404 not found 404 not found oaj materials and devices – new article type : « methods » http://materialsanddevices.co-ac.com the oaj materials and devices’s international editorial committee is happy to announce that a new article type is launched! perhaps did you write an article on a physical object that you prepared or synthesized, and you felt frustrated because you could describe the preparation method only in few lines ? or you used a computing method in a simulation study and you couldn’t describe in details the method you developed during months or even years ? such examples are frequent, it is why we introduce a new type of articles in the journal materials and devices : « methods » this type of article concerns all kinds of methods, whether theoretical, computational, experimental, or sample preparation methods, whether in the form of crystals, nanomaterials, thin or thick films, multilayers, etc. these articles can be submitted before or after the publication of other articles (*) that use the method described. the expected structure of these articles is a brief justification of the work, followed by the detailed presentation of the method presented, as well as a short description of typical results obtained by the method in question. and as usually, publications are free of charges for authors ! submissions may be as a free style manuscript you will be expected to prepare the final manuscript according to the template only when it is accepted ! you have methods to present in details ? prepare the text, register as author, and submit it in the site of the journal (click here) ! please register all authors ! the template will be available soon. thank you ! (*) if you prepare the « method » article after the article(s) that used the method to describe in detail, please respect copyrights ! http://materialsanddevices.co-ac.com/ http://caip.co-ac.com/index.php/materialsanddevices/user/register this document is part of a new book, it is brought to you freely by the open access journal materials and devices the book, “perovskites and other framework structure materials (2d-perovskites, aurivillius, ruddlesden-popper, dionjacobson phases, tungsten bronzes, clays, and others) new trends and perspectives” (editors p. saint-grégoire and m.b smirnov) is a collective volume of 800 pages with 76 authors and 26 chapters on recent developments and hot subjects, divided into two parts: a. fundamental aspects and general properties b. elaborated materials and applied properties available in 3 formats: ● ebook ● printed softcover, black & white ● printed hardcover, color. non-contractual view publication date: 2021, january 14th go to the book(click) http://perovskitesandotherfws.co-ac.com/ http://materialsanddevices.co-ac.com/ chap.20 : a review of the synthesis of single-crystal 1d perovskite nanostructures by the hydrothermal method o.kovalenko (1,2), a. ragulya (1,2) (1) department of physics, chemistry and technology of nanotextured ceramics and nanocomposite materials, frantsevich institute for problems of materials science nasu, ukraine (2) llc nanotechcenter, ukraine corresponding author : olgiuskovalenko@gmail.com abstract : recently, anisotropic, particularly, one-dimensional (1d) ferroelectric perovskite nanostructures have been of high interest due to a number of unique properties. despite the existing works about the synthesis of such 1d nanostructures, there remain issues of fine-tuning the particle morphology due to the complex mechanism of particle formation. therefore, in this paper, an attempt was made to describe the influence of the crystallization mechanism as well as hydrothermal synthesis parameters (such as reagent nature, ph, concentration, surfactant, heat treatment mode) on the peculiarities of the anisotropic growth and the formation of the 1d perovskite nanostructures. keywords : perovskite, nanostructure, anisotropy, crystallization cite this paper: o.kovalenko, a. ragulya, chap no20 in “perovskites and other framework structure crystalline materials”, p 571 (coll. acad. 2021) – doi:10.23647/ca.md20200307 * perovskites and other framework structure crystalline materials * p 571 mailto:olgiuskovalenko@gmail.com o.kovalenko, a. ragulya i. introduction the perovskite-type compound with the general formula of abo3 (fig.1) is the most studied ferroelectric oxides due to the unique dielectric and ferroelectric properties1,2. compositions based on the batio3, srtio3, pbtio3 and pbzro3 form solid solutions with each other and with a large number of other oxides and provide an enormous va riety of ferroelectric properties3. particularly, batio3 and pb(zr,ti)o3 are widely used for its high dielectric and piezoelectric coefficients, respectively4,5. it makes this material widely used in non-volatile digital memories, thin-film capacitors, electronic transducers, actuators, high-k dielectrics* as well as pyroelectric sensors, electrooptic modulators, optical memories and nonlinear optics6. figure 1: perovskite structure. i) a-site (dodecahedral coordination) with (ba,ca,na, k, sr, pb) cations; ii) b-site (octahedral coordination) with (ti,zr, nb,ta) cations; iii) bo6 oxygen octahedral recently, increasing attention is paid to the one-dimensional (1d) ferroelectric nanostructures including nanowires, nanorods, and nanotubes due to the excellent performance in nanoelectronic, photoelectronic, and data storage devices7,8,9,1011,12,13. recently, the 1d perovskite nanostructures have attracted attention in such application as nano-sensors and catalysts for the integration in the current electronic devices10,14,15, biological materials (mimicking of the ion channels, drug delivery systems, stem cells investigation), photodetectors, solar cells, building blocks for laser applications, etc8,16,17. *material with a high dielectric constant (k) as compared to silicon dioxide * perovskites and other framework structure crystalline materials * p 572 page 1 chap.20 : a review of the synthesis of single-crystal 1d perovskite nanostructures by the hydrothermal method i. introduction rev name of authors (eventually completed by “et al”) and abbreviated title – should not exceed one line article type: a-regular research paper ; l-short paper; r-review article ; conf.-conference paper (acronym of the event); t-technical paper ; ur-unexpected results (delete irrelevant items) title of the article eventual subtitle m. alfron (1), a. dupond (2), o. popov (3), t. shiaoshi (4) (1) laboratory name, university, country, e-mail address (2) laboratory name, university, country, e-mail address (3) laboratory name, university, country, e-mail address (4) laboratory name, university, country, e-mail address corresponding author : e-mail hyperlink "mailto:e-mail@address" @ hyperlink "mailto:e-mail@address" address received: 12 november 2016 / received in final form: 25 december 2016 / accepted: 04 january 2017 abstract : the abstract will be written in fontsize 8. it should represent the content of the paper and should not exceed 10 lines. please do not use abbreviations in the abstract. keywords : list at least 5 keywords in english separated by comas, use fontsize 8 and capital letters, for instance ecomaterials, semiconductors, nanomaterials, oxides, etc introduction new! we are aware of the time losses due to preparation of manuscripts in different formats to fulfill requirements of different journals. for this reason, in order to save your time, we decided to accept submissions of new articles in any form: when submitting your article, you may now submit a file edited freely, without following any template. we only ask you to number lines, formula, figures and tables. thereafter submit a pdf generated from your manuscript. we shall ask you to prepare the final version of your manuscript at final stage, when and if your article is accepted following recommendations of reviewers. if you choose to edit your article as an .odt document, please use this template with care. please note that for review articles the template is different! do not change the format (use fontsize 8), and proceed by replacing the text in the present document by your own text. if necessary, you can introduce new paragraphs generated from the present model of paragraph, but without changing the format. it is recommended to use the last stable official version of libre office, that you can download at www.libreoffice.org/. a manual for using libre office or open office to edit a scientific article containing formula can be found here : https://wiki.documentfoundation.org/images/3/37/mg40-mathguide.pdf for each part you copy or edit in the present document, check that the result is in agreement with the present model, and that the format has not been accidentally changed in the meantime. second paragraph copy this paragraph as many times as you need. if you need to introduce equations, use the libre office facilities available in the software. equations need to be numbered. the number will be indicated as follows, for instance (1), located on the right side; use preferentially the function integrated in libre office named “autotext” accessible through menu > edition or through a shortcut dependent of the language version of libre office, often fn+f3 or ctrl+f3 (see for more details : https://wiki.openoffice.org/wiki/documentation/ooo3_user_g hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" uides/writer_guide/numbering_ hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" e hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" quations (1) . an advantage of automatic numbering of equations is that you can cite equations in the text using crossreference, which modifies automatically the numbering if you introduce changes, for instance if you delete an equation. (1) equations should be centered in the paragraph. in the text refer to equations as eq. (1), (2), ... please do not forget to introduce the signification of abbreviations the first time they are introduced. concerning references, they should appear in the text as a number between brackets, in the order of appearance, and as superscript in the text for instance as [3]. all references will be located at the end of the document, in the space left for it. please follow the format for references therein. beware to use the standard abbreviation of cited journals according to the issn list of title abbreviation (see http://www.issn.org/2-22661-ltwa-online.php). in the references, if the doi (digital object identification) of cited articles is available, it is better (but not mandatory) to mention it. figures should be also centered in the text. in principle, they should occupy no more that one column, but in particular cases where it should be larger, a figure could occupy the whole width of the page. take care that the figure and the caption should be displayed in the same column. figures should have a caption as follows : figure 1: title of the figure – bold, fontsize 9 comments (fontsize 7), indicate clearly which quantities are along vertical and horizontal axes; check that the figure may be read easily, labels of axes, in particular, should be present and large enough to be read without problem. take care also of the size of the pictures : avoid pictures with a size exceeding 500 ko. finally check that the figure caption appears entirely below the figure.(here is an example of what should not be done !) tables will be centered, and numbered according to the order of their appearance in the text. tables should not be cut into several pieces, either between different pages, or between different columns. prefer tables occupying one column, but if necessary a table can occupy the whole width of the page.table title and caption will be above the table itself as follows : table 1 : title of the table (centered) third paragraph copy the model of paragraph given by “second paragraph” as many times as you need. last paragraph should concern conclusion. in this template, we now take opportunity to say some words about open access and the philosophy of this journal. according to the “budapest open access initiative” (see http://www.budapestopenaccessinitiative.org/): “in response to the growing demand to make research free and available to anyone with a computer and an internet connection, a diverse coalition has issued new guidelines that could usher in huge advances in the sciences, medicine, and health. the recommendations were developed by leaders of the open access movement, which has worked for the past decade to provide the public with unrestricted, free access to scholarly research—much of which is publicly funded. making the research publicly available to everyone—free of charge and without most copyright and licensing restrictions—will accelerate scientific research efforts and allow authors to reach a larger number of readers. the recommendations are the result of a meeting organized by the open society foundations to mark the tenth anniversary of budapest open access initiative, which first defined open access. the recommendations include the development of open access policies in institutions of higher education and in funding agencies, the open licensing of scholarly works, the development of infrastructure such as open access repositories and creating standards of professional conduct for open access publishing. the recommendations also establish a new goal of achieving open access as the default method for distributing new peer-reviewed research in every field and in every country within ten years’ time.” generally, open access journals (or open access option in traditional journals) are not free of charge for authors: the fees vary between approximately 100 € and 9000 € per article. traditional journals propose now frequently an open access option, that makes your article openly accessible, but this is not a free service. however in both cases, open access and traditional editing, reviewers do their work without any charge for the journal. materials and devices is edited by the scientific association collaborating academics, and the bet we make, which is a challenge, is that because of volunteerism, the journal is and will remain free of charge for authors. as a result, you don't need to pay for publishing your article in materials and devices, and you may use and distribute freely copies of your paper, and, what is important, you remain owner of the article content. however beware that if you do not respect this template, which would induce additional work for us, you will be charged by an inclusive fee of 100€ if your paper is accepted and if you do not submit a final version according to this template. there is an interesting site, in which you can check publisher copyright policies and self-archiving, called sherpa/romeo. you should absolutely consult it before distributing your articles through internet if it is published in a traditional journal (it may be forbidden by some editor to distribute or self-archive your work): http://www.sherpa.ac.uk/romeo/index.php you can use your article without limitation if it is published in materials and devices. your submission of articles and your involvement in the journal or in collaborating academics are welcome! conclusion this paragraph should resume as clearly as possible the results you obtained, underlying the most important points and probable, eventual future prolongations of the work. acknowledgements: please locate eventual acknowledgements here following this format. references 1. r.firstname, h.secondname, o.etc, journal of experimental science, vol.4, p 18 (2014) 2. r.firstname, h.secondname, o.etc, title-of-the-paper, in title-of-the-book, editor, place (year) 3. etc you can also use for references the automatic numbering provided by the text editor. important: please prepare a list of e-mail addresses of scientists working in the field of this article, or in related fields (at least 15 addresses) (requested by the journal, will not appear in the published article) and send that list together with the manuscript by e-mail to editor.materialsanddevices@gmail.com adresses should be separated by coma, as name1@univ1.net, name2@univ2.com, … thereafter remove this part underlined in yellow from your manuscript! important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article permissions – important: all materials in this article may be freely reused (figures, tables, …) without any need to ask permission or to pay any fee. it is simply asked to refer to the article. materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! put your article as soon as possible on your personal sites, institutional sites, etc! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has been designed so that it can be accepted by doaj, and we are happy to inform you that this is the case now. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers, and o: opinion papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) important: all submitted articles, fullfilling above indications, are evaluated by peers from a pure scientific point of view! the editor-in-chief does not take any right of censorship, whether on the basis of the subject of the article, or the strength of the “profile of the authors”, their reputation, or other. we do not take any action to mechanically optimize the impact factor of the journal, for example by analyzing the forecast number of citations of the article based on the number of scientists working in the field, or fashion effects, or other. we want to maintain materials and devices open access and free of charge thanks to volunteeriing, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com cite this article: authors, oaj materials and devices, vol 4 #1, xxxx (2019) – doi: 10.23647/ca.md2017xxxxx oaj materials and devices, vol 5#1, 0504 (2020) – doi: 10.23647/ca.md20180504 _2147483647.unknown rev name of authors (eventually completed by “et al”) and abbreviated title – should not exceed one line article type: rinvited review article (event abbreviation if adequate) title of the review article eventual subtitle m. alfron (1), a. dupond (2), o. popov (3), t. shiaoshi (4)(1) laboratory name, university, country, e-mail address (2) laboratory name, university, country, e-mail address (3) laboratory name, university, country, e-mail address (4) laboratory name, university, country, e-mail address corresponding author : e-mail hyperlink "mailto:e-mail@address" @ hyperlink "mailto:e-mail@address" address received: 12 november 2016 / received in final form: 25 december 2016 / accepted: 04 january 2017 abstract : the abstract will be written in fontsize 8. it should represent the content of the paper and should not exceed 10 lines. please do not use abbreviations in the abstract. keywords : list till 5 keywords in english separated by comas, use fontsize 8 and capital letters, for instance ecomaterials, semiconductors, nanomaterials, oxides, etc i. introduction new! we are aware of the time losses due to preparation of manuscripts in different formats to fulfill requirements of different journals. for this reason, in order to save your time, we decided to accept submissions of new articles in any form: when submitting your article, you may now submit a file edited freely, without following any template. we only ask you to number lines, formula, figures and tables. thereafter submit a pdf generated from your manuscript. we shall ask you to prepare the final version of your manuscript at final stage, when and if your article is accepted following recommendations of reviewers. please use this template for review articles only (see the other template that is required for other article types, see the site of the journal). do not change the format (use fontsize 10), and proceed by replacing the text in the present document by your own text. if necessary, you can introduce new paragraphs generated from the present model of paragraph, but without changing the format. save the document as a .doc file or a .odt file. please avoid .docx format! it is recommended to use the last stable official version of libre office, that you can download at www.libreoffice.org/. it allows a very good recognition of a document by different versions of the software using various platforms (windows, mac, linux). a manual for using libre office or open office to edit a scientific article containing formula can be found here : https://wiki.documentfoundation.org/images/3/37/mg40-mathguide.pdf for each part you copy or edit in the present document, check that the result is in agreement with the present model, and that the format has not been accidentally changed in the meantime. ii. second paragraph copy this paragraph as many times as you need. ii.1. second paragraph – first subparagraph (reduce the size to 14) if you need to introduce equations, use the libre office facilities available in the software. ii.1.a. second paragraph – first subparagraph first sub-subparagraph (reduce the size to 12) equations need to be numbered. the number will be indicated as follows, for instance (1), located on the right side; use preferentially the function integrated in libre office named “autotext” accessible through menu > edition or through a shortcut dependent of the language version of libre office, often fn+f3 or ctrl+f3 (see for more details : https://wiki.openoffice.org/wiki/documentation/ooo3_user_g hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" uides/writer_guide/numbering_ hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" e hyperlink "https://wiki.openoffice.org/wiki/documentation/ooo3_user_guides/writer_guide/numbering_equations" quations (1) . an advantage of automatic numbering of equations is that you can cite equations in the text using crossreference, which modifies automatically the numbering if you introduce changes, for instance if you delete an equation. (1) equations should be centered in the paragraph. in the text refer to equations as eq. (1), (2), … footnotes should be introduced using the integrated function in word or in libre office writer please do not forget to introduce the signification of abbreviations the first time they are introduced. concerning references, they should appear in the text as a number between brackets, in the order of appearance, and as superscript in the text for instance as [3]. all references will be located at the end of the document, in the space left for it. please follow the format for references therein. beware to use the standard abbreviation of cited journals according to the issn list of title abbreviation (see http://www.issn.org/2-22661-ltwa-online.php). in the references, if the doi (digital object identification) of cited articles is available, it is better (but not mandatory) to mention it. figures should be also centered in the text. take care that the figure and the caption should be displayed in the same page. figures should have a caption as follows : figure 1: title of the figure – bold, fontsize 10 comments (fontsize 9), indicate clearly which quantities are along vertical and horizontal axes; check that the figure may be viewed easily, labels of axes, in particular, should be present and large enough to be read without problem (here is an example of what should not be done !). take care also of the size of the pictures : avoid pictures with a size exceeding 500 ko. finally check that the figure caption appears entirely below the figure. tables will be centered, and numbered according to the order of their appearance in the text. tables should not be cut into several pieces, between different pages. table title and caption will be above the table itself as follows : table 1 : title of the table (centered) iii. third paragraph copy the model of paragraph given by “second paragraph” as many times as you need. last paragraph should concern conclusion. in this template, we now take opportunity to say some words about open access and the philosophy of this journal. according to the “budapest open access initiative” (see http://www.budapestopenaccessinitiative.org/): “in response to the growing demand to make research free and available to anyone with a computer and an internet connection, a diverse coalition has issued new guidelines that could usher in huge advances in the sciences, medicine, and health. the recommendations were developed by leaders of the open access movement, which has worked for the past decade to provide the public with unrestricted, free access to scholarly research—much of which is publicly funded. making the research publicly available to everyone—free of charge and without most copyright and licensing restrictions—will accelerate scientific research efforts and allow authors to reach a larger number of readers. the recommendations are the result of a meeting organized by the open society foundations to mark the tenth anniversary of budapest open access initiative, which first defined open access. the recommendations include the development of open access policies in institutions of higher education and in funding agencies, the open licensing of scholarly works, the development of infrastructure such as open access repositories and creating standards of professional conduct for open access publishing. the recommendations also establish a new goal of achieving open access as the default method for distributing new peer-reviewed research in every field and in every country within ten years’ time.” generally, open access journals (or open access option in traditional journals) are not free of charge for authors: the fees vary between approximately 100 € and 9000 € per article. traditional journals propose now frequently an open access option, that makes your article openly accessible, but this is not a free service. however in both cases, open access and traditional editing, reviewers do their work without any charge for the journal. materials and devices is edited by the scientific association collaborating academics, and the bet we make, which is a challenge, is that because of volunteerism, the journal is and will remain free of charge for authors. as a result, you don't need to pay for publishing your article in materials and devices, and you may use and distribute freely copies of your paper, and, what is important, you remain owner of the article content. however beware that if you do not respect this template, which would induce additional work for us, you will be charged by an inclusive fee of 100€ if your paper is accepted and if you do not submit a final version according to this template. there is an interesting site, in which you can check publisher copyright policies and self-archiving, called sherpa/romeo. you should absolutely consult it before distributing your articles through internet if it is published in a traditional journal (it may be forbidden by some editor to distribute or self-archive your work): http://www.sherpa.ac.uk/romeo/index.php you can use your article without limitation if it is published in materials and devices. your submission of articles and your involvement in the journal or in collaborating academics are welcome! iv. conclusion this paragraph should resume as clearly as possible the results you obtained, underlying the most important points and probable, eventual future prolongations of the work. acknowledgements: please locate eventual acknowledgements here following this format. references 1. r.firstname, h.secondname, o.etc, journal of experimental science, vol.4, p 18 (2014) 2. r.firstname, h.secondname, o.etc, title-of-the-paper, in title-of-the-book, editor, place (year) 3. etc you can also use for references the automatic numbering provided by the text editor. important: please prepare a list of e-mail addresses of scientists working in the field of this article, or in related fields (at least 15 addresses) (requested by the journal, will not appear in the published article) and send that list together with the manuscript by e-mail to editor.materialsanddevices@gmail.com adresses should be separated by coma, as name1@univ1.net, name2@univ2.com, … thereafter remove this part underlined in yellow from your manuscript! important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article permissions – important: all materials in this article may be freely reused (figures, tables, …) without any need to ask permission or to pay any fee. it is simply asked to refer to the article. materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! put your article as soon as possible on your personal sites, institutional sites, etc! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has been designed so that it can be accepted by doaj, and we are happy to inform you that this is the case now. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers, and o: opinion papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) important: all submitted articles, fullfilling above indications, are evaluated by peers from a pure scientific point of view! the editor-in-chief does not take any right of censorship, whether on the basis of the subject of the article, or the strength of the “profile of the authors”, their reputation, or other. we do not take any action to mechanically optimize the impact factor of the journal, for example by analyzing the forecast number of citations of the article based on the number of scientists working in the field, or fashion effects, or other. we want to maintain materials and devices open access and free of charge thanks to volunteeriing, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com cite this article: authors, oaj materials and devices, vol 4 #1, xxxx (2019) – doi: 10.23647/ca.md2017xxxxx � in this way footnotes are numbered by the text processor. the space reserved for the footnotes is automatically reserved by the software... oaj materials and devices, vol 4 #1, xxxx (2019) – doi: 10.23647/ca.md2017xxxxx p6 _2147483647.unknown rev s. abou garham et al., lead-free bnt piezoelectric thin films by sol-gel method conference article (international symposium on physics of data storage-1) lead-free bnt piezoelectric thin films by sol-gel method s. abou dargham (1, 2), f. ponchel (1), m. soueidan (3), a. khoury (2), j. assaad (1), d. remiens (1), d. zaouk (2) (1) iemn – doae, mimm team, university of valenciennes, france (2) applied physics laboratory, lebanese university, lebanon (3) lebanese atomic energy commission – cnrs, riad l solh, lebanon corresponding author: sara.aboudargham@etu.univ-valenciennes.fr received: 21 september 2016 / received in final form: 24 november 2016 / accepted: 30 november 2016 abstract: the objective of this work is to synthesize lead-free piezoelectric thin films by the sol-gel method: bismuth sodium titanate (bi0.5na0.5tio3 or bnt). bnt films were annealed with the rapid thermal process (rtp). the film treated at 700°c is dense and well crystallized in the perovskite phase. the first results of electrical characterizations showed promising dielectric, ferroelectric and piezoelectric performance. at 12 khz, the dielectric constant and losses are 430 and 0.07, respectively. ferroelectric hysteresis measurements indicated a remanent polarization of 10μc/cm2, associated with a coercive field of 70 kv/cm. the piezoelectric properties of bnt films were studied with a laser doppler interferometer: a piezoelectric coefficient (d33effmax) of 42 pm/v was measured. keywords: piezoelectric, lead-free, sol-gel, thin films, bnt. introduction lead zirconate titanate (pb(zr,ti)o3 or pzt) are widely used in the microelectronics industry due to their ferroelectric and piezoelectric properties [1]. however, the rohs directive made by the european union took effect on july 2006. this directive restricts the use of 6 hazardous substances (pb, hg, cd...) in electronic and electrical equipment [2]. therefore, lead-free piezoelectric materials have been attracting attention as new materials in place of pzt [3]. bismuth sodium titanate (bi0.5na0.5tio3 or bnt) is a promising lead-free piezoelectric material. bnt ceramics have strong ferroelectric properties (remnant polarization pr=38 µc/cm2, curie temperature tc= 320°c and coercive field ec= 73 kv/cm) and relatively high piezoelectric properties (d33=60-90 pm/v) [4]. bnt is a promising material for different applications (based on piezoelectric properties, pyroelectric and electrocaloric effects, etc.). in the present work, structural and electrical proprieties of bnt thin films prepared by the sol-gel method were studied. materials and devices, vol 1(1), 1217 (2016) – doi: 10.23647/ca.md20161217 s. abou garham et al., lead-free bnt piezoelectric thin films by sol-gel method experimental details the objective of this work is to synthesize a lead-free piezoelectric material by the sol-gel method: the bismuth sodium titanate (bnt). bismuth nitrate iii penta-hydrate [bi(no3)3.5h2o], sodium nitrate [nano3] and titanium (iv) isopropoxide [ti(och(ch3)2)4] were used to prepare the solution of bnt. nitrates were dissolved in acetic acid and water at 70°c. then the mixture was introduced to a prepared solution of titanium isopropoxide in acetylacetone. after stirring at room temperature, a stable yellow sol precursor of bnt was obtained. the solution was deposited by spin coating (at a speed of 3000 rpm for 20 s) on a pt/ti/sio2/si substrate. then thermal processes (drying, pyrolysis and annealing) were applied; bnt films were annealed with the rapid thermal processor (rtp) after each layer deposition in order to reduce thermal stresses. lno top electrodes were deposited on the films by magnetron sputtering and patterned by a photolithography liftoff process for the subsequent measurements. x-ray diffraction (xrd, siemens d5000, germany) and scanning electron microscope (sem, zeiss ultra 55) analyses were used to examine the crystalline structure and surface morphology of bnt films. dielectric properties of bnt films were studied using an impedance analyzer (hp 4192a). for the polarization hysteresis (p-e) loops, we have used an aixacct tf 2000 analyzer to study the ferroelectric properties at the macroscopic scale of bnt films. results and discussions figure 1 shows the xrd patterns of the bnt films annealed at different temperature by the rtp. at 700°c, the bnt thin film is completely crystallized in the rhombohedral perovskite phase of bi0.5na0.5tio3. figure 1: xrd patterns of bnt thin films. scanning electron microscopy (sem) micrographs of bnt thin films annealed at 700°c and 750°c are shown in figure 2. bnt films annealed at 700°c present dense and uniform grains. however, in increasing the annealing temperature (750°c) cracks and pores were produced. as it can be seen from the cross-sectional micrographs, the film annealed at 700°c has a uniform thickness (about 350 nm). this film exhibits a relatively dense grained structure. figure 2: sem micrographs of bnt thin films. figure 3 shows the dielectric permittivity and dielectric loss as a function of the applied electrical field for the bnt film annealed at 700°c measured at room temperature at 12 khz. dielectric constant and loss tangent loops appear approximately symmetric, with a typical hysteresis behavior for ferroelectric capacitors. the maximum dielectric permittivity and loss factor were about 430 and 0.07, respectively. figure 3: electrical field dependences of (a) the permittivity and (b) the dielectric losses for the bnt thin film. figure 4 shows hysteresis loops of a 350 nm-thick bnt film at room temperature. remanent polarizations (pr) of 10μc/cm2, associated with a coercive field (ec) of 70 kv/cm, were measured for an applied electric field of 350 kv/cm. increasing the applied electric field (from 12v to 16v) leads to non-symmetric loop due to the leakage currents and to the non-symmetry of the top and bottom electrodes (lno – pt) [5]. the piezoelectric coefficient was measured using a modified laser doppler vibrometer. the measurement method as proposed in a previous paper is used [6]. the d33eff loop of a 350 nm thick bnt film is represented in figure 5. the maximum materials and devices, vol 1(1), 1217 (2016) – doi: 10.23647/ca.md20161217 s. abou garham et al., lead-free bnt piezoelectric thin films by sol-gel method value of d33 piezoelectric coefficient measured at 270 kv/cm is 42 pm/v. figure 4: room temperature macroscopic ferroelectric hysteresis (p-e) loops measured for a bnt film, for an applied voltage of 12 and 16v. conclusion polycrystalline piezoelectric lead-free thin films (bnt) were deposited on pt/tio2/sio2/si substrates by an optimized sol-gel/spin-coating process. the structural and morphological analyses showed that the films annealed at 700°c with the rapid thermal processor (rtp) is dense and well crystallized in the perovskite phase. the values of the permittivity and the losses are 430 and 7%, respectively. the remanent polarization and coercive field values of bnt thin films are 10 μc/cm2 and 70 kv/cm when the maximum applied electric field is 350 kv/cm. first results of piezoelectric characterizations at the macroscopic level showed promising piezoelectric response (d33=42 pm/v). figure 5: d33eff (e) loop of bnt film. acknowledgements: the authors acknowledge the financial support provided by the lebanese national council for scientific research (cnrs-l). references 1. t. yamamoto, japanese journal of applied physics, vol 35, p 5104 (1996) 2. official journal of the european union, vol 46, p 19 (2003) 3. t. takenaka, h. nagata, y. hiruma, japanese journal of applied physics, vol 47, p 3787 (2008) 4. a. herabut, a. safari, journal of the american ceramic society, vol 80, p 2954 (1997) 5. z zhou, j xue, w li, j wang, h zhu, j miao, applied physics letter, vol.85, p 804 (2004) 6. r. herdier, d. jenkins, e. dogheche, d. remiens, m. sulc, review of scientific instruments, vol. 77, (2006) materials and devices, vol 1(1), 1217 (2016) – doi: 10.23647/ca.md20161217 introduction experimental details results and discussions conclusion s.ghyati, m.benhamou, m.el-jai, i.akhrif., polymer nanocomposites from natural clay oaj materials and devices, vol 3 #1, 1103 (2018) – doi: 10.23647/ca.md20181103 article type: a-regular research paper polymer nanocomposites from natural clay: understanding clay-peg interaction and their effect on spacing between clay-plates s. ghyati (1), m. benhamou (2), m. el-jai (3), i. akhrif (4) (1) ensam, moulay ismail university, p.o. box 15290, al mansour, meknes, morocco, ghyatisouad@gmail.com (2) physics department, faculty of sciences p.o. box 11201, moulay ismail university, meknes, morocco, benhamou.mabrouk@gmail.com (3) euromed university, fez, morocco, mostaphaeljai@gmail.com (4) geoscience and environment laboratory, sidi mohamed ben abdellah university, fez, morocco, akhrif@upf.ac.ma corresponding author : ghyatisouad@gmail.com received: 15 january 2018 / received in final form: 11 march 2018 / accepted: 11 march 2018 abstract : the interactions between clay-plates and hydrophilic polymer are investigated assuming that the polyethylene glycol chains are grafted onto face-to-face clay-plates. besides the usual van der waals attractive interaction, the clay-plates experience a repulsive effective interaction, due to the excluded volume force between monomers along the grafted peg chains. the face-to-face clayplates then play the role of polymer brushes. the free energy (per unit area) of a clay-plate pair is the sum of these interactions, and from its expression, we determine the minimal inter-sheet distance, after intercalation, which corresponds to a critical percentage of peg. finally, our results are found to be in good agreement with some recent experimental work. keywords : nanocomposites, clay, polyethylene glycol, interactions. introduction properties emerging from nanocomposites based on clay have been extensively studied and explored as powerful tools in a series of applications, such as adsorbents of organic pollutants in soil, water and air, rheological control agents, paints, medicine [1-4]. owing to hydrophilic nature of clay, the intercalation by water-soluble polymers is expected to be relatively simple. however, early attempts to intercalate pval, p4vp or peg between face-to-face clayplates were not successful, as shown by xrd experiment [5]. in fact, that is due to many factors, as the solvent quality and the elaboration methods. the main role of the polymer intercalation is to expand the interlayer-spacing and to reduce the effective interaction between the clay-platelets. the first goal has been achieved by making use of the anionic charge within the interlamellar galleries. since the van der waals interactions between solid surfaces decrease with the square of the separation-distance, the insertion of the organic or inorganic molecules into the interlamellar space greatly helps to achieve the second aim [67]. the used poly(ethylene oxide) (peo) is a nonionic and watersoluble polymer with many applications, due to its flocculent, thickening, lubrication, dispersing, and water-retention properties [8]. recently, peo/clay nanocomposites are mailto:ghyatisouad@gmail.com s.ghyati, m.benhamou, m.el-jai, i.akhrif., polymer nanocomposites from natural clay oaj materials and devices, vol 3 #1, 1103 (2018) – doi: 10.23647/ca.md20181103 promising materials and showing a great potential for various applications. peo and its low-molecular-weight peg can intercalate between clay-plates giving rise to a limited increase of the basal spacing (about 0.8 nm) [9]. many studies have further more focused on the structure and the conformation of the peo chains in the confined space of clays [10]-[11]. the purpose of this work is to contribute to the understanding of how hydrophilic peg6000 chains interact with clay-plates and to obtain further information regarding the interplate separation profile, as a function of the polymer-density. for this we assume that the peg chains are grafted onto face-to-face clay-plates. this paper is organized as follows. in the next section, we summarize our theoretical framework about the face-to-face effective interactions. a comparison between the theory and some experimentis given in the third section. finally, some concluding remarks are drawn in the last section. theoretical framework consider a given clay-plate pair confining end-grafted polymer chains (figure 1). each consists of 𝑁 monomers of common size, 𝑏. in addition, we assume that the confined host medium is a good solvent figure 1: two interacting layers of grafted peg chains. to describe physics, we need the expression of the free energy (per unit area), 𝐹𝑡𝑜𝑡. in fact, the latter is the sum of two contributions 𝐹𝑡𝑜𝑡 = 𝐹𝑣𝑑𝑤 + 𝐹𝑝 . (1) the first term accounts for the contribution of the van der waals forces between the adjacent clay-plates [12], 𝐹𝑣𝑑𝑤 = − 𝐴𝐻 12𝜋𝑑2 , (2) where 𝑑 is the separation between the considered clayplates and 𝐴𝐻 is the hamaker constant. the second term in equality (1) is that of the steric forces [13], 𝐹𝑝 = 𝛼𝑘𝐵 𝑇𝑏 3𝑁 2γ2 ( 1 𝑑 ) . (3) here α is a numerical coefficient of the order of unity, γ = 1 s2⁄ is the surface coverage (number of grafted polymer chains per unit area), where s is the mean-distance between the grafted chains, and γ∗ = rg −2 denotes some threshold that indicates the passage from the mushroom to brush regimes, with the gyration-radius of a single swollen polymer chain, rg~bn 3 5⁄ . there, 𝑇 is the absolute temperatura and 𝑘𝐵 is the boltmann’s constant. in this work, we are interested rather in the brushregime, with γ > γ∗. the mushroom regime corresponds to the condition γ < γ∗. then, there is a competition between the attractive interaction that exists even in the absence of the polymer and the repulsive one that results from the excluded volume forces. notice that the surface coverage is simply proportional to the volume fraction of the intercalated polymer between the claysheets. it is then natural to consider the phase-diagram in (γ, 𝑑)-plane. now, equating the first derivative of the total free energy (1), with respect to the inter-sheet distance, 𝑑, at fixed surface coverage, gives the equilibrium relationship 𝑑 𝑏 = 𝐴𝐻 6𝜋𝛼𝑁 2𝑘𝐵 𝑇 × 1 (γ𝑏2)2 (4) then the equilibrium distance decreases as the inverse of the squared surface coverage. indeed, as the polymerconcentration is increased, the excluded volume force between monomers belonging to the grafted polymer chains is screened out. in figure 2, we report the renormalized inter-sheet distance 𝑑 𝑏⁄ , upon the dimensionless surface coverage, γ𝑏2. 0,0 0,2 0,4 0,6 0,8 1,0 0 5 10 15 20 in te r d is ta n c e surface coverage figure 2: renormalized inter-sheet distance, 𝐝 𝐛⁄ , upon the dimensionless surface coverage, γ𝐛 𝟐 . comparison between experiment and theory in this section, we compare the predictions of the theoretical model described above with some recent measurements of the interplate separation-values, 𝑑001, obtained from five samples using xrd analysis [14]. these results have been investigated by experiments on a three-component clay-polymer-water system. at fixed amount of clay (𝑚 = 6𝑔), figure 3 shows the plot of 𝑑001-values for kaolinite, as a function of peg6000 percentage. s.ghyati, m.benhamou, m.el-jai, i.akhrif., polymer nanocomposites from natural clay oaj materials and devices, vol 3 #1, 1103 (2018) – doi: 10.23647/ca.md20181103 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,700 0,705 0,710 0,715 0,720 0,725 d 0 0 1 ( n m ) % peg 6000 figure 3: interplate separation as a function of peg6000 percentage. as shown in this figure, there is a remarkable agreement between the experimental results and the theoretical predictions (figure 2). in fact, the inter-sheet distance decreases with the polymer-density, because of the screening effect caused by the peg brushes leading to a significant decrease in the layer thickness, and therefore, strengthening the van der waals attraction. conclusion in this paper, we present a comparative analysis between recent experimental results giving the evolution of the intersheet distance, as a function of the peg6000 percentage, and some theoretical model we recently developed. the latter is based on a balance between a van der waals attractive interaction which tends to bring the clay-plates close to each other and a repulsive energy induced by the end-adsorbed chains. the main outcome of this study confirmed the decrease of the separation between clay-platelets with the polymer-density and to understand how small densities of peg6000 chains interact with the clay-plates. references 1. s.ray, m.oakamoto, polymer/layered silicate nanocomposites: a review from preparation to processing, journal of progress in polymer science, vol.28, p 1539-1641 (2003) 2. p.c.lebaron, z.wang, t.j.pinnavaia, polymer-layered silicate nanocomposites: an overview, journal of applied clay science, vol.15, p 11-29 (1999) 3. c.aguzzi et al., use of clays as drug delivery systems: possibilities and limitations, journal of applied clay science, vol.36, p 22-36 (2007) 4. h.a.patel et al., nanoclays for polymer nanocomposites, paints, inks, greases and cosmetics formulations, drug delivery vehicle and waste water treatment, journal of bulletin of materials science, vol.29, p 133-145 (2006) 5. l.a.utracki, clay-containing polymeric nanocomposites, smithers rapra publishing, crewe (2004) 6. d.klempner, l.h.sperling, l.a.utracki, interpenetrating polymer networks, american chemical society, new york (1994) 7. a.ajji, l.a.utracki, compatibilisation of polymer blends, journal of progress in rubber and plastics technology, vol.13, p 153-188 (1997) 8. p.aranda, e.ruiz-hitzky, poly (ethylene oxide)-silicate intercalation materials, journal of chemistry of materials, vol.4, p 1395-1403 (1992) 9. p.aranda, e.ruiz-hitzky, poly (ethylene oxide)/nh4 + -smectite nanocomposites, journal of applied clay science, vol.15, p 119-135 (1999) 10. j.wu, m.m.lerner, structural, thermal, and electrical characterization of layered nanocomposites derived from sodiummontmorillonite and polyethers, journal of chemistry of materials, vol.5, p 835-838 (1993) 11. s.zhu, j.chen, h.li et al., structure and conformation of poly (ethylene glycol) in confined space of montmorillonite, journal of applied surface science, vol.264, p 500-506 (2013) 12. j.n.israelachvili, intermolecular and surface forces, academic press, san diego (2011) 13. s.t.milner, t.a.witten, m.e.cates, theory of the grafted polymer brush, macromolecules, vol.21, p 2610-2619 (1988) 14. i.akhrif, l.mesrar, m.el jai, m.benhamou, r.jabrane, elaboration and x-ray diffraction techniques,characterization of clay-peg 6000 nanocomposites with clay matrix, journal of multidisciplinary and current research, vol.3, p 564-571 (2015) s.ghyati, m.benhamou, m.el-jai, i.akhrif., polymer nanocomposites from natural clay oaj materials and devices, vol 3 #1, 1103 (2018) – doi: 10.23647/ca.md20181103 important: articles are published under the responsability of authors, in particular concerning the 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(see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev a.bendjerad et al, modeling of magnetic properties (cr/nio/ni) based multi-layers deposited by magnetron sputtering using… l-short paper modeling of magnetic properties (cr/nio/ni) based multi-layers deposited by magnetron sputtering using preisach model a. bendjerad (1,2), a. benhaya (2), s. boukhtache (1), m. zergoug (3) , k. benyahia (2) (1) l.e.b, research laboratory electrical engineering department; university of batna 2, 05000 batna, algeria (2) l.e.a, research laboratory electronics advanced; university of batna 2, 05000 batna, algeria (3) c.s.c, centre de soudage et de contrôle, route de dely ibrahim, bp 64, chéraga, algeria corresponding author : bendjerad@gmail.com received: 26 december 2016 / received in final form: 4 march 2017 / accepted: 10 march 2017 abstract : in the present work, thin films of cr/nio/ni are deposited on glass substrates using rf magnetron sputtering technique. the uniformity and homogeneity of the prepared films were controlled by varying the power of the source, the targetsubstrate distance and the pressure of the plasma gas which is argon. in order to test the preisach model, we carried out measurements according to two directions: parallel and perpendicular to the substrate plane using a vibrating sample magnetometer at room temperature. good agreement has been obtained by comparing the experimental hysteresis loops to the ones determined using preisach model. we conclude that this model is powerful in predicting the magnetic properties of multilayer systems. keywords : cr/nio/ni, magnetron sputtering, preisach model, magnetic hysteresis. introduction the exchange coupling between a ferromagnetic material (f) and an antiferromagnetic material (af) is one of the important physical phenomena during the recent decades. it is mainly operated in the case of magnetic thin layers [1]. the choice of nickel oxide (nio), as part of this work, is justified by the alternative it offers in terms of both antiferromagnetic layer and insulation. moreover, it has a very strong corrosion resistance [2]. this choice also finds its origin in the exchange interaction, but in this case, the atomic arrangement is such that this interaction promotes antiparallel spin ordering [3]. as for the ferromagnetic material, we have chosen nickel which is of considerable importance because of its advantageous properties such as the spontaneous magnetization in the absence of magnetic field at room temperature [4-6] and also its total magnetic energy is materials and devices, vol 2(1), 0310 (2017) – doi: 10.23647/ca.md20170310 a.bendjerad et al, modeling of magnetic properties (cr/nio/ni) based multi-layers deposited by magnetron sputtering using… minimum [3]. it is worth noting that chromium as thin films with thickness in the range 10 – 20 nm are widely used to make hard disk drives. the deposited films are composed of crystalline grains which are physically isolated through the segregation of intergranular nonmagnetic chromium to the grain boundaries. it is also importatnt to point out that prior to 2006, all hdds used so-called longitudinal media where the co c-axis lay in the media plane. hence the easy-axis anisotropy direction and magnetization were also in the film plane [7]. the recording layers are deposited on the substrate using sputtering which is the most suitable deposition technique for preparing this kind of films. to achieve a film with adequate magnetic properties, it is important to well set the process parameters which are: composition, thickness and structure of the layer. the magnetic properties of the deposited film also depend on the structure of the chromium underlayer. the deposition parameters for both layers, such as substrate temperature, bias voltage and surface texture, are also very important. it is essential to deposit the recording layers on a chromium underlayer in order to obtain the necessary in-plane orientation [8]. another option for the recording layers is to include a very thin layer of an antiferromagnetic spacer material which has the advantage of orienting the magnetization of the high and low materials, antiparallel for a magnetically more stable configuration. the spacer could be achieved by either depositing a very thin layer of material such as chromium or by oxidizing surface made of ni thus forming nio [9]. however, when one generally makes a ferromagnetic material (f) in contact with an antiferromagnetic material (af), there is an interface of the two materials, which will induce an additional anisotropy in the system called exchange anisotropy [10] which is unidirectional and depends on the used materials and their geometry [3], their crystallinity, texture, interface roughness, distribution, and many other parameters such layer thickness or temperature where the real role is not yet understood [11]. multilayer structures made of cr/nio/ni are widely used in several magnetic and electronic fields such as digital storage, magnetic sensor technology [12-13], magnetic recording media [14-15] or domain stabilizers in recording heads based on anisotropic magnetoresistance [16]. the general deposition techniques used to prepare magnetic layers are spray [17], e-beam [18], pulsed laser deposition [19], chemical bath deposition [20], ion bombardment [21] and molecular beam epitaxy [22]. in the present work, the studied multilayers were deposited on glass substrates using dc and rf magnetron sputtering techniques. experimental protocol thin films of cr/nio/ni are deposited on glass substrates the sizes of which are 5mmx5mmx1mm using dc and rf magnetron sputtering techniques carried out on a sputter type moorfield minilab 060. firstly, the substrates were ultrasonically cleaned in detergent, ethanol and acetone. each cleaning step was carried out during 20 min with, between each two consecutive steps, a thorough rinsing in deionized water heated at 90°c. the substrates were finally dried in a flowing nitrogen gas. high quality of cr, nio and ni targets are used for deposition with purity ranging between 99.94% and 99.99%. the targets were pre-sprayed for 5 min to remove any surface contamination with the shutter in place to prevent the substrates to be exposed. the substrate holder was rotatably held during spraying in order to obtain a homogeneous and uniform growth on the substrate surface. preisach model mathematical modified formulation we obtained through the preisach model and the modified lorentz function the following expression: (1) with: mi-1: the previous magnetisation moment. this formulation makes calculation easier. experimental results materials and devices, vol 2(1), 0310 (2017) – doi: 10.23647/ca.md20170310   dd baba ak tmtm d i h h 2)()( 2 c 2 c 2 1                                  ni rf1 (200 ǻ) glass nio rf2 (35ǻ) cr dc (10ǻ) nio rf2 (35ǻ) ni rf1 (1000 ǻ) figure. 1: thin films (cr/nio/ni) deposited on glass (substrate) a.bendjerad et al, modeling of magnetic properties (cr/nio/ni) based multi-layers deposited by magnetron sputtering using… measurements of magnetic properties were carried out on a vsm ev9 from digital measurement system with a maximum strength field of 2.6 tesla parallel and perpendicular to the substrate plane. figure. 2. shows the hysteresis loops for both parallel and perpendicular cases. as it can be seen, the loop is very slim. hence, we conclude that the losses are very small. it is worth noting that when ni is deposited on nio, the exchange coupling takes place. however, the effects is still relatively lower because of the reduction of contact surface with the af layer. furthermore, the offset field is lower with nio, which is consistent with the interfacial coupling energies reported in literature. the reversal of the magnetization is a basic principle of magnetic recording. magnetization in a material can be reversed by applying a large enough field allowing the material to reach the saturation regime in a direction parallel to the field. the two different states of plus and minus magnetization are the basic idea for digital information storage. the two principal methods for reversing the magnetization are rotation and domain-wall motion and the predominant mechanism depends on the material and its dimensions. both modes can be examined in terms of energy considerations. validation of the experimental model of preisach the identification of the model parameters is conducted by minimizing the deviation of measured and simulated results by an optimization method. in order to test the preisach model, we carried out tests according to two directions: parallel and perpendicular to the substrate plane by comparing the experimental hysteresis loops and those obtained by the model. a result for a typical example is depicted in figure. 3. conclusion we have determined the magnetic properties of antiferromagnet/ferromagnet multilayers of the system cr/ni/nio, using dc and rf magnetron sputtering. magnetic hysteresis loops measured at room temperature for the prepared films revealed that the magnetization is parallel to the substrate plane. a preisach model based on the rotation operator has been presented. the results provided by this model are very satisfactory and are in good agreement with the experimental results. materials and devices, vol 2(1), 0310 (2017) – doi: 10.23647/ca.md20170310 figure. 2: hysteresis loops thin layers based on (cr/nio/ni) magnetic fields applied parallel to the substrate magnetic fields applied perpendicular to the substrate figure. 3: parallel magnetic field experimental (measurement) theoretical (preisach model) simulation a.bendjerad et al, modeling of magnetic properties (cr/nio/ni) based multi-layers deposited by magnetron sputtering using… references 1. g.v. eleftheriades and k.g. balmain, ” negative-refraction metamaterials: fundamental, principles and applications”, ieee press and john wiley & sons, isbn : 0-471-60146-2, 2005. 2. christian hahn, gr´egoire de loubens, v. v. naletov, j. ben youssef, olivier klein, et al.. conduction of spin currents through insulating oxides. 2013. hal id: hal-00875774. 3. céline portemont. “etude de l’anisotropie d’échange dans des agrégats de cobalt nanométriques. matiére condensée [cond-mat]. university joseph-fourier grenoble i, 2006. french. hal id: tel-00120880. 4. j. bass, w.p. pratt jr. physica b, 321, pp. 1–8, 2002. 5. v.k. dugaev, yu. vygranenko, m. vieira et al. p hysica e, 16, pp. 558–562, 2003. 6. m.l. plumer , j. van ek , and w.c. cain (new paradigms in magnetic recording) be-08 http://suessco.com/fileadmin/user_upload/western_digital.pdf 7. k. ishida and t. nishizawa, bull, alloy phase diag., 11 (1990) 357. 8. andicacos and al, “thin film structures for magnetic recording heads”, us 5132859 a 21 juil. 1992, appl. no.: 571,944. 9. yan huang, guopeng wang, shujie sun, observation of exchange anisotropy in single-phase layer-structured oxides with long periods, (2015) doi:10.1038/srep15261. 10. adeline maitre doctor of the university of rouen (study by numerical simulations of fm / afm bilayers with exchange anisotropy) supported on 4 october 2012 hal id: tel-00760007 umr cnrs 6634. 11. h-ch. tong, f. liu, k. stoev, y. chen, x. shi, j. magn. magn. mater., 239.106–111, 2002. 12. s.i. kasatkin, p.i. nikitin, a.m. muravjev et al. sensors actuators, 85, pp. 221–226, 2000. 13. m. ohkoshi, k. tamari, m. harada, s. honda, t. kusuda, ieee transl. j. magn. japan 1 (1985) 37. 14. a.a. glazer, a.p. potapov, r.i. tagirov, sov. phys. jetp. lett. 15 (1972) 259. 15. j.nogués, ivan k. schuller, “exchange bias” journal of magnetism and magnetic materials 192 (1999) 203—232. 16. a. iljinas, j. dudonis, r. brucas, a. meškauskas, nonlinear analysis: modelling and control, 2005, vol. 10, no. 1. 17. wan qing, wang tai-hong, lin cheng-lu, received 2 september 2002 chin.phys.lett vol. 20, no.2 (2003)301. 18. t. katase and al. 4259 nagatsuta-cho, midori-ku, yokohama, japan pacs no: 68.55-a,74.78.-w, 74.25.sv, 74.62.bf, 74. 19. gui-fang huang, al. international journal electrochem.sci, 3 (2008) 145 – 153. 20. romain fleurier, thesis ferromagnetic resonance and structure of iron-based bimetallic nanoparticles universite d'orleans: 11/12/2006. 21. bezencenet odile, thesis doctor of science of the university paris-vi, defended on 2008. materials and devices, vol 2(1), 0310 (2017) – doi: 10.23647/ca.md20170310 rev h. chadli, f. fergani, et al. filling rate dependence on theoretical raman spectra of c60 peapods conference article (international symposium on physics of data storage-1) filling rate dependence on theoretical raman spectra of carbon c60 peapods h. chadli, f. fergani, s. a. ait abdelkader, ah rahmani, b. fakrach, a. rahmani laboratoire d’etude des matériaux avancés et applications (lem2a), université moulay ismail, fsm-estm-estk, bp 11201, zitoune, 50000 meknes, morocco. corresponding author : h.chadli@fpe.umi.ac.ma received: 27 september 2016 / received in final form: 21 december 2016 / accepted: 21 december 2016 abstract : we use the spectral moments method in the framework of the bond-polarization theory to calculate nonresonant raman spectra of c60 peapods as a function of the concentration of fullerenes inside the single wall carbon nanotubes. the evolution of the average raman intensity ratios between raman mode of c 60 molecules and nanotube as a function of the concentration of fullerenes has been analyzed and a general good agreement is found between calculations and measurements. keywords : carbon nanotubes, peapods, raman spectroscopy, spectral moment method, simulation introduction single walled carbon nanotubes (swnt) can encapsulate small and large molecules, including c60 fullerenes[1,2,3]. those systems consist of swnt in which fullerene molecules are inserted and called peapods. this hybrid system between fullerene and swnt have generated a lot of interest for future electronic applications. due to their special onedimensional nanosized structure and their tunable electronic properties, peapods are considered important materials for several potential applications from high temperature superconductor[4] to memory elements[5]. from an experimental point of view, peapods structural analysis can be performed using transmission electron microscopy[1,2] or electron diffraction[3], x-ray scattering[6] or using raman spectroscopy[7]. from a theoretical point of view, it was shown that c60 molecules inside swnts with a wide range of diameters from 1.25 nm to 2.71 nm can form ten different packing arrangements[8]. some of these predicted phases have been experimentally observed[9]. kuzmany et al. have performed a detailed raman analysis of the concentration of c60 fullerenes in peapods[7]. the authors measured the scattering relative intensity from the fullerenes to that from the tube in order to obtain the relative c60 filling concentrations. the relative concentrations derived from the measurement of normalized intensity ratio for each mode of c60 are close (see table 1 of ref. [7]). in previous works [10,11], we calculated the nonresonant raman spectra of c60 peapods for linear and zigzag configurations. in this paper, in order to materials and devices, vol 1(1), 1221 (2016) – doi: 10.23647/ca.md20161221 mailto:h.chadli@fpe.umi.ac.ma h. chadli, f. fergani, et al. filling rate dependence on theoretical raman spectra of c60 peapods improve the comparison with the experimental raman data measured on peapod samples, we calculate the nonresonant raman spectra of c60 peapods with large diameters (2.15-2.3 nm) in which the c60 molecules phase can take a double helix or a two molecules layers configuration depending on the diameter. the relative intensity ratio between a raman mode of c60 and a mode of swcnt, normalized by the same ratio calculated for a reference filling factor, gives a useful method to derive from raman experiments the relative concentration of c60 in peapods samples prepared with the same batch that the reference filling factor sample. model and method the structure of c60s inside swnt depends primarily on tube diameter. we have already studied the different possible configurations of c60 inside swcnt and found that the c60 molecules adopt a linear configuration for diameters below 1.45 nm and a zigzag configuration for diameters between 1.45 and 2.20 nm[9]. in this study, we consider swnt in a diameter range from 2.20 to 2.30 nm in which the c60 molecules can take a double helix or a two molecules layers configuration depending on the nanotube diameter. these configurations of the c60 molecules inside the nanotubes are derived from energy minimization calculations previously described in previous works[10]. the geometrical optimizations of c60 inside swnt are derived. we found that the c60 molecules adopt a double helix arrangement for swnt's diameter in the range 2.16-2.23nm and layers of two molecules for tube diameter in the range 2.23-2.28nm. for the swcnt, the c-c interactions are described using the force constant model introduced by saito[12]. the interactions between carbon atoms for the c60 molecules are calculated using the force constants model described by jishi and dresselhaus[13]. the interactions between carbon atoms belonging to two different molecules (tube-tube, c60-c60 or tube-c60) are described by the familiar (12-6) lennard-jones potential, u lj=4ε[(σ /r) 12 −(σ /r) 6 ] (1) where r is the carbon atom-atom distance, ε=2.964 mev and σ=0.3407 nm are van der waals parameters. results raman spectra calculations are based on the spectral moments method which has proved to be a powerful approach for determining the infrared, raman, and inelastic neutron scattering spectra of harmonic systems (for mor details see refs.[14]). the calculated zz-polarized raman spectra of individual peapods for each configuration of the c60 molecules inside the tube are shown in figure 1 along with their corresponding unfilled nanotubes and the unoriented c60 molecule. in the following, we mainly discuss the polarized zz raman spectra of unfilled zigzag swnts ((n, 0) with n = 17, 28 and 29), and for their corresponding peapods with linear [c60@(17,0)], double-helix [c60@(28,0)], and two-molecule layers phases [c60@(29,0)]. concerning the high-wavenumber modes range, above 1200 cm-1, the main modes of c60 are located around 1219 (hg(6)), 1403 hg(7)), 1468 (ag(2)), and 1582 cm-1 hg(8)), in c60@(17,0), c60@(28,0), and c60@(29,0), independently of the configuration of c60 molecules inside the tube, these modes show a small upshift (1-2 cm-1) with respect to their position in the free c60 spectrum. as already found in linear and zigzag peapods (see figure 2 in ref. [10]), we calculate that the tangential-like modes (tlm) of scnts are almost not affected by the insertion of c60 molecules inside the nanotube. concerning the main modes of (28,0) and (29,0) swnt located at 168, 102 and 98 cm-1 are upshift to 174, 102 and 100 cm-1, respectively. these shift and splitting of radial breathing-like modes (rblm) depend on one side, on the configuration of the c60 molecules inside swnt, and the other side on the coupling effects related to the interactions between the c60 molecules and the nanotube host, and on interc60 interactions. using the spectral moments method, we investigate the evolution of the average non resonant intensity ratios between raman mode of c60 molecules and nanotube as a function of the concentration of c60s inside the tubes. obviously, this non-resonant approach is not able to calculate the dependence of the absolute intensity of each mode with the excitation energies. nevertheless, concerning the dependence of the raman spectrum with the filling factor, the relative intensity ratio between a raman mode of c60 and a mode of swcnt, normalized by the same ratio calculated for a reference filling factor, gives a useful method to derive from raman experiments the relative concentration of c60 in peapods samples prepared with the same batch than the reference filling factor sample. we calculate the dependence of the raman spectrum at different filling factor. to facilitate the comparison with the experimental results, we performed an average of materials and devices, vol 1(1), 1221 (2016) – doi: 10.23647/ca.md20161221 h. chadli, f. fergani, et al. filling rate dependence on theoretical raman spectra of c60 peapods the raman spectra over the peapod orientations with regards to the laboratory frame. raman spectra are calculated in the vv configuration for unoriented peapod samples. for each filling factor, the integrated intensity ratios between a raman mode of c60 and the rblm (for c60 phonon modes: hg(2), ag(1), hg(3) and hg(4)) or g-mode (for c60 phonon modes: hg(7) and ag(2)) are calculated. these calculated intensity ratios are normalized with respect to the same intensity ratios calculated for the 60% filling factor sample. the relative concentrations are derived by this way for the typical c60@(28,0) (double helix chain of c60), c60@(29,0) (two molecule layers), c60@(13,13) (zigzag chain of c60) and c60@(10,10) (linear chain of c60) (fig. 2a, fig.2b, fig 2c and fig.2d, respectively). . figure 1: the zz calculated raman spectra of several phases of c60 inside swnts. spectra are displayed in the breathing mode (a), intermediate (b) and tlm (c) ranges. figure 2: calculated average intensity ratios, normalized on the 60% filling factor intensities, between modes of the c60 in peapods crystal and the rblm (hg(2),ag(1),hg(3), hg(4)) or g-mode (ag(2)) of nanotube. the considered configurations of c60 are linear (a), zigzag (b), double helix (c) and two-molecules layers (d) inside (10,10), (16,16), (28,0) and (29,0), respectively. materials and devices, vol 1(1), 1221 (2016) – doi: 10.23647/ca.md20161221 h. chadli, f. fergani, et al. filling rate dependence on theoretical raman spectra of c60 peapods as expected, for all the investigated peapods diameter, the relative concentrations calculated for each c60 mode are close. the comparison of the data of figure 2 shows that the relative concentrations calculated for infinite peapods increase when the peapod diameter increases. indeed, for a filling factor around 20%, the relative concentration is close to 0.2, 0.4, 0.6 and 0.7 in c60@(10,10) (diameter of (10,10) is 1.35 nm), c60@(13,13) (diameter of (13,13) is 1.76 nm), c60@(28,0) (diameter of (28,0) is 2.19 nm) and c60@(29,0) (diameter of (29,0) is 2.27 nm), respectively. in the c60@(10,10), the average relative concentrations are found between 0.98 and 1.08 following the different c60 phonons modes, in good agreement with the experimental relative concentration evaluated around 1.13[7]. for concentrations around 20% (corresponding to the l43 sample (eels concentration 25±10) in ref. [7]), the average relative concentration is calculated around 0.22± 0.02 except for ag(2) mode showing an overestimated concentration, in good agreement with the experimental relative concentration evaluated around 0.19. conclusion in this work, we calculate the nonresonant raman spectrum of isolated peapods with large diameter and using the spectral moments method. the dependence of the raman spectrum with the c60 filling level have been discussed. the evolution of the average intensity ratios between raman mode of c60 molecules and nanotube as a function of the concentration of c60s have been analyzed and a general good agreement is found between calculations and measurements. acknowledgements: the work was supported by the cnrs-france/cnrst-morocco agreement. references 1. b. w. smith, m. monthioux, d. e. luzzi, nature 396, p 323 (1998). 2. h. kataura, y. kumazawa, y. maniwa, i. umezu i, s. suzuki, y. ohtsuka, y. achiba synth. metals 121 p.1195 (2000) 3. h. hirahara, k. suenaga, s. bandow, h. kato, t. okazaki, h. shinohara, s. iijima phys. rev. lett. 85 p.5384 (2000) 4. r. f. service, science 292, p 45 (2001). 5. y. k. kwon, d. tomanek, and s. iijima, phys. rev. lett. 82, p 1470 (1999). 6. h. kataura, y. maniwa, m. abe, a. fujiwara, t. kodama, k. kikuchi, h. imahori, y. misaki, s. suzuki, y. achiba, applied physics a 74, p 349 (2002) 7. h. kuzmany, r. pfeiffer, c. kramberger, t. pichler, x. liu, m. knupfer, j. fink, h. kataura, y. achiba, b.w. smith, d.e. luzzi appl. phys. a 76, p.449 (2003) 8. m. hodak, l. a. girifalco, phys. rev. b 68, p 085405 (2003). 9. a. khlobystov, d. a. britz, a. ardavan, g. a. d. briggs, phys. rev. lett. 92, p 245507 (2004). 10. h. chadli, a. rahmani, k. sbai, p. hermet, s. rols, and j.-l. sauvajol, phys. rev. b 74, p 205412 (2006). 11. h. chadli, f.fergani, m.bentaleb, b.fakrach, k.sbai, a.rahmani, j.-l.bantignies, j.-l. sauvajol, physicae 71, p 31 (2015). 12. r. saito, t. takeya, t. kimura, g. dresselhaus, and m. s. dresselhaus phys. rev. b 57 p 4145 (1998). 13. r. a. jishi, r. m. mirie, and m. s. dresselhaus, phys. rev. b 45, p 13685 (1992). 14. a. rahmani, j.-l. sauvajol, s. rols, and c. benoit, phys. rev. b 66, p 125404 (2002). materials and devices, vol 1(1), 1221 (2016) – doi: 10.23647/ca.md20161221 introduction model and method results conclusion rev a. m. nassir et al – raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes oaj materials and devices, vol 3, #2, 2110 (2018) – doi: 10.23647/ca.md20182110 p1 article type: a-regular research paper raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes a. m. nassir, ah. rahmani, m. boutahir, b. fakrach, h. chadli, and a. rahmani advanced material and applications laboratory (lem2a), university moulay ismail, fsm, bp 11201, zitoune, 50000 meknes, morocco. *corresponding author : rahmani614@gmail.com received: 12 april 2018 / received in final form: 06 october 2018 / accepted: 08 october 2018 abstract: the structure of boron–nitride nanotubes (bnnts) is very similar to that of cnts, and they exhibit many similar physical and chemical properties. in particular, a single walled boron nitride nanotube (bnnt) and a single walled carbon nanotube (cnt) have been reported. the spectral moment’s method (smm) was shown to be a powerful tool for determining vibrational spectra (infrared absorption, raman scattering and inelastic neutronscattering spectra) of harmonic systems. this method can be applied to very large systems, whatever the type of atomic forces, the spatial dimension, and structure of the material. the calculations of vibrational properties of bnnt@cnt double-walled hybrid nanostructures are performed in the framework of the force constants model, using the spectral moment's method (smm). a lennard–jones potential is used to describe the van der waals interactions between inner and outer tubes in hybrid systems. the calculation of the bnnt@cnt raman active modes as a function of the diameter and chirality of the inner and outer tubes allows us to derive the diameter dependence of the wave number of the breathing-like modes, intermediate-like modes and tangential-like modes in a large diameter range. these predictions are useful to interpret the experimental data. keywords: raman, carbon, boron nitride, smm, nanotube. introduction single-wall carbon nanotubes (scnts) have gained the attention of many experimental, theoretical, and computational research groups. such nanomaterials have rapidly evolved into one of the most fundamental structures in nanoscience and nanotechnology since their discovery by iijima [1]. single-wall boron nitride nanotubes (sbnnts) [2] are intriguing nanotube materials consisting of hexagonal boron nitride sheets. one of the most important features of sbnnts is that bnnts possess a large band gap (around 6 ev) irrespective of the diameters and chiralities [3]. in addition, sbnnts are chemically and mechanically stable [4]. recently, sbnnts inside scnts (sbnnt@scnt) are synthetized with a high yield using a nano-templated reaction and ammonia borane complexes as a precursor [5]. in order to study the vibrational properties of sbnnt@scnt, the raman active modes are calculated. we present the calculated raman spectra in the breathing-like mode (blm), intermediate-like mode (ilm) and tangential-like mode (tlm) ranges. also, we report the frequency dependence on the nanotubes diameter. the results are useful in the interpretation of experimental raman data of sbnnt@scnt. models and methods the structure of a sbnnt@scnt consists of sbnnt inside scnts greatly spaced by intermolecular distance d close to 0.34 nm from minimum energy calculations. the intratube interactions are described by using a force constants model and previously used in our calculations of the raman spectrum of isolated sbnnts [6] and scnts [7,8].van der waals interaction between the inner sbnnt and outer scnt is described by the lennard-jones potential, given by the following expression: 𝑈𝐿𝐽 (𝑟𝑖𝑗 ) = 4𝜖⌈(𝜎 𝑟𝑖𝑗 )⁄ 12 − (𝜎 𝑟𝑖𝑗 )⁄ 6 )⌉ (1) a lennard-jones potential is used to describe the van der waals intertube interactions between the inner sbnnt and outer scnt, where rij is the distance between atoms i and j. the parameters of the bond polarizability model are chosen according to wirtz et al [9]. the energy calculations performed using the lennard-jones potential show that the optimal a. m. nassir et al – raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes oaj materials and devices, vol 3, #2, 2110 (2018) – doi: 10.23647/ca.md20182110 p2 sbnnt-scnt distance d is around 0.34 nm. the raman efficiency of modes is calculated according to the bondpolarizability (bp) model. in this model, the polarizability is only modulated by the nearest-neighbor bonds and the polarizability of a particular bond is assumed to be given by the empirical equation [10]: 𝝌𝜶,(𝒓) = 1 3 (𝓵 + 𝟐𝒑)𝜶, + (𝓵 − 𝒑) (𝒓𝜶𝒓 − 1 3 𝜶,) (2) 𝝌𝜶,(𝒓) = 1 3 (𝓵 + 𝟐𝒑)𝜶, + (𝓵 − 𝒑) (�̂�𝜶�̂� − 1 3 𝜶,) where 𝛼 and 𝛽 denote the cartesian components (x,y,z) and �̂� is the unit vector along the vector 𝑟 connecting the atoms n and m which are covalently bonded. the parameters 𝛼𝑙 and 𝛼𝑝 correspond to the longitudinal and perpendicular bond polarizability, respectively. the usual method to calculate the raman spectrum consists of direct diagonalization of the dynamical matrix of the system. however when the system contains a large number of atoms, the dynamical matrix is very large and its diagonalization fails or requires long computing time. by contrast, the smm allows the raman spectrum of very large harmonic systems to be directly computed without any diagonalization of the dynamical matrix. this approach is used in previous works [11,12]. results and discussions first, we focus on the raman spectra of bnnt@cnt doublewalled hybrid nanostructures. infinite tubes have been obtained by applying periodic conditions on the unit cells of the two swnts. in order to identify all raman active-modes, we present in figure 1 the calculated zz polarized raman spectra of armchair bnnt@cnt. figure 1: calculated zz polarized raman spectra of armchair bnnt@cnt: (5,5)@(10,10), (7,7)@(12,12), and (10,10)@(15,15). spectra are displayed in the blm (left), intermediate (middle) and tlm (right) regions. in all regions of the raman spectra, our calculations state a systematic frequency upshift of the breathing-like modes in bnnt@scnts with respect to sbnnts and scnts due to the van der waals interactions between the two concentric tubes. in the tlm region, spectra are characterized by two modes. the number of raman active modes calculated is independent of the nanotube diameter. we can specify that the modes a1 of bnnt move to the tangential modes cnt, when the diameter increases. in the intermediate mode region, all spectra are dominated by one mode. we observe a downshift with increasing tube diameter. in the blm range, the raman spectrum shows two modes resulting from the in-phase coupled motions of the breathing modes of the inner and outer tubes. for all modes, we observe a frequency downshift with increasing tube diameter, and the intensity of these modes decreases. in the case of zigzag bnnt@cnt (figure 2), we found that if the diameter of carbon nanotubes increases, the peaks corresponding to blm mode and those of the intermediate region are downshifted. figure 2: the calculated zz polarized raman spectra of zigzag bnnt@cnt: (9,0)@(18,0), (17,0)@(26,0), and (26,0)@(35,0) in the blm (left), intermediate (middle) and tlm (right) regions. in the intermediate and tlm regions, the same number of raman active modes in armchair and zigzag sbnnt@scnt is found. in the blm region, a significant dependence of raman active modes as a function of the tube diameter is calculated. our calculations state a systematic up shift of the breathing-like mode frequencies with respect to the frequency of the breathing modes in isolated carbon and boron nitride nanotubes. for the a1 tangential mode of swbnnt@swcnt, all the modes downshift with increasing tube diameter (figure3). the diameter dependence of the specific rblms and especially on the in-phase and counter-phase coupled motions of the rbms of the inner and outer tubes. these modes are called rblm(cnt) (in-phase motions of both tubes) and rblm(bnnt) (counter-phase vibrations of both tubes). for instance, they are, respectively, centered at 165 and 286 cm−1 in bnnt(9,0)@(18,0)cnt. their eigen displacement vectors obtained from the direct diagonalization of the dynamical matrix are displayed in figure 4. one can see that the rblms modes are strongly dependent on the diameter d, is well fitted by the analytical expression: ω(cm−1) = a d (3) the a parameter depending on the mode symmetry (see table 1) the value of this a parameter is close to 231 and 158 nm cm-1 for the rblm(cnt) mode and rblm(bnnt) mode respectively (see table 1), independently of chirality. a. m. nassir et al – raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes oaj materials and devices, vol 3, #2, 2110 (2018) – doi: 10.23647/ca.md20182110 p3 figure 3: diameter dependence on the wavenumber zz infrared active modes for swbnnt@swcnt in the low wavenumber region. systems cnt bnnt modes rblm rbm rblm rbm a(nm.cm-1) 231 224[13] 158 190[14] table 1 : the a parameter for the a/d dependence of the modes as a function of the tube diameter d. figure 4: calculated atomic motions of selected modes in bnnt (9,0)@(18,0)cnt. conclusion in this work, we have calculated the raman spectra of sbnnt encapsulated inside scnt using the spectral moment’s method. the dependence of the positions of the raman-active modes in the low, intermediate, and high wave-number ranges as a function of the encapsulated tube diameter are discussed. we found in the blm range that the raman spectrum shows two modes resulting from the in-phase coupled motions of the breathing modes of the inner and outer tubes. we observed a frequency downshift with increasing tube diameter, and the intensity of these modes decreases. we found also in the tlm regions, the same number of raman active modes in armchair and zigzag sbnnt@scnt. these results are useful in the interpretation of experimental raman data of sbnnt@scnt. references 1. iijima, s.: helical microtubules of graphitic carbon. nature (354), 56–58 (1991). 2. golberg, d. bando, y. tang, c. zhi, c.: boron nitride nanotubes. adv. mater. (19), 2413−2432 (2007). 3. xiang, hj. yang, j. hou. jg. zhu. q.: first-principles study of small-radius single-walled bn nanotubes. physical review b. 68 (3), 035427 (2003). 4. chen, y. zou, j. campbell, sj. le caer, g. : boron nitride nanotubes: pronounced resistance to oxidation .applied physics letters 84 (13), 2430-2432 (2004). 5. nakanishi, r.; kitaura, r.; warner, j. h; yamamoto, y.; arai, s.; miyata, y., shinohara, h. thin single-wall bn-nanotubes formed inside carbon nanotubes. scientific reports volumen 3, article number: 1385 (2013) 6. fakrach, b. rahmani, a. chadli, h. sbai, k. bentaleb, m. bantignies, j. l. and sauvajol. j. l.: infrared spectrum of singlewalled boron nitride nanotubes. phys. rev. b. 85, 115437-115445 (2012). 7. rahmani, a. sauvajol, j – l. rols, s. and benoit, c.: nonresonant raman spectrum in infinite and finite single-wall carbon nanotubes. phys. rev. b. 66, 125404 (2002). 8. rahmani, a. sauvajol, j.-l. cambedouzou, j. benoit, c.: raman-active modes in finite and infinite double-walled carbon nanotubes. phys. rev. b. 71, 125402−125410 (2005). 9. wirtz, l. lazzeri, m. mauri, f. rubio, a.: raman spectra of bn nanotubes: ab initio and bond-polarizability model calculations. phys. rev. b. 71, 241402−241405 (2005). 10. bell, r. j.: method in computational physics, academic, new york, vol. 15 (1976). 11. boutahir, m. (2018). identification of mono-and few-layers graphene: raman study. materials and devices, 3(1). 12. chadli, h. fergani, f. abdelkader, s. a. ait rahmani, a.h fakrach, b. rahmani, a. filling rate dependence on theoretical raman spectra of carbon c60 peapods, materials and devices, vol 1(1), 1221 (2016) 13. sbai, k. rahmani, a. chadli, h. bantignies, j.-l. hermet, p. and sauvajol, j.-l.: infrared spectroscopy of single-walled carbon nanotubes. j. phys. chem. b, 110, 12388-12393 (2006). 14. fakrach, b. rahmani, a. chadli, h. sbai, k. and sauvajol, j. l. raman spectrum of single-walled boron nitride nanotube. physica e. 41, 1800–1805 (2009). https://www.nature.com/articles/srep01385#auth-1 https://www.nature.com/articles/srep01385#auth-2 https://www.nature.com/articles/srep01385#auth-3 https://www.nature.com/articles/srep01385#auth-4 https://www.nature.com/articles/srep01385#auth-5 https://www.nature.com/articles/srep01385#auth-6 https://www.nature.com/articles/srep01385#auth-7 a. m. nassir et al – raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes oaj materials and devices, vol 3, #2, 2110 (2018) – doi: 10.23647/ca.md20182110 p4 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev f. fergani, s. a. ait abdelkader et al. raman-active modes in defective peapod materials and devices, vol 3(1), 0803 (2018) – doi: 10.23647/ca.md20180803 conference paper (ispds2) raman-active modes in defective peapod f. fergani, s. m. ait abdelkader, h. chadli, a. h. rahmani, a. rahmani laboratoire d’etude des matériaux avancés et applications (lem2a), université moulay ismail, morocco. corresponding author : fati.fergani@gmail.com received: 17 january 2018 / received in final form: 08 march 2018 / accepted: 09 march 2018 abstract : the vibrational properties of defective single-walled carbon nanotube filled with c60 fullerene is the subject of the current study. for this aim we use the spectral moments method in the framework of the bondpolarization theory to calculate the nonresonant raman spectra of hexa-vacancy defective c60 peapods. essentially, the vibrational properties are closely coupled with the atomic structure of the system. the evolution of the raman spectrum as a function of the spatial arrangement of defects in carbon nanotubes is discussed. this work provides benchmark theoretical results to understand the experimental data of defective c60 peapod. keywords : single wall carbon nanotubes, c60 peapods, hexa-vacancy defect, raman spectroscopy, spectral moment method introduction since the pioneering study in 1998 by smith et al.[1,2], single wall carbon nanotubes (swnt) filled with c60 fullerene molecules (called peapod) have attracting intensive interest in the material science and nanotechnology community on account of their interesting structure and their excellent electronical and mechanical properties. thus, these materials represent a new class of hybrid systems between fullerenes and swnts where the encapsulated molecules (the peas) and the swnt (the pod) are bonded through van der waals interactions. using high-resolution transmission electron microscopy (hr-tem), suenaga and co-workers[3] elucidated that, the carbon nanotube is not perfect but it has a structural defects. there are several studies on the defects in swnt structure and their effect on mechanical properties of swnt[4,5], however only few literatures are available to date about the effect of defect in peapod. experimentally peapod is made by a purification process, if this process is done imperfectly, some defects may remain on the wall of the peapod[6,7]. the evaluation of effects of defects and impurities on properties of these nanostructures would be crucial because of the inevitable creation of defects during the synthesis and purification processes[8] and under mechanical strains[9,10]. the most typical type of defects in crystalline lattices are point vacancies, interstitials, and bound complexes of the two. a missing or extra atom is a small perturbation in weakly bonded metal crystals, but it is not the same for the graphene. when vacancies and interstitials are highly disfavored, bond rotations are not, and these constitute the most prevalent type of defect in high quality graphites. a single bond rotation only affects four adjacent hexagons, converting two into pentagons and two into seven-sided heptagons, known in the literatura as a stone-wales (sw) defect. the simplest defect type is a vacancy where a lattice site is unoccupied. the presence of vacancies may deteriorate the outstanding properties of nanotubes but may also have beneficial effects. in previous works of our group[11,12,13], we calculated the vibrational properties of non defect c60 peapods. in order to improve the comparison with the experimental raman data measured on peapod samples, we calculate the nonresonant raman spectra of c60 filled hexa-vacancy swnt. mailto:e-mail@address f. fergani, s. a. ait abdelkader et al. raman-active modes in defective peapod materials and devices, vol 3(1), 0803 (2018) – doi: 10.23647/ca.md20180803 in this aim, we calculate the nonresonant raman spectra in the framework of the bond-polarizability model combined with the spectral moment method. this paper is organized in the following way. in section 2 we present the used model and method. results of calculations are the aim of section 3, the final section is conclusions. model and method vacancy defects are always presented in swnts due to postprocessing, including ion[14] and electron irradiation[15], and so on. in this study, we focus on vibrational properties of c60 inside hexa-vacancy defect in swnt. the starting point for the majority simulation techniques is the calculation of the dynamical matrix of the system, and so will it be for this article. the dynamical matrix of c60 inside defective swnt is calculated by block: the intramolecular interactions between carbon atoms at the surface of the c60 molecules are modelized by the force constants model described by jishi and dresselhaus[16], the c-c intratube interactions at the surface of defective swnt are calculated using density functional theory (dft) as implemented inside the siesta package[17] and the dynamical matrices associated with the coupling between the different subsystems (c60-swnt and c60-c60 interactions) are described by the familiar (12-6) lennard-jones potential,     6124)( rrru lj   , where r is the carbon atom-atom distance. we fixed 2.964 mev and 3407.0 nm according to ref. [18]. raman scattering studies has been extensively used to identify structural defect and nondefect in carbon nanotube and peapods. the intensities of the raman lines are calculated within the empirical non-resonant bond polarizability model[19]. in this study we use the same bond polarizability parameters used in our previous work concerning the calculation of the raman spectra of individual c60 and c70 peapods[12,20]. the d-band in the raman spectra of sp2 carbons is a signature of defects in the graphene lattice[21] and is often used to characterize defective swnts. however, the interpretation of the d-band feature might be ambiguous as a large observed d-band intensity might originate from one nanotube while the radial breathing mode (rbm) or graphitic g-band could be due to another tube present in the same sample[22]. results in this work, we focus primarily on vibrational properties of hexa-vacancy defect in both swnt (see figure 1) and peapod. for this aim we study the raman spectra of hexavacancy defect in (10,10) swnt as a function of defect concentration. however, it is found from figure 2 that compared with that in the perfect swnts, although the hexa-vacancy leads to a redshift of the tube’s rbm frequency. when the concentration of hexa-vacancies increases rbm downshift from 164 cm-1 in pristine tube to 161 cm-1, 160 cm-1, and 158 cm-1 for 2%, 3%, and 4% hexa-vacancies concentration in (10,10) swnt, respectively. a second-lowest raman-active mode located at 328 cm-1, 330 cm-1, 338 cm-1 for 2%, 3%, 4% hexa-vacancy concentrations for (10,10), this mode correspond to hexavacancy defect in (10,10) nanotube. figure 1: schematic of both pristine (a) and hexavacancy defect (b) in swnt. figure 2: zz-polarized raman spectra of armchair carbon nanotube (10,10) as a function of hexavacancies defects concentration. the ratio of the dto the g-band intensity (id/ig), is usually used for a measurement of the disordered and the defect sites on carbon nanotubes walls, and it is useful to determine both the purity and the defect density, which has been difficult to accomplish by means other than raman spectroscopy. in fact, the decrease of the intensity of the g mode upon defect creation increases the id/ig intensity ratio, which could lead to an estimation of the amount of defects. the data in figure 3 shows the id/ig ratio increased linearly for (10,10), from 0 to 10% concentration. because of their structural and vibrational properties, a lot of theoretical and experimental studies have been presented on c60 and c70 fullerenes and several interesting properties have been predicted or observed. despite the large number of experimental results on the defect-induced changes to the raman spectra of nanotubes samples the information that can be extracted from such analyses is limited and thus many issues remain unclear. in particular, the vibrational studies of defects peapods need more studies, for this purpose and in order to investigate the effect of hexa-vacancy defect on the oscillatory behavior of c60 peapod oscillators, we calculate zzpolarized raman spectra of individual peapods for linear configuration of the c60 molecules inside (10,10) as a function of hexa-vacancy defect rates. for this purpose, four defect rates 0%, 0.6%, 1.2%, 1.8% in (10,10) have been considered, when the swnts fill with a 320, 269, 218, 167 c60 f. fergani, s. a. ait abdelkader et al. raman-active modes in defective peapod materials and devices, vol 3(1), 0803 (2018) – doi: 10.23647/ca.md20180803 figure 3: the intensity ratio id/ig for (10,10) armchair swnt is plotted as a function of the concentration of hexa-vacancy defect in the nanotube walls. molecules, respectively, the results are shown in figure 4. the zz raman spectra are displayed in the peapod radial breathing-like modes (prblm) range (left), in the region of the radial c60 modes and d band of defective swnt (middle), and in the range of tangential modes: ag(2) mode of c60 and gmodes of the tubes (right). the comparison between the calculated raman spectra of perfect and defect peapods does not show significant differences in the intermediate and high-frequency regions except a new mode due to hexa-vacancy defect in swnt (mode d) located at 1355 cm-1. the modes located in the breathing-like mode range are very sensitive to the defect in swnt because major changes in frequencies and intensities are observed. concerning the rblm mode of prestine c60@(10,10) peapod is downshifted by 3 cm-1 independent of defect rate in peapod wall. regarding the main lowest frequency raman active modes of c60 no significant modification was observed in the hg(2) and ag(1) modes on defective peapod. by contrast, the increase of defect rate from 0% to 1,8% leads to a downshift of the hg(1) mode by 12 cm-1 with respect to the hg(1) mode of c60 molecule. figure 4: hexa-vacancy rate dependence of the zz-polarized raman spectra of c60@(10,10) peapods. f. fergani, s. a. ait abdelkader et al. raman-active modes in defective peapod materials and devices, vol 3(1), 0803 (2018) – doi: 10.23647/ca.md20180803 conclusion in this paper, we have studied defects of the polarized raman spectra of hexa-vacancy in both (10,10) armchair single-walled carbon nanotube and c60@(10,10) peapod as a function of the concentration of defects using the bond polarizability model combined with the spectral moment’s method. by examining the raman intensities calculated for defective nanotube samples containing specific defects hexavacancy, we conclude that id/ig ratios is sensitive to the defect concentration. all these predictions help us to explain the experimental raman spectra of hexa-vacancy defect in nanotubes and in peapods. acknowledgements: the work was supported by the cnrs-france/cnrst-morocco agreement. references 1. b. w. smith, m. monthioux, d. e. luzzi, nature, vol.396, p 323 (1998) 2. b. w. smith, m. monthioux, d. e. luzzi, chem. phys. lett., vol.315, p 31 (1999) 3. k. suenaga, t. okazaki, k. hirahara, s. bandow, h. kato, a. taninaka, h. shinohara, s. iijima, appl. phys. a, vol.76, p 445 (2003) 4. x. hao, h. qiang, y. xiao-hu, carbon, vol.45, p 2486 (2007) 5. x. hao, h. qiang, y. xiao-hu, compos. sci. technol, vol.68, p 1809 (2008) 6. b.w. smith, chem. phys. lett., vol.321, p 169174 (2000) 7. b. burteaux, a. claye, b.w. smith, m. monthioux, d.e. luzzi, j.e. fischer, chem. phys. lett., vol.310, p 21 (1999) 8. m. b. nardelli, b. i. yakobson, j. bernholc, phys. rev. b, vol.57, p r4277 (1998) 9. w. fa, f. hu, j. dong, phys. lett. a, vol.331, p 99 (2004) 10. h. kim, j. lee, s.-j. kahng, y.-w. son, s.b. lee, j. ihm, y. kuk, phys. rev. lett., vol.90, p 216107 (2003) 11. h. chadli, a. rahmani, k. sbai, j.-l. sauvajol, physica a., vol.358, p 226 (2005) 12. f. fergani, s. a. abdelkader, h. chadli, b. fakrach, ah. rahmani, p. hermet, and a. rahmani, journal of nanomaterials, vol.2017, p 1 (2017) 13. h. chadli, f. fergani, s. a. ait abdelkader, ah rahmani, b. fakrach, a. rahman, materials and devices, vol.1, no. 1, p 1221 (2016) 14. a. v. krasheninnikov, k. nordlund, m. sirvi, e. salonen, and j. keinonen, phys. rev. b, vol.63, p 245405 (2001) 15. p. m. ajayan, chem. rev., vol.99, p 17871799 (1999) 16. r. a. jishi, l. venkataraman, m. s. dresselhaus, g. dresselhaus, chem. phys. lett., vol.209, p 77 (1993) 17. j. m. soler, e. artacho, j. d. gale, a. garca, j. junquera, p. ordejon, d. sa nchez-portal, j. phys.: condens. matter, vol.14, p 2745 (2002) 18. h. ulbricht, g. moos, t. hertel, phys. rev. lett., vol.90, p 095501 (2003). 19. s. guha, j. menendez, j.b. page, g.b. adams, phys. rev. b, vol.53, p 13106 (1996) 20. f. fergani, h. chadli, a. belhboub, p. hermet, a. rahmani, j. phys. chem. c, vol.119, p 5679 (2015) 21. f. tuinstra, j. l. koenig, j. chem. phys., vol.53, p 11261130 (1970) 22. w. a. saidi, p. norman, phys. chem. phys., vol.16, p 1479 (2014) f. fergani, s. a. ait abdelkader et al. raman-active modes in defective peapod important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com materials and devices, vol 3(1), 0803 (2018) – doi: 10.23647/ca.md20180803 http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p1 article type: t-technical paper dynamic modeling of double star synchronous generator with permanent magnets gning n s (1) (2), nadia ait a. (1), seck a. (2), mourad ait a. (1), thiaw l. (2), benkhoris m.f. (1) (1) ireena, university of nantes, saint nazaire, france (2) l.e.r, university cheikh anta diop of dakar, dakar, senegal corresponding author : nabou439@gmail.com received: 11 june 2019 / received in final form: 05 august 2019/ accepted: 07 august 2019 abstract: in this paper, the dynamic modeling of the double-star generator is presented, then its adaptation in an electromechanical conversion. we reported all torque production to the first equivalent submachine to minimize losses. the model implementation is done under the matlab/simulink environment. the dc bus current and voltage control loops have been realized by synthesizing a pi controller. the results obtained are consistent with a good followup of the imposed references.. keywords: double star generator; electromechanical conversion; controller pi; dynamic modeling. introduction faced with the global demand for nature conservation and the maintenance of natural biodiversity, the world is moving to wards renewable energies to generate electricity. in this context the demand for electromechanical converters is increasing. often the architecture of an electromechanical energy conversion consists in adding a three-phase alterna ting machine to a three-phase pwm (pulse width modula tion) converter. with this classic architecture, a defect in one element of the energy conversion chain alone can cause the actuator to loose total or partial control. therefore, to increase the reliability of the energy conversion chain, the use of two machines for the redundancy problem often creates difficulties related to comanagement. recently [1][2] the use of double stator machines was proposed, allowing to integrate two machines in one, with two independent windings connected in stars. studies carried out on double star machines show that in addition to reducing the pulsation amplitudes of the torque by using a large number of phases, a good choice of the phase cite this article: n.s. gning , nadia. ait.a, mourad. ait. a, seck. a, thiaw.l, benkhoris. m.fl, oaj materials and devices, vol 4 (2), 0208 (2019) – doi : 10.23647/ca.md20190208 mailto:nabou439@gmail.com n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p2 shift angle between the two stator stars, in this case an electrical angle of 30 degrees, further reduces these pulsa tions, making them even more attractive [3][4]. this configuration has been applied to asynchronous ma chines [5][6][7][8] and to permanent magnet synchronous machines in motor operation[9]. we propose to replace conventional machines (three-phase) by synchronous double-star permanent magnet machines in generator operation connected to a continuous bus. in this paper, first we present the modeling of the perma nent magnet fem double star generator. the pi controller and the description of the machine control are the second part. third, we present the simulation results performed under the matlab/simulink environment. dynamic modeling of the generator the topology ds-pmsg -converter-bus continuous can be done using several structures of converters. we are inte rested in this study to the structure with three-phase con verters because it is the most used in the industry. in this case the converters can be: -independent: each of the stars is connected to its own source of dc voltage via a three-phase converters. -in parallel: all the stars are connected to the same dc voltage source via the three-phase converters. from these two topologies, we will choose the topology to a single continuous capacitor bus c which is less cumbersome and reduces the cost of installation. the load is represented by a resistive load r. assumptions the modeling of a ds-pmsg is based on the following main assumptions: •magneto-motive forces have a sinusoidal distribution. •mutual inductance are characterized only by their funda mental. •magnetic saturation is neglected. •the two stars are strictly identical and shifted up by an angle π/6. ds-spmg modeling in abc frame as shown in figure 1, the ds-spmg is represented the stator structure is described as follows two three-phase windings (a1,b1,c1; a2,b2,c2) offset by an angle of 30 degrees. θ gives the rotor position. figure 1: ds-spmg in abc frame this allowed to consider and to modeling the ds-spmg as a six-phase generator. the stator voltage equation for the six phases is given by equation (1) as follow: (1) ds-spmg model in (α; β, z1; z2; o1; o2) frame in the (α; β) frame, all axes are projected to pass from a three-phase to a two-phase frame. figure 2: projection in α, β frame in order to minimize the coupling between the state variables, we can rewrite the model of the machine in the orthonormal frame α, β, z1; z2; o1; o2, applying the transformation matrix t6 [11]. [iα; iβ; iz1; iz2; ic1; ic2]= [t6] [is] n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p3 after calculation, the model given by equation (1) becomes: (2) : maximum value of mutual inductance : leakage inductance : pulsation : magnetic flow applying this basis change, the obtained model is composed of two fully decoupled submachines: •the primary submachine, expressed in the reference α; β, contributes to the generation of electromechanical torque. •the secondary submachine expressed in the reference z1; z2; o1; o2 not participate in the generation of the electro magnetic torque. ds-pmsg modeling in park frame only the primary submachine contributes to the electroma gnetic conversion of the torque. the second submachine is only a seat of losses.the park transform is applied only pri mary submachine. the model is given by equation (3): (3) +3 controller design principe to prevent the second submachine to generate losses without producing torque, its currents are imposed null. always with the aim of minimising losses, the id current of the primary submachine is imposed at zero. this allows the torque to be linearized at the same time simulation results the control block shema is represented by figure 3. we have two control loops: an external loop that controls the dc bus voltage; an internal loop (in red color in figure 3) to regulate the currents in the dq mark. in the simulator, the converters are replaced by a gain g. we synthesized pi regulators for currents and voltage using. the pole compensation method. in the following, we have substituted the indices d, q, z1, z2 respectively to dp, qp, ds, qs so that the indices refer to the primary and secondary submachine. reg: regulation block containing four pi for regulation of four current. n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p4 dec: decoupling block ds-pmsg: this block represents the machine and contains its dynamic model calcul.power: power calculation block based on the voltages in the dq frame calcul.uc2: block for calculating the dc bus voltage uc from the power. calcul.iqref: block for calculating the iqref current, which is the only non-zero current of the machine. figure 3: synoptic of regulation figure .4. simulation results in figure 4, we have the four currents (id, iq, iz1, iz2) that exactly follow the imposed references. the simulation results show that only the first submachine participates to the production of torque as seen in the mo delling. therefore, it is the only one to produce the full power of the dual generator. this result not only validates the modeling of the generator but also minimizes losses. these results also allow industries to increase the reliability of operation while remaining in the classic electronic power point of view, conclusion in this paper, a dynamic modeling approach to the double star generator was developed. then we implemented the model on a simulator developed in matlab / simulink environment. we used the pi regulator. the simulation results show a good follow-up of the imposed references and allows to validate the model. in the following we think about regulate the dynamic model of the generator in degraded mode. n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p5 references [1]zhang, a houari, a seck, l moreau, “fault tolerant of a double stator permanent magnet generator in tidal curent energy system,” ieee, vol. 978, pp. 4678–8075, 2016. [2]gregor, r., barrero, f., toral, sl, duran, mj, arahal, mr, prieto, j. et mora, jl (2010). méthode de contrôle du courant pwm vectoriel à espace prédictif pour entraînements de moteurs à induction triphasés doubles asymétriques. iet electric power applications , 4 (1), 26-34.e. [3]b. sedrine, “machines à commutation de fux à grand nombre de phases : modèles comportementaux en mode dégradé et élaboration d’une stratégie de commande en vue de l’amélioration de la tolérance aux pannes,” ph.d. dissertation, ecole normale superieure de cachan, 2014. [4]fall, o., charpentier, j. f., nguyen, n. k., & letellier, p. (2016, june). comparaison de performances de différentes structures de machines synchrones à aimants permanents (msap) polyphasées en mode normal et en modes dégradés en vitesse variable avec défluxage pour des applications hydroliennes. [5]d. hadiouche, “contribution à l’étude de la machine asynchrone double étoile: modélisation, alimentation et structure,” ph.d. dissertation, université henri poincaré, nancy-i, 2001. [6]a. yahdou, “commande et observation par mode glissant d’une machine asynchrone double étoile sans capteur mécanique,” master’s thesis, université henri poicare nancy-i, 2001. [7]m. yacine, “contribution à l’étude de la machine asynchrone doubleétoile. application à la sureté de fonctionnement.” ph.d. dissertation, université freres mentourii-constantine, 2015. [8]li, kang, doki, shinji, et fujitsuna, masami. the position sensorless control for the wound-field synchronous motor with double three-phase wound stator in stop/low-speed driving. in : iecon 2015-41st annual conference of the ieee industrial electronics society. ieee, 2015. p. 003218-003223.. [9]b. naas, “direct torque control based three level inverter-fed double star permanent magnet synchronous machine,” science direct, vol. 18, pp. 521–530, 2012. [10]f. terrien and m. benkhoris, “analysis of double star motor drives for electrical propulsion,” in electrical machines and drives ninth international conference on iet, vol. 468, pp. 90–94, 1999. [11] m.merabtene, “modelling of a double star synchronous motor fed by pwm inverter under fault conditions,” international conference on electrical machines icem’2002, bruges, belgique, 25-28 august 2002, cd-rom. [12]l. parsa, “on advantages of multi-phase machines,” in 31st annual conference of ieee industrial electronics society, 2005.iecon 2005.ieee,p. 6, 2005. [13]e. levi, “multiphase electric machines for variable-speed applications,” ieee transactions on industrial electronics, vol. 55, no. 5, pp. 1893–1909, 2008. [14]shamsi-nejad, mohammad-ali, nahid-mobarakeh, babak, pierfederici, serge, et al. fault tolerant permanent magnet drives: operating under open-circuit and short-circuit switch faults. king mongkut’s university of technology north bangkok international journal of applied science and technology, 2014, vol. 7, no 1, p. 57-64.b. n. badreddine naas, nezlie, “direct torque control based three level inverter fed double star permanent magnet synchronous machine,” science direct, vol. 18, pp. 521–530, 2012. [15]a. rockhill and t. lipo, “a generalized transformation methodology for polyphase electric machines and networks,” in electric machines & drives conference (iemdc), 2015 ieee international. ieee, pp. 27–34, 2015. [16]a. dieng and al, “fault-tolerant control of 5-phase pmsg for marine current turbine applications based on fractional controller,” ifac proceedings volumes, vol. 47, no. 3, pp. 11 950–11 955, 2014. complementary informations on authors ndeye seynabou gning ndeye-seynabou.gning@etu.univ-nantes.fr, https://www.researchgate.net/profile/ndeye_gning2 lamine thiaw: lamine.thiaw@ucad.edu.sn, https://www.researchgate.net/profile/lamine_thiaw mouhamed fouad benkhoris mohamed-fouad.benkhoris@univ-nantes.fr, https://www.researchgate.net/profile/mohamed_fouad_benkhoris https://www.researchgate.net/profile/ndeye_gning2 https://www.researchgate.net/profile/lamine_thiaw https://www.researchgate.net/profile/mohamed_fouad_benkhoris n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p6 [17]iffouzar, k., benkhoris, m. f., ghedamsi, k., & aouzellag, d. (2016). behavior analysis of a dual stars induction motor supplied by pwm multilevel inverters. revue roumaine des sciences techniques-serie electrotechnique et energetique, 61(2), 137-141. [18]l. parsa and h. a. toliyat, “fault-tolerant five-phase permanent magnet motor drives,” in industry applications conference, 2004. 39th ias annual meeting. conference record of the 2004 ieee, vol. 2. ieee, pp. 1048–1054, 2004. n.s.gning et al – dynamic modeling of the double star synchronous generator with permanent magnets oaj materials and devices, vol 4 (2), 0208 (2019) – doi: 10.23647/ca.md20190208 p7 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev b. allouche, y. gagou, and m. el marssi – lead potassium niobate thin films grown by pulsed laser deposition a: regular paper lead potassium niobate thin films grown by pulsed laser deposition b. allouche, y. gagou and m. el marssi lpmc, université de picardie jules verne, 33 rue saint leu, 80039 amiens cedex, france corresponding author: allouche_bilal@hotmail.fr received: 12 september 2016 / received in final form: 7 january 2017 / accepted: 13 january 2017 abstract: by pulsed laser deposition, lead potassium niobate pb2knb5o15 was grown on (001) oriented gd3ga5o12 substrate using a platinum buffer layer. the pkn thin films were characterized by x-ray diffraction and scanning electron microscopy (sem). the dependence of their structural properties as a function of the deposition parameters was studied. it has been found that the out of plane orientation of pkn film depends on the oxygen pressure used during the growth. indeed, pkn thin film is oriented [001] for low pressure and is oriented [530] for high pressure. for these two orientations, the crystalline quality of pkn film was determined using omega scans. keywords: ferroelectric thin film, ttb-structure, pld, pkn introduction in the recent years, some studies have shown the increasing interest of materials with tetragonal tungsten bronze (ttb) structure by demonstrating their potential technological applications [1–5]. among the tetragonal tungsten bronze (ttb) oxides, lead potassium niobate pb2knb5o15 (pkn) is one of the bestknown compounds [6,7]. it has an orthorhombic structure at room temperature with cell parameters: a=17.754(2) å, b = 18.014(2) å and c = 3.915(1) å [8]. pkn ceramic presents a behavior of a classical ferroelectric and undergoes a ferroelectric-paraelectric phase transition at tc=450 °c [9], changing the point symmetry from p4/mbm (n° 127, paraelectric) to cm2m (n° 38, ferroelectric). at room temperature pkn is ferroelectric and ferroelastic as refined by sciau et al. [7]. the ferroelectric polarization in pkn is oriented along the b axis of the orthorhombic unit cell. above curie temperature, pkn is paraelectric and paraelastic with a tetragonal symmetry (space group p4/mbm n° 127) [9]. pkn was previously studied for its piezoelectric, ferroelectricferroelastic coupling, optical properties, and surface-acousticwave (saw) properties [6,9–13]. so pkn thin films can be of a great interest for ferroelectric and ferroelastic applications. furthermore, the higher curie temperature of pkn makes it very interesting for several optical and ferroelectric-ferroelastic coupling applications [10]. because of the complexity of the ttb structure [14], compounds with such structure as thin films are very rare, materials and devices, vol 1(1), 1401 (2016) – doi: 10.23647/ca.md20171401 mailto:allouche_bilal@hotmail.fr b. allouche, y. gagou, and m. el marssi – lead potassium niobate thin films grown by pulsed laser deposition especially because, nowadays no ttb-structure substrates are available. in this context, realization of ttb-structured thin films is a significant issue. herein, we make a proposition to grow oriented pkn thin film by choosing an adapted substrate. pulsed laser deposition (pld) technique is also known and repeated to be adapted to grow usually complex structures since it uses a uv laser for a congruent transfer from target to substrate. experimental pkn target was prepared by a solid state reaction starting from the oxides k2co3, nb2o5 and pbo (sigma aldrich, 99.99 %): 4pbo + k2co3 + 5nb2o5  pb4k2nb10o30 + co2 (1) the stoichiometric mixture was dried at 650 °c for 6 h, and then annealed at 1100 °c for 20 h. the obtained powders were pressed into ceramics of about 2cm in diameter and 5 mm in thickness. the ttb structure with orthorhombic cell (a=17.754(2) å, b = 18.014(2) å and c = 3.915(1) å) was confirmed by using x-ray diffraction (xrd). pkn thin film has been grown on (001)-gd3ga5o12 (ggg) substrates by pulsed laser deposition. 50 nm thick platinum (pt) buffer layer was also deposited by pulsed laser deposition, this will serve as bottom electrode for further electrical measurements. the following table summarizes the pld parameters used to grow pkn thin film: table 1: experimental conditions used to grow pkn and pt films by pld pt layer pkn films substrate temperature 25 °c 750 °c oxygen pressure 10-6 mbar 0.03 and 0.15 mbar targetsubstrate distance 2.5 cm 3.8 cm laser frequency 5 hz 3 hz time deposition 13 minutes 55 minutes laser fluency 2.5 j/ cm2 1.9 j/cm2 note that the temperature of 750 °c is the minimum necessary to achieve good crystallinity for pkn films. indeed, below 750 °c no bragg peak related to pkn phase was detected by xrd. two different values of oxygen background pressure were used to elaborate pkn thin films (0.03 and 0.3 mbar). after deposition, the average thickness of the obtained films, controlled by the deposition rate, was around 200 nm (±10%) for pkn and 50 nm for pt. the deposition rate was determined from thick films using dektak profilometer in pkn case, and from the simulation of laue oscillations in the case of pt layer (see results section). the films were systematically characterized by x-ray diffractometry performed on a two-circle siemens d5000 diffractometer using θ-2θ and rocking curves scans. all experiments were performed using a 0.1mm slight before and after the sample. the x-ray tube was operating at 40 kv and 40 ma (kα cu: 1.54056 å). sem micrographs were performed using fei-quanta 200f microscope. results and discussion gadolinium gallium garnet (ggg) [15] substrate is an oxide with cubic structure with m3m symmetry, its bulk cell parameter is a=12.382 å. it is usually used as substrate to grow epitaxial iron and yttrium garnet. because of its cell parameter, which is so close to that of general ttb materials, ggg substrate can be of a great interest to grow oriented and epitaxial ttb compounds. as shown in table 1, pkn thin film has been deposited under different oxygen pressures, 0.03 and 0.15 mbar. fig 1 shows xray diffractogram of 200 nm thick pkn film grown on pt(50nm)/ggg substrate. we note that pt layer is oriented along its [111] direction. smooth and well-structured laue oscillations appeared from either side of the (111)pt peak indicating a good crystalline quality of pt layer along the growth axis. these oscillations have been simulated and allowed to control with precision the pt layer thickness. pt out of plane lattice parameter deduced from this diffractogram, assuming a cubic structure, is cpt = 3.924 å (± 3%). the simulation was performed using the following relation: i=i 0 sin 2 ⁡(2 π c n c sin ⁡θ / λ) sin 2 ⁡(2 π c sin ⁡θ / λ) (2) where: i is the diffracted intensity, c the lattice parameter and nc the number of unit-cells along the growth axis. concerning pkn film, in the case of low pressure (0.03 mbar, fig 1 (a)), only the (00ℓ) bragg reflections can be seen. pkn is oriented [001] and its polar axis is parallel to the substrate. the out-of-plane cell parameter deduced from this diffractogram is cpkn=3.932 å (± 1%). this value is higher than the ccell parameter in bulk pkn (c=3.915 å), which means that pkn should be strained in the plane by the substrate. in addition, we observe that the peak (002)pkn is narrower than the (111)pt: remember that the peak width is inversely proportional to the crystallites size along the growth direction. thus, pkn film crystallites size would be larger than that of the pt layer. materials and devices, vol 1(1), 1401 (2016) – doi: 10.23647/ca.md20171401 b. allouche, y. gagou, and m. el marssi – lead potassium niobate thin films grown by pulsed laser deposition figure 1: semilogarithmic -2 x-ray diffractograms of pkn thin film films are of about 200 nm in thickness, deposited on pt(50 nm)/ggg substrate under oxygen partial pressures of a): 0.03mbar and b): 0.15 mbar. c): zoom around (111)pt peak showing laue oscillations fit. in the case of high pressure (0.15 mbar, fig 1 (b)), besides (00ℓ)ggg and (111)pt peaks, only the (530) and its upper order (10 60) bragg reflections related to pkn are observed. in these conditions, pkn thin film is clearly oriented [530]. this result is very reproducible even for very low thicknesses. for this orientation, any pkn cell parameter cannot be deduced from this diffractogram. however, the polar axis of the orthorhombic cell is out of the substrate plane. this will be more suitable for some ferroelectric applications that requires out of plane polarization switching. films mosaicity was investigated by omega scans performed around the reflections of pkn, pt and ggg substrate (fig. 2). in the case of [001]pkn, the full width at half maximum (fwhm) of (111)pt and (002)pkn are about three times as high as that measured on (004) ggg, which was 0.30°. also, it is so important to note that the mosaicity in pkn film (1.3°) is quite comparable to that of the pt layer. so, one can conclude that the mosaicity in pkn is mainly due to the pt layer. figure 2: ɵ-2ɵ (left) and omega (right) scans performed around: (111)pt, (002)pkn and (530)pkn respectively. in the case of [530]pkn film, both pt and pkn layers show a large mosaicity along the growth axis. values are similar to that obtained for [001]. moreover, omega scans show a smaller mosaicity compared to that in pkn oriented [530]. all values are summarized in the table 2. table 2: fwhm of bragg peaks relative to the substrate and to the pt and pkn films. δ2 (°)ɵ δω (°) (004)ggg 0.044 0.310 (111)pt 0.242 0.877 (002)pkn 0.197 1.299 (530)pkn 0.124 0.861 fig. 3 shows sem micrographs performed on the top surface of the pkn thin film. one can see regular surfaces with an homogeneous microstructure and uniform grain distribution. for the low pressure deposition film (i.e. (001)pkn thin film), the materials and devices, vol 1(1), 1401 (2016) – doi: 10.23647/ca.md20171401 b. allouche, y. gagou, and m. el marssi – lead potassium niobate thin films grown by pulsed laser deposition figure 3: sem pictures of the previously presented (001)pkn and (530)pkn thin films respectively. grains are flat and parallel to the substrate surface. in contrast, for the high pressure film deposition (i.e. (530)pkn thin film) the grains have rather spherical shape. we also note that the average grain size is similar for both films, which is due to the used elaboration conditions (the same temperature, 750°c). the films surface doesn’t present any cluster nor pld droplets, due to the optimized laser energy. conclusion lead potassium niobate thin films have been successfully elaborated using pulsed laser deposition on (111)pt/(001)ggg. pkn thin films orientation can be controlled by setting up the oxygen partial pressure during the growth. in fact, as function of the oxygen partial pressure, pkn grew with in-plane or outof-plane ferroelectric polarization. this study clearly demonstrated that the (111)pt layer determines pkn orientation. this assumes that the growth of pkn on pt/si substrate would be quite possible; because the growth of platinum is already mastered on si and (111)pt/si substrates are available. this makes pkn compound compatible with an implementation in microelectronic devices, especially because lead based ttb compounds, such as pkn, often show partial ferroelastic-ferroelectric coupling properties, which is very advantageous for memories and optical gates applications. acknowledgements: the present work was financially supported by the french ministry of higher education and research. references [1] k. lin, h. wu, f. wang, y. rong, j. chen, j. deng, r. yu, l. fang, q. huang, x. xing, structure and thermal expansion in tungsten bronze pb2knb5o15, dalton trans. 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[15] h. asada, a. kuwahara, k. sueyasu, t. ishibashi, q. liu, g. lou, k. kishimoto, t. koyanagi, longitudinal spin seebeck effect in bi-substituted neodymium iron garnet on gadolinium gallium garnet substrate prepared by mod method, phys. procedia. 75 (2015) 932–938. doi:10.1016/j.phpro.2015.12.128. materials and devices is an open access journal managed by scientists for science. issn 2495-3911 it is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed! we apply «the principles of transparency and best practice in scholarly publishing» as defined by the committee on publication ethics (cope). copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercialnoderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. materials and devices aims at publishing papers on all aspects related to materials, namely according to their chemical formula, to their physical properties, to their nature, or according to some specific applications. papers on biomaterials, geomaterials, archeomaterials or on studies of ancient materials are also welcome. a particular attention is also paid to environmental studies related with materials. authors are also encouraged to submit papers on theoretical studies applied to materials. concerning devices, the scope is restricted to those integrating particular materials. http://materialsanddevices.co-ac.com/ materials and devices, vol 1(1), 1401 (2016) – doi: 10.23647/ca.md20171401 http://materialsanddevices.co-ac.com/ https://creativecommons.org/licenses/by-nc-nd/4.0/ https://creativecommons.org/licenses/by-nc-nd/4.0/ http://publicationethics.org/ introduction experimental results and discussion conclusion rev m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p1 article type: conf.-conference paper (casamansun2018) simulation and optimization of the nsic layer’s thickness in a nsic/si photovoltaic cell m. kabe (1), y. lare (1), l. ottaviani (2), m. pasquinelli (2), d. barakel (2), m. portail (3) (1) solar energy laboratory, university of lome, togo (2) im2np (umr cnrs 7334), aix-marseille university, france (3) crhea (research center of heteroepitaxy and its applications), nice, france corresponding author: danielkabe2@gmail.com received: 1st april 2019 / received in final form: 1st june 2019 / accepted: 3rd june 2019 abstract : simulations of the emitter layer in 3c-sic heterostructure solar cells were performed by means of scaps to model the optimal thickness and predict the influence on cell’s behaviour. then, the cells have been elaborated by chemical vapor deposition and characterized. the opto-electrical measurements showed an improvement of the absorption of photons in the short wavelengths thanks to the thin layer of the emitter, and the non-degradation in bulk of the base cell. on the front side, the using of ti/au contacts also leads to an improvement in the absorption of photons thanks to the low series resistance. keywords : sic thin layer, heterostructure, solar cell introduction silicon remains the most used material in photovoltaic field. however, its applications are limited in the visible photo-conversion range. thus, research is venturing into experimenting with wide band gap semiconductors such as silicon carbide in order to widen the spectral band from visible to ultraviolet, by using the polytype 3c of the silicon carbide (3c-sic). indeed, silicon carbide is a wide band gap semiconductor material with exceptional properties in terms of temperature resistance, and chemical stability. 3c silicon carbide, with 2.36 ev bandgap could be a potential candidate and also, this material has been extensively studied due to its potential applications in variety of fields (1). sic is known for its ability to resist to high radiation level (2), making it suitable to work in solar concentrators. 3c-sic/si heterojunctions have already been studied in the domain of power cite this article: m. kabe , y. lare, l. ottaviani, m. pasquinelli, d. barakel, m. portail, oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p2 diodes (3), as window layer or as emitter for photovoltaic cells in several configurations (4). the opportunity to make 3c-sic/si tandem cells has been studied theoretically (5) even if according to (6), a tandem cell formed of an sic cell superimposed on a silicon cell would hardly achieve the performance of a single silicon cell. the first step in order to realize 3c-sic/si tandem cells is to masterize the deposition of 3c-sic on si wafers. we carried out simulations first in order to optimize the emitter layer to have a better conversion of the photons in the field of ultra-violet, and to understand the degradation of the si bulk properties during the sic film deposition. then, characterizations were performed on cells developed by the crhea (center for research on heteroepitaxy and its applications). the present work presents the results. simulation results in order to predict the properties of the cells to be developed by crhea, we performed simulations using scaps software. scaps is a software for modeling solar cells based on cdte and cigs (7), developed by marc bulgerman of the department of electronics and information systems (elis), university of gent, in belgium. our simulations thus consisted in the optimization of the emitter layer of the heterojunction 3c-sic/si. we optimized also the influence of the diffusion length of the carriers in the bulk of si following the deposition temperature during growth of the sic/si deposition process by the cvd method. figure 1: influence of sic thickness on eqe figure 2: influence of the lifetime in the si bulk these simulations have shown, first the improvement of the spectral response in the short wavelengths, especially for an optimal thickness of the emitter of 0.2 μm. secondly, a degradation in the visible response for >600nm could be observed in the bulk of si during the growth of sic, similar results were obtained by touré et al (8). results and discussions samples 3c-sic, <100> oriented, epitaxial layers were grown on <100> oriented, 10 ohm.cm p-type silicon wafer by resistive heating hot wall chemical vapor deposition, under hydrogen flux (15sml). silane and propane gases were used as precursors, under 200 mbar of pressure (c/si ratio =1.1). nitrogen was used in order to produce an n-type doping. the growing has been realized in two steps, first a carburation step at 1100°c, then a growing step at 1350°c. this process has been described in (9). the nitrogen flux for the doping level was 50 sccm, producing an estimated doping level of 7-8* 1018 cm-3 and 1019 cm-3.the two highest doping levels have been controlled by ftir method (10). the thickness of the emitter is varied: 2 μm, 1 μm, 0,5 μm, and 0,2 μm. one wafer was doped at 1019cm-3. photovoltaic cells were then produced in three steps: (i) mesa-structures were realized by classical photolithography (size 1.98x2.43 mm), (ii) the ti/au front contacts were deposited followed by a subsequent annealing at 460°c, (iii) an al/au layer was deposited on the backside of the wafer, followed by an annealing at 460°c. some other cells were fabricated using ni/au as ohmic contacts on the front side. m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p3 current-voltage characteristics current-voltage measurements were performed using a keithley 236 source-measurement unit. the curves in the dark are fitted with a single diode model based on the series and the shunt resistances, the ideality factor and the saturation current. a solar simulator with an am 1.5 spectrum and an illumination power of 1000 w.m-2 allows measurements under light. . figure 3: current voltage characteristics the parameters of the cells are presented in table 1. table 2 shows the previous results obtained by moussa and al, with diodes based on 2 um sic emitters and distinct doping levels (from 4.1017 cm-3 to 3.1019 cm-3) and ni/au layer as ohmic contact on front side (8). table 1: parameters of the new diodes emitter layer voc (mv) jcc(ma.cm-2) ff(%) η (%) rs(ω) rsh(ω) 0,2 μm (7.1018 cm-3) 220 ± 8 23,66 ± 0,56 0,502 ± 0,062 2,8 ± 0,4 27,625 ± 7,06 1247,83 ± 202,77 0,5 μm (7.1018 cm-3) 245±1 21,62 ± 0,12 0,58 ± 0,039 3,1± 0,12 20 ± 10,42 2906,53 ± 1675,86 1 μm (7.1018 cm-3) 260 ± 7,5 16,27 ± 0,52 0,62 ± 0,01 2,63 ± 0,13 12,31 ± 0,126 4359,42 ± 1175,82 2 μm (7.1018 cm-3) 260 ± 3,8 18,49 ± 0,12 0,52 ± 0,012 2,5 ± 0,12 56,88 ± 18,93 1194,27 ± 399,065 n+, 2 μm (1,5.1019 cm-3) 270± 1 16,66± 1,04 0,5 ± 0,01 2,37 ± 0,12 75,5 ± 8,74 1784,7 ± 136,6 m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p4 table 2 : parameters of the former diodes (8) emitter ( 2 um) doping level voc (mv) isc (ma/cm-2) fill factor efficiency % rs(ω.cm2) rsh(ω.cm2) 4.0e+17 90 12.5 0.37 0.42 0.48 559 2.0e+18 103 14.7 0.41 0.62 0.27 769 7.0e+18 110 15.3 0.42 0.70 0.26 780 3.0e+19 108 14.7 0.44 0.67 0.34 690 one wafer with 2 μm sic layer and a specific doping value of 1019 cm-3 was also developed by crhea. it can be noted that all the parameters of the cells with thicknesses lower than 2 μm are better, since the average quantum efficiency reaches 3%. in addition the highest photocurrent of the order of 24 ma.cm-2, is related to the lowest thickness of the emitter layer (0,2 μm). the metallization of the front contact using ti/au rather than ni/au leads to two phenomena: the reduction of rs and increasing of rsh on one hand, the improvement of voc on the other hand. nevertheless, the voc remains weak, indicating that the recombinations at the interfaces are not negligible. external quantum efficiency the benchmark of quantum efficiency, is based on a xenon uv-extended arc lamp, able to emit light from 200 to 1180 nm wavelengths, a monochromator, a chopper and a lockin amplifier. the illumination power ranges from 80 nw cm-2 at 200 nm to 10 μw cm-2 from 400 to 1180 nm. the setup was calibrated using a hamamatsu s1227 uv-extended photodiode. samples lay on gold covered copper plate. figure 4: external quantum efficiency of the 3c-sic/si as it can be seen on the graphs, the response is better in the ultraviolet between 200-400 nm for smaller emitter thickness. moreover, in the higher wavelength range (l> 600 nm), an improvement in the response of the new cells compared to the former one diode is observed. this shows that the growth of sic/si has been improved since there is less degradation in the si bulk. in addition, the metallization using ti/au, for the front contact, has made it possible to increase the performances in the cell’s efficiency according to the table 1. conclusion in order to improve the conversion efficiency of solar cells based on silicon carbide, a simple heterostructure has been studied. simulations were performed, and then characterizations measured. the conclusion of this study shows that we obtain an improvement of the spectral response in the short wavelength domain thanks to the thinner layer of the emitter, then an improvement of the growth due to the non-degradation of electronic bulk properties in si for wavelengths greater than 600 nm. the perspective of our work should consist of studying sic-3c/si tandem cells in order to better obtain a photovoltaic conversion of these cells in the short wavelengths. aknowledgements: the authors thanks scac-togo (cultural cooperation service of the embassy of france in togo) and crhea for supporting this work. m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p5 complementary informations on authors: kabe: danielkabe2@gmail.com lare: yenlare@yahoo.fr, lare yendoubé researchgate.net ottaviani: laurent.ottaviani@univ-amu.fr, laurent ottaviani researchgate.net pasquinelli: marcel.pasquinelli@univ-amu.fr barakel: damien.barakel@univ-amu.fr portail: marc.portail@crhea.cnrs.fr references 1. kefif k, bouizem y, belfedal a, sib jd, benlakehal d, chahed l. hydrogen related crystallization in silicon carbide thin films. optik. 2018;154:459–466. 2. sprouster dj, koyanagi t, dooryhee e, ghose sk, katoh y, ecker le. reprint of: microstructural evolution of neutron irradiated 3c-sic. scr mater. 15 janv 2018;143:176‑80. 3. chung gs, kim ks, yakuphanoglu f. electrical characterization of au/3c-sic/n-si/al schottky junction. j alloys compd. oct 2010;507(2):508‑12. 4. tanner p, dimitrijev s, harrison hb. current mechanisms in n-sic/p-si heterojunctions. in: 2008 conference on optoelectronic and microelectronic materials and devices. ieee; 2008. p. 41–43. 5. heidarzadeh h, baghban h, rasooli h, dolatyari m, rostami a. a new proposal for si tandem solar cell: significant efficiency enhancement in 3c–sic/si. optik. 1 févr 2014;125(3):1292‑6. 6. richards bs, brown as, trupke t, corkish rp, green ma. β-sic–based photovoltaic and optical devices. in: proceedings of anzses conference. 2002. 7. burgelman m, verschraegen j, degrave s, nollet p. modeling thin-film pv devices. prog photovolt res appl. 2004;12(2‑3):143–153. 8. toure m, berenguier b, ottaviani l, pasquinelli m, palais o, di lauro p, et al. new 3c silicon carbide on silicon heterojunction solar cells for uv collection enhancement. mrs online proc libr arch. 2014;1693. 9. zielinski m, portail m, chassagne t, juillaguet s, peyre h. nitrogen doping of 3c-sic thin films grown by cvd in a resistively heated horizontal hot-wall reactor. j cryst growth. 2008;310(13):3174–3182. 10. portail m, zielinski m, chassagne t, chauveau h, roy s, de mierry p. highly sensitive determination of n+ doping level in 3c–sic and gan epilayers by fourier transform infrared spectroscopy. mater sci eng b. 2009;165(1‑2):42–46. mailto:danielkabe2@gmail.com mailto:yenlare@yahoo.fr mailto:laurent.ottaviani@univ-amu.fr mailto:marcel.pasquinelli@univ-amu.fr mailto:damien.barakel@univ-amu.fr m. kabe and al. / simulation and optimization of the nsic layer in a nsic/si photovoltaic cell oaj materials and devices, vol 4 (1), 3103 (2019) – doi: 10.23647/ca.md20193103 p6 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev m.boutahir et al – identification of monoand fewlayer graphene: raman study oaj materials and devices, vol 3, #1, 0503 (2018) – doi: 10.23647/ca.md20180503 article type: a-regular research paper(ispds2) identification of monoand fewlayer graphene: raman study m. boutahir*, ah. rahmani, h. chadli, a. rahmani advanced material and applications laboratory (lem2a), university moulay ismail, fsmestm, bp 11201, zitoune, 50000 meknes, morocco. *corresponding author : mourad.boutahir@gmail.com received: 21 janvier 2018 / received in final form: 05 mars 2018 / accepted: 05 mars 2018 abstract : in this theoretical work, the raman spectra were analyzed by considering the origin of the g peak, its shape, position and relative intensity as a function of the number of graphene layers. by using the spectral moment’s method, the raman spectra of mono, bi and few-layers of graphene are calculated and a good agreement was found with group theory concerning the number of the raman-active modes and the raman measurements. our results provide a raman analysis to evaluate the number of layers in multilayer graphene. keywords : raman spectroscopy, graphene, graphite introduction since its discovery, graphene has attracted considerable interest due to some of its extraordinary properties [1, 2]. graphene can be synthetized using micromechanical cleavage of graphite [1, 2], epitaxial growth [3, 4], chemical vapour deposition [4, 5] or to be appealing, a characterization tool must be nondestructive, fast and give the maximum structural and electronic information. raman spectroscopy can fulfill these requirements. raman spectroscopy has thus become a standard characterization tool in the fast growing field of graphene studies. the difficult point in raman measurements of graphene is spectral interpretation. the raman spectra of all carbon systems show only a few prominent features. the spectra appear deceivingly simple: just a couple of very intense bands in the 1000-2000 cm−1 spectral range and some other bands at 2500-2800 cm−1. however, the accurate analysis of their shape, intensity and positions allow discriminating between hard amorphous carbon or metallic and semiconductor nanotubes. this has resulted in an enormous amount of work on the vibrational spectroscopy of graphene [7, 8, 9, 10] and also renewed the interest in its vibrational properties. the relation of phonon dispersion and the vibrational density of states (vdos) are still an open issue in the field, as it can be ascertained from several publications. gruneis et al.[11] parameterized the popular 4th-nearestneighbor force constant (4nnfc) approach [7]. dubay and kresse [12] performed calculations using density-functional theory (dft) within the local-density approximation (lda) for the exchange correlation function. in this work, using the spectral moments method (smm) [14, 15, 16, 17], and in the framework of the bond-polarization theory, the polarized raman spectra of mono-, biand tri-layer graphene, were calculated. the dependence of the raman active modes on the number of sheets was investigated. the results of calculations were compared with experimental raman data. models and methods most models used to describe the phonon bands, the valence force field (vff) method, and the force constant model (fcm). the latter has the lowest computation time requirements. in the fcm model, the dynamics of atoms are simply described by a few force springs connecting an atom to its surroundings up to a given number of neighbours. in contrast, the vff method is based on the evaluation of the force constants, which requires longer computational times. fcm uses a small set of empirical measurements. despite its simplicity, it can provide accurate and robust tools to investigate thermal properties of crystals and m.boutahir et al – identification of monoand fewlayer graphene: raman study oaj materials and devices, vol 3, #1, 0503 (2018) – doi: 10.23647/ca.md20180503 in particular graphene nanostructures. the fcm employed model involves a fourth nearest neighbor approximation. this model was previously used by our group to study the nonresonant raman spectra of (single walled carbon nanotubes (swnts), double walled carbon nanotubes (dwnts), dimers of two swnts ans oligomers encapsuled in graphene (pt@g). [18, 19, 20, 21, 22, 23, 22]. we also performed calculations of the potential reliefs of interlayer interaction energy in bi-layer and tri-layer graphene, as well as in graphite using the lennard-jones potential. v(r) = 4ε[(σ/r)12 –(σ/r)6] (1) the values of lennard-jones parameters are ε = 2.964 and σ = 3.407. note that the lennard-jones potential was successfully used to describe the van der waals energy in graphite-based systems [24]. the raman efficiency of modes was calculated according to the nonresonant raman scattering approach by using the bond-polarizability (bp) model [25, 26, 27]. in this model, the polarization is only modulated by the nearest-neighbor bonds and the components of the induced polarizability tensor [26, 27]. results and discussions the calculations were first performed on an infinite sheet of graphene which was obtained by applying periodic conditions on the unit cells of the graphene. figure 1 shows the calculated zz polarized raman spectra of infinite graphene. the symmetries of the raman active modes were directly derived from the polarized zz in the spectra. indeed, it was established that the a1g raman mode of graphene is active in the zz polarization. the number of calculated active modes is in agreement with group theory calculations [28]. the zz polarized spectrum is dominated by a strong a1g raman active mode calculated in the tangential mode (tm) region calculated around 1588 cm−1. the raman spectrum of graphene bilayer (2-lg) was also calculated with bernal ab layer stacking. the g-band is calculated to occur 1588.4 cm−1 and corresponds to the atomic motion of nearest neighbor carbon atoms moving against each other within the plane and in phase between the two layers (figure 2-d). figure1: raman spectra of graphene mono-layer. table 1: the raman active modes in 1-lg, 2-lg and 3-lg three other raman active modes are found, one located at 58cm−1 and the two others at 89 cm−1 and 866cm−1. figure 2 shows the eigenvector displacements of the raman active modes in a graphene bi-layer. the van der waals interactions lead to new raman active modes associated to single-layer graphene. note that the atomic motion of the mode located at 89 cm−1 (figure 5-a) is similar to that of the counter phase radial breathing mode of double walled carbon nanotubes [32]. figure2: the atomic motions of raman active modes in graphene bi-layer. for the trilayer graphene (3-lg), the g-band mode is calculated at 1589 cm−1. as in the case of bi-layer graphene, additional raman active modes are also calculated in 3-lg. the atomic motion of these raman active modes is shown in figure 3. in table 1, we present calculated raman active mode frequencies in 1-lg, 2-lg and 3-lg systems. we note that our calculated 1-lg 1588cm 1 2-lg 58cm 1 89cm 1 866cm 1 1588.4cm 1 3-lg 42cm 1 64cm 1 74cm 1 112cm 1 866cm 1 1588.4cm 1 1589.06cm 1 m.boutahir et al – identification of monoand fewlayer graphene: raman study oaj materials and devices, vol 3, #1, 0503 (2018) – doi: 10.23647/ca.md20180503 frequencies of the raman-active modes are in good agreement with group theory predictions [28]. figure3: the atomic motions of raman active modes in graphene tri-layer. finally, we calculate the zz raman spectrum of graphite. figure 4 presents the g-bands of the raman spectrum of mono-layer, bi-layer, tri-layer graphene and graphite. we found that the a1g mode up-shifted with increasing number of layers. the g peak also showed a small shift upon increasing the number of layers. for instance, the g band frequency ω(g) of single-layer graphene is 1588cm−1, that of bi-layer graphene is 1588.4cm−1 and for trilayer is 1589.4cm−1. figure4: raman spectra of graphene mono-, biand tri-layer and graphite. conclusion in this paper, the evolution of calculated raman active modes as a function of the number of graphene layers are analyzed and general good agreement is found between our calculations and group theory. the high frequency regions of the raman spectra of graphene multilayer are characterized by a splitting of the a1g mode of graphene mono-layer. the additionnal modes that originate from the monolayers a1g modes are strongly coupled through the van der waals interlayer interactions. these predictions are useful for understanding the experimental raman spectra of multilayer graphene. references [1] k. novoselov, d. jiang, f. schedin, t. booth, v. khotkevich, s. morozov, a. geim, twodimensional atomic crystals, proceedings of the national academy of sciences of the united states of america 102 (30) (2005) 10451–10453. 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[34] m. dresselhaus, g. dresselhaus, a. jorio, a. souza filho, r. saito, raman spectroscopy on isolated single wall carbon nanotubes, carbon 40 (12) (2002) 2043–2061. m.boutahir et al – identification of monoand fewlayer graphene: raman study oaj materials and devices, vol 3, #1, 0503 (2018) – doi: 10.23647/ca.md20180503 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate sp ecific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by sc ientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com introduction most models used to describe the phonon bands, the valence force field (vff) method, and the force constant model (fcm). the latter has the lowest computation time requirements. in the fcm model, the dynamics of atoms are simply described by a few forc... nearest neighbor approximation. this model was previously used by our group to study the nonresonant raman spectra of (single walled carbon nanotubes (swnts), double walled carbon nanotubes (dwnts), dimers of two swnts ans oligomers encapsuled in grap... we also performed calculations of the potential reliefs of interlayer interaction energy in bi-layer and tri-layer graphene, as well as in graphite using the lennard-jones potential. conclusion copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. rev hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 1 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 article type: conf.invited conference paper (ispds2) carbon nanotubes functionalized with copper hexacyanoferrate nanoparticles for a selective extraction of cesium from liquid waste h. draouil (1,2,3,4) l. alvarez (4), j. causse (1), v . flaud (5), m.a. zaïbi (3), j.l. bantignies (4), m. oueslati (2) and j. cambedouzou (1) (1) institut de chimie séparative de marcoule, cea-cnrs-enscm-um, 30207 bagnols sur cèze, france (2) unité de nanomatériaux et photonique, université el manar, faculté des sciences de tunis, département de physique, 2092 el manar, tunis tunisia (3) ecole nationale supérieure d'ingénieurs de tunis, université de tunis, 1008 tunis, tunisia (4) laboratoire charles coulomb, cnrs, université de montpellier, f-34095 montpellier, france (5) institut charles gerhardt montpellier, université de montpellier, f-34095 montpellier, france corresponding author : laurent.alvarez@umontpellier.fr received: 03 may 2018 / received in final form: 01 july 2018 / accepted/: 02 july 2018 abstract : single-walled carbon nanotubes are functionalized with copper hexacyanoferrate nanoparticles for the liquid-solid extraction of cesium from liquid waste and contaminated water. the functionalization process is followed mainly by x-ray photoemission spectroscopy. indeed, determining the chemical environment around carbon or nitrogen atoms allows to evidence the formation of covalent bounding. in addition, the signatures of iron and copper ions give information on the effective growth of hexacyanoferrate nanoparticles. furthermore, the cesium sorption mechanism is investigated by comparing the peak intensities associated to the response of potassium and cesium ions. finally, based on the liquid chromatography analyzes, the sorption of cesium with the functionalized carbon supports is studied. the main results of this work are the demonstration of both a good selectivity of cesium trapping and a high sorption capacity by hybrid single-walled carbon nanotubes. keywords : liquid waste, nanotubes, hexacyanoferrate, functionalization, cesium trapping http://www.icgm.fr/ hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 2 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 introduction decontamination of radioactive water, whether from nuclear effluents from industry and research, or from nuclear accidents, is a major challenge to limit releases to the environment [1-2]. in particular, radioactive iodine (i-131) and cesium (cs-137) are particularly toxic and found in large quantities in polluted waters [3-4]. it therefore becomes urgent to provide sustainable solutions for the treatment of contaminated water, in particular with radioactive cesium ions (cs+). several materials have been proposed for this application, but the frequent coexistence of other ions whose concentration is higher than cs+ limits the efficiency of decontamination. thus, the use of selective sorbents is absolutely mandatory. prussian blue analogues have been shown to be particularly relevant for this application. in particular, they are useful for the treatment of contaminated natural water or diluted wastes with typical cs+ concentrations ranging from 10-9 g l_1 for contaminated water and up to 10-4 g l-1 for low to intermediate level wastes [4]. however, once hydrated, this material forms sludge that is difficult to reprocess afterwards, which makes difficult its utilization [5-6]. then, prussian blue grafting tests on mesoporous silica have been carried out. this allows a continuous flowing on solid support, affording the treatment of large quantities of water. however this latter material exhibits a low sorption rate and has a weakness inherent in its chemical composition towards aggressive media such as basic medium [7-8]. single walled-carbon nanotubes are solid materials displaying a high specific area, good mechanical and chemical resistances. however, pristine nanotubes (including multiwalled) exhibit a poor sorption capacity [9-10]. outer surface functionalization with dimethyl-acetylene dicarboxylate increase significantly the whole sorption capacity but without any selectivity [11]. consequently, in order to overcome all these drawbacks, this work is focused on the hexacyanoferrate nanoparticles (hcf, which are prussian blue analogs) grafting onto single-walled carbon nanotubes (nt) in order to elaborate new hybrid system (hfc-nt) for a selective cesium extraction with high capacity. experimental section nanotubes are purchased from carbon solution, inc.(reference p2-swcnts, of diameter 1.4±0,2nm). propargylamine (prg) and copper-hexacyanoferrate precusors are purchased from sigma-aldrich (99%) and used without further purification. 1functionalization with propargylamine a mixture containing 60mg of nt with 25ml of pure prg is prepared. the mixture is submitted to ultrasonication for 15 min following the procedure described elsewhere [10]. the mixture is then transferred into a teflon-lined steel autoclave and heated to 100°c during 24 hours. this blend is filtered and then washed with acetone in order to remove all prg molecules in excess. 2cu-hfc-nps growth this step is based on two reactions, following the procedure described in a previous work [11]. the first step features the addition of a copper nitrate (cu(no3)2) solution in order to attach a cu atom to the prg. this cu atom serves as a nucleation center for the further growth of the cuhcf-np. the resulting system is carefully rinsed with acetone. the second step consists in the addition of a potassium ferrocyanide (k4fe(cn)6) solution aimed at initiating the growth of the first cell of the cuhcf-np. both solutions are prepared with a concentration of 10-2 m. this process is cycled three to four times. 4characterization x-ray photoelectron spectroscopy (xps) is performed on an escalab 250 (thermo electron). the x-ray excitation is provided by a monochromatic al ka (1486.6 ev) source. all xps spectra are treated using the avantage software. liquid phase ionic chromatography (lpic) is performed using an ics-5000-dionex instrument with 4 scans for each sample. 5cesium sorption cs+ sorption measurements are carried out in batch mode on both pristine nt and on hcf-nt according to the following protocol: 10 mg of a buckypaper of carbon nanotubes are stirred with 20 ml of cesium nitrate solution using different concentrations (0.1 mm, 0.5 mm, 2 mm, 4 mm and 8 mm) for 24 h. carbon nanotubes are recovered by filtration using filter paper with particle retention between 5 and 13 mm and thoroughly washed using milli-q water. the solid samples are then dried for further analyses, while the liquid phase is analyzed by lpic. functionalization processes the different functionalization steps are investigated by xps. figure 1 displays the low resolution spectra for pristine nanotube (black curve, 1), prg grafted on nt (red curve, 2) and hcf-nt (blue curve, 3). for pristine nt, two chemical elements are identified: carbon atoms (peak around 285 ev) of the nanotubes and some oxygen (530 ev) probably covalently bond to the carbon network, giving rise to defects [12]. after prg (h-c≡c-ch2-nh2) grafting, a new peak at around 400 ev is observed, featuring the presence of nitrogen [13]. after hcf nanoparticle growth k2cufe(cn)6, new and expected peaks assigned to potassium (295 ev), iron (730 ev) and copper (932 ev) appear in the photoemission spectrum (fig.1.c) [14,15]. to better investigate the functionalization process and the chemical bounding formed, high resolution measurements are required. figure 2 displays the deconvoluted c1s peak at each hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 3 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 functionalization step. comparing the c1s peaks of pristine nts (fig.2.a) with prg grafted nt samples (fig.2.c), we clearly see changes around 286 ev (linked to co or cn bonds [12]), especially in terms of full width at half maximum (fwhm) (1ev for pristine nt and 1.3 ev for prg-nt). 900 800 700 600 500 400 300 200 k2s cu2p fe2p c1s o1s n1s in te n s it y ( a .u ) binding energy (ev) (3) (2) (1) pristine nt prg-nt hcf-nt figure 1: xps survey at each grafting step quantitatively, this contribution has significantly increased (from 4% up to ~ 14%). this evolution is concomitant with a decrease of the sp2 peak at 284.4 ev and an increase of the sp3 contribution at 285 ev. indeed, nt functionalization with prg leads to a change of sp2 orbitals into sp3 orbitals in order to ensure a covalent bonding between the carbon atoms of the nt and prg. in addition, the c-n bondings of the prg molecules increase significantly the peak intensity at around 286 ev which can arise either from c-o or c-n (and even triple bonding between carbon atoms) [12]. for nt functionalized with hcf (fig. 2.c), the signal around 286 ev (relative to c-n, c-o or c≡c bonds) decreases with respect to the prg-nt (from ~ 14% to 10.6%). one possible assumption is to consider that the washing step after hcf functionalizationthat is to say after the growth of hexacyanoferrate nanoparticles, prg-cuhcf particles not covalently bound to nt could have been removed, which induces a decrasing of c≡c bond signal. typical binding energy for nitrogen atoms in cyanide groups of hexacyanoferrate molecules is between 397.5 ev and 400 ev [15]. figure 3 shows the high resolution n1s spectra of prg-nt (fig. 3.a) and hcf-nt (fig. 3.b) samples. the most important signal at around 399 ev is due to c-n bonding from the prg molecules whereas the peaks at around 400 et 402 ev, assigned to n-c=o and nitrogen ions correspond to defects and contamination after the different chemical treatments. following the growth of hcf nanoparticles, a new peak appears around 397.6 ev, assigned to the c≡n bonds expected in hcf nanoparticles [15]. figures 4 and 5 display peaks at 708.3 and 932.7 ev corresponding to fe2p and cu2p binding energies [14-15]. the fe2p energy is in good agreement with the formation of fe2+, as expected in case of copper hcf. biesinger et al [14] analyzed different types of copper samples such as cu and cu2o, and found the same cu2p decomposition profile as in our sample. figure 2: high resolution c1s x-ray photoemission spectra after each grafting step they attributed the lower energy bond to cu+ and the higher to cu2+. in these compounds, cu2+ is generally expected [15-16], but a reversible reduction reaction in cu+ is sometimes reported [17]. it is worth mentioning that the intensity ration between 288 286 284 282 c) binding energy (ev) hcf-nt c-o c-n c c c=c c-c c-h pristine nt a) b) in te n si ty ( a .u .) prg_nt hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 4 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 the two peaks depend on the area investigated. figure 3: high resolution n1s x-ray photoemission spectra after each grafting step 712 710 708 706 704 in te n si ty ( a .u .) binding energy (ev) fe2p 3/2 figure 4: high resolution fe2p x-ray photoemission spectrum of hcf-nt it should be noted that the ratio cu+ / cu2+ strongly depends on the zone studied in our samples. as we do not believe in the heterogeneity of our samples, we assume a reduction under xrays, leading to a transformation from cu2+ to cu+. anyway, all the results are consistent with an efficient process of functionalization. 940 938 936 934 932 930 928 cu 2+ in te n si ty ( a .u .) binding energy (ev) cu +cu2p3 figure 5: high resolution cu2p x-ray photoemission spectrum of hcf-nt. cesium sorption capacity the cs+ sorption measurements are carried out on both pristine and functionalized nanotubes with hfc. figure 6: xps survey for pristine hcf-nt (a) and exposed to solutions containing different cs concentrations (b) 0.1 mm, (c) 2 mm, (d) 4mm) the xps surveys of nt functionalized by hfc before and after exposure to csno3 solutions of different cs concentrations 404 403 402 401 400 399 398 397 396 hcf-nt i n te n s it y ( a .u .) binding energy (ev) b) prg_nt a) nh 2 + n-c=o c-nh 2 c = n 750 740 730 720 710 300 290 280 270 fe2pcs3d fe2p binding energy (ev) cs3d c1s in te n s it y ( a . u .) k2p (d) (c) (b) (a) + hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 5 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 (0.1mm, 2mm and 4mm) are presented in figure 6. the presence of cs is detected in two positions of binding energy: ~ 738 ev and ~ 724 ev [18] (fig. b, c and d). the intensity of these peaks increases with the concentration of csno3. concomitantly, the disappearance of the signal from potassium is observed. this result confirms an exchange between cs+ and k+ ions within the hfc cubic structure. finally, we observe cs+ xps signal that increases very slowly, suggesting that sites available for cs+ sorption are rapidly saturated. 0 2 4 6 8 0 50 100 150 200 250  a d s( m g /g ) cs concentration (mm) in csno 3 solution figure 7: sorption isotherm of cs+ on nt and hcf-nt in order to go further in understanding the sorption mechanism, we also conducted lpic analyzes of the cesium solution before and after exposure to hfc-nt. the cs+ sorption isotherm by pristine and functionalized nanotubes with hfc are shown in figure 7. both nt materials show increasing sorption capacity with increasing concentration of cs+, although it is still lower for pristine nt with respect to hcf-nt (150 mg.g1 and 230 mg.g-1 respectively). one way to evaluate the proportion of cs+ ions complexed in hfc nanoparticles (i.e. selectively trapped) is to subtract the sorption isotherm from the pristine nt to that of hfc. thus, for cs concentration of 4mm, the selective sorption of cs reaches a value of about 80 mg.g-1 (about a third of the total sorption of the hfc-nt). this value compares rather well with other materials generally used for cs extraction. conclusions hexacyanoferrate nanoparticules (prussian blue analogs) have been successfully grafted at the outer surface of carbón nanotubes using propargylamine molecules as intermediate species. the different steps of the whole fuunctionalization process have been investigated mainly by means of x-ray photoemission spectroscopy. the study of the different chemical environments around the carbón and nitrogen atoms allowed to evidence the formation of the expected covalent bondings at each step of the process. the nature of iron and copper ionic species confirms the growth of copper hexacyanoferrate nanoparticules. cesium sorption capacity has been studied by liquid phase ionic chromatography. the reached value of 80 mg/g is particularly encouraging. finally, ion exchange mechanism between potassium and cesium species has been confirmed by photoemission measurements. references 1. w.-q. shi, l.-y. yuan, z.-j. li, j.-h. lan, y.-l. zhao and z.-f. chai, radiochimica. acta, vol.100, p 727 (2012) 2. p. p. povinec, m. aoyama, d. biddulph et al, biogeosciences, vol.10, p 5481, (2013) 3. d. yang, s. sarina, h. zhu, h. liu, z. zheng, m. xie, s.v. smith and s. komarneni, angewandte chemie international 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hajer draouil et al, carbon nanotubes functionalized with copper hexacyanoferrate 7 oaj materials and devices, vol 3 #2, 0407 (2018) – doi: 10.23647/ca.md20180407 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p1 article type: t-technical paper modelling and simulation of an automatic solar module characteristics data acquisition system e.akoro, g. j. p. tevi, m. e. faye, m. sene and a. s. maiga laboratoire d'electronique, informatique, télécommunication et energies renouvelables, ufr des sciences appliquées et des technologies, université gaston berger-saint-louis, sénégal corresponding author: justinakoro@gmail.com received: 20 november 2018 / received in final form: 15 february 2019 / accepted: 16 february 2019 abstract: this paper is devoted to the design and simulation of an automatic data acquisition system of solar module characteristics. the system is essentially composed of three parts. the first part is devoted to the acquisition of the electrical parameters of the solar module (current, voltage and power) in automatic ways using an automatic variable load. the second part is focused on devices which measure the ambient temperature and solar irradiation. in the last part, we study the design of an acquisition interface and a database for data saving. the results of simulations validate the correct operation of the measuring bench. keywords: pv module, automatically variable load, acquisition interface, database introduction the performance of photovoltaic modules is based on a number of significant parameters extracted from the characteristic i-v such as the short-circuit current isc, the open-circuit voltage voc, the current impp, and the voltage vmpp at the point of maximum power, the form factor ff, the series resistance rs and the shunt resistance rsh [1]. on the other hand, the atmospheric parameters in which the solar module must operate are generally not taken into account by the manufacturers. these climatic parameters often change abruptly, which can affect the efficiency of photovoltaic systems [2]. thus, to study their influence on the operation of the solar module, it would be interesting to have a database in which various data (pv current, voltage and power, temperature and irradiance) will be permanently recorded for their exploitation. this work consists in designing a device for automatic acquisition of the characteristics of solar modules and climatic parameters. to have the characteristic of the current (i) as a function of the voltage (v), we opted for an automatic variation of the load at the terminals of the pv module which is an 8-bit r / 2r digitalto-analog converter (dac). the climatic parameters taken into cite this article: e.akoro, g. j. p. tevi, m. e. faye, m. sene and a. s. maiga, oaj materials and devices, vol 4 (1), 1602 (2019) – doi: 10.23647/ca.md20191602 e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p2 account are the temperature and solar irradiation. the acquisition of all these parameters is done in automatic ways controlled by a microcontroller which name is pic16f877. the overall scheme of the simulated electronic card is design under the isis proteus software. synoptic diagram of the system as we pointed out in the introduction, the purpose of this work is to have a database in which data will be permanently recorded. this is the result of an automatic device set to acquire all these data. to realize this automatic system of acquisition, it is necessary to involve a certain number of elements: the solar module: which is a technological device intended to convert solar radiation into electrical energy. automatically variable load: current and voltage values measurement requires a variable load that will vary the voltage and the current at the terminals of the solar module, which will be used for plots of different characteristic curves. sensors: to measure the climatic parameters. acquisition card: responsible for collecting all these parameters that we want to record in the database. computer: after acquisition and appropriate conversions of data by the acquisition card, it is necessary to route them to a computer (computer) via a rs232 serial link for operation and possibly storage. the figure below illustrates the synoptic diagram of the system figure 1: synoptic diagram of the automatic acquisition system effects of climatic parameters on solar cells climatic parameters such as temperature and irradiation have a considerable influence on the characteristics of a solar module. increasing the temperature with fixed irradiation results in a net decrease of the open circuit voltage (voc) and an increase of the short circuit current (icc), as well as a decrease in the maximum power (pmax). similarly, when the irradiation varies for a temperature kept constant at 25 ° c, the short-circuit current (icc) varies due to the irradiation, whereas the open-circuit voltage (vco) varies very little [3]. measurement of electrical parameters equivalent circuit of solar module in the absence of a solar module model under the isis software that we used, we designed a simpler diode module model by paralleling a current and voltage generator. using a voltmeter and an ammeter, we made sure to obtain the critical values of our photovoltaic generator, namely, the maximum short-circuit current icc and the maximum open-circuit voltage voc. e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p3 figure 2: one-diode module model our study will focus on the monocrystalline sp75 with the following features: table 1: characteristics of the single-crystal sp75 panel automatically variable load for the automatically variable load, we use an 8-bit r / 2r (figure 3) digital-to-analog converter (dac) developed in [4]. it is a resistance network composed of only two values, r and 2r. the role of this load is to automatically vary the impedance at the terminals of the photovoltaic generator (gpv) to allow measurement of the current and voltage of the module. with this load r / 2r network, we can obtain 256 measurements of current-voltage torque (i-v). to control this digital resistor, we will need a sequencer, an automaton that is responsible for generating the control signals needed to operate and control the units involved in the execution of a given instruction. we use pic microprocessor as a sequencer, very popular specialized and accessible on the local market. the binary signals generated by a sequencer and applied to the transistors set the value of the resistor. the bipolar transistor is chosen as an electronic switch due to the low power loss compared to others types of transistors. figure 3: programmable control of the automatically variable load. voltage measure maximum power pmax 150 w optimum maximum tension vopt 17.6 v optimum maximum current iopt 9.19 a open circuit voltage vco 21.6 v short circuit current icc 10.2 a e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p4 we use a voltage divider bridge to measure the voltage. it is made by two resistors placed between the output of the solar panels and the ground. figure 4 allows to go from the voltage vpv at the outputs of the photovoltaic module to the voltage vpm range in 0 and 5 volts, to be then measured by the microcontroller. the relation expressing the voltage vpv as a function vpm is: 𝑉𝑝𝑚 = 𝑉𝑝𝑣.𝑅11 𝑅11+𝑅12 (1) figure 4: diagram of voltage measurement current measurement for current measurement (figure 5) the simplest method is to measure the voltage across a resistor to derive the current flowing through it. this method is not expensive compared to other techniques and provides good accuracy in low frequency. the measuring resistor and the circuit associated with it must have good temperature stability and good accuracy [5]. as for the voltage measurement circuit, this voltage obtained at the output of this amplifier must be between 0 and 5 volts and thus be measurable by the microcontroller. the ipv current of the photovoltaic generator is: ipv = vshunt rshunt (2) the relationship between the measured voltage (vm) and the shunt voltage (vshunt) is: 𝑉𝑚 = − 𝑅2 𝑅1 . 𝑉𝑠ℎ𝑢𝑛𝑡 (3) r1 and r2 must be chosen so that vm is between 0 and 5 v. figure 5: current measurement circuit measurement of climatic parameters as described above the characteristics of a photovoltaic panel are influenced by several climatic parameters that must be controlled, namely the temperature of the panel and the solar irradiance. if one or the other of these quantities varies too much during the successive measurements corresponding to a curve, then the results will not be relevant, hence the need to characterize these different parameters. temperature measurement we use the rtd pt100 temperature sensor described in [6] to measure the temperature. it is a resistance which value changes as a function of the evolution of the temperature (at 0 ° c the value of the resistor is 100 ohm). the theoretical value of the resistance for a pt100 probe is: rt = 100 (1 + 0,004) (4) with  the temperature. to adapt the signal from the platinum resistance to the microcontroller input, it is necessary to use a conditioner. the temperature measurement circuit is as follows: e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p5 + _  m r r r e r + _  rt générateur de courant +  u 2 r 1 r 2 aop 1 aop 2 aop 3 deuxième étage u 1 u 3 +15v r 4 r 3 r 5 r 6 troisième étage premier étage u p figure 6: conditioning circuit for the pt100 sensor the whole consists of a first current generator level is followed by a second amplifier level. the third level allows to obtain a linear response u3 = k.  the current generating circuit enables the platinum resistance to be fed with a current of constant intensity i = e r = 1 ma (5) the voltage across the platinum resistance is, therefore, an affine function of the temperature: 𝑈1 = 𝑎 + 𝑏 (6)  the second level amplifier allows to amplify the u2 voltage 1 1 2 2 r r 1 uu          (7)  the last level eliminates the constant term from the voltage divider (up) and adjusts the yield with resistor r4 to have a direct reading of the temperature: p 3 4 2 3 4 3 r r r r 1 uuu           (8) by choosing: e = 10 v; r = 10 k ; r1 = 1 k ; r2 = 10 k ; r3 = 10 k ; r5 = 3.3 k and playing on the result to be obtained which should be u3=0.05 so as to have 0°c u3=0v and at 100°c u3=5v, we get by calculation r4 = 103.636k and r6=286.96. operational amplifiers (tl081) are supplied with + 15v / 15v. the simulation of this conditional circuit gives the following results: table 2: simulation results of the conditioning circuit for the pt100 sensor solar irradiance measurement to measure the global solar radiation at the surface of the photovoltaic modules, we use the kipp & zonen cmp11 pyranometer, with a sensitivity of 8.44 μv/w.m. as the temperature, to adapt the output signal of the pyrometer to the input of the microcontroller, it is necessary to use a conditioner described in [7]. the irradiance measuring circuit is as follows: figure 7: conditioning circuit for the kipp & zonen cmp11 sensor the relations leading the operation of this circuit are given in the following: vem = gxve (9) 𝐺 = 1 + 49,4𝐾 𝑅𝐺 (10) ve = sxe (11) t (°c) rt(ω) u3(v) 0 100 0,09 10 104 0,58 50 120 2.53 100 140 4,97 first level second level third level e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p6 thus, the irradiance e is defined as a function of the output voltage of the amplifier by the following relation: 𝐸 = vem 8,44.10−6(1+ 49,4k rg ) (12) to test the operation of the conditioning circuit, the latter has been simulated with isis proteus. e (w/m2 ) 0 100 40 0 600 900 100 0 120 0 vem(v) 0 0.4 5 1.7 2.5 3 3.7 9 4.21 4.7 table 3: results of simulation of the conditioning circuit for kipp & zonen cmp11 design of the electronic card the electronic card which control the acquisition of the various parameters is captured and simulated under the isis proteus software. in addition to the sensors and the automatic variable load, the electronic card contains the following elements: microcontroller pic 16f877a, quartz oscillator delivering a periodic signal which runs the steps of the microcontroller program, the rs232 link used to transmit information from the microcontroller to the acquisition interface without using the synchronization clock. the figure below shows the simulated electronic card under isis: figure 8: simulation diagram of the electronic card e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p7 acquisition interface and recording of data the interface we designed is used to read the data received from the rs232 serial link. we used the visual studio express 2012 software developed by microsoft corporation. the read data are: temperature (°c), solar irradiance (w/m²), current (a), voltage (v) and power (w) of the photovoltaic module. when the electronic card is powered, just choose port 2, click the start button to start playback. after 256 read values the loop resumes. the end of the acquisition will be decided by the managers of the laboratory. the figure below shows the acquisition interface in operation: figure 9: the system of acquisition in full operation in order to better analyze the data read on the interface, a database is created for the recording. this database is nothing more than a file in which a line of data is written every second and recorded automatically. each line is associated with a date, the year, the month, the day, the hour, the minute and the second. the following figure shows the file containing the recorded data for a temperature of about 31 ° c and a solar irradiation of 1000 w / m². figure 10: data record file (temperature = 31 °and irradiance=1000 w/m2) conclusion the work presented in this article deals with the automatic acquisition of the characteristics of solar modules. as part of the optimization of photovoltaic installations, our main objective was to set up a system that would facilitate the acquisition of the different characteristics of solar modules and then to save them in a database. the results obtained are acceptable for the automatic acquisition of the characteristics of the solar modules. data acquisition can be performed for all variables in a time range as small as one second which allows controlling the operation of the photovoltaic generator in real time. e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p8 complementary informations on authors: edjadessamam akoro: justinakoro@gmail.com, https://www.researchgate.net/profile/edjadessamam_akoro jean g.p. tevi: tevi.gabriel-jean-philippe@ugb.edu.sn, https://www.researchgate.net/profile/tevi_gabriel_jean-philippe marie e.faye diagne: marie-emilienne.faye@ugb.edu.sn, https://www.researchgate.net/scientificcontributions/2146975088_marie_emilienne_faye moustapha sene: mstsene@yahoo.fr, https://www.researchgate.net/scientificcontributions/2146960350_moustapha_sene amadou s. maiga: amadouseidou.maiga@ugb.edu.sn,https://www.researchgate.net/profile/seidou_maiga_amadou references 1. e.durán, j.m. andújar; galán, m.sidrach-de-cardona, methodology and experimental system for measuring and displaying i-v characteristic curves of pv facilities. prog. photovolt. res. appl. 2009. 2. c.j. lohmeier (2011), highly efficient maximum power point tracking using a quasi-double-boost dc/dc converter for photovoltaic systems. university of nebraska – lincoln, electrical & computer engineering, department of computer engineering 3. fatou ndiaye, moustapha sene, modoubeye, amadou s. h. maiga, effects of climatic conditions on a polycrystalline photovoltaicmodule inniger. international letters of chemistry, physics and astronomy, issn: 2299-3843, vol. 55, pp 59-65 4. o.sow, d.diarisso, n.mbodji, m.diallo, a.diao, i.gaye,f.i.barro, g.sissoko (2016), experimental processus for acquisition automatic features of i-v properties and temperature of the solar panel by changing the operating point. circuits and systems, 7, 3984-4000. 5. l.yang, and a.yang, communication—on zero-resistance ammeter and zero-voltage ammeter.journal of the electrochemical society, 164 (13) c819-c821 (2017) 6. généralité sur les sondes pt100 [in line]. [viewed on june 12, 2019]. lipsakiss.free.fr/anal/ing2/cao_elec/projet/pt100.doc 7. a. triki, a. mahrane, a. guenounou et m. laghrouche, conception et simulation d’un banc de mesure de la caractéristique i v des modules photovoltaïques, revue des energies renouvelables vol. 17 n°1 (2014) 29 – 41 e.akoro et al -modelling and simulation of an automatic solar module characteristics data acquisition system oaj materials and devices, vol 4(1), 1602 (2019) – doi: 10.23647/ca.md20191602 p9 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! http://materialsanddevices.co-ac.com/ rev a.k. collado, g. hernández, v. morejón, f. coll, c. peniche encapsulation of a bioactive steroid in polymer matrix article type: a-regular research paper encapsulation of a bioactive steroid in a polymer matrix (micro-encapsulation of di-31 in chitosan by spray drying for various purposes) a.k. collado (1), g. hernández (2), v. morejón (2), f. coll (2), c. peniche (3) (1) biomaterials center, university of havana, cuba, akcollado@biomat.uh.cu (2) center for the study of natural products (cepn), university of havana, cuba giselle_hernandez@fq.uh.cu, vniebla@fq.uh.cu, fcoll@fq.uh.cu (3) faculty of chemistry, university of havana,cuba, peniche@fq.uh.cu corresponding author: akcollado@biomat.uh.cu received: 6 january 2017 / received in final form: 25 april 2017 / accepted: 15 may 2017 abstract: di-31 is a synthetic analog of brasinosteroids (abr), the active ingredient (pa) of biobras, a plant growth stimulant, which has shown positive impact on cuban agriculture, especially in rice cultivation. however, it has the drawback of having low solubility in water and being rapidly metabolized by the plants. an alternative to overcome these limitations is its micro-encapsulation in a polymer matrix. chitosan (chi) has been investigated as an excellent candidate for microencapsulation of di-31. chitosan (chi) is a natural polysaccharide obtained from chitin extracted from exoesqueleton of crustaceans, which increases resistance of the plants to the attack of pests and promotes the yield of the crops, also possesses excellent biocompatibility, biodegradability and mucoadhesivity, also inducing the defense of the plants against the attack of different pathogens. keywords: polymer matrix, chitosan, microparticles, spray drying, di-31 introduction the brasinoesteroids (br) are steroidal phytohormones with important regulatory functions in plants. these compounds determine, among other plant physiological processes, cell division and growth, seed germination, crop yield, response to different stress conditions (saline, water, thermal stress) and plant protection to different pests and diseases. the role of the same in germination of seeds and growth, in flowering, senescence, photosynthesis, chlorophyll content, plant vascular tissue differentiation and activity of some plant enzymes (carbonic anhydrase, nitrate reductase) has been extensively studied. several brasinoesteroids (br) and synthetic analogues of brasinosteroids (abr) have been used for the control of insects and pests that affect crops, due to their antiecdysteroid activity[1]. the synthetic analog of brasinosteroids, di31, synthesized at the center for natural product studies at the university of havana (cepn), is a commercial agrochemical widely used in many crops, being able to increase the yield of different crops between 5 and 30%. on the other hand, the low aqueous solubility thereof; as well as the need to carry out two or more applications of biobras (commercial agrochemical based on di-31) at different stages in the case of long cycle crops, limit the expression of their benefits in plants and make them more expensive. chitosan (chi) is a linear cationic polysaccharide composed essentially of 2-amino-2-deoxy-d-glucose units. this biopolymer is rarely found in nature and is mainly obtained by exhaustive deacetylation of chitin, which is the main constituent of fungal cell walls, insect cuticle and carapace of materials and devices, vol 2(1), 1505 (2017) – doi: 10.23647/ca.md20171505 mailto:akcollado@biomat.uh.cu mailto:akcollado@biomat.uh.cu mailto:peniche@fq.uh.cu mailto:fcoll@fq.uh.cu mailto:vniebla@fq.uh.cu mailto:giselle_hernandez@fq.uh.cu a.k. collado, g. hernández, v. morejón, f. coll, c. peniche encapsulation of a bioactive steroid in polymer matrix molluscs and crustaceans[2]. said polysaccharide is biocompatible, biodegradable, non-toxic and mucoadhesive; in addition its antifungal and antibacterial properties, antioxidants, hypocholestatic and coagulants make it very attractive for numerous applications in medicine and pharmacy. thus there are numerous reports and patents on the preparation of microparticles, microcapsules, hydrogels, nanoparticles, films and composites of chi and their derivatives for the controlled release of various drugs. on the other hand, chi can induce metabolic changes in plants, with an increase in crop yield, seed germination and resistance to pests[3]. in the bibliographic review carried out by the authors for the accomplishment of this work, there was no history of obtaining systems of controlled release of steroids based on chitosan, only systems of urea and other non-steroidal agrochemicals were found based on said polymer. from this background, it is necessary to have controlled release systems for biologically active steroids, especially the synthetic analogue 3 of brasinosteroids (di31), for use in agriculture. it is possible to prepare a polymer system based on chitosan with a biologically active steroid (microparticles) that allows its controlled dosage in plants. therefore, in order to validate this hypothesis, the general objective of the work is to obtain and characterize physicochemically the microparticles of chitosan loaded with di-31, using the technique of spray drying for its application to plants[4]. experimental part chitosan used was supplied by chitopharm (haugesund, norway), mw = 129.4 kda degree of acetylation 20.5%. we used di-31 (natural products center of the university of havana) and sodium tripolyphosphate (tpp, sigma-aldrich). solubility study of the brassinosteroid analog di-31: a solubility study was carried out in order to evaluate the characteristics of the solvents to be used in the drying process using the spray driying. thus, 4 solutions of ethanol and water in the proportions 80/20, 70/30, 60/40 and 50/50 were prepared with 300 rpm magnetic stirring maintained for a period of 15 minutes. in parallel, 4 more solutions were prepared in the same proportions and conditions but of tetrahydrofuran (thf) and water[5]. preparation of microparticles of chitosan and chitosan/di-31 by spray-drying: to obtain the chitosan microparticles loaded with di-31, a solution of chi at 1% (m/v) was started. di-31 (as active ingredient to be encapsulated) and tpp (as crosslinking agent) were added to the chitosan solution by 0.25 and 0.01 respectively, relative to the polymer mass. the resulting suspension was sprayed in a mini spray-dryer b-290 (büchi labortechnik ag, flawil, switzerland) with 0.7 μm nozzle at an inlet temperature of 90 ° c with a feed liquid flow at 5 ml / min and an outlet temperature of 115 °c[6]. obtaining the microparticles: the microparticles of chitosan loaded with di-31 were obtained by spray drying of the buchi brand from germany. the process passed through successive stages, the first of which involved the formation of an oil-water emulsion (o / w). an aqueous / ethanol solution (70/30%) was used as the aqueous phase, while a solution of di-31 (active ingredient) was used as the organic phase. in parallel, a solution of chitosan in both acetic acid was prepared at 1%. the resulting formulation was suctionally introduced into the apparatus having an inlet temperature of 105 degrees celsius and an outlet temperature of 90. microparticles of sizes between 1 and 4 micrometers were obtained[7]. physico-chemical characterization of microparticles obtained: the microparticles of chi/di-31 were characterized by ftir spectroscopy using a perkin-elmer ftir (italy) spectrophotometer with 32 scans and 4 cm-1 resolution. samples were prepared by the potassium bromide tablet method. the size of microparticles was determined using a nikon eclipse e-400 optical microscope (mexico d.f.). the morphology of the microparticles was studied by scanning electron microscopy (sem) with a tescan 5130 sb microscope (czech republic). samples were coated with au-pd using a polaron sc 7620 (uk). determination of encapsulation efficiency: 25 mg of chi/di-31 microparticles, and chi (placebo) microparticles were shaken at 40 ° c in 0.1 n acetic acid for 24 h. the resulting solutions were filtered and the amount of encapsulated steroids was estimated by absorbance determined by uv at 245 nm using an ultrospec 2100 pro uv spectrophotometer. the concentration of the solution was determined from a previously obtained calibration curve. the amount of encapsulated compound was expressed as percent loading (g of brasinoesteroides in 100 g of microparticles). the reported loading rate is expressed as the mean standard deviation ± sd of four experiments[7,8]. in vitro drug release study of microparticles: in vitro release of di-31 from the chi microparticles was studied by measuring the corresponding profiles using uv detection at a specific wavelength. 25 mg of chi/di-31 microparticles were placed in a volumetric flask containing phosphate buffer and sodium pbs (ph 6.0) and 70% ethanol solution in parallel to a total volume of 25 ml and incubated at 30 ° c with constant stirring at 100 rpm. a 1ml aliquot was periodically taken from the flask and replaced with fresh solution to maintain a constant volume. through the value of the uv absorbance of the solution, the concentration of the solution was determined by extrapolation of the curve and with the slope value. these studies were done in triplicate for each sample. results figure 1 shows the electron micrograph of the microparticles of chi/di-31 + tpp obtained by spray-drying; the microparticles have a morphology and size characteristic of the used drying materials and devices, vol 2(1), 1505 (2017) – doi: 10.23647/ca.md20171505 a.k. collado, g. hernández, v. morejón, f. coll, c. peniche encapsulation of a bioactive steroid in polymer matrix process as described in the literature for the equipment employed. the images exhibit a spherical morphology of the microparticles, attributable to the use of the spray drying. the morphology of chi / di-31 microparticles can be seen in figure 2. in addition, a speckle is observed on the surface thereof, characteristic of the insolubility in water of the encapsulated active principle. figure 1. sem micrograph of the chi/di-31 + tpp microparticles obtained by spray driying. figure 2. sem micrograph of the microparticles of chi/di-31 obtained by spray drying. infrared spectroscopy to fourier transform the ftir, chitosan, chi/ di-31 microparticles(mdi-31) and the tpp cross-linked microparticles (mdi-31+tpp) are shown in fig. 3. also included is the placebo spectrum (m) of the microparticles for comparison of the characteristic bands. figure 3. ftir spectra of chi / di-31 + tpp microparticles release study of chi/ di-31 microparticles in ethanol / water and buffer-phosphate solution (pbs) the release behavior of the di-31 studied from the microparticles was evaluated by performing in vitro release experiments at ph 6 (pbs) and by mixing water and ethanol to simulate the conditions of the current agrochemical formulations. in all cases a sustained release of the steroid was obtained, characterized by an almost constant release rate (zero order kinetics) during the first 24 h. as expected, the release was always higher in ethanol / water than in pbs, due to the higher solubility of the steroid in said organic solvent. figure 4. microparticle release profile in ethanol / water materials and devices, vol 2(1), 1505 (2017) – doi: 10.23647/ca.md20171505 a.k. collado, g. hernández, v. morejón, f. coll, c. peniche encapsulation of a bioactive steroid in polymer matrix figure 5. release profile of the microparticles in pbs (ph 6) discussion as shown in figure 1, the chi/di31 particles exhibit a collapsed appearance, whereas in the chi/di31 + tpp particles the predominant shape is spherical, further exhibiting a characteristic mottling on its surface. the round shape of the particles of chi/di31 can be attributed to the drying process due to the evaporation of the solvent that generates an external crust, and once formed this is that the solvent still present in its interior evaporates resulting in a partial shrinkage of the particle[9,10]. in the case of the microparticles of chi/di31 + tpp, the shape is markedly spherical, some with some roughness, but not collapsed, which is a consequence of the presence of tpp in the atomized mixture. depending on the equipment used that has a nozzle with internal diameter of 0.7 μm, the particle size should be less than 10 μm. taking into account the scale of the micrograph, the particle size oscillates around 4 μm, which is in agreement with the nozzle used and with the results reported by desai et al.[11] in a study of obtaining chitosan microparticles with tpp in which the particle size obtained varies from 3.1-10.1 μm. as for the yield of the process, 69 ± 1% was obtained for chi /di31 microparticles and 54.4 ± 0.8% for chi / di31 + tpp microparticles. other authors report similar results and associate the loss of mass to the material adhered to the walls of the chamber and the cyclone of the spray, which is inherent in the technological process when working at a bank scale[12]. efficiency of encapsulation reached was 46.8 ± 0.7%. this result is due, among other factors, to the known fact that when a suspension is atomized, some of the drug crystals are left out of the microdroplets and therefore are not encapsulated[6]. this low encapsulation efficiency could be improved from a technological view from a study of the concentrations of polymer, drug and crosslinking agent in the mixture to be atomized, in addition to the optimization of the drying parameters. the ir spectrum of chi / di-31 microparticles shows absorption bands at 2942-2784 cm-1 (c-h stretching aliphatic band), 1657 cm-1 (amide i), and 1.597 cm-1 (-nh 2) flexure (amide iii). the absorption bands at 1154 cm-1 (antisymmetrical stretching of the c-o-c bridge), 1082 and 1032 cm-1 (skeletal vibrations involving c-o stretching) are characteristic of their saccharide structure[8]. the chi/ di-31 microparticle spectra are dominated by the chi peaks due to the excess chi on the di-31 in the microparticles. the spectrum of di-31 shows a more intense and narrow band at 1700 cm-1, which is absent in the spectrum of empty microparticles. these bands overlap, the amide i and the -nh2 bands at 1650 and 1597 cm-1, respectively, producing a broadband ranging from 1700 to 1500 cm-1. the observed hypsochromic change of these peaks is probably the result of an interaction of the hydroxyl groups and / or carbonyl groups of the di-31 with the amine group of chi molecules. the abr di-31 was loaded into tpp and chitosan forming microparticles. the highest loading percentages were obtained using ethanol solution of the steroid. although in both cases the load never exceeded 50%, a remarkable increase in the load percentage is obtained when the di-31 is only in the system. sustained release profiles were obtained for all 3 cases studied. the results indicate that when introducing a novel process of obtaining by driying spray it would be possible to design an efficient system of supply based on chitosan for the sustained release of brasinoesteroids for its application as agrochemicals. acknowledgements: we are indebted to the science doctors tamara menendez and jesus gonzales, researchers from the biomaterials center for dedicating hours of their time in a disinterested way to our scientific work. references [1] akbuga, j. , a biopolymer: chitosan, international journal of pharm. advances, vol. 1, pp. 3-18 (1995) [2] he, p., davis, s.s. and illum, l., chitosan microspheres prepared by spray-drying, international journal of pharmaceutics, materials and devices, vol 2(1), 1505 (2017) – doi: 10.23647/ca.md20171505 a.k. collado, g. hernández, v. morejón, f. coll, c. peniche encapsulation of a bioactive steroid in polymer matrix vol. 187, no. 1, pp. 53-65 (1999) [3] huang, y.c., chiang, c.h. and yeh, m.k., optimizing formulation factors in preparing chitosan microparticles by spray-drying method, journal of microencapsulation, vol. 20, no. 2, pp. 247-260 (2003) [4] bhattarai n, gunn j, zhang m. chitosan-based hydrogels for controlled, localized drug delivery. advanced drug delivery reviews 62:83-99 (2010) [5] berthold, a., cremer, k. and kreuter, j., influence of crosslinking on the acid stability and physicochemical properties of chitosan microspheres, s.t.p. pharma sciences, vol. 6, no. 5, pp. 358-364 (1996) [6] bulgarelli, e., forni, f. and bernabei, m.t., casein/gelatin beads:i. cross-linked solution composition effect on cross-linking degree, international journal of pharmaceutics, vol. 190, pp. 175-182 (1999) [7] kim, c.j. and lee, p.i., synthesis and characterization of suspension-polymerized poly(vinyl alcohol) beads with coreshell structure, journal of applied polymer science, vol. 46, no. 12, pp. 2147-2157 (1992) [8] ré, m.i., microencapsulation by spray drying, drying technology, vol. 16, no. 6, pp. 1195-1236 (1998) [9] vandelli, m.a., pifferi, g., seghizzi, r. and cameroni, r., swelling behaviour of gelatin microspheres crosslinked with d,lglyceraldehyde. the effect of the preparative factors, pharmacy and pharmacology. letters. vol. 5, pp. 116-119 (1995) [10] tewes f, boury f, benoit jp. biodegradable microspheres: advances in production technology. in: benita s, editor. microencapsulation methods and industrial applications 158. 2nd ed. usa: taylor & francis group, p. 1-53 ( 2006) [11] desai kgh, park hj. preparation and characterization of drug-loaded chitosan-tripolyphosphate microspheres by spray drying. drug development research; 64:114-28 (2005) [12] peniche c, fernández m, gallardo a, lópez-bravo a, román js. drug delivery systems based on porous chitosan/polyacrylic acid microspheres. macromolecbioscien, 3:540-5 (2003) important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com materials and devices, vol 2(1), 1505 (2017) – doi: 10.23647/ca.md20171505 mailto:contact@co-ac.com http://materialsanddevices.co-ac.com/ introduction copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. rev a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 article type: a-regular research paper vortex phase transition and superconducting properties of organic quasi-two-dimensional -(bedt-ttf)2cu[n(cn)2]br h. el ouaddi (1), a. tirbiyine (1), a. taoufik (1), y. ait ahmed (1), f. chibane (1), h. chaib (2), a. nafidi (2), s. snoussi (3) (1) e.m.s, research laboratory, university of ibn zohr, bp: 8106, agadir, morocco (2) l.p.m.c.n.e.r, research laboratory, university of ibn zohr, bp: 8106, agadir, morocco (3) laboratory of solid physics (cnrs, ura2), university of paris-sud, building 510, 91405 orsay, france corresponding author : hassanelouaddi@gmail.com received: 12 january 2018 / received in final form: 15 march 2018 / accepted: 16 march 2018 abstract : we report investigations of the low temperature dc susceptibility and the magnetization on the layered organic superconductor κ-(bedt-ttf)2cu[n(cn)2]br near 80k and the effect of disorder on the superconducting transition temperature tc. the shielding effect (s) and the critical current density jc were studied (with h parallel to the c axis of the crystal). jc can be estimated by analysis of magnetic hysteresis measurement using the bean model. for each temperature value, we observed two regimes in the critical current density jc(h). this result implies that there exists a first-order phase transition in the vortex system in this organic superconductor. our results show that the magnetic properties of these compounds depend strongly on the cooling rate. the structural transformation which occurs at the vicinity of 80k very strongly influences the physics of vortex lattice and the associated magnetic behavior. keywords : organic superconductor, critical current, shielding effect, magnetic susceptibility, vortex pinning. introduction the layered organic molecular crystals κ-(bedt-ttf)2x based on a donor molecule bis(ethylenedithio)tetrathiafulvalene (abbreviated as bedt-ttf) have been recognized as highly correlated electron systems [1]. they have a layered structure with alternating sheets of metallic (dimerized et molecules) and insulating (anion, x) planes. among them, compounds of the family κ-(bedt-ttf)2x have recently attracted considerable attention because of their similarity to the high tc cuprates and the possibility that they may also have a non-conventional paring state [2]. organic superconductors exhibit other typical features like a structural transformation occurring around 80k for κ(bedtttf)2cu[n(cn)2]br and introduces a certain degree of disorder in the conducting planes. that can influence considerably the physics of vortex lattices of these compounds and the associated magnetic behavior. organic charge transfer salts are excellent model systems in which to study many of the questions about the strongly correlated phenomena described above. band structure suggests that these materials mailto:e-mail@address mailto:e-mail@address mailto:e-mail@address mailto:e-mail@address mailto:e-mail@address a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 should be metals at all experimentally relevant pressures and temperatures. further, organic chemistry allows the organic charge transfer salts to be subtly tuned in ways that have never been achieved in inorganic materials. the compound κ(et)2cu[n(cn)2]br constitutes a beautiful example, for which, the mott transition can be driven by replacing the eight hydrogen atoms in the et molecule with deuterium [3]. a remarkable feature of the electronic state of κ-(bedtttf)2x compound is that, the native quarter filled band is modified to the effective half filled band by the strong dimer structure consisting of two bedt-ttf molecules. in fact, the bedt-ttf molecule has two ethylene groups at the end; the two-dimensional conduction planes consist of bedt-ttf molecular dimers, which form an anisotropic triangular lattice. when the terminal ethylene groups in each et molecule contain all possible eight hydrogen atoms (h8), the material shows bulk superconductivity. upon replacing the hydrogen by deuterium (d8), tc gets considerably reduced, the phase transition becomes broader, and no volume superconductivity is observable. figure 1: (a) crystal structure of κ-br; (b) eclipsed and staggered configurations of the ethylene groups (ch2)2 of bedt-ttf molecule from a dimerized structure. organic bedt-ttf molecules stack in conducting planes separated by inorganic insulating layers, giving rise to a highly anisotropic quasi-two dimensional band structure; (c) view of the packing of the polymeric anion chains in κ-br. protons on the bedt-ttf molecule are omitted for clarity. the layered structure of κ-(bedt-ttf)2x family of organic molecular metals is shown in figure 1(a). bedt-ttf molecules dimerize, forming molecular units that stack on a triangular lattice in two-dimensional planes. the removal of one electron from each bedt-ttf dimer causes the tightbinding band to be half filled, and to balance the charge, layers of anion x are located between the partially oxidized bedt-ttf sheets. the flat bedt-ttf molecules (figure 1(b)) dimerize to form molecular units that stack in planes on a triangular lattice [4]. the anions, x, separate the planes and accept one electron from each bedt-ttf dimer. influence of the superconducting transition temperature tc of κ-(bedt-ttf)2cu[n(cn)2]br was found in one of the first investigations after synthesis of the compound [5]. recently this effect has been the subject of numerous studies in the salt with both usual h8-bedt-ttf and deuterium substituted d8bedt-ttf molecules (which we will subsequently abbreviate as κ-h8-br and κ-d8-br salts, respectively) [6-11]. there is growing evidence that a proper cycling is important for electronic properties [6. 7. 9-11]. the effect is related to the phase transition at 80k, due to the order-disorder transformation of the terminal ethylene groups of the bedtttf molecules [12-13]. in this paper, we report on an extensive experimental study of the effect of the cooling rate on the interlayer transports properties at tc and on the magnetic susceptibility and magnetization. by freezing the sample into different disordered states, we found that there is a strong evidence for a structural transformation at around 80k. the results of the critical current and the shielding effect for the κ-(bedtttf)2cu[n(cn)2]br sample are also present as function of magnetic field at different temperatures with magnetic fields applied perpendicular to the conducting planes. experimental section single crystals of the κ-(bedt-ttf)2cu[n(cn)2]br superconductor were synthesized at the jean rouxel institute of materials. both hydrogenated and deuterated compounds were used in this study. the two samples have average dimensions: 0.7×0.7×0.2mm3 and 1×1×0.25mm3, respectively. our samples had good magnetic quality and were stable; the results remained unchanged despite repeating the experiment several times. the block-like crystals weighing m=0.59mg for κ-h8-br and m=2.07mg for κ-d8-br. before starting each measurement, the sample was first warmed to a given temperature well above tc. once the residual field is eliminated, the sample was zero field cooled (zfc) or field cooled (fc) to a desired temperature. magnetic measurements were done with a commercial conducting quantum interference device (squid), which produces a magnetic field up to 5t. magnetic field was applied perpendicular to the sample plane. the superconducting magnet was reset such that the remaining field was less than 1μt. we have investigated the magnetic susceptibility of the superconducting phase as a function of the cooling rate in the zfc conditions. in the slow cooling rate, the sample was cooled from 160–90k at a cooling rate of about 2k/min and then from 90–70k, at a cooling rate of 0.1k/min. furthermore, the sample is then kept at the temperature of 70k during 20h a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 and then cooled directly to 2k at a cooling rate of 5k/min. in the rapid cooling condition, the sample was submerged directly in the dewar at a temperature of the order of 2k. results and discussion the superconducting transition temperature was measured by use of a dc susceptibility, and the magnetic field was applied perpendicularly to the conducting layers. 2 4 6 8 10 12 14 -5 -4 -3 -2 -1 0 2 4 6 8 10 12 14 -4 -3 -2 -1 0  (1 0 5 e m u )  20 oe 3 oe 1.5 oe 1 oe  (1 0 -5 e m u ) t(k) 5 oe figure 2: magnetic susceptibility as a function of temperature, at for different magnetic field values for hydrogenated κ-h8-br in slow cooling. the inset shows the susceptibility versus temperature at field 5oe. we present in figure 2 the susceptibility variations versus temperature for hydrogenated κ-h8-br sample in slow cooling conditions, at different fields (h=1oe, h=1.5oe, h=3oe and h=20oe) and for h=5oe in the onset. values of the superconducting transition temperature have been taken here from the diamagnetic transition curve at the crossing point of the interpolation lines from the normal and superconducting regions. we can plot thus defined tc (i.e., suppression of superconductivity) as a function of field with overlaid for the slow-cooled, as shown in figure 3. clearly, the critical tc decreases with increasing field monotonically. on the other hand, a strong increase of tc, as large as 1k was reported, in the case of deuterated (κ-d8-br) sample [14]. temperature 80k corresponds to a structural phase transition temperature in the anion chain. cooling through 80k at different rates will freeze the high-temperature phase to low temperatures and the presence of local moment suppresses the superconducting transition temperature. scanning microregion infrared reflectance spectroscopy measurements have shown evidence for macroscopic insulating/metallic region phase separation at the surface of fast cooled samples [15]. 0 5 10 15 20 11,50 11,55 11,60 11,65 11,70 11,75 t c (k ) h(g) figure 3: superconducting critical temperature versus magnetic field for hydrogenated κ-h8-br. let us now look at the amplitude of the real part of dc susceptibility (figure 4) which is nothing but the shielding effect (s) [16]. furthermore, on the basis of data shown in figure 2, we obtained the shielding effect dependence of the magnetic field. the shielding effect represents the exclusion of magnetic flux by the sample in alternative dynamic mode. s was set arbitrarily equal to 1 for hdc=1oe. it can be seen from the curves that the shielding effect depends strongly on both temperature and applied magnetic field. further, the decrease in s as a function of the temperature was much slower in the case of the low field. it clearly shows an improvement of the quality of the grains and intergranular coupling in the sample. 0 5 10 15 20 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 s (a .u ) h(oe) 8.5 k 9.5 k 10.5 k figure 4: shielding effect (s) in arbitrary units as a function of the magnetic field, for three different temperatures. magnetization hysteresis cycles measurements have played an important role in understanding the critical characteristics of superconductor. in particular, it makes possible a contactless determination of the critical current density using the critical state model [17]. it is well known that the critical current a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 density jc depends on the flux pinning properties of a superconductor. -1000 -500 0 500 1000 -6x10 -3 -4x10 -3 -2x10 -3 0 2x10 -3 4x10 -3 6x10 -3 slow cooling m (e m u ) h(g) t=3 k rapid cooling figure 5: magnetization hysteresis cycle at t=3k in slow and rapid cooling of deuterated κ-(bedtttf)2cu[n(cn)2]br sample. figure 5 shown the magnetic hysteresis loops of (κ-d8-br) compound at t=2k after slow and rapid cooling rate, in the magnetic field range of (−1kg; 1kg). in the case of the slow cooling rate, a wide cycle is observed. the hysteresis results from flux pinning, and when the pinning is absent, the magnetic behavior of the superconductor is fully reversible. the presence of several pining centers provides high currents. when the magnetic field increases, the magnetic flux continues to penetrate the sample and the diamagnetism is not perfect. it is important to note the absence of the secondary peak in the whole temperature range. furthermore, the secondary peak has been observed both in iron-pnictides [18-19] and in cuprate high tc superconductors [20]. the hysteresis cycles depend strongly on the cooling rate vc of the samples through the order–disorder transformation which affects the ethylene groups c2h4 and which occurs at the vicinity of 80k [9]. the value of 80k was speculated to correspond to a structural transition temperature in the anion chain. taniguchi et al [21] reported the cooling-rate dependence of the magnetization curves, where the hysteretic magnetization width becomes narrow by cooling fast. one may consider that cooling fast introduces a much larger number of the ethylene-disorders, and leads to much stronger vortex pinning on the basis of a concept of the simple pinning effect by disorder. the critical current density was determined using the bean critical state model, from the irreversible parts of the magnetization curves with the formula [17]: d =j c m 30  (1) where d is the size of the simple and δm is the difference between the magnetizations measured while decreasing and increasing field in the perpendicular field orientation. in figure 6, we present the critical current density jc(h) variations. as can be seen in this figure jc depend strongly on both temperature and magnetic field. it is important to note that in the case of κ-d8-br sample, the jc(h) dependence can be divided into two regimes, e.g. jc(h) exhibits a slight decrease below some an applied magnetic field h*. the latter being the field where the slope of jc(h) curve change. a gradual transition to a power low behavior, that is   hhj c )( is found above this field. thus, this regime, named the power law region, is usually attributed to strong pinning centers. furthermore, the second regime shows a sharp drop in the jc occurring because of a fast creeping of vortices. 10 1 10 2 10 3 10 -6 10 -5 10 -4 10 -3 j c (a /c m 2 ) h(g) 4 k 6 k figure 6: critical current density versus magnetic field, for two different temperatures (t=4k and t=6k) and for deuterated κ-(bedt-ttf)2cu[n(cn)2]br sample in slow cooling. the strong decrease of the current density jc(h), when h>h* can be explained by a collective pinning behavior of vortices. the vortices number becomes greater when the applied magnetic field increases. conclusions as conclusion, we reported the magnetic susceptibility and the magnetization measurements to investigate the disorder effect and the first-order phase transition in the vortex system in organic superconductor κ-(bedt-ttf)2cu[n(cn)2]br. our a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 results show that both shielding effect and the critical current depend strongly on the temperature and magnetic field. the cooling rate has a considerable effect on the superconducting properties; the effect is much less in the case of hydrogenated salts. in particular, the cooling rate near 80k controls the amount of disorder at low temperature. superconducting transition temperature tc is determined using the dc magnetic susceptibility. finally, it is clear from all the above discussions and results that organic superconductors offer a unique opportunity to study (and perhaps to distinguish between) the contribution of various physical defects and thermal fluctuations to the broadening of the superconducting transition around tc. acknowledgements: this research was partially supported by cnrs (france) and cnrst (morocco) for financial support via pics 522. we thank c. mézière and p. batail for providing us the sample references 1. b. j. powell, and r. h. mckenzie, journal of physics: condensed matter, vol.18, p 827 (2006) 2. r. h. mckenzie, sciences, vol.278, p 820-821 (1997) 3. h. taniguchi, k. kanoda, and a. kawamoto, physical review b, vol.67, p 014510 (2003) 4. t. ishiguro, k. yamaji and g. saito, organic superconductors 2nd edn, springer, berlin (2006) 5. w. k. kwok, u. welp, k. d. carlson, g. w. crabtree, k. g. 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studies of high temperature superconductors: diverse superconducting systems and some miscellaneous applications, vol.37, ed. a. narlika (nova science publishers, huntington, ny, usa), p 205–248 (2001) 14. a. tirbiyine, a. taoufik, a. nafidi, h. el ouaddi, s. snoussi, h. chaib, s. bahsine, o. touraghe and n. hassanaine, iop conf. series: mater. sciences and engineering, vol.13, p 012036 (2010) 15. n. yoneyama, t. sasaki, n. kobayashi, y. ikemoto and h. kimura, physical review b, vol.72, p 214519 (2005) 16. r. a. hein, t. l. francavilla and d. h. leinberg, eds., magnetic susceptibility of superconductors and other spin systems. new york: plenum, ch.3 (1991) 17. c. p. bean, t. sasaki, n. kobayashi, y. ikemoto and h. kimura, physical review letters. vol.8, p 250 (1962) 18. w. zhou, x. xing, w. wu, h. zhao and z. shi, scientific reports, vol.6, p 22278 (2016) 19. a. k. pramanik, l. harnagea, c. nacke, a. u. b. wolter, s. wurmehl v. kataev and b. büchner, physical review b, vol.83, p 094502 (2011) 20. y. yeshurum, n. bontemps, l. burlachkov and a. kapitulnik, physical review b, vol.49, p 1548 (1994) 21. h. taniguchi, a. kawamoto, k. kanoda. physical review b, vol.59, p 8424 (1999) a. el ouaddi et al vortex phase transition and superconducting properties of organic quasi-two-dimensional… oaj materials and devices, vol 3, #1, 1603 (2018) – doi: 10.23647/ca.md20181603 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers: a: regular papers, l: short papers, r: review papers, t: technical papers, ur: unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 article type: a-regular research paper investigation of dna denaturation from generalized morse potential r. el kinani (1), h. kaidi (2), m. benhamou (3) (1) physics department, faculty of sciences p.o. box 11201, moulay ismail university, meknes, morocco, radouane_kin@yahoo.fr (2) crmef, p.o. box 255, meknes, morocco, hamidkaidi@gmail.com (3) physics department, faculty of sciences p.o. box 11201, moulay ismail university, meknes, morocco, benhamou.mabrouk@gmail.com correspondingauthor: radouane_kin@yahoo.fr received: 18 january 2018 / received in final form: 30 june 2018 / accepted: 02 july 2018 abstract: in this paper, we present a non-linear model for the study of dna denaturation transition. to this end, we assume that the double-strands dna interact via a realistic generalized morse potential that reproduces well the features of the real interaction. using the transfer matrix method, based on the resolution of a schrödinger equation, we first determine exactly their solution, which are found to be bound states. second, from an exact expression of the ground state, we compute the denaturation temperature and the free energy density, in terms of the parameters of the potential. then, we calculate the contact probability, which is the probability to find the double-strands at a (finite) distance apart, from which we determine the behaviour of the mean-distance between dna-strands. the main conclusion is that, the present analytical study reveals that the generalized morse potential is a good candidate for the study of dna denaturation. keywords : dna, interactions, generalized morse potential, denaturation transition, free energy. introduction deoxyribonucleic acid, more commonly known as dna, is a complex molecule that contains all of the information necessary to build and maintain an organism. all living things have dna within their cells. in fact, nearly every cell in a multicellular organism possesses the full set of dna required for that organism. however, the dynamics of dna transcription is among the most fascinating problems of modern biophysics, because it is at the basis of life. it is also a very difficult problem due to the complex role played by rna polymerases in the process. it is now well established (freifelder, 1987) that the local denaturation of dna is involved, so that it is interesting to investigate the thermal denaturation of the double-helix as a preliminary step to the understanding of the transcription (fig. 1). dna denaturation is a process that refers to the melting of the double-stranded dna into two single strands. in fact, such a phenomenon originates from the breaking of hydrogen bonds between the bases in the duplex. thermodynamically speaking, the major contribution to dna helix stability is the stacking of the bases on top of one another. hence, in order to denature dna, the main obstacle to overcome is the stacking energies providing cohesion between adjacent base pairs. moreover, studies of molecular dynamics and structure of nucleic acids are of general importance for the understanding of their functions. as such they have been subject of several theoretical and experimental investigations. because of the importance of the functions played by dna denaturation in replication, transcription and recombination processes, many theoretical and experimental techniques have been developed to study melting or strand separation of dna. http://www.synonymo.fr/synonyme/investigation http://www.synonymo.fr/synonyme/investigation r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 figure 1: double-helix structure of dna shown in a full atomic representation bursts (left) and representation compact (right). the physics of dna thermal denaturation (or melting), that is the separation of the two strands upon heating, is a subject which has a long history [1]-[3], because it can be viewed as a preliminary for the understanding transcription. the separation of the two complementary strands starts locally by the formation of small denatured regions, very similar to the transcription bubble. another important motion of the dna molecule is its "breathing" or fluctuational opening. in these very large fluctuations, the base-pairs are temporarily broken, and the two bases are exposed for chemical reaction, for a very short time (10−7s). these fluctuational openings can be considered as intrinsic precursors for the denaturation, and they could play a role in carcinogenesis by external molecules [4]. the wide interest in this problem is also motivated by the fact that uv absorption spectroscopy experiments [5]-[6] indicate that the whole denaturation process looks like a chain of sharp first-order-like phase transitions, in the sense that large portions of inhomogeneous dna sequences separate over narrow temperature intervals. the molecular deformation involved in melting or in fluctuational openings, is so large that they cannot be described by linear approximations therefore, biomolecular dynamics is a fascinating topic for nonlinear science, because it is related to basic phenomena of life and one knows that it has to be fundamentally nonlinear. we point out that the first model for the study of dna denaturation is ising-like, which represents a base-pair by a variable taking only two values, 0 and 1, i.e., closed and open. the denaturation transition is then analyzed by treating the statistical mechanics of this one-dimensional ising-spin chain. the best known model in this category is that introduced by poland and scheraga [7]. in our case, we have adopted some model introduced by dauxois, peyrard and bishop [8], with a change in the level of the interaction potential between the bases of the double-helices. the model by dauxois, peyrard and bishop considers a simplified geometry for dna chain, where one neglects the asymmetry of the molecule and represents each strand by a set of point-like masses corresponding to the nucleotides. we emphasize that, in their model, peyrard and bishop [8] adopted the standard morse potential (mp) [9] that depends on three kinds of parameters. such a potential reproduces well the main characteristics of the real potential, namely repulsive at short-distance (steric interaction) and attractive (van der waals interaction), at high-distance. we discuss here some aspects of dna dynamics and we show that simple nonlinear models can provide a good description of the large amplitude distortions of the molecule, which are observed experimentally. our basic approach can be viewed as an extension of ising models, which have been widely used to study the statistical mechanics of the melting, in which we treat completely the dynamics of the bases. in this work, we re-examine the study of the denaturation of dna, using an extended peyrard and bishop model [8], where the standard mp is replaced by a more realistic one we introduce for the first time, termed q-mp, with a real parameter, q (see below). such a new potential reduces to the standard mp for q = 0, and to that of dang-fan potential [10], for q = −1. in this sense, the q-mp is more general. in addition, the introduction of this new potential is that, the experimental adjustment of q-parameter may model various physical situations. the remaining of presentation proceeds as follows. in section 2, we describe the used model for dna denaturation. a study of the denaturation transition is presented in section 3. finally, some concluding remarks are drawn in the last section. a simple model for dna denaturation: the main characteristics of our model are as follows: (i) one takes into account the transverse motions. the displacements from equilibrium of the n-th nucleotide are denoted as wn, for one chain, and vn, for the other. the longitudinal displacements are not considered, because their typical amplitudes are significantly smaller than the amplitudes of the smaller ones [11]. (ii) two neighboring nucleotides of the same strands are connected by an harmonic potential, in order to keep the model as simple as possible. on the other hand, the bonds connecting the two bases belonging to different strands, are extremely stretched, when the double-helix opens locally, so that their nonlinearity must not be ignored. we use a generalized morse potential to represent the transverse interaction of the bases in a pair. it describes not only the hydrogen bonds, but the repulsive interactions of the phosphate groups, partly screened by the surrounding solvent as well. the hamiltonian of the model is then the following 𝐻 = ∑ { 1 2 𝑚(�̇�𝑛 2 − �̇�𝑛 2) 𝑛 + 1 2 𝐾[(𝑤𝑛 − 𝑤𝑛−1) 2 + (𝑣𝑛 − 𝑣𝑛−1) 2] + 𝑉𝑞 (𝑤𝑛 − 𝑣𝑛 )} , (1) where 𝑚 is the reduced mass of the bases. the contribution, 𝑉𝑞 (𝑤𝑛 − 𝑣𝑛 ), represents the interaction potential (q-mp) of the bases in a pair, whose form is the following http://www.synonymo.fr/synonyme/investigation r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 𝑉𝑞 (𝑤𝑛 − 𝑣𝑛 ) = 𝐷 ((1 − 𝑏 𝑒𝛼(𝑤𝑛−𝑣𝑛)/√2 + 𝑞 ) 2 − 1) . (1a) we assume that the real parameter 𝑞 is such that 𝑞 > 0 or −1 ≤ 𝑞 < 0. in fact, the latter acts as an important deformation parameter. there, 𝑏 is some parameter that is related to the minimum of the interaction potential, 𝐷 is the potential depth and 𝛼 > 0 defines the potential-range. notice that, the proposed potential is a four parameter exponential-type one, which is already pointed out in ref. [12], and it may reduce to the most well-known exponential-type molecule potentials by choosing appropriate parameters (𝐷, 𝑏, 𝛼, 𝑞). the values 𝑞 = 0 and 𝑞 = −1 describe the morse and deng-fan potentials, respectively. hence, the potential 𝑉𝑞 (𝑤𝑛 − 𝑣𝑛 ) is more general and may be a good candidate for the study of a large class of interacting molecular systems. in fig. 2, we report the 𝑞-generalized mp upon distance, for various values of the parameter 𝑞 keeping fixed the other ones, (𝐷, 𝑏, 𝛼). in particular, this figure shows that, the potential minimum is shifted towards its smaller values, as the parameter 𝑞 is increased. figure 2: reduced morse potential, 𝐕𝐪 (𝐰𝐧 − 𝐯𝐧), versus distance, for different values of 𝐪. now returning to equation (1) when it is expressed in terms of the variables 𝑥𝑛 = (𝑤𝑛 + 𝑣𝑛 ) √2⁄ and 𝑦𝑛 = (𝑤𝑛 − 𝑣𝑛 ) √2⁄ , yielding 𝐻 = ∑ * 1 2 𝑚�̇�𝑛 2 + 𝐾 2 (𝑥𝑛 − 𝑥𝑛−1) 2 𝑛 + ( 1 2 𝑚�̇�𝑛 2 + 𝐾 2 (𝑦𝑛 − 𝑦𝑛−1) 2) + 𝐷 ((1 − 𝑏 𝑒𝛼𝑦𝑛 + 𝑞 ) 2 − 1)+ . (2) the part of the hamiltonian that depends on the variables 𝑥𝑛 ′𝑠, describes the displacement of the centre of mass of each base pair. it is well behaved, so that we can ignore this term in the statistical mechanics of the model. therefore, we henceforth consider only the part of 𝐻 which depends only on 𝑦𝑛, because it possesses the complete information on the associative dynamics of the dna, 𝐻′ = ∑ * 1 2 𝑚�̇�𝑛 2 + 𝐾 2 (𝑦𝑛 − 𝑦𝑛−1) 2 + 𝑉𝑞 (𝑦𝑛 )+ .𝑛 (3) figure 3: schematic representation of model. in the above expression, m is the mass of strands and k > 0 accounts for their elastic constant. study of dna denaturation and its statistical mechanics: since we are interested in the thermal denaturation of dna, the natural approach is to make use of statistical mechanics. due to the one-dimensional character of the system, and since the interactions are restricted to nearest neighbor interactions, it can be treated exactly, including fully the nonlinearities, with the transfer operator method [13]. in the canonical ensemble, the partition function of the model is related to the hamiltonian, 𝐻𝑦, by 𝑍 = ∫ ∏ 𝑑𝑦𝑛 𝑑𝑝𝑛 𝑒 −𝛽𝐻𝑦 𝛿(𝑝1 − 𝑝𝑁 ) 𝑁 𝑛=1 +∞ −∞ 𝛿(𝑦1 − 𝑦𝑁 ) (4) with the notation 𝛽 = 1 𝑘𝐵 𝑇⁄ , and the dirac-function, 𝛿, ensures the periodic boundary conditions. the integrals over variables 𝑝𝑛 are decoupled gaussian integrals, which can be easily calculated to give 𝑍 = (2𝜋𝑚𝑘𝐵 ) 𝑁/2𝑍𝑦, and due to the onedimensional character of the model, the configurationally part, 𝑍𝑦, is a product of terms that couple two consecutive variables 𝑦𝑛 𝑍𝑦 = ∫ ∏ 𝑑𝑦𝑛 𝑒 −𝛽𝑓(𝑦𝑛,𝑦𝑛−1) 𝑁 𝑛=1 +∞ −∞ 𝛿(𝑦1 − 𝑦𝑁 ) , (5) with the notation 𝑓(𝑦𝑛 , 𝑦𝑛−1) = 𝐾 2 (𝑦𝑛 − 𝑦𝑛−1) 2 + 𝑉𝑞 (𝑦𝑛 ) . (5a) therefore, calculation of 𝑍𝑦 can be performed by the transfer integral (ti) method [14]-[16]. let us define ti operator 𝑦𝑛−1 → 𝑦𝑛 and its eigenfunctions, 𝜑𝑖, by ∫ 𝑑𝑦𝑛−1𝑒 −𝛽𝑓(𝑦𝑛,𝑦𝑛−1)𝜑𝑖(𝑦𝑛−1) = 𝑒 −𝛽𝜖𝑖 𝜑𝑖 (𝑦𝑛 ) . (5b) http://www.synonymo.fr/synonyme/investigation r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 the 𝛿-function in 𝑍𝑦 expression can be expanded in the basis of the eigenfunctions of ti operator as 𝛿(𝑦𝑁 − 𝑦1) = ∑ 𝜑𝑖 ∗(𝑦𝑛 )𝜑1(𝑦1) . (5c) performing successively integrals over variables (𝑦1, 𝑦2, 𝑦3, … , 𝑦𝑁 ), one gets 𝑍𝑦 = ∑ 𝑒 −𝛽𝜖𝑖 ∫ 𝑑𝑦𝑛 |𝜑𝑖 (𝑦𝑛 )| 2 = ∑ 𝑒−𝛽𝑁𝜖𝑖 . 𝑛𝑛 (5d) we used the fact that the functions 𝜑𝑖’s are normalized to unity. in the thermodynamic limit (𝑁 → ∞), the above sum is dominated by the term having the smallest value of 𝜖𝑖 we denote as 𝜖1. therefore, according to ref. [3], we arrive at an equation which is formally identical to the schrödinger equation for a particle experienced a 𝑞-generalized mp, − (𝑘𝐵 𝑇) 2 2𝐾 𝑑2 𝑑𝑦2 𝜑𝑖 (𝑦) + 𝑉𝑞 (𝑦)𝜑𝑖 (𝑦) = 𝐸𝑖 𝜑𝑖 (𝑦) . (7) this schrödinger equation has been exactly solved [10], and in particular, we find that the associated ground state and the ground state energy are exactly given by 𝜑0(𝑦) = 𝑁0𝑒 𝑄1𝑦 ( 𝑒𝛼𝑦 𝑒𝛼𝑦 + 𝑞 ) 𝑄2 𝛼𝑞 , (8) 𝐸0 = − (𝑘𝐵 𝑇) 2 2𝐾 𝑄1 2 . (9) with a known normalization constant, 𝑁0, and 𝑄1 = 2𝐾𝐷𝑏 (𝑘𝐵𝑇) 2 ( 𝑏−2𝑞 𝑞 ) 1 2𝑄2 × 𝑄2 2𝑞 , (10) 𝑄2 = 1 2 [−𝛼𝑞 + √𝛼2𝑞2 + 8𝐾 (𝑘𝐵 𝑇) 2 𝐷𝑏2] . (11) we find that the free energy (per site) is given by 𝑓 = −𝑘𝐵 𝑇 ln 𝑍 = 𝜖0 − 𝑘𝐵 𝑇 2 ln(2𝜋𝑚𝑘𝐵 𝑇) . (12) on the other hand, the computed ground state, 𝜑0(𝑦), gives the contact probability as follows 𝑃(𝑦) = 𝐶0𝑒 2𝑄1𝑦 ( 𝑒𝛼𝑦 𝑒𝛼𝑦+𝑞 ) 2𝑄2 𝛼𝑞⁄ , (13) with the known normalization constant, 𝐶0. now, notice that the system undergoes a denaturation transition, if the ground state energy, 𝐸0, vanishes; this condition then defines the denaturation temperature given by, 𝑇𝑑 = 2√2𝐾𝐷 𝛼𝑘𝐵 × √𝑏 √𝑏 − 2𝑞 (14) that naturally depends on the parameters of the problem, which are (𝐾, 𝐷, 𝛼, 𝑞). before discussing the above expression of the denaturation temperature, we emphasize that the above computed contact probability, relation (13), may be used to determine the meandistance, ξ = 〈y〉, between adjacent strands. we find that, in the vicinity of the denaturation temperature, td, this length scales as ξ = 〈y〉 = ∫ yp(y)dy ∞ 0 ~(td − t) −1 . (15) the divergence of this length is a signature of a denaturation transition. now, come back to the main result dealt with the denaturation temperature expression, relation (14). firstly, such a characteristic temperature depends naturally of the parameters (d, b, α, q) of the q-mp and the elastic constant, k, between neighboring strands. secondly, this temperature is well defined, because of the conditions: −1 ≤ q < 0. thirdly, the denaturation temperature increases, as it should be, with the elastic constant, k. this means that the denaturation transition occurs at high temperature for higher elastic strands. fourthly, the denaturation temperature increases with increasing q-parameter. fifthly, in the q = 0 limit, we find that result from the standard mp [8], that is 𝑇𝑑,𝑞=0 = 2√2𝐾𝐷 𝛼𝑘𝐵 , (16) finally, the value q = −1 defines the denaturation temperature from deng-fan potential [10], 𝑇𝑑,𝑞=−1 = 2√2𝐾𝐷 𝛼𝑘𝐵 × √𝑏 √𝑏 + 2 . (17) conclusion the aim of this work is an analytical study of dna denaturation from a 𝑞-defomed morse potential, using the schrödinger equation method. finally, the main conclusion is that, our analytical studies reveal that the 𝑞-deformed morse potential is a good candidate for the description of dna denaturation and its statistical properties. acknowledgements: we are much indebted to professor t. bickel for fruitful correspondences and helpful discussions, and for our referee, for its useful suggestions and pertinent remarks. http://www.synonymo.fr/synonyme/investigation r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 references 1. d.poland, h.a.scheraga, theory of helix-coil transitions in biopolymers, academic press, new york (1970) 2. r.m.wartell, a.s.benight,thermal denaturation of dna molecules: a comparison of theory with experiment, physics reports, vol.126, p 67 (1985) 3. m.peyrard, nonlinear dynamics and statistical physics of dna, nonlinearity, vol.17, p r1 (2004) 4. o.gotoh, prediction of melting profiles and local helix stability for sequenced dna, advances in biophysics, vol.16, p 1 (1983) 5. r.thomas, structure secondaire et denaturation des acides nucleiques, bulletin de la société de chimie biologique, vol.35, p 609 (1953) 6. a.segerer, t.a.langworthy, k.o.stetter, thermoplasma acidophilum and thermoplasma volcanium sp. nov. from solfatara fields, systematic and applied microbiology, vol.10, p 161 (1988) 7. d.poland, h.a.scheraga, occurrence of a phase transition in nucleic acid models, the journal of chemical physics, vol.45, p 1464 (1966) 8. t.dauxois, m.peyrard, a.r.bishop, thermodynamics of a nonlinear model for dna denaturation, physica d: nonlinear phenomena, vol.66, p 35 (1993) 9. p.m.morse, diatomic molecules according to the wave mechanics. ii. vibrational levels, physical review, vol. 34, p 57 (1929) 10. z.h. deng, y.p. fan, shandong university journal, vol. 7, p 162 (1957) 11. j.a.mccammon, s.c.harvey, dynamics of proteins and nucleic acids, cambridge university press (1988) 12. j.sheng, z.ying, z.xiang-lin, s.liang-tian, identity for the exponential-type molecule potentials and the supersymmetry shape invariance, communications in theoretical physics, vol.36, p 641 (2001) 13. m.peyrard, a.r.bishop, statistical mechanics of a nonlinear model for dna denaturation, physical review letters, vol. 62, p 2755 (1989) 14. d.j.sears, r.a.m.ferrell, statistical mechanics of one-dimensional ginzburg-landau fields, physical review b, vol.6, p 3409 (1972) 15. j.a.krumhansl, j.r.schrieffer, dynamics and statistical mechanics of a one-dimensional model hamiltonian for structural phase transitions, physical review b, vol.11, p 3535 (1975) 16. a.r.bishop, j.a.krumhansl, s.e.trullinger, solitons in condensed matter: a paradigm, physica d: nonlinear phenomena, vol.1, p 1 (1980) http://www.synonymo.fr/synonyme/investigation r. el kinani, h. kaidi, m. benhamou., investigation of dna denaturation from generalized morse potential materials and devices, vol 3 #2,0207 (2018) – doi: 10.23647/ca.md20180207 important:articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and the irown analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! 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(see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://www.synonymo.fr/synonyme/investigation http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com introduction a simple model for dna denaturation: conclusion copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. optical and electronic properties of a two-dimensional quantum dot with an impurity a. chafai et al. znte/cdse type-ii cssqd under an external electric field article type: a-regular research paper znte/cdse type-ii core/shell spherical quantum dot under an external electric field a. chafai (1,*), i. essaoudi (1,2), a. ainane (1,2,3), f. dujardin (2), r. ahuja (3) (1) laboratoire de physique des matériaux et modélisation des systèmes, (lp2ms), unité associée au cnrst-urac 08, university of moulay ismail, fsm, b.p. 11201, meknes, morocco. (2) lcp-a2mc, université de lorraine, institut de chimie, physique et matériaux, 1 bd. arago, 57070 metz, france. (3) condensed matter theory group,department of physics and astronomy, uppsala university, 75120 uppsala, sweden. corresponding author : evoachmed @ gmail.com received: 23 january 2018 / received in final form: 05 april 2018 / accepted: 06 april 2018 abstract : we have investigated in the framework of the envelope function approximation and taking into account the dependence of the electron effective mass on radius the energy of an electron inside a znte/cdse core/shell spherical quantum dot. in order to make the problem more realistic, we describe the conduction bandedge alignment between core and shell materials by a finite height barrier. by applying the ritz variational principle the effect of the electric field on the electronic states was also examined. our numerical results show the opportunity to control the energy states position of the charge carriers inside our core/shell nanostructures by controlling the size (core radius, shell thickness) of the nanostructure and the strength of the external electric field. keywords : core/shell materials, nanostructures, quantum dots, electric field introduction the world of materials science is witnessing a flagrant change in the exploration of matter at small scale [1]. when the matter is at nanoscales, we are witnessing at improved and advanced properties [2]. nowadays nanomaterials have become more popular and their applications may be encountered in various fields, such as nanoelectronics, nanophotonics, nanomedicines, nanosensors and so on [3, 4]. a major feature of nanoscaled materials is the quantum confinement effect, which leads to spatial enclosure of the electronic charge carriers within the nanostructure. when the motion of the charge carriers is frozen over all the three spatial directions, then we talk about quantum dots (qds). we can find in the literature various works about this zero dimensional semiconductors. for example, montenegro et al. [5] applied the variational procedure in the effective-mass oaj materials and devices, vol 3 #1, 0504 (2018) – doi: 10.23647/ca.md20180504 mailto:e-mail@address mailto:e-mail@address mailto:e-mail@address a. chafai et al. znte/cdse type-ii cssqd under an external electric field approximation to calculate the ground state donor-binding energy and the density of states of donor in spherical gaas(ga,al)as qds, as functions of the qd radii and of the donor position. bose [6] found that the binding energy decreases as the dot dimension increases and as the impurity moves away from the center. it is also shown that the effect of the nanodot size and the donor position on the binding energy is more pronounced for dots of smaller sizes. marin et al. [7] investigated the ground state energy of excitons inside a micro-spherical crystallites with a finite height potential wall as a function of the particle radius in the strong confinement regime. they have demonstrated that the quantum dot cannot be modelled using an infinite barrier height potential in the strong confinement regime. other shapes of quantum dots have also been extensively studied essentially cylindrical qds [8-11], lens qds [12-14] and pyramidal qds [15-18].the effect of an external electric field on the ground-state energy of charge carriers inside quantum dot was also studied by several authors. using a variational method lien et al. [19] have investigated the correlation energy of hydrogen impurities in spherical and disc-like quantum dots with parabolic confinements submitted to an external electric field. he et al. [20] have applied a non degenerate and degenerate perturbation approach to calculate the correlation energies of the ground and three low-excited states of hydrogenic impurity inside a spherical parabolic-like quantum dot as a function of the confinement strength and the intensity of the applied electric field. ref. [21] presents a study of the ground state binding energy of an impurity inside quantum dots under external electric and magnetic fields. using the micro-photoluminescence spectroscopy, the problem of an exciton in a single ingan quantum dot was treated by robinson et al. [22]. they have found that the quantum-confined stark effect causes a shift in the exciton energy of more than 5 mev, accompanied by a reduction in the exciton oscillator strength. the shift has both linear and quadratic terms as a function of the applied field. dujardin et al. [23] performed a variational approach to investigate the behavior of an exciton confined in zno single quantum disk under lateral electric field. they have shown that the electric field shifts down the excitonic binding energies. in the last decade, semiconductors core/shell quantum dots attracted interest of several researchers owing to their improved properties [25-26]. according to the maximum of the valence band and the minimum of the conduction band is or isn’t in the same material we can distinguish three categories of semiconductors core/sell quantum dots [24], type-i, type-ii and reverse type-i. fig.1 gives an overview of the principal categories of core/sell quantum dots. due to the conduction and valence band profile of type-ii core/sell quantum dots, the overlapping of the electrons and holes wave functions is reduced. as a result, one carrier is mostly confined to the core, while the other is mostly confined to the shell. the energy gap in this category of core/shell material ( e g c / s ) is determined by the energy separation between the conduction band edge of one semiconductor and the valence band edge of the other semiconductor. e g c / s can be related to the conduction and valenceband energy offsets at the interface by the following equation [27]: e g c /s =e g c −v v =e g s −v c (1) where e g c and e g s are, respectively, the band gaps of semiconductors core and shell. in this case, emission is lower than the band gap of either semiconductor. as a result the emission color is shifted toward spectral ranges. in the present work, we are concerned with the calculation of the energy state 1s, (n=1, l=0, m=0), of one electron confined in core/shell quantum dot type-ii. for this purpose we firstly investigate the case with zero electric field afterwards, we turn up an electric field f⃗ parallel to the ( o⃗z ) axis. in the next section we introduce the theoretical formalism, while in section 3 we present our numerical results. figure 1: categories of semiconductors core/sell qd (a) type-i, (b) type-ii, (c) reverse type-i. the model and applied theory within the framework of the effective-mass approximation, applying the isotropic and non-degenerate parabolic approximations, taking into account the dependence of the electron effective mass on radius and assuming that the core and shell materials dielectric constants are sufficiently close to ignore the effects of induced surface polarization charges. the stationary shrödinger equation of a system consisting of an electron inside a core/shell spherical quantum dot submitted to an external electric field can be written as: [ d2dr2 +2r ddr +ki2− l (l+1)r2 +2me (r )ħ2 w ] χ nl (r )=0 (2) where the electron effective mass (the square of the wave vector ki 2 ) is assumed to be m1 ( 2m1 ħ2 (u e− ee10) ) in the core material and m2 ( 2m2 ħ2 ee 10 ) in the shell material, and w = -q f.r is the electrostatic energy. it is clear that the presence of the electric field makes the problem more complicated and does not admit any analytical solution, that is why we have applied a variational approach to determine the electron ground state energy, and by analogy to the problem of the quantum wells we chose as our variational wave function: χ10(r ) =ψ 10 ( r ).exp(−αr cos (θ)), (3) where α is the variational parameter, θ is the angle between the electron position vector and the z-axis and ψ 10( r) is the oaj materials and devices, vol 3 #1, 0504 (2018) – doi: 10.23647/ca.md20180504 a. chafai et al. znte/cdse type-ii cssqd under an external electric field exact wave function of the same system with zero electric field. accordingly the energy of the electron 1s under an external electric field is determined variationally by the following expression: ee 10=min α [ ⟨ χ 10(r)|h f |χ10(r )⟩ ⟨ χ10(r )| χ10( r)⟩ ] (4) where h f is the hamiltonian of the confined electron under an electric field. discussion of the results we present in this section the results of our numerical calculation performed for znte/cdse core/shell spherical quantum dot characterized by an electron effective mass mznte=0.15m₀ [28] ( mcdse=0.13m₀ [29]) in the core (shell) material. first of all, we start our analysis by the case with zero electric field. to this end, and in order to give a detailed investigation of the electronic behavior of an electron confined in our nanostructure we display, in figure 2, the energy ground state versus the core to shell radii ratio rc / rs for various inner radius values: rs = 5 nm, 15 nm, 20 nm, 40 nm, 50 nm, 70 nm. we can easily notice that the energy ground state undergoes a great change by changing the value of rc and rs radii. in more detail the energy ground state increases if the size of the nanostructure decreases and for a fixed total size of the nanostructure the energy decreases if the thickness of the shell material t s increases. we can also find out that the effect of the size of core material on the energy ground state is more pronounced for the small nanostructures. for example the effect of the core size can be easily noticed for small core/shell nanostructure even for a core to shell radius ratio neighboring 0.15 which is very small as compared with large core/shell nanodot in which this effect will manifest only for core to shell radius ratio practically higher than 0.6. this variation of energy vis-a-vis the dimensionality of the nanostructure is intimately related to the quantum confinement effect which is considered as a major feature of nanostructured semiconductors. because of this effect, researchers can widely and precisely control the electronic energy states of core/shell nanostructures, by the control of both rc and rs radius, which leads to a precise control of the optical transitions making them useful for many optoelectronic devices. the following provides a description of the influence of an external electric field on the electron ground state energy. for this purpose we plot, in figure 3, the energy ground state of an electron confined in core/shell spherical quantum dot versus core to shell radii ratio rc / rs for a fixed external radius value rs =5 nm and various electric field strength values: f=0 kv/cm and 900 kv/cm. we can notice that the effect of the electric field can be almost marginalized for small nanostructures which is in full agreement with the earlier works already existing in literature [30,31]. this can be attributed to the fact that the electron is strongly confined in the shell material in such a way that the distribution of the electron probability density remains symmetric ensuring to the system to keep practically a similar energy to that in the zero electric field. figure 2: the energy ground state of an electron inside a core/shell spherical quantum dot drawn versus the core to shell radii ratio r c/ rs for: f=0 kv/cm and rs = 5 nm (square symbol), 15 nm (circle symbol), 20 nm (up triangle symbol), 40 nm (down triangle symbol), 50 nm (left triangle symbol), 70 nm (right triangle symbol). figure 3: the energy ground state of an electron inside core/shell spherical quantum dot drawn versus core to shell radii ratio rc / rs for fixed external radius value rs =5 nm and various values of the electric field strength: f=0 kv/cm (square symbol), f=900 kv/cm (circle symbol). we report in figure 4(a) the variation of the electron energy ground state versus core to shell radii ratio rc / rs for fixed external radius value r s = 40 nm and various electric field strength values: f=0 kv/cm, 100 kv/cm and 600 kv/cm. in order to understand the behavior of the electron inside core/shell nanostructure under an external electric field we plot in figure 4(b) the stark shift (δe=e(0)-e(f)) versus core to shell radii ratio rc / rs for fixed external radius value rs =40nm and various electric field strength values: f=100 kv/cm and 600 kv/cm. oaj materials and devices, vol 3 #1, 0504 (2018) – doi: 10.23647/ca.md20180504 a. chafai et al. znte/cdse type-ii cssqd under an external electric field figure 4: (a) the energy ground state of an electron inside a core/shell spherical quantum dot drawn versus the core to shell radii ratio r c/ rs for fixed external radius value rs = 40 nm and various electric field strength values: f=0k v/cm(square symbol), f=100 kv/cm (circle symbol), f=600 kv/cm (up triangle symbol), (b) the stark shift versus rc / rs for fixed external radius value rs = 40 nm and various electric field strength values: f=100k v/cm(square symbol), f=600 kv/cm (circle symbol). we can see that the presence of the electric field perturbs the electronic states of the electron, therefore a modification of the electron energy and the electron probability density are assisted. indeed, the application of the electric field tends to move the electron probability density in the opposite direction of the applied electric field which leads to break the symmetry of the electron probability density, and as a result the energy is red-shifted. this effect is more pronounced for large nanostructures. that is explained by the fact that in large nanostructure the electron probability density has enough space to move in the opposite direction of the external electric field which lead, by breaking the symmetry of the electron probability density, to the diminution of the electronic ground state energy. in contrast, in small nanostructure case, the electron probability density is too 'tight' so the effect of the electric field is eclipsed by the geometrical confinement effect. conclusion in summary, we have presented the impact of the nanodot size and the external electric field on the electron ground state energy. it is worth remarking that our results are in excellent agreement with the works that already exist in the literature. we have also shown that there are a competition between the effect of confinement and the effect of electric field. moreover we have found that the application of an external electric field is an additional opportunity to control the energy of charge carriers inside nanostructures core/shell type-ii, which is very useful from the application point of view. acknowledgements: this work has been initiated with the support of urac: 08, the project ppr: (mesrsfc-cnrst) and the swedish research links program dnr348-2011-7264. the authors would like to thank all the organizations. references 1. t. pradeep, nano: the essentials understanding nanoscience and nanotechnology. tata mcgrawhill publishing company limited, 2007. 2. m. köhler and w. fritzsche, nanotechnology: an introduction to nanostructuring techniques. wiley-vch, 2007. 3. b rogers, j adam and s pennathur, nanotechnology: understanding small systems. crc press, 2015. 4. s thomas, n kalarikkal, a.m stephan, b. raneesh and a.k. haghi, advanced nanomaterials: synthesis, properties, and applications. apple academic press, 2014. 5. n. porras-montenegro, s.t. pérez-merchancano and a. latgé, j. appl. phys. 74 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and e. feddi, physica b 477 (2015) 100. 27. j. bang, j. park, j. lee, n. won, j. nam, j. lim, b. chang, h. lee, b. chon, j. shin, j. park, j. choi,k. cho, s. park,t. joo and s. kim, chem. mater. 22(2010) 233. 28. v.e. borisenko and s. ossicini, what is what in the nanoworld: a handbook on nanoscience and nanotechnology. wiley-vch verlag & co. kgaa, 2012. 29. s. adachi, properties of group-iv, iii--v and ii--vi semiconductors. john wiley & sons ltd, 2005. 30. i. essaoudi, b. stébé, a. ainane, phys. rev. b. 64 (2001) 235311. 31. f. dujardin, e. feddi, e. assaid, a. oukerroum, eur. phys. j. b 74 (2010) 507. oaj materials and devices, vol 3 #1, 0504 (2018) – doi: 10.23647/ca.md20180504 https://www.sciencedirect.com/science/journal/09214526 https://www.sciencedirect.com/science/journal/09214526 a. chafai et al. znte/cdse type-ii cssqd under an external electric field important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. 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optical properties. of pzn-pt nanoparticles thin layers for pv applications oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 p1 article type: conf.-conference paper (casamansun) optical properties of pzn-pt nanoparticles thin layer on ito glass for photovoltaic application r. ndioukane (1), d. kobor (1), l. motte (2), j. solard (3) (1) laboratoire de chimie et de physique des matériaux, assane seck university of ziguinchor, senegal (2) laboratory for vascular translational science, paris 13 university, france (3) centrale de proximité en nanotechnologies de paris nord, institut universitaire de technologie de villetaneuse, france corresponding author: r.ndioukane1532@zig.univ.sn received: 14 september 2018 / received in final form: 12 february 2019 / accepted: 15 february 2019 abstract: in this work, undoped and mn doped pb(zn1/3nb2/3)o3-4.5pbtio3 nanoparticles were dispersed in biopolymer and in mixed biopolymer + pentacene as active layer and deposited by spin coating on ito glasses. morphological, optical and electrical properties of these layers were investigated. sem images show the superposition of different deposited layers ito/tio2/pzn-pt-np-biopolymer on glass substrate with thicknesses of 1.600 µm, 1.505 µm and 1.765 µm respectively. the absorbance value in uv visible for pentacene layer increases from 75 % to 99 % while the transmittance for ito glasses diminishes from more than 80 % to 2 %. optical gaps of ito, tio2, pzn-pt nanoparticles are respectively 3.75 ev, 3.2 ev and 3.15 ev. pentacene deposition reduced the gap to 1.65 ev for undoped sample and 1.60 ev for the doped ones. intermediate gaps (2.3 ev and 2.6 ev for undoped sample and 2.15 ev and 2.7 ev for doped sample) were observed. photoluminescence performed between 450 nm and 750 nm confirms « these intermediate gaps ». keywords: perovskite, nanoparticles, thin film, optical properties, band gap cite this article: rémi ndioukane, diouma kobor, laurence motte and jeanne solard, oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 r. ndioukane et al., optical properties. of pzn-pt nanoparticles thin layers for pv applications oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 p2 introduction among all the solution-processed thin film optoelectronic material technologies investigated over the past 2 decades, organic–inorganic (or hybrid) methylammonium lead triiodide (mapbi3) perovskites have emerged as clear frontrunners with proof-of-concept high performance devices demonstrated for a broad range of applications [1-8]. the mapbi3-based photovoltaic devices have demonstrated constantly increasing power conversion efficiency (pce), which now exceeds 22% [9-10] and is steadily approaching that of single-junction monocrystalline silicon (c-si) solar cells. although the record for the highest efficiency perovskite solar cell was achieved using a mesoporous titania (tio2)-based architecture [10-12] photovoltaic devices employing a simple planar architecture are closing in with the highest reported efficiency of 20% [6, 13, 14]. despite this breakthrough, hybrid lead-halide perovskites are known to degrade due to moisture and heat, upon prolonged exposure to light and are prone to ion or halide vacancy migration, leading to unstable operation of photovoltaic devices. great efforts have been put forth for achieving highly efficient planar solar cells by exploring for potential ideal contact layers [15]. in addition, it is now realized that the next steps in advancing hybrid perovskitebased materials toward a viable photovoltaic technology will require simultaneously improving both the overall efficiency and also intrinsic stability. to overcome such difficulties, we oriented our research to inorganic pzn-pt perovskite materials with excellent and stable properties compared to the organic-perovskite ones. however, despite their excellent properties, one of the greatest difficulties to integrate widely such materials in electronic devices is to achieve them in thin films form because of their incongruent melting property. in this paper, undoped and mn doped pzn4.5pt nanoparticles were dispersed in biopolymer and in mixed biopolymer + pentacene as active layer and deposited by spin coating on ito glasses. after the successful deposition of the thin film, morphological, optical and electrical properties were investigated. experimental procedure the quality of the layers depends strongly on the state of the materials surfaces and their interfaces, whether organicorganic or metal-polymer. thus a chemical treatment of the ito substrate surface is necessary to eliminate the contaminating elements. for this, we combined the ultrasonic method with piranha to clean substrates. the piranha solution is composed of h2so4 96 % (30 ml) and h2o2 (10 ml). after cleaning, the different layers, namely titanium oxide (tio2), undoped and mn doped pzn-4.5pt nanoparticles dispersed in a biopolymer and pentacene were successively deposited by spin coating. in this study we used a natural biopolymer containing polysaccharides with short side chains. this polymer can take several conformations that allow it to adapt or intercalate depending on the environment. colloidal suspension of tio2 the titanium oxide used in this study is a finished product marketed by sigma-aldrich (cas number 13463-67-7). the suspension is obtained by grounding tio2 powder in a mortar and adding a few drops of acetic acid giving a white paste. the as prepared paste is deposited on ito glass substrate at room temperature using a spin coater midas 1200d at 3500 rpm with an initial acceleration of 5 seconds and an operating time of 2 min. pzn-pt nanoparticles thin film fabrication undoped and mn doped pzn-4.5pt single crystals synthesized by the flux method [16] were grounded in a mortar to obtain a very fine powder (tem characterizations revealed nanoparticles of the nanometer order and studies (not shown here) have confirmed that the population of spherical particles having a diameter of 30 nm was more representative). the grounded powder was dispersed in biopolymer solution. to obtain a homogeneous film, spin coating process was carried out at room temperature at 3500 rpm with an initial acceleration of 5 seconds and an operating time of 10 min. the biopolymer is used to disperse undoped and mn doped pzn-4.5pt perovskite nanoparticles but also as a hole-injecting layer through the organic layer/ito interface. secondly it serves buffer layer to prevent diffusion of oxygen and indium to active layer, these impurities can act as exciton recombination centers or photogenerated traps carriers. results and discussion sem images surface morphology was observed by using an electron beam lithography system pioneer raith model in c(pn)2 (paris 13 university). observation of film surfaces in a scanning electron microscope makes it possible to verify the homogeneity of films, grains shapes and aggregates as well as the qualitative analysis of layers. sem images of samples composed of ito/tio2/pzn-pt-npbiopolymer films (dkrn-ito2), ito/tio2/pzn-pt+1%mn-npbiopolymer (dkrn-ito4), ito/tio2/pzn-pt-npbiopolymer/pentacene (dkrn-ito7), ito/tio2/pznpt+1%mn-np-biopolymer/pentacene (dkrn-ito8) deposited at room temperature on glass substrates are shown respectively in figure 1. dkrn-ito2 and dkrn-ito4 (fig. 1a and 1b) shows a homogeneous, sparse and porous surface, showing white gray coloured non-regular agglomerated grains with an average size of 30 nm. dkrn-ito7 and dkrn-ito8 samples (fig. 1c and 1d), developed in the same conditions with the only difference of adding a pentacene layer, have uniform, compact and homogeneous slightly black surfaces. this suggests that pentacene leads to a coalescence of the grains by diffusion through the pores. the morphology of the surface is initially related to the energy of the particles. indeed, when the particle on the substrate acquires a great energy, it will have a large surface diffusion length. then, this allows it to reach the sites energetically favorable and thus to r. ndioukane et al., optical properties. of pzn-pt nanoparticles thin layers for pv applications oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 p3 complete the possible gaps, reducing the irregularities of the surface. in the other case, the particles deposited on the substrate in contact with the air having lost a large part of the energy, their diffusion length will be very short. therefore, the morphology of the surface will reflect a part of the morphology of the substrate but with greater irregularities due to the shading effect, and secondly the nature of the deposited material [17]. observation in scanning electron microscope in transverse mode, allowed us to see the disposition of the various deposited layers but also to determine their thickness. for example, in figure 2a showing the sem image in transverse mode of the dkrn-ito2 sample composed of the ito / tio2 / np-pzn-4.5pt-biopolymer layers, we obtained thicknesses of 1.600 μm, 1.505 μm and 1.765 μm respectively for ito, tio2 and np-pzn-pt-biopolymer. this allowed us to confirm the value of the thickness of the ito given by the supplier (1.600 μm). figure 1: sem images of thin film (a) dkrnito2, (b) dkrn-ito4, (c) dkrn-ito7 and (d) dkrn-ito8 figure 2: sem images in transversal mode (a) dkrn-ito2, (b) dkrn-ito4, (c) dkrn-ito7 and (d) dkrn-ito8 table 1: thickness values of different layers thicknesse (µm) ito tio2 biopolymer pentacene dkrn-ito2 1,600 1,505 1,765 dkrn-ito4 1,600 2,401 1,667 dkrn-ito7 1,600 1,709 1,680 1,431 dkrn-ito8 1,600 1,691 1,582 1,322 optical properties optical properties of thin films were investigated using an uvvisible spectrophotometer with an integrating sphere model lambda 950s in im2np (marseille). measurements are made with a pitch of 5 on a wavelength spectrum ranging from 250 and 1500 nm. transmittance and absorption typical transmission spectra obtained for the different deposited layers at room temperature are shown in figure 3a. for the ito reference sample composed of ito layer only, there is a strong transmission of more than 80 % throughout the visible band. this confirms the transmission value given by the supplier. this transmission decreases with the deposition respectively of tio2/np-pzn-4.5pt-biopolymere, tio2/np-pzn4.5pt+1%mn-biopolymer, tio2/np-pzn-4.5ptbiopolymere/pentacene and tio2/np-pzn-4.5pt+1 %mnbiopolymer/pentacene. for the different deposits, the general patterns of the spectra are similar. two transmission domains can be distinguished according to the wavelength: a domain (λ < 800 nm) characterized by high absorption and low transmission of the different layers, which corresponds to the absorption of the layer in question. a relatively high transmission domain for λ range of 800 1500 nm, it increases sharply and tends to values between 30 and 56 % for the dkrn-ito2 sample, 26 and 47 % for the dkrn-ito4 sample, 25 and 45 % for the dkrn-ito7 sample, 45 and 70 % for the dkrn-ito8 sample. authors in the literature, such as d. kobor [18] report transmission values of 25 and 45 % for wavelengths between 600 and 900 nm of pzn-4.5pt single crystals. this confirms the values obtained in this study, although we can also consider the influence of the organic layers of biopolymer and pentacene which tend to attenuate this transparency. in figure 3b, it can be seen that the addition of the pentacene layer greatly increases the absorption throughout the visible spectrum. it is deduced that r. ndioukane et al., optical properties. of pzn-pt nanoparticles thin layers for pv applications oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 p4 pentacene increases the absorption band in the visible (~ 90 %). indeed, pentacene is a semiconductor that absorbs well in the visible and authors like a. skaiky [19] have shown it. this is a good thing for photovoltaic applications. on the other hand, the biopolymer seems to have less influence on the absorption compared to pentacene. figure 3: (a) transmittance and (b) absorbance according to the uv-visible-nir wavelength for different samples determination of band gap to calculate the optical gap eg, we used tauc relation [20]. ( ) (1) n g h a h e    where a is a constant, hν is photon energy, eg is the allowed energy gap, n = ½ for allowed direct transition, α is the absorption coefficient and n = 2 for allowed indirect transition. thus, from the value of the absorption coefficient and by plotting the curve of (αhν)² as a function of the photons energy, we have determined the optical gap eg: it suffices to draw the slope in the region of absorption as shown in figure 4 and the intersection of this line with the abscissa axis (for αhν = 0) gives directly eg. the values found are shown in table 2. for the ito reference sample, the value of the gap found (3.75 ev) is in perfect correlation with that found by g. fatma-zohra [21] (3.80 ev). for the dkrn-ito2 and dkrnito4 samples, the gap remains high with values of 3.20 ev and 3.15 ev that can respectively correspond to the tio2 gap that is 3.02 ev according to schon [22] and pzn-pt gap equal to 3.04 ev according to he chong-jun [23]. pentacene deposition reduced the gap to 1.65 ev for the dkrn-ito7 sample and 1.60 ev for dkrn-ito8. we also note the presence of intermediate gaps (2.30 ev and 2.60 ev for dkrn-ito7 and 2.15 ev and 2.70 ev for dkrn-ito8). these intermediate gaps could be due to the heterogeneity of the layers (presence of tio2, nanoparticles of pzn-4.5pt undoped or doped mn, biopolymer, pentacene). these values could correspond respectively to the gap of the pentacene layer (1.65 and 1.60 ev), the combination of the biopolymer with pentacene (2.30 and 2.15 ev) and tio2 (2.60 and 2.70 ev). it appears from the results that pentacene tends to influence even the gap of the inner layers (tio2, nanoparticles and biopolymer) whose absorption is considerably reduced. the results are in perfect correlation with the curves of figure 3. figure 4: tauc plot curves of (x) ito, ( ) dkrnito2, ( ) dkrn-ito4, ( ) dkrn-ito7 and ( ) dkrn-ito8 r. ndioukane et al., optical properties. of pzn-pt nanoparticles thin layers for pv applications oaj materials and devices, vol 4 (1), 1502 (2019) – doi: 10.23647/ca.md20191502 p5 table 2: gap values of different samples samples eg1 (ev) eg2 (ev) eg3 (ev) ito 3,75 dkrn-ito2 3,20 dkrn-ito4 3,15 dkrn-ito7 1,65 2,30 2,60 dkrn-ito8 1,60 2,15 2,70 photoluminescence to confirm the effect of pentacene on the reduction of the optical gap, we investigate photoluminescence on samples dkrn-ito7 and dkrn-ito8. figure 5 shows the photoluminescence (pl) spectra obtained. we observe a first emission peak at 2.3 ev and a second peak at 2.5 ev for dkrn-ito7 while for dkrn-ito8 we have a peak at 2.2 ev and another at 2.6 ev. this confirms the values of the intermediate gaps found by the tauc method. photoluminescence was performed between 450 nm and 750 nm. this does not allow observing the peak of 1.6 ev revealed by the method of tauc. indeed, this peak would probably appear in the infrared. figure 5: photoluminescence of (a) dkrn-ito7 and (b) dkrn-ito8 conclusion pzn-4.5pt nanoparticles thin layers were successfully prepared using a biopolymer. sem images revealed the superposition of different deposited layers. it shows uniform, compact and homogeneous surface with deposition of pentaconene layer. optical characterization by transmittance and absorbance measurements allowed us to observe the influence of the layers on absorption and optical gap. it also made it possible to follow the evolution of the gap according to the nature of the deposited layer. pentacene has been very successful in improving photovoltaic properties. acknowledgements: this work is supported by agence universitaire de la francophonie (auf). complementary informations on authors: rémi ndioukane: r.ndioukane1532@zig.univ.sn, research gate (rémi ndioukane), linkedin (remi ndioukane) diouma kobor: dkobor@univ-zig.sn, research gate (diouma kobor) laurence motte: lmotte2009@hotmail.fr, research gate (l. motte) jeanne solard: jeanne.solard@iutv.univ-paris13.fr, research gate (jeanne solard) references 1. m. m. 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(see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p1 article type: conf.-conference paper (casamansun2018) arma model for short-term forecasting of solar potential: application to a horizontal surface on dakar site a. mbaye1, m.l. ndiaye1, d.m. ndione2, m. sylla1, m.c. aidara1, m. diaw2,1, v. traoré2, a. ndiaye1 and p.a.s. ndiaye1 1international center for training and research in solar energy /esp/ucad, bp 5085, dakar-fann, senegal. 2 hydraulic and fluids mechanics laboratory (hfml), department of physics, faculty of sciences and technology, cheikh anta diop university (ucad), bp 5005, dakar-fann, senegal. corresponding author : amy1.mbaye@ucad.edu.sn received: 12 september 2018 / received in final form: 04 february 2019 / accepted: 11 march 2019 abstract: this paper presents a model for short-term forecasting of solar potential on a horizontal surface. this study is carried out in to the context of valuing of energy production from photovoltaic solar sources in the sahelian zone. in this study, autoregressive moving average (arma) process is applied to predict global solar potential upon 24 hours ahead. the arma (p, q) is based on finding optimum parameters p and q to better fit considered variable (sunshine). data used for the model calibrating are measured at the station of ecole supérieure polytechnique of dakar. records are hourly and range from october 2016 to september 2017. the choice of this model is justified by its robustness and its applicability on several scales through the world. simulation is done using the rstudio software. the akaike information criterion shows that arma (29, 0) gives the best representation of the data. we then applied a white noise test to validate the process. it confirms that the noise is of white type with zero mean, variance of 1.252 and p-value of about 26% for a significant level of 5%. verification of the model is done by analyzing some statistical performance criteria such the rmse =0.629 (root mean squared error), the r² = 0.963 (coefficient of determination), the mae=0.528 (mean absolut error) and the mbe=0.012 (mean bias error). statistics criteria show that the arma (29,0) is reliable;then, can help to improve planning of photovoltaic solar power plants production in the sahelian zone. keywords: arma, stochastic, forecasting, solar radiation, dakar. cite this article: a. mbaye, m. l. ndiaye, d. m. ndione, m. sylla, m. c. aidara, m. diaw, v. traoré, a. ndiaye, p. a. s. ndiaye,oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 mailto:corresponding%20author%20:%20amy1.mbaye@ucad.edu.sn a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p2 introduction senegal has significant potential for enhancing solar resource (pv and thermal) with 3000 hours of sunshine per year and an average of global irradiation about 5.8 kwh / m2 / day. solar photovoltaic market is growing in the world in general particularly in africa. currently there is a proliferation of photovoltaic solar power plants in senegal. integration of these intermittent sources on the senelec electricity system causes many problems on planning and maintaining the consumption/production balance. such difficulties are stochastic behaviour of the renewable energy sources related. to overcome such difficulties, forecasting can be considered. thus, prediction of solar potential can be a substantial contribution in renewable energy production. it allows to evaluate the intermittent energies rate on the distribution network, in order to mitigate unbalances risks. indeed, forecasting production of intermittent energies allows anticipating on the availability of the production sources and facilitating the network management. it is inspired by the stochastic behaviour of the atmospheric situations that are deterministic factor for the solar potential the earth surface. considering above uncertainty sources, operators in solar power plants fields need appropriate tools to predict the energy production and availability. in the literature, stochastic prediction of the solar potential on horizontal surface can be done either at long-term scale [1, 2] or short-term scale [4, 3]. thus, this study has been done to contribute to the search for reliable prediction methodologies of photovoltaic power. four categories of models exist in the literature [5, 6, 4]. among these models, we have linear, nonlinear models, probabilistic models and models of naive types. an autoregressive moving average (linear model) process is used to forecast solar potential at dakar. we have chosen to work with the model autoregressive moving average because of its robustness and applicability on several sites in the world on different forecast horizons [7, 28, 9, 10, 11]. arma model is based on researching optimal fit parameters p and q for better representation of considered time series (solar radiation). our contribution in this field of study focuses on implementating reliable solar potential prediction model that able to predict the senelec’s capacity of production for 24 hours forecast horizon and can be used as a decision support tool for planning and managing photovoltaic solar power plants in senegal and surrounding. section2 describes the methodology and tools used to reach our target, section 3 presents results of issues form forecasting model and interpretation. the last section is devoted to the conclusion and perspectives. materials and methods 1. presentation of study area dakar is located in the extreme west of the cape verde peninsula, at the edge of the atlantic sea, between latitude 14° 75 n and longitude -17.33 ° w with an average altitude of about 16m (figure1). it contains some meteorological stations including one of measuring of the international center for training and research in solar energy (cifres) of the polytechnic high school of cheikh anta diop university (ucad) of dakar. this station measures global, direct and diffuse solar radiation, ambient temperature, relative humidity, rainfall, wind speed and wind direction. dakar covers an area of 550 km². its climate is of tropical type characterized by alternation of two seasons: a very long and dry season on one hand (9 months) and a short and rainy season on the other (3months). the dry season is characterized by the predominance of the harmattan dry wind that is neither hot nor cold; the rainy season is characterized by the hot and moist monsoon wind. temperatures vary according to the seasons. a low range of diurnal temperature caused by the maritime wind exchanges composed of a steady wet and fresh wind blowing especially in the dry season explaining the leniency of temperatures at dakar in comparison to that inside the country. dakar has a relatively mild climate, due to prerogatives of its geographical position and oceanic influences determining special characteristics of this region. rainfall in this area usually occurs between july and october. the rainy month of this area is august. annual rainfall is estimated about 500 mm. within variation of the air moisture average depends on the temperature and hygrometric characteristics of the one. average of the relative humidity rate in the site is close to 95%, especially during the rainy season between august and september. lower values of relative humidity are observed during the dry season in which the time evaporation remains significant. in this work, we used solar radiation data from cifres station. the data series runs from october 1st, 2016 to september 30th, 2017 and measurements are made every one hours. a campbell scientific model cr800 datalogger is used. figure1: location of dakar in senegal area a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p3 2. autoregressive moving average process (arma) in the literature, some authors [9, 28] argue that autoregressive moving average process (arma) seems adequate for fitting solar radiation time series. moreover, the arma process can be used to forecast time series. running such processes is based on observations in order to determine adequate stochastic model that fit the studied variable. in time series analysis, wold proposed in 1938 a decomposition of time series into components referred to as deterministic component (trend and periodic component) and stochastic one [18]. deterministic component can be computed through known physical laws and steady mathematical schemes. the stochastic component can’t be exactly determined by known physical and mathematical lows due to its random feature, then are modelled through stochastic processes. stochastic processes have also been referred to as yule processes (infinite linear combination process that cannot be expected). in 1954, wold defined from a random process a linear model composed of an autoregressive process noticed by ar and a moving average one noticed by ma [16]. combination of both processes gives the arma process. an ar process fits a time series through a linear function of its past values while the ma process smooth fluctuations around a mean of a time series. in addition, the trend component is represented by some weighted mean based on the past values of the time series. elsewhere, the residual is composed of strictly random part of the raw time series noticed by i  . arma process is characterized by following equation: jt q j jtt p i it xx        1 1 1 (1) 𝜑𝑖 : parameter of autoregressive process 𝜃𝑖 : parameter of the moving average process (𝜃0 =1) 𝜀𝑖 a residual. 3. application of the arma process (p, q) on the studied site. 3.1dickey-fuller test to check for non-stationarity of recorded data, a general function noticed by "adf.test" has been used. the function is applied using the package “tseries" of the r software. among tests, one can cite the classical dickey-fuller test, the augmented dickey-fuller test and the phillips-perron test. for above tests, the null hypothesis is non-stationarity of the time series [15]. in this study, the augmented dickey-fuller test is used to verify non-stationarity of the solar radiation. 3.2 validation of the arma process (p, q) in the determination p and q orders of the arma (p, q) process, the autocorrelation and partial autocorrelation functions can be used. through above functions, we can select several possible orders p and q. the aic criterion is used to select the optimal order of p and q. validation of the process includes an examination of the estimated coefficients and by analysing the residue, (the estimated residues must follow a white noise process). indeed, analysis of residual is based on the autocorrelation, box, and pierre tests [12, 19]. this test applied to the residual to validate whether residual is "white noise" (zero mean, fixe and uncorrelated variance).we use the box.test function of the r software to perform this test. in practice, this function gives a p-value for the applied test. the null hypothesis h0 of white noise is accepted, when the p-value is greater than 5% and is rejected otherwise. 4. information criterion we study the specific criteria of the stochastic models such the akaike’s aic (an information criterion) criterion and the bayesian one (bic) to check for optimum orders of the model. among these criteria, we chose to work with the akaike criterion. indeed, this criterion of akaike or aic is based on researching optimum parameters p and q [16]. the best of the arma models (p, q) is the model that minimizes the statistic determined in priori. this criterion aic is described follow the eq. (2): t qp qpaic )(2 ˆlog),( 2    (2) )²( 1 ˆ 0 2    n t tt t  0 t  5. model performance criteria in forecasting purposes, several methods are available for verifying the performances and the reliability of the used model [17, 22, 14]. in this paper, the root mean squared error (rmse), the mean absolute error (mae), the mean bias error (mbe) and the coefficient of determination (r²) are used to evaluate issues of the model. the mean root error (rmse) representing the standard deviation between predictions and observations is commonly used. the rmse is given by the following equation. 2 1 1 )²)ˆ( 1 ( i n t i pp n rmse    (3) the mean absolute error (mae) measures the difference between predictions and observations and is given by eq. (4) 1 1 1 n mae p p n    (4) mean bias error (mbe) is the estimation of algebraic difference between forecasted time series and observed one. a positive value of mbe means that predicted values overestimates expectations, while a negative value characterize an underestimation. the mbe value is calculated using the following equation. )ˆ( 1 1 i n t i pp n mbe    (5) a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p4 the coefficient of determination (r²) indicates how the regression curve adjusts the data or how variation in time of forecasts fits observations. r² is calculated using eq. (6)     n i i n i ii p pp r 2 2 2 )( )ˆ( 1 (6) results 6. autocorrelation partial autocorrelation tests fig.2 and fig.3 present respectively the plots of the partial autocorrelation and autocorrelation functions of the solar potential recorded at the dakar site. this afc curve shows oscillatory behaviour and the deterministic feature of the solar potential. indeed, the bars of the afc curve go beyond the confidence interval, so the data are random. the afc curve maintains periodic (deterministic) behaviour of a time series if it exists. in addition, the augmented dickey-fuller test has been carried out for this purpose through the r software. results show that data are random with a p-value of 0.01 for a significant level of 5% (thus greater than 5%). the null hypothesis for this test is the non-stationarity of the time series. figure2: autocorrelation function of the solar potential. figure3: partial autocorrelation function of the solar potential. 7. calibration of the arma model to determine the order of the arma process, the aic information criterion has been used. according to the test, the retained orders are of 29 for p and 0 for q with a variance equal to 1.252. then, we find that an arma process (29, 0) fits better the data on dakar site according to the aic information criterion. residual is of zero mean (white noise) of which statistical characteristics are presented in table1. 8. noise validation statistic characteristic of the noise from the arma (29, 0) in the calibrating period (october 2016 to september 2017) are presented in table 1. results show residual is white noise, then retained orders can be used to predict the solar potential for 24 hours forecast horizon on the dakar site. in addition, the boxpierce test has been applied to the data in order to confirm randomness of the residual. performed test has a p-value of about 0.26 at significant level of 5%. then, the null hypothesis of randomness is accepted. table1: statistical characteristic of the residual. site residual mean var p-value cifres/esp 𝜀 0 1.252 0.26 figure4: autocorrelation function of the residual from applied arma (29, 0) at the dakar site. 9. study of the forecast quality table 2 shows performances of the arma (29, 0) for 24 hours forecast horizon. the coefficient of variation between observations and forecasts is about 0.963 close to 1. this means that the forecasts are well representative of the observations. the mean bias error (mbe) used to predict solar potential at 24 hours time horizon is about 0.012. the positive value of the mbe means that the model overestimate solar potential in the study area. the root mean squared error (rmse) is equal to 0.629, accordingly the model is acceptable because of reduce rmse. in a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p5 a same way, the mea of which value is about 0.528 confirms the reliability of the model. globally, analysis of the performances criteria confirms the reliability of the arma (29, 0). then, the model can be used to predict the solar radiation for 24 hours forecast horizon one the dakar site. table 2: performances of the prediction model arma (29, 0). rmse mbe mae r² 0.629 0.012 0.528 0.963 figure5: evolution of measured and predicted data of the study area. discussion according to the tests carried out, the selected orders are p = 29 and q = 0. it is found that an arma (29, 0) reproduces the data of the dakar site better according to the akaike information criterion (aic). the box-pierce test was applied to check the randomness of the noise. it confirms that the noise is white with zero mean, variance of 1.252 and p-value of about 26% above the 5% threshold. the model accuracy is studied by calculation of the rmse = 0.629 (root mean squared error), the r² = 0.963 (coefficient of determination), the mae = 0.528 (mean absolute error) and the mbe = 0.012 (mean bias error). these performance criteria confirm well the reliability of the arma (29, 0) in 24 hours ahead forecasting of the solar potential of the site of dakar. other similar work has already been carried out as part of the prediction of solar potential [23, 24, 7, 25, 27]. in a. mbaye and al., (2018), discrete kalman filter model is applied at the dakar site (senegal); results show very good performance (rmse = 0.048 and r ² = 0.99) for 20 minute forecast horizon. m. willy and al., (2018) applied a multi-layer perception (pmc) model at the gandon (senegal) site. the results also show very good performance (rmse = 0.03 and r ² = 0.99) for 10 minute forecast horizon. in c. voyant and al., (2013), used an arma(1,0) to predict the global solar radiation at several mediterranean sites with the best mean annual of rmse standardized equal to 19.4% on the site of ajaccio and 16% on marseille. in m. y. sulaiman and al., (1997), applied the box-jenkins approach to daily solar radiation from four different locations in malaysia. they removed the deterministic component using fourier analysis and modelled the stochastic component modeled using arma model. for this case of study, the residuals are better described by arma (2, 0). in as’ad. mohamad, (2012) works toward finding the best model for predicting peak of electricity demand for up to seven days in australlia considering time series upon one year. four autoregressive integrated moving average (arima) models have been compared for. results show that, the arima model calibrated using the data for december 2010-may 2011 is the best (rmse = 369.678) in comparison to the arima model calibrated from september 2010 to may 2011 (rmse = 370.735). in this paper, we confirm that the arma (p, q) model is applicable on different spatio-temporal scales. in addition, the results almost show statistical similarity between studies. globally, one can retain that the arma (p, q) can give very good performance and can be applied on various regions with different climates around the world. this study can help to improve the planning of photovoltaic solar power plants production in the sahelian zone and in the sub region. conclusion this study focuses on short-term solar potential prediction on a horizontal surface at dakar. an arma (p, q) model was applied to the data measured on dakar (senegal) site for 24 hours forecast horizon solar potential prediction purpose. arma model is performed on the basis on finding optimum parameters p and q that better fit data (sunshine). non-stationarity of the time series is first checked applying the dickey-fuller test. it shows that data are random with a p-value of about 0.01% for significance level of 5%. the akaike information criterion was used to determine the orders of the arma process. retained parameters are p=29 and q=0.the box-pierce test was used to test the residual. it found that residual series are white noise for significance level of 5% with zero mean, variance of 1.252 and a p-value of 26%. verification of the model is done by analyzing some statistical performance criteria such the rmse = 0.629 (root mean squared error), the r ² = 0.963 (coefficient of determination), the mae = 0.528 (mean absolut error) and the mbe = 0.012 (mean bias error). statistics criteria show that the arma (29, 0) is reliable. this model can be used as a decision support tool for planning and managing photovoltaic solar power plants in senegal and surrounding. we projected to apply same arma model in other tropical and intertropical areas in comparison purpose. a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p6 complementary informations on authors: amy mbaye: e-mail and research gate: amy1.mbaye@ucad.edu.sn ; orcid and linkedln profiles: amymbaye86@yahoo.fr. didier maria ndione: e-mail, research gate, orcid and linkedln profiles: didiermaria.ndione@ucad.edu.sn. references 1. a. k. yadav and s. s. chandel, solar radiation prediction using artificial neural network techniques, sustain energy, vol.33, p 772 (2014). 2. m. ikhsan, a. purwadi, n. hariyanto, n. heryana and y. haroen, study of renewable energy sources capacity and loading using data logger for sizing of solar-wind hybrid power system, procedia technol, vol.11, p 1048 (2013). 3. h. madsen, h. a. nielsen and t. s. nielsen, a tool for predicting the wind power production of offshore wind plants, proceedings of the copenhagen offshore wind conference & exhibition (2005). 4. a. mellit, a. pavan and v. lughi, short-term forecasting of power production in a largescale photovoltaic plant, solar energy, vol.105, p 401 (2014). 5. p. brockwell and d. ra, time series: theory and methods, springer series in statistics, second edition (2006). 6. j. d. hamilton, times series analysis, one of princeton university press's notable centenary titles, hard over (1994). 7. c. voyant, c. paoli, m. muselli and m. l. nivet, multi-horizon solar radiation forecasting for mediterranean locations using time series models, renew subtain energy, vol.28, p 4452 (2013). 8. a. zaharim, a. m. razali, t. p. gim and k. sopian, time series analysis of solar radiation data in the tropics, european journal of scientific research, vol.25, p 672 (2009). 9. j. boland, time series and statistical modelling of solar radiation, recent advances in solar radiation modelling, viorel badescu (ed.), springer verlag, p 283 (2008). 10. m. david, f. ramahatana, p. j. trombe and p. lauret, probabilistic forecasting of the solar irradiance with recursive arma and garch models, solar energy, elsevier, vol.133, p 55 (2016). 11. c. benard, e. boileau and b. guerrier, modeling of global solar irradiation using arma processes: application to low-time (hourly) prediction, with a view to establishing optimal control in the habitat, revue phys,vol.20,p 845 (1985). 12. g. e. p. box and david a. pierce, distribution of residual autocorrelations in autoregressive integrated moving average time series models, journal of the american statistical association, vol.65, p 1509 (1970). 13. c. join, m. fliess, c. voyant and f. chaxel, solar energy production: short-term forecasting and risk management, ifac papers online, vol.49 p 686 (2016). 14. c. voyant, prediction of time series of global solar radiation and photovoltaic energy production from artificial neural networks, thesis, university of corsican-pascal paoli doctoral school environment and society,chapter2, p 87 (2011). 15. r. davidson and j. g. mackinnon, report that the phillips perron test performs worse in finite samples than the augmented dickey–fuller test, journal of economic dynamics and control, vol.12, p 297 (2004). 16. t. fang and r. lahdelma, evaluation of a multiple linear regression model and sarima model in forecasting heat demand for district heating system, applied energy, vol.179, p 544 (2016). 17. h. jiang, y. dong and l. xiao, a multi-stage intelligent approach based on an ensemble of two-way interaction model for forecasting the global horizontal radiation of india, energy conversion and management, vol.137, p 142 (2017). 18. h. wold, a study in the analysis of stationary time series, j. n. journal of the royal statistical society, vol. 102, p 295 (1939). 19. g. m. ljung and g. e. p. box, on a measure of lack of fit in time series models, biometrika vol.65, p 297 (1978). 20. m. lazzaroni, s. ferrari, v. piuri, a. s. salman, l. cristaldi and m. faifer, models for solar radiation prediction based on mailto:amy1.mbaye@ucad.edu.sn mailto:amymbaye86@yahoo.fr mailto:didiermaria.ndione@ucad.edu.sn https://scholar.google.com/citations?user=3s3hew8aaaaj&hl=fr&oi=sra https://scholar.google.com/citations?user=gsikv-aaaaaj&hl=fr&oi=sra https://scholar.google.com/citations?user=09kxe5yaaaaj&hl=fr&oi=sra https://www.researchgate.net/profile/russell_davidson https://www.researchgate.net/profile/james_mackinnon a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p7 different measurement sites, elsevier, measurement, vol.11, p 037 (2015). 21. s. monjoly, r. calif, m. andre and t. soubdhan, prediction tools for wind power generation: application to optimize coupling to electricity distribution networks, university of the west indies and guyana december, (2013). 22. t. soubdhan, j. ndong, h. o. baba and m. thangdo, a robust forecasting framework based on the kalman filtering approach with a twofold parameter tuning procedure: application to solar and photovoltaic prediction, solar energy, vol.131, p 246 (2016). 23. a. mbaye, j. ndong, m. l. ndiaye, m. sylla, m. c. aidara, m. diaw, m. f. ndiaye, p. a. ndiaye and a. ndiaye, kalman filter model as a tool for short-term forecasting of solar potential: case of the dakar site, edp science, vol.57, p 2267 (2018). 24. w. m. nkounga, m. f. ndiaye, m. l. ndiaye, o. cisse, m. bop and a. sioutas, short-term forecasting for solar irradiation based on the multi-layer neural network with the levenberg-marquardt algorithm and meteorological data: application to the gandon site in senegal, 7th international conference on renewable energy research and applications, ieee, p 869 (2018). 25. y. m. sulaiman, o. w. m. hliang and m. a. wahab, modeling of solar radiation in time series domain, renewable energy, vol.11, p 97 (1997). 26. m. a. alghoul, m. y. sulaiman, b. z. azami and m. a. wahab, modeling of solar radiation in time series domain, international energy journal, vol.7, p 261 (2006). 27. m. as’ad, finding the best arima model to forecast daily peak electricity demand, proceedings of the fifth annual applied statistics education and research collaboration (asearc) conference papers, university of wollongong australia (2012). https://www.sciencedirect.com/science/article/pii/s0038092x16001444#! https://www.sciencedirect.com/science/article/pii/s0038092x16001444#! https://www.sciencedirect.com/science/article/pii/s0038092x16001444#! https://www.sciencedirect.com/science/article/pii/s0038092x16001444#! a. mbaye et al, arma model for short-term forecasting of solar potential oaj materials and devices, vol 4 (1), 1103 (2019) – doi: 10.23647/ca.md20191103 p8 o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 article type: a-regular research paper first principles calculations of electronic and optical properties for mixed perovskites: ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) o. tahiri, s. kassou, r. el mrabet & a. belaaraj laboratoire physique des matériaux et modélisation des systèmes, cnrst-urac08, département de physique, faculté des sciences, université moulay ismail, 50000-meknes, maroc. corresponding author: a.belaaraj@fs-umi.ac.ma received: 23 february 2018 / received in final form: 20 april 2018 / accepted: 23 april 2018 abstract: the effect of ca and sr-doping on the structural electronic and optical properties of the cubic ba1xcaxtio3 and ba1-xsrxtio3 (x=0.4, 0.6) mixed crystals was investigated using first-principles calculations based on density functional theory (dft). the calculated band structures based on the optimized geometry of the cell for the solid solutions show an indirect band gap character at m-points, with low energy dispersion along height symmetry directions in the brillouin zone. the band gaps increase with ca and sr concentrations. the total and partial densities of states were analyzed to examine the contribution of different orbitals to the maximum of valence band and the minimum of the conduction band. the optical properties such as reflectivity, energy loss, refractive index and extinction coefficient were studied. keywords: dft calculations, band gap, density of state, optical properties. introduction the interest carried in perovskites (atio3) and their dielectric properties did not stop growing. the technico-economics requirements, directed essentially to the miniaturization and the production at a lower cost, are at the origin of the discovery of new successful materials. the most recent fields of application are the ones of the aeronautics, the antennas guides of waves, filters, satellite links, the processing and storage of the information [1-3].the titanate of barium is certainly the material most studied among compounds ferroelectrics [4] due to their chemical and mechanical stability. at room temperature it exhibit a ferroelectric properties in tetragonal phase with space group p4mm, over this temperature the batio3 becomes a cubic phase pm-3m. the integration of ions isovalents as, ca2+, sr2+ and pb2+ in ba sites and the substitution of tetravalent ions ti4+ by zr4+, sn4+ and hf4+ can influences the properties of the batio3, such as the phase transition temperature and tailor these properties to performance requirements. the investigations in this domain were mainly concentrated on the systems (ba, sr)tio3 characterized by high dielectric constant. increasing content of sr2+on the ba2+ site, leads to decrease the temperature transition with an expansion of the constant dielectric, low leakage current, low dielectric dispersion against frequency and can be implanted in electroluminescent devices as a high transparency insulator layer [5]. the major problems of these compounds seem of dielectric losses and its relative variation, according to the temperature [6,7]. in order to reduce this inconvenient, we have considered the good dielectric properties and the relaxor nature of (ba, ca) tio3 materials which are expected as alternative candidates fortunable microwave dielectric materials with low dielectric loss and temperature dependence. the aim of this work is to carry out the electronic and optical properties; o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 such as reflectivity, energy loss, refractive index and extinction coefficient of ba1-xcaxtio3 and ba1-xsrxtio3, where x = 0.4 and 0.6, using the first principle calculations. computation detail we used for our calculations abinit ab initio software package [8-10] which is based on the density functional theory (dft), using plane wave pseudo potential formalism, in order to obtain response function calculations [11-13], computing are performed by the generalized gradient approximation (gga) with the fritz-haber-institute (fhi) pseudopotentials and perdew-burke-ernzerh of exchange correlation [14], energy cutoff of the electronic wave functions was expanded in plane waves at 950 ev, which are well converged. the monkhorst pack mesh scheme [15] k-points grid sampling was set at 4 x 4 x 4 to perform the irreducible brillouin zone integrations. the initial crystal data of batio3 in cubic structure with the space group pm-3m reported in the literature [16], were used as a starting point. the optimized structure and minimum energy lattice constants of the relaxed cubic unit cell were initially computed. the electronic and optical properties were calculated for the equilibrium structures. structural and electronic properties the calculated a-cell parameters are listed in table1. it is apparent that the a-lattice parameter decreases with doped amount of the sr and ca elements, this result is due to the lower ionic radius value of sr and ca compared to ba in the pure compound batio3. the values obtained for the pure batio3, srtio3 and catio3 crystals are in perfect agreement with other theoretical and experimental values [17-19]. table 1: calculated a-cell parameter and band gap energy of ca and sr-substitued batio3 batio3 cell parameter(a) (å) band gap eg (ev) 4.123 4.008 [17] 4.011 [16] exp 2.150 2.200 [23] ahuja 3.270 [26] exp ba0.6ca0.4tio3 ba0.4ca0.6tio3 catio3 4.106 4.075 3.964 3.851[17] 3.895[18] exp 2.201 2.263 2.433 2.780 [24] 3.500 [27] exp ba0.6sr0.4tio3 ba0.4sr0.6tio3 srtio3 4.092 4.064 3.984 3.907 [17] 3.890 [18] exp 2.222 2.266 2.380 2.200 [23] 3.250 [28] exp the calculated band structures along the high symmetry directions in the first irreducible brillouin zone, in the same scale from -6 ev to 20 ev for all crystals are shown in figure1; these bands look very similar and agree with band structure published, previously in the literature [17-23]. the nature of the crystal components and the electrostatic interactions affect the dispersion of the band structure. the top of the valence band, for ba0.6ca0.4tio3, ba0.4ca0.6tio3, ba0.6sr0.4tio3 and ba0.4sr0.6tio3 compounds, is located at m-points. the highest valence states at m-points appear only about 0.1 ev after the highest states at г points. the bottom of the conduction band is located at г-points. the lowest valence states at гpoints appear only about 0.1 ev after the highest states at x-points. the analysis of all directions reveals medium energy dispersion along г-m and m-x directions, while a lower dispersion is present along г-x, equivalent to the revolution axis. figure 1: calculated band structure: a) ba0.6ca0.4tio3, b) ba0.6sr0.4tio3, c) ba0.4ca0.6tio3, d) ba0.4sr0.6tio3 the figures reveal also that all compounds exhibit an indirect band gap transition. from table 1, we can see that the energy gap increases by increasing the ca and sr content. this effect of doping is in agreed with previous works [19,20]. the high band gap value is found to be 2.266 ev for ba0.4sr0.6tio3. the calculated values for the pure batio3, srtio3 and catio3 (figure 2) are found to be 2.15 ev, 2.380 ev and 2.433 ev respectively, which are in reasonable agreement with other theoretical data [21-24]. while they are slightly lower than available experimental results [26-28]. these results are well known by underestimate the band gap presented by dft calculations [29-31]. figure 3 shows plots of the total (tdos) and partial (pdos) densities of states for ba0.4ca0.6tio3, ba0.4sr0.6tio3, ba0.6ca0.4tio3 and ba0.6ca0.4tio3. a low displacement of the density is observed in conduction band to high energy as function of ca and sr concentration. the analysis of tdos and pdos variation versus photon energy reveals that the maximum of the valence band is occupied by the orbital o-2p, and the minimum of the conduction band is occupied by the orbital ti-3d. from -4 ev to -1 ev, appears the mixed contribution of o-2p, ti-3d and a low contribution of ba-6s, ca-4s and sr-5s orbitals. beyond 6 ev, a low contribution of o-2s, o-2p, ti-3s, ti-3d, ba-5p, ba-6s, ca-3p, ca-4s, sr-5s and sr-4p orbitals appears too. optical properties the real and imaginary components of the dielectric function are used to calculate the optical properties of ba1-xcaxtio3 and ba1-xsrxtio3 solid solutions, such as the reflectivity r (ω), energy loss l(ω), refractive index n (ω )and extinction coefficient k (ω) from the following relationships [22]: where ε1(ω) and ε2(ω) are the real and imaginary parts of the frequency         1/2 22 1 2 1     ωε+ωε+ωε=ωn 12         1/2 1 22 1 2 1      ωεωε+ωε=ωk 2       1 1 2 +ωε ωε =ωr       22 2 1 2)( ωεωε ωε ωl   o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 figure 2: total and partial densities of states of the pure batio3, catio3 and srtio3 figure 3: total and partial densities of states: a) ba0.6ca0.4tio3, b) ba0.6sr0.4tio3,c) ba0.4ca0.6tio3, d) ba0.4sr0.6tio3 o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 complex dielectric function ε(ω)= ε1(ω)+iε2(ω), which are calculated from the kramers-kronig relationship and the momentum matrix elements between the occupied and unoccupied wave functions[32-33]. the calculated reflectivity r(ω) of the studied compounds, in the energy range from 0 to 30 ev, are shown in figure 4 for the energy values less than 1 ev and above 22 ev, the reflectivity is lower than 17% for all compounds, which indicates that these compounds are transparent, and expected to be poor electrical conductors at this range. figure 4: variation of reflectivity r(ω) versus photon energy: a) ba0.6ca0.4tio3 and ba0.6sr0.4tio3b) ba0.4ca0.6tio3 and ba0.4sr0.6tio3 the curves show that the first optical critical point (a1) of the reflectivity occurs at 3.271 ev and 3.790 ev for ba0.6ca0.4tio3 and ba0.4ca0.6tio3, and at 3.907 ev and 3.790 ev for ba0.6sr0.4tio3 and ba0.4sr0.6tio3. these points give the threshold for indirect optical transitions between the valence band (vb) and the conduction band (cb), which are known as the fundamental absorption edge due to the interaction between the o-2p and ti-3d states [34-35]. after this threshold energy (first critical point), the curves decrease towards another critical point a2, this peak is caused by the interaction between the o-2p and higher-energy conduction bands, whereas the peak a3 is due to the interactions between ti-3d and o-2s. we can observe that the first peaks resulting from transition between o-2p and ti-3d are dominant. figure 5: variation of energy loss l(ω) versus photon energy: a) ba0.6ca0.4tio3 and ba0.6sr0.4tio3b) ba0.4ca0.6tio3 and ba0.4sr0.6tio3 as shown in figure 5, the energy loss gives a sharp peak at 21 ev, which is related with the reduction of reflectivity r(ω), and gives the plasma frequency ωp, according to drude theory [36]. figure 6: variation of refractive index n(ω) versus photon energy: a) ba0.4ca0.6tio3 and ba0.4sr0.6tio3 b) ba0.6ca0.4tio3 and ba0.6sr0.4tio3 the variation of refractive index n(ω), with photon energy, for the titled compounds are shown in figure 6. at 0 frequency, the value of the refractive index is found to be about 2.25 for ba0.6ca0.4tio3 and ba0.6sr0.4tio3, and 2.30 for ba0.4ca0.6tio3 and ba0.4sr0.6tio3. their variations enhanced beyond the zero frequency, increase with energy in transparency region and limit reaching their maximum values in the uv region at a1 point. the obtained values are 3.204 for ba0.6ca0.4tio3, 3.201 for ba0.4ca0.6tio3, 3.040 for ba0.6sr0.4tio3 and 3.258 for ba0.4sr0.6tio3. beyond the maximum point (a1), the refractive index decreases with few oscillations to a2 and a3 points. then, it tend to the unity after plasma frequency which exhibit an insulators-like behaviour. in general, the spectra are shifted towards low energies by changing the cations from ba to ca and sr. the calculated extinction coefficient k(ω) for ba0.6ca0.4tio3 and ba0.4sr0.4tio3 and for ba0.6ca0.6tio3 and ba0.4sr0.6tio3 is displayed in figure 7a and figure 7b respectively.the analysis of the curves depicts a constant value between 0 ev and the optical edge value, and then, the extinction coefficient increases with ca and sr content, accompanied by some swings which are due to the extinction of the plasmons. the absorption edge starts from about 2 ev, corresponding to the energy gap. this originates from the transition between o-2p states located at the top of the valence bands to the ti-3d states dominating in the bottom of the conduction bands. table ii gathers the values of the critical points (a1). the higher value was observed for ba0.4ca0.6tio3 (1.970 at 4.485 ev). figure 7: variation of extinction coefficient k(ω) versus photon energy: a) ba0.6ca0.4tio3 and ba0.6sr0.4tio3 b) ba0.4ca0.6tio3 and ba0.4sr0.6tio3 o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 table 2. maximum values of the first peaks for optical constants. conclusion we have investigated the structural, electronic and optical properties of ba1xcaxtio3 and ba1-xsrxtio3 (x=0.4, 0.6) using dft calculations with gga approximation as implemented in the abinit package. the results show that the fundamental gap of all compounds exhibits an indirect transition at m-points, with low energy dispersion along height symmetry directions wich is large compared to batio3 situated at point. the calculated energy band gaps are 2.201 ev, 2.222 ev, 2.263 ev and 2.266 ev for ba0.6ca0.4tio3, ba0.6sr0.4tio3, ba0.4ca0.6tio3 and ba0.4sr0.6tio3 respectively. the analysis of the total and partial densities of states reveals the contribution of all components around the energy gap and a small displacement of the density in conduction band to high energy. the energy loss gives a sharp peak at 21 ev, which is related with the reduction of reflectivity due to plasma frequency ωp. references 1. r. migoni, h. 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(2018) o. tahiri et al. electronic and optical properties of ba(1-x)ca(x)tio3 and ba(1-x)sr(x)tio3 (x=0.4, 0.6) oaj materials and devices, vol 3 #1, 2004 (2018) – doi: 10.23647/ca.md20182004 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. (see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com rev f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-1 – doi: 10.23647/ca.md20220327 article type: a-regular research paper spectrophysics of coumarin-based chromophore faisal rasool, (1), amir sohail* (1) (1) chemistry department, college of science, united arab emirates university, p.o. box 15551, al-ain, united arab emirates. corresponding author : amir sohail received: 13 march 2022 / received in final form: 24 march 2022 / accepted: 7 april 2022 abstract : in this work, we comprehensively explore the spectral and photophysical properties of a coumarinbased dye (1) in neat solvents. the modulation of stokes shifts, emission quantum yields (фf) and excited-state lifetimes of 1 by local environment (polarity, polarizability, viscosity and hydrogen bonding) signifies the formation of intramolecular charge state (ict) from the amino group to the coumarin moiety. collectively, in the more viscous polar solvents the rotation of the amino group is restricted, exponentially decreasing the non-radiative rate constants (knr). keywords : spectrophysics, intermolecular charge transfer, non-radiative rate constant, excited-state lifetime, local environment. introduction organic molecules' fluorescence is heavily reliant on their surroundings.[1] the bulk properties of a fluorophore or a chemical system are essentially determined by intermolecular reactions, and a number of properties must be considered when determining this relationship. molecular shape and conformation, electrostatic, dipolar, and multipolar interactions, and short-range dispersive interactions are among these influences.[2], [3] fluorescent dyes have thus become common molecular probes for determining microenvironmental parameters such as media polarity, as well as tracking their distribution and relocation in micro heterogeneous systems. based on the literature study, it is reported that researchers have been interested in obtaining white light emission from organic molecules because of their usefulness in the solid-state lighting industry, as well as the light effects of liquid-crystal displays (lcds) and full color oled displays.[4], [5] very rare organic compounds have been reported that emit across the entire visible spectrum (400 nm to 700 nm) with only a few reports available.[6]–[8] however, multilayered device fabrication by successive evaporation of different emitting compounds, spin coating of a mixture of different soluble emitters, excimer or exciplex emission, use of organic–metal complexes in a hybrid device structure, and phosphorescent emitters with a compatible host are the most commonly used methods for white light emissions.[4], [6], [9] [10], [11]. for white emission, the system structure is also essential. the f. rasool, a. sohail. oaj materials and devices, vol. 6#1 (2022), 0327-1 doi: 10.23647/ca.md20220327 mailto:e-mail@address f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-2 – doi: 10.23647/ca.md20220327 disadvantages of phosphorescent emitters are their high expense and complex system architectures. as a result, in order to be realistic in white organic light emitting diodes (woleds), emission from a single compound is often preferred for ease of product fabrication.[9], [12]–[14] woleds with a single emitting part provide benefits such as reproducibility, system reliability, and ease of fabrication[14]. in this context, the field of developing new fluorescent organic moieties with a broad spectrum of emissions in their solid state remains intriguing and demanding for researchers[15], [16] coumarins have inspired researchers' attention for decades due to their broad variety of uses in electronics and photonics, taking advantages of their high stability and ease of synthesis, which has led to many sophisticated applications as sensors and emitters for solid state dye lasers and oleds.[14], [17], [18] however, based on structures the planar coumarin are considered to be more prone to self-quenching due to aggregation and intermolecular interactions (π–π interactions), reducing their usage and applications in oleds.[2], [19]–[23] it is believed that the invention of a host–guest doped emitter device has been a blessing to emissive display technologies increasing its application in many fields.[5], [24]–[28] simultaneously, a lot of work has been undertaken to eliminate planar luminophores' aggregation/dye–dye interactions. regulated π–π interactions are important in the creation of long-range emissions (excimer/exciplex formation), so they've been used as a support for light generation, especially white electroluminescence (el).[28], [29] as a result, over the last decade, new fluorescent materials for oleds, as well as the creation of a basic device structure, have gotten a lot of attention.[6], [17], [30], [31] in this context, our exploration for new white-emitting electroluminescent materials led us to synthesize planar coumarin derivatives with extended π-conjugation. the physical properties in solution such as uv-vis absorption, fluorescence and excited-state lifetime of compound 1 are investigated in this study. figure 1. chemical structures of 1, see experimental section. results and discussion table 1 summarizes the collected major absorption and emission maxima for chromophore 1’s structures, as well as the single fluorescence lifetime values (figures 2, 3), along with the corresponding stokes shift, relative fluorescence quantum yields (фf), excited-state lifetime (τ), radiative (kr) and non-radiative (knr) rate constants in different neat solvents. figure 2. absorption (black) and emission (red) spectra (λexc = 375 nm) of chromophore 1 in hexane (a) and ethanol (b). tetrahydrofurane (c), dimethylsulphoxide (d), dioxane (e), dichloromethane (f), chloroform (g), acetonitrile (h), butanol (i), dimethyleflouroamide (j) f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-3 – doi: 10.23647/ca.md20220327 figure 3. emission decays for 1 (25 μm) in hexane (a), ethanol (b) acetonitrile (c), chloroform (d), diethylether (e), methanol (f), tetrahydrofuran (g), dichloromethane (h), dimethylsulphoxide (i), dimethylefouramide (j), dioxane k) and butanol (l) upon excitation at 375 nm (30 ps) at room temperature. instrument response function (irf) is also shown in red upon excitation at 375 nm (30 ps) at room temperature. instrument response function (irf) is also shown in red. noticeably, non-linear lippert-metaga plot has been observed as illustrated in figure 4a when stokes shift values were plotted against solvent orientational polarizability (δf) (table 2). in addition, the measured фf and τ did not correlated with solvent polarity/polariozabilioty factors (figure 4b and 5a). this means that solvent polarity and polarizability effects do not alone play a role on affecting the photophysical properties of 1 in neat solvents. figure 4. correlation between the stokes shifts (δν, a) and fluorescence quantum yields (фf, b) for 1 with the orientation polarizability (δf) for different solvents. the time-resolved emission measurements along with the quantum yields data enabled us to better understand the origin of luminescence and to assess which solvent property controls the spectral properties of 1. in the present study, the emission decays were measured every 10 nm across the entire emission spectra for each sample when excited at 375 nm. in the global analysis, the data measured at all wavelengths are fitted simultaneously by a mono-exponential function convoluted with the instrument response function (irf). the fluorescence lifetime is given by the inverse of the rate constant of the exponential decay. the fluorescence lifetime experiments were repeated several times. the estimated experimental error was 4 %. the radiative (kr) and nonradiative (knr) rate constants (table 1) were then calculated and compared to the solvent parameters listed in table 2 (figure 5b). while kr is independent of solvents polarity, value of knr increases significantly in low-polarity solvents. figure 5. correlation between the excited-state lifetime (τ, a), radiative (kr) and non-radiative (knr, b) decay rates for 1 with the orientation polarizability (δf) for different solvents. to explain the above observation, the knr was plotted against solvent viscosity. an exponential dependence was observed (figure 6). it transpires that by analogy to similar coumarin derivatives,2 the increased value of knr in non-polar solvents is attributed to the rotation of toluene or cyano group, which provides a rapid deactivation pathway to the ground state. in more polar solvents an intramolecular charge state (ict) state is formed, causing the larger stokes shift. however, in this ict state, rotation of the toluene is restricted and knr decreased. it must be said that this rotation is restricted due to large energy barrier in the ground state. the energy barrier is much smaller in the excited state. consequently, such rotation effects the emission intensity and excited state lifetime of the fluorophore. f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-4 – doi: 10.23647/ca.md20220327 figure 6. exponential dependence of non-radiative decay rates for 1 with solvent viscosity (η) in cp for different solvents, r = 0.99 experimental samples all solvents cb7 (purity >99.9%) were purchased from sigma-aldrich and used as received. millipore water was used (conductivity less than 0.05 µs). spectroscopy the uv–visible absorption spectra were measured between 300 and 500 nm on a cary-300 instrument (agilent, santa clara, ca, usa) at room temperature. fluorescence spectra measurements were scanned at room temperature, between 400 and 700 nm on a cary-eclipse fluorimeter (agilent, santa clara, ca, usa). slit widths were 2.5 nm for both excitation and emission monochromators. the ph values were recorded using a ph meter (wtw 330i equipped with a wtw sentix mic (xylem analytics germany sales gmbh & co. kg, wtw, weilheim, germany). quartz cuvettes (1.0 cm, 4.0 ml) were used in all spectroscopic measurements and were obtained from starna cells inc. (atascadero, ca, usa). the concentration of chromophore was kept at 25 μm in all experiments, in which solution was prepared under n2 pursing. all nmr spectra were performed on a varian 400 mhz spectrometer in d2o. all 1h-nmr spectra are referenced in ppm with respect to a tms standard. the ph values of the solutions were adjusted (± 0.2 units) by adding adequate amounts of hcl or naoh and recorded using a ph meter (wtw 330i equipped with a wtw sentix mic glass electrode). photochemistry the excited-state lifetimes were measured by timecorrelated single-photon counting (tcspc) on lifespec ii spectrometer (edinburgh, kirkton campus, uk) by using epl-375 picosecond diode laser (λex =375 nm, repetition rate = 20 mhz, and instrument function = 30 ps) for excitation. a red-sensitive high-speed pmt detector (h5773-04, hamamatsu photonics k. k., hamamatsu, japan) was used to collect ~10,00 counts/s for each run. the concentration of 1 was 25 μm in each solvent. the data were analyzed by the iterative reconvolution method using the instrument’s software that utilizes the marquardt-levenberg algorithm to minimize χ2. the fluorescence decay in each solvent was found to fit mono-exponential function, eq. (1), (1) where τ is the lifetime with amplitude α quantum yield, radiative and non-radiative measurements  values were measured using coumarin 2 (c 450) in acetonitrile as the standard (фf = 0.8),2 and calculated using the known equation: where n is the refractive indices for the standard (std) and experimental (unk) solvents, i is the fluorescence integral of the emission between 400 and 700 nm, and a is the absorbance at the excitation wavelength. the error estimated as standard deviation of the mean was approximately 10% for the fluorescence quantum yields. kr and knr were calculated using the known equations: , , , and . conclusions the detailed photophysics of a coumarin-based dye as a function of local microenvironment is described and it is concluded that the change in quantum yields and excited-state lifetimes are due to the changes in non-radiative rate constants (knr), which correlates exponentially with solvent viscosity. a more polar solvents (such as butanol) restricts the rotation of the toluene/cyano compared to non-polar solvent (such as hexane). acknowledgements all authors thank the research program in united arab emirates university. references [1] e. l. rachofsky, r. osman, and j. b. a. ross, “probing structure and dynamics of dna with 2-aminopurine: effects of local environment on fluorescence †,” biochemistry, vol. 40, no. 4, pp. 946–956, jan. 2001, doi: 10.1021/bi001664o. 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[30] s.-w. wen, m.-t. lee, and c. h. chen, “recent development of blue fluorescent oled materials and devices,” j. disp. technol., vol. 1, no. 1, pp. 90–99, sep. 2005, doi: 10.1109/jdt.2005.852802. f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-6 – doi: 10.23647/ca.md20220327 table 1. absorption (λa), steady-state emission (λf) peak positions and excited-state lifetimes τ along with stokes shifts (δν), fluorescence quantum yields (фf), radiative rate constants (kr), and non-radiative rate constants (knr) for 1 at 25 µm in neat solvents. dye was excited at 375 nm in all solvents. table 2. solvent properties including refractive index (n), dielectric constant (ԑ), orientational polarizability (δf), viscosity (η), hydrogen bond accepting ability (β), hydrogen bond donating ability (α) and polarity/polarizability parameter (π*). solvents λa/ nm λf/ nm δν (cm -1) фf τ/ ns kr / 108 s–1 knr / 108 s–1 hexane 383 437 3226.4 0.057 0.35 16.5 26.9 diethylether 387 452 3715.9 0.079 0.682 11.6 13.5 chloroform 393 459 3658.8 0.205 1.817 11.3 4.37 dichloromethane 392 462 3865.2 0.246 2.044 12.2 3.69 dioxane 387 455 3861.8 0.213 1.708 12.5 4.61 tetrahydrofuran 387 460 4100.7 0.157 1.441 10.9 5.85 acetonitrile 382 469 4856.1 0.346 3.435 10.1 1.9 methanol 387 472 4653.4 0.298 3.782 7.8 1.86 ethanol 389 465 4201.6 0.580 3.501 16.6 1.2 dimethylformamide 387 474 4742.7 0.325 4.489 7.23 1.5 butanol 389 465 4201.6 0.291 3.319 8.78 2.13 dimethylsulphoxide 391 478 4654.9 0.116 1.518 7.64 5.82 solvents n ԑ δf η/ cp α β π* α + β + π* hexane 1.376 1.87 -0.001 0.28 0 0 -0.08 -0.08 diethylether 1.352 4.33 0.17 0.24 0 0.47 0.27 0.74 chloroform 1.446 4.81 0.15 0.57 0.44 0 0.58 1.02 dichloromethane 1.416 8.93 0.22 0.41 0.33 0 0.82 1.15 dioxane 1.422 2.22 0.02 1.37 0 0.37 0.55 0.92 tetrahydrofuran 1.406 7.58 0.21 0.48 0 0.55 0.58 1.13 acetonitrile 1.344 37.5 0.31 0.34 0.19 0.31 0.75 1.25 methanol 1.328 32.7 0.31 0.54 0.93 0.62 0.6 2.15 ethanol 1.364 25.07 0.29 0.98 0.83 0.77 0.54 2.14 dimethylformamide 1.435 37.6 0.28 0.92 0 0.69 0.88 1.57 butanol 1.394 17.85 0.27 2.57 0.79 0.88 0.47 2.14 dimethylsulphoxide 1.479 48.9 0.26 1.99 0 0.76 1 1.76 f. rasool, a. sohail. – spectrophysics of coumarin-based chromophore oaj materials and devices, vol. 6#1 (2022), p0327-7 – doi: 10.23647/ca.md20220327 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article permissions – important: all materials in this article may be freely reused (figures, tables, …) without any need to ask permission or to pay any fee. it is simply asked to refer to the article. materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! put your article as soon as possible on your personal sites, institutional sites, etc! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has been designed so that it can be accepted by doaj, and we are happy to inform you that this is the case now. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers, and o: opinion papers. 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(2) department of physics, university of pretoria, south africa, heshamabdelbagi100@gmail.com. (3) physics department, shendi university, sudan, heshamabdelbagi100@gmail.com. (4) radiation science division, south africa nuclear energy corporation (necsa), south africa, tshepo.ntsoane@necsa.co.za. *corresponding author: alawad20024@gmail.com received: 05 march 2022 / received in final form: 15 april 2022 / accepted: 23 april 2022 abstract : zirconium carbide (zrc) samples were prepared by spark plasma sintering (sps), at temperatures of 1700 °c, 1900 °c and 2100 °c, all at pressure of 50 megapascal (mpa). the density of zrc ceramic pellets was measured using a micromeritics accupyc ii 1340 helium pycnometer. the density of zrc ceramic pellets was found to increase from (6.51 ± 0.032) g/cm3 to (6.66 ± 0.039) g/cm3 and (6.70 ± 0.017) g/cm3 when the temperature of the sps was increased from 1700 oc to 1900 oc and 2100 oc respectively. moreover, the hardness of zrc ceramic pellets were measured using rockwell hardness test. the hardness of zrc ceramic pellets increased from (7.4 ± 0.83) to (17.0 ± 0.073) and (18.4± 0.05) gigapascals (gpa) at temperatures of 1700 oc, 1900 oc and 2100 oc respectively. x-ray diffraction shows the absence of spurious phases or impurity. xrd results showed that, all prepared zrc samples has the same preferred orientation of the planes (i.e., 200). furthermore, the average grain size of zrc was calculated using sherrers’s equation. the average grain size of the pure zrc powder increased from 67.46 nm to 72 nm, 79 nm and 83 nm when the zrc powder was sinteried at temperatures of 1700 oc, 1900 oc and 2100 oc respectively. the differences in the average grain size between the prepared samples leads to show different surface morphologies that monitored by scanning electron microscopy (sem). keywords : zirconium carbide; ceramic pellets; zirconium carbide powder; spark plasma sintering, sintering temperature. cite this article: b.a.b. alawad, h.a.a. abdelbagi, p.n. ntsoane, t.t. hlatshwayo, oaj materials and devices, vol. 6 (1), p0408-1 (2022) doi: 10.23647/ca.md20220408 b.a.b. alawad, h.a.a. abdelbagi, et al. microstructure of zirconium carbide ceramics synthesized by spark plasma sintering oaj materials and devices, vol 6(1), p0408-2 (2022) – doi: 10.23647/ca.md20220408 introduction zrc is refectory ceramic material, it has attracted considerable attention due to its high melting point (3541 oc), low density (6.73 g/cm3), high hardness (25.5 gpa), high electrical conductivity (78× 10-6 ω cm), high modulus of elasticity (350 440 mpa), good thermal shock resistance and solid-state phase stability [1-3]. due to its excellent properties, zrc material is a promising candidate for many applications such as coating of nuclear particles fuels and ultra-high temperature applications [4, 5]. zrc ceramic pellets can be prepared by the chemical vapor deposition or spark plasma sintering. sps is a sintering technique utilizing uniaxial force and a pulsed direct electrical current under low atmospheric pressure to perform high speed consolidation of the powder [6]. it provides rapid densification for different types of materials such as zrc and hafnium carbide (hfc) [7]. this direct way of heating allows the application of very high heating and cooling rates, enhancing densification over grain growth promoting diffusion mechanisms allowing maintaining of the intrinsic properties of nano-powders in their fully dense products [8-10]. sps systems offer many advantages over conventional systems using hot press sintering, hot isostatic pressing or atmospheric furnaces. including ease of operation and accurate control of sintering energy as well as high sintering speed, high reproducibility, safety and reliability [8, 11]. while similar in some aspects to hot press, the sps process is characterized by the application of the electric current through a power supply, leading to very rapid and efficient heating [8]. in sps, densifications and sinter ability of zrc can improved by metallic additive such as ni, mo, and their alloy [12, 13]. however, this can degrade the high temperature properties and corrosion resistance of zrc [1214]. for this reason, no additives were added in the zrc samples sintered. spark plasma sintering technique is a promising approach to improve the densification of zrc at high temperature [6]. previous study reported that, pressure assisted sintering at high sintering temperature to obtained dense zrc ceramic [7]. in this work, the zrc powder was compressed using sps at pressure of 50 mpa and at different temperatures (i.e., 1700 oc, 1900 oc and 2100 oc). in this paper, the effect of sintering temperature on the microstructures, density, and hardness of the obtained zrc ceramics was investigated. experimental procedure copy the raw materials used were zirconium carbide powder (mean particle size of 67.46 nm and purity >99 %) from sigmaaldrich. the zrc powder was weighed using an electronic mass balance, so that equal amounts of the zrc powder were used for the spark plasma sintering (sps) process. the powders were prepared in a 20 mm inner diameter graphite die. graphite foil with a thickness of 0.2 mm was placed between the die and powder for easy removal and to ensure that the cooling of the sintered zrc samples was homogeneous. the outside of the graphite die was covered with an insulating felt to reduce radiation loss [15]. after the powder was placed in the graphite die, it was first cold pressed using a hydraulic press to consolidate the powder together and then spark plasma sintered (sps). the zrc ceramic pellets were sintered by sps using the hhpd-25 from fct system gmbh germany at tshwane university of technology (see fig. 1) [16]. the sps process was conducted at temperatures of 1700 °c, 1900 °c and 2100 °c at a heating rate of 100 °c/min in vacuum (0.05 bar) until the desired temperature was attained. the holding time and pressure for sintering were 10 minutes and 50 mpa respectively. at the end of the sintering cycle, the specimens were rapidly cooled to room temperature. the samples of 20 mm diameter and approximately 5 mm thickness were attained. the samples were then cut into smaller pieces by a diamond saw, thereafter, polished using a saphir 550 semi-automatic grinder/polisher. the samples were then cleaned in an ultrasonic bath using demineralized water and then ethanol for 5 min each. then, the samples were dried in an oven at 100 oc for 30 min. fig. 2 shows variation in pressure, displacement and temperature versus time regime during the sintering process at 1700 ˚c, 1900 ˚c and 2100 ˚c – see fig. 2 (a), (b) and (c) respectively. at the end of the sintering cycle, the specimens were rapidly cooled to room temperature. the bulk densities of the as-sintered zrc samples were measured by archimedes‟ technique (using a micromeritics accupyc ii 1340 fully automated pycnometer at university of pretoria), this was done after removing the outer layer by polishing. the vickers hardness was measured on a hardness tester (rockwell hardness testing machine at university of pretoria) with an indentation load of 10 kg and a dwell time of 10 s. the phase composition of the sintered zrc samples was analyzed by x-ray diffraction (using bruker xrd d8 advance) with a cukα radiation source (λ = 1.54056 å) within the recording range of 15 to 125° and a step size of 0.04o. the grain sizes of samples were measured from the xrd patterns using sherrers’s equation as given by equation (1) below [17]. furthermore, the preferred orientation of the planes of the sintered zrc samples was determined from the texture coefficient of the planes as given by equation (2) [18]. b.a.b. alawad, h.a.a. abdelbagi, et al. microstructure of zirconium carbide ceramics synthesized by spark plasma sintering oaj materials and devices, vol 6(1), p0408-3 (2022) – doi: 10.23647/ca.md20220408   cos k d = (1) where d is the average grain size, β is the full width at half maximum (fwhm) of the diffraction peak, θ is the bragg angle (i.e., position of the peak), k is a constant (a value of 0.94 was used), λ is the wavelength of the excitation x-rays which is equals 1.54056 å for cukα radiation source.  − = )(/)( )(/)( 1 hklihklin hklihkli tc o o (2) where tc (hkl) is the texture coefficient of the hkl plane, i(hkl) is the measured relative intensity of a plane taken from the raw data of xrd, i0(hkl) is the standard intensity of the plane taken from the international centre for diffraction data (icdd) database, n is the number of planes considered. the morphology of the zrc surface layer were observed by scanning electron microscopy (sem) (zeiss ultra plus) with operating voltage of 1 kv. fig. 1. schematic diagram of spark-plasma sintering (sps). results and discussion 1. density and vickers hardness measurements the relative density of zrc increased with the sintering temperature from 96.6 % at 1700 °c and reached a maximum of 99.5 % at 2100 °c. the relative density of the zrc ceramics from sciti et al. [19] after sintering at 2100 °c was about 99 %. they used zrc powders with mean particle size of 3.8 µm and their sample was sintered for only 3 min but at a higher pressure of 65 mpa. sun et al. [20] performed reactive spark plasma sintering (rsps) using zirconium oxide (zro2) and carbon black to obtain zrc whose relative density increased with the sintering temperature and reached 96.1% at 1900 °c. therefore, as seen from the results in table 1 and the results from other studies [19,20], it can observed that higher densification of zrc carbide is obtained as the sintering temperature increased. the relative density increases with temperature from 1700 to 2100 °c, and the grains coalesce to form denser clusters. the density did not reach the theoretical density of zrc which is about 6.73 g/cm3, due presence of minute amounts of free carbon. sun et al. [20] and sciti et al. [19] obtained vickers hardness values of 16.3 and 17.9 gpa from zrc sintered at 1900 °c and 2100 °c respectively. the hardness values obtained in this study were 17.0 and 18.4 gpa after sintering zrc at 1900 °c and 2100 °c respectively. these hardness values are slightly higher compared to those obtained by sun et al. and sciti et al. this is due to the longer sintering duration of 10 min at a lower pressure of 50 mpa at 2100 °c compared to 3 min and 65 mpa used by sciti et al. [19]. it can be observed that longer sintering durations can lead to lower porosity therefore high density and high hardness values. the number of pores of the zrc sintered at different temperatures were observed by scanning electron microscopy (sem) and the results are discussed in section 3.3. fig. 2. the graphs of pressure, displacement and temperature versus time regime during the sintering process at (a) 1700 oc (b)1900 oc (c) 2100 oc. 2. xrd analysis the phase composition of the bulk as-sintered zrc samples was analysed by x-ray diffraction analysis (with an x-ray exposure time of 2 seconds for each step). the xrd patterns of zrc samples sintered at 1700 °c, 1900 °c and 2100 °c are shown in fig. 3. the diffraction peaks indicate the polycrystalline structure of the sps synthesised zrc. the all samples had similar peaks, and their intensities were observed to vary slightly. the xrd patterns of the prepared zrc samples by sps showed that all peaks are belong to the zrc crystalline peaks. there did not appear to be any extra peaks, indicating there were no impurities present. since the starting materials were pure zrc powders, the xrd results was expected. b.a.b. alawad, h.a.a. abdelbagi, et al. microstructure of zirconium carbide ceramics synthesized by spark plasma sintering oaj materials and devices, vol 6(1), p0408-4 (2022) – doi: 10.23647/ca.md20220408 table 1: relative density and hardness of zrc prepared by sps at 1700 ˚c, 1900 ˚c and 2100 ˚c and compared with the data from previous studies [19, 20]. material s sintering conditions (oc/min/mp a) mean grain size (µm) relat ive dens ity (℅) vickers hardne ss (gpa) refere nce zrc 1700/10/5 0 0.07 2 96.5 7.4 ± 0.83 this study zrc 1900/10/5 0 0.07 9 98.9 17.0±0 .073 this study zrc 2100/10/5 0 0.08 3 99.5 18.4 ±0.05 this study zrc 1850/10/6 0 arou nd 2 85.3 9.1± 1.40 [20] zrc 1900/10/6 0 <10 96.1 16.3 ± 1.60 [20] zrc 2100/3/65 13±1 99.0 17.9 ± 0.60 [19] the zrc peaks became slightly sharper at 2100 °c but the peak intensities were slightly lower than those obtained at 1700 °c and 1900 °c. the change in the peak intensity might be due to the change in the zrc grain size, which will be discussed in more details in the next paragraph. the preferred orientation determined from the texture coefficient of the planes (given by equation (2) above) of the zrc prepared by sps at 1700 °c, 1900 °c and 2100 °c was found to be (200). the grain sizes of the zrc samples were calculated using sherrers’s equation (i.e., equation (1)). the calculated grain size of the pure zrc powder (manufactured by sigma-aldrich with 99.9% purity) was found to be 67.46 nm. the average grain size was observed to increase from 71.88 ± 3.6 to 83.59 ± 3.9 nm after sintering from 1700 °c to 2100 °c, at 50 mpa for 10 min, respectively. increasing the sintering temperature will increase the mobility of zrc atoms led to the increase in average grain size, in line with crystal growth theory [21,22]. in comparison to previous studies by sciti et al. [19, 23] who investigated the sinter ability of commercial zrc powders with mean particle size of 3.8 µm (they did not report the grain or crystallite size), however, they measured the grain size for the obtained dense zrc ceramics. they found that the grain size increased from 5.8±1 to 13±1 µm after sintering at temperatures from 1900 to 2100 °c, pressure of 65 mpa and time of 3 min. this indicated that the starting materials, sintering conditions and the application of very high heating and cooling rates led to form larger grain sizes at higher temperatures which enhanced higher densification. sciti et al. [23], measured the grain sizes of their sps prepared zrc samples through image analysis on sem micrographs using the image pro plus software. however, in this study, the crystallite size was calculated from xrd spectra using sherrers’s equation (i.e., equation (1)). therefore, these are fundamentally different results and not comparable with our results, since a particle often has more than one grain. the overall trend is an increase in grain size of zrc with increasing temperature. it is well known that the average grain size of a film increases with increasing temperature as reported by thompson et al. [24]. this is due to the increasing mobility of the atoms at higher temperature. fig. 3. xrd patterns of zrc ceramics produced by sps in 1700 oc, 1900 oc and 2100 oc. 3. sem analysis the sem images (obtained by secondary electron mode) from the surface of the zrc samples sintered to different final temperatures allowed the investigation of the microstructure evolution during the sps. however, the contrast in these images is not appropriate to make grain size comparison easy. this could be due to the large pores that can trap the secondary electrons generated. the surface of zrc sintered at 1700 °c is given in fig. 4 (a) and the surface can be observed to be inhomogeneous and coarse. this is due to agglomeration and coalescing of the fine zrc particles to form larger ones during sintering. this led to a highly porous structure at this sintering temperature. the presence of these pores in the surface of zrc samples sintered at 1700 °c can explain the lower relative density of the sample b.a.b. alawad, h.a.a. abdelbagi, et al. microstructure of zirconium carbide ceramics synthesized by spark plasma sintering oaj materials and devices, vol 6(1), p0408-5 (2022) – doi: 10.23647/ca.md20220408 obtained (96.5 %) – see table 1. furthermore, the structural changes due to sintering at different temperatures can be deduced from the sem micrographs as seen in fig. 4 (a), (b) and (c). the surface of zrc sample sintered at 1900 °c (fig. 4 (b)) is still inhomogeneous, it is denser with a lower number of pores compared to the sample sintered at 1700 °c. the inhomogeneous surface consists of particles of different sizes. the reduced pore size and density accounts for the increase in relative density of this sample to 98.9% and increase in particle size after sintering at 1900 °c – see fig 4 (b) and table. 1. as mentioned above, increasing the sintering temperature can decrease the number of pores due to growth of the crystallites at higher temperatures. the surface of the sample sintered at 2100 °c has fewer and smaller pores (with relative density of 99.5 %) compared to the sample prepared at 1900 °c which had larger and more pores. the surface looks smoother compared to the 1700 °c and 1900 °c prepared samples and the grains are lying flat on a surface. the sem micrographs of zrc sintered at 1700 and 2100 °c illustrate how the zrc surface morphology changed with the relative density. these changes led to an increase in relative density and hardness from 96.5% and 7.4 gpa at 1700 to 99.5% and 18.4 gpa at 2100 °c, respectively. in fig. 4(c), more consolidated surface structure appears in the specimens. therefore, from fig. 4 and table 1, the sintering temperature determines the level of densification of zrc as well as the crystallite size growth. the progress of enhanced densification and crystallization phenomena with increase in the sintering temperature might be due to accelerated surface diffusion and grain boundary diffusion at the higher temperatures [25]. fig. 4. sem micrographs of (a) zrc ceramic sintered at 1700 °c, (b) at 1900 °c and (c) at 2100 °c by sps. conclusion zrc was synthesised by sps at various temperatures. the phase and microstructure evolution after the zrc sintering process at 1700 ˚c, 1900 ˚c and 2100 ˚c was investigated by sem. the relative density of zrc prepared by sps was seen to increase as sintering temperature increased. this is due to the increase in the grain size of zrc as the sintering temperature increased. the growth of the grain will lead to the closure of the pores. thus, the reduction in the pore size will led to the increase in relative density high temperatures sintered samples. moreover, the reduction in the pore number and size causes the hardness of zrc to be increased. the preferred orientation of the zrc sintered at 1700 °c to 2100 °c was found to be the (200) plane. the surface of the as-sintered samples was observed to vary with sintering temperatures. the zrc surface was generally 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university, m.benhamou@ensam-umi.ac.ma received: 9 july 2018 / received in final form: 28 july 2018 / accepted: 31 july 2018 abstract: diffusion is a natural or artificial process that governs many phenomena in nature. the most known diffusion is the brownian or normal motion, where the mean-square-displacement of the tracer (diffusive particle among others) increases as the square-root of time. it is not the case, however, for complex systems, where the diffusion is rather slow, because at small-scales, these media present an heterogenous structure. this kind of slow motion is called subdiffusion, where the associated mean-square-displacement increases in time, with a non trivial exponent, α, whose value is between 0 and 1. in this review paper, we report on new trends dealt with the study of the anomalous diffusion in condensed matter physics. the study is achieved using a theoretical approach that is based on a generalized langevin equation. as particular crowded systems, we choose the so-called pickering emulsions (oil-in-water), and we are interested in how the dispersed droplets (protected by small solid charged nanoparticles) can diffuse in the continuous phase (water). dynamic study is accomplished through the mean-square-displacement and the velocity-autocorrelation-function. finally, a comparison with molecular dynamics data is made. keywords: complex systems, anomalous diffusion, generalized langevin equations, mean-square-displacement, velocity-autocorrelation-function, molecular dynamics simulation. i. introduction the anomalous diffusion in various fields of science (physics, chemistry, biology, ecology...) has received much attention from a theoretical and experimental point of view. in fact, such a diffusion m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p2 appears in heterogeneous, disordered, fractal, colloidal and polymer systems, and in general, it produces within the complex systems containing entities that move on different scale-times. in opposition to the normal or brownian diffusion, the anomalous diffusion is slower, due to an extreme difficulty that a particle (tracer) moves in a complex structure. this kind of diffusion is usually referred to as subdiffusion, and it is characterized by a mean-square-displacement (msd) that behaves as: w(t) ≡ 〈(𝐱(t) − 𝐱(0)) 2 〉 = 2dαt α, with 0 < α < 1. this large-time behavior then deviates from the linear dependence on time found for the brownian motion [1-3] . in expression above, 𝐱(t), represents the time-position of the random walker, and the generalized diffusion coefficient, dα, also called "fractional diffusion coefficient", is expressed in length2/timeα unit. we emphasize that the subdiffusion is a feature of the crowded systems, where the trajectories of their mobile constituents are strongly correlated. notice that the above scaling relation is valid for large-times, that is beyond some characteristic time depending on the specific details of the diffusion process and the structure of the host medium. in general, a particle is said to be subdiffusive if the condition w(t)/t → 0, for t → +∞, is satisfied (very slow diffusion). this explains why the anomalous exponent, 𝛼, must be in the interval 0 < α < 1. it is noted that the subdiffusive transport appears in a variety of systems, such as the random-walk in fractal structures [2] , fractional-time brownian motion [4] , living systems [5] , charge carrier transport in amorphous semiconductors [6,7] , nmr diffusometry on percolation structures [8] , and the motion of a colloid in a polymer network [9] . for example, for diffusion in fractal structures, α = 2/dw, where dw > 2 is the walk-dimension (dw = 2df/ds, where df and ds are the fractal and spectral dimensions, respectively), and for the fractional-time brownian motion, α = 2h, where 𝐻 is the hurst index. examples of enhanced diffusion (α > 1) include tracer particles in vortex arrays in a rotating flow [10] , layered velocity fields [11] , and richardson diffusion [12] . the case 1 < α < 2 refers to superdiffusion (turbulent plasmas, levy-flights, transport in polymers), α = 2, to ballistic diffusion (optical traps), and α = 3, to richardson diffusion (atmospheric turbulence). the subdiffusion or superdiffusion exponent, 𝛼, is not a universal quantity, but mainly depends on the pertinent parameters that control the phenomenon. as we shall see below, for the subdiffusion of the clothed droplets of pickering emulsions, this exponent shall depend on their size, density and surface charge, and the saltconcentration. anomalous diffusion is a subject which has been extensively studied, especially in the past decade by using the so-called generalized langevin equation (gle) (with memory) [13,14–19] . the last has been introduced by kubo [20] , as a generalization of the standard langevin equation describing the brownian or normal diffusion. another useful approach to the anomalous diffusion is based on the fractional diffusion equation [21-23] ), fractional fokker–planck equation [21,24] , generalized chapmankolmogorov equation [25] and fractional generalized langevin equation [26,27] . in their seminal paper, mainardi and pironi [28] had introduced a fractional langevin equation taking into account the retarding effects due to hydrodynamic backflow and showed that it is a particular case of gle. these equations can be analyzed by using the properties and asymptotic behaviors of mittag-leffler (m-l) functions [29-41] . for the reader, an exhaustive list of other important developments of the subject can be found in ref. [42]. in this paper, we show how gle can be applied to study the sub-diffusion phenomenon within particular complex systems which are pickering emulsions (pes) [43,44] , and compare results from this equation to molecular dynamics (md) data [45] . this computational method was introduced by alder and wainwright [46] , in order to study the structure and dynamics of liquids. pes are dispersions presenting, very often, as oil-in-water (o/w), water-in-oil (w/o) or double emulsion water-oil-water (w/o/w). these dispersions are stabilized by an addition of small solid (organic or inorganic) particles that act as emulsifiers, instead of the surfactant molecules [47-50] . these particles that act as emulsifiers are of nanometric size, while the stabilized droplets are as small as few micrometers diameter. the stabilization of larger droplets (few millimeters diameter) is possible as well, using micron-sized solid particles. the stabilization of the dispersed droplets within pes is ensured by a strong adsorption of the solid nanoparticles at their surfaces. in contrary to surfactants, where the adsorption is rather dynamic (reversible), that of the charged solidparticles is irreversible and sufficiently strong, with a very high adsorption energy, between kb t and 10 8kbt, where kbt is the thermal energy. here, kb is the boltzmann's constant and t is the bath temperature. of course, such an energy mainly depends on the value of the wetting (or contact) angle and the droplet-radius [50] . m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p3 the anchoring of the solid particles emanates from a partial wetting of the surface of the charged solid particles by water and oil. due to their remarkable properties, such as high stability with respect to coalescence and their recent use in nanotechnology leading to the creation and the characterization of the nano-scale structures in new ways, pes have been the subject of many studies, both from experimental and theoretical point of views. in addition, they can serve as templates for the advanced materials [51,52] , as janus colloids [53] , composite particles [54-61] and colloidosomes [62-64] . pes are heterogenous liquids which present as a dispersion of droplets of some liquid (dispersed phase) in another one (continuous phase). the two liquids are not chemically and physically compatible. by a mechanical mixing of the emulsion, each droplet becomes surrounded by discrete nanoparticles arranged on its surface. for the study of pes, the clothed droplets can be regarded as charged soft-colloids [65] . these charged droplets are subject to an anomalous diffusion as observed by md simulations [45] , and we are interested in how they really move using a gle approach. the dynamics of these droplets are studied through two main quantities, which are msd and the velocityautocorrelation-function (vacf). as we shall see below, for an appropriate choice of the memoryfunction, the solutions to gle express themselves in terms of m-l functions. the remaining of the presentation proceeds as follows. in the first section, we present a general dynamic theory, based on a gle. a comparison between the results from this theory with md data is the aim of the third section. finally, some concluding remarks are drawn in the last section. ii. dynamic theory consider a given particle, termed tracer or random walker, which executes a diffusion movement in the host medium. the raised question is how this random walker diffuses in the host medium, beyond some characteristic time we will precise below. in this time-regime, the random walker (target) feels to be trapped in a cage formed by the surrounding particles (traps), and then, it cannot escape from this cage, except after a long-time. we denote by nc, the average-number of traps around the considered random walker. consequently, the presence of the traps makes difficult such a diffusion process, and then, the random walker executes rather a subdiffusion, characterized by an anomalous exponent, α. the latter depends essentially on the nature of the random process and that of the host medium. the basic dynamic quantities of our interest are msd, 〈(𝐱(t) − 𝐱(0)) 2 〉 ≡ w(t), and vacf, 〈𝐯(t). 𝐯(0)〉 ≡ cvv(t). they are related by w(t) = 2 ∫ dt′(t − t′)cvv(t ′), t t0 cvv(t) = 1 2 d2w(t) dt2 (1) to investigate quantitatively the cage effect and the subdiffusion phenomenon, the starting point is a gle developed in the past by kubo [20] and by zwanzig [66] . then, gle describing the motion of the random walker reads m d𝐯(t) dt = −m ∫ dt′γ(t − t′)𝐯(t′) t 0 + 𝛏(t) (2) here, γ(t) is the memory-function that expresses a retardation to friction. the random force, 𝛏(t), satisfies 〈𝛏(t)〉 = 𝟎 , 〈𝛏(t). 𝛏(0)〉 = mkbtγ(t) . 〈𝐯(0). 𝛏(t)〉 = 0 (3) for viscous colloidal solutions, the particle acceleration vanishes, and in this case, gle equation reads −m𝐯0δ(t) = −m ∫ dt′γ(t − t′)𝐯(t′) t 0 + 𝛏(t) (4) where v0 = |𝐯0| = √2kbt/m is the initial velocity of the tracer and the stochastic force, 𝛏(t), also satisfies relations (3). m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p4 assume, now, that the memory-function has the form γ(t) = γ0δ(t) + γα γ(1−α) t−α (0 < α < 1) (5) here, γ0 and γα are two positive constants, γ(x) is the euler gamma function and δ(t) represents the dirac-distribution. using the laplace-transform techniques together with relations (3), we find that msd and vacf, in the non-inertial regime, are given by w(t) = 2 kbt mγ0 te1−α,2 (− ( t τ ) 1−α ) (6) with the heaviside step-function, θ(x). in these expressions, eσ,τ(x) denotes the twoparameter m-l function [29] . there, τ = (γ0/γα) 1/(1−α) is a time-scale. for small-times, in comparison with the characteristic one, τ, msd and vacf behave, respectively, as then, at these time-scales, the random walker executes a brownian (normal) diffusion, with the usual diffusion coefficient, d0 = kbt/mγ0. for large-times, compared to τ, we find w(t) = 2dαt α (𝑡 ≫ 𝜏) (10) cvv(t) = α(α − 1)dαt α (t ≫ τ) (11) with which denotes the generalized diffusion coefficient. iii. comparison with md simulations for the description of the dynamic properties of pes, using md method, the equations of motion are solved in the canonical ensemble using the velocity verlet algorithm (vva) [67] , with the thermostat of berendsen [68] , in order to keep the temperature constant. in addition, periodic boundary conditions are applied to remove the surface effects and simulate an infinite emulsion. in the following, it will be convenient to use dimensionless units, where the length unit is σ, time in units of τ = σ√m/ε, where m is the oil-droplet mass and ε is the depth of the interaction potential, kbt is the energy unit, and l0 = n × (6v/πn) 1/3 is the box-size, where n is the number of the clothed oil-droplets, and v is the volume of simulation box (in periodic conditions). md simulations [45] where carried out with 1728 oildroplets and the dimensionless time-step for vva is chosen to be 0.05. the last typical value of steptime is that usually adopted in studying the colloidal solutions from md simulations. discussion on dynamics of pes was made [45] varying the pertinent factors, as the surface charge of oil-droplets, and their density and the concentration of the added salt. cvv(t) = kbt mγ0 d2 dt2 [te1−α,2 (− ( t τ ) 1−α ) θ(t)] (7) w(t) = 2d0 t (t ≪ τ) (8) cvv(t) = d0δ(t) (t ≪ τ) (9) 𝐷𝛼 = 𝐷0 γ(𝛼+1) (12) m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p5 charge effects the first goal was the quantification of the influence of the charge carried by the oil-droplets on their dynamic properties [45] . the size of the oil-droplets, their reduced number density and the saltconcentration were fixed to the values: σ = 20000 å, ρ∗ = 0.0020 and cs = 2.91 μm. but the valence, z, was varied from 1000 to 4500. -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 lo g (m e a n s q u a re d is p la c e m e n t) log(time) z=1000 z=1500 z=2000 z=2500 z=3000 z=3500 z=4000 z=4500 figure 1: msd versus dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the oil-droplet surface charge, with the fixed parameters: 𝛔 = 𝟐𝟎𝟎𝟎𝟎 å, 𝛒∗ = 𝟎. 𝟎𝟎𝟐𝟎 and 𝐜𝐬 = 𝟐. 𝟗𝟏 𝛍𝐌. figure 1 shows the log-log plot of the reduced msd upon dimensionless time, t/τ, for various values of the surface charge. such a figure clearly shows the existence of two time-regimes. for early times, the random walker executes a normal diffusion, independently of the value of the surface charge. this agrees with the theoretical behavior, relation (8). above some known characteristic time, it executes rather a subdiffusion, and msd behaves as w(t)~dαt α, with an average subdiffusion exponent αc = 0.418. this result is in perfect agreement with the theoretical behavior, relation (10). as already shown [45] , both anomalous diffusion exponent, α, and fractional diffusion coefficient, dα, decrease progressively with the surface charge. as the later is augmented, the correlations between the oildroplets become stronger, and consequently, one assists to a slow dynamic. figure 2 indicates the time-variation of vacf, for the same values of the surface charge. the abrupt increase of this function, at small-times, can be explained by formula (9) replacing the diracdistribution δ(t) by a very narrow gaussion function, that is: δ(t) → (2πσ)−1/2exp(−t2/2σ), with a very small time-scale σ. for large-times, vacf goes to zero, in agreement with theoretical formula, relation (11). 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time z=1000 z=1500 z=2000 z=2500 z=3000 z=3500 z=4000 z=4500 figure 2: vacf versus dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the oil-droplet surface charge, with the fixed parameters: 𝛔 = 𝟐𝟎𝟎𝟎𝟎 å, 𝛒∗ = 𝟎. 𝟎𝟎𝟐𝟎 and 𝐜𝐬 = 𝟐. 𝟗𝟏 𝛍𝐌. density effects the second goal was the study of the influence of the density of the clothed oil-droplets on their dynamics [45] , fixing their surface charge and size, and the salt-concentration to the values: z = m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p6 2000, σ = 20000 å and cs = 2.91 μm. figure 3 shows the log-log plot of msd, versus dimensionless time, t/τ, for various values of the droplet-density. as above, this msd exhibits two time-regimes: normal, with a density-dependent diffusion coefficient, and subdiffusive, with an average subdiffusion exponent, αd = 0.432. this is in good agreement with the theoretical formulae (8) and (10). -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 lo g (m e a n s q u u a re d is p la c e m e n t) log(time)   =0.0010   =0.0015   =0.0020   =0.0025   =0.0030   =0.0032 figure 3: msd versus dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the oil-droplet density, with the fixed parameters: 𝐙 = 𝟐𝟎𝟎𝟎, 𝛔 = 𝟐𝟎𝟎𝟎𝟎 å and 𝐜𝐬 = 𝟐. 𝟗𝟏 𝛍𝐌. figure 4 indicates the variation of vacf upon time, for the same parameters as before. the timebehavior of this dynamic property agrees well with the theoretical predictions, relations (9) and (11). 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time  * = 0.0010  * = 0.0015  * = 0.0020  * = 0.0025  * = 0.0030  * = 0.0032 figure 4: vacf versus dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the oil-droplet density, with the fixed parameters: 𝐙 = 𝟐𝟎𝟎𝟎, 𝛔 = 𝟐𝟎𝟎𝟎𝟎 å and 𝐜𝐬 = 𝟐. 𝟗𝟏 𝛍𝐌. salt-concentration effects a quantitative investigation of the effects of the salt-concentration, cs, on the oil-droplets dynamics was achieved in ref. [45], fixing the remaining parameters to the values: z = 500, σ = 5000 å, and ρ∗ = 0.0020. m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p7 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 c s =0.470 c s =0.595 c s =0.735 c s =1.058 c s =1.440 c s =1.881 c s =2.381 lo g ( m e a n s q u a re d is p la c e m e n t) log (time) figure 5: msd versus dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the saltconcentration, with fixed parameters: 𝐙 = 𝟓𝟎𝟎, 𝛔 = 𝟓𝟎𝟎𝟎 å and 𝛒∗ = 𝟎. 𝟎𝟎𝟐𝟎. 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time c s =0.470  c s =0.595 c s =0.735 c s =1.058 c s =1.440 c s =1.881 c s =2.381 figure 6: vacf versus the dimensionless time, 𝐭/𝛕, in log-log scale, for various values of the saltconcentration, with fixed parameters: 𝐙 = 𝟓𝟎𝟎, 𝛔 = 𝟓𝟎𝟎𝟎 å and 𝛒∗ = 𝟎. 𝟎𝟎𝟐𝟎. figures 5 and 6 show the time-variation of msd and vacf, respectively. also, in this case, md data are in good agreement with theory, relations (8) to (11). in particular, at large-time, msd exhibits a subdiffuse behavior with an average exponent 𝛼𝑠 = 0.467. iii. conclusion in this presentation, we focus on a quantitative dynamic study of the subdiffusion phenomenon within crowded systems, as pickerings emulsions, which are stabilized by a strong irreversible adsorption of charged solid nanoparticles on the surface of the dispersed oil-droplets. as we have shown above, the subdiffusion with complex systems may be approched well using a non-inertial generalized langevin equation. dynamic properties were studied through two important physical quantities, which are msd and vacf. this equation was solved exactly with an appropriate choice of the memory-function, whose solution is expressed in terms of mittag-leffler functions. for pickering emulsions, it was demonstrated that the diffusion of a given oil-droplet is normal, at short-time, and subdiffusive, at large-time, with an anomalous exponent between 0 and 1, and the theoretical predictions were found to be in perfect agreement with very recent md simulations [10] . an important question to ask is how particles that are embeded on the surface of a crowded system, can diffuse in time. such a question was ensured in the case of fluid or polymerized membranes [69] and the oil-droplets of a pickering emulsion [70] . the main result is that, the random walker executes a subdiffusion, at short-time, followed by a saturation regime, at infinite time. finally, it will be interesting to extend these extensive dynamic studies to the situation where the diffusing particles have arbitrary shapes and forms. m. benhamou – review on anomalous diffusion in condensed matter physics oaj materials and devices, vol 3 #2, 0730 (2018) – doi: 10.23647/ca.md20180730 p8 acknowledgements: i am much indebted to professors d. durand and l. benyahia for helpful discussions. i would like to thank the le mans university for their kind hospitality during my regular visits. references 1. a.blumen, j.klafter, g.zumofen, in optical spectroscopy of glasses, edited by i.zschokke, reidel, dordrecht (1986) 2. s.havlin, d.ben-avraham,adv. phys., vol.36, p 187(1987) 3. j.-p.bouchaud, a.georges, phys. rep., vol.195, p 127 (1990) 4. see, for instance, d.nualart, fractional brownian motion: stochastic calculus and applications, proceedings of the international congress of mathematicians, edited by european mathematical society, madrid, spain (2006) 5. s.stachura, g.r.kneller,molecular simulation, vol.40, p 245 (2014) 6. h.scher, m.lax, phys. rev. b, vol.7, p 4491 (1973); 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(2) unité energies renouvelables, département physique, université de nouakchott al aasriya, nouakchott, mauritanie. corresponding author : sidiabaahmed@gmail.com received: 21 november 2018 / received in final form: 14 february 2019 / accepted: 17 february 2019 abstract : the purpose of this work is to evaluate four empirical models developed in literature such as ghouard, perrin brichambaut, bird and hulstrom and dependent model of the link trouble factor. the validation of these different theoretical models was carried out using solar global radiation data collected on the cheikh zayed nouakchott power plant. these measurements were carried out at a time step of 5 minutes during the period of one year. (april 1, 2015 to march 31, 2016).the results show that the ghouard model presents notable performances compared to the other models, with a determination coefficient of 96.2%. this validation also shows that the solar radiation measured and that estimated by the different models have the same pace and have good performance with a coefficient of determination greater than 93%. the available solar potential estimation was carried out using the actual measurements collected on the cheikh zayed plant. the results obtained showed that the available solar potential is 5 kwh / m² / d. keywords : solar pontential, theoretical models, measured data, sheikh zayed plant. cite this article: ahmed sidibba, diene ndiaye, sidi bouhamady, menny el bah, oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 mailto:e-mail@address a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p2 introduction the problem of energy has dominated the global economic and political scenes of the last forty years. the predominant use of fossil fuels such as oil and gas has led to a number of environmental and regional conflicts. the 1973 crisis, known as the energy crisis, has forced the world to think of alternatives to existing conventional resources that are exhaustible and in limited quantities on a global scale. indeed, fossil fuels tend to be depleted by the high-energy consumption of the world, hence the need to find new energy resources. renewable energies have a great advantage because they are abundant and inexhaustible. the major limit of these renewable resources remains the high initial investment cost [1] and its random characteristics that require a feasibility analysis of their available potentials. solar energy occupies, today, one of the most important places among the various resources of renewable energies. the precise knowledge of the available potential of sunshine and its distribution at a given location, however, remains of major importance for the development of solar energy systems and the analysis of their performance. in recent years, many models have been proposed to predict solar radiation. capderou et al. 1987 [2] proposed a prediction model of solar radiation based essentially on the knowledge of the atmospheric disorder factor. the model makes it possible to determine the different components of the solar radiation (global, diffuse and direct) of a given locality. zhang et al, 2002 [3] proposed a model for estimating hourly solar radiation in beijing and guangzhou. as part of this modeling, the authors considered the influence of the variation of meteorological parameters as temperature, humidity and wind speed on the behavior of solar radiation. chen et al, 2004 [4] observed, following a study, that the hargreaves and allen models are not suitable for estimating global solar radiation for, especially, regions of china. as a result, they suggested another model to improve the estimation of sunshine. the aim of this work is to study different methods for determining global solar radiation on a horizontal plane and then to validate it by comparison with solar radiation measured at the nouakchott-mauritania site, which will make it possible to propose the most appropriate model for the prediction of solar radiation. finally, we make an estimate of available solar energy in nouakchott in the coastal region. data and methodologies study site the site of study located in nouakchott, the capital of mauritania according to the coordinates (15.983˚e, 18.153˚n). a photovoltaic plant of 15 mwp is installed in this site in 2013. the plant is instrumented by a system of measurements of meteorological parameters such as temperature, solar radiation and wind speed. figure 1 illustrates the geographical location of the site. the data collected on this system covers the period of one year (april 1, 2015 to march 31, 2016) and is measured every 5 minutes. calculation method of available solar energy the available solar energy represents the amount of energy received on the ground per unit area (wh/m²). it can be defined as the integral of the solar power received on the ground during a period of 24 hours. this period is often limited to another period corresponding to the interval from sunrise to sunset. available daily solar energy can be calculated using following equation: [5].   dttie cs ls gg   (1) with, ig (t) indicates the instantaneous solar radiation (power received on the ground per unit area) in (w/m²). figure1. geographical location of the site clearness index another parameter to analyze the feasibility of available solar potential will also be calculated. this is the clearness index kt, which is most often calculated using the following equation: h o t g g k  (2) where, go is the solar energy measured on the ground (kwh/m²/d) and gh is the solar energy measured outside the atmosphere (kwh/m²/d). x n , π i g cs h                 365 360 cos003301 24 (3) where, n is the day number of the year, the parameter (x) is given by equation (4). a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p3 ) )sin( sin(l) 180 +)sin( )cos( (cos(l)    x (4) modeling of solar radiation in this phase of the study, four models will be presented to analyze their performance on the nouakchott coast using real data collected on this site. bird and hulstrom model the direct normal irradiance in this model described by bird and hulstrom [6] is in function of absorption and transmittance by the atmospheric components such as of ozone, gas, water and aerosols, and it is given as follows: awgrscn τττττi,i  0 97510 (5) awgor ,τ,τ,τ,ττ (dimensionless) are the rayleigh, ozone, gas, water and aerosols scattering transmittances, respectively. they are given as follows:   011840 109030exp , aa , ar mmm,τ  (6)  26001270exp , ag m,τ  (7)    1 1 682580 11 3856034791495921   u,u,u,τ , w (8)   91080780808730 1exp , a , aa , aa mkkkτ  (9)     12 333 30350 330 00030044010027150481391161101   u.u,u,u,u,τ , (10) where ma (dimensionless) is the air mass at the actual pressure of the site, mr (dimensionless) is the air mass at standard pressure (1013.25 mbar), u1 (cm) is the pressurecorrected relative optical path length of precipitable water, ka (dimensionless) is the optical aerosol thickness and u3 (cm) is the optical path relative to the ozone layer.      25314 06780sin10409sin 1 ,a ,hs,hs m    (11) 1 251013         , p mm ar (12) r mhpu  1 (13) 21 35027580 aλaλa k,k,k  (14) for μm.λ 380 1  and μm,λ 500 2   31, aia λiβk   (15) λi (m) is the wavelength and ßa the angstrom turbidity coefficients. table 3 gives the values of ßa according to the type of site. roz mlu  3 (16) table 1: value of according to the site climate zones a  rural site 0,05 urban site 0,10 industrial site 0,30 p (mbar) is the local aipressure, z (m) is the altitude of studied site, loz(cm) is the vertical ozone-layer thickness and hp (cm) is the precipitable water-vapor thickness. these parameters can be calculated by the following equations.   265510257211013 ,z,p   (17) r oz m,, l   9049 1 (18) diffuse solar radiation d (w/m2) at ground level is a combination of three components corresponding to rayleigh scattering after the first pass through the atmosphere (dr w/m2); the aerosol dispersion after the first passage through the atmosphere (da (w/m2) and the multi-reflection processes between the ground and the sky dm w/m2) all these components are given respectively by the equation following: a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p4 mar dddd  (19)     021 1 150sin790 , ar raawgocs r mm τ,ττττhsi, d    (20)     021 1 1sin790 , ar ascaawgocs a mm τfττττhsi, d    (21)    ag agarn m ρρ ρρddhsi d    1 sin (22) where hs (°) is the solar elevation; isc (w/m2) is the solar constant; ζaa is the transmission factor of direct solar radiation due to aerosol absorption, ζas is the fraction of the incident radiation transmitted after the aerosol scattering effects, ρg (dimensionless) is the ground albedo (set at 0.2) and ρa (dimensionless) is the albedo of cloudless sky.      a , aaaa τmmωτ  1111 061 0 (23) aa a as τ τ τ  (24)     asca τf,ρ  1106850 (25) ω0 (dimensionless) is the single-scattering albedo fraction of incident energy scattered to total attenuation by aerosols and it is taken to be 0.9, fc is the diffusion fraction, it is equal to 0.84. finally, the global radiation g (w/m2) received on a horizontal surface can be written in the form of the following equation.   dhig n  sin (26) ghouard model ghouard et al. (1977) model proposed empirical formulas, which are based on the disturbing factor evaluations depending on the atmospheric conditions and astronomical parameters [7]. the direct solar radiation by this model does not take into account the absorbed and reflected solar flux by the atmospheric components (water vapor, aerosols, ozone …),and it is defined as follows:    hs hs a acii tcs sin sin exp 2 1        (27) the diffuse solar radiation comes from all the space and has no privileged orientation; and it can be calculated as follows:    hs hs a acid tcs sin sin exp2939,0271,0 2 1              (28) the global solar radiation can be calculated by the following equation:              hs a hsacihsacig tcstcs sin expsin706,0sin271,0 2 11 (29) represents the earth-sun distance correction. it can be given by:  2cos034,01  nc t (30) where, n is the day number of the year. ics is the solar constant, a1 and a2 are the coefficients of the turbidity factor, and they are given in the following table 2. table 2: turbidity factors depending on climatic conditions. climatic condition clear sky normal condition covered sky a1 0.87 0.88 0.91 a2 0.17 0.26 0.43 perrin-brichambaut model in 1975, perrin-brichambaut proposed a model, which is a function of astronomical parameters [8]. the above relationships are transformed into the following ones according to the atmospheric conditions:    4,0sin1,0 hscid cs  (31)    hs hsb a ri sin 1sin exp          (32) dig  (33) where, r (w/m2) is the apparent extraterrestrial irradiance. a, b and c (dimensionless) are empirical values to calculate the solar irradiance according to the perrin brichambaut model (table 3). a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p5 table 3: r, a, b and c values according to the perrin brichambaut model. atmospheric condition r a b c clear sky 1210 1,67 3,9 0,67 normal condition 1230 1,61 3,1 0,47 industrial site 1260 2,23 4 0,45 dependent model of the link trouble factor the link trouble factor integrates several forms of attenuation, such as attenuation by clouds, aerosols, water vapor, etc.). these factors are widely used, in the case of missing data to estimate the attenuation of solar radiation for each component of the atmosphere. for this reason, models of solar radiation estimates often use this factor. the global solar radiation on a horizontal plane given by the following equation: idg  (34) where i represents the solar radiation received on the horizontal plane without undergoing modification through the atmosphere. this component can be given by the following equation:    hs hs t ii l cs sin sin4,99,0 exp          (35) where, hs is the solar elevation, tl is the link trouble factor given by the following equation:     vtatal pf.f,,t ln214061442  (36) represents the atmospheric trouble factor. it can take several values depending on the atmospheric nature of the areas. = 0,05 in rural areas; = 0,1 in urban area; = 0,2 in industrial or polluted zone. pv is the partial pressure of water vapor (expressed in mmhg). it can be calculated by the following equation:   sec 101325 760 ppp atv  (37) with pat is the atmospheric pressure (in pascal), psec the dry air pressure, equal to 1,01222*105pa. diffuse solar radiation can be calculated by the following equation:  )sin(5,0)sin(040 hsthsid lcs  (38) models performance validation in addition, the performance of the proposed model has been evaluated based on the following well established statistical error parameters [9]: root mean square error (rmse) the rmse (w/m2) is always positive, a zero value is ideal. this test provides information on the short-term performance of the models by allowing a term by term comparison of the actual deviation between the calculated value and the measured value [10]. it can be expressed by the following equation: (39) mean bias error (mbe) the test of mbe (w/m2) provides information on the long term performance of the models [11]. a positive mbe gives the average amount of over estimation in the predicted value and a negative mbe value gives the average amount of under estimation in the predicted value. it is given by the following equation: (40) coefficient of determination the r2 takes values between 0 and 1. while a value around 1 shows perfect linear relationship between the measured and calculated values, a value around zero indicates the absence of the linear relationship [12]. this coefficient can be expressed by equation (41). (41) (42) k is the total number of observations, ges is the value estimated by the model, gmes is the measured value. results and analysis global solar energy available measurements of global solar radiation collected in nouakchott (cheikh zayed plant) are used to analyze the available solar potential. the application of available solar energy calculation methods and clearness index was used to determine solar a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p6 energy and daily clearness index. the monthly average of these two parameters is calculated. the results obtained are given in table 4. the results shows that solar energy available on the nouakchott coast is quite large. the values obtained varies from 5023.07 wh/m²/d (december) to 7117.18 wh/m²/d observed for the month of april. the corresponding clearness indices are 0.67 for the two months, respectively. these results show the clarity of the sky during these two months (kt greater than 65%). the results of the clearness index obtained (table 4) show in the majority of cases (75% of the time), that the clearness index corresponds to clear sky days. for the months of february, june and august, the clearness index is less than the clear-sky threshold. the values remain however high (higher than 60%). table 4: monthly average of extraterrestrial solar irradiation, global solar irradiance on ground and clearness index months solar energy on the ground g (wh/m²/d) solar energy outside the atmosphere g h (wh/m²/j) clearness index k t (-) january 5390,21 7807,94 0,69 february 5472,16 8772,77 0,62 march 6939,06 9851,57 0,70 april 7117,18 10584,86 0,67 may 7004,98 10845,87 0,65 june 6640,87 10859,26 0,61 july 6997,18 10792,69 0,65 august 6510,48 10566,52 0,62 september 6840,42 9938,71 0,69 october 6076,91 8917,93 0,68 november 5348,61 7910,39 0,67 december 5023,07 7455,46 0,67 distribution of available solar energy the data collected on the nouakchott coast are also used to study the distribution of available solar energy. the daily solar energies calculated from these measurements are therefore used. the frequency and cumulated frequency of each energy varies from 0 to 9 kwh/m²/d in steps of 0.5 are determined. the results obtained are illustrated in figure 2 (a and b). figure2 (a) shows that daily solar energy is available at different frequencies. these energies vary between 1 and 8 kwh/m²/d. for energy variations in the interval between 0 and 4 kwh/m²/d, the available frequencies are low (less than or equal to 1.5%). on the other hand, for energy variations in the interval between 4 and 8 kwh/m²/d, the frequency of the energy is between 6 and 22%. the highest frequency (22%) is obtained for the daily energy of 7 kwh/m²/d. these results show that a pv generator installed on the nouakchott coast can operate at a rate of 22% with available solar energy of 7 kwh/m²/d. the results of the cumulated distribution (figure 2 (b)) show that the daily energies frequency less than or equal to 5 kwh /m²/d is 6%, which means that during 94% of time, a pv generator can operate at available solar energy above 5 kwh/m²/d. this value is greater than average solar energy in many parts of the world [5]. figure 2 (a), (b): daily distribution of available solar energy a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p7 analysis of the clearness indices distribution the results obtained from daily clearness index calculations are used to analyze the distribution. thus, the frequency distribution and the cumulated distribution are indicated in figure 3 (a and b). it can be seen that there nearly exist no clearness index between 0 and 0.35, the frequency observed in this interval being 1.5% at most. for the clearness index between 0.35 and 0.65, the observed frequency can reach 25%. the highest frequency is observed for the clearness index greater than 65%. indeed, the figure (3b) of the cumulated distribution illustrates that the frequency for which clearness index is less than or equal to 0.65 is about 25%, so 75% of the time represents a clearness index greater than 0.65. we can say that 75% of the time, the sky is clear with a cloud cover almost nil. this is interesting for a photovoltaic or thermal application using global solar radiation. figure 3 (a), (b): distribution of the clearness index model performance analysis this study part presents the results obtained on solar radiation modeling. the four models presented above are studied by determining the solar radiation in steps of 5 minutes for cases of clear sky days where kt is greater than or equal to 65%. the results obtained as a result of the calculation are compared with the measurements corresponding to the measurement period. thus, the parameters of performance analysis of the models such as the root mean square error, the coefficient of determination, the mean error between the measurements and the predicted values are determined for each model. the results obtained are shown in table 5. table 5: model performance parameters type of models mbe (w/m2) rmse (w/m2) r2 (-) ghouard -0,54 79,69 0,962 trouble of link -4,83 79,74 0,960 bird and hulstrom 5,88 81,66 0,959 perrinbrichambaut -40,78 102,83 0,935 the results (table 5) show that the models give good results with a coefficient of determination greater than 93%. it should be noted that the ghouard model gives, however, better results with a mean error of 0.54 w / m2, a root mean square error of 79.69 w / m² and the corresponding coefficient of determination of 96.2%. the results also shows that the highest errors are observed for the perrin-brichambaut model, so the perrin brichambaut model is the worst performer at the nouakchott site. the observed errors are 40.78 and 102.83 w/m² for the mean error and mean squared error respectively. the corresponding coefficient of determination is 93.5%. these results are comparable to those found in reference [7]. we also find that ghouard, perrin-brichambaut models and the dependent model of link trouble factor underestimate the measures, and the bird and hulstrom model overestimate the measures. figure 4 illustrates the pace of the solar radiation calculated by the four models and the measured solar radiation. these results represent the solar radiation of a typical clear-sky day, calculated over the period of the year after having subtracted 25% of the data corresponding to the averagely covered sky and / or covered corresponding to kt lower than 65%. it can be noted that the times of sunrise and sunset correspond for all the models and the measurements as well as the time of the maximum solar radiation. the maximum observed difference between the measured and calculated solar radiation is 16.67%, for the perrin brichambaut model and the minimum difference is 7.7% observed for the ghouard model. solar radiation calculated and measured for days with clear skies are also used to analyze the distribution. the cumulated distribution is then determined for the four models and for the a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p8 measurements. the results obtained are illustrated in figure 5. it can be seen that solar radiation less than or equal to 500 w / m² is available at a time percentage between 50% (model using the link trouble factor) and 70% (perrinbrichambaut). the percentage corresponding to the measurements is about 65%. for solar radiation greater than 500 w / m², the time percentage is 50%, 30% and 45% for the three cases (model using the link trouble factor, perrin-brichambaut model and the measurements) respectively. figure 4: solar radiation measured and calculated as a function of time figure 5: cumulated distribution of solar radiation calculated and measured solar energy the solar radiation calculated for each model over one year period has been used to estimate the solar potential available. thus, the available daily solar energy is calculated on the period of each month using the equation 1, the results of the calculations are presented in figure 6. the results show that the calculated solar energies follow the same pace for all models with a significantly difference between the models. on the other hand, the measured solar energy shows a significant and stable potential for the months of september, october, november, december and january. these high values of available solar energy observed for measurements can be explained by the significance of the solar radiation intensity essentially due to a lack of cloud cover and low attenuation of solar radiation during the indicated period. indeed, the clearness index observed for these months is greater than 65%, which corresponds to days with clear skies. figure 6: measured and calculated monthly solar energy variation distribution of calculated energies the energy calculated for clear-sky days is also used to determine the available energy distribution by taking into account the same step of variation of previously adopted energies. the results obtained are illustrated by figure 7. it can be seen that for energies less than or equal to 5 kwh/m²/d, the frequency is equal to zero. this can be explained that the days whose energy is less than 5 kwh/m²/d corresponds to covered or averagely covered sky, so are not taken into account in the calculation. a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p9 figure 7 (a), (b), (c), (d), (e): distribution of calculated and measured energies conclusion the objective of this study is to characterize and model solar radiation received on a horizontal plane for the nouakchott site. for this, measurements collected on the cheikh zayed plant are used. these data measured in steps of 5 minutes covering the period of a year, include measurements on solar radiation, wind speed and ambient temperature. in order to estimate the available solar potential, an available solar potential estimation approach using real measurements is presented. the application of this approach made it possible to calculate the available solar energy and the clearness index. the results obtained showed that the available solar potential is very important (greater than 5 kwh/m²/d). a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p10 in order to choose an appropriate model to predict the solar radiation available on a horizontal plane for the nouakchott region, four of the most used models in the literature are presented. there is the model of ghouard, perrinbrichambaut, bird and hulstrom and the model dependent on the link trouble factor. the performance of these four models is also studied by determining the determination coefficient , the mean squared error and the mean error between the calculated value and the measured value. the performance analysis is performed considering the one-year period of measurements. the results obtained showed that, overall, the models give good results (with a coefficient of determination (r2) greater than 93%). these models can, therefore, be used to estimate global solar irradiance for nouakchott site and for locations with climates similar. in this study, we showed that the best results are however obtained with the ghouard model. in perspective, it is important to characterize and model the available solar potential using a longer period (10 years) and for other regions of mauritania and sub-regions to take into account the influence of spatiotemporal variation on the available potential and on the quality of solar radiation modeling. complementary informations on authors: ahmed sidibba: sidiabaahmed@gmail.com, research gate (ahmed sidibba) boudy bilal: boudy_bilal@yahoo.fr, research gate (boudy bilal), diene ndiaye: diene.ndiaye@ugb.edu.sn, research gate (diene ndiaye) sidi bouhamady: sbouhamady@gmail.com, menny el bah: mennyfr@yahoo.fr, references [1]samira mc. statistical study of solar radiation on an inclined plane, thesis defended in 2012 in the university of aboubeker belkaid. [2] m. capderou, 'solar atlas of algeria, tome 1, vol 1 and 2: theoretical and experimental models', university publications offices, algeria, 1987. [3] zhang qy. huang yj. development of typical year weather files for chinese locations. ashrae transactions 2002; 108(2):1063-75. [4] chen, r., k. ersi, j. yang, s. lu and w. zhao. validation of five global radiations models with measured daily data in china. energy conversion and management 2004, 45:1759–69. [5] bilal b. implementation of new multi-objective optimization approaches for hybrid wind-solar-battery-generator systems. university thesis, esp-ucad, 2012, no19, 145p. [6] bird re, hulstrom rl. a simplified clear sky model for direct and diffuse insolation on horizontal surfaces. golden, co: solar energy research institute; 1981 seri/tr-642-761. [7] mghouchi y. el bouardi a., choulli z., ajzoul t., models for obtaining the daily direct, diffuse and global solar radiations .renewable and sustainable energy reviews, 2016, 56, 87–99. [8] perrin de brichambaut c. 'estimation of energy resources in france', 1975, notebooks of the a.f.e.d.e.s, n ° 1. [9] stone rj. improved statistical procedure for the evaluation of solar radiation estimation models. sol energy 1993;51(4):289–91. mailto:sidiabaahmed@gmail.com mailto:boudy_bilal@yahoo.fr mailto:diene.ndiaye@ugb.edu.sn mailto:sbouhamady@gmail.com mailto:mennyfr@yahoo.fr a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p11 [10] katiyar a.k., kumar a., pandey c.k. and das b. a comparative study of monthly mean daily clear sky radiation over india’, international journal of energy and environment, ijee, vol. 1, n°1, pp. 177 – 182, 2010. [11] zekai sen, ‘solar energy fundamentals and modelling techniques’, edition springer, 2008. [12] kerkouche k., cherfa f., hadj a., arab bouchakour s., abdeladim k. et bergheul k., evaluation of the global solar irradiation on an inclined surface according to different models for the site of bouzaréah, revue of renewable energies vol. 16 no. 2, 2013, 269-284. a. sidibba et al characterization and modeling of solar radiation on the ground oaj materials and devices, vol 4 (1), 1702 (2019) – doi: 10.23647/ca.md20191702 p12 important: articles are published under the responsability of authors, in particular concerning the respect of copyrights. readers are aware that the contents of published articles may involve hazardous experiments if reproduced; the reproduction of experimental procedures described in articles is under the responsability of readers and their own analysis of potential danger. reprint freely distributable – open access article materials and devices is an open access journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed and encouraged! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations soon. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attributionnoncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. aims and scope of the journal : the topics covered by the journal are wide, materials and devices aims at publishing papers on all aspects related to materials (including experimental techniques and methods), and devices in a wide sense provided they integrate specific materials. works in relation with sustainable development are welcome. the journal publishes several types of papers : a: regular papers, l : short papers, r : review papers, t : technical papers, ur : unexpected and « negative » results, conf: conference papers. 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dynamics simulations s. el-moudny (1), m. benhamou (2), m. badia (3), m. ossmani (4) (1) physics department, faculty of sciences, moulay ismail university, morocco, elmoudny.soukaina@gmail.com (2) physics department, faculty of sciences, moulay ismail university, morocco, benhamou.mabrouk@gmail.com (3) physics department, royal air school, morocco (4) ensam, moulay ismail university, morocco corresponding author : elmoudny.soukaina@gmail.com received: 30 january 2018 / received in final form: 17 april 2018 / accepted: 24 april 2018 abstract : in this work, we aim at an extensive study of the diffusion phenomenon of oil-droplets dispersed in water onto which are strongly adsorbed charged point-like particles (pickering emulsions). this diffusion that originates from multiple collisions with the molecules of water, is anomalous, due to the presence of relatively strong correlations between the moving oil-droplets. using molecular dynamic simulation, with a pair-potential of sogami-ise type, we first observe that the random walkers execute a normal diffusion, at intermediate time, followed by a slow diffusion (subdiffusion) we attribute to the presence of cages, formed by the nearest neighbors (traps). in the cage-regime, we find that the mean-square-displacement increases according to a time-power law, with an anomalous diffusion exponent, 𝛼 (between 0 and 1). the existence of a cage effect is shown also by computing the velocity auto-correlation function of the random walker. it is found that, in a cage, this function is governed by an underdamped (oscillatory) behavior, for strong densities and surface charges, and low-salt concentration. in the inverse situation, however, we observe that this correlation-function is rather overdamped (non-oscillatory). in the two cases, at large-time, this function fails according to a time-power law, with the exponent 𝛼 − 1. keywords : pickering emulsions, sogami-ise potential, anomalous diffusion, cage effect, mean square displacement introduction pickering emulsions are emulsions that are stabilized by solid particles. in fact, the solid particles form a spherical shell and impede coalescence when two droplets approach each other. pickering emulsifiers irreversibly adsorb at the oil–water interface and require a much higher energy for desorption (≈ 106 − 108 𝑘𝐵 𝑇) as compared to the conventional surfactants ( ≈ 7 𝑘𝐵 𝑇 ). the emulsifier-free character of pickering emulsions makes them attractive regarding applications where the surfactants have detrimental effects, in particular, when contacted with living matter for health and body care applications [1]. pickering emulsions have been the focus of considerable research in the past decade due to their properties such as high stability with respect to the coalescence, as well as, due to advances in nanotechnology that allows us to create and characterize the nano-scale structures in new ways. in fact, the colloidal assembly of solid particles within pickering emulsions can be used as templates for advanced materials such as janus colloids, composite particles, and colloidosomes. mailto:elmoudny.soukaina@gmail.com mailto:benhamou.mabrouk@gmail.com mailto:soukaina@gmail el-moudny et al – extensive study of cage effect and subdiffusion in pickering emulsions using molecular dynamics simulations oaj materials and devices, vol 3 #1, 2404 (2018) – doi: 10.23647/ca.md20182404 a pickering emulsion has a complex structure which presents as a dispersion of droplets of a liquid (dispersed phase) in another (host liquid). each droplet is surrounded by discrete spherical particles arranged on the surface. if the preparing conditions (such as wettability, charge, concentration, shape and size of particles, as well as, the ph and salt concentration in aqueous phase) are right, the clothed droplets can be considered as "soft-colloids". due to the thermal agitation, the clothed droplets experience a (lateral) diffusion with the molecules of the continuous phase. at the beginning, a single clothed droplet normally diffuses, but at large-time, this motion is hampered by the presence of the others, and then, the same clothed droplet executes rather an anomalous diffusion we are interested in. as we shall see below, quantitatively, this anomalous phenomenon mainly depends on the pertinent parameters, such as the surface charge of the droplets, their number density, and the salt-concentration. in this work, we quantitatively study the anomalous diffusion within pickering emulsions using the molecular dynamics (md) simulations. the dynamic properties are investigated through the time-evolution of the mean-square-displacement (msd) combined with the velocity auto-correlation function (vacf). for this purpose, we adopted the sogami-ise (si) pair-potential [2] between charged clothed droplets. it presents as the sum of a repulsive screened coulomb potential and an attractive tail. for the dynamics study, our starting point is a proposition of a relevant dynamic theory, based on the langevin equation and its generalization (with memory). we then write an integro-differential equation for vacf and its relations with msd. the exact solution of this equation, with an appropriate choice of the memory-function, enables us to valid the obtained results from md as a computer experiment. pair-potential expression consider a suspension of 𝑁 droplets (soft-colloids) of a liquid that are dispersed in another liquid of different chemical nature. in this study, we restrict ourselves to oil-in-water dispersions, only. the volume of the solution is denoted as 𝑉, and the oil-droplet number density as 𝜌 = 𝑁 𝑉⁄ . for simplicity, these oil-droplets are assumed to be monodisperse spheres of common diameter 𝜎 . the surface of each oil-droplet is wetted by 𝑍 irreversibly adsorbed charged particles of small diameter in comparison with 𝜎. the strong adsorption of the particles rigidifies the surface of the oil-droplets, so they can be viewed as soft spherical colloids (as latex particles in water, for instance) that carry the same charge 𝑍𝑒 (macroions). when they are added to the solution, the adsorbed particles are ionized and release small ions (counterions) in the solution. generally, the colloids are in contact with other free ions resulting from a dissociation of a salt or an electrolyte. it is well-known that the surrounding mobile ions leads to a screening of the coulomb forces between macroions (oil-droplets). beside the screened coulomb interactions, the macroions experience attractive van der waals ones, and the thermodynamic properties (phase transitions, structure...) of the system can be described correctly within the framework of the so-called derjaguin-landau-verwey-overbeek (dlvo) theory [3]. in the same context, in his seminal paper [2], i. sogami used a self-consistent theory combined with a resolution of the poisson-boltzmann equation, satisfied by the electric potential created by the macroions (ionized latex polyballs), for the determination of their associated effective interaction potential. such a potential involves a short-range (screened) coulomb repulsion, whose origin is self-evident, in addition to a long-ranged exponential attractive tail. the expression of the si potential between charged oil-droplets reads [2] 𝑈(𝑟) 𝑘𝐵𝑇 = 𝑙𝐵 [ 𝑍𝑠𝑖𝑛ℎ(𝜅𝜎/2) 𝜅𝜎/2 ] 2 [ 1+(𝜅𝜎/2)coth (𝜅𝜎/2) 𝑟 − 𝜅 2 ] 𝑒 −𝜅𝑟 (1) for 𝑟 > 𝜎 . in this expression, the screening parameter 𝜅 is defined by the standard relation 𝜅2 = 4𝜋𝑙𝐵 ∑ 𝜌𝑖 𝑧𝑖 2 𝑖 (2) here, 𝑙𝐵 = 𝑒 2/ 𝑘𝐵 𝑇 denotes the bjerrum length, which is a characteristic length-scale at which the electrostatic interaction between a pair of monovalent ions has magnitude 𝑘𝐵 𝑇. the length 𝑙𝐵 has the value 𝑙𝐵 = 0.7 𝑛𝑚, for water, at room temperature (this length is kept fixed to this value). throughout this work, the temperature 𝑇 will be fixed to the value 298 𝐾 (room temperature). in the presence of a salt of concentration, 𝐶𝑠, the above formula becomes 𝜅2 = 4𝜋𝑙𝐵 (𝜌𝑍 2 + 𝐶𝑠 ) (3) figure 1 shows the variation of the reduced si pair-potential 𝑈(𝑟)/ 𝑘𝐵 𝑇, with the dimensionless distance, 𝑟/𝜎, for various values of the salt-concentration. these curves are drawn with parameters: 𝜌∗ = 0.002, 𝑍 = 500 and 𝜎 = 5000 å. 1,0 1,2 1,4 1,6 1,8 2,0 2,2 -0,4 0,0 0,4 0,8 r /  u(r) / k b t c s =0.29 m c s =1.79 m c s =3.45 m c s =5.11 m figure 1: dimensionless si pair-potential, 𝑼(𝒓)/𝒌𝑩𝑻 , versus the dimensionless distance. finally, we note that, using this potential, tata and coworkers [4] performed monte carlo (mc) and brownian dynamics simulations, and the obtained results agree well with certain experimental observations [5,6]. also kepler and fraden [7] determined the pairpotential of the colloidal particles from measurements of the pair correlation-function of both dilute and moderately concentrated dispersions. thus, the determined pair-potential can be reproduced by si potential assuming 𝐶𝑠 = 1.75 × 10²¹ 𝑚⁻³ , as pointed out by tata and arora [8]. the authors argued that the results by kepler and fraden supported the counterion-mediated attraction discussed by sogami. el-moudny et al – extensive study of cage effect and subdiffusion in pickering emulsions using molecular dynamics simulations oaj materials and devices, vol 3 #1, 2404 (2018) – doi: 10.23647/ca.md20182404 results and discussions theory: normal diffusion: consider a given clothed oil-droplet, termed tracer, which experiences a normal diffusion, for early times, because of the absence of the correlations. at these small-time-scales, the random walker is not yet trapped in a cage. as we shall below, such a regime will be put in evidence by our computer simulations, for smaller times. the brownian motion of the tracer can be described by the following phenomenological langevin equation 𝑀 𝑑𝒗(𝑡) 𝑑𝑡 = − 𝒗(𝑡) + 𝑭𝑠 (𝑡) (4) the friction coefficient, , is related to the viscosity of the emulsion, , and the oil-droplet radius, 𝑅, by the classical stokes relation: = 6𝜋 𝑅 . of course, the viscosity of the solution depends on the number density of the dispersed oildroplets, 𝜌. come back to the stochastic force and note that this is considered to be a white noise with 〈𝑭𝑠 (𝑡)〉 = 0 (5) 〈𝑭𝒔(𝑡). 𝑭𝒔(0)〉 = 6𝑘𝐵 𝑇 𝛿(𝑡) (6) 〈𝒗(0). 𝑭𝒔(𝑡)〉 = 0 (7) now, we are interested in two related physical quantities: velocity auto-correlation function (vacf), 〈𝒗(𝑡). 𝒗(0)〉 ≡ 𝑐𝑣𝑣 (𝑡), and mean-square-displacement (msd), 〈[𝒓(𝑡) − 𝒓(0)]²〉 ≡ 𝑊(𝑡). vacf solves the following differential equation [9] 𝑑𝑐𝑣𝑣(𝑡) 𝑑𝑡 = −𝛾𝑐𝑣𝑣 (𝑡) (8) its solution is simply 𝑐𝑣𝑣 (𝑡) = 〈𝒗²〉𝑒 −𝛾𝑡 , 〈𝒗²〉 = 𝑐𝑣𝑣 (0) = 3 𝑘𝐵𝑇 𝑀 (9) with the mass weighted friction constant 𝛾 = /𝑀 , called relaxation rate. on the other hand, vacf and msd are related by [9] 𝑊(𝑡) = ∫ 𝑑𝑡1 ∫ 𝑑𝑡2𝑐𝑣𝑣(𝑡1, 𝑡2) 𝑡 0 𝑡 0 = 2 ∫ 𝑑𝑡 ′ 𝑡 0 (𝑡 − 𝑡 ′)𝑐𝑣𝑣(𝑡′) (10) replacing vacf by its explicit expression (9) in eq. (10) yields the following time-evolution of msd [9] 𝑊(𝑡) = 6 𝑘𝐵𝑇 𝑀 ( 𝑒−𝛾𝑡−1+𝛾𝑡 𝛾² ) (11) for times much longer than the inverse relaxation rate, that is for 𝑡 ≫ 𝛾 −1 ≡ 𝑡∗, msd grows linearly with time, and we have 𝑊(𝑡) = 6𝐷𝑡, 𝑡 ≫ 𝑡 ∗ (12) the linear growth of msd with time is then reached beyond the characteristic time 𝑡 ∗ = 𝑀 6𝜋𝑅𝜂(𝜌) (13) this time limit depends only on oil-droplet density through the viscosity (𝜌). if, in contrast, 𝑡 << 𝑡∗, we can approximate 𝑒 −𝛾𝑡 by 1 − 𝛾𝑡 + 𝛾²𝑡²/2, and find 𝑊(𝑡) = 〈𝒗²〉𝑡 2 = 3 𝑘𝐵𝑇 𝑀 𝑡², 𝑡 ≪ 𝑡 ∗ (14) which shows that msd grows as 𝑡² (ballistic motion). anormal diffusion: now, the raised question is how the tracer moves beyond the relaxation rate, 𝑡∗. in this time domain, the tracer (target) feels to be trapped in a cage formed by others clothed oil-droplets (traps), and cannot escape from this cage only after a long-time. as consequence, the presence of the traps makes difficult such a diffusion process, and then, the random walker executes rather a subdiffusion, characterized by an exponent denoted as 𝛼. to discuss the cage effect and the subdiffusion laws, the starting point is a generalized langevin equation [9], 𝑑𝒗(𝑡) 𝑑𝑡 = −𝛾𝒗(𝑡) − ∫ 𝑑𝑡 ′𝜅(𝑡 − 𝑡 ′)𝒗(𝑡 ′) + 𝑭𝑠 (𝑡) 𝑡 0 (15) where 𝜅 is the memory-function that expresses the friction retardation. we note that this random force 𝐹𝑠 (𝑡) satisfies equality (5) and (7), but with the second moment (generalization of eq. (6)) 〈𝑭𝒔(𝑡). 𝑭𝒔(0)〉 = 6𝑀𝑘𝐵 𝑇[𝛾𝛿(𝑡) + 𝜅(𝑡)] , 𝑡 > 0 (16) oscillating regime: in this regime, the random walker is subject to oscillations before it undergoes a subdiffusion process. therefore, the tracer moves in a harmonic potential resulting from its interactions with the surrounding nearest neighbors. this equivalent to take for the memory-function the following form 𝜅(𝑡) = 𝜔0 2 (𝑡) (17) the frequency 𝜔₀ must be considered as a phenomenological parameter that depends, of course, on the essential parameters of the problem. in these conditions, the integro-differential equation (15) writes 𝑑𝑐𝑣𝑣(𝑡) 𝑑𝑡 = −𝛾𝑐𝑣𝑣 (𝑡) − 𝜔0 2 ∫ 𝑑𝑡 ′𝑐𝑣𝑣 (𝑡 ′) . 𝑡 0 (18) using laplace transform, we find that vacf presents three regimes: • the underdamped regime (𝛾 < 2𝜔0): 𝑐𝑣𝑣 (𝑡) = 〈𝑣²〉𝑒 −𝛾𝑡/2 {𝑐𝑜𝑠(𝜔 ̃0𝑡) − 𝛾 2𝜔 ̃0 𝑠𝑖𝑛(𝜔 ̃0𝑡)} (19) with the notation: 𝜔 ̃0 = √𝜔0 2 − 𝛾2 4 . • the overdamped regime (𝛾 > 2𝜔0): 𝑐𝑣𝑣 (𝑡) = 〈𝑣²〉𝑒 −𝛾𝑡/2 {𝑐𝑜𝑠ℎ(𝜔 ̂0𝑡) − 𝛾 2𝜔 ̂0 𝑠𝑖𝑛ℎ(𝜔 ̂0𝑡)} (20) with the notation: 𝜔 ̂0 = √ 𝛾2 4 − 𝜔0 2 . • the critical regime (𝛾 = 2𝜔0): 𝑐𝑣𝑣 (𝑡) = 〈𝑣²〉𝑒 −𝛾𝑡/2 (1 − 𝛾𝑡 2 ) (21) el-moudny et al – extensive study of cage effect and subdiffusion in pickering emulsions using molecular dynamics simulations oaj materials and devices, vol 3 #1, 2404 (2018) – doi: 10.23647/ca.md20182404 such a regime separates the oscillating regime and the nonoscillating one. using the relation (10) between msd and vacf, we find that msd also presents three regimes: • the underdamped regime ( 𝛾 < 2𝜔0): 𝑊(𝑡) = 6 𝑘𝐵𝑇 𝑀𝜔0 2 [1 − 𝑒 − 𝛾𝑡 2 {𝑐𝑜𝑠(�̃�0𝑡) + 𝛾 2�̃�0 𝑠𝑖𝑛(�̃�0𝑡)}] (22) • the overdamped regime ( 𝛾 > 2𝜔0): 𝑊(𝑡) = 6 𝑘𝐵𝑇 𝑀𝜔0 2 [1 − 𝑒 − 𝛾𝑡 2 {𝑐𝑜𝑠ℎ(�̂�0𝑡) + 𝛾 2𝜔 ̂0 𝑠𝑖𝑛ℎ(�̂�0𝑡)}] (23) • the critical regime ( 𝛾 = 2𝜔0): 𝑊(𝑡) = 24 𝑘𝐵𝑇 𝑀𝛾² [1 − 𝑒 −𝛾𝑡/2 (1 + 𝛾𝑡 2 )] (24) in contrary to the freely diffusing brownian particle, msd approaches a plateau value in the limit 𝑡 → ∞, independently of the dynamic regime, 𝑊(𝑡) = 6 𝑘𝐵𝑇 𝑀𝜔0 2 , 𝑡 ≫ 2𝛾 −1 ≡ 𝑡 ∗∗ (25) then, this corresponds to the plateau regime where 𝛼𝑝 = 0. subdiffusive regime: beyond the plateau regime, the random walker executes a slow motion, and the corresponding msd obeys the law 𝑊(𝑡) = 〈[𝒓(𝑡) − 𝒓(0)]²〉 = 2𝐷𝛼 𝑡 𝛼 , (0 < 𝛼 < 1) (26) the normal diffusion with 𝑊(𝑡) ∼ 𝑡 (large-time) corresponds to a vanishing vacf, that is 𝑐𝑣𝑣 (𝑡) = 0 (large-time), whereas 𝑐𝑣𝑣 (𝑡) ≠ 0 in the case of an anomalous diffusion. specifically, 𝑐𝑣𝑣 (𝑡) < 0 corresponds to the subdiffusion (since 𝛼 < 1), and 𝑐𝑣𝑣 (𝑡) > 0 to the superdiffusion (since 𝛼 > 1). we note that for the determination of the diffusion exponent, 𝛼, we shall use relation (26), expressed in log-log scale. this exponent is 1, for normal diffusion regime, 0, for the plateau regime, and between 0 and 1, for the subdiffusive one. to sum up, we say that we have now all necessary theoretical ingredients for the explanation of the results from our md simulations. this is the aim of the next section. results from md simulation: spirit of md simulation: within the framework of md method for the description of the dynamic properties of pickering emulsions, the equations of motion are solved in the canonical ensemble using the velocity verlet algorithm (va) [10] with the thermostat of berendsen [11], in order to keep the temperature constant. periodic boundary conditions are applied to remove the surface effects and simulate an infinite system. in the following, we will use dimensionless units, where the length unit is 𝜎, time in units of 𝜏 = 𝜎√(𝑀/𝜖), 𝑘𝐵 𝑇 is the energy unit, and 𝐿₀ = 𝑁 × (6𝑉/𝜋𝑁)1/3 is the box-size, where 𝑉 is the volume of simulation box (in periodic conditions). md simulations where carried out with 1728 particles and the dimensionless time-step for the velocity va is chosen to be 0.05. surface charge effects: in this paragraph, we will look at the influence of the surface charge of the clothed oil-droplets on their dynamic properties. for the study, the size of the oildroplets, their reduced number density and the saltconcentration are fixed to the values: 𝜎 = 20000 å, 𝜌∗ = 0.0020 and 𝐶𝑠 = 2.91 𝜇𝑀. their valence 𝑍 is ranged from 1000 to 4500. figure 2 shows the log-log plot of the reduced msd upon dimensionless time, 𝑡/𝜏 , for various values of the oil-droplet surface charge. we first remark that, for times less than a (dimensionless) transition time 𝑡₁ ≃ 2.483, which is independent of the surface charge, the curves for different surface charges are superposed, and the random walker experiences a normal diffusion, that is 𝑊(𝑡) = 6𝐷𝑡 , the reduced normal diffusion coefficient is 𝐷 = 14.120 . this simulated normal regime is in perfect agreement with the theoretical predictions relatively to the normal diffusion regime discussed above, eq. (12). the existence of the normal diffusive regime can be understood as follows. in the intermediate times, the random walkers (oildroplets) do not feel to be correlated, whatever are the values of their surface charge. for larger times, however, the situation is quite different, and the dynamic of the oil-droplets depends heavily on the surface charge, and msd behaves rather as 𝑊(𝑡) ∼ 𝑡𝛼, with an average subdiffusion exponent 𝛼𝑐 = 0.418 (the subscript c is for charge). in agreement with the theory described above, we remark that the normal diffusion is followed by a transient plateau-like regime, which precedes the subdiffusion one. the existence of this plateau regime is conform with the theoretical eq. (25). this implies the formation of cages, where a given clothed oil-droplet is surrounded by their nearest neighbors. as shown in figure 2, the plateau is more and more pronounced, for strong surface charges. we also remark that the crossover time between the plateau-like regime and the subdiffusion one, 𝑡₂, depends on the value of the surface charge. this means that the moving oildroplet needs more time to break free of the cage of its nearest neighbors, as the surface charge increases. physically, for higher surface charges, the available space for the oil-droplets becomes effectively reduced by the volume-excluding, because the repulsion becomes more important. this leads to a slowing down of the diffusion process of the oil-droplets, which stay localized for some time that increases with increasing surface charge. this behavior is reflected in vacfs displayed in figure 3, for the same values of the oil-droplet surface charge. vacfs are characterized by an underdamped (oscillatory) decay, more pronounced, for higher surface charges, in perfect agreement with the theoretical eq. (19). this underdamped feature can be related to the confinement of the particle in the cage formed by its nearest neighbors, and means that the diffusion process is not markovian, but rather has memory [9]. for low-surface charges, however, we see that vacf is rather an overdamped function, which is conform with the theoretical expression (20). we also observe that, for any value of the surface charge, the tail or the long-time behavior of vacfs, which reflects the diffusional regime of the oil-droplets under consideration, approaches asymptotically zero, from negative values. therefore, the oil-droplets display a subdiffusion. this negative region indicates that, on average, a displacement of the oildroplets toward its nearest neighbors is followed by a displacement back toward its initial position. in other words, it reflects the fact that the velocity of the oil-droplets is, on average, reversed by repulsion with the cage of nearest neighbors. el-moudny et al – extensive study of cage effect and subdiffusion in pickering emulsions using molecular dynamics simulations oaj materials and devices, vol 3 #1, 2404 (2018) – doi: 10.23647/ca.md20182404 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 lo g (m e a n s q u a re d is p la c e m e n t) log(time) z=1000 z=1500 z=2000 z=2500 z=3000 z=3500 z=4000 z=4500 figure 2 : msd versus the dimensionless time, 𝒕/𝝉 , in log-log scale, for various values of surface charge 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time z=1000 z=1500 z=2000 z=2500 z=3000 z=3500 z=4000 z=4500 figure 3: vacf versus the dimensionless time, 𝒕/𝝉, for various values of surface charge density effects: to study the influence of the density of the clothed oil-droplets on their dynamics, we keep fixed their surface charge and size, and the salt-concentration to the values: 𝑍 = 2000, 𝜎 = 20000 å and 𝐶∗ = 2.91 𝜇𝑀, and vary this density. in figure 5, we depict the log-log plot of msd against the dimensionless time, 𝑡/𝜏 , for various values of the oil-droplet density. we first remark that for 𝑡 < 𝑡₁′ , with 𝑡₁′ = 1.449 (reduced transition time), msds are straight lines of the same slope, but decrease as the oil-droplet density is increased, in perfect agreement with the theoretical formula (13). then, the random walker follows a normal brownian diffusion, whose msd is 𝑊(𝑡) = 6𝐷(𝜌)𝑡, for 𝑡 < 𝑡₁′. here 𝐷 is the usual diffusion constant. second, for 𝑡 > 𝑡₁′, we assist to a cage effect, where msds are very sensitive to the variation of the oil-droplet density, and exhibit a subdiffusive behavior, with an average subdiffusion exponent 𝛼𝑑 = 0.432 (the subscript d is for density). before, msds exhibit a plateau regime that becomes more and more pronounced. the existence of such a regime agrees well with the theoretical formula (25). the subdiffusive behavior evoked above is clearly shown in figure 6 representing the variation of vacfs upon the reduced time, 𝑡/𝜏, for different values of the oil-droplet density. from these plots, we see that the negative region of vacfs becomes larger as the oil-droplet density increases. in particular, we observe that vacf is underdamped (oscillatory) for stronger densities, and overdamped for lower ones, in perfect agreement with theoretical formulae (19) and (20), respectively. in addition, the same plots indicate that vacfs tails approach asymptotically zero, from negative values. this means that the oil-droplets undergo a subdiffusion. -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 lo g (m e a n s q u u a re d is p la c e m e n t) log(time)   =0.0010   =0.0015   =0.0020   =0.0025   =0.0030   =0.0032 figure 4: msd versus the dimensionless time, 𝒕/𝝉 , in loglog scale, for various values of the oil-droplet density 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time  * = 0.0010  * = 0.0015  * = 0.0020  * = 0.0025  * = 0.0030  * = 0.0032 figure 5: vacf versus the dimensionless time, 𝒕/𝝉, for various values of the oil-droplet density salt-concentration effects: now, we fix the surface charge, size and reduced number density of the oil-droplets to the values: 𝑍 = 500 , 𝜎 = 5000 å and 𝜌∗ = 0.0020 , and vary progressively the salt-concentration, 𝐶𝑠. the aim is to quantify the effects of this concentration on the diffusion process executed by a given clothed oil-droplet. we represent in figure 8 the log-log plot of msd upon the dimensionless time, 𝑡/𝜏 , for various values of the saltconcentration. we first observe that, for 𝑡 < 𝑡₁′′, with 𝑡₁′′ = 1.439 (reduced transition time), msds increase linearly with time, and have practically the same slope, whatever is the value of the salt-concentration. this means that the tracer experiences a normal brownian diffusion, whose msd is 𝑊(𝑡) = 6𝐷𝑡, for 𝑡 < 𝑡₁′′, with the (reduced) normal diffusion coefficient 𝐷 = 14.186, in perfect agreement with the theoretical equation (13). second, for larger times ( 𝑡 > 𝑡₁′′ ), msds become very sensitive to the variation of the salt-concentration, and present a subdiffusive behavior, due to the cage effects, with an average subdiffusion exponent 𝛼𝑠 = 0.467 (the subscript s is for salt). el-moudny et al – extensive study of cage effect and subdiffusion in pickering emulsions using molecular dynamics simulations oaj materials and devices, vol 3 #1, 2404 (2018) – doi: 10.23647/ca.md20182404 before this regime is attenuated, msds exhibit a plateau, which is more and more pronounced, rather for low saltconcentrations. the existence of such a regime is in perfect agreement with the theoretical formula (25). the subdiffusive character of the random walker is also shown in figure 9 that represents vacfs versus the reduced time, 𝑡/𝜏 , for many values of the salt-concentration. these curves are underdamped (oscillatory), for low saltconcentrations, and overdamped (non-oscillatory), for high salt-concentrations, before they reach a negative region of vacfs that becomes more and more pronounced, as the saltconcentration is decreased. the existence of underdamped and overdamped behaviors is conform with the theoretical formulae (19) and (20). thus, the cage effect is more important, decreases with increasing salt-concentration (mutual interactions between charged oil-droplets are drastically diminished). also, the curves show that vacfs tails approach asymptotically zero, from negative values. this indicates that the oil-droplets experience a subdiffusion. -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 c s =0.470  c s =0.595  c s =0.735  c s =1.058  c s =1.440  c s =1.881  c s =2.381  lo g ( m e a n s q u a re d is p la c e m e n t) log (time) figure 6: msd versus the dimensionless time, 𝒕/𝝉 , in log-log scale, for various values of the salt concentration 0 2 4 6 8 10 12 14 -10 -5 0 5 10 15 20 v e lo c it y a u to c o rr e la ti o n f u n c ti o n time c s =0.470  c s =0.595  c s =0.735  c s =1.058  c s =1.440  c s =1.881  c s =2.381  figure 7: vacf versus the dimensionless time, 𝒕/𝝉, for various values of the salt concentration conclusion in this work, we focus on a dynamic problem that is related to the so-called pickering emulsions. we are interested in how the stabilization process is accomplished in time. during this process, the clothed oil-droplets execute a diffusion motion we are interested in. contrary to the diffusion in homogeneous media, we find that, using md simulations, the oil-droplets experience rather a slow motion, due to the complex structure of the pickering emulsions. the origin of this anomalous diffusion, observed in many areas of science, is the existence of cages, made of nearest neighbors (traps) surrounding the random walker (target). to valid our md simulation data, we proposed a memory diffusion theory that is based essentially on a generalized langevin equation. we found that the results from md simulations agree well with the predictions 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(see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com rev a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 article type: review article fret-based supramolecular architectures for temperature sensing and cancer diagnosis a. sohail* (1), s. hisaindee (1), i. shah (1), a.a. menhali (2) f. rasool (1) (1) chemistry department, college of science, united arab emirates university, p.o. box 15551, al-ain, united arab emirates. (2) biology department, college of science, united arab emirates university, p.o. box 15551, al-ain, united arab emirates. corresponding author : 201770097@uaeu.ac.ae received: 17 october 2021 / received in final form: 15 february 2021 / accepted: 24 february 2021 abstract : supramolecular nanostructured materials, displaying förster resonance energy transfers (fret) signals, have become the focus of interest for many researchers across the globe. fret-based supramolecular systems have extended applications in areas as diverse as materials science, biochemistry, analytical chemistry, and nanomedicine. the non-covalent phenomena operating in supramolecular frameworks depends on many factors such as wide range of time scales, binding strengths, distances, and concentrations of the supramolecular components (host and guest). herein, we focus in which fret has been used to study non covalent interactions having a key role of cancer diagnosis and temperature sensing in supramolecular systems. furthermore, we have discussed fret-based architectures with current the advancements in the field and provide a perspective on new progress for the future. keywords : supramolecular architechtures, non-covalent interaction, host-guest chemistry, fret signals, diagnosis. cite this article: a. sohail, s. hisaindee, i. shah, a.a. menhali, f. rasool, oaj materials and devices, vol 6 #1, 0102 (2022) – doi: 10.23647/ca.md20220102 a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 i. introduction supramolecular chemistry describes chemical systems composed of a discrete number of molecules with self-organization tendency through weak and reversible non-covalent interaction. supramolecular science heavily relies on macrocycle-based host-guest chemistry.(1,2) typically, in a host-guest system, a large macrocyclic host recognizes a small guest molecule, binds to each other through non covalent interactions (hydrophobic forces, electrostatic interactions, hydrogen bonding, van der waals forces) in a controlled manner.(3) this binding of host and guest molecules leads to the formation of host-guest complex.(1,3,4) more importantly, the guest molecules should fit in the cavity of host molecules, emphasizing on selective and spontaneous binding of host and guest, and thus realizing the molecular recognition.(5–7) host−guest molecular recognition has brought revolutions in the development of more sophisticated supramolecular systems or materials because of their good selectivity and stimuli responsiveness. taking advantage of weaker non-covalent host-guest interactions, the host-guest complexes are more suitable for reversibility and responsiveness towards various factors in the confined surrounding environment such as ph, light radiation, temperature, competitive factors, chemical signals, and biological interfering, etc.(3,4,6–8) the stimuli-responsive property of host-guest systems provide a favorable platform for the developing of new advanced artificial molecular machines and nanoscale smart materials.(9–11) in the past decades, many fret-based supramolecular system has been reported with extended applications such as optical sensor, photo-switches, artificial light harvesting system etc.(12–15). fret got the attention of many researchers since the concept was first disclosed by theodor förster with a remarkable discovery of green fluorescent proteins (gfps).(16) fret-based approaches are considered applicable in the diagnosis of cancer, temperature sensing due to its high sensitivity, versatility and non-invasiveness.(17–19) förster provided the basis of quantitative description for the non-radiative energy transfer between the donor and acceptor molecules. practically, in a fret phenomena, a donor fluorophore after absorption of light energy is excited to high energy state which in turn release the absorbed energy as emission of light, transfers its energy non-radiatively to the nearby acceptor fluorophore.(20) moreover, the excitation energy of the donor’s electron is transferred to that of the acceptor’s via an induced-dipole movement interaction.(21) fret is a more powerful tool than simple fluorescence because it is very sensitive to small changes in the ambient environment. there are many conditions that need to be met for the occurrence of fret phenomena. firstly, to ensure the occurrence of fret, the process require an efficient spectral overlap of donor emission with acceptor fluorophore absorption considering molecular electronic excitation and energy release.(1,22,23) secondly, the donor and acceptor fluorophores should be at favorable distance and needs to be less than approximately 10 nm.(24) the third and final criteria for the efficient energy transfer is the proper orientation of both the fluorophores to each other. once all the conditions are satisfied, the fret efficiency(25) and thus relying on the number of photons absorbed by donor fluorophores that has a key role in contribution of fret and can provide highly sensitive, temporally specific information on molecular distance and orientation. these features broaden the scope of fret and are well suited to study a wide-range of supramolecular phenomena with extended application in many fields. moreover, fret depends strongly on the distance between the donor and acceptor as given by equation (1). a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 (1) where energy transfer efficiency is represented by e and r stands for the donor-acceptor distance. r 0 is the förster radius and varies with the size of donor-acceptor pairs and depends on the spectral overlap. in general, three types of fluorescent activities have been noted in a fret phenomenon, namely, the turn-off effect on the donor, the switch-on fluorescence of the acceptor and, sometimes the acceptor quench the emission of donor and acceptor. surprisingly, the functioning of fret inside the host-guest system facilitates donor-acceptor pair association and dissociation with flexibility and controllability due to the stimuli-responsiveness and selectivity exhibited by host-guest non-covalent interactions. the combination of fret with host guest science possesses more advanced applications in many fields such as real-time in vivo monitoring of biomolecules, and structural manipulation,(26,27) cell imaging and drug delivery,(28,29) chemical and biological sensing(30–33) and photosynthesis mimicking.(18,34–36) herein, we particularly focus on fret operating supramolecular systems used for the diagnosis of cancer, and temperature sensing. to ensure the current developments in the field, an up-to-date literature study was carried for signifying our understanding of cellular processes and help in advanced approaches applied in synthetic supramolecular systems and their in vivo applications. 2. applications of supramolecular fret system based on host-guest chemistry 2.1. temperature sensing recently, amir et al. reported the preparation of a bioactive, supramolecular carbohydrate polymer. the latter was formed by grafting cucurbit[7]uril macrocycle (cb7)-encapsulated dequalinium chloride hydrate (dch) onto alginic acid carbohydrates (alg) via amide linkage formation. the supramolecular assembly was shown to have the capability of light energy transfer which can be controlled by varying polymer temperature without changing the polymer.(4) to validate energy transfer, dchalg and dch/cb7alg polymer was titrated with ans. no fret signals were observed as no significant decrease in the excited lifetime was recorded while titrating dchalg with ans as shown in figure 2a and 2c. to confirm fret signals occurrence in dch/cb7alg upon titration with ans, a substantial decrease in the excited state was recorded and thus showing the fret signals between dch/cb7alg and ans as depicted in figure 2b and 2d. prior to any emission signal measurements, energy transfer was induced by introducing 0.5 µm ans at 298 k to guarantee the integrity of the examination. following that, the temperature was reduced to 278 k, increased to 378 k, and then returned to 278 k. after ans addition, the process was repeated three times with an ans concentration rise of 2.75 µm every cycle (up to 8.75 μm). the technique shown in figure 3 was used to obtain the emission data. a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 figure 1:schematic representation of supramolecular carbohydrates polymer synthesis and modulation of fret signals by altering temperature.(4) fret signals were generated using dch (donor) and 2-anilinonaphthalene-6-sulfonic acid (ans, acceptor). the modified carbohydrate platform's stationary and time-resolved photoluminescence spectra indicated that fret resulted in a color change from violet (387 nm) to blue (429 nm), which could be switched on and off to temperature stimuli at 298-368 k. dch alginate polymer was prepared by covalent linkage of dch to alginic acid (via amide linkage) with/without cb7. in the first step, alginic acid was activated in dmso with the coupling reagent n, n′-dicyclohexylcarbodiimide (dcc), and 4-dimethylaminopyridine (dmap) as catalyst for 24 hours under constant nitrogen purging (as depicted in figure 1). figure 2: at various concentrations, energy transfer from (a) dchalg (1.5 mg l-1 aqueous suspension) and (b) dch/cb7alg (2.75 mg ml-1 aqueous suspension) to ans. corresponding 320 nm emission decays indicated by the estimated average excited-state lifetime in the absence and presence of cb7 (c) and (d). a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 figure 3: schematic representation of fret signal regeneration in aqueous suspensions and fret signal on/off switching between 298 and 368 k in 20 k increments was monitored by the rise in the unquenched/quenched lifespan ratio following temperature reduction (fret on) and increase in temperature (fret off) the results in figure 3 demonstrate the reversible response of dch/cb7alg to a temperature change from 278 to 378 k after adding an incremental quantity of ans (7 m, from 8.75 to 33.3 m) four times to create five sensing cycles. the results validated the novel supramolecular polymers' response to temperature stimuli at 298-368 k in aqueous environments. it should be emphasized that in figure 3, the unquenched/quenched lifespan ratio (τo/τ) was determined in each cycle by simply changing the temperature from 298 to 368 k. furthermore, the excitedstate lifetime was assessed rather than the steady-state spectrum since the former was more suitable for validating fret signal modulation in response to a thermal change. furthermore, the physiological activity and toxicity of the proposed supramolecular polymers should be assessed, in view of their application to a wide range of biomedical uses in the future. 2.2. cancer diagnosis wang and colleagues demonstrated that supramolecular fluorescent nanoparticles can be used for fret detection of hydrogen peroxide (h2o2) in cancer cells.(37) supramolecular fluorescent nanoparticles selfassembled from fluorescein isothiocyanate modified β-cyclodextrin (fitc-β cd)/rhodamine b modified ferrocene (fc-rb) amphiphile were employed for h2o2 detection in cancer cells as depicted in figure 4. the self-assembled nanoparticles based on numerous non-covalent contacts in an aqueous medium demonstrated great sensitivity to h2o2 while being stable under physiological conditions. the addition of h2o2 resulted in a noticeable fluorescence shift of nanoparticles from red (rb) to green (fitc) in fluorescent tests due to the fluorescence resonance energy transfer (fret) phenomenon. furthermore, in vitro results clearly indicate that fluorescent nanoparticles may be effectively absorbed by cancer cells through endocytosis and then destroyed by endogenous h2o2, accompanied by fret from “on” to “off.”. a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 figure 4: the amphiphile fitc-b-cd/fc-rb and its h2o2-activated behavior(37) these supramolecular fluorescent nanoparticles, which were created through a series of non-covalent interactions, are likely to have applications in the diagnosis and imaging of illnesses induced by oxidative stress, in which there is a cellular accumulation of reactive oxygen species such as hydroxyl radicals. for many years, nanocarriers have been particularly designed for the transport and controlled release of drugs and biological molecules. however, cargo loading and release of frequently utilized carriers are difficult to monitor, particularly in vivo. huang and colleagues described in their study, a [2]rotaxane complexation with pillar[5]arene (p5) to achieve mitochondria imaging and drug delivery materials.(28) in this work, aggregation-induced emission (aie) and aggregation-caused quenching (acq) were introduced in a host-guest controlled fret investigation. a [2]rotaxane with increased fluorescence was produced by attaching a tetraphenylethylene (tpe) unit, a typical aie-active luminophore, as a stopper on one end of the axle with pillar[5]arene acting as the wheel. the anti cancer medication doxorubicin (dox), as well as the acq agent, were covalently attached to the wheel through imine bridges and therefore positioned near to tpe, resulting in a significant failure of the fluorescence emission owing to the acq effect, which happened during fret from tpe to dox. because of the additional negative membrane potential of mitochondria, it may be identified by the [2]rotaxane via electrostatic interactions and lighted up as a result of the recognition. based on the above foundation, they started to create fret-capable snps for dox delivery that were constructed using pillar[5]arene-based amphiphilic supramolecular brush copolymers (sbps) (29) tpe and 4,4′-bipyridinium derivative (m) moieties were alternately implanted onto the polymer. the host-guest interactions formed between the m entities and peg-biotin (targeting group), as illustrated in figure 5a, functionalized p5. as a result, sbps were produced and then self-assembled into snps, which displayed an aie effect caused by the aggregation of tpe units in the particles' center. the system's emission decreased when dox was encapsulated in the snps because of fret from tpe to dox and the acq of the dox units, resulting in dual-fluorescence quenching. when the guest m was reduced by the intracellular reductase nad(p)h in an acidic environment from a bicationic entity to its radical cationic state, the binding between them and p5 was severely weakened, with the association constant dwindling by two orders of magnitude, resulting in the detachment of the host-guest pair and the dis-association of the snps. a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 1, 0102 (2022) -doi: 10.23647/ ca.md20220102 dox was therefore liberated from the confinement of the particles, and led to the restoration of fluorescence as well. figure 5b–e demonstrates the controlled drug releasing characteristics, distributions in normal tissues, and cancer cell inhibition efficiency, indicating the good encapsulation and cancer targeting capabilities (dox concentration was higher in tumor treated with dox-loaded snps than with dox alone in contrast to that in other organs). in this work, the proximity/separation of the fret pair was regulated in a very circuitous, but subtle, way by modulating the assembly of sbps and fret at the same time, producing an exquisite collaboration between stimuli-responsiveness of host-guest chemistry and fluorescence signaling of fret. figure 5: (a) procedure for the creation and disassembly of snps with dox loading and dual fluorescence quenching; (b–e) graphical depiction of the drug-delivering snps' in vivo effects: (b) blood circulation time of dox.hcl and dox-loaded snps as measured by dox plasma concentration after injection; (d) tumor growth inhibition curves on the hela tumor model treated with phosphate buffered saline (pbs), dox.hcl, and dox loaded snps, in that order. (e) the average weight of tumors in mice carrying hela tumors following the three different treatments indicated above [29]. 2016. copyright. the royal society of chemistry has granted permission for this reprint 3. conclusion and future perspectives the innovative collaboration between fret effects and host-guest chemistry has brought significant changes in the fabrication of a wide range of smart fluorescent materials with stimuli-responsive properties. however, in this emerging field, there are still many challenges for researchers to overcome in order to play better light tricks. these supramolecular fluorescent nanoparticles, which were created through a non-covalent interaction, are likely to have applications in the diagnosis of cancer disease and temperature sensing. moreover, the amazing evolution of dynamically constructed fret systems backed by supramolecular macrocyclic chemistry has resulted in the creation of a wide range of smart fluorescent materials with extended applications. furthermore, it is believed that more advanced supramolecular frameworks will have numerous biomedical applications in the future. a. sohail et al, fret-based supramolecular architectures for temperature sensing and cancer diagnosis oaj materials and devices, vol.6 # 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(2) lcpm, assane seck university, senegal corresponding author: dieng.babacar@ugb.edu.sn received: 14 september 2018 / received in final form: 14 february 2019 / accepted: 16 february 2019 abstract: in this work, recent advances in various silicon nanostructures used in crystalline silicon solar cells for antireflection and light trapping are reviewed. simulations and optimizations are also performed for the most relevant of these nanostructures. the results showed that nanocones and nanoparaboloids outperform nanopillars and give almost the same antireflective performance, reducing the average reflectance of the crystalline silicon surface below 2% in the wavelength range 300-1100 nm and under normal incidence. this reflectance is also found to stay below 4% for angles of incidence lower than 60° and for the averaged s and p light polarization. as a result, short-circuit current densities of 41.62 and 41.96 ma/cm², can be expected for a silicon solar cell decorated with these two nanostructures, respectively. finally, we described the formation of silicon nanocones via nanowires by metal assisted chemical etching. keywords: silicon, nanostructures, antireflection, light trapping, chemical etching cite this article: authors, oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 mailto:dieng.babacar@ugb.edu.sn b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p2 i. introduction today’s state-of-the-art r&d best monocrystalline (multicrystalline) silicon solar cell and module can deliver power conversion efficiencies (pce) of about 26.7% (21.9%) and 24.4% (19.9%), respectively [1]. the increased production volumes and the associated maturity of the crystalline silicon-based technology have brought the cost of silicon pv modules down to 0.4 us$/wp [2]. however, the actual efficiency (cost) is not yet high (low) enough to guarantee a widespread adoption of solar by consumers. further efficiency enhancement and cost reduction, through optimization of device structure, simplification of device fabrication, as well as reduction of material usage, are required [3]. the nanostructuring of the silicon surface has been found to be an efficient way to eliminate the frontsurface reflection and, simultaneously, to increase the absorption in silicon solar cells [4]. optimized silicon nanostructure arrays exhibit not only excellent antireflective and light trapping properties [6–9], but also provide other pv relevant functionalities such as hydrophobicity [10, 11]. therefore, they are more and more used in solar cells for efficiency enhancement [5] and cost reduction [3]. in this work, recent advances in various silicon nanostructures used for antireflection and light trapping in crystalline silicon solar cells, such as nanopyramids, nanopillars, nanocones and nanoparaboloids, are first reviewed. then, the most relevant of these nanostructures are simulated and optimized for performance enhancement. finally, the formation of silicon nanocones by metalassisted chemical etching (mace) is described. ii. recent advances in silicon nanostructures used for antireflection and light trapping ii.1. silicon nanopyramids pyramids have long been the dominant structure at the front surface of monocrystalline-silicon solar cells. pyramidal silicon microstructures (~10 μm thickness) provide a relatively low surface area and a good light trapping capability, achieved through multiple reflection of the incident light in the various facets of the pyramidal structure [12, 13]. this results in average reflectance values of less than 10% in the spectral range 300 – 1100 nm and an appreciable increase in the solar cell pce. also, inverted pyramids have been found to outperform upright pyramids due to the fact that most of the incident rays bounce several times (at least three) on the walls of the inverted pyramids but only twice between conventional random upright pyramids. therefore, the length of the optical path and the probability of light absorption are higher in the inverted pyramid structure [12, 14–16]. in addition to superior light trapping capability, the inverted pyramid structure is characterized by recessed and wide deeps, making this texture more suitable for conformal coating and filling. the coverage of passivation layers (for example hydrogenated amorphous silicon (a-si:h) [17, 18] and silicon nitride (sinx) layers [13]) or thin film solar cells (for example a thin film perovskite solar cell [19]) and the filling of metal electrodes in photovoltaic devices [13] demonstrated the compatibility of inverted pyramids with subsequent process steps in the manufacture of solar cells. recently, with the trend toward ultrathin crystalline silicon cells, pyramidal microstructures commonly applied on thick crystalline silicon cells become unsuitable and the implementation of nanopyramids is proving to be more effective [13, 20–24]. metal (e.g. au, ag, cu)-assisted chemical etching [13, 16] or combination of lithography and wet chemical etching are principally used to fabricate inverted nanopyramids on silicon wafers [17, 20, 22, 24]. the different techniques used, the optimized structural parameters found and the performance obtained are summarized in table 1. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p3 table 1: techniques, parameters and performance of inverted nanopyramid structure on a silicon wafer. techniques parameters performance laser interference lithography and wet chemical etching [20]. period = 700 nm spacing = 100 nm 37.5 ma/cm2of jsc for 10 μm-thick c-si (over 30-fold reduction in material usage) laser interference lithography and subsequent combined dry and wet etching [22] period = 700 nm spacing = 100 nm depth = 475 nm r below 10% over the broad λ range 300 – 1200 nm increase in efficiency by 67% colloidal lithography and anisotropic wet etching [23] period = 1400 nm increase in jsc by 76% for 20-μm-thick csi (39.86 ma/cm2 vs 22.63 ma/cm2 for the flat counterpart) laser interference lithography and reactive ion etching (rie) and wet etching [24] width ~ 450 nm height ~ 310 nm spacing ~ 125 nm increase in jsc by 11.45% (from 29.422 to 32.793 ma/cm2) cu-assisted anisotropic etching [13] random inverted pyramids mean r down to ~4.4% over the λ range 300 – 1000 nm; a high conversion efficiency of 18.87% colloidal lithography [18] diameter ∼600 nm depth ∼530 nm aspect ratio (length by diameter) 0.9–1 increase in the light path by 7.5 times; efficiency of 8.6% on 830 nm-thick monocrystalline silicon jsc = short-circuit current density; r = reflectance; λ= wavelength. the advantages of excellent antireflection and light-trapping capabilities, an inherent low parasitic surface area, a negligible surface damage (less material damage), a scalable fabrication capability and good compatibility with subsequent process steps, make inverted nanopyramids a promising alternative for high-performance and cost-effective crystalline silicon thin film cells [23]. ii.2. silicon nanopillars silicon nanopillar arrays with different pillar profiles have been found to exhibit excellent broadband, omnidirectional antireflective, and hydrophobicity properties due partly to the graded effective refractive index profile provided by the structure. their great potential in improving the pce and lowering the cost of crystalline silicon solar cells has been theoretically and experimentally demonstrated [7–9, 25–35]. furthermore, it has been shown that the shape, height and period of silicon nanopillar arrays have a great influence on their antireflective properties [8, 28–30, 34]. sharper pillars would lead to sharper minimum in the reflectance spectrum and so to a surface that is less suitable for broadband applications [8]. in fact, a close relation exists between the nanopillar shape and the refractive index gradient. nanopillars with a tapered profile produce a smooth transition of the refractive index from the top to the bottom of the structure, whereas nanopillars with a cylindrical profile produce a larger discontinuity at the interface which causes more reflection [34]. also, it was observed that the taller the pillars, the lower the reflectance, but the higher the fabrication cost. this is because at small pillar height, the reflectance is high as the interface appears abrupt to incident light [8]. as for the period, it was shown that close-packed nanopillar arrays exhibit better antireflective performance than non-close-packed arrays due to a smoother refractive index gradient [30]. however, for single-diameter nanopillars, that are similar to nanowires, it was found that increasing the material filling ratio leads simultaneously to an increase of the reflectance and a decrease in the transmittance, with the absorption showing a strong diameter dependence [36]. the light absorption of nanopillar arrays is either determined by the material filling ratio or by transverse resonance leaky modes depending on the input wavelength. a properly designed multi-diameter b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p4 nanopillar array was found to compete with a nanocone array on broadband light absorption capability, showing the same light absorption level when the number of the segment n=7 [37]. various techniques are used to fabricate silicon nanopillars such as the combination of reactive-ion etching (rie) with processes as self-assembly [25], spin coating [26], nanoimprint lithography [27], colloidal lithography [28], electron beam lithography [35], and inductively coupled plasma reactive-ion etching (icp-rie). the different techniques used, the optimized structural parameters found and the performance obtained are summarized in table 2. table 2: techniques, parameters and performance of nanopillar structures on a silicon wafer. techniques [references] parameters performance self-assembly of polystyrene sphere and rie [25] height = 260 nm aspect ratio = 0.9 r < 8% for 600 ≤ λ ≤ 1300 nm spin-coating and rie [26] height = 2200 nm period = 380 nm r < 2.5% for 350 ≤ λ ≤ 1650 nm nanoimprint lithography (nil) and deep rie (drie) [27] diameter < 40 nm height = 1.5 μm wide-area fabrication of high aspect ratio silicon pillar arrays with straight sidewalls colloidal lithography (or anodic aluminum oxide) and metal-assisted chemical etching [28] period = 100 nm diameter = 60 nm average specular r of 0.7% for 200 ≤ λ ≤ 1900 nm and for θ up to 70° (sand p-polarized light) cryogenic inductively coupled plasma reactive-ion etching [25]. height ∼ 800 nm width = 200 nm bottom diameter ∼200 nm 20 nm of al2o3 film (passivation) r < 1% for 300 ≤ λ ≤ 1 000 nm; efficiency of 22.1%; potential increase of 3% in daily energy production electron beam lithography and rie [35] width = 140 nm thickness = 110 nm spacing = 100 nm average r < 5% in the visible spectrum for both polarizations for 0° ≤ θ ≤ 40° jsc = short-circuit current density; r = reflectance; λ = wavelength; θ = incident angle. strongly reduced reflection and enhanced light trapping can be achieved in thin (<100 μm) crystalline silicon solar cells covered with nanopillar arrays on top of interference coatings. optimized si nanocylinders (diameter = 250 nm, height = 150 nm and pitch = 450 nm) on a standard si3n4 coating (thickness = 60 nm) resulted in an average reflectance of 1.3% in the 450 – 900 nm spectral range and for angles of incidence up to 60°. this reduced reflection resulted from the coupling of mie modes to the substrate, leading to strong preferential forward scattering due to the high-mode density in the high-index si substrate [32]. it was shown that an efficiency as high as 21.5% can be achieved for a 20-μm-thick cell using this combination. this represent a significant improvement compared with the efficiency found for planar c-si cell with a standard si3n4 antireflection coating of the same thickness (17.5%) [38]. ii.3. silicon nanocones compared with many other structures, nanocones are considered as the more optimal ones for antireflection and light trapping due to their relatively small tips that provide a smoother transition of their refractive index from air to the substrate [39–47]. investigations of the effects of structural parameters on the optical characteristics of crystalline si thin films with the surface decorated by si nanocone arrays showed that the base diameter should be equal to the array periodicity for efficient solar energy harvesting, and an optimized light absorption can be realized when the nanocone height b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p5 reaches ∼400 nm. it was also shown that an ultimate efficiency of ∼31.5% can be achieved when the periodicity is ∼600 nm for a 800 nm-thick si film with a 400 nm-high nanocone array. moreover, this ultimate efficiency can be further increased to some extent due to the enhanced light absorption in the low energy region by appropriately increasing the si film thickness [48]. nanocone arrays (dtop = 200 nm, dbot = 600 nm, period = 600 nm, height 50 – 10 000 nm) were found to have significantly improved solar absorption and ultimate efficiency (about 22% higher) over nanowire arrays. detailed simulations revealed that nanocones have superior absorption due to reduced reflection from their smaller tip and reduced transmission from their larger base. the enhanced ultimate efficiency of silicon nanocone arrays was found to be insensitive to tip diameter [49]. it was found that when the aspect ratio of the nanocones is less than two, both excellent antireflection and light scattering are obtained. the light trapping effect that increases the optical path length becomes more prominent, especially when the substrate becomes thinner [50]. like silicon nanopillars, silicon nanocones can also be fabricated by various techniques. the different techniques used, the optimized structural parameters found and the performance obtained are summarized in table 3. table 3: techniques, parameters and performance of nanocone structures on silicon wafer. techniques parameters performance nanosphere lithography and rie [39] corrugated si nanocones height ~ 590 nm diameters: bottom ~ 560 nm; top (tip) ~ 80 nm; aspect ratio ~ 1.0 r < 0.7% for 400 ≤ λ ≤ 1050 nm. r < 0.5% for θ up to 70° at 632.8 nm for both sand ppolarized light. colloidal nanosphere lithography and single-step deep rie [40] polystyrene nanoislands: thickness 50 – 100 nm si nano-conical frustum: dbase ~ 200 nm; dtop = 190 nm; height = 320 nm; lattice constant=360 nm average r of 3.8% for 300 ≤ λ ≤ 400 nm (vs 9.2% for sharptipped nanocone structures) e-beam lithography and drie [51] inverted nanocones: radius ~50 nm; lattice constant 300 – 400 nm three to four-fold reduction in reflection langmuir−blodgett assembly and rie [51] double-sided grating: top: period=500 nm; base radius = 250 nm; height = 710 nm bottom: period = 1000 nm; base radius=475 nm; height=330 nm jsc of 34.6 ma/cm2 at an equivalent thickness of 2 μm colloidal lithography (langmuir–blodgett method) and rie [43] diameter = 200 nm eqe > 80% for 400 ≤ λ ≤ 800 nm in a sub-10-μm-thick; pce = 13.7% two-step dry etching process (rie and drie [46] low r ~ 0.5% for 300 ≤ λ ≤ 1500 nm inductively coupled plasmareactive ion etching (icp-rie) [47] height = 230 nm spacing = 52 nm average r < 1% at θ = 45° for 400 ≤ λ ≤ 1000 nm average r < 4% for θ < 60°; improvement of the jsc (from 22 to 33 ma/cm2) and the pce (from 8.7 to 13.1%) by 50% jsc = short-circuit current density; r = reflectance; λ = wavelength; θ = incident angle; eqe= external quantum efficiency; pce = power conversion efficiency. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p6 ii.4. silicon nanoparaboloids paraboloid-shaped nanostructures have been found to be superior to pillar-shaped and cone-shape nanostructures, minimizing the reflectivity for a much broader spectral range, due to a linear change of the effective refractive index from air to the substrate [53]. k. shinotsuka et al. numerically simulated both convex and concave paraboloids and found that the surface reflectivity is drastically decreased when a step is introduced in the taper. the optimization of the step position (at 100 nm height for convex and 150 nm height for concave) and depth (7 nm for convex and 6 nm for concave) provided average reflectances of 0.098% (0.1939 % without step) for convex protrusions and 0.040% (0.2021% without step) for concave protrusions, respectively, in the visible range (380 – 780 nm) at various incident angles. a stepped concave paraboloid, fabricated on the whole surface of a 6 in. si wafer (sufficient size for industrial utilization) by dry etching exhibited a measured reflectance of 0.077% on average in the visible range [54]. this mini-review shows that the design and optimization of silicon nanostructures with different shapes produce different results, mainly expressed in terms of reflection minimization and short-circuit current maximization. the next section deals with the simulation and optimization of the most relevant silicon nanostructures for solar cells. iii. simulation and optimization of silicon nanostructures in this work, the transfer matrix method [55] is used to calculate the front reflectance from a nanostructured silicon surface. the optical constants needed for this calculation are taken from [56] for crystalline silicon. the structures under consideration are shown in figure 1. they consist of arrays of periodic pillars (a), cones (b), truncated cones (c), and parabolas (d) designed on crystalline silicon substrate. for each structure, the geometrical parameters to optimize are principally the diameter, the height and the period. figure 1: schematic representations of nanostructures: (a) pillars, (b) cones, (c) truncated cones, and (d) parabolas. to model the structures, each of them is considered as forming a composite layer consisting of silicon and air (the refractive of air index is taken nair ≈ 1) with a thickness equal to the height of the silicon nanostructure. therefore, the effective refractive of the layer index is calculated in the framework of the effective medium approximation. finally, the complex reflection coefficient, r, of the layer is calculated from the elements of the transfer matrix and the reflectance, r, is obtained as │r│2. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p7 to evaluate the performance of these ar structures, the weighted reflectance of the solar radiation (rw) and the short-circuit current density (jsc) that can be expected, are calculated using the following equations:    max min max min )()().( )()().().(       diqef driqef rw (1) )()().().( max min    daiqefqj sc  (2) in these equations ch i f . ).( )(    is the incident photon flux where i() represents the solar radiation; iqe() is the internal quantum efficiency of the solar cells, r() refers to the reflectance given by the ar structure, a() is the absorption in the silicon active layer, q and  are the elementary charge and the incident wavelength, respectively. the main objective of the optimization is to reduce the weighted reflectance (rw) and to maximize the short circuit current density over the widest wavelength range, incident angles and for the two types (s and p) of light polarization. figures 2.a and 2.b show the variations of the average reflectance and the short-circuit current density, respectively, as function of the base diameter of the pillar, truncated cone and cone-shaped structures. as can be seen, low reflectance values and high short-circuit current densities are obtained with a base diameter around 100 nm. figure 2: (a) average reflectance and (b) short-circuit current density as a function of the structure base diameter. for the parabola-shaped structure, the semi-major and semi-minor axis are two important parameters. the influence of these two parameters on the reflectance is depicted in figure 3. as can be seen, the optimal values for the semi-major and the semi-minor axis are around 35 nm and 25 nm, respectively. it is known that very small and very large structures give a dense an airy structure, respectively. thus, short and long wavelengths will not be well trapped. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p8 10 20 30 40 50 60 70 80 90 100 2 4 6 8 10 12 14 16 18 ellipse parameters of parabola (nm) a v e ra g e r e fl e c ta n c e ( % ) semi-major axis semi-minor axis figure 3: average reflectance as a function of the ellipse parameters of the parabola-shaped structure. the period of the nanostructures plays an important role in the reduction of the reflectance. practically, the period of the nanostructures can be determined by adjusting the diameter of the nanomask used during the fabrication. therefore, it is necessary to optimize the period before the fabrication step. figures 4.a and 4.b show the variation of the average reflectance and the shortcircuit current density, respectively, as function of the period. as can be seen, the optimal periods of the pillar, truncated cone, cone and parabola-shaped structures are around 750 nm, 500 nm, 400 nm and 350 nm, respectively. as could be expected, the optimal period depends on the structure shape. a small period is adequate for nanocone and nanoparabloid shapes because their peaks are sharp. with these optimal periods, the ar structures act as an effective medium for the longer wavelengths, as a photonic crystal for wavelengths comparable to the period and as a grating diffraction for the smaller wavelengths. figure 4: (a) average reflectance and (b) short-circuit current density as a function of the period of nanostructures. the height is another important parameters for antireflective nanostructures. figure 5 shows that by increasing the height of the nanostructures, the reflectance decreases abruptly at first, then increase slightly and decrease at last. in fact, the long structures make it possible to obtain multiple rebounds of the incident light inside the antireflective structure and therefore to increase the probability of light b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p9 transmission. since the height of nanostructures increase with the etching time, long nanostructures lead to a high production cost. therefore, a trade-off is to be found between the more performing long nanostructures and the high production cost. figure 5: average reflectance as a function of the height of the nanostructures. figure 6.a compares the reflectance of the four types of antireflective structures optimized in this study. the performance of a quarter-wavelength sinx layer is also shown as reference. it can be seen that the antireflective structures perform better than the planar sinx over the wavelength range 3001100nm. particularly, the conical and parabolic shapes give the best antireflective performance. this might be due to a better graded refractive index (grin). indeed, a best grin is obtained when the volume fraction (f) is nearly one at the bottom of the nanostructures and zero at the top of them. figure 6: (a) reflectance as function of the wavelength for the ar nanostructures and a sinx layer used as reference; (b) dependence of the reflection on the incident angles. the performances of the ar structures studied in this work are summarized in table 3. these performances are obtained under normal incidence and in the wavelength range 300-1100 nm. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p10 table 4: summary of the performance of the antireflective structures ar structures rw [%] jsc [ma/cm²] pillars 3.0792 41.1799 cones 2.7507 41.3114 truncated cones 2.0067 41.6274 parabolas 1.2222 41.9607 the effect of incident angle on the antireflective performances given by these ar structures is also considered. figure 6.b shows that the reflectance is only sensitive to angles greater than 60°. the conical and parabolic shape give the best antireflective performances. but, in practice, a conical nanostructure is easier to fabricate than a parabolic one. as their antireflective performances are almost the same, the conical nanostructure can be considered as the optimal shape. the fabrication of this structure is described in the next section. iv. fabrication of silicon nanocones by mace method dry etching with nanoscale mask patterns is the commonly used method to fabricate subwavelengthscale silicon nanostructures [57]. however, this method is complex, expensive, and unsuitable for mass production. metal assisted chemical etching (mace), based on the strong catalytic activity of metal in an aqueous solution, is an alternative to produce silicon nanostructures for electronic and optoelectronic devices. it is a simple, fast, cost-effective, and high throughput method for fabricating various silicon nanostructures without any sophisticated equipment. in this work, silicon nanocones (sncs) were fabricated via silicon nanowires (snws). silicon samples were first cleaned using acetone, ethanol and deionized water in the ultrasonic bath during 15 minutes. after this cleaning, the samples were immersed in a piranha solution (h2so4/h2o2) during 10 minutes to eliminate any organic trace. the last steps of the cleaning process were the removing of the native oxide (sio2) using diluted hf solution and the rinse of the samples with deionized water. after cleaning, the samples were immersed in the hf/agno3 (4.8m/0.02m) solution during 5 minutes. this solution allows to deposit ag nanoparticles on the silicon surface. then, the samples were directly immersed in hf/h2o2 (4.8m/1.176.10-3m) mixture. in order to remove the ag waste, a diluted hno3 solution was used. finally, vertical snws were obtained on the crystalline silicon substrate. a sem image of the sample is shown in figure 7. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p11 figure 7: sem image of silicon nanowires fabricated by mace method on a c-si substrate. once the snws were obtained, they were treated with a mixture of hf/agno3/h2o2 in order to fabricate sncs. indeed, this mixture has a dual function: it leads to the selective deposition of ag clusters at the snw tips and at the same time performs the etching of the silicon surface. the ag cluster deposition and removal processes were then repeated several times under well-controlled chemical conditions in order to yield silicon nanowires with different morphology, focusing on the ultimate goal to produce silicon nanocones. finally, a hno3 solution was used to remove the residual silver. reflectance spectra from the fabricated silicon nanocones were measured using a uv-vis-nir spectrophotometer and the results were compared with the calculated one. it can be seen in figure 8 that the experimental results confirm the theoretical ones. however, the measured reflectance is slightly higher than the calculated one because a metallic grid was deposited on the sncs arrays as surface contact. b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p12 figure 8: reflectance spectra from fabricated sncs: calculated (blue) and measured (red). iv. conclusion we have reviewed recent advances in various silicon nanostructures used for antireflection and light trapping in crystalline silicon solar cells, such as nanopyramids, nanopillars, nanocones, and nanoparaboloids, with particular focus on the fabrication techniques, the structural parameters and the resulting performance. using the transfer matrix method, we have simulated and optimized three silicon nanostructure shapes and found that nanocones and nanoparaboloids outperform nanopillars. they exhibit nearly the same antireflective performance, reducing the average reflectance of the crystalline silicon surface below 2% in the wavelength range 300-1100 nm and under normal incidence. our simulation and optimization results showed that with these two silicon nanostructure shapes short-circuit current densities of 41.62 and 41.96 ma/cm² can be expected, respectively. therefore, this is a confirmation of the great potential of these nanostructures to enhance the power conversion efficiency of crystalline silicon solar cells. we have fabricated a conical ar nanostructure by mace method and measured its average reflectance. we have noticed a small deviation in the average reflectance between the measured (2.96%) and the calculated one (1.98%). complementary informations on authors: babacar dieng: dieng.babacar@ugb.edu.sn, https://www.researchgate.net/profile/babacar_dieng modou beye: almodu@yahoo.fr, https://www.researchgate.net/profile/modou_beye moussa toure: m.toure5053@zig.univ.sn, https://www.researchgate.net/profile/m_toure mailto:dieng.babacar@ugb.edu.sn https://www.researchgate.net/profile/babacar_dieng mailto:almodu@yahoo.fr https://www.researchgate.net/profile/modou_beye mailto:m.toure5053@zig.univ.sn https://www.researchgate.net/profile/m_toure b. dieng, m. beye, m. toure, d. diouf , d. kobor, a. s. maiga, design and optimization of silicon nanostructures oaj materials and devices, vol 4 #1, 0129 (2019) – doi: 10.23647/ca.md20190129 p13 djicknoum diouf: djicknoum.diouf@ugb.edu.sn, https://www.researchgate.net/profile/djicknoum_diouf3 acknowledgements: b. dieng acknowledge financial support from the cea-mitic. references 1. m. a. green, y. hishikawa, w. warta, e. d. dunlop, d. h. levi, j. hohl-ebinger, a. w. y. 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(see details in the site of the journal: http://materialsanddevices.co-ac.com) we want to maintain materials and devices open access and free of charge thanks to volunteerism, the journal is managed by scientists for science! you are welcome if you desire to join the team! advertising in our pages helps us! companies selling scientific equipments and technologies are particularly relevant for ads in several places to inform about their products (in article pages as below, journal site, published volumes pages, …). corporate sponsorship is also welcome! feel free to contact us! contact@co-ac.com http://materialsanddevices.co-ac.com/ mailto:contact@co-ac.com materialsmaterials andand devicesdevices conference volumeconference volume communications presented at the first communications presented at the first transpyrenean encounter on advanced transpyrenean encounter on advanced materialsmaterials (team1 – sète, 4,5,6 july 2017)(team1 – sète, 4,5,6 july 2017) editor p. saint-grégoireeditor p. saint-grégoire published by collaborating published by collaborating academicsacademics http://co-ac.comhttp://co-ac.com materials and devices, vol.2, no2 (2017) issn 2495-3911 doi : 10.23647/ca.md20170407  an international research journalan international research journal http://materialsanddevices.co-ac.com issn 2495-3911 general informations materials and devices is a new journal devoted to all aspects of materials and related devices. it is open access and free of charges for authors. our aim was to create a high quality journal, with a strict peer-review process, and complying with the transparency rules edicted by the doaj, cope,... materials and devices publishes several types of articles : a : regular papers, that should present the results of original research, not published or submitted somewhere else. l : short papers, written as letters, focusing on one or few particular aspects, representing a very significant progress, for rapid publication. r : review papers, that presents a summary of results published in literature, on fields covered by the journal. t : technical papers, on the development of laboratory technics and aparatus relevant to studies on materials and related devices. such papers will present the details of the designed technics, and an example of application in real condition. ur : unexpected and « negative » results, the journal accepts papers describing unexpected results, or results considered as negative, provided that the original ground arguments are sound, and that a reasonable interpretation can be proposed. typical examples are : a synthesis process that is generally successful, which aborts in given cases, or give different unexpected but interesting results, results contradicting a theory or a model, etc. the idea to publish such papers is mainly to save time to the scientific community by giving information that is generally not available, except as private communications between researchers. we are happy to announce these innovations : section t (technical papers) and ur (unexpected and « negative » results are original. they correspond to needs in the scientific community. conf: conference papers : finally, materials and devices may also publish conference proceedings and conference papers in special volumes. this service is not free, organizers of conference interested should contact the journal to know details. aims and scope of the journal the topics covered by the journal are wide, it aims at publishing papers on : all aspects related to materials, namely according to their chemical formula (oxides, fluorides, carbon compounds, …, organic, inorganic), to their physical properties (conductors, super-conductors, semi-conductors, insulators, dielectrics,...), to their nature (crystalline or amorphous materials, liquid crystals, modulated systems, aperiodic materials, nanomaterials and nanostructured materials)… or environmental type (ecomaterials), or according to some specific applications. papers on biomaterials, geomaterials, archeomaterials or on studies of ancient materials are also welcome. a particular attention is also paid on environmental studies related with materials. authors are also encouraged to submit papers on theoretical studies applied to materials, including pure mathematical approaches, physical approaches, models, numerical simulations, etc. devices in a wide sense. however, concerning devices, the scope is restricted to those integrating particular materials (for instance memories based on some specific magnetic materials) or category of materials. papers on all types of such devices are welcome. oaj materials and devices i http://materialsanddevices.co-ac.com/ policy of the journal materials and devices is an open access (*) journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal has thus been worked out in such a way as complying with the requirements issued by oaspa and doaj in order to apply to these organizations. evaluation – peer-reviewing : after reception, the paper is sent to two reviewers for evaluation. in case of divergent opinions of reviewers, the editor-in-chief sends the paper to a third reviewer and then gives a final decision based on all reports. reviewers are asked to reply within three weeks to warranty a fast publication process. copyright on any article in materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. (*) an open access journal means that all content is freely available without charge to the user or his/her institution. users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. this is in accordance with the boai definition of open access. international editorial board orientation of the journal, choice of reviewers, special issues, editorial policy, etc, are discussed by the international editorial board. list of members algeria mokhtar boudissa, professor researcher, dpt ebt, enmc laboratory, faculté de technologie, université f. abbas setif-1, sétif 19000 boudi44 @ yahoo.fr brazil paulo t.c. freire, full professor, universidade federal do ceará, fortaleza tarso @ fisica.ufc.br josé de los santos guerra, professor, instituto de física, universidade federal de uberlandia (ufu), uberlandia – jsantosguerra @ gmail.com burkina faso dieudonné joseph bathiebo, full professor, university of ouagadougou – djbathiebo@gmail.com canada zuo-guang ye, professor, simon fraser university, burnaby, bc zye @ sfu.ca cuba aimé peláiz barranco, full professor, physics faculty, havana university pelaiz@fisica.uh.cu maria sánchez, full professor, faculty of physics, university of havana – maruchy @ fisica.uh.cu elena vigil, full professor, physics fac. materials sc. & tech. inst. (imre), university of la habana, and solar energy cathedra chairperson, cubasolar-u.h. evigil @ fisica.uh.cu czech republic ivan gregora, institute of physics, czech academy of science, prague gregora@fzu.cz vacláv janovec, emeritus professor, prague denmark heloisa bordallo, associate professor, niels bohr institute university of copenhagen france patrice bourson, professor, lmops université de lorraine centralesupelec 2 rue e. belin 57070 metz patrice.bourson@univ-lorraine.fr oaj materials and devices ii mailto:patrice.bourson@univ-lorraine.fr mailto:gregora@fzu.cz mailto:evigil@fisica.uh.cu mailto:maruchy@fisica.uh.cu mailto:pelaiz@fisica.uh.cu mailto:djbathiebo@gmail.com mailto:jsantosguerra@gmail.com mailto:tarso@fisica.ufc.br mailto:boudi44@yahoo.fr alain claverie, research director, cemes/cnrs toulouse, and private consultant to several companies (microelectronics, areospace) claverie@cemes.fr pierre saint-grégoire, full professor, universities of toulon and nîmes, president of collaborating academics, https://fr.linkedin.com/in/saint-gregoirepierre-5bb6372b pstgregoire@gmail.com philippe sciau, senior scientist, cemes-cnrs, 29 rue j. marvig, 31055 toulouse philippe.sciau@cemes.fr georges zissis, professor, université toulouse 3 paul sabatier; laboratoire laplace umr 5213, toulouse georges.zissis@laplace.univ-tlse.fr germany lukas m. eng, tu dresden, institute of applied physics, and also, center for advancing electronics dresden lukas.eng@tu-dresden.de india amit das, doctor, solid state physics division, bhabha atomic research centre, trombay, mumbai 400085 sm yusuf, head, magnetism section, and professor at homi bhabha national institute, solid state physics division, bhabha atomic research centre, trombay, mumbai 400085 israël gil rosenman, the henry and dinah krongold chair of microelectronics, school of electrical engineering-physical electronics, faculty of engineering, tel aviv university, ramat aviv gilr@eng.tau.ac.il italy luca rebuffi, x-ray optics and spectroscopy laboratory supervisor, elettra-sincrotrone trieste s.c.p.a., trieste luca.rebuffi@elettra.eu japan emilio j. juarez-perez, researcher, energy materials and surface sciences unit. okinawa institute of science and technology graduate university (oist) 1919-1 tancha, onna-son, okinawa, 904-0495 ej.juarezperez@oist.jp , http://ej-juarezperez.home.oist.jp/ kazakhstan koblandy turdybekov, head of the department of physics, karaganda state technical university, karaganda xray-phyto@yandex.kz mexico a. guillermo castellanos-guzmán, professor-researcher, dip cucei universidad de guadalajara, guadalajara jal. gcastel@cucea.udg.mx moldova anatolie sidorenko, director, institute of electronic engineering and nanotechnologies "d.ghitu" asm – anatoli.sidorenko@nano.asm.md, anatoli.sidorenko@kit.edu morocco abdelhai rahmani, professor, physics department, faculty of sciences, meknes rahmani614@gmail.com / a.rahmani@flsh.umi.ac.ma people republic of china yang gan, professor, department head, harbin institute of technology, harbin ygan@hit.edu.cn qinghui jiang, assoc professor, state key laboratory of material processing and die & mould technology, and school of materials science and engineering, huazhong university of science and technology, wuhan 430074 qhjiang@hust.edu.cn zhifu liu, professor, cas key lab of inorganic functional materials and devices, shanghai institute of ceramics, chinese academy of sciences liuzf@mail.sic.ac.cn xiaoyong wei, professor, electronic materials research laboratory (emrl) xi’an jiaotong university, xi’an 710049 wdy@mail.xjtu.edu.cn poland maria zapart, institute of physics, faculty of production engineering and materials technology, czestochowa university of technology zapart@wip.pcz.pl oaj materials and devices iii mailto:zapart@wip.pcz.pl mailto:wdy@mail.xjtu.edu.cn mailto:liuzf@mail.sic.ac.cn mailto:qhjiang@hust.edu.cn mailto:ygan@hit.edu.cn mailto:a.rahmani@flsh.umi.ac.ma mailto:rahmani614@gmail.com mailto:anatoli.sidorenko@kit.edu mailto:anatoli.sidorenko@nano.asm.md mailto:gcastel@cucea.udg.mx mailto:xray-phyto@yandex.kz http://ej-juarezperez.home.oist.jp/ mailto:ej.juarezperez@oist.jp mailto:luca.rebuffi@elettra.eu mailto:gilr@eng.tau.ac.il mailto:lukas.eng@tu-dresden.de mailto:georges.zissis@laplace.univ-tlse.fr mailto:philippe.sciau@cemes.fr mailto:pstgregoire@gmail.com https://fr.linkedin.com/in/saint-gregoire-pierre-5bb6372b https://fr.linkedin.com/in/saint-gregoire-pierre-5bb6372b mailto:claverie@cemes.fr russian federation boris darinskii, professor, voronezh state university, university sq.1, voronezh 394006 darinskii@mail.ru alexander sidorkin, professor, voronezh state university, university sq.1, voronezh 394006 sidorkin@phys.vsu.ru alexander sigov, professor, head of condensed matter physics chair, president of the university, moscow technological university, moscow sigov@mirea.ru mikhail smirnov, professor, physical department, st. petersburg state university smirnomb@rambler.ru alexander vtyurin, deputy director, head of raman spectroscopy group, kirensky institute of physics, krasnoyarsk vtyurin@iph.krasn.ru senegal issakha youm, professor, department of physics, fst, university cheikh anta diop de dakar, dakar-fann singapore pooi see lee, professor, nanyang technological university, singapore, pslee@ntu.edu.sg south africa malik maaza, chair, unesco unisa africa chair in nanosciences, college of graduate studies, unisa, pretoria, & nanoafnet, ithemba labs, national research foundation of south africa, faure, western cape maaza@tlabs.ac.za , maazam@unisa.ac.za spain javier piqueras, professor, universidad complutense de madrid carmen aragó, full professor, dpt. física de materiales, universidad autónoma de madrid carmen.arago@uam.es paloma fernández, full professor, department materials physics, fac. of physics, university complutense, madrid arana@fis.ucm.es togo kossi napo, professor, unesco chair on renewable energies, faculty of sciences, university of lomé silnapo@yahoo.fr ukraine yulian vysochanskii, professor, uzhgorod national university, uzhgorod vysochanskii@gmail.com united kingdom james f. scott, depts. of chemistry and physics, st. andrews university, st. andrews, fife, uk ky16 9st jfs4@standrews.ac.uk: usa michael d. hampton, professor, department of chemistry, university of central florida, orlando, fl 32816 alexei gruverman, professor of physics, university of nebraska-lincoln agruverman2@unl.edu anirudha v. sumant, ph.d., materials scientist, center for nanoscale materials, argonne national laboratory, 9700 s. cass ave., building 440, room a-127, argonne, il 60439 sumant@anl.gov , linkedin profile: http://www.linkedin.com/in/anisumant editor-in-chief : pierre saint-grégoire (france) – pstgregoire@gmail.com people interested in this project are welcome ! contact us to submit your proposals, ideas, suggestions, or to get involved in some actions ! oaj materials and devices iv http://www.linkedin.com/in/anisumant mailto:sumant@anl.gov mailto:agruverman2@unl.edu mailto:jfs4@st-andrews.ac.uk mailto:jfs4@st-andrews.ac.uk mailto:vysochanskii@gmail.com mailto:silnapo@yahoo.fr mailto:arana@fis.ucm.es mailto:carmen.arago@uam.es mailto:ac.za/maazam@unisa.ac.za mailto:maaza@tlabs.ac.za mailto:pslee@ntu.edu.sg mailto:vtyurin@iph.krasn.ru mailto:smirnomb@rambler.ru mailto:sigov@mirea.ru mailto:sidorkin@phys.vsu.ru mailto:darinskii@mail.ru materials and devices (issn 2495-3911) is a new journal, and as such, is not yet indexed. however in future we shall consider as a priority task, to reach a significant impact factor for this journal. collaborating academics ngo materials and devices is owned by the non governmental non profit organization collaborating acamics, an international ngo located in france, that works for scientific communication (organization of meetings, workshops, etc) and development of science. during the launching period authors are encouraged to join the ngo collaborating academics (admission fee 15€/year) that supports the journal, in order to help reaching financial stability. collaborating academics has launched collaborating academics – international press. caip is a collaborative project led by academics and scholars. the main idea is to appropriate the scientific edition in its open access form, and keep it free as much as possible. these structures base their activities on volunteerism and you are welcome if you are interested in joining us! to get involved : register as potential reviewer/reader/author in the site of the journal : http://materialsanddevices.co-ac.com join collaborating academics : http://co-ac.com and propose ideas ! submit papers ! submit your paper on line at http://materialsanddevices.co-ac.com contact us at : contact@co-ac.com publisher : collaborating academics french association (loi 1901) registered nr w343019101 (préfecture de l’hérault). no siret: 814 883 476 000 16 – ape 9499z address : 14, av frederic mistral, 34110 frontignan, france contact : + 33 675 64 02 29 – email : contact@co-ac.com advertising of free/open source softwares scientists need efficient, robust, reliable operating systems… use linux! oaj materials and devices v mailto:contact@co-ac.com mailto:contact@co-ac.com http://materialsanddevices.co-ac.com/ advertising of free/open source softwares libreoffice https://www.libreoffice.org/ libreoffice is a powerful office suite – its clean interface and feature-rich tools help you unleash your creativity and enhance your productivity. libreoffice includes several applications that make it the most powerful free and open source office suite on the market: writer (word processing), calc (spreadsheets), impress (presentations), draw (vector graphics and flowcharts), base (databases), and math (formula editing). octave https://www.gnu.org/software/octave/ gnu octave is a high-level interpreted language, primarily intended for numerical computations. it provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. it also provides extensive graphics capabilities for data visualization and manipulation. octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. the octave language is quite similar to matlab so that most programs are easily portable. http://www.scilab.org/en scilab is free and open source software for numerical computation providing a powerful computing environment for engineering and scientific applications. scilab includes hundreds of mathematical functions. it has a high level programming language allowing access to advanced data structures, 2d and 3-d graphical functions. a large number of functionalities is included in scilab. http://www.abinit.org/ abinit is a package whose main program allows one to find the total energy, charge density and electronic structure of systems made of electrons and nuclei (molecules and periodic solids) within density functional theory (dft), using pseudopotentials and a planewave or wavelet basis… learn more in the internet site! https://csc.fi/web/elmer/elmer elmer is an open source multiphysical simulation software mainly developed by csc it center for science (csc). elmer development was started 1995 in collaboration with finnish universities, research institutes and industry. after its open source publication in 2005, the use and development of elmer has become international. elmer includes physical models of fluid dynamics, structural mechanics, electromagnetics, heat transfer and acoustics, for example. these are described by partial differential equations which elmer solves by the finite element method (fem). scidavis http://scidavis.sourceforge.net/ scidavis is a free application for scientific data analysis and visualizat oaj materials and devices vi http://scidavis.sourceforge.net/ http://www.csc.fi/ https://csc.fi/web/elmer/elmer http://www.abinit.org/ http://www.scilab.org/en https://www.gnu.org/software/octave/ https://www.libreoffice.org/ first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com http://team1.co-ac.com aims and participants the transpyrenean encounter on advanced materials aims at establishing or reinforcing contacts and collaborations between groups of france, spain, and portugal, in the fields of advanced materials, and related topics. the encounter is also open to participants from other countries, wishing to construct or having collaborations with groups of the above countries. we hope that this meeting, team-1, will open a series of encounters, and the preparation of team-2 will be discussed by the binational permanent committee in near future. covered topics all topics related to advanced materials of different types are relevant ; in particular presentations may belong to the following categories : advanced electronic, optical, and optoelectronic materials, advanced materials for energy, advanced engineering materials, advanced materials for biomedical applications, nanomaterials and low dimensional materials, miscellaneous advanced materials, smart materials, advanced materials in systems, and also infrastructures for materials characterization and advanced characterisation techniques. local committees general organizer saint-gregoire pierre universities of toulon and nîmes / collaborating academics (france) chair committee claverie alain cemes-cnrs, toulouse, france gagou yaovi university of picardie, amiens (france) saint-gregoire pierre universities of toulon and nimes/ collaborating academics (france) organizing committee allouche billal leti, cea grenoble (france) asbani bouchra pmn/st2eimn, nantes (france) frémy marie-angèle university of toulon (france) pérez annie university of aix-marseille (france) team1 – presentation sète (france) 4, 5, 6 july 2017 scientific committees international scientific committee the scientific committee is constituted of about 35 scientists from france, portugal, spain, and few other countries, working in the field of advanced materials. the role of this international committee is to discuss the scientific orientation of the encounter(s), propose invited talks, topics, etc. list of members : alonso, julio a., university of valladolid, valladolid, spain ; baron thierry, ltm – umr 5129 cnrs-uga, grenoble, france ; bernard samuel, cnrs/iem, montpellier, france ; bourges philippe, laboratoire léon brillouin – llb – cen-cea, saclay, france ; buchaillot lionel, iemn cite scientifique, villeneuve d'ascq, france ; bustarret etienne, cnrs, institut néel, grenoble, france ; casanove marie-josé, cemes-cnrs, toulouse, france ; catalan, gustau, icrea-icn2, barcelona, spain ; cavaleiro, albano, university of coimbra, coimbra, portugal ; chaudret bruno, lpcno, umr 5215 insa-cnrs-ups, insa, toulouse, france ; claverie alain, cemes-cnrs, toulouse, france ; coutaz jean-louis, imep-lahc, university savoie mont blanc, le bourget du lac, france ; de teresa nogueras, josé maria, csic-university of zaragoza, zaragoza, spain ; dugourd philippe, ilm, university lyon1, lyon, france ; fernandez sanchez paloma, department física de materiales, fac. of physics, university complutense, madrid, spain ; gaffet eric, ijl, university of lorraine, nancy, france ; gagou yaovi, lpmc, university of picardie jules verne, amiens, france ; kadri abderrahmane, lemop, university of oran, oran, algeria ; magén, césar, university of zaragoza, fundación araid, zaragoza, spain ; maignan antoine, crismat, ensicaen, caen, france ; mano joão f., university of aveiro, aveiro, portugal ; maré thierry, iut saint malo, university rennes1, lgcgm, rennes, france ; martingago, jose a., icmm-csic, madrid, spain ; maurel françois, itodys, university paris diderot , paris, france ; monteiro, teresa, department of physics and i3n, university of aveiro, aveiro, portugal ; muller pierre, cinam, university aix-marseille, marseille, france ; peláiz-barranco, aimé, ferroic materials group, physics faculty, havana university, la habana, cuba ; remiens denis, iemn doae – university of valenciennes and hainaut cambrèsis (uvhc) and ustl, valenciennes, france ; saint-grégoire pierre, mipa laboratory, universities of toulon and nîmes, nîmes/toulon, france ; vilatela, juan josé, imdea materials, madrid, spain ; zunigaperez, jesus, crhea, cnrs, valbonne, france. permanent restricted committee besides the international committee, team organization involves a permanent restricted committee the role of which is to discuss the programmation of next encounters, decide about periodicity of encounters, choose among different propositions (date, place, etc). composition : alonso julio, claverie alain, fernandez sanchez paloma, gagou yaovi, monteiro teresa, saint-gregoire pierre logos design : anna cantaluppi team1 – presentation first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com first transpyrenean encounter on advanced materials : forewords the idea to organize an event having as main goal to favour and develop contacts and collaborations on advanced materials on both sides of pyrenean mountains has emerged progressively through informal discussions at the occasion of various meetings between individual scientists. finally the situation has accelerated few months ago, with a proposition to organize it during the summer 2017, under the aegis of the association collaborating academics (http://co-ac.com). it was a real challenge to succeed to be ready in time : first we had to think to the structure and general organization, then to constitute the local committees, the permanent committee, and the scientific committee. it took time to do this, and when we finally had a complete list of members, we had a rather short time to discuss about the content of team-1. as a consequence everything was not perfect, but we did our best to launch and organize team-1, which had the advantage to « start the process », to make the original idea real, and to define the basis of further meetings of the series, if there is a continuation, which we hope ! team-1 has gathered less than 40 participants, but a meeting with such a reasonable number of persons is an advantage to interchange, know each other, and discuss about collaborations. most of participants were of course from france, portugal, and spain, but few other countries had representants, like algeria, cuba, poland, and senegal that we had the pleasure to welcome. we hope to see in future other meetings of the series being organized in various places, and to see the development of initial ideas to allow the setup of scientific networks on various topics on advanced materials. this first encounter has given the opportunity to exchange about numerous fields on covered topics, having the advantage to attract attention of participants to other research problems than their own, thus favouring contacts between researchers of different specialities. may this series of meetings contribute to meet the challenges and needs of humanity in the next decades, in which the role of advanced materials should be determinant in many respects! before closing these forewords, i would like to thank all those who made this meeting possible : members of organizing committees, members of the staff of lycée charles de gaulle who did their best to host the encounter, the university complutense de madrid for financial support, and all participants for their interesting and good quality communications ! prof. pierre saint-grégoire mipa laboratory universities of toulon and nîmes team1 – presentation http://co-ac.com/ first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com http://team1.co-ac.com communications team1 – presentation sète (france) 4, 5, 6 july 2017 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com electron holography for the quantitative measurements of electric and magnetic properties in nanostructures e. snoeck, c. gatel, l. a. rodríguez, a. masseboeuf cemes-cnrs 29, rue jeanne marvig, b.p. 94347, f-31055 toulouse cedex, france. corresponding author : snoeck@cemes.fr keywords : electron holography, magnetic domain wall, electric charges electron holography (eh) is powerful tem method particularly efficient for the quantitative studies of local electrostatic and magnetic fields with spatial resolution of the order of few nanometers and over fields of view as large as few microns [1]. in addition, eh allows performing in-situ measurements for the analysis of magnetic reversal processes as function of external applied field at various temperatures or of domain wall (dw) motion under the application of an electrical pulse. the basics of eh and of the experimental procedure will be first presented and we will illustrate the capabilities of eh to measure the number of electric charges trapped in an insulating nanostructure [2]. in a second part, we will present recent eh results obtained on the magnetic configuration change in fe nanocubes for sizes varying between 20 to 30 nm [3] and on the magnetic domain wall configuration in diameter-modulated fecocu nanowires [4]. we will discuss these results combined with micro-magnetic simulations. references: [1] magnetic mapping using electron holography e. snoeck and c. gatel in transmission electron microscopy in micronanoelectronics ed. a. claverie, editeur : iste ltd and john wiley & sons inc (2012) [2] counting elementary charges on nanoparticles by electron holography, c. gatel, a. lubk, g. pozzi, e. snoeck, and m.j. hÿtch, phys. rev. lett. 111, 025501 (2013) [3] size specific spin configurations in single iron nanomagnet: from flower to exotic vortices. c. gatel, f. bonilla, e. snoeck, b. warot-fonrose, b. chaudret, l-m. lacroix, and t. blon nano lett., 2015, 15 (10), pp 6952–6957 [4] quantitative nanoscale magnetic study of isolated diameter-modulated fecocu nanowires l. a. rodriguez, c. bran, d. reyes, e. berganza, m. vazquez, c. gatel, e. snoeck and a. asenjo acs nano, 2016, 10 (10), pp 9669–9678` materials and devices, vol 2, #1, p 1 (2017) – doi: 10.23647/ca.md20170407 mailto:snoeck@cemes.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com macroscopic cnt fibers as multifunctional material for large-area flexible all-solid-state edlc e. senokos (1), v. reguero (2), l. cabana (3), j. palma (4), r. marcilla (5), j. j. vilatela (6) (1) imdea materials institute, spain, evgeny.senokos@imdea.org (2) imdea materials institute, spain, victor.reguero@imdea.org (3) imdea materials institute, spain, laura.cabana@imdea.org (4) imdea energy institute, spain, jesus.palma@imdea.org (5) imdea energy institute, spain, rebeca.marcilla@imdea.org (6) imdea materials institute, spain, juanjose.vilatela@imdea.org juan jose vilatela: juanjose.vilatela@imdea.org keywords : carbon nanotube fibers, all-solid supercapacitor, energy storage, polymer electrolyte, structural composite growing interest to multifunctional energy storage systems providing high electrochemical properties alongside with excellent flexibility and capability to withstand static and dynamic mechanical stresses demands new electrode materials and architectures. carbon nanotube (cnt) fibres is considered as highly appealing candidate material for flexible energy storage owing to their unique combination of excellent electrical conductivity (3.5x10⁵ s/m), highperformance mechanical properties (specific tensile strengths of 1,5 gpa/sg, modulus of 60 gpa/sg and toughness of 80 j/g) and high surface area (260 m²/g). here we present a simple method to fabricate large area (100 cm²) all-solid edlcs made by cnt fibres and ionic liquid-based polymer electrolyte membrane. electrochemical characterization demonstrate excellent performance of all-solid devices with the maximum gravimetric capacitance, energy and power densities of 28 f/g, 11.4 wh/kg and 46 kw/kg very similar to those obtained using pure il, and which can be taken as a benchmark to evaluate the efficiency of the edlc assembly process. furthermore, self-standing all-solid edlcs exhibit excellent cyclic stability over 10000 cycles with capacitance retention more than 96% at 3.5v of applied voltage and 5 ma/cm² current density. the edlc devices can be repeatedly bent and folded 180° without degradation of their properties. moreover, bending produces reversible increases in energy density of as much as 25%. mechanical test of sc devices demonstrate a great perspective to use these materials as structural edlc. implementation of the tensile properties of an individual filament in resulting composite would enable achieving specific modulus and strength of approximately 0.37 gpa/sg and 18 gpa/sg, respectively. materials and devices, vol 2, #1, p 2 (2017) – doi: 10.23647/ca.md20170407 mailto:juanjose.vilatela@imdea.org mailto:juanjose.vilatela@imdea.org mailto:rebeca.marcilla@imdea.org mailto:jesus.palma@imdea.org mailto:laura.cabana@imdea.org mailto:victor.reguero@imdea.org mailto:evgeny.senokos@imdea.org first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com materials and methods, using oxalic precursors. applications to soldering and component manufacturing by selective laser decomposition ph. tailhades (1), i. pasquet (1), h. le trong (1), v. baco-carles (1), l. presmanes (1), c. bonningue (1), m. gougeon (1), k. kiryukhina (2), v. conedera (3), p.f calmon (3), d. dragomirescu (4), h. camon (3) (1) institut carnot chimie balard cirimat, umr cnrs 5085, université de toulouse, université paul sabatier 118 route de narbonne, 31 062 toulouse cedex 9, france. (2) centre national d’etudes spatiales, 18 avenue edouard belin, 31 401 toulouse cedex 9, france (3) laas-cnrs, université de toulouse, cnrs, 7 avenue du colonel roche, 31 400 toulouse (4) laas-cnrs, université de toulouse, cnrs, insa, 7 avenue du colonel roche, 31 400 toulouse corresponding author : tailhades@chimie.ups-tlse.fr keywords : oxalate, selective laser decomposition, soldering, patterning, selective laser sintering transition metal oxalates have very often been used as precursors for the preparation of oxides or metals at moderate temperatures. during the oxalate decomposition, nanoparticles are generally formed. they exhibit a high sinterability, or even lower melting points compared with the bulk state. these properties can be used to form solders at low temperatures, with metals having high bulk melting points, or to directly form oxides or metals by local decomposition of the oxalates in a focused laser beam. figure 1 : (a) illustration of the sensitivity of silver oxalate to decomposition: periodic formation of silver particles under the electron beam of a sem (b) formation of ag nanoparticles inside the oxalate porosity resulting from the thermal decomposition (c) metallic silver grid obtained by selective laser decomposition of silver oxalate (the remaining oxalate was removed by washing) (d) copper oxide pattern inside a copper oxalate layer. this talk details more specifically, the behavior of the silver oxalate and its advantage for the brazing electronic components at low temperature and the shaping of two-dimensional metallic structures, using conventional photolithography machines. other examples, described and discussed, relate to the production of two-dimensional semiconducing or ferrimagnetic structures based on single or mixed oxides. materials and devices, vol 2, #1, p 3 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com scanning thermal microscopy thermal probing and acting at the nanoscale m. j. pereira (1), j. s. amaral (2), n. j. o. silva (3), v. s. amaral (4) (1) ciceco and physics department, university of aveiro, portugal, mariasapereira@ua.pt (2) ciceco and physics department, university of aveiro, portugal, jamaral@ua.pt (3) ciceco and physics department, university of aveiro, portugal, nunojoao@ua.pt (4) ciceco and physics department, university of aveiro, portugal, vamaral@ua.pt corresponding author : mariasapereira@ua.pt keywords : sthm, microscopy, thermal management, nano-thermal analysis, atomic force microscopy (afm) thermal nano-characterization techniques with high spatial resolution are fundamental to address thermal issues which may compromise the performance of miniaturized devices and materials. scanning thermal microscopy (sthm) is a probing and acting technique based on atomic force microscopy that uses a nano-probe designed to act as a thermometer and a resistive heater. using a park systems xe7 scanning thermal microscopy equipment (tip radius ~ 100 nm, temperature up to ~160ºc, sensitivity ~ 0.1ºc and 50 nm spatial resolution) we present the versatility of the technique taking several approaches to study material properties [1]. sthm’s high spatial resolution and ability to perform surface and sub-surface thermal imaging are highlighted in the study of nanocomposite structures with complex inhomogeneities, such as graphene oxide(go)/poly(lactic acid) (pla) (fig. 1). assisted by the control of the global material’s temperature with external heat sources, the nano-probe’s thermal sensing and actuating abilities induce local structural transformations in materials such as the ferromagnetic shape memory alloy ni-mn-ga and map the spatial distribution of local martensite-austenite transition temperatures. fig.1 left: schematic of the sthm thermal nano-probe heating profile when in contact with the sample; topography (center) and thermal conductivity contrast (tcc) (right) of go/pla nanocomposite (tcc scan showing details on entwining of polymeric chains absent from topography scan). samples provided by prof. ana barros (univ. aveiro) [1] m. j. pereira, j. s. amaral, n. j. o. silva, v. s. amaral, microscopy and microanalysis, v 22, issue 6 (2016) 1270-1280 materials and devices, vol 2, #1, p 4 (2017) – doi: 10.23647/ca.md20170407 mailto:mariasapereira@ua.pt first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com piezoelectric zno/pva composite films c. mateo-mateo (1, 2), j. yuan (1), m.a. correa-duarte (2), a. colin (1), p. poulin (1) (1) centre de recherche paul pascal (crpp), cnrs, université de bordeaux, france (2) department of physical chemistry, biomedical research center (cinbio), universidade de vigo, spain corresponding author: mateo@crpp-bordeaux.cnrs.fr keywords : piezoelectric, composite, films piezoelectric energy harvesting [1] is a promising technology for energy recovery from vibration or shock. although piezoelectric (pz) materials are used in several applications such as generators, fuel lighters, sensors in automobiles…their use on large scale remains challenging. the main problem relies on the lack of mechanical resistant and efficient materials suitable for new applications. herein, we present the hydrothermal synthesis of pz zno nanowires (nws) with high aspect ratio and the fabrication of zno/pva composite films by embedding the zno particles in the polymer matrix. the application of an electrical field allows the alignment of the zno nws giving a strong net macroscopic polarization under stress. mechanical deformation tests were also performed on the composite films observing the presence of strong voltage peaks that could be related to piezoelectric effects. other mechanisms related to triboelectric contributions will be discussed. the combination of the flexible polymer (pva) with high aspect ratio pz particles [2] could lead to obtain efficient pz films with high strength and flexibility. fig 1. zno/pva freestanding composite film (a) and sem images of the composite film (b, c). view of the top au electrode on the composite film (a). electrical response when the film is mechanically deformed (d). references [1] j. curie, p. curie, bulletin de la société minéralogique de france, vol 3 (1880) 90-93 [2] c. andrews, y.r. lin, h.x. tang, h.a. sodano, journal of intelligent material systems and structures 22, 6 (2011) 1879-1886 materials and devices, vol 2, #1, p 5 (2017) – doi: 10.23647/ca.md20170407 mailto:mateo@crpp-bordeaux.cnrs.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com when high pressure-high temperature synthesis helps to discover new oxides: examples from multiferroism and magnetic frustration p. zuo (1,2), c. darie (1,2), c. goujon (1,2), m. legendre (1,2), c.v. colin (1,2), h. klein (1,2), p. bordet (1,2) (1) univ. grenoble alpes, inst neel, f-38000 grenoble, france (2) cnrs, inst neel, f-38000 grenoble, corresponding author : celine.darie@neel.cnrs.fr keywords : high pressurehigh temperature, oxides, multiferroism, magnetic frustration in the last decades, high pressure (> 1gpa) has been increasingly used in different fields of research ranging from earth science to solid state physics, chemistry and material science. at institut néel, grenoble, a state-of-the-art and unique instrumental park is dedicated to solid-state synthesis, crystal growth and characterization of materials under extreme conditions (fig.1). in this contribution we start with a description of these high pressure (up to 15gpa) and high temperature (up to 1500°c) facilities, with an extension to recent developments and new experimental set-up as dta (differential thermal analysis) and xrd (x-ray diffraction). in a second part, we will present two studies of hp-ht syntheses in the field of research of new materials that are multiferroic or show magnetic frustration, respectively. the case of a new form of a spin liquid phase 1 ba3nisb2o9 obtained under high pressure-high temperature will be presented. the second example will show the stabilization of small rare-earth compounds in the series nalncowo6 (ln = rare earth), a new class of potentially multiferroic compounds, with the help of hp-ht2. fig. 1: belt (left) and conac (right) devices at institut néel (1) “a new high pressure form of ba3nisb2o9” c. darie, c. lepoittevin, h. klein, s. kodjikian, p. bordet, c.v. colin, o.i.lebedev, c. deudon, c. payen journal of solid state chemistry 237(2016)166–173 (2) "structural study of a doubly ordered perovskite family nalncowo6 (ln=y, la, nd, pr, sm, eu, gd, tb, dy, ho, er, yb): hybrid improper ferroelectricity in nine new members" p. zuo, c. v. colin, h. klein, p. bordet, e. suard , e. elkaim and c. darie submitted to inorganic chemistry materials and devices, vol 2, #1, p 6 (2017) – doi: 10.23647/ca.md20170407 mailto:celine.darie@neel.cnrs.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com diamond interfaces in power devices: electron microscopy issues d. araújo (1), j.c. piñero(1), f. lloret(1,2), p. villar(1), m. gutiérrez (1), m. florentin (2), t. pham (2), d. eon(2), j. pernot (2) (1) departamento de ciencias de los materiales im y qi, universidad de cádiz, 11510 puerto real (cádiz), spain, daniel.araujo@uca.es (2) institut néel, cnrs-ujf, av. des martyrs, 38024 grenoble (france) (3) univ. grenoble alpes, f-38000 grenoble (france) (4) institut universitaire de france, 103 boulevard saint michel, 75005 paris (france) corresponding author : daniel.araujo@uca.es keywords : diamond, power devices, electron microscopy, mpcvd, tem the growing interest on the applications of diamond for power devices relies in its promising properties as a high breakdown field, high carrier mobility and high thermal conductivity. indeed, diamond-based schottky diodes, using zr metal over oxygen-terminated diamond surfaces, showing power figure of merit of 244 mwcm -2 have been recently reported. however, designing reliable diamond schottky diodes (sbd) or diamond-mos capacitors are still a technological challenge. indeed, a lack of knowledge of the bandgap behavior in hydrogen/oxygen-terminated diamond surfaces contacting metal and oxide layers should be first understood to take advantage of the outstanding properties of diamond in the electronic power devices engineering. to pursue this objective, scanning transmission microscopy (stem)-based techniques as high angle annular dark field (haadf) and electron energy loss spectroscopy (eels), joined with x-ray photoelectron spectroscopy (xps) and cathodoluminescence (cl), are used to analyse the diamond/oxide interfaces of mosfets and sbd structures. the atomic surface configuration related to diamond/al2o3 interface bandgap levels joined to the ald-grown oxide bandgap itself are reported. the effect of the cherenkov and plasmon-related peaks on the eg determination will be evaluated. a relationship between nanostructure and energy bandgap in oxide layer at a nanometer-scale will be presented showing the importance of such aspects in the design of either mosfet or sbd diamond related devices. materials and devices, vol 2, #1, p 7 (2017) – doi: 10.23647/ca.md20170407 mailto:daniel.araujo@uca.es first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com electrodeposition strategies for antibacterial calcium phosphate coatings on titanium c. pierre (1), e. vidal (2), g. bertrand (1), e. ruperez (2), c. rey (1), d. rodriguez (2), c. combes (1) (1) cirimat, université de toulouse, france, camille.pierre@ensiacet.fr (2) biomaterials, biomechanics and tissue engineering group, upc, spain, elia.vidal@upc.edu corresponding author: camille.pierre@ensiacet.fr keywords: electrodeposition, calcium phosphate, antibacterial, coating, titanium implants titanium and its alloys are the most used biomaterials for orthopedic and dental implants thanks to their good biocompatibility. nevertheless, osseointegration of these implants is long to achieve and that is why surface treatments are applied to promote bone healing and growth. for that purpose, calcium phosphate coatings are commonly prepared [1]. several coating processes can be used such as plasma spray, sol-gel, laser-deposition or electrodeposition. among these techniques, electrodeposition is very attractive because it allows to produce thin coating on complex shapes and it is a low temperature process that permits to associate temperature-sensitive molecules of biological and/or therapeutic interest [2]. a second problem linked to the implantation is the bacterial colonization that may lead to implant loosening. the purpose of this study is to create a low temperature calcium phosphate bioactive coating on titanium to enhance osseointegration and also to associate an antibacterial agent with this layer to prevent post-operative infections [3], [4]. in this study, two strategies have been developed: (5) calcium phosphate electrodeposition was realized at constant potential and an antibacterial element (ie. ag, cu,…) is then introduced by ionic exchange; (6) calcium phosphate and an antibiotic molecule were co-deposited by pulsed-electrodeposition. the influence of the process parameters (current density/potential, ton/toff ratios and electrolyte temperature) has been investigated. scanning electron microscopy, x-ray diffraction, raman and ftir spectroscopies were used to characterize the coatings with and without the antibacterial agent. moreover, adhesion between the substrate and the coating was also investigated. preliminary antibacterial and drug release tests were also realized. coatings prepared by the two different methods were composed of mixed calcium phosphate phases. changes in the process parameters produced different crystal morphologies. the addition of an antibacterial compound did not seem to influence the coating formation and its chemistry. all the studied coatings had good mechanical stability, in terms of adhesion and shear strength. in vitro antibacterial properties were also demonstrated against e. coli and s. aureus. [1] r.a. surmenev et al., acta biomater., vol. 10, no2, pp 557-579, 2014 [2] r.i. asri et al., j. mech. behav. biomed. mater., vol. 57, pp 95-108, 2016 [3] d. scharnweber et al., j. mater. med., vol. 18, no2, pp 391-397, 2007 [4] x. lu et al., j.r. soc. interface, vol.8, no 57, pp 529-539, 2011 acknowledgments: the authors thank the midi-pyrénées region (bioactisurf project n°14054394), mat201567183-r(mineco/feder), agaur fi-drg and the cost action td1305 for supporting this research work. materials and devices, vol 2, #1, p 8 (2017) – doi: 10.23647/ca.md20170407 mailto:camille.pierre@ensiacet.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com aberration-corrected electron microscopy of advanced functional nanomaterials c. magén (1) (1) laboratorio de microscopías avanzadas (lma), instituto de nanociencia de aragón (ina) araid, universidad de zaragoza, spain, cmagend@unizar.es corresponding author : cmagend@unizar.es keywords : (scanning) transmission electron microscopy, aberration correction, nanomagnetism, complex oxides, nanostructures the fast emergence of nanoscience during the last decades has been favoured by the development of new nanocharacterization tools with unprecedented resolution and sensitivity. in addition to the invention of scanning probe microscopy, traditionally considered the starting signal of nanotechnology, the development of other types of microscopy techniques have contributed decisively to our understanding of the world at nanometer scale. in the field of transmission electron microscopy (tem), the most crucial milestone has been the development of aberration correctors. this new technology has offered scientist the possibility of atomically resolved characterization of structural, chemical and electronic properties of a wide range of advanced (nano)materials, with an undeniable impact on the development of novel materials in fields such as oxide thin films, semiconductor nanostructures, carbon based materials, magnetic nanostructures, nanoparticles, etc. this lecture will review several applications of advanced tem techniques that have been developed in the last years at the lma, focusing on the work carried out in advanced materials for spintronic applications and the infrastructures available at the lma to carry out these investigations. one of the subjects will the characterization of multiferroic oxide thin films, particularly the analysis of defects and domain walls that confer these materials unexpected physical properties, by the combination of atomic resolution imaging and spectroscopic techniques. secondly, the potential of interferometric tem techniques for the imaging of magnetization states at the nanometer scale will be demonstrated by illustrating the characterization of individual magnetic nanostructures and heterostructures grown by focused electron and ion beam techniques with different architectures. materials and devices, vol 2, #1, p 9 (2017) – doi: 10.23647/ca.md20170407 mailto:cmagend@unizar.es first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com flexoelectricity: from semiconductors to memory devices g. catalan (1, 2), j. narvaez (2, 3), k. cordero (2), u. bhaskar (2,4), n. domingo (2) (1) icrea, barcelona, spain (2) icn2 (institut catala de nanociencia i nanotecnologia), barcelona, spain (3) universidad de los andes, bogotá, colombia (4) purdue university, indiana, usa corresponding author: gustau.catalan@icn2.cat keywords : flexoelectricity, ferroelectricity, piezoelectricity, mems, oxides flexoelectricity allows inducing polarization by bending (or by any other inhomogeneous deformation) in dielectrics of any symmetry, including centrosymmetric materials such as srtio3 and also ferroelectrics such as batio3. while this has been traditionally exploited for making piezoelectric-like sensors using non-piezoelectric materials, there is a much wider variety of functional possibilities that have only recently started being explored. in my talk, i will cover three of them which our laboratory has been very directly involved: 1) measuring flexoelectricity not on dielectric insulators but on semiconductors. in the latter, we have seen that the effective flexoelectric coefficient can be orders of magnitude larger than the flexoelectricity of insulators, and in addition it scales with thickness in such a way that it is a relevant effect even at the macroscale. 2) using inverse flexoelectricity to make actuators that bend in response to a voltage (as opposed to sensors that generate a voltage in response to bending). these have been made in the form of mems cantilevers grown on silicon substrates, and are thus a technologically promising device concept. 3) exploiting flexoelectricity not only to mechanically write ferroelectric domains, but also to mechanically read them, enabling the full voltage-free operation of a ferroelectric memory. materials and devices, vol 2, #1, p 10 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com characterizing magneto-thermal materials and processes at ciceco-ua infrastructures and expertise v. s amaral (1), j. s. amaral (2), n. j. o. silva (3), a. davarparnah (4), f. mohseni (5), t. santos (6), m. j. pereira (7) ciceco and physics department, university of aveiro, portugal (1) vamaral@ua.pt ; (2) jamaral@ua.pt ; (3) nunojoao@ua.pt ; (4) amin.davarpanah@ua.pt ; (5) f.mohseni@ua.pt ; (6) tiago.santos@ua.pt ; (7) mariasapereira@ua.pt corresponding author : vamaral@ua.pt keywords : magnetometry; thermal conductivity; infrared thermometry; magnetocaloric magnetic materials are in the front line to face challenges of energy conversion, savings and harvesting. the application of magnetocaloric materials into systems working in the vicinity of phase transitions provide the gains necessary to develop sustainable strategies for their innovative use. in the frame of thermal systems, mostly significant for cooling/heating, electrical energy supply processes and heat induction, materials optimization must also comprise their thermal conductivity, dynamic behavior and its dependence on the magnetic state of materials. to face such a combined study towards optimization of magneto-thermal materials and processes, our group at ciceco-aveiro institute of materials developed a new research infrastructure. its main instruments are:  quantum design mpms3 squid-vsm magnetometer (7 tesla/ 1.8k-400k)  hot disk tps 2500 thermal properties measurement system (thermal conductivity and specific heat) transient plane source method, (0.005 to 1800 w/m/k.) for solids or liquids, with bath (-20ºc to 180ºc) and oven (up to 750ºc). a custom assembly for measurements under 1 tesla magnetic field was also built.  flir 5600 infrared thermography camera ( -20 up to 3000ºc and 20mk resolution, up to 200 hz frame rate in full resolution). additional microscope (x5 lens, micrometer resolution) for local thermal mapping. a custom assembly for measurements under magnetic field cycling up to 1 tesla was built.  park xe-7 atomic force microscope (afm) with scanning thermal probe microscopy (sthm) probe and actuator (better than 100 nm resolution, with tip temperature up to 160ºc). we present highlights in the context of developing materials, heat transfer, and measurement techniques. ciceco-aveiro institute of materials, poci-01-0145-feder-007679 (fct ref. uid/ctm/50011/2013) is financed by national funds through fct/mec(piddac) and co-financed by feder under the pt2020 partnership agreement. materials and devices, vol 2, #1, p 11 (2017) – doi: 10.23647/ca.md20170407 mailto:vamaral@ua.pt mailto:mariasapereira@ua.pt mailto:tiago.santos@ua.pt mailto:f.mohseni@ua.pt mailto:amin.davarpanah@ua.pt mailto:nunojoao@ua.pt mailto:jamaral@ua.pt mailto:vamaral@ua.pt first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com photonic crystals and related nanostructures for the control of light trapping and emission c. seassal, l. lalouat, n.-v. hoang, h. ding, h.s. nguyen, e. drouard université de lyon; institut des nanotechnologies de lyon-inl, umr cnrs 5270, cnrs, ecole centrale de lyon, ecully f-69134, france corresponding author : christian.seassal@ec-lyon.fr keywords : nanophotonics, photonic crystals, light trapping, wavelength conversion, light emission photonic crystals and related structures offer great potentialities for the next generation photovoltaic solar cells, light emitters and wavelength converters. in this communication, we will present advanced designs and strategies to carefully control light-matter interaction with advanced photonic nanostructures. such control is based on photonic crystals and metastructures including active media and enabling a tight control of dispersion characteristics [1-2]. we will also discuss on the compromise between perfectly ordered and perturbated nanopatterns [3-4]. theoretical predictions and experimental results will be presented as illustrations. we will discuss on the integration of photonic nanopatterns in thin film silicon solar cells, with a view to optimize their conversion efficiency. we will also present approaches and results related to light-emitting and wavelength conversion photonic structures using various types of active media. [1] j. marques-hueso, r. peretti, r. abargues, b. s. richards, c. seassal, j. p. martínez-pastor, “photonic crystaldriven spectral concentration for upconversion photovoltaics,” advanced optical materials 3, pp568-574 (2014) [2] r. peretti, g. gomard, l. lalouat, c. seassal, e. drouard, “absorption control in pseudodisordered photoniccrystal thin films,” phys. rev. a 88, 053835 (2013) [3] c. seassal, l. lalouat, h. ding, e. drouard, “carefully mixing disorder and periodicity to optimize solar light trapping”, spie newsroom, solar & alternative energy, 14 july 2016 [4] l. lalouat, h. ding, b. gonzalez-acevedo, a. harouri, r. orobtchouk, v. depauw, e. drouard, c. seassal, “pseudo-disordered structures for light trapping improvement in mono-crystalline si thin-films”, solar energy materials & solar cells, 159, 649-656 (2016) materials and devices, vol 2, #1, p 12 (2017) – doi: 10.23647/ca.md20170407 mailto:christian.seassal@ec-lyon.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com p3mt/vacnt/al nanocomposites electrodes with high capacitance for supercapacitor t. vignal,a,b l. darchy,b a. boisset,b h. hauf,b j. descarpentries,b q. mestre,c m. pinault,c m. mayne-l’hermite,c p. banet,a p.h. auberta a lppi, ea 2528, 5 mail gay lussac, université de cergy-pontoise, france b nawatechnologies sa, 190 avenue célestin coq-zi, rousset, france c nimbe, cea, cnrs, université paris-saclay, cea saclay, gif-sur-yvette, france corresponding author: pierre-henri.aubert@u-cergy.fr keywords : poly(3-methylthiophene), carbon nanotubes, electrode materials, supercapacitors supercapacitors are desirable for applications requiring high power densities. among the various types of supercapacitors, electrochemical ones based on electronically conducting polymers (ecp) as electrode material are particularly interesting because of their high capacitance (1). however, their energy densities and their electrochemical stability are still limited (2,3). in order to improve the capacitance and the energy density of such pseudo-capacitive supercapacitors, our strategy consists in making nanocomposite electrodes of poly-3-methylthiophene (p3mt) in ionic liquid media. these depositions were made on the surface of nanostructured electrodes composed of very dense carpet of vertically aligned carbon nanotubes (10 11 – 1012 cnt/cm²) on an aluminium collector (vacnt/al). in this study, different electropolymerizations methods (cyclic voltammetry, galvanostatic, potentiostatic, pulsed methods (3,4)) were used to optimized the deposition and the storage properties of p3mt. thus, nanocomposites with weight ratios of p3mt/(p3mt+cnt) ranging from 5 to 90% were obtained and characterized by electrochemistry (cv and eis) and microscopy. the results show that conformal depositions of polymers were obtained. in the case of the best nanocomposites, the electrodes capacitance increase from 32 mf/cm² to 1300 mf/cm². finally, stability tests of electrodes and coin cells assembly were studied and their performances will be presented. references: [1] mastragostino m. et al., adv. mater. 1996, 8, 331. [2] schnoor t. i.w. et al., carbon 2013, 60, 229. [3] lagoutte s. et al., electrochimica acta 2014, 130, 754. [4] sharma r.k. et al., electrochem. commun. 2008, 10, 268. materials and devices, vol 2, #1, p 13 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com biomimetic nanopore to design “smart” membranes s. balme (1) (1) institut européen des membranes, université de montpellier, france, corresponding author : sebastien.balme@umontpellier.fr keywords : single nanopore, membrane, biomimetic, sensor, soft matter in the life science, it is well known that ionic bio-channels insure exchange and communication of living cells. their properties in terms of ionic permeability, selectivity and response regarding the environment are exceptional. unfortunately, the transfer of these properties to artificial set-up whose the mechanical strength is high enough to be useful in many different types of applications has not been made. the limitations of artificial nanopore membranes prepared by track-etched polymer sheets or transmission electron microscopy irradiation of thin silicon nitride film are the weak ionic selectivity and unresponsiveness against stimuli. thus the main challenge consists of mimicking biological channels properties to design artificial nanopore membrane which is able to modulate their transport. to achieve this goal two strategies will be explored. the first one consists to a solid-state nanopore functionalized with more and less complex systems which permits to improve their properties. the second strategy is based in insertion of protein inside nanopore in order to obtain hybrid biological/artificial system. this strategy aims to combine the advantages of both solid-state nanopores (robustness, number, size and shape control) and biological channels (selectivity, precise structure) in this talk, we will discuss on the different strategies to functionalize single track-etched nanopore using chemical grafting of (bio)macromolecule, self-assembly of poly-electrolytes or direction insertion of ion channel. such functionalization permits to obtain nanopore with high ionic selectivity such as ionic-diode as well as design nanovalves which respond to ligand anchoring, ph, light. we will show also the potentialities of functionalized nanopores for specific bio-sensor as well as osmotic energy. materials and devices, vol 2, #1, p 14 (2017) – doi: 10.23647/ca.md20170407 mailto:sebastien.balme@umontpellier.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com fe-afe based functional oxide materials f. ponchel(1), d. rémiens(1), t. lasri(2), x. guo(1, 3), l. jianyun(1, 3), h. liuyang(1, 3), j. ge(1, 3), y. chen(3), g. wang(3) (1) iemn – uvhc – umr cnrs 8520 – groupe mamina – le mont houy 59313, valenciennes cedex 9, france denis.remiens@univ-valenciennes.fr (2) iemn – dhs – umr cnrs 8520 – groupe mitec cité scientifique avenue henri poincaré, cs 60069 59652 villeneuve d'ascq cedex, france tuami.lasri@iemn.univ-lille1.fr (3) key laboratory of inorganic functional materials and devices shanghai institute of ceramics, chinese academy of sciences (siccas) 1295 dingxi road, shanghai, 200050, china genshuiwang@mail.sic.ac.cn corresponding author : denis.remiens@univ-valenciennes.fr keywords : anti ferroelectric, storage energy, high frequency tunability. lead free piezoelectric material in this talk we will present some results obtained in three directions, namely anti ferroelectric (afe) thin films for energy storage applications, ferroelectric thin films for microwave applications and lead-free ferroelectric thin films which applications are potentially very large. anti ferro electric (afe) thin films for energy storage applications. the well known pbzro3 (pz) afe material is deposited by rf magnetron sputtering on silicon substrate. more precisely, highly (001)-oriented pure pz films and sn-substituted pz films are deposited on (001)-lanio3 buffered sio2/si substrates. different sn-substituted pbzro3 films (pbzr1-xsnxo3, x = 0%, 3%, 5%, 10%) with orthorhombic anti-ferroelectric phase are fabricated. the effects of sn substitution on the structure and energy performance have been investigated in details. in another topic research, the dielectric properties (relative permittivity and losses) of pzt, pst and bst films were measured up to 60 ghz using coplanar waveguides (cpw). based on the cpw scattering parameters measurement, the frequency dependence of the complex permittivity has been determined thanks to a homemade numerical code based on finite elements. even at 60 ghz a large tunability of 47%, 30% and 60% has been measured for pzt, pst and bst respectively. lead-based piezoelectric materials are well known for their excellent piezoelectric properties. however, due to the effects of lead toxicity, since recently it is desired to reduce lead-based materials usage in electronic devices. therefore, lead-free materials have gained much interest in the microelectronic industry. in this context we have been working on lead-free bi0.5na0.5tio3 (bnt) piezoelectric thin films. bnt films were deposited on pt/tiox/sio2/si substrates by sputtering. a piezoelectric coefficient (d33effmax) of 80 pm/v was obtained. bnt is regarded as an interesting alternative to pzt for mems application. materials and devices, vol 2, #1, p 15 (2017) – doi: 10.23647/ca.md20170407 mailto:denis.remiens@univ-valenciennes.fr mailto:genshuiwang@mail.sic.ac.cn mailto:tuami.lasri@iemn.univ-lille1.fr mailto:denis.remiens@univ-valenciennes.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com energy harvesting materials based on carbon nanotube fibre for tough electronics a. monreal-bernal, juan j. vilatela imdea materials institute, eric kandel 2, getafe 28906, spain corresponding author : alfonso.monreal@imdea.org keywords : carbon nanotube fibre, zinc oxide, tough electronics, schottky barrier, photoconductivity nanocarbons are very popular materials to interface with semiconductors. they combine extraordinary mechanical properties, high thermal stability, thermal conductivity and more importantly, very high carrier mobility. they have been shown to improve performance of (opto)electronic devices including solar cells, photoelectrochemical cells, and other applications involving interfacial charge transfer processes. a porous network of cnts can act as a large-area scaffold for the semiconductor and be used as current collector to harvest carriers generated in the semiconductor by photovoltaic, photochemical and piezoelectric processes. in the quest for making robust, flexible large-area devices based on nanocarbon/semiconductor hybrids (and other semiconductors) challenges remain in terms of the quality of nanocarbon/semiconductor junction that can be produced using simple large-area processes, and the mechanical robustness of these hybrid materials. in this work we present a study on the structure and electronic properties of 10 cm 2 scale zno/cnt fiber materials. the carbon nanotube fibers (cntf) combine a high surface area with bulk tensile strength, toughness and in-plane conductivities superior to steel and much greater than those of conventional vacuum-filtered cnt/graphene membranes. they are therefore ideal electrodes/current collectors to be combined with semiconductors, not only to produce new tough and efficient devices, but also as a test system to study lowdimensional properties of cnt/semiconductor junctions on a macroscopic scale. with these objectives in mind, this work presents a detailed characterisation of the electronic properties of bulk schottky barrier heterojunctions between cntf and zno, from which various parameters of interest are extracted, including junction energy levels, dopant concentration, ideality factor and interfacial resistance. the hybrid material is also shown to be highly piezoresistive and piezoelectric, and as a demonstration of interfacial charge transfer we show piezoelectric energy harvesting. materials and devices, vol 2, #1, p 16 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com epitaxial growth of nanostructured functional oxide thin-films by solution chemistry josé m. vila-fungueiriño (1), a. gómez (2), r. moalla (3), g. saintgirons (3), c. magén (4), j. gázquez (2), r. bachelet (3), m. gich (2), f. rivadulla (5), a. carretero-genevrier (1) (1) institut d’électronique et des systèmes (ies), umr 5214, bâtiment 5, 860 rue saint priest, 34090 montpellier, france (2) institut de ciència de materials de barcelona (icmab), consejo superior de investigaciones científicas (csic), campus uab 08193 bellaterra, spain (3) institut des nanotechnologies de lyon (inl) umr 5270, 36 avenue guy de collongue, 69134 ecully, france (4) departamento de física de la materia condensada, universidad de zaragoza, zaragoza, spain (5) centro de investigación en química biolóxica e materiais moleculares (ciqus), universidade de santiago de compostela, 15782 santiago de compostela, spain jose-manuel.vila@ies.univ-montp2.fr keywords: epitaxial thin films, oxides, polyler assisted deposition the variety of structures and properties provided by oxides offers an important route for the development of new devices integrated on different substrates such as silicon. at the interface of thin films and nanostructures the physical properties can strongly differ from bulk state due to the low dimensionality conditions imposed. in this regard, the control of crystallization mechanism at the nanoscale provided by the chemical solution methods is an affordable alternative to physical deposition techniques. however, the integration of functional oxides on silicon need to be further developed due to the dissimilarities on these materials, i.e. chemical reactivity, structural parameters, and thermal stability. this work describes the synthesis of high quality epitaxial thin films and heterostructures of different functional oxides by chemical solution deposition (csd). in combination with molecular beam epitaxy (mbe) these oxides can be epitaxially integrated in silicon. in particular, complex oxide such as perovskites nanostructured thin films are synthetized by using a csd method called polymer assisted deposition (pad) [1,2] supported with the controlled epitaxial growth of srtio3 (sto) buffer layer on si [3]. by this route, la0.7sr0.3mno3 (lsmo) ultrathin films with abrupt interfaces and nanopillared batio3 (bto) on lsmo with good functionalities can be obtained exhibiting a great technological potential. the complementary of physical and chemical deposition techniques may stablish the basis for the development of low cost functional devices compatible with standard microfabrication technologies. [1] q. x. jia et al. nature materials 3, 529 (2004). [2] j. m. vila-fungueiriño et al. acs appl. mat. interfaces 7, 5410 (2015). [3] j. m. vila-fungueiriño et al. front. phys. 3, 38 (2015) materials and devices, vol 2, #1, p 17 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com confinement of organic dyes inside carbon nanotubes a. salvati(1), a. belhboub(1), alvarez (1), r. leparc (1), s. rols (6),p. hermet(1),b. jousselme(3), k. suenaga (4), a. rahmani (5) jl. bantignies (1) (1) laboratoire charles coulomb, university of montpellier, france, (2) institut laue-langevin, grenoble, france, (3) laboratoire d’innovation en chimie des surfaces et nanosciences (licsen), cea saclay, france (4) nanomaterials research institute, aist, tsukuba, japan (5) laboratoire d’etude des matériaux avancés et applications,université moulay ismaïl, morocco (6) institut charles gerhardt montpellier,, university of montpellier, france jean-louis bantignies : jean-louis.bantignies@umontpellier.fr keywords : encapsulation, confinement, nanotube, vibrational spectrocopies, dft opto-electronic properties of single-walled carbon nanotubes can be significantly modified by chromophore confinement into their hollow core. this presentation deals with quaterthiophene derivatives encapsulated into nanotubes displaying different diameter distributions. we show that the supramolecular organizations of the confined chromophores depend on the nanocontainer size. the raman radial breathing mode frequency is monitored by both the number of confined molecules into a nanotube section and the competition between dye/dye and dye/tube wall interactions. the confinement properties lead also to an exaltation of the infrared absorption response1 in single-walled carbon nanotubes from dye molecule interactions due to a symmetry breaking, allowing us, thanks to the complementarity of dft calculations and experimental ir investigations to study interactions between both subsystems. significant electron transfer from the confined molecules to the nanotubes is also reported from raman investigations. this charge transfer leads to an important enhancement of the photoluminescence intensity by a factor of nearly five depending on the tube diameter. in addition, close to the molecule resonance, the magnitude of the raman g-band shifts is modified and the intensity loss is amplified, indicating a photo-induced electron transfer. results are discussed in the frame of electron-phonon coupling. thus, confinement species into nanotubes allow moving the fermi level and consequently to monitor their opto-electronic properties. reference 1. a. belhboub et al., j. phys. chem. c (2016) 120, 28802-28807. materials and devices, vol 2, #1, p 18 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com electrostriction and giant permittivity of polymer nanocomposites j. yuan, a. luna, a. colin, c. zakri, w. nerin, p. poulin (1) centre de recherche paul pascal – cnrs, university of bordeaux, 115 avenue schweitzer, 33600 pessac, france corresponding author : poulin@crpp-bordeaux.cnrs.fr keywords : nanocomposites, polymer, dielectric, electrostriction, energy harvesting the inclusion of conductive particles into insulating polymer matrices allows the synthesis of nanocomposites with tunable dielectric properties. in particular, giant permittivity is achieved when the conductive inclusions form near percolated networks. the permittivity of such nanocomposites strongly varies when the soft polymer matrix is deformed, giving rise to large electrostriction coefficients as needed in variable capacitors of energy harvesting devices. near percolated networks can easily be obtained with particles of anisotropic shape, such as carbon nanotubes, metal nanowires or graphene platelets. because of their large aspect ratio, the particles exhibit a large excluded volume and a resultant low percolation threshold compared to spherical or quasi-spherical particles. the control of the spatial organization of the particles in the matrix is critical for the control of the material dielectric properties. we will present recent approaches to control the ordering of carbon nanotubes using emulsion templates to obtain enhanced dielectric permittivity and electrostriction coefficients [1]. we will also discuss differences or rod like particles from graphene platelets with giant anisotropy. the percolation behavior of graphene platelets has been recently predicted to be far more complicated than generally anticipated by excluded volume concepts [2]. here, by characterizing the percolation transition in a liquid crystalline graphene based elastomer composite, we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals (lcs) at concentrations below the percolation threshold [3]. we find that the competition of percolation and lc transition provides a new route towards high-permittivity materials. near-percolated liquid crystalline graphene based composites display a giant permittivity along with a low loss tangent. the near percolated nanocomposites exhibit large permittivity variations in response to small strain deformations, giving rise to a giant electrostriction coefficients of about m= -5×10-14 m2/v2 at 100 hz. the present materials are promising for uses in variable capacitors of energy harvesters. their implementation in actual electronic devices is currently investigated. [1] luna, a., yuan, j., neri, w., zakri, c., poulin, p. and colin, a., (2015) giant permittivity polymer nanocomposites obtained by curing a direct emulsion. langmuir 31: 12231-12239. [2] mathew, m.; schilling, t.; oettel, m., phys. rev. e 2012, 85 (6), 061407. [3] graphene liquid crystal retarded percolation for high permittivity materials , j. yuan, a. luna, w. neri, c. zakri, t. schilling, a. colin, p. poulin , nat. comm. (2015) 6, 8700. materials and devices, vol 2, #1, p 19 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com structural optimization and stability study of a yellow-to-transmissive poly(prodotcarbazole) conjugated polymer clément ernest (1), xavier sallenave (1), pierre-henri aubert (1), frédéric vidal (1), claude chevrot (1) (1) laboratoire de physicochimie des polymères et interfaces (lppi, ea 2528), université de cergy-pontoise, 5 mail gay lussac 95031 cergy pontoise cedex, france corresponding author: clément ernest, clement.ernest@u-cergy.fr keywords : conducting polymer, conjugated polymer, electrochromic polymer most of pi-conjugated polymers are colorful in their neutral state, i.e. they show characteristic absorption in the visible part of the light spectrum (400-800nm). however, once pdoped (or oxidized), the absorbance spectrum of pi-conjugated polymers shifts to higher wavelengths values (infra-red domain) and so, become colorless [1]. among the accessible colors in the visible palette, getting polymers with yellow colors in the neutral state is more specific. indeed, one absorption peak centered on 450 nm is needed to obtain this kind of yellow electrochromic material. thus, we have synthesized, a conjugated polymer according to the procedure described in the literature as suzuki polycondensation to yield a yellow-to transmissive switching electrochromic polymer [1,2]. this polymer is based on alterned propylenedioxythiophene (prodot) and 2,7-carbazole (cbz) units as described in figure 1. since this polymer is soluble in common organic solvents, it could be deposited on various conductive substrates by spraycasting method on ito glass. thus, the optoelectronic properties have been characterized using uv/vis spectroscopy, spectrocolorimetry, differential pulse voltammetry (colorimetric study while different potentials were applied), and spectroelectrochemistry. the study shows that this polymer displays vibrantly yellow-colored neutral and a transmissive light-grey oxidized state. these prodot-cbz studies have allowed us to evidence some good colorimetric characteristics as l* values above 85, a* values around −18, and b* values around 80 (the color was assessed by utilizing the cie 1976 l*a*b* color space), these values match with a bright yellow. furthermore, this study allows us to highlight some issues, notably we have carefully studied the cyclability and aging of the prodotcbz polymer upon electrochemistry cycling. modelling based on monomers and trimers with b3lyp and td-b3lyp have also been carried out in order to be able to explain the different phenomena that have been observed during the optoelectronic characterization. figure1: prodot-cbz polymer [1] beaujuge p.m. et al., macromolecules, 42(11): p. 3694-3706 (2009) [2] kerszulis j.a et al., macromolecules, 47(16): p. 5462-5469 (2014) materials and devices, vol 2, #1, p 20 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com materials modelling from ab-initio to thermodynamic properties j. n. gonçalves (1), a. s. fenta (2, 3), c. o. amorim (4), n. m. fortunato (5), j. s. amaral (6) and v. s amaral (7) (1) ciceco and physics department, university of aveiro, portugal, joaonsg@ua.pt (2) ciceco and physics department, university of aveiro, portugal, fenta@ua.pt (3) ku leuven, instituut voor kernen stralingsfysica, belgium, abel.silvafenta@kuleuven.be (4) ciceco and physics department, university of aveiro, portugal, amorim5@ua.pt (5) ciceco and physics department, university of aveiro, portugal, fortunato@ua.pt (6) ciceco and physics department, university of aveiro, portugal, jamaral@ua.pt (7) ciceco and physics department, university of aveiro, portugal, vamaral@ua.pt @ua.pt corresponding author: joaonsg@ua.pt keywords : multiferroic; magnetocaloric; graphene; functionalized nanoparticles computational materials modelling is a fundamental tool to perform structure research, materials properties prediction and design, and to assist the interpretation of experimental data. the multi-scale range of studies covers sub-atomic ab-initio electronic structure methods (density functional theory-dft) up to macroscopic thermodynamic properties. our group at physics department and ciceco is conducting research on developing and applying computational methods to materials science studies, covering a broad range of situations:  multiferroic materials (magnetic and dielectrics): use of dft to study role of local charge and spin distribution on magnetoelectric coupling and hyperfine properties (magnetic field and electric field gradient)  magnetocaloric materials: dft calculation of magnetic exchange interaction under strain, monte-carlo statistical physics methods and mean-field approaches to predict magnetocaloric materials performance in metals, alloys, and oxides  hydration layer and ad-atoms on graphene, their bonding, magnetic and hyperfine properties  local coordination of heavy ions adsorbed on functionalized nanoparticles we will present some cases where the computational studies were closely related to current experimental work within the group and collaborations. materials and devices, vol 2, #1, p 21 (2017) – doi: 10.23647/ca.md20170407 mailto:joaonsg@ua.pt first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com advanced high temperature materials for space and energy applications m. balat-pichelin procédés, matériaux et energie solaire, promes-cnrs laboratory, font-romeu odeillo, france, marianne.balat@promes.cnrs.fr corresponding author : marianne.balat@promes.cnrs.fr keywords : high temperature, oxidation, emissivity, ceramics, refractory alloys the development of advanced materials – ceramics and refractory metals and alloys – that can withstand high temperatures is increasing as many applications can be encountered particularly in the space and energy fields. concentrated solar energy is a useful tool to get very high temperatures in a few seconds in reactors under controlled atmospheres that can reproduce severe environments. in this presentation, some examples will be given for space applications with the behavior of heat shields of spacecrafts during their atmospheric reentry such as the ixv one (intermediate experimental vehicle, esa) which was successfully launched and recovered on february 2015, of the solar probe plus mission (nasa) that will be launched in 2018, and the problem of space debris with the application of the french law los (loi sur les opérations spatiales) mandatory by 2021 will be also presented. in the field of energy, new ultra high temperature ceramics (uhtc) and coating layers on refractory alloys are under study to be implemented for the receivers of future solar power plants for electricity production in order to increase the temperature of the coolant (air at high pressure) and thus the efficiency. the experimental reactors coupled to solar furnace facilities such as rehpts and mesox (fig. 1) at the 6 kw solar furnace, and mediase (fig. 2) at the 1000 kw solar furnace will be presented together with recent original results on oxidation kinetics in air plasma conditions, behavior of materials in high vacuum, emissivity measurement at high temperature… according to the different environments encountered by the selected materials. fig. 1 : mesox faclity at the 6 kw odeillo solar furnace fig. 2 : mediase at the 1000 kw odeillo solar furnace materials and devices, vol 2, #1, p 22 (2017) – doi: 10.23647/ca.md20170407 mailto:marianne.balat@promes.cnrs.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com zno, what is in? paloma fernández dept. física de materiales, fac. physics, university complutense ciudad universitaria, 28040 madrid, spain corresponding author : arana@ucm.es keywords : zinc oxide, zno, ii-vi compounds, history of materials, semiconductors, wide band gap, exciton, luminescence ii-vi compounds have been present almost from the early days of human civilization. of course the main uses have changed along the time. one of first references to such a compound can be found in marco polo´s. in book of the marvels of the world, chapter xxi, concerning the city of cobinan and the things that are made there. he refers to zinc oxide “…they also prepare both tutia (a thing very good for the eyes) and spodium; and i will tell you the process….”. where the tutia is the arabian name for some zno compounds and spodium is an ancient name for zno obtained by sublimation. much later, xix century we find some references as that of von döbereiner in annalen der physik und physikalische chemie, about the green luminescence of zno, the so called rinmann´s green, and at the end of the same century (1866), sidot published an extensive study on the good properties of blende. the advent of electronic devices and the consequent necessity to have homojunctions of good quality, prevented the massive use of compounds which, typically, cannot be prepared in both p and n type, due to the autocompensation phenomena. in this context iii-v compounds won the match, until the last part of last century, where again the good properties such as wide band gap, high exciton energy or efficient luminescence were required. a particular case in the frame of ii-vi is zno. what are the properties, which make this material so attractive? from phosphors and varistors to nanopiezotronics, we will give an overview of the main applications of this material and the phenomena behind. materials and devices, vol 2, #1, p 23 (2017) – doi: 10.23647/ca.md20170407 mailto:arana@ucm.es first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com biocompatible piezoelectric materials for tissue engineering paula m. vilarinho (1) sebastian zlotnik (1), marisa maltez da costa (1), nathalie barroca( 1), m. helena fernandes (1), sandra vieira (2), m. odete cruz e silva (2), ana colete mauricio (3), brian rodriguez (4) (1) department of materials and ceramic engineering, ciceco – aveiro materials institute, university of aveiro, campus santiago, 3810-193 aveiro, portugal (2)centre for cell biology, health sciences and biology departments, university of aveiro, 3810-193 aveiro, portugal (3) clinicas veterinárias, instituto de ciências biomédicas abel salazar, universidade do porto, porto, portugal (4) school of physics and conway institute of biomolecular and biomedical research, university college dublin, dublin, ireland paula m. vilarinho; paula.vilarinho@ua.pt keywords : piezoelectrics, biomaterials, tissue growth, bone growth this talk is about an alternative approach to the development of the next generation of osteoinductive materials that can repair the body in-situ whilst permitting mobilization. the approach uses piezoelectric biocompatible materials. the annual number of new bone fractures in the eu will rise from 3.5 million in 2010 to 4.5 million in 2025, corresponding to an increase of 28% [1]. factures comprise hip, vertebral, forearm and others. delayed fracture healing and nonunion occurs in up to 5–10% of all fractures [2]. diseases such as arthritis, osteoporosis, tumours, and trauma may originate defects in the skeleton demanding a surgical procedure to replace or restore the lost bone. although the comprehension of bone growth and fracture healing is presently very well advanced, efficacious bone treatments are still timely and of paramount importance. piezoelectrics are materials that can create electricity when subjected to a mechanical stress and reversely, generating a strain by the application of an electric field. piezoelectrics find a wide range of applications as sensors, actuators and motors, in the automobile, aeronautics, computer, military, consumers and medical industry. the major medical applications of piezoelectrics include ex-vivo imaging; in-vivo tissue growth applications are seldom, if any. starting from the relatively well known role of electrical stimulation on living tissues and assuming that in-vivo endogenous electric potentials can control cell functions as growth, migration and mitosis rate, in our work we are exploiting the usage of piezoelectrics as smart platforms for biological communication targeted for tissue growth. our current results demonstrate the effect of polarization of biocompatible piezoelectrics (oxides and polymers) on protein adsorption and cells adhesion viability and proliferation. [1] international osteoporosis foundation (iof), facts and statistics, 2017. [2] bone healing in 2016, john a. buza, iii and thomas einhorn, clin cases miner bone metab., 13 (2), 101 – 105, 2016, doi: 10.11138/ccmbm/2016.13.2.101 materials and devices, vol 2, #1, p 24 (2017) – doi: 10.23647/ca.md20170407 mailto:paula.vilarinho@ua.pt first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com bottom-up approach to epitaxial functional oxide nanostructures and nanocomposite thin films x. obradors, t. puig, m. coll, j. gázquez, a. palau, s. ricart, n. mestres, a. queraltó, p. cayado, r. guzmán, z. li, j. c. gonzález, b. mundet, j. jareño, l. soler, c. pop, b. villarejo, n. f. pino, n. chamorro, p. machado, j. banchewski, m. tristany, a. pérez del pino, e. bartolomé institut de ciència de materials de barcelona-csic, campus uab, 08193 bellaterra, catalonia, spain corresponding author : xavier.obradors@icmab.es keywords : thin films, chemical solution deposition, superconductors, epitaxy, ferromagnetism complex oxides are a large arena of functional materials where quantum effects are becoming the main source of unique properties and functionalities. to fully exploit these novel opportunities a deep understanding of the growth mechanisms of ultrathin films, nanostructures and nanocomposites is required, as well as a detailed comprehension of atomic scale structure and its correlation with electronic states and functionalities. generation of large area arrays of self-organized oxide nanostructures (nanodots, nanowires) and large area thin and ultrathin films and nanocomposites provides unique opportunities for the development of novel functionalities with a wide range of potential applications (superconducting, electronic, magnetic, ferroelectrics, photovoltaics, resistive switching, etc.). bottom-up approach based on chemical solution deposition (csd) offers a high throughput (ink jet printing) and cost-effective route for the generation of complex oxide thin films, multilayers and nanocomposite films while atomic layer deposition (ald) is very effective in modifying the interfacial properties or to grow ultrathin films at low temperatures. in this talk i will review recent developments in the understanding of the growth mechanisms of epitaxial oxides derived from chemical solutions when conventional thermal annealing (cta), rapid thermal annealing (rta), pulsed laser annealing (pla) or transient liquid assisted growth (tlag) are used. i will also show that csd and ald can be combined to prepare oxide multilayers with modified functionalities. the systems investigated include the ionic conductor ce1-xgdxo2, ferromagnetic-metallic perovskites (la1-xsrxmno3), perovskites with metalinsulator transitions (renio3), ferroelectrics (batio3), multiferroics (bifeo3) or yba2cu3o7 derived nanocomposite high temperature superconductors. some outstanding properties of these complex oxides are found to be linked to the nanoscale strain and complex atomic defects deciphered by hrtem and xmcd. i will stress that to fully develop the strong potential of bottom-up approaches to complex functional materials the growth mechanisms need to be fully disentangled to achieve control of the relevant properties. materials and devices, vol 2, #1, p 25 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com lead-free ferroelectric and multiferroic systems from the aurivillius family a. peláiz-barranco (1), y. gonzález-abreu (1), j.d.s. guerra (2), p. saint-grégoire (3), y. gagou (4), a. rivas-gutiérrez (1), j. falohgandarilla (1), s. díaz-castañón (5). (1) facultad de física-instituto de ciencia y tecnología de materiales, universidad de la habana. san lázaro y l, vedado. la habana 10400, cuba. (2) grupo de ferroelétricos e materiais multifuncionais, instituto de física, universidade federal de uberlândia. 38408-100, uberlândia – mg, brazil. (3) mipa laboratory, universities of toulon and nîmes, 30021 nimes cedex 01, france. (4) university of picardie jules verne, lpmc, 80039 amiens cedex, france. (5) división de materiales avanzados, instituto potosino de investigación científica san luis potosí, c.p. 78216, méxico. corresponding author: pelaiz@fisica.uh.cu keywords: ferroelectrics, multiferroics, ceramics over the last 20 years there has been an enormous effort in developing lead-free ferroelectric systems in order to obtain good dielectric, ferroelectric and piezoelectric properties than those the conventional ferroelectrics based on lead, such as pzt. the ferroic group materials of the physics faculty, havana university, cuba, has been working since 1983 in the study of ferroelectric and piezoelectric materials, especially modified pzt and pt. an important group of lead-free ferroelectric materials belong to the aurivillius family, compounds which are layered bismuth [bi2o2]2+[an−1bno3n+1]2− (see figure). srbi2nb2o9 is a member of this family where the divalent sr2+ cation can be totally or partially replaced by other cations, most commonly ba2+. a few years ago, we have begun to work on sr1-xbaxbi2nb2o9 lead-free ferroelectric materials. the barium concentration dependence of the dielectric behavior has suggested a cation site mixing among atomic positions, which has been supported by the structural analysis. a transition from normal ferroelectric-paraelectric phase transition to a relaxor behavior has been observed when the barium concentration has increased. for the sr0.70ba0.30bi2nb2o9 composition has been obtained the better piezoelectric, pyroelectric and ferroelectric properties. ferroelectric thin films have been also obtained for sr0.70ba0.30bi2nb2o9 and sr0.15ba0.85bi2nb2o9 compositions. on the other hand, the aurivillius family systems are potential candidates as multiferroics by doping magnetic elements at the b-site. a magneto-electric four-layered structure (bi5feti3o15) can be obtained by inserting bifeo3 into bi4ti3o12, a classical three layers perovskite. bi4.2ln0.8fe0.5co0.5ti3o15 (ln3+ = la3+, pr3+, nd3+) multiferroic ceramics have been studied. the ln3+ elements have showed an important influence on the characteristic magnetic hysteresis. the presentation will show a general overview of our researches on lead-free ferroelectric and multiferroic systems from the aurivillius family. figures : crystal structure of aurivillius type with m=2 (upper, right) ; magnetic hysteresis loop in a multiferroic aurivillius type material (bottom, left). materials and devices, vol 2, #1, p 26 (2017) – doi: 10.23647/ca.md20170407 mailto:pelaiz@fisica.uh.cu first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com advanced electrode materials for lithium and post-lithium batteries r. berthelot, n. louvain, m. sougrati, l. stievano and l. monconduit institut charles gerhardt de montpellier (umr5253) equipe “agrégats interfaces et matériaux pour l’energie” université de montpellier, 2, place bataillon cc1502 – 34095 montpellier corresponding author : romain.berthelot@umontpellier.fr keywords : battery electrode, post-lithium, ball-milling, operando characterization in less than fifty years, lithium-ion batteries shifted from scientific discoveries to rapid industrial prototypes, before flooding the market of the electrochemical energy storage. this exceptional achievement escorted the huge explosion of electronical mobile tools such as cell phones, tablets or portable computers. now lithium-ion batteries also equip hybrid or full electric vehicles and are also considered for grid storage. the lithium-ion technology is mature but there is still room for performance improvements. this can be done by protecting the surface of standardized electrode materials through chemical coating and hence prolonging the life of such batteries. this can also be done by investigating innovative electrode materials. in case of lithium becomes a strategical element, it is also important to investigate post-lithium electrochemical storage systems, such as sodium-ion or magnesiumbased batteries.in this presentation, we will summarize very recent results and ongoing research projects that we carry out at “institut charles gerhardt de montpellier”. after a general introduction that will deal with the concept of rechargeable batteries and the electrode materials requirements, different examples of new materials for li-, na-, or mg-ion batteries will be presented. it embraces the synthesis procedures that may strongly influence the final morphology of the active materials, and the optimization of the electrode formulation to enhance the electrochemical performance (specific capacity, lifetime, etc.) for some electrode materials that are investigated for a long time and already implemented in commercialized cells, the optimization of the electrochemical performance is still possible, for example by protecting the particle by a fluorinated shell that can help in reducing the solidelectrolyte interphase and thus accessing extra capacity. the understanding of the electrochemical process (ion insertion and de-insertion) is possible by performing operando characterizations, like x-ray diffraction, mössbauer or x-ray absorption spectroscopies. depending on the chemical nature of the electro-active materials, the electrochemical process might be a reversible intercalation of the cations or can undergo an alloying mechanism with new phases created. the deep investigation of the electrochemical mechanisms that occurs during the battery life may also help in evidencing the failure process. materials and devices, vol 2, #1, p 27 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com nano-crystallization in decorative layers of ancient ceramics ph. sciau, a. pinto, m. brunet, j. groenen, c. brouca-cabarrecq cemes-cnrs, université de toulouse, france corresponding author : philippe.sciau@cemes.fr keywords : cultural heritage material, ancient ceramic, metallic lustre decorations of glazed ceramics, which appeared in mesopotamia during the 9th century ad, are certainly the most famous historical example of controlled nanotechnology for optical devices [1]. yet, the use of optical properties of metallic particles is older. actually, the tinting strength of metallic nano-crystal was used earlier for colouring glasses. it was shown that red glasses of final bronze age (1200-1000 bc) from frattesina di rovigo in italy were coloured thanks to crystalline particles of metallic copper dispersed in the surface layer of glassy matrix [2]. many other examples can be found in literature showing that this glass staining process was widely used worldwide up to present times. thus, the presence of both copper and cuprite particles was reported in celtic enamels. most of the roman tesserae of red colour were obtained from a glass containing copper nano-crystal. these tesserae were produced massively during the roman period thanks to a scale production of glass ingots. outside europe and mediterranean basin, copper nanoparticles for colouring glasses and glazes were also massively used in asia. for instance, the colouring of japanese satsuma glasses was obtained in this way. the blue-red jun glazed porcelains made from song to qing chinese dynasties were manufactured using a similar process leading to the formation of copper nano-crystals in the red zones during firing. it is also the case for some vietnamese porcelains and stonewares. beside metallic nano-crystals exploited for their optical properties, many other nanoscale crystals can be found in ancient ceramics and more specifically in their decorative or coating layers. these crystals can play a major role in the physical properties of these thin layers or merely be an indicator of the manufacturing process. these thin layers are formed during firing and result from physicochemical reactions among the diverse compounds of raw preparation. in general, the firing conditions are not suitable for obtaining large crystals and many of formed phases are in the form of nano or submicrometric crystals. over time and in other places around the world, the variety of raw preparations and firing conditions used are so diverse that it is not conceivable to give here an exhaustive report. in this presentation, we will focus our attention on decorative layers of greek and roman potteries for which oxide nano-crystals play a key role in the optical and/or mechanical properties [3]. we will present also some glazed decorations of chinese ceramics in which some rare and interesting phases for modern applications were found [4]. [1] ph. sciau, in the delivery of nanoparticles, edited by a. a. hashim (intech, 2012), pp. 525. [2] i. angelini et al., j. archaeol. sci. 31 (8), 1175 (2004). [3] ph. sciau. in nanoscience and cultural heritage (philippe dillmman, ludovic bellot-gurlet and irène nenner (ed.), atlantis press, 2016, isbn 978-94-6239-197-0), pp. 41. [4] c. dejoie et al. (2014). sci. rep. 4, 4941 (doi:10.1038/srep04941). materials and devices, vol 2, #1, p 28 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com long period modulated structures in trigonal double molybdates and tungstates m. b. zapart, w. zapart institute of physics,technical university of czestochowa, poland corresponding author : zapart@wip.pcz.pl keywords : ferroelastics, modulated structures, order parameter. double molybdates and tungstates with the general formula mr(xo 4)2 (m=an alkali metal li-cs, ag or monovalent tl-ion, r= a rare earth element, bi, in, sc, ga, al, fe, cr, x=mo,w) are well known in the literature. the structural diversity in these compounds reflects in a wide variety of physical properties. they may be considered as ferroelectric and ferroelastics, solid-state electrolytes , optical materials, phosphor and laser-host materials. some double molybdates and tungstates having a trigonal symmetry p-3m1 of the crystal structure exhibit interesting sequences of ferroelastic phase transitions. also an existence of the incommensurate phases was reported in a few crystals belonging to this family, namely ksc(moo4)2, rbin(moo4)2, ksc(wo4)2. a group-theoretical analysis of possible transitions in the tdm/t compounds has shown that they lead either to monoclinic or triclinic systems and are induced by one of the two-dimensional irreducible representations of the space group, τ5 or τ6. the transition from the trigonal to monoclinic phases is improper one and is accompanied by a doubling of the unit cell along the threefold axis of the crystal, onset of spontaneous strain and nucleation of ferroelastic domains. however the above approach cannot account for the simultaneous existence of the ferroelastic and incommensurate phases in these crystals. in order to explain such coexistence, the coupling of two order parameters η and ζ was considered, responsible for doubling the size of the unit cell and the long period modulation of the crystal structure, respectively. such an interaction of both parameters could lead to a variety of transitions, also to dimmock's phases where both, long and short period modulated phases coexist. experimental examples of such phases, derived from the observation of tdm / t crystals in polarized light and the electron paramagnetic resonance studies, were also provided. materials and devices, vol 2, #1, p 29 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com electrocaloric measurements in leadfree materials b. asbani1,2 a), j.-l. dellis1, y. gagou1, a. lahmar1, m. amjoud2, m. trček3, z. kutnjak3, d. mezzane2 and m. el marssi1, 1 lpmc, université de picardie jules verne, 33 rue saint-leu, 80039 amiens cédex, france 2 lmcn, f.s.t.g. université cadi ayyad, bp 549, marrakech, morocco 3 jozef stefan institute, jamova cesta 39, 1000 ljubljana, slovenia corresponding author : bouchra.asbani@cnrs-imn.fr keywords : electrocaloric effect, lead-free, pyroelectric coefficient, ba0.8ca0.2tio3 ceramics the electrocaloric (ece) effect was investigated in lead-free doped ba0.8ca0.2tio3 ceramics synthesized by a conventional sintering process. all analyzed ceramics exhibit tetragonal structure. the dielectric spectroscopy and calorimetry revealed that the curie temperature decreases as a consequence of elements doping and that the ceramics exhibits a first order ferroelectric phase transition. direct measurements using high resolution calorimetry were compared to the two indirect measurements using the maxwell relationship. in a first well-known indirect method, p-e hysteresis loops were measured in a wide temperature range and pyroelectric coefficient and thus the electrocaloric responsivity were determined by derivation of p(t, e) data. in second method the electrocaloric responsivity was determined by direct measurements of the pyroelectric coefficient and consequently the electrocaloric responsivity ξ was determined by direct measurements of the pyroelectric currents under different applied electric fields [1]. good agreement was obtained between different methods and large electrocaloric responsivity was found for some critical compositions around the dielectric maximum [2,3,4]. [1] b. asbani, j-l. dellis, y. gagou, h. kaddoussi, a. lahmar, m. amjoud, d. mezzane, z. kutnjak, m. el marssi epl (europhysics letters) 111, 57008 (2015) [2] b. asbani, j.-l. dellis, a. lahmar, m. courty, m. amjoud, y. gagou, k. djellab, d. mezzane, z. kutnjak, m. el marssi, applied physics letters 106, 042902 (2015) [3] h. kaddoussi, a. lahmar, y. gagou, b. asbani, j.-l. dellis, g. cordoyiannis, b. allouche, h. khemakhem, z. kutnjak, m. el marssi, journal of alloys and compounds, 667, 198 (2016) [4] b asbani, y gagou, j-l dellis, a lahmar, m amjoud, d mezzane, z kutnjak, solid state communications, 237– 238, p 49–54 (2016) materials and devices, vol 2, #1, p 30 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com effect of ce and la on the corrosion layer of new alloys zn-re khadoudj guessoum (1), delphine veys-renaux(2), emmanuel rocca(2), kamel belhamel(1) (1) laboratoire des matériaux organiques, département de génie des procédés, faculté de technologie, université de béjaia, béjaia 06000, algeria (2) institut jean lamour-umr cnrs 7198, université de lorraine-cnrs, bp 70239, vandoeuvre-lès-nancy 54506, france corresponding author : gueksabrina05@yahoo.fr keywords : rare earth, corrosion, alloys, cerium new zn-re1-5 wt.% alloys (re=ce and la) were synthesized by melting under controlled atmosphere and cast in plates. in these materials, rare earth metal are exclusively present in intermetallic phases homogeneously dispersed in the zinc matrix: zn11ce, zn13la. the electrochemical behavior of these new alloys was investigated in a reference corrosive medium. in parallel, the pure intermetallic phases zn11ce and zn13la were synthesized and their electrochemical influence was studied by voltametry and galvanic coupling. from results of controlled precipitation experiments of cerium and zinc salts performed in carbonated medium, the presence of cerium in the corrosion layer and its protective character could be attributed to the formation of a mixed double lamellar zinc-cerium product. therefore, addition to zinc of less than 2 wt.% of cerium or lanthanum allow to improve the corrosion resistance of zinc. cross-section corrosion layer of zn-ce2 wt.% immersed 30 days in astm water: bse image (a) and corresponding wds x-cartography of ce (b); drx pattern of a mixed double lamellar product (c) . materials and devices, vol 2, #1, p 31 (2017) – doi: 10.23647/ca.md20170407 mailto:gueksabrina05@yahoo.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com synthesis of cu2zns3 wurtzite by sol–gel process influence of preparation temperature m. hamici (1) and p.saint-grégoire (2). (1) dac-hr laboratory, sétif -1,university, algeria (2) mipa laboratory, universities of toulon and nîmes, france corresponding author : hemissi_melia@yahoo.fr. keywords : czt, x-ray diffraction, meb, semi-conductor, wurzite. cu2zns3 (czs) is certainly one of the most promising materials for photovoltaics. it has a direct band gap that may be tuned between 1.4 and 1.6 ev, and a high absorption coefficient over 104 cm−1. moreover, the fact that it is composed of earth abundant and non-toxic constituents, and that its synthesis does not involve a polluting or energy consuming process, makes this compound an environment friendly one. in the present study, the wurtzite czs material has been prepared by a sol–gel route. the czs samples have been characterized structurally by x-ray diffraction (xrd), morphologically by scanning electron microscopy (sem) and optically using a uv-vis spectrophotometer. the compound appears to be more stable than the quaternary czts (cu2znsns4), also considered promising for photovoltaics. sem studies reveal that the morphology of the obtained materials – powders or films – depends strongly on the annealing temperature and crystallization process. the structure of films may include agglomerated nanocrystals or intricated fibers, among others (see figures). the study of optical absorption reveals a band gap around 1.55 ev, suitable for photovoltaic applications. sem images of cu2zns3 thin layer a) as-grown, and b) after a sharp heating at 400°c during drying materials and devices, vol 2, #1, p 32 (2017) – doi: 10.23647/ca.md20170407 a b first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com oxidation process of in2s3 crystalline powder m. hamici (1), l. vaillant (2), and p. saint-grégoire (3) (1) dac-hr laboratory, sétif -1,university, algeria, hemissi_melia@yahoo.fr (2) enermat division, institute for science & technology of materials (imre), university of havana, zapata esg g, s/n, 10400 cuba (3) mipa laboratory, toulon and nimes universities, france, pstgregoire@gmail.com corresponding author : hemissi_melia@yahoo.fr keywords : in2s3, in2o3, oxidation, photovoltaics, chemical bath, thermal analysis in2s3 is a promising material that has been studied in the last years mainly in reason of its potential interest in solar cells as a cds buffer layer substitute for fabricating cd-free cigs solar cells. in 2s3 films of the crystalline  form may be obtained by chemical bath deposition (cbd), physical vapor deposition (pvd) and by spray pyrolysis. in the literature the oxidation of in2s3 films was described for films obtained by cbd and pvd. some of us showed that the oxidation process depends on the film microstructure : the temperature region in which the oxidation occurs is strongly dependent on the size of crystals in deposited films, and the temperature of annealing in air determines the composition of the solid solution. a potential interest of the intermediate compositions is that the band gap varies as a function of composition and can be tailored to intermediate values between the band gap value for in2s3 and that for in2o3, that should influence the efficiency of solar cells built with the corresponding buffer layer. however on the other hand, such nanostructured thin films are fragil with respect to heating or also to chemical attacks. attempts to deposit p-type semiconducting materials cu2sns3 (cts) and cu2znsns4 (czts) on in2s3 thin films, with a penetration of the ptype semiconductors, are made difficult because of chemical instability of the in2s3 film in the corresponding baths. this situation motivated us to investigate the possibility to obtain in 2s3 films by dr blade technique, and to study carefully the behaviour of such films and constitutive crystalline powders, that have grains with a micrometric size as evidenced in the sem, to be compared with results obtained with nanometric powders resulting from thin films as studied recently. in this communication we present first the films obtained by dr blade, and then results of tga that show weight losses in nitrogen that correspond to elimination of solvents, and thereafter weight losses in air, accompanying the substitution of sulphur by oxygen in the structure. this mechanism is confirmed by analyses performed by edx and the obtained materials are also studied by x-ray diffraction (xrd). the variation of bandgap of the obtained materials of different compositions is deduced from uv-visible spectrometry data. figure 1: sem micrograph of in2s3 powder figure 2: weight loss versus temperature in air atmosphere (tga measurement) materials and devices, vol 2, #1, p 33 (2017) – doi: 10.23647/ca.md20170407 400 500 600 7,6 7,8 8,0 8,2 8,4 8,6 8,8 9,0 d er iv . w ei g h t (% ) in it ia l w ei g h t m = 8 .8 5 7 0 m g w ei g h t (m g ) temperature °c -0,20 -0,15 -0,10 -0,05 0,00 mailto:hemissi_melia@yahoo.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com 3d-fib characterization of the martensitic transformation on shot peened metastable steels g. fargas, j.j. roa, a. mateo ciefma departament de ciència dels materials i enginyeria metal·lúrgica, eebe-universitat politècnica de catalunya, barcelona corresponding author: antonio.manuel.mateo@upc.edu keywords: focus ion beam (fib), shot peening, metastable steels, martensite metastable austenitic stainless steels can be considered as trip (transformation induced plasticity) steels because plastic deformation leads to transformation from austenite to martensite. on the other hand, during service life of a component manufactured with these steels, fatigue failure may occur. therefore, shot peening could be used to increase their fatigue resistance. despite numerous investigations have shown the beneficial effects of shot peening on austenitic stainless steels, scarce information exists related to metastable grades. in the present work, the relationship between microstructural changes induced by shot peening and fatigue behavior of a commercial aisi 301 ln (corresponding to standard en 1.4318) metastable steel was studied. two different steel conditions were selected: annealed (with fully austenitic microstructure) and cold rolled (with a biphasic microstructure composed by austenite and martensite). the deformed microstructure on the subsurface was analyzed on cross-section specimens through the shot peened region by means of 3d-fib (focus ion beam) tomography collecting around 400 sequential images milled with a ga+ ion beam current. results pointed out that extensive plastic deformation and phase transformation developed in annealed specimens as a consequence of shot peening. however, the increase of roughness and the generation of microcracks led to a limited fatigue limit improvement. in contrast, shot peened cold rolled specimens exhibited enhanced fatigue limit. in the latter case, the main factor that determined the influence on the fatigue response was the distance from the injector, followed by the exit speed of the shots and the coverage factor. materials and devices, vol 2, #1, p 34 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com synthesis of co doped zno thin films by sol-gel n. lameche (1), m.hemici (2) (1) applied optics laboratory , university of setif1-algeria,norelhouda_l@yahoo.fr (2) dosage, analysis and characterization laboratory, university of setif1-algeria , hemissi_melia@yahoo.fr corresponding author : norelhouda_l@yahoo.fr keywords : cobalt doped zno, dip coating, thin films, optical constants in the present work, zno and co:zno thin_films with different percentage of cobalt content were deposited by dip_coating technique. the sol has been prepared by reacting zinc acetate and cobalt (ii) nitrate in 2-propanol alcohol. the effect of cobalt doping concentration on the structural, optical, morphological proprieties of zno thin_films was investigated. the wurtzite structure was observed in all deposited films and the presence of zinc, oxygen and cobalt was confirmed by using edx analysis. the optical constants (refraction index, absorption, extinction and dielectric constants) were found to depend on the cobalt content. the band_gap energy decreased from 3.26 to 3.20 ev with increasing cobalt concentration. cobalt effect modified the surface morphology of zno thin_films. rms roughness and crystallite size decreased when co doping increases from 0 to 8at.%. fig.1: spectral dependences of refractive index (n) of the undoped and co-doped zno thin films fig. 2 : afm images of undoped and co-doped zno thin films materials and devices, vol 2, #1, p 35 (2017) – doi: 10.23647/ca.md20170407 mailto:norelhouda_l@yahoo.fr first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com ferroic systems: the cuban experience a. peláiz-barranco, f. calderón-piñar, o. garcía-zaldívar, y. gonzálezabreu, y. mendez-gonzález, y. garcía-puente physics facultyinstitute of science and technology of materials, havana university, san lázaro y l, vedado. la habana 10400, cuba. corresponding author: pelaiz@fisica.uh.cu keywords : ferroelectrics, antiferroelectrics, multiferroics, ceramics the research′s group on “ferroic materials” of the physics facultyinstitute of science and technology of materials, havana university, cuba, was founded in 1983 (named before “ferroelectrics group”). the first researches were realized for search of high efficiency of piezoelectric energy conversion and low dielectric loss for ultrasonic generation. today, the main research topics are about ferroelectric, antiferroelectric and multiferroic systems. ceramics systems of high quality have been obtained for several years. thin films and composites have been also obtained. structural, dielectric, piezoelectric, pyroelectric, ferroelectric and magnetic analyzes have been carried out in a wide variety of systems such as pbtio 3, pb(ti,zr)o3, pb(zn1/3nb2/3)-pbtio3-batio3, srbi2nb2o9, (bi0.5na0.5)tio3-batio3, bifeo3, bife0.5co0.5ti3o15, and others, included several modifications of them. ferroelectric phase transitions, relaxor behavior, dielectric relaxation and electrical conductivity, thermally stimulated processes and pyroelectricity, ferroelectric-antiferroelectric coexistence, ferroelectric-ferrimagnetic coexistence, electrocaloric effect and energy storage are some of the most important developed topics. the presentation will show a general overview of the group, the principal topics and results, the main scientific collaborations, etc. materials and devices, vol 2, #1, p 36 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com x-ray absorption spectroscopies in correlated oxides and advanced materials a. y. ramos (1,2), s. grenier(1,2), a. bailly (1,2), y. joly (1,2) (1) univ. grenoble alpes, inst neel, f-38000 grenoble, france (2) cnrs, inst neel, f-38000 grenoble, france corresponding author : aline.ramos@neel.cnrs.fr keywords : xas, herfd-xanes, rexs, oxide we study the correlations between structural and electronic properties in a wide set of solid compounds ranging from 3d bulk materials, thin films at the 2d limit, down to 1d nanoparticles. our common tools are related to x-ray absorption spectroscopy (xas) and resonant x-ray scattering (rexs) with large applications in correlated oxides and developments of these technics and analysis tools. xas allows to probe the valence and structure of the coordination shells for a target chemical element. in the so called herfd mode, the specific emission lines (k, kβ1,3, kβ2,5..) of the absorbing element are independently collected using crystal analyzer spectrometer. this significantly improves x-ray absorption near edge structure (xanes) features and the counting statistics, but also gives access to spin, redox and ligand sensitivity. surface-rexs couples of the capabilities of surface diffraction and resonant scattering for the investigations of electronic structure in ultrathin films and at surfaces. our measurements carried out at the french collaborating research group beamlines at the esrf, and the analysis is based on ab initio simulations in a mono-electronic approach using the advanced fdmnes code. (a) (b) (c) (d) (a) emergence of ferromagnetism in cr doped lamno3 by xanes and xmcd ; (b) pressure induced insulator to metal transition in lamno3 from xanes in the pre-edge range ; (c) charge order in 7nm fe3o4 film by srexs, (d) platinum-sub nanoparticle catalysts by herdf xanes. we present some studies carried out in our group, with focus on xas study in perovskite oxides and recent results of herdf-xanes and sxrs in ultrathin magnetite films and pt nanoclusters. materials and devices, vol 2, #1, p 37 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com nano-x: a toulouse based platform dedicated to materials characterization using x-ray scattering techniques n. ratel-ramond (1), l. vendier (2), g. viau (3), b. malard (4) (1) cemes-cnrs, toulouse, france, nicolas.ratel-ramond@cemes.fr (2) lcc, cnrs toulouse, france, laure.vendier@lcc-toulouse.fr (3) lpcno, insa toulouse, france, gviau@insa-toulouse.fr (4) cirimat, inpt ensiacet, france, benoit.malard@ensiacet.fr corresponding author : nicolas.ratel-ramond@cemes.fr keywords : x-ray diffraction, x-ray scattering, technical platform the nano-x platform is a tool dedicated to the characterization of nanomaterials using x-ray scattering and diffraction techniques. this project was initiated in 2013 and is supported by 4 laboratories based in toulouse (cemes, cirimat, lcc and lpcno). the nano-x platform is geographically based in the 4 constituting laboratories, who aim to maintain and develop x-ray techniques at a competitive level. the instrument pool is constituted of 6 equipment dedicated to x-ray diffraction and scattering techniques, including single crystal x-ray diffraction, powder diffraction, high resolution x-ray diffraction, wide angle x-ray scattering, microdiffraction and various sample environments for in-situ investigations. the equipment available allow the analysis of single crystal specimen, polycristalline bulk sample, thin films and multi layers, as well as powders or amorphous materials, under variable condition of temperature, pressure and atmosphere. the main topics covered by the platform are stress and strain determination, texture measurements, crystal structure, quantitative analysis, sample crystallinity and nanomaterials. the platform is accessible to physicists, chemists, materials scientists and industrial partners. materials and devices, vol 2, #1, p 38 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com laser activation of semiconductor nanostructures for zno nanorods based solar cells y. rodríguez martínez (1), j. a. alba cabañas (2), o. cruzata (3), p. saint-gregoire (4) and l. vaillant roca (1) (1) photovoltaic research laboratory, enermat division, institute of materials science and technology – physics faculty, university of havana, cuba, yerila@imre.uh.cu (2) physics faculty photovoltaic research laboratory, enermat division, institute of materials science and technology, university of havana, cuba, jalba@estudiantes.fisica.uh.cu (3) laser division, institute of materials science and technology, university of havana, cuba, osmel@imre.uh.cu (4) mipa laboratory, toulon and nimes universities, france, pstgregoire@gmail.com corresponding author : vaillant@imre.uh.cu keywords : zno nanorods, inorganic nanostructured solar cells, laser activacion, seeding, core/shell structures inorganic nanostructured solar cells can combine the stability of inorganic materials with the advantages of the 3 rd generation solar cells architecture. these devices are characterized by an extension of the main junction which is obtained through an incremental roughness of the materials, leading to the creation of embedded or inter penetrated junctions. also, it is important to consider the possibility to exploit the effects of quantum confinement at the nanoscale like carrier multiplication, for achieving better conversion efficiencies. although the conceptual design in this type of solar cells has a tremendous potential, there are huge experimental challenges to be overcome. stability can be addressed by focusing in inorganic semiconductor materials, as mentioned before. in our case, we have chosen the zno nanorods network because of its friendly environmental impact and wide range of applications in solar cells. for using a pulsed laser as a local heat source, we follow two different approaches. in the first one we applied the pulsed laser during the process for creating the nucleation points or seeds, before growing the zno nanorods by the hydrothermal technique. in the second one, we point out to the in-situ fabrication of semiconductor quantum dots on the zno nanorods surfaces, by pulsing the laser at different fluences and pulses number. the results are studied by scanning electron microscopy (sem) and photoluminescence (pl). on the left, scheme of laser activation of the seeds for the zno nanorods. right, in-situ laser induced growth of semiconductor quantum dots on the zno nanorods surfaces. materials and devices, vol 2, #1, p 39 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com dielectric permittivity enhancement and large electrocaloric effect in the lead free (ba0.8ca0.2)1-xla2x/3tio3 ferroelectric ceramics b. asbani1,2, y. gagou1,a, m. trček3, j.-l. dellis1, m. amjoud2, a. lahmar1, d. mezzane2, z. kutnjak3 and m. el marssi1 1lpmc, université de picardie jules verne, 33 rue saint-leu, 80039 amiens cédex, france 2lmcn, f.s.t.g. université cadi ayyad, bp 549, marrakech, morocco 3jozef stefan institute, jamova cesta 39, 1000 ljubljana, slovenia corresponding author : yaovi.gagou@u-picardie.fr keywords : ferroelectric, electrocaloric, lanthanum, dielectric, responsivity lanthanum (la) incorporation in the (ba0.8ca0.2)tio3 (bct) matrix induces enhancement of electrocaloric effect, decrease of curie temperature and increase of dielectric permittivity. we studied the influence of la substitution on electrocaloric effect (ece) in bct matrix using both indirect and direct methods. from ferroelectric polarization and pyroelectric measurements, we calculate ece response versus temperature for all the (ba 0.8ca0.2)1-xla2x/3tio3 (xbctl) ceramics compositions ranging from x = 0 to 0.05. the results showed good agreement between the two methods at the same applied electric field. a maximal value of electrocaloric temperature change t = 0.30 k was obtained at 25 kv/cm corresponding to an ec responsivity  = 0.120×10-6 k m/v, in a wide temperature region in the vicinity of the ferroelectric phase transition temperature (250 k to 400 k) for x=0.05 that places this family as very promising materials for electrocaloric applications near room temperature. dielectric enhancement (left) and electrocaloric temperature change (right) in bclt materials and devices, vol 2, #1, p 40 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com multiferroic thin films and superlattices grown by pld and their caracterisation using ppms technique y. gagou lpmc, university of picardie jules verne, 33 rue saint leu, 80039 amiens cedex corresponding author : yaovi.gagou@u-picardie.fr keywords : multiferroics, pld, ppms technique, epitaxial pulsed laser deposition (pld) is one of the most efficient techniques to produce epitaxial thin films whose crystallographic orientation is well controlled during the growth process. this method is based on the bombardment of a dense ceramic target by a pulsed laser inside a pressure autoclave in which the substrate is prepared to receive the particles of material torn out during the interaction between the target and the laser. in this work we show the experimental procedure of a thin film and a superlattice with optimal conditions of elaboration and the characterization by the means of new equipment available in our laboratory (a lambda physik 248 nm excimer laser in a meca 2000 uhv chamber) to carry out this research theme. the materials studied are thin films of multiferroic oxides whose magnetic and transport properties are obtained by a quantum design's physical properties and magnetic system (ppms) equipment. the first results obtained on thin film and superlattice of perovskite, ttb-type materials and aurivillius phase doped by magnetic metal rare earths (gd, co, fe, mn ...) are discussed in view of the crystallographic aspects and magneto-electric properties. the epitaxial layers are grown on cubic single crystal (001)mgo and (001)sto substrates amgo=4.213 å buffered with an oxide conducting layer of la1/2sr1/2coo3 (lsco), alsco=3.805 å. the tipical thickness is of about 4000 å. the best conditions of syntheses are obtained by varying the deposition temperature (generally around 750 °c) and the oxygen partial pressure (around ~ 0.2 mbar). a deposition rate of 0.40 å/pulse was determined from x-ray thickness and laue oscillations observed on very thin films of materials. the surface quality of the layers are monitored using reflection high-energy electron diffraction (rheed). xrd patterns were recorded using a d8 discover diffractometer with cu k-alpha radiation. from the left to the right: rheed, afm image on gkn/sto, epitaxy on pkn/mgo and fe properties of bt/mgo materials and devices, vol 2, #1, p 41 (2017) – doi: 10.23647/ca.md20170407 first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com energy confinement effects in cdte nanocrystals embedded on zno nanorod matrix s. larramendi (1), l. vaillant (2), p. saint-gregoire (3), j. ferraz dias (4), and m. behar (5) (1) institute of materials science and technology (imre), university of havana, cuba, (2) institute of materials science and technology (imre), university of havana, cuba, vaillant@fisica.uh.cu (3) mipa laboratory, universities of toulon and nimes, france, pstgregoire@gmail.com (4) ion implantation laboratory, institute of physics, federal university of rio grande do sul, brazil, jfdias@if.ufrgs.br (5) ion implantation laboratory, institute of physics, federal university of rio grande do sul, brazil, behar@if.ufrgs.br corresponding author: saull@fisica.uh.cu keywords : low dimensional structures; hydrothermal crystal growth , physical vapor deposition processes, zinc compounds, semiconducting ii-v, solar cells a zno nanorod structure was grown by the hydrothermal method and interpenetrated with cdte using the isothermal closed space sublimation technique [1]. the obtained structure was studied by using the rutherford backscattering spectrometry (rbs), scanning electron microscopy (sem), and high resolution transmission electron microscopy (hrtem). the x-ray diffraction (xrd) technique confirmed the presence of cdte nanocrystals (ncs) of very small size formed on the surface and in the interspaces between the zno nanorods. the rbs observations together with the sem observations give information on the obtained structure. finally the photoluminescence studies show evidence of energy confinement effect in the grown cdte ncs. the obtained structure of vertically-aligned zno nanorods interpenetrated with cdte ncs has some similarity with those structures proposed for excitonic organic solar cells. therefore we propose that the present cdte/zno heterostructure can be a good candidate for an efficient solar cell device. nanocrystals of cdte over zno nanorods superficies grown by isothermal closed space sublimation (a) zno nanorods network prior to deposition, (b) zno nanorods network after deposition (sem images) (c) zno nanorods with deposited cdte-ncs (sem image) (d) a tem image of an object similar to that shown in © [1] s. larramendi, lidice vaillant roca, pierre saint-grégoire, johnny ferraz dias, moni behar, infiltration of cdte nanocrystals into a zno wire vertical matrix by using the isothermal closed space technique, journal of crystal growth, 475, 274 (2017) materials and devices, vol 2, #1, p 42 (2017) – doi: 10.23647/ca.md20170407 (c) (d) 200 nm mailto:saull@fisica.uh.cu mailto:behar@if.ufrgs.br mailto:jfdias@if.ufrgs.br mailto:pstgregoire@gmail.com mailto:vaillant@fisica.uh.cu first transpyrenean encounter on advanced materials – team1 – http://team1.co-ac.com theoretical study of the performance of homo and heterojunctions based on cuinse2 e.m. keita , b. mbow, c. sene, m.s. mane laboratoire des semiconducteurs et d’energie solaire, département de physique, faculté des sciences et techniques, université cheikh anta diop, dakar, sénégal email address : elouazy@hotmail.fr keywords : thin films, cuinse2, cuins2, internal quantum efficiency, homo and heterojunctions the objective of this work is to predict and enhance the electrical performance of cuinse 2 photovoltaic devices by optimizing geometrical and electrical parameters. for this purpose, two, three and four-layer structures (including window layer and substrate) are modeled for the theoretical determination of the internal quantum efficiency and the short-circuit photocurrent. first we studied homojunctions based on cuinse2 considering the following models: homojunction (cuinse2(p)/cuinse2(n)), homojunction deposited on substrate (cuinse2(p)/cuinse2(n)/cuinse2(n+)), homojunction with window layer (cuins2(p+)/cuinse2(p)/ cuinse2(n)), homojunction with window layer deposited on substrate (cuins2(p+)/cuinse2(p)/cuinse2(n)/ cuinse2(n+)). the effects of the window layer and the substrate are highlighted. secondly we considered heterojunctions based on cuinse2 using wide gap windows layers based on zno and cds according to the following models : zno(n+)/cds(n)/cuins2(p)/cuinse2(p+) and zno(n+)/cds(n)/ cuinse2(p)/cuins2(p+). based on the continuity equation which governs transport of carriers in semiconductor material, models of calculation of spectral responses of homo and heterojunctions based on cuinse2 are proposed. for each structure we have presented the energy band diagram based on the anderson model [1] and the associated continuity equation. we have established the corresponding boundary conditions between the different layers and determined the expression of the photocurrent. this expression depends on the geometrical, electrical and optical parameters that characterize the photovoltaic cell. the results obtained show that, in the case of the homojunction (cuinse2(p)/cuinse2(n)) the losses of carriers by recombination at the surface of the front layer reduce the influence of the diffusion length and provoke a low internal quantum efficiency. the deposition of a window layer based on cuins 2 on the front face (illuminated face) allows to reduce carrier losses at the surface and enhances the spectral response for radiation energies lower than his energy band gap (1.04 < e <1.57 ev). the substrate allows to enhance the internal quantum efficiency in the range of low energies (1.04 < e <1.4 ev). the structure cuins2(p+)/cuinse2(p)/cuinse2(n)/ cuinse2(n+) gives the best theoretical spectral response in the case of the homojunctions. the spectral response curves show that a thin thickness of the window layer (less than 0.1 μm) is sufficient. for the heterojunction zno(n+)/cds(n)/cuins2(p)/cuinse2(p+) where the materials are arranged with decreasing gap, the internal quantum efficiency shows that a thin thickness of the base is sufficient (on the order of 0.1 to 0.3 μm) when the recombination velocity at the interface base-substrate is lower than 2x105 cm.s-1. for high recombination velocity at the interface base-substrate (greater than 2x10 6 cm.s-1) it is preferable to increase the thickness of the base to a value greater than 3 μm. for the structure zno(n+)/cds(n)/ cuinse2(p)/cuins2(p+) the spectral response curves obtained are more elevated in comparison with the previous model. the recombination velocity at the interface base-substrate becomes less influential on the internal quantum efficiency. the spectral response is due to the absorption of the base and the space charge region. a base thickness greater than or equal to 3 μm is better. calculation of the theoretical short-circuit photocurrent under the solar spectra (am 0, am 1 and am 1.5) was established for each structure using numerical integration method. we have also determined the saturation current using some essential notions of semiconductor physics. an approximate resolution methods (graphic and numerical) are used to determine the short-circuit current, the open circuit voltage, the maximum power point and allow to evaluate the efficiency of the photovoltaic cell. these results have been applied to the heterojunction models. the calculated values remain in the range of the values reported in the literature [2]. our results validate the different models established to model the physical phenomena studied. this study is very important to dimension and optimize the different photoconductive layers. [1] r. l. anderson, ‘’germaniumgallium arsenide heterojunctions’’, ibm j.res.dev.4, 283, 1960. [2] subba ramaiah kodigala, ‘’cu(in1-xgax)se2 based thin solar cells’’, 2010, volume 35, academic press, elsevier.inc, p. 16. materials and devices, vol 2, #1, p 43 (2017) – doi: 10.23647/ca.md20170407 mailto:elouazy@hotmail.fr diapo 1 scidavis is a free application for scientific data analysis and visualizat oaj materialsoaj materials andand devicesdevices conference volumeconference volume communications presented at tramp19 communications presented at tramp19 (marrakech, morocco, november 2019)(marrakech, morocco, november 2019) guest editors daoud mezzane, mohammed guest editors daoud mezzane, mohammed gouné, khalid hoummadagouné, khalid hoummada published by collaborating published by collaborating academicsacademics http://co-ac.comhttp://co-ac.com materials and devices, vol.4, no2 (2019) pp 2912-1 – 2912-99 issn 2495-3911 doi: 10.23647/ca.md20192912 an international research journalan international research journal http://materialsanddevices.co-ac.com issn 2495-3911 general informations the oaj materials and devices is a journal created at the end oy 2016, devoted to all aspects of materials and related devices. it is open access and free of charges for authors. our aim was to create a high quality journal, with a strict peer-review process, and complying with the transparency rules edicted by the doaj, cope,... materials and devices publishes several types of articles : a : regular papers, that should present the results of original research, not published or submitted somewhere else. l : short papers, presenting original results, written as letters, focusing on one or few particular aspects, representing a very significant progress, for rapid publication. r : review papers, that presents a summary of results published in literature, on fields covered by the journal. t : technical papers, on the development of laboratory techniques and aparatus relevant to studies on materials and related devices. such papers will present the details of a given technique, and an example of application in real condition, they may also take the form of overviews or reviews. in one of these last cases, the word «  review » or « overview » will appear explicitly in the title of the article. ur   : unexpected and «   negative   » results , the journal accepts papers describing unexpected results, or results considered as negative, provided that the original ground arguments are sound, and that a reasonable interpretation can be proposed. typical examples are : a synthesis process that is generally successful, which aborts in given cases, or give different unexpected but interesting results, results contradicting a theory or a model, etc. the idea to publish such papers is mainly to save time to the scientific community by giving information that is generally not available, except as private communications between researchers. opinion articles, the journal accepts submissions of this type of papers in which authors express, expose, and motivate their opinion, suggestions, proposals, analyzes, on general, philosophical, political aspects, policies related to researches on materials and on devices, on all subjects from the production of the scientific results, to the publication and use of those results. see details in the journal’s site. comments: short articles allowing to discuss specific points of an article that preferentially has been published in the oaj materials and devices, and that is of particular importance for the readership of the journal. they should not attack the article, but provide a scientific, objective view or commentary, or complementary informations in a respectuous style. conf: conference papers : oaj materials and devices may also publish conference proceedings and conference papers in special volumes. organizers of conference interested should contact the journal in advance to know details. (updated on june, 21st, 2019) aims and scope of the journal the topics covered by the journal are wide, it aims at publishing papers on : all aspects related to materials, namely according to their chemical formula (oxides, fluorides, carbon compounds, …, organic, inorganic), to their physical properties (conductors, super-conductors, semi-conductors, insulators, dielectrics,...), to their nature (crystalline or amorphous materials, liquid crystals, modulated systems, aperiodic materials, nanomaterials and nanostructured materials)… or environmental type (ecomaterials), or according to some specific applications. papers on biomaterials, geomaterials, archeomaterials or on studies of ancient materials are also welcome. a particular attention is also paid on environmental studies related with materials. authors are also encouraged to submit papers on theoretical studies applied to materials, including pure mathematical approaches, physical approaches, models, numerical simulations, etc. oaj materials and devices i http://materialsanddevices.co-ac.com/ devices in a wide sense. concerning devices, the scope is restricted to those integrating given materials (for instance memories based on some specific magnetic materials) or those related to materials in their study or use (for instance specific instruments in materials science, devices of interest for the use of particular materials,...) . papers on all types of such devices are welcome. policy of the journal materials and devices is an open access (*) journal which publishes original, and peer-reviewed papers accessible only via internet, freely for all. your published article can be freely downloaded, and self archiving of your paper is allowed! we apply « the principles of transparency and best practice in scholarly publishing » as defined by the committee on publication ethics (cope), the directory of open access journals (doaj), and the open access scholarly publishers organization (oaspa). the journal is now indexed by the doaj and listed by this organization. evaluation – peer-reviewing : after reception, the paper is sent to reviewers for evaluation. in case of negative or divergent opinions of reviewers, the editor-in-chief sends the paper to another reviewer and then gives a final decision based on all reports. reviewers are asked to reply within three weeks to warranty a fast publication process. copyright on any article in the oaj materials and devices is retained by the author(s) under the creative commons (attribution-noncommercial-noderivatives 4.0 international (cc by-nc-nd 4.0)), which is favourable to authors. (*) an open access journal means that all content is freely available without charge to the user or his/her institution. users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. this is in accordance with the boai definition of open access. international editorial board – list of members orientation of the journal, choice of reviewers, special issues, editorial policy, etc, are discussed by the international editorial board. algeria mokhtar boudissa, professor researcher, dpt ebt, enmc laboratory, faculté de technologie, université f. abbas setif-1, sétif  19000 boudi44 @ yahoo.fr brazil paulo t.c. freire, full professor, universidade federal do ceará, fortaleza tarso @ fisica.ufc.br josé de los santos guerra, professor, instituto de física, universidade federal de uberlandia (ufu), uberlandia – jsantosguerra @ gmail.com burkina faso dieudonné joseph bathiebo, full professor, university of ouagadougou – djbathiebo@gmail.com canada zuo-guang ye, professor, simon fraser university, burnaby, bc zye@sfu.ca cuba aimé peláiz barranco, full professor, physics faculty, havana university pelaiz@fisica.uh.cu maria sánchez, full professor, faculty of physics, university of havana – maruchy @ fisica.uh.cu elena vigil, full professor, physics fac. materials sc. & tech. inst. (imre), university of la habana, and solar energy cathedra chairperson, cubasolar-u.h. evigil @ fisica.uh.cu czech republic ivan gregora, institute of physics, czech academy of science, prague gregora@fzu.cz vacláv janovec, emeritus professor, prague denmark heloisa bordallo, associate professor, niels bohr institute university of copenhagen france patrice bourson, professor, lmops université de lorraine - centralesupelec 2 rue e. belin 57070 metz patrice.bourson@univ-lorraine.fr oaj materials and devices ii mailto:patrice.bourson@univ-lorraine.fr mailto:gregora@fzu.cz mailto:evigil@fisica.uh.cu mailto:maruchy@fisica.uh.cu mailto:pelaiz@fisica.uh.cu mailto:zye@sfu.ca mailto:djbathiebo@gmail.com mailto:jsantosguerra@gmail.com mailto:tarso@fisica.ufc.br mailto:boudi44@yahoo.fr alain claverie, research director, cemes/cnrs toulouse, and private consultant to several companies (microelectronics, areospace) claverie@cemes.fr pierre saint-grégoire, dr hab, president of collaborating academics, https://fr.linkedin.com/in/saint-gregoire-pierre-5bb6372b, pstgregoire@gmail.com philippe sciau, senior scientist, cemes-cnrs, 29 rue j. marvig, 31055 toulouse philippe.sciau@cemes.fr georges zissis, professor, université toulouse 3 paul sabatier; laboratoire laplace umr 5213, toulouse georges.zissis@laplace.univ-tlse.fr germany lukas m. eng, tu dresden, institute of applied physics, and also, center for advancing electronics dresden lukas.eng@tu-dresden.de india amit das, doctor, solid state physics division, bhabha atomic research centre, trombay, mumbai 400085 sm yusuf, head, magnetism section, and professor at homi bhabha national institute, solid state physics division, bhabha atomic research centre, trombay, mumbai 400085 israël gil rosenman, the henry and dinah krongold chair of microelectronics, school of electrical engineering-physical electronics, faculty of engineering, tel aviv university, ramat aviv gilr@eng.tau.ac.il kazakhstan koblandy turdybekov, head of the department of physics, karaganda state technical university, karaganda xray-phyto@yandex.kz mexico a. guillermo castellanos-guzmán, professor-researcher, dip cucei universidad de guadalajara, guadalajara jal. gcastel@cucea.udg.mx moldova anatolie sidorenko, director, institute of electronic engineering and nanotechnologies "d.ghitu" asm – anatoli.sidorenko@nano.asm.md, anatoli.sidorenko@kit.edu morocco abdelhai rahmani, professor, physics department, faculty of sciences, meknes rahmani614@gmail.com / a.rahmani@flsh.umi.ac.ma people republic of china yang gan, professor, department head, harbin institute of technology, harbin ygan@hit.edu.cn qinghui jiang, assoc professor, state key laboratory of material processing and die & mould technology, and school of materials science and engineering, huazhong university of science and technology, wuhan 430074 qhjiang@hust.edu.cn zhifu liu, professor, cas key lab of inorganic functional materials and devices, shanghai institute of ceramics, chinese academy of sciences liuzf@mail.sic.ac.cn xiaoyong wei, professor, electronic materials research laboratory (emrl) xi’an jiaotong university, xi’an 710049 wdy@mail.xjtu.edu.cn poland maria zapart, institute of physics, faculty of production engineering and materials technology, czestochowa university of technology -  zapart@wip.pcz.pl russian federation boris darinskii, professor, voronezh state university, university sq.1, voronezh 394006 darinskii@mail.ru alexander sidorkin, professor, voronezh state university, university sq.1, voronezh 394006 sidorkin@phys.vsu.ru alexander sigov, professor, head of condensed matter physics chair, president of the university, moscow technological university, moscow sigov@mirea.ru mikhail smirnov, professor, physical department, st. petersburg state university smirnomb@rambler.ru oaj materials and devices iii mailto:smirnomb@rambler.ru mailto:sigov@mirea.ru mailto:sidorkin@phys.vsu.ru mailto:darinskii@mail.ru mailto:zapart@wip.pcz.pl mailto:wdy@mail.xjtu.edu.cn mailto:liuzf@mail.sic.ac.cn mailto:qhjiang@hust.edu.cn mailto:ygan@hit.edu.cn mailto:a.rahmani@flsh.umi.ac.ma mailto:rahmani614@gmail.com mailto:anatoli.sidorenko@kit.edu mailto:anatoli.sidorenko@nano.asm.md mailto:gcastel@cucea.udg.mx mailto:xray-phyto@yandex.kz mailto:gilr@eng.tau.ac.il mailto:lukas.eng@tu-dresden.de mailto:georges.zissis@laplace.univ-tlse.fr mailto:philippe.sciau@cemes.fr mailto:pstgregoire@gmail.com https://fr.linkedin.com/in/saint-gregoire-pierre-5bb6372b mailto:claverie@cemes.fr alexander vtyurin, deputy director, head of raman spectroscopy group, kirensky institute of physics, krasnoyarsk vtyurin@iph.krasn.ru senegal issakha youm, professor, department of physics, fst, university cheikh anta diop de dakar, dakar-fann singapore pooi see lee, professor, nanyang technological university, singapore, pslee@ntu.edu.sg south africa malik maaza, chair, unesco unisa africa chair in nanosciences, college of graduate studies, unisa, pretoria, & nanoafnet, ithemba labs, national research foundation of south africa, faure, western cape maaza@tlabs.ac.za , maazam@unisa.ac.za spain carmen aragó, full professor, dpt. física de materiales, universidad autónoma de madrid carmen.arago@uam.es paloma fernández, full professor, department materials physics, fac. of physics, university complutense, madrid arana@fis.ucm.es emilio j. juarez-perez, senior researcher, araid foundation, ina institute of nanoscience of aragon, icma aragon materials science institute, zaragoza university. campus río ebro. edificio i+d. c/ mariano esquillor, s/n, 50018 -zaragoza ejjuarezperez@unizar.es, http://araid.es/es/users/ejjuarez javier piqueras, professor, universidad complutense de madrid togo kossi napo, professor, unesco chair on renewable energies, faculty of sciences, university of lomé -  silnapo@yahoo.fr tunisia hamadi khemakhem, professor, faculty of sciences of sfax, sfax hamadi.khemakhem@fss.usf.tn ukraine yulian vysochanskii, professor, uzhgorod national university, uzhgorod vysochanskii@gmail.com united kingdom james f. scott, depts. of chemistry and physics, st. andrews university, st. andrews, fife, uk ky16 9st jfs4@standrews.ac.uk: usa michael d. hampton, professor, department of chemistry, university of central florida, orlando, fl  32816 alexei gruverman, professor of physics, university of nebraska-lincoln agruverman2@unl.edu anirudha v. sumant, ph.d., materials scientist, center for nanoscale materials, argonne national laboratory, 9700 s. cass ave., building 440, room a-127, argonne, il 60439 sumant@anl.gov , linkedin profile: http://www.linkedin.com/in/anisumant editor-in-chief   : pierre saint-grégoire (france) – pstgregoire@gmail.com people interested in this project are welcome ! contact us to submit your proposals, ideas, suggestions, or to get involved in some actions ! materials and devices (issn 2495-3911) is a relatively new journal, and as such, is not yet indexed. however in future we shall consider as a priority task, to reach a significant impact factor for this journal. oaj materials and devices iv mailto:hamadi.khemakhem@fss.usf.tn mailto:silnapo@yahoo.fr http://www.linkedin.com/in/anisumant mailto:sumant@anl.gov mailto:agruverman2@unl.edu mailto:jfs4@st-andrews.ac.uk mailto:jfs4@st-andrews.ac.uk mailto:vysochanskii@gmail.com http://araid.es/es/users/ejjuarez mailto:ejjuarezperez@unizar.es mailto:arana@fis.ucm.es mailto:carmen.arago@uam.es mailto:ac.za/maazam@unisa.ac.za mailto:maaza@tlabs.ac.za mailto:pslee@ntu.edu.sg mailto:vtyurin@iph.krasn.ru abstracts book cadi ayyad university, faculty of sciences and technologies marrakech 7-9 november 2019 marrakech, morocco third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p2 the third international symposium tramp19 follows the previous successful events, tramp14, and tramp17 and was held in the warm and hospital city marrakech in morocco, on 7-9 november 2019. the symposium was dedicated to the different aspects of the materials science and especially to advanced materials and their applications in energy, transport, medical and biological sectors. it has been a great opportunity for the junior and experienced scientists to share their knowledge on these hot subjects. tramp ‘s objectives and topics of interest: bring together a broad international community of scientists, engineers and phd students. provide opportunities to strengthen existing collaborations and exchange of ideas to bring new partnerships. create a forum for researches and experts regarding to nanomaterials, train students and young researchers. synthesis, characterizations and properties of nanomaterials. characterizations and properties of surfaces and interfaces. functional and nanostructured materials. nanostructured thin films. metallurgy, metal alloys and corrosion. synthesis and applications of nanocomposites. nanomaterials for energy and environment applications. nanomaterials applications for electronics, medicine and biotechnologies. scanning probe techniques. https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p3 organizing institutions • laboratory of condensed matter and nanostructures, university cadi ayyad, morocco • university mohammed v, rabat, morocco (cnrst priority program ppr 15/2015) • institute of condensed matter chemistry of bordeaux (icmcb), france • institute microelectronic materials and nanosciences of provence, aix marseille university, marseille, france • european research and innovation network “engineering of nanostructures with giant magneto-piezoelectric and multicaloric functionalities” horizon-rise-engima. organizers • mohamed goune, icmcb, bordeaux, france • khalid hoummada,im2np, aix marseille university, marseille, france • hamadi khemakhem, lamma, faculty of sciences, sfax, tunisia • daoud mezzane, lmcn, university of cadi ayyad, marrakech, morocco organising committee • university of cadi ayyad, marrakech, morocco abdelhadi alimoussa, samira amhil, m’barek amjoud, said benmoumen, elhassan choukri, lhouceine hajji, zouhair hanani, abderahim ihyadn, said khardazi, soukaina mersmliz, daoud mezzane, hanane mezzourh, aziz neqali, hajar zaitouni • university mohammed v, rabat, morocco abdallah el kenz, hassan el moussaoui, el mehdi salmani • im2np, aix marseille university, marseille, france yves klein, nouredine oueldna • icmcb/cnrs, bordeaux, france sebastien fourcad https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p4 international scientific committee: • m’barek amjoud, university of cadi ayyad, marrakech, morocco • mohamed chérif benoudia, national school of mines and metallurgy, annaba, algeria • ahmed chitnalah , university of cadi ayyad, marrakech, morocco • abdelilah benyoussef , hassan ii academy of sciences and technologies, rabat, morocco • lahcen bih, university of moulay ismail, meknès, morocco • sylvie bordère, i2m/cnrs, bordeaux, france • ahmed charai, university aix-marseille, france • youssef el amraoui, university of moulay ismail, meknès, morocco • mimoun el marssi, university of picardie jules verne, amiens, france • lahcen essaleh, university of cadi ayyad, marrakech, morocco • hamid ez-zahraouy, university mohammed v, rabat, morocco • abdeslem fnidiki, gpm université de rouen, france • yaovi gagou, university of picardie jules verne, amiens, france • stéphane gorsse, icmcb/cnrs, bordeaux, france • mohammed hamdani, university ibno zohr, agadir, morocco • mohammed hamedoun, university mohammed v, rabat, morocco • hamid keddami, university of cadi ayyad, marrakech, morocco • zdravko kutnjak, jožef stefan institute, ljubljana, slovenia • mohammed lahcini, university of cadi ayyad, marrakech, morocco • abdelilah lahmar, university of picardie jules verne, amiens, france • mohamed loulidi, university mohammed v, rabat, morocco • igor lukyanchuk, university of picardie jules verne, amiens, france • oksana mykaylo, uzhgorod national university ukraine • abdelmoula najmeddine, faculty of sciences, sfax, tunisia • abdelhai rahmani , university of moulay ismail, meknès, morocco • mustapha raihane, university of cadi ayyad, marrakech, morocco • benaissa rhouta, university of cadi ayyad, marrakech, morocco • slim zghal, faculty of sciences, sfax, tunisia https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p5 sponsors of tramp19 symposium university of bordeaux cadi ayyad university aix-marseille university mohammed v university of rabat engima project laboratory of condensed matter and nanostructures faculty of science and techniques of marrakech institute of condensed matter chemistry bordeaux institute for materials, microelectronic and nanosciences of provence national center for scientific research national center for scientific and technical research society of development of science and novel technologies https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p6 plenary speakers https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p7 ps001 materials science of nanostructures: understanding of the future a. v. ragulya1,2* 1institute for problems of materials science, national academy of sciences of ukraine, krjijanovskogo 3, 03142 kyiv, ukraine 2 nanotechcenter llc, krjijanovskogo 3, 03142 kyiv, ukraine e-mail*/ andrey.ragulya@gmail.com abstract the main feature of nanomaterials is the dependence of their properties on the size of the structural element. the main feature of nanotechnology is the ability to operate with nanomaterials that have a certain structure. therefore, the diversity of structural forms increases every year by exponential low. the escalation of complexity and variety of nanostructures is an intensive way of nanotechnology development today, alternatively to the combinatorics with chemical composition, which gives extensive growth. examples are known: nanotubes, fullerenes – all first time have been predicted and obtained from carbon only and then were composed from other elements or chemicals. the same happened with 2d materials: from graphene to graphene-like sulfides, selenides, maxenes, and others.new structural forms and new materials with extraordinary properties are ahead. the classical materials science is grounded on the study of relations between composition, structure and properties of materials, taking into account the processes of production and processing and production economics. in terms of physics and chemistry, we are accustomed to perceiving material through the prism of the energy of interatomic interaction. classical materials science is first and foremost the science of bodies in which covalent chemical bonds with energy higher than 2 electron volts operate. in this coordinate system we consider the majority of material properties strength and hardness, thermal conductivity and diffusion, ferroelectricity and luminescence. however, in nature, there are also low energy bonds, there are mechanisms providing self-assembly and self-organization of nanoparticles with the aid of weak bonds. for the convergence of the two segments of materials science it is necessary to develop new processes with feedback, which allow to create new structures, new methods of analysis of these structures, new methods of control of process parameters. development of multiscale modeling and design of new structures and materials is required. for example, methods of operating 2d materials are required to connect them to complex devices. it is possible to mix the maxenes evenly as a powder in the polymer and to obtain a screen from microwave radiation. it is possible to construct an ordered layered structure, an electronic device, by ordering the nanoparticles in an external field. keywords: strong chemical bonds, weak chemical bonds, complex nanostructures aknowledgement: this work was supported in part by the research executive agency (grant agreement 778072 — engima — h2020-msca-rise-2017). https://sites.google.com/site/tramp2019marrakech/ mailto:andrey.ragulya@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p8 ps002 is the nanopiezotronics based on a piezoelectric effect? franck dahlem* e-mail*/ franck.dahlem@cermav.cnrs.fr abstract the nanopiezotronics refers to the research field on the coupling between semiconducting and piezoelectric properties of nano-objets. it was for instance observed that the mechanical deformation of flexible structures based on zno or iii-nitride nanowires generates electrical spikes [1] or modifies their i/v characteristic. the piezoelectricity was claimed as the origin of these electro-mechanical couplings which could result on a broad range of new applications from nano-generators to nano-sensors [2]. in this talk, the spontaneous and piezoelectric polarizations of iii-nitride materials will be described and the local study of the surface potential and piezocharges will be presented in order to investigate the nanopiezotronic signal obtained via conductive scanning probe microscopy in iii-n nanowires. the results emphasize the negligible role of the piezoelectric effect [3], especially via the questioning of the giant piezoelectricity which was claimed to be present in such nanowires [4]. several scanning force microscopy techniques dedicated to the local probing of electro-behaviors like the kelvin probe force microscopy (kpfm) or the piezoresponse force microscopy (pfm) will be introduced during the presentation with a special care concerning their applications to semiconductors and related artifacts. references [1] z.l. wang , j.h. song , science 312 , 242 (2006) [2] z.l. wang , mrs bulletin vol. 37 (2012) [3] l. jaloustre, s. le-denmat, t. auzelle, m. azadmand, l. geelhaar, f. dahlem, r. songmuang, arxiv. (2019) [4] m. minary-jolandan, r. a. bernal, and h. d. espinosa, mrs communications 1, 45 (2011) https://sites.google.com/site/tramp2019marrakech/ mailto:franck.dahlem@cermav.cnrs.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p9 ps003 the relationship between the energetic performance of rechargeable batteries and the properties of their electrode materials ismael saadoune1* 1cadi ayyad university, marrakech email*/ i.saadoune@uca.ma abstract the depletion of fossil fuels and their drastic effects on the environment are becoming problematic. hence, researchers were encouraged to use the clean renewable energies and to smoothly transit from thermal to electrical vehicles. nevertheless, these two energetic applications require efficient energy storage technologies to fit with their impressive recent development. owing to its high-energy density, long life cycling, lightweight and recyclability, lithium-ion batteries (libs) are widely used for portable electric devices along with electric vehicles (evs). sodium ion batteries (na-ion) are also predicted to be promising low cost alternatives of the current lithium technology especially in large-scale applications. the concept of li-ion and na-ion consists of the reversible exchange of the alkali metal between the anode and the cathode materials, that constitute the main component of these two technologies. the energetic performances of the liand na-ion (capacity, voltage, energy, cycling…) strongly depend on the structure and the physico-chemical performance of the electrode materials. through some recent investigations done in lcme laboratory (uca), this keynote will present a series of example elucidating the dependence of the storage performance of li and na-ion batteries on the features of the electrodes. keywords: energy storage, li-ion batteries, na-ion batteries, electrode materials. acknowledgements: the author would like to thank ocp, iresen and cnrst for their financial support. https://sites.google.com/site/tramp2019marrakech/ mailto:i.saadoune@uca.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p10 ps004 entropic description of a mg-based metallic glass from serrations statistics yannick champion1* 1univ. grenoble alpes, cnrs, simap, 38000 grenoble, france e-mail*/ yannick.champion@simap.grenoble-inp.fr abstract series of independent instrumented nano-indentation experiments were performed on a mg65cu12.5ni12.5(ce75la25)10 metallic glass at room temperature and at strain rates in the range of 1 to 0.3 s-1. the loading part of curves shows serrations which size and frequency of occurrence were measured using an automated procedure. it was conjectured, that (i) serration occurs through rearrangement of appropriate zone in the glass that should naturally scale with a multiple of an elementary domain size characterizing the deformation mechanism. (ii) as activated zones leading to serration are very few, the process should fit with rare event dynamics. actually, serration sizes are well fitted by a poisson distribution and the waiting times between successive serrations is consistent with the poisson statistics. the model predicts an elementary domain which size scales with that of the activation volume of about 3 atoms, measured from nano-indentation near-creep tests at constant load in the same series of experiments (thurieau et al, j. appl. phys. 2015). dynamics of shear bands initiation, which is seemingly of avalanche type, is analyzed using the statistical approach proposed by adam and gibbs (j. chem. phys. 1965) to describe viscosity. an entropic description is proposed where elementary domains are associated to energy levels and able to cooperatively evolve to form avalanches (serrations). https://sites.google.com/site/tramp2019marrakech/ mailto:yannick.champion@simap.grenoble-inp.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p11 ps005 ferroelectric topological nanomaterials for ultrafast computing circuits with low energy dissipation luk’yanchuk*,a, yu. tikhonovb, a. sénea, a. razumnayab, v. vinokourc a university of picardie, france, b southern federal university, russia, c argonne national laboratory, usa email*/ lukyanc@ferroix.net abstract formation of unusual textures of polarization is imminent for nano-scale ferroelectric samples, films, rods, and granules, where the depolarization surface effects play a crucial role. the topologically protected stability of such textures and security of information storage is coming from polarization vorticity, provided by the condition of absence of the energetically-unfavorable depolarization charge. the endurance of ferroelectric formations with respect to high-energy irradiation makes them ideal for the aerospace industry, and the periodic domain walls structures can be used as a platform for terahertz radiation, generators and detection devices. polarization domains that alternate the surface charge distribution can be formed in ferroelectric thin films as an effective mechanism to confine the depolarization field to the near-surface layer and diminish the depolarization energy. however, their existence has long been considered as barely possible until the direct theoretical predictions [1,2] and experimental evidence [3,4] in thin oxide-based superlattices. very recently we have demonstrated that the effective capacitance of ferroelectric layers with domains is negative [5,6]. this effect is explained by the opposite orientation of the depolarizing field with respect to the field-induced averaged polarization. this phenomenon is currently considered as the platform for the realization of the dissipation-free high-performance nano-circuits [7]. moreover, in the sub-thz region, the resonance plasmonic effect can be induced by oscillating domain walls [8] and can be suitable for the design of the ultra -small lowenergy thz chips. multi-vortex [9] and skyrmion [10] states can be formed inside ferroelectric cylindrical nano-dots and nanorods to reduce the depolarization energy. we study the topological stability of such states and target the multi-domain and topological excitations in fe nanodots as a platform for it-secured multivalued logic units, breaking ground for neuromorphic computing [11,12]. references [1] a. m. bratkovsky and a. p. levanyuk, phys. rev. lett. 84, 3177 (2000). [2] i. a. luk'yanchuk, et al. phys. rev. lett., 94, 047601 (2005), ibid. 102, 147601 (2009) [3] s. k. streiffer, j. a. eastman, d. d. fong et al., phys. rev. lett. 89, 067601 (2002); [4] s. o. hruszkewycz, m. j. highland, et al., phys. rev. lett.110, 177601 (2013). [5] p. zubko, …, a. sené, i. luk’yanchuk, j.-m. triscone & j. íñiguez, nature, 534, 524 (2016) [6] i. luk’yanchuk, et al. (nature) communications physics 2, 22 (2019) [7] j. íñiguez, p. zubko, i. luk’yanchuk, & a. cano, nature reviews materials, 4, 243 (2019) [8] i. luk'yanchuk, a sené, v. vinokour, phys. rev. b 98, 024107 (2018) [9] g. pascoli l. lahoche, i. luk'yanchuk, integrated ferroelectrics, 99, 60 (2008) [10] l baudry, a sené, ia luk'yanchuk, l lahoche, and jf scott, phys. rev. b 90, 024102 (2014) [11] p.-w. martelli, s. m. mefire, i. luk'yanchuk, europhys. lett. 111, 50001 (2015) [12] baudry, l., lukyanchuk, i. & vinokur, v. m. sci. rep. 7: 42196 (2017) [13] keywords: ferroelectrics, thz radiation, nanoelectronics, multibit logic, negative capacitance https://sites.google.com/site/tramp2019marrakech/ mailto:lukyanc@ferroix.net third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p12 ps006 3d imaging of materials chemistry at the atomic-scale by atom probe tomography f. danoix, m. gouné*, k. hoummada**, r. danoix, f. vurpillot, d. blavette gpm – umr cnrs 6634 – normandie université – france * icmcb upr cnrs 9048 bordeaux – france ** im2np, cnrs, aix marseille université (france) e-mail*/ frederic.danoix@univ-rouen.fr abstract the technique of atom probe tomography (apt) enables atomic level microstructural characterization to be performed on a wide range of materials, from laboratory model to complex engineering alloys, to thin multilayer films, semiconducting structures and devices, and, since recently, to ceramic materials. the intrinsic performances of recent instruments will be presented, and well as their unique outcomes. information on the size, morphology and compositions of coexisting phases, solute partitioning of the elements between the phases, and solute segregation to defects, like dislocation lines, interfaces and grain boundaries can be obtained down to the atomic scale. these informations lead to a more complete understanding of fundamental and service properties of complex engineering materials. the types of atomic level information that may be obtained with atom probe tomography are illustrated in a large variety of materials. https://sites.google.com/site/tramp2019marrakech/ mailto:frederic.danoix@univ-rouen.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p13 ps007 toward material engineering and applications mustapha jouiad* e mail*/ mustapha.jouiad@u-picardie.fr abstract the inherent increasing demand in energy solutions and new technologies in various sectors such as transport and environment has prompted scientists to custom the materials design and properties for targeted application. most of the newly developed materials are complex composites with more and more reduced size and dimensions. special fabrication techniques have then emerged to make the processing possible and easily tunable. among these techniques and the list is not exhaustive: atomic layer deposition, plasma enhanced chemical vapor deposition, electron beam & thermal evaporators, magnetron sputtering, electron beam and photo lithography have attracted increasing interest due to their volatility and reproducibility. in parallel and to accommodate this progress made in nanomaterials, advanced characterization techniques such as high-resolution scanning transmission electron microscopy (hrstem), electron energy loss spectroscopy (eels), scanning near-field optical microscopy (snom), in situ experiments (tem+afm+sem) and 3d imaging, appear as major tools to first evaluate the processing routes and parameters, then to correlate the fabricated materials to their targeted application. this duality, which consists of closing the loop between these two aspects fabrication and characterization in one hand and the material testing in the other hand, is a must to achieve cutting edge research and breakthrough. ultimately, this approach will allow better prediction of the material design for the desired application. in addition, as this approach lies in cross disciplines, it gives to scientists leverage to overcome the multidisciplinary aspect related to nanotechnology. in this seminar, this approach will be applied to novel materials with special emphasis to the potential applications in energy harvesting & conversion, sensing, biology, and communications. these applications can find use in different domains such as space, transport and energy saving. https://sites.google.com/site/tramp2019marrakech/ mailto:mustapha.jouiad@u-picardie.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p14 ps008 soft caloric liquid crystal-based materials brigita r.,1,* gregor s.,2 boštjan z.,1 samo k.,1,3 zdravko k.1 1 jožef stefan institute, ljubljana, slovenia 2 faculty of mathematics and physics, university of ljubljana, ljubljana, slovenia 3 faculty natural sciences and mathematics, university of maribor, maribor, slovenia email*/ brigita.rozic@ijs.si abstract caloric effects are manifested in the heating or cooling a caloric material due to the application or removal, respectively, of the external field under nearly adiabatic conditions. materials with large caloric effects, such as the electrocaloric (ec) and elastocaloric (ec) effects, have the promise of realizing new solid state refrigeration techniques [1, 2]. first proof of such conceptual cooling devices was produced from relaxor ferroelectric ceramic and polymer thin films [3, 4], but with rather low power density, due to the relatively large ec inactive regenerator mass [5]. the natural idea is to replace such regenerator with the ec active dielectric fluid, such as liquid crystals (lcs), which may improve the power density of ec cooling devices. another soft material, called liquid crystal elastomers (lces), are good candidates with large elastocaloric effect with potentially better elastocaloric responsivity than shape memory alloys wires, in which the ec temperature change of 40 °c was observed at 0.8 gpa stress field [6]. in this contribution a review of recent direct measurements of the large ec effect in lcs and large ec effect in lces [7, 8] will be given. in smectic liquid crystalline materials and mixtures of lcs with functionalized nanoparticles the ec effect exceeding 8 k was found in the vicinity of the isotropic to smectic a phase transition. direct ec measurements indicate that the ec response is significantly enhanced by the latent heat [9]. further, the results of direct measurements of the ec in side-chain and main-chain (mc) lces will be presented. the ec change of temperature of about 1 k was observed in mclces. however, both soft materials can play a significant role as active cooling elements and parts of thermal diodes or regeneration material in development of new cooling devices. references [1] z. kutnjak et al., wiley encyclopedia of electrical and electronics engineering, p. 1-19 (2015). [2] x. moya et al., nature mater. 13, 439 (2014). [3] s.-g. lu et al., appl. phys. lett. 97, 162904 (2010). [4] b. rožič et al., j. appl. phys. 110, 064118 (2011). [5] u. plaznik et al., appl. phys. lett. 106, 043903 (2015). [6] e. a. pieczyska et al., exp. mech. 46, 531 (2006). [7] i. lelidis and g. durand, phys. rev. lett. 76, 1868 (1996). [8] x.-s. qian et al., adv. funct. mater. 23, 2894 (2013). [9] e. klemenčič et al., scientific reports. 9, 1171 (2019). keywords: electrocaloric, elastocaloric, liquid crystal, liquid crystal elastomers https://sites.google.com/site/tramp2019marrakech/ mailto:brigita.rozic@ijs.si third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p15 invited speakers https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p16 is001 nanocrystalline multifunctional pr-co compounds: permanent magnets, magnetic refrigeration and hydrogen storage fersi ra. bouzidia,b w., patout lc., charaï a. c bessais l. b and thabet-mliki n. a* a université de tunis el manar, lmop lr99es17 faculté des sciences de tunis, b université paris est, icmpe (umr 7182), cnrs, upec, f94320 thiais france c aix-marseille université – cnrs, im2np, faculté des sciences de jérôme, f-13397 marseille, france e mail*/ najeh.mliki@fst.utm.tn abstract rare-earth transition metal intermetallics rmn, where a rare earth (r) is combined with a transition metal (m), are attractive compounds for their technological magnetic application. of all them, only the r-3d intermetallics ever exhibit a significant magnetic moment on the m partner. this group is the subject of this work. after presenting the relevant theoretical models for magnetism in r-3d intermetallics the crystallographic relations between the stoichiometry are discussed. following a detailed treatment, the overall magnetic properties are summarized. the characteristics of the intermetallic compound rmn are depending on the nature of the metals involved and the stoichiometry of the compound. we focus here in the pr-co binary system, it forms several intermetallic compound which have structural and magnetic properties enough different. these compounds can crystallize in hexagonal and rhombohedral structures depending on annealing temperature. the structures of prcox compounds derived from the structure of the compound by replacing prco5 third of rare earth atoms by a pair of atoms of transition metal smaller. the crystal structure of pr2co7, as well as pr5co19 compounds, can be constructed by the substitution of co atom by the rare earth atom in each mesh prco5, as well as the prco3 and prco2 compounds, by an ordered substitution of atoms. these compounds exhibit magnetic properties that can be exploited to produce soft, hard or semi-hard magnetic materials. the origin of these unique magnetic properties is mainly due to the coexistence of two complementary types of magnetism: magnetism characteristic of localized 4f electrons of the rare earths and itinerant magnetism of the 3d electrons of the transition metals. moreover, we report that the insertion of a light element such as carbon or hydrogen, allows to increase the curie temperature of these systems. the related hydrides present a reversible cycle of absorption/desorption. we also report on the study of the magnetocaloric effect (me) of the intermetallic pr-co type. it shows that the me effect is sensitive to the stack configuration. the temperature dependence of the magnetization (m vs. t) and the arott plots around the second order magnetic transition for pr5co19 and pr2co7 compounds are reported. these results indicate that pr-co compounds could be good candidates for permanent magnets, but also for magnetic refrigeration at high temperature and for hydrogen storage. keywords: nanomaterials, permanent magnets, magnetic refrigeration, hydrogen storage, energy. https://sites.google.com/site/tramp2019marrakech/ mailto:najeh.mliki@fst.utm.tn third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p17 is002 lead-free and antiferroelectric materials as electrocaloric coolants b. rožič,1 b. asbani,2 m. el marssi,2 h. uršič,1 j. koruza3, b. malič,1 r. pirc,1 d. mezzane,4 z. kutnjak,1* 1jožef stefan institute, jamova cesta 39, 1000 ljubljana, slovenia 2lpmc, university of picardie jules verne, 33 rue saint-leu, amiens, france 3technical university darmstadt, alarich-weiss-str. 2, darmstadt, germany 4lmcn, f.s.t.g. university cadi ayyad, bp 549, marrakech, morocconiversity/ institute email*/ zdravko.kutnjak@ijs.si abstract the request for greener heat-management technologies has recently developed significant interest in new electrocaloric (ec) effect-based cooling devices that have the potential to replace the existing cooling technics [1,2]. in this contribution the direct measurements of the large ec effect in antiferroelectric, leadbased and lead-free ferroelectric materials [3,4] will be presented. specifically, the negative ec effect in antiferroelectric pzstn, n/95/5 plzt and pbz ceramics will be investigated by direct experiments. here, it is demonstrated that both negative and positive ec response can be arbitrarily invoked in antiferroelectric materials by properly controlling the electric field and temperature. in addition, the large positive ec response observed by direct experiments in lead-free bctz-based ferroelectric materials will be reviewed. a prototype of electrocaloric based cooling device using a regeneration technique will be presented, its properties reviewed and compared to existing caloric prototypes. references: [1] z. kutnjak., b. rožič, r. pirc., wiley encyclopedia of electrical and electronics engineering, p. 1-19 (2015). [2] a. s. mischenko et al., science 311, 1270 (2006). [3] r. pirc, b. rožič, j. koruza, g. cordoyiannis, b. malič, z. kutnjak, j. phys.: condens. matter 27, 455902 (2015). [4] b. asbani, j.-l. dellis, a. lahmar, m. courty, m. amjoud, y. gagou, k. djellab, d.mezzane, z. kutnjak, m. el marssi, appl. phys. lett. 106, 042902 (2015). keywords: antiferroelectric, ferroelectric, electrocaloric, dielectric, lead-free https://sites.google.com/site/tramp2019marrakech/ mailto:zdravko.kutnjak@ijs.si third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p18 is003 characterizing the porosity in thin bst films by laseracoustic waves. fouzia tayaria,wolfgang donnerb and anouar njeha*. alaboratoire de physique des matériaux, faculté des sciences de sfax, université de sfax, tunisia. binstitute of materials science, university of technology, petersenstr.23, 64287 darmstadt, germany. e-mail*/ njehanouar@gnet.tn abstract porosity may be harmful for the properties of thin films. depositing dense films is often the aim of the technological development, although there are also applications requiring adjusting a special amount of pores in the film. in thin films, the pore dimension is in the sub-micrometer range so that detecting the pores is difficult. the laser-acoustic technique is shown to be able to indicate an enhanced porosity in thin films. it is based on surface acoustic waves and yields young’s modulus of the film. the elastic modulus of the material is distinctly influenced by porosity. it reduces with increasing porosity and depends also on the shape of the pores. test series of bst (ba0.65sr0.35tio2) thin films with porosity were deposited on pt/tio2/sio2/si substrate. the laser-acoustic tests yielded elastic moduli for the films that were up to 24% lower compared to the value of the bulk material. the lowering of young’s modulus was found to correlate with increasing porosity. for the manufactured bst series a pore volume fraction up to approximately 7% was estimated. a theory for young’s modulus depending on porosity, also taking into account the pore shape, was employed to deduce information on the pore structure from the laser-acoustic results . key words: bst thin films, texture, porosity, laser acoustic waves. https://sites.google.com/site/tramp2019marrakech/ mailto:njehanouar@gnet.tn third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p19 is004 structural, dielectric and energy storage properties of neodymium niobate with tetragonal tungsten bronze structure mahfoud belarbi, abdelilah lahmar1*, yaovi gagou and mimoun el marssi 1university of picardie jules verne/ laboratory of condensed matter physics e mail*/ abdel.ilah.lahmar@u-picardie.fr /phone:+33322827691 abstract the present work reports on the effects of nd3+ substitution on the structural, dielectric and energy storage behaviour of polycrystalline ba2nanb10o30 (bnn) ceramics. the ferroelectric lead-free ba2na1-xndx/3nb5o15 ceramics were prepared by conventional solid-state reaction technique. the room temperature x-ray study and raman investigations have allowed to evidence the stabilization of a tetragonal tungsten bronze structure with p4bm as space group for all studied compound. dielectric study carried out on the prepared ceramics has permitted to determine the temperature of phase transitions (tc). it was found that the dielectric constant increased with increasing the amount of nd in bnn matrix. room temperature energy storage property was determined using p-e hysteresis loops. the optimum discharge density was found for x= 0.7 with wrec = 18,1 mj.cm-3) at 1khz. keywords: tetragonal tungsten bronze, dielectric, energy storage. https://sites.google.com/site/tramp2019marrakech/ mailto:abdel.ilah.lahmar@u-picardie.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p20 is005 benefit of pressure in the sintering process alain largeteau1*, myhtili prakasam, oudomsack viraphong 1cnrs, univ. bordeaux, bordeaux inp, icmcb, umr 5026, f-33600 pessac, france email*/ largeteau@icmcb-bordeaux.cnrs.fr abstract pour atteindre certains objectifs, la conception de procédés originaux de synthèse dans la gamme de pression (1 bar – 60 kbar (6 gpa)) a mené à l’obtention de matériaux impossibles à élaborer par tout autre procédé. le service de synthèse hautes pressions (hp) étudie l’effet de p pour l’obtention de matériaux et la maitrise des transitions de phase. ces matériaux peuvent être sous forme de monocristaux, micro/nanocristallites, polycristaux (par frittage pour l’obtention de céramiques) et de monolithes (par densification et/ou consolidation de matériaux pulvérulents). le procédé hp est maitrisé sous forme gaz, liquide et solide; le milieu fluide en condition hydrothermale (état souscritique ou supercritique) permet par le biais du phénomène de dissolution-précipitation, la croissance de monocristaux et le frittage de poudres (céramiques, métalliques). l’impact de la pression au travers de ses principales caractéristiques (faible énergie mise en œuvre en comparaison avec la température (t), accroissement de la réactivité chimique, diminution du volume, force motrice) est étudié pour une grande variété de domaines d’applications : piézoélectricité, photonique, biomatériaux, outils d’usinage. des exemples de l’intérêt de la ression seront donnés pour les exemples suivants: diminution de t de frittage / consolidation / densification, par son effet de force motrice, afin de :  limiter la croissance granulaire,  favoriser la phase basse température : sio2 quartz (transition - à 573°c),  préserver la composition initiale du biomatériau (conservation d’éléments volatils: oh-, h2o, co2),  augmenter le domaine de stabilité thermique évitant la décomposition : bp [tdecomp. = 1130°c]: tfritt. = 1600°c/5 gpa, mgb2 [tdecomp. = 830°c]: tfritt. = 1200°c/5 gpa, orientation de la réaction chimique dans le sens de la synthèse conduisant à la phase la plus dense : diamant (c-c) au détriment du graphite (h-c), initiation d’une nouvelle microstructure plus fine par la maitrise des changements de phase (matériaux polymorphes) soit à l’état solide (al2o3:  -> ) ou bien soit à l’état liquide par dissolution d’une phase et précipitation d’une autre phase (sio2: amorphe -> cristallisé), frittage de matériaux réfractaires (borures, nitrures, carbures) pour atteindre une densité améliorée en comparaison avec les procédés à plus basse pression (c-sic), frittage de phase stable qu’à haute pression (c-c, c-bn), densification de céramiques avec une porosité proche de 0% (céramiques transparentes) ou à forte porosité (biomimétisme structure osseuse) divers procédés hp seront présentés pour la synthèse de matériaux / multimatériaux / composites sous forme dense (hp-ht, hp-sps, hys, hip, ..) et poreux (hys, fip, hip, cip, uap, ..), mais également pour l’obtention de matériaux sous forme de monocristaux (hycg, hys) et micro/nano-cristallites (hycr), la purification de matériaux naturels (hypu) et la décontamination athermique (sanitisation à froid: pascalization) de biocomposites dont l’un des constituants est thermo-instable (hhp, hpp) https://sites.google.com/site/tramp2019marrakech/ mailto:largeteau@icmcb-bordeaux.cnrs.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p21 is006 the role of mechanical fields and stress relaxation on amorphous/crystalline transition of nanoscale silicon nitride in -fe s.bordère* e-mail*/ sylvie.bordere@u-bordeaux.fr abstract the need to reduce the fuel consumption of vehicles, improve passenger safety and the new global standards for the co2 emission force the automotive industry to rapidly develop new materials with higher mechanical properties and lower density. the attractive properties of nanoscales si3n4 in terms of both density and strengthening make them excellent candidate for nitriding applications in the transportation industry. upon nitriding of fe-si binary alloys at 570°c, a very large amount of si3n4 forms in the -fe matrix as an amorphous phase of size-dependent cuboidal morphology whose density is very low (1.8 g. cm-3). upon denitriding at the same temperature, a transition from amorphous si3n4 to crystalline si3n4 was observed. this change in structure is associated with a change from the cube-like morphology to a hexagonal prism shape and an increase of density from 1.8 g. cm-3 to 3.6 g. cm-3. in this paper, the understanding of such an evolution was addressed through an approach based on numerical modelling that couples both stress field and the diffusion-controlled growth of nanoparticules of si3n4. the role of the anisotropy of stress fields, the elastic strain energy stored in the material, the pressure jump at the interface between si3n4/ -fe and the stress relaxation phenomenon on the stability of both amorphous and crystalline nanoparticles were discussed. the results obtained open new avenues for developing new lighter materials for transportation. https://sites.google.com/site/tramp2019marrakech/ mailto:sylvie.bordere@u-bordeaux.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p22 is007 design, microstructures and properties of high entropy alloys and complex concentrated alloys s. gorsse1*, f. perouzet1,2, d. hachet1,3, s. godet3, c. navone2, r. banerjee4, o. senkov5, d. miracle5 1univ. bordeaux, cnrs, bordeaux inp, icmcb, france. 2liten, cea, france. 3université libre de bruxelles, belgium. 4university of north texas, usa. 5air force research laboratory, usa. e-mail*/ sgorsse@gmail.fr abstract high entropy alloys (heas) and complex concentrated alloys (ccas) based on 3d transition metals (3d tm ccas) and refractory elements (rccas) are widely studied as candidates for structural and functional materials. 3d tm ccas usually have fcc or duplex fcc+bcc microstructures, while rccas usually have bcc-based phases. in fact, many 3d tm ccas and rccas have both disordered solid solution and long-range ordered phases, i.e. fcc+l12 and bcc+b2 respectively, giving the opportunity to produce precipitation-strengthened alloys. besides, low stacking fault energy fcc heas/ccas are susceptible to deformation twinning which imparts excellent strength-ductility combination by increasing strain hardenability. this talk steps back over the rapid development of heas/ccas to discuss their principles and the new concepts they introduce, their microstructures and properties, their design strategies, and will develop ideas to guide future efforts. we will also explore different processing routes with the aim to evaluate the effects on the microstructure and tensile properties of 3d tm ccas. https://sites.google.com/site/tramp2019marrakech/ mailto:sgorsse@gmail.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p23 is008 discovery of a feconipdcu high-entropy alloy with excellent magnetic softness wencka m1*. 1institute of molecular physics, polish academy of sciences ul. smoluchowskiego 17, 60-179 poznań, poland email*/ magdalena.wencka@ifmpan.poznan.pl abstract the author reports on the discovery of a magnetically soft high-entropy alloy of composition feconipdcu, which performs comparably to the best commercial soft magnets for static and low-frequency applications. properly heat-treated feconipdcu develops nanostructure that can be viewed as a two-phase bulk nanocomposite of randomly intermixed feconi magnetic domains and pdcu nonmagnetic “spacers”, both of 2–5 nm cross dimensions. due to the nanometric size, the feconi domains are magnetically single-domain particles, and since the particles are exchange-coupled across the boundaries, exchange averaging of magnetic anisotropy takes place, resulting in an almost vanishing coercive field and excellent magnetic softness. the formation of a two-phase nanostructure favorable for the exchange averaging of magnetic anisotropy is a consequence of specific values of the binary mixing enthalpies for the chosen elements. though high-entropy alloys are generally considered to be random solid solutions of multiple elements on a topologically ordered crystal lattice, clustering of the atoms into preferential chemical environments on a nanoscale essentially determines their magnetic properties. experimentally, the magnetic properties of the feconipdcu highentropy alloy are compared to the commercial, magnetically soft non-oriented silicon electrical steel [1]. keywords: high-entropy alloy, bulk nanocomposite, magnetism, magnetic softness references [1] p. koželj, s. vrtnik, a. jelen, m. krnel, d. gačnik, a. meden, m. wencka, j. leskovec, s. maiti, w. steuer, j. dolinšek: discovery of a feconipdcu high-entropy alloy with excellent magnetic softness, advanced ingineering materials 2019: 1801055 https://sites.google.com/site/tramp2019marrakech/ mailto:magdalena.wencka@ifmpan.poznan.pl third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p24 is009 magnetoelectric effect in chemically disordered perovskite multiferroics v. v. laguta1,2,3*, a. v. ragulya1,3 1institute for problems of materials science, national academy of sciences of ukraine, krjijanovskogo 3, 03142 kyiv, ukraine 2institute of physics as cr, cukrovarnicka 10, 162 53 prague, czech republic, 3nanotechcenter llc, krjijanovskogo 3, 03142 kyiv, ukraine email*/laguta@fzu.cz abstract multiferroics are materials having two or more order parameters (for instance, magnetic, electric or elastic) coexisting in the same phase. they have emerged as an important topic in condensed matter physics due to both their intriguing physical behaviors and a broad variety of novel physical applications they enable. the unique physical properties of multiferroics originate from the complex interactions among the structural, polar and magnetic long-range order parameters. in magnetoelectric (me) multiferroic materials, besides of the linear and biquadratic couplings of magnetic and electric order parameters, quadratic paramagnetoelectric (pme) effect should exist in the paramagnetic phase below the tc temperature of the paraelectric-toferroelectric phase transition, where the electric polarization is non-zero. in general, the quadratic me coupling is much less studied in magnetoelectrics than the linear coupling while the former one can be even larger than its linear counterpart in antiferromagnetic (afm) materials. large me coupling in afm multiferroics, especially in ceramic samples, are attractive for applications in me memory elements and spintronics as afm domains are almost unsusceptible to external magnetic fields that preserves well the stored information. the coupling between ferroelectricity and antiferromagnetism offers an intriguing possibility of electric field control and switching of afm domains. it is aim of this report to present results of comprehensive study of the me effect in chemically disordered perovskite multiferroics based on ferroelectric-antiferromagnets pb(fe1/2nb1/2)o3 [pfn] and pb(fe1/2ta1/2)o3 [pft]. usage of ceramic samples enables performing dielectric and me response measurements up to 400-500 k without marked influence of conductivity. however, main attention is paid to low (t<150 k) temperatures, where the me coupling coefficient is extremely large (as compared to the wellknown multiferroic bifeo3) and shows strong nonlinearity. we also present the results of me measurements in pfn ceramics with 900 and 1800 switching of electric polarization in the afm phase which demonstrate that the alignment of electric domains leads to corresponding alignment of magnetic domains. the behavior of the me coupling between disordered (dynamically or statically) spin ensemble and polarization in case of spin-glass or superparamagnetic phases was studied as well. extremely large me response is demonstrated in magnetoelectrics with superparamagnetic phase. phenomenological landau theory of phase transitions is used to explain experimental data. keywords: multiferroic, magnetoelectric, multifunctional material, magnetoelectric aknowledgement: this work was supported in part by the research executive agency (grant agreement 778072 — engima — h2020-msca-rise-2017). https://sites.google.com/site/tramp2019marrakech/ mailto:laguta@fzu.cz third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p25 is010 probing structural and magnetic properties of thin films by 57fe mössbauer spectrometry j. juraszek1*, f. appert, s. jouen, m. jean, l. diallo, l. lechevallier, a. fnidiki 1normandie univ., unirouen, insa rouen, cnrs, gpm, 76000, rouen, france email*/ jean.juraszek@univ-rouen.fr abstract in this talk, recent advances of 57fe conversion electron mössbauer spectrometry (cems) for the analysis of thin films will be presented. examples of applications will include various functional materials such as multiferroic thin films [1-2] and diluted magnetic semiconductors [3]. for multiferroic bismuth ferrite (bifeo3) thin films, we will show that both strain and magnetic field destabilize the cycloidal spin structure (figure 1), resulting in a critical magnetic field sharply reduced from the bulk value [4]. figure 1: mössbauer spectrum at 300 k of a 70-nm thick (001) bfo thin film grown onto gso substrate and corresponding cycloidal spin structure derived from the fit. this work is supported by the région normandie and the european regional development fund of normandy (erdf) through the "magma" project, and by the région normandie through the “tempo” project. references: [1] i.c. infante, j. juraszek, s. fusil, et al. , physical review letters 107, 237601 (2011). [2] d. sando, a. agbelele, d. rahmedov, et al. , nature mater., 12, (2013) 641–646. [3] m. l. diallo, l. diallo, a. fnidiki, et al., j. appl. phys. 122, (2017) 083905. [4] a. agbelele, d. sando, c. toulouse, et al., adv. mater. (2017) 1602327. keywords: thin film, multiferroic, mössbauer spectrometry, magnetism. https://sites.google.com/site/tramp2019marrakech/ mailto:jean.juraszek@univ-rouen.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p26 is011 electrocaloric effect in ferroelectric composites and domain structure yaovi gagou1* e-mail*/ yaogagou@gmail.com abstract climate global warming is becoming a very serious problem all over the world, so that everyone must play their part in helping to save our planet. it should be noted that industrial production alone generates nearly 51% of greenhouse gases. among these greenhouse gases, there are coolants used in cooling devices. freon and these analogs are also poisonous gases that are not environmentally friendly, so they must be disposed of in the future. the alternative will be to produce cooling based on the barocaloric (bce), magnetocaloric (mce), piezocaloric (pce)or electrocaloric effect (ece). physics based on these physical properties is gaining importance in order to replace the cooling gases with the solid material and the applications could take place massively in the near future, if the variation of the electrocaloric temperature approaches the 10 k for a material under a reasonable applied field. in this presentation, we investigated the electrocaloric effect of phase transition region in ferroelectrics in general and those based on batio3. at first, we were interested in the effect of doping to decrease curie temperature towards room temperature and then on the amplification of the ece. the first goal is reached. with regard to the amplification of the ece our work continues on the study of the grain size effect and the control of domain structure and the combination of ferroelectric materials. the obtained results on the ferroelectric composites based on bctl or btsr and the perspectives were highlighted. https://sites.google.com/site/tramp2019marrakech/ mailto:yaogagou@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p27 is012 mechanisms during thin film reaction and their influence on thin film properties alain portavoce1* e. assaf, l. patout, m. bertoglio, k. hoummada, c. alfonso, a. charaï, and s. bertaina 1im2np, cnrs-aix-marseille univ., faculté des sciences de saint-jérôme case 142, 13397 marseille, france email*/ alain.portavoce@im2np.fr abstract thin films are essential bricks of many nanostructures used in nanotechnology devices. for example, the gate of complementary metal oxide semiconductor (cmos) transistors is a stack of several nano-films of different electrical properties, typically: 20 nmthick sio2/ 5 nm-thick monocrystalline doped-semiconductor/ 2 nm-thick sio2/ 10 nm-thick hfo2/ 3 nm-thick tin/ 20 nm-thick highly-doped polycrystalline si/ 20 nm-thick silicide/ w 1st metallic contact. in order to get the desired properties, some layers composing the nanostructure need to be made of given phases containing several elements (given structure and composition). in this case, the desired phase needs to be grown after deposition, often using solid-state reaction. to this aim, several reaction processes can be used to form the phase of interest, such as thin-film reactive diffusion, which is a usual process in industry (“salicide” process in microelectronics for silicide growth, for example). however, the reaction process type is expected to influence the structure and the atomic distribution of the obtained layer, and thus, could modify the film properties. consequently, the growth process should be wisely chosen. this study presents the influence of two types of solid-state reaction, reactive diffusion (rd) and non-diffusive reaction (ndr), on the chemical, structural, and magnetic properties of ferromagnetic mn5ge3 and mncoge thin films, potentially interesting for gebased spintronics. in our case, rd-mediated growth is characterized by a strong initial composition gradient and “long-range” atomic transport during the film growth, while ndr takes place without composition gradient and without long-range atomic transport. the comparison of these two opposite methods illustrates the influence of atomistic processes taking place during solid-state crystal growth, such as atomic transport, on the properties of the obtained crystal. the results show also how the control of atomic transport could allow thin film properties to be modified. https://sites.google.com/site/tramp2019marrakech/ mailto:alain.portavoce@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p28 is013 dynamical properties of ferroelectric thin films and superlattices razumnaya a.g1*., linnik e.d., mikheykin a.s., tikhonov yu.a., lukyanchuk i.a. 1southern federal university email*/ agrazumnaya@sfedu.ru abstract ferroelectric thin films and artificial superlattices composed of alternating ferroelectric layers usually exhibit better functional parameters than bulk materials of the same compositions or even can have new properties, not reachable in the bulk. epitaxial ba0.5sr0.5tio3 (bst0.5) thin film, bi-color artificial batio3/ba0.5sr0.5tio3 (bt/bst) and tri-color batio3/ba0.5sr0.5tio3/srtio3 (bt/bst/st) superlattices were grown on cubic single crystal (001)mgo substrates by pulsed laser deposition using alternating focusing of the laser beam on stoichiometric bt, bst, and st targets. the biand tri-color superlattices were symmetric with the modulation periods of λ = 135 å and 143 å, consequently. the total thickness of the grown bt/bst and bt/bst/st superlattices was 1000 nm, while that of the bst-film was 600 nm. for comparison, the ba0.5sr0.5tio3 (bst05) ceramics sample was prepared by conventional solid-state reaction method from stoichiometric mixtures of baco3, srco3, and tio2 raw materials. the structural parameters of the layers were determined by x-ray diffraction. nearand subterahertz dynamics of soft and debye-type central modes was studied by the polarized raman spectroscopy of the bt/bstx superlattices in the temperature range of 80-500 k. based on the temperature dependence of the polar modes we revealed the phase transitions temperatures in the studied heterostructures. in the sub-thz frequency range of the xz spectra, we observed the coexistence of the debye-type central peak and soft mode in bi-color batio3/ba0.5sr0.5tio3 superlattice. this work was supported by internal grant no. vngr-07/2017-23 of southern federal university, russia, and by h2020-rise-engima action keywords: ferroelectrics, raman spectroscopy, lattice dynamics, crystal structure, phase states https://sites.google.com/site/tramp2019marrakech/ mailto:agrazumnaya@sfedu.ru third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p29 is014 contribution to the improvement of light emitting diodes based on nitrides z. benzarti khalfallah1* 1laboratoire des matériaux multifoncionnels et applications (lamma), département de physique, faculté des sciences de sfax, université de sfax, route de soukra km 3,5 b.p. 1171 – 3000 sfax, tunisie. email*/ zohra.benzarti@gmail.com abstract nowadays, the commercial success of light-emitting diodes (leds) has encouraged researchers to focus on the achievement of even higher efficiency optoelectronic devices. however, the improvement in the performance of leds is limited by some issues related to the active region and template properties, which have to be ameliorated. commonly, sapphire substrates are used for the nitride material growth. nevertheless, the large mismatch with nitride templates is considered as a source of significant number of defects, which reduce led’s luminescence. in order to overcome these drawbacks, we have proposed novel technology, so-called “sin treatment”. this technique has been proved to be very promising method for nitride material growth. it is a simple and cost effective technology, which introduces a randomly in-situ sin nano-masking on sapphire substrate. we have elaborated si-doped gan template layer and nitride-based multiple quantum well (mqw) light-emitting diodes with gan buffer layer using sin treatment by metalorganic vapor phase epitaxy (movpe). it is shown that optical properties of ingan/gan mqws depend on the defect density of elaborated templates. thereafter, we report an enhancement of the emission of mqw leds using sin treatment, compared to the mqw led emissions deposited on a conventional gan buffer layer. keywords: gan, movpe, sin treatment, leds. https://sites.google.com/site/tramp2019marrakech/ mailto:zohra.benzarti@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p30 orals https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p31 or001 wear and friction behavior of the porous tinicu alloy for biomedical application latifa k. 1*, hacène c.1, abednour h.1, soumaya m.2 1 national school of mines and metallurgy, annabaalgeria 2 research center in industrial technologies crti, algiersalgeria e mail*/ latifabiomat@gmail.com abstract porous tinicu alloys are used in wide and different engineering applications due to their excellent mechanical properties such as ductility, strength, toughness, etc. also, these alloys have a good resistance to corrosion and the excellent biocompatibility properties, the demands increased to use it in different medical applications. the biomedical application of these alloys requires good structural and surface biocompatibility. it is characterized by the damage caused by the implant-tissue interaction. this damage is related to products released by friction. for this purpose, the objective of this work is the study of the tribological behavior of porous tinicu alloys, using two static partners: alumina ball and bone pion.in this research work, porous tinicu alloys were prepared from the pre-alloyed powders. the milling was realised using a planetary ball mill for 10 hours an under argon atmosphere. the the milled tinicu powders were then sintered at temperatures of 950°c for 7h.the results of the investigation confirm that wear degradation is manifested by the abrasive mechanism for both partners. the addition of copper improves the tribological properties of the alloys developed by decreasing the coefficient of friction. keywords: tinicu alloys, sintering, wear. https://sites.google.com/site/tramp2019marrakech/ mailto:latifabiomat@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p32 or002 design of a bio-flexible piezoelectric nanogenerator for biomechanical energy harvesting z. hanani a,b,*, d. mezzane a, m. amjoud a, m. lahcini c, y. gagou d, h. ursic e, a. jamali f, n. novak e, s. fourcade b, m. el marssi d, z. kutnjak e and m. gouné b a lmcn, cadi ayyad university, marrakesh, 40000, morocco b icmcb, university of bordeaux, pessac, 33600, france c lco2mc, cadi ayyad university, marrakesh, 40000, morocco d lpmc, university of picardy jules verne, amiens, 80039, france e jožef stefan institute, ljubljana, 1000, slovenia f pme, university of picardy jules verne, amiens, 80039, france e-mail*/ zouhair.hanani@edu.uca.ma abstract over the last decade, the research and development of piezoelectric and sensing devices based on functional piezoelectric materials has made significant progress 1. piezoelectric nanogenerators (ngps) are increasingly becoming a new energy conversion source with promising capabilities for mechanical energy harvesting using piezoelectric materials at the nanoscale 2. so far, the market for piezoelectric devices is largely dominated by lead-based generators based on pzt (pbzr1-xtixo3) systems because of their excellent piezoelectric properties. however, lead is toxic and harmful to the environment and our health 3. consequently, it is highly desirable to develop environmentally friendly piezoelectric materials whose piezoelectric properties would be comparable to those of lead-based components 4. in this regard, lead-free ceramic ba0.85ca0.15zr0.10ti0.90o3 (bczt) with excellent dielectric, ferroelectric and piezoelectric properties were embedded in the biodegradable polylactic acid (pla). bczt fillers were elaborated by low-temperature hydrothermal route and functionalized via core-shell structuration using polydopamine layer (pda). bczt/pla nanocomposite films were elaborated by solvent casting method. the core-shell structuration of bczt particles leads to an enhancement of the dielectric, ferroelectric and energy storage performances. finally, bczt/pla eco-friendly and bio-flexible nanogenerator was designed to have an insight on the output performances. keywords: lead-free ceramic, biodegradable polymer, nanocomposite, piezoelectric nanogenerator, energy storage. references 1 k. il park, c.k. jeong, j. ryu, g.t. hwang, and k.j. lee, adv. energy mater. 3, 1539 (2013). 2 m.a. parvez mahmud, n. huda, s.h. farjana, m. asadnia, and c. lang, adv. energy mater. 8, 1 (2018). 3 binoy bera, imp. j. interdiscip. res. 2, (2016). 4 z. hanani, d. mezzane, m. amjoud, a.g. razumnaya, s. fourcade, y. gagou, k. hoummada, m. el marssi, and m. gouné, j. mater. sci. mater. electron. 30, 6430 (2019). https://sites.google.com/site/tramp2019marrakech/ mailto:zouhair.hanani@edu.uca.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p33 or003 photocatalytic and photoluminescent properties of a system based on smpo4 nanostructure phase a. bouddouch1, 2, *, a. baabou2, e. amaterz1, 3, a. taoufyq1, b. bakiz1, j. c. valmalette2, f. guinneton2, s. villain2, a. benlhachemi1 (1) laboratoire matériaux et environnement (lme), faculté des sciences, université ibn zohr, b.p 8106, cite dakhla, agadir, maroc. (2) institut matériaux microélectronique et nanosciences de provence, université de toulon, aix marseille univ, cnrs, im2np, toulon, france. (3) institut de thermique, mécanique, matériaux (ithemm), université de reims champagne-ardenne, reims, france. email*/ abdo.bouddouch@gmail.com abstract in the present work, we investigate the structural, microstructural, vibrational, photocatalytic and luminescence properties of the system smpo4 thermally treated at 900 °c. polycrystalline sample was elaborated using a coprecipitation technique. the sample was then characterized using x-ray diffraction, scanning electron microscopy, infrared spectroscopy, raman spectroscopy and photoluminescence analyses under uv excitation. xray diffraction profile analyses showed that the monoclinic phase p21/n was observed. the scanning electron microscopy experiments showed a homogeneous distribution of morphologies and indicated that smpo4 was in nano-sized particle. attributions of raman and ftir vibrational modes were proposed. for the photocatalytic activity, uv-visible spectrophotometer has used to analyze the evolution of photodegradation of rhodamine b. photoluminescence (pl) properties of smpo4 nanoparticle has been investigated and reported. keywords: samarium phosphate smpo4, luminescence properties, co-precipitation technique, photocatalytic activity, diffraction techniques, spectroscopy methods. acknowledgments this project was financially supported by campus france (phc toubkal 2018 (french-morocco bilateral program) grant number: 38999we). https://sites.google.com/site/tramp2019marrakech/ mailto:abdo.bouddouch@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p34 or004 highly textured ge(sn) thin films grown by magnetron sputtering on si(100) h. khelidj1,3*, a. portavoce1, k. hoummada2, m. bertoglio1, m. c. benoudia3, d. mangelinck1 1cnrs, im2np, faculté des sciences de saint-jérôme case 142, 13397 marseille, france 2aix-marseille université, im2np, faculté des sciences de saint-jérôme case 142, 13397 marseille, france 3ecole nationale supérieure des mines et de la métallurgie, l3m, annaba, algeria adresse /e-mail : im2np, faculté des sciences de saint-jérôme case 142, 13397 marseille, france email*/ hamza.khelidj@im2np.fr abstract cmos si-photonics is currently considered as a key technology for the development of the future generation of communication systems. in particular, ge(sn) semiconductor alloys have received increasing attention since it should allow the integration of laser in the cmos technology [1], which is an essential brick still missing in si photonics technology. indeed, ge(sn) films are expected to be compatible to the cmos technology, and to exhibit a direct bandgap for sn concentrations higher than 10 at.%. furthermore, ge(sn) should possess carrier mobility exceeding both the carrier mobility in ge and si. however, the low sn solubility in ge ( 1 at%) and the large lattice mismatch between α-sn (6.489 å) and ge (5.646 å) or si (5.431 å), complicate the epitaxial growth of sn-rich ge(sn) layers on si substrates. growth techniques, such as chemical vapor deposition (cvd) and molecular beam epitaxy (mbe), were shown to be able to grow sn-rich ge(sn) thin films in epitaxy on si(001) substrate, exhibiting good crystalline properties [2]. nevertheless, magnetron sputtering is one of the cmos-compatible techniques the most cost-effective for mass manufacturing. this technique was shown to be able to produce ge(sn) thin films deposited on si or ge with reasonable electrical properties and high sn concentration, allowing for the production of efficient ge(sn)-based devices [3]. the present work aimed to study ge(sn) thin film elaboration on si(100) substrate, using magnetron sputtering. ge1−xsnx thin films with 0.04 ≤ x ≤ 0.13 were deposited at room temperature (rt) or at 360 °c on si(100) substrates, with or without the pre-deposition of a ge buffer. the film growth kinetics was studied by in-situ xrd, while the film microstructure was investigated using xrd and sem, and their surface state was studied by afm. in situ xrd measurements show a strong kinetic competition between ge(sn) crystallization and sn incorporation, complicated by sn melting and de-wetting, limiting the possibilities of ge(sn) layer production. ge and sn phase separation can lead to strongly inhomogeneous layers, with probably amorphous ge inclusions. however, sn selective etching using a 5% hf solution can be used to improve the surface state of the films. rt deposition leads to the growth of polycrystalline ge(sn) layers, while the subsequent deposition of a ge buffer and the ge(sn) film at 360 °c allows the growth of a strongly textured ge(sn) layers, probably in epitaxy on the si(001) substrate, with a good surface state and a high sn incorporation (~ 13 at%). key words: si photonics, cmos, ge(sn), magnetron sputtering, epitaxy. references: [1] h. pérez ladrón de guevara, a.g. rodríguez, h. navarro-contreras, m.a. vidal, determination of the optical energy gap of ge1−xsnx alloys with 0<x<0.14, appl. phys. lett. 84 (2004) 4532. [2] r. r. lieten, j. w. seo, s. decoster, a. vantomme, s. peters, k. c. bustillo, e. e. haller, m. menghini, and j.-p. locquet, tensile strained gesn on si by solid phase epitaxy, applied physics letters 102, 052106 (2013). [3] j. zheng, s.wang, z. liu, h. cong, c. xue, c. li, y. zuo, b. cheng, and q. wang, gesn p-i-n photodetectors with gesn layer grown by magnetron sputtering epitaxy, applied physics letters 108, 033503 (2016). https://sites.google.com/site/tramp2019marrakech/ mailto:hamza.khelidj@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p35 or005 dielectric and energy storage study for the ito/bife0.95mn0.05o3/srruo3/srtio3 heterostructure s. yousfi1,2*, h. bouyanfif1, j. belhadi1, j.l dellis1, l. bih2, m. el marssi1 1laboratoir de physique de la matière condensée, université de picardie jules verne, 33 rue saint leu, 80000, amiens, france. 2département matériaux et procédés, ensam meknès, université moulay ismail, marjane 2,b.p. 15290 almansor, meknès, maroc. e-mail*/said.yousfi1@gmail.com abstract during the last years, multiferroic materials have gained great attention due to their fundamental physics and possible integration in advanced applications, especially in energy storage. bifeo3 (bfo) appears actually as one of the most interesting, because it shows multiferroic properties at room temperature. the lack of dielectric study in the bfo thin film present an obstacle to this integration. to remedy this, a bfo thin film was elaborated by pulsed laser deposition, and a dielectric dependency in frequency and temperature is investigated. the dielectric relaxation study, noticed two origins, the translational hopping process, and the dipole frictional losses. the energy storage is deduced from the measured polarization hysteresis loop. keywords: energy, dielectric, thin film, multiferroic. https://sites.google.com/site/tramp2019marrakech/ mailto:said.yousfi1@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p36 or006 lacoo3 thin films as gas sensor m. jędrusik1,2*, a. kopia2, c. turquat1, madjid.arab1, c. leroux 1. 1univ toulon, aix marseille univ, cnrs, im2np, toulon, france, 2agh university of science and technology, wimiip, kraków, poland e-mail*/ jedrusik@agh.edu.pl abstract gas sensors recently attracted attention of researchers for application in harsh environment for example in car industry [1]. electrochemical sensors with perovskite lacoo3 sensing electrodes deposited on yttrium stabilized zirconia (ysz) is promising configuration. cubic ysz is a well-known ionic conductor widely used in gas sensor application. in literature there is few works concerning tetragonal ysz as ionic conductor in gas sensor. tetragonal phase is characterized by high chemical stability and high mechanical properties. perovskites are popular sensing materials [2]. in this work thin films of lacoo3 were deposited on ysz (9,5 % mol) and (3,5%) substrates by pulsed laser deposition (pld) method at 750 °c and 850 °c in presence of oxygen. the sensors are in the configuration lacoo3/ysz/pt and will be used for the detection of nox gases. the influence of the deposition temperature and of nature of the substrate on the morphology of the sensing electrodes (lacoo3 thin films) was investigated by transmission electron microscopy (tem) x ray diffraction (xrd) scanning electron microscopy (sem). the resistance variation of lacoo3 layers under no2 was also tested. sensors were exposed to various concentration of no2 in the temperature range 25 °c 700 °c. keywords: gas sensors, thin films, lacoo3, pld, no2 references [1] miura n., sato t., anggraini s.a.,ikeda h., zhuyikov s., ionics, 20, 901-925, (2014) [2] i.waernhus, t.grande, k.wiik, topics in catalysis, 54, 1009-1016, 2011 https://sites.google.com/site/tramp2019marrakech/ mailto:jedrusik@agh.edu.pl third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p37 or007 hybrid thin films for catalytic degradation of dyes akram s1, 2*, michael l1, dhouha g2, martial c1, habib b2. 1 laboratoire de physique de la matière condensée, ufr des sciences, université de picardie jules verne, amiens, france. 2 laboratoire des matériaux avancés et phénomènes quantiques, faculté des sciences mathématiques, physiques et naturelles de tunis, université de tunis el manar, tunis, tunisie. email*/ akram.sakli@gmail.com absract during the past twenty years, oxidation techniques have been emerged as new processes for treat of wastewater containing high concentration of non-biodegradable and / or toxic pollutants. photocatalytic degradation is one of these techniques which is capable whether partially or completely mineralizing various organic molecules. titanium dioxide tio2 is the most widely used as photocatalyst, because of its photo-stability and low costs, however, the photocatalytic efficiency of this material is limited by the fact that its particles are harmful [1] for biological bodies. a new promising material is based on hybrid composite of bismuth oxide and carbon deposited on thin films using spin coating and pecvd techniques. in this work, we present a brief description of the microstructure of the deposited thin films and the results of photodegradation tests carried out on indigo carmine and methyl orange dye solutions diluted in distilled water. the results showed a total discoloration of the solutions, thus a loss of associated chromophores. the apparent kinetics of the discoloration reactions were calculated basing on the langmuir hinshelwood model and studied according to the different deposition parameters of our bioc films. keywords: catalytic degradation, dye, thin film, titanium dioxide, apparent kinetics. references [1] m. shakeel et al, biological trace element research, volume 172, issue 1, pp 1-36, july 2016. toxicity of nano-titanium dioxide (tio2-np) through various routes of exposure: a review. https://sites.google.com/site/tramp2019marrakech/ mailto:akram.sakli@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p38 or008 effect of the wo3/nb2o5 ratio on the structural, electrical and energy storage properties of bao–na2o– nb2o5–wo3-p2o5 glass–ceramics a. ihyadna*, a. lahmarb , d. mezzanea, l. bihc,d, a. alimoussaa, m. amjouda, m. el marssib, i.a. luk’yanchukb. alaboratory of condensed matter and nanostructures, cadi ayyad university, marrakesh, morocco b condensed matter physics laboratory, university of picardie jules verne, amiens, france cdépartement matériaux et procédés, ensam meknès, université moulay ismail, meknès, maroc. d equipe physico-chimie la matière condensée (pcmc), faculté des sciences de meknès, maroc. e mail*/ ihyadn.abderrahim@gmail.com abstract ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. in this context, new phosphate glass-ceramics 2bao-0.5na2o–2.5[(1-x)nb2o5–xwo3]-1p2o5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated b0, b1, b2, b3, b4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °c for 10 hours. subsequently, the obtained glass-ceramics were studied by differential scanning calorimetry (dsc), x-ray powder diffraction (xrd), raman and impedance spectroscopy. all of these techniques allowed the identification of ba2na4w2nb8o30 phase with tungsten bronze structure embedded in the glassy matrix. the density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x =0.3 and then decreases. dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. the dielectric constants of all the samples exhibited excellent stability from 25 °c to 150°c °c and low dielectric losses less than 0.03. room temperature energy storage property which depends on the composition x, was performed using p-e hysteresis loops of the glass-ceramics. the optimum recoverable density of 25.6 mj/cm3was obtained for b3 with an energy efficiency of 73.77% under the electric field of 90kv/cm. keywords: phosphate; glass-ceramics; structural and dielectric properties; energy storage; wo3. https://sites.google.com/site/tramp2019marrakech/ mailto:ihyadn.abderrahim@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p39 or009 electrical transport properties of multi-contact interfaces and spots numerical imaging from surface profilometry s. ait mohamed 1,3*, b. jonckheere 1,2, r. bouzerar1 1lpmc, université de picardie, france 2sncf, france 3ikos consulting, france e-mail: aitmedsab@gmail.com abstract though widely used in many industrial applications, discrete interfaces arising from contacting metal pieces are poorly understood. that field has attracted the attention of most engineers or researchers to respond to the acute need for a better understanding of both the physical and mechanical processes acting within such interfaces and open new ways to the control and optimization of these interfaces. the major obstacle to a physical understanding of such interfaces originates from their structural and functional complexity. due to their discreteness consisting of a sparse array of mechanical spots with typically micron size scales, their structural complexity is tightly connected to the random surface geometry of the contacting materials. on the opposite side, their functional complexity regards multiphysical aspects such as the strongly coupled thermal and electrical transport properties and their sensitivity to the mechanical conditions imposed to the interface. the mechanical spots contribute the electrical properties both individually through their shape and size and collectively through their elastic interactions. the interface structure is a basic knowledge which allows computing its transport properties whenever a model of electron transport is available. our approach to discrete interfaces relies on the prior determination of the interface structure from surface profilometry and numerical imaging of the spots. the surface profiles data processing with a specific numerical code provides the spots array, its evolution with the compression force, the statistical spots sizes and shapes distribution as well as the mechanical stresses. the electrical properties are extracted from the numerical simulation of an electron transport model restricted to constriction effects. in a second step, these predictions are compared to electrical and mechanical stresses data obtained on copper/copper interfaces allowing the validation of the numerical model and a further interpretation of the physical processes acting within the contact. simulation of the mechanical contact between a cooper plate and a flat rigid surface https://sites.google.com/site/tramp2019marrakech/ mailto:aitmedsab@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p40 or010 multilayer devices from thin films obtained by tape casting ivanchenko s*., umerova s., baranovskyi d., kovalenko o., ragulya a nanotechcenter llc / frantsevich institute for problems of materials science nasu krzhizhanovsky str., 3, ukraine, 03142, kyiv e-mail*/ sergonische@gmail.com abstract creation of thin batio3 tapes for use as a dielectric layers in ceramic multilayer capacitors is a challenging goal because it is the most efficient way to increase an mlcc capacity. the use of nanopowders as the basis for tapes is promising because it allows obtaining of films with low thickness and roughness close to the linear dimensions of one nanoparticle. it is a guarantee of improving the performance of multilayer devices without increasing their size, which is consistent with the tendency of miniaturization. adaptation of high productive film formation method like tape casting to create layers with thickness of less than 1 µm from an affordable electrotechnical materials is a promising and challenging goal. the batio3 nanopowder was used to create tapes of dielectric layers and a mix of ni/nio powders was used for conductive layers. tapes with the thickness from 5 µm to less than 1 µm were created by the tape casting method. the rheological behavior of all casting suspension was studied and casted tapes were characterized. surface roughness comparable with the diameter of 1 particle was achieved. from obtained tapes, a few types of multilayer composites with different layers thickness were assembled using isostatic lamination. obtained multi-layer composites were successfully annealed and sintered without cracking or delamination. keywords: tape casting, thin films, mlcc, nanopowders, sintering. https://sites.google.com/site/tramp2019marrakech/ mailto:sergonische@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p41 or011 effects of concentration and temperature on the rheological properties of nanofluide graphene / slideway oil 1cadi ayyad university, ens marrakech, team nanostructures of physics, morocco email*/abderrahim.bakak@gmail.com abstract nanofluids are colloidal solutions composed of particles with nanometric size, suspended in a liquid. their astonishing thermal properties have been the subject of intense investigation during the last decade. in this study, the effects of the volume fraction of graphene nanopowder and temperature were studied on the rheological properties of the slideway oil as a base fluid. for this purpose, nanofluids based on graphene were prepared using a twostep process. in addition, in order to evaluate the morphology and the stability of the nanoparticles, a scanning electron microscope analysis was performed on these samples. the results of the sem analysis indicated a uniform dispersion of nanoparticles. in addition, the results of the experiments indicated that with increasing temperature, the viscosity of the nanofluid decreases. in addition, it has been found that the dynamic viscosity of the nanofluids, having a solid volume fraction of less than 1%, is lower than that of the base fluid. for fractions from 1%, the dynamic viscosity of the nanofluid increases with the solid volume fraction. finally, the addition of these nanoparticles can also modify the newtonian behavior of the base fluid, and then the behavior of the nanofluids strongly depends on the volume fraction in nanoparticles. keywords: graphene, slideway oil, nanofluid, viscosity, rheological properties, volume fraction, temperature https://sites.google.com/site/tramp2019marrakech/ mailto:abderrahim.bakak@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p42 or012 interactions between transformations during intercritical annealing of a high-formability steel arthur marceaux dit clement1,2,*, khalid hoummada1, josée drillet2, véronique hebert2, philippe maugis1 1aix marseille univ, cnrs, im2np, marseille, france 2arcelormittal maizières research sa, maizières-les-metz, france e-mail*/ arthur.marceauxditclement@arcelormittal.com abstract high strength steels are widely used in the automotive industry to help reduce the average weight of vehicles without compromising passengers safety [1]. manufacturing these steels involves a cold-rolling step before intercritical annealing, during which a certain volume fraction of austenite is formed. the austenite decomposes upon cooling into several products (usually martensite) and gives the steel its final microstructure. the steel mechanical properties are dependent on the volume fraction of the phases composing the microstructure, but also on their chemistry, their morphology and their spatial distribution. this latter property is essential to ensure good formability. consequently, it is of prime importance to not only understand how austenite forms during intercritical annealing, but also where. during intercritical annealing, several transformations occur simultaneously, such as recrystallization, cementite precipitation, microalloying elements precipitation and austenite formation. these transformations interact with each other [2–5]. for example, microalloying elements hinder recrystallization [5], whereas incomplete recrystallization tends to accelerate austenite formation kinetics and leads to banded microstructures [2,4]. in this study, we used a model for microstructural evolutions during intercritical annealing to show how these transformations interact with each other, and how cementite precipitation, often neglected in available literature, should be considered to properly model recrystallization and austenite formation kinetics. keywords: cementite, recrystallization, precipitation, austenite, intercritical annealing references [1] o. bouaziz, h. zurob, m. huang, steel res. int. (2013) 937–947. [2] j. huang, w.j. poole, m. militzer, metall. mater. trans. a 35 (2004) 3363–3375. [3] h. azizi-alizamini, m. militzer, w.j. poole, metall. mater. trans. a 42 (2011) 1544–1557. [4] r.r. mohanty, o. girina, n. fonstein, metall. mater. trans. a 42 (2011) 3680–3690. [5] m. bellavoine, m. dumont, j. drillet, v. hébert, p. maugis, metall. mater. trans. a 49 (2018) 2865–2875. https://sites.google.com/site/tramp2019marrakech/ mailto:arthur.marceauxditclement@arcelormittal.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p43 or013 obtaining pure stoichiometric lead titanate with size control o. kovalenko 1,2*, s. skapin3, m. macek krzmanc3, d. vengust3, s. umerova1,2, s. ivanchenko1,2, d. baranovsky1,2, m. spreitzer3, a. ragulya1,2 1institute for problem of material science nanu, 2nanotechcenter, 3jozef stefan institute email*/ olgiuskovalenko@gmail.com abstract lead titanate (pbtio3) is a well-known material for its unique ferroelectric and piezoelectric properties. despite on the toxicity of the pb-content material it still attracts high attention due to the wide spectrum of the properties such as switchable polarization, piezoelectricity, high non-linear optical activity, pyroelectricity and high dielectric behavior. due to the toxic nature of the pbo volatile material at high temperature and problems connected with large lattice distortion during cubictetragonal phase transition around 773 k, it’s important to reduce the synthesis temperature. in this context synthesis method and condition, which has the crucial role on the temperature, should be well matched. there’re various methods of pbtio3 nanopowders preparation such as conventional mixed-oxide, mechanochemical synthesis, pechini-type processes, hydrothermal process, sol-gel processing. among them, the most appropriate in context of phase purity, stoichiometry precise control, particle size, homogeneity and production effectivity, is pechini method, thermal decomposition of the organic precursor. crucial role in the obtaining product with desire characteristic in this method is determination of the precursor optimal precipitation condition and optimizing the heat treatment condition of its precursor. in present work pbtio3 with tetragonal structure was obtained with pechini and hydrothermal methods. the effect of lead titanyl oxalate precipitation conditions (starting reagents, ph, c solution) and precursor thermal decomposition mode on the final decomposition temperature and morphology of lead titanate nanopowders were investigated. thermogravimetric analysis of lead titanil oxalate was performed to investigate the optimal calcification regime. hydtothermal method of pbtio3 obtaining was used to compare with pechini method in view of morphology characteristic. the obtained powders of lead titanate were analyzed by scanning electron microscopy and x-ray analysis. the optimal mode of calcination of lead titanate oxalate has been determined, taking into account the variety and low melting point of lead oxides in order to obtain the pure phase of lead titanate. the final temperature for the pbtio3 crystallization is 823 к. the sizes of the pbtio3 nanoparticles obtained with pechini and hydrothermal methods are 8-75 nm (with aggregate sizes of 166-500) and 83-333, respectively. comparison of hydrothermal method and pechini methods in terms of morphology control for pbtio3 obtaining was performed keywords: lead titanate, pechini method, hydtothermal method, size control https://sites.google.com/site/tramp2019marrakech/ mailto:olgiuskovalenko@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p44 or014 elaboration of thermoelectric mg-ag-sb thin films n. oueldna1,2,*, a. portavoce1 , m. bertoglio1, a. kammouni2, and k. hoummada1 1im2np, cnrs/aix-marseille university, faculté des sciences de saint-jérôme case 142, 13397 marseille, france 2lasmar, university of moulay ismail, faculté des sciences 11 201 meknes, maroc e-mail*/ nouredine.oueldna@im2np.fr abstract the increase of functionality of mobile technologies leads also to an increase of energy consumption, limiting the autonomy of mobile devices. in this context, new technologies allowing for environmental energy harvesting (eh) are currently investigated. these eh devices should allow the autonomy of mobile devices to be extended by either partially recharging the battery of the device or allowing some operations to be performed without using the energy stored in the battery. in the case of technologies such as micro-sensors, microelectronics integrated circuits (ic) etc. for which part of the energy is thermally lost, the integration of thermoelectric devices appear as a potential eh solution. in this case, the integrated thermoelectric device should be based on nanostructures, such as thin films, elaborated with industrial processes compatible with the complementary metal oxide semiconductor (cmos) technology [1], and the material workingdomain should be around room temperature. bisbte and bi2te3 are known as the best compounds operating at room temperature [2-3]. however, these materials are toxic and scarce, motivating the development of alternative materials. the ternary compound α-mgagsb was recently shown as a serious potential candidate for roomtemperature thermoelectric applications. it is a less-toxic p-type thermoelectric material exhibiting a zt ~ 1 close to room temperature, which can be increased by doping [4]. however, this material was only studied in its bulk state, using elaboration methods incompatible with cmos technology. in this work, the elaboration of mgagsb thin films by cmos-compatible magnetron sputtering is investigated for the first time. the film microstructure is characterized by as x-ray diffraction and scanning electron microscopy, and compared to the film seebeck coefficient measured between −50 and +50 °c. keywords: thermoelectric materials, mg-ag-sb, thin film, seebeck coeficient references [1] j. a. kittl et al., “silicides and germanides for nano-cmos applications,” mater. sci. eng. b solid-state mater. adv. technol, 2008. [2] b. poudel et al., “high-thermoelectric performance of nanostructured bismuth antimony telluride bulk alloys,” science, 2008. [3] h. j. goldsmid, “bismuth telluride and its alloys as materials for thermoelectric generation,” materials (basel)., 2014. [4] liu, z., et al. “high thermoelectric performance of α-mgagsb for power generation.” energy environ. sci., (2017). https://sites.google.com/site/tramp2019marrakech/ mailto:nouredine.oueldna@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p45 or015 the effect of sn doping on structural, ferroelectric, dielectric and electrocaloric properties of ba0.9sr0.1tio3 h. zaitouni1,*, l. hajji1, d. mezzane1, e. choukri1, a. alimoussa1, k. hoummada2, y. gagou3, b. rožič4, m. el marssi3, z. kutnjak4 1laboratory of condensed matter and nanostructures (lmcn), cadi-ayyad university, faculty of sciences and technology, department of applied physics, marrakech, morocco. 2laboratoire matériaux et microélectronique nanosciences de provence, umr 7334, aix marseille universitécnrs, faculté des sciences service 142, 13397 marseille cedex 20, france. 3laboratoire de physique de la matière condensée (lpmc), université de picardie jules verne, 33 rue saint-leu, 80039 amiens cédex, france. 4laboratory for calorimetry and dielectric spectroscopy, condensed matter physics department, jozef stefan institute, ljubljana, slovenia. e mail: hajarzaitouni88@gmail.com abstract the lead-free ferroelectric materials ba0.9sr0.1ti1-xsnxo3 with x = 0, 0.02, 0.05, 0.07, 0.10 and 0.15 (abbreviated as bsts) were prepared using the conventional solid-state method. the effect of sn substitution on the crystal structure, ferroelectric behavior, dielectric and electrocaloric properties of bsts ceramics have been systemically investigated. the x-ray diffraction (xrd) patterns show that the samples have well crystallized into perovskite structure suggesting the substitution of ti4+ by sn4+ in bst lattice. with increasing sn-content, the enhancement of the dielectric permittivity was observed for (0≤x≤0.10) and the ferroelectric transition temperature (tc) was found to shift towards the room temperature (tc = 33°c for x = 0.10). a typical p–e hysteresis loops were observed for the investigated compositions and they were confirmed the ferroelectric-paraelectric phase transition. electrocaloric effect (ece) of bsts ceramics was studied by using the indirect method from pe hysteresis loops using the maxwell relation. keywords: bsts ceramics, electrocaloric effect (ece), x-ray diffraction, ferroelectric. https://sites.google.com/site/tramp2019marrakech/ mailto:hajarzaitouni88@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p46 or016 phase formation between ni thin films and inas substrate s. rabhia,b, c. perrin-pellegrinoa*, l. patouta, m.c. benoudiab , a. charaïa, k. hoummadaa a institut matériaux microélectronique nanosciences de provence (im2np), aix-marseille université (amu), france b laboratoire mines métallurgie matériaux (l3m), ecole nationale supérieure des mines et de la métallurgie (ensmm), annaba, algérie. e-mail*/ carine.perrin-pellegrino@im2np.fr abstract as conventional si cmos scaling approaches the end of the roadmap, iii-v based mosfets are seriously being considered as an alternative technology to continue moore’s law.[1] to realize high-performance iii-v mosfets, reliable contact metals for s/d with low contact resistance is essential, especially in highly scales devices [2]. an atomic level understanding of the metal-semiconductor solid-state reaction can shed light on material-electronic property interactions at nano-scale, especially when the intentional or unintentional defects are present. the best candidate as iii-v material is the solid solution ingaas, with the adequate proportion in order to be able to grow in epitaxy with si. despite the large interest for this material, fundamental studies on the metal reaction have principally focused on gaas and very few on inas. we have focused our research on this last ternary system (ni/inas). ni has been deposited on inas(100) substrate to form a 100 nm thick film. the first phase formed during the solid state reaction has been identified as ni3inas with a nias hexagonal structure. it grows in epitaxy from an initial layer formed as deposit. the ternary phase is stable up to 250°c but from this temperature a new phase appear. the solid state reaction has been followed by in situ x-ray diffraction and the phase formed during the first stage has been characterized carefully using hrtem. the relation of epitaxy between the phase and inas substrate has been established and is different from the one found for the similar system ni/gaas. references [1] takagi, s.; takenaka, m. in high mobility material channel cmos technologies based on heterogeneous integration, junction technology (iwjt), 2011 11th international workshop on, ieee: 2011; pp 1-6 [2] chueh, y.-l., et al. (2008). "formation and characterization of nixinas/inas nanowire heterostructures by solid source reaction." nano letters 8(12): 4528-4533 keywords: iii-v materials, thin films, solid state reaction, epitaxy, contact https://sites.google.com/site/tramp2019marrakech/ mailto:carine.perrin-pellegrino@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p47 or017 in situ and real time study of gravity effects on the solidification microstructure formation h. soltani1,3*, g. reinhart1, m.c. benoudia2, f. ngomesse1, m. zahzouh3 and h. nguyen-thi1 1 aix marseille univ, université de toulon, cnrs, im2np, marseille, france 2 l3m-ecole nationale supérieure des mines et de la métallurgie, annaba, algeria 3 lmgm-badji mokhtar university, p.o. box 12, 23000, annaba, algeria hadjer.soltani@im2np.fr; guillaume.reinhart@im2np.fr; mohamed-cherif.benoudia@ensmmannaba.dz; fabiola.ngomesse@im2np.fr; moussa.zahzouh@ensmm-annaba.dz; e-mail*/ henri.nguyen-thi@im2np.fr abstract mechanical properties of materials are deeply related to the solidification microstructure, which results from the solidification conditions such as the thermal history and gravity-related phenomena. the understanding of the relationship between the final grain structure and the processing conditions is thus crucial to improve industrial products. in this work, we will present a study of the gravity effects on the dynamic of the microstructure formation. it is well known that gravity-related phenomena such as thermo-solutal convection caused by density gradients in the melt, and buoyancy when the liquid phase is denser than the solid phase or vice-versa, are unavoidable and can affect drastically both the grain number and their morphology. the aim of our study is to investigate directional solidification experiments of refined al-20wt.%cu alloys, using in-situ and real time x-radiography. experiments were carried out on sheet-like samples (thickness ≈ 250 μm) in the laboratory device sfinx (solidification furnace with in situ x-radiography), for two different furnace orientations with respect to the gravity direction: horizontal orientation where the main surface of the sample is perpendicular to the gravity direction. for this configuration the gravity related phenomena are limited in the thickness of the sample. vertical orientation where the main surface is parallel to the gravity direction. for this position, the temperature gradient can be either parallel to gravity (upward solidification) or antiparallel to gravity (downward solidification). the gravity effects are significant in the liquid phase of the sample for this configuration. the comparison of the grain formation mechanisms during the experiments performed with the same solidification parameters (growth velocity and temperature gradient), but with the two different configurations (horizontal and vertical) allows us to reveal the different effects related to the presence of gravity and that affect the grain structure. the main phenomena highlighted from this comparison and that affect drastically the grains structure formation are the grain floatation during the upward solidification due to the buoyancy force, and the cu-enriched plume formation during the downward solidification. keywords: solidification, x-radiography, convection, grain structure, gravity, buoyancy. https://sites.google.com/site/tramp2019marrakech/ mailto:henri.nguyen-thi@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p48 or018 effect of sr doping on the conduction process in the copper calcium titanate ceramics synthesized by semi wet method s. amhil1*, l. essaleh1, e. choukri1, a, alimoussa1 1university cadi ayyad marrakech /laboratory of condensed matter and nanostructures e mail*/ amhilsamira@gmail.com abstract in this report, strontium (sr) doped calcium copper titanate ca1-xsrxcu3ti4o12 with two values x=0 and x=0.05 commonly known as cscto ceramics have been obtained by using the semi wet route synthesis method. rietveld refinement shows that the powders crystallize in the cubic perovskite related structure with im3 space group. scanning electron micrograph (sem) analysis shows that the average grain size of ceramics becomes larger when sr doping is considered. both dc and ac electrical conductivity are investigated throughly in the temperature and frequency ranges between [373-653k] and [20hz-1mhz], respectively. the values of the average activation energies for cscto-0 (x=0) and cscto-5 (x=0.05) were found to be 612mev and 576mev, respectively. in fact, sr doping has an effect on the broadening of the impurity band that can lead to a dramatic decrease in the activation conduction energy of cscto ceramics. a systematic study of ac electrical conductivity reveals that the predominant conduction mechanism existing in these ceramics is generated by large polaron hopping process. this mechanism has also been identified by the modulus analysis and confirmed by comparing the hopping polaron size with the lattice parameter. keywords: copper calcium titanate, semi wet route, low temperature, electrical properties, olpt. https://sites.google.com/site/tramp2019marrakech/ mailto:amhilsamira@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p49 or019 layered na0.66[co1-ytiy]o2 cathodes for next generation sodium-ion batteries noha sabi1,2*, angelina sarapulova3, sylvio indris3, sonia dsoke4, helmut ehrenberg3 and ismael saadoune1,2 1lcme, fst marrakesh, university cadi ayyad, av. a. khattabi, bp 549, 40000, marrakech, morocco 2materials science and nano-engineering department, mohammed vi polytechnic university, ben guerir, morocco 3 institute for applied materials (iam), karlsruhe institute of technology (kit), hermann-von-helmholtz platz 1, 76344 eggenstein-leopoldshafen, karlsruhe, germany 4helmholtz-institute ulm for electrochemical energy storage (hiu), p.o. box 3640, d-76021 karlsruhe, germany e-mail*/ sabinoha1992@gmail.com abstract rechargeable sodium-ion batteries are regarded to be promising for next generation storage devices i.e. grids thanks to the rich and natural abundance of sodium and as a consequence low price. in addition to that, sodium-ion batteries exhibit similar electrochemical mechanism as commercial lithium-ion batteries. commercialized by sony in 1991[1], licoo2 has received tremendous success as positive electrode material for lithium ion batteries. this was the main reason that motivated researchers to investigate first naxcoo2 as alternative for the sodium-ion technology. in comparison to its lithium counterpart, the naxcoo2 structure show numerous potential steps during electrochemical sodium intercalation/deintercalation. this suggests more complicated phase transitions. the aim of this work is to elucidate the effect of increasing titanium contents on the structural properties and electrochemical performances of naxcoyti1-yo2 (y=0, 0.05;0.1; 0.2; 0.3; 0.33) system in na half-cell. naxcoyti1-yo2 compositions were synthesized through the solid state method, the sodium electrochemical intercalation/deintercalation in the potential window 2-4.2v was investigated via diffraction using synchrotron radiations. the crystal structure of all compositions was stable over the cathodic potential window. inactive titanium has drastically reduced the number of potential steps and limited the biphasic domains observed in the case of na0.66coo2. the combined effect of cobalt and titanium has shed light on a powerful candidates in terms of structural stability at high voltages and stable capacity for next generation sodium ion batteries. figure 1: galvanostatic cycling test with potential limitations involving naxco1-ytiyo2 with different titanium concentrations at sodium half-cell in the potential range 2 and 4.2v keywords: sodium-ion batteries, layered structures, na0.66co1-ytiyo2, references [1] barboux, p., tarascon, j-m., shokoohi. f-k. the use of acetates as precursors for the low-temperature synthesis of limn2o4 and licoo2 intercalation compounds. j. solid state chem.94, 185-196 (1991). [2] berthelot, r., carlierand, d., delmas, c. electrochemical investigation of the p2–naxcoo2 phase diagram, nature materials 10,74–80 (2011). acknowledgements ms sabi is grateful to ocp and um6p for the financial support. https://sites.google.com/site/tramp2019marrakech/ mailto:sabinoha1992@gmail.com https://www.sciencedirect.com/science/article/pii/0022459691902316#! https://www.sciencedirect.com/science/article/pii/0022459691902316#! https://www.sciencedirect.com/science/article/pii/0022459691902316#! third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p50 or020 structural, thermal, electrical and electrocaloric properties of lead-free bczt-bct solid solution s. merselmiz1*, s. ben moumen1, z. hanani1,2, d. mezzane1, s. fourcade2, y. gagou3, k. hoummada4, l. hajji1, z. abkhar1,n. novac5, b. rožič 5, z. kutnjak5 1 lmcn, cadi ayyad university, marrakesh, 40000, morocco 2 icmcb, university of bordeaux, pessac, 33600, france 3 lpmc, university of picardy jules verne, amiens, 80039, france 4 im2np, aix marseille university, marseille, 13397, france 5 jožef stefan institute, ljubljana, 1000, slovenia e-mail*/ soukaina.mers@gmail.com abstract lead-free batio3 (bto) and its solid solutions (bst, bct, bzt, bct-bzt) have a wide range of applications in many fields including electronic industries, such as positive temperature coefficient devices, infrared detectors, multilayer ceramic capacitors (mlcc), lead-free piezoelectric transducers, microwave tunable dielectrics , because of their enhanced dielectric, ferroelectric, piezoelectric and electrocaloric properties 1–2. ba1-xcaxtio3 (bct) solid solution has been reported as a promising mlcc, dielectric filters and piezoelectric actuators3. in recent years, an increase interest in the development of lead-free piezoelectric and electrocaloric materials such as (1-x)ba(zr0.2ti0.8)o3–x(ba0.7ca0.3)tio3 (bzt-bct) system by dint of its excellent electromechanical properties4. in this study, (ba0.8ca0.2)(zr0.02ti0.98)o3 (ba0.8ca0.2)tio3 solid solution in weight ratio 1:1 abbreviated bczt-bct was synthesized by solid state reaction method. structural, dielectric, thermal, ferroelectric, alongside to electrocaloric properties were thoroughly investigated. in-situ raman spectroscopy results confirmed the existence of tetragonal phase at room temperature. x-ray diffraction and the differential thermal analysis (dsc) measurements of bczt-bct ceramic were used to highlight the phase transition from tetragonal to cubic at 115 °c. high dielectric permittivity (ε’~ 9000), low dielectric loss (δ ~0.02) were found at curie temperature tc=115 °c. the coercive field of bczt-bct was found to be less than 2 kv/cm. keywords: lead-free ceramic, solid solution, phase transition, dielectric, ferroelectric references 1 c. mao, s. yan, s. cao, c. yao, f. cao, g. wang, x. dong, x. hu, and c. yang, j. eur. ceram. soc. 34, 2933 (2014). 2 z. hanani, d. mezzane, m. amjoud, a.g. razumnaya, s. fourcade, y. gagou, k. hoummada, m. el marssi, and m. gouné, j. mater. sci. mater. electron. 30, 6430 (2019). 3 b. asbani, j.-l. dellis, a. lahmar, m. courty, m. amjoud, y. gagou, k. djellab, d. mezzane, z. kutnjak, and m. el marssi, appl. phys. lett. 106, 042902 (2015). 4 m. acosta, n. novak, v. rojas, s. patel, r. vaish, j. koruza, g.a. rossetti, and j. rödel, appl. phys. rev. 4, 41305 (2017). https://sites.google.com/site/tramp2019marrakech/ mailto:soukaina.mers@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p51 or021 microstructural evolution of dissimilar metal welds during ageing: an apt/ebsd investigation i.medouni1, 2*, a.portavoce1, p.maugis1, m.yescas2, f.roch2, p.joly2, k.hoummada1 1 aix marseille univ, cnrs, université de toulon, im2np, 13397, marseille, france 2 framatome, développement (dtid) et ingénierie mécanique (dtim), 92084 paris la défense cedex e-mail*/ ilyes.medouni@im2np.fr abstract the integrity of the welded joints made to assemble the various components of a nuclear reactor is very important for the proper functioning of the power plant. the joints are used to assemble at least two different materials, and the welding operation of these heterogeneous materials involves metallurgical and chemical phenomena, leading to atomic redistributions. furthermore, atomic redistribution in the joint vicinity can be modified (grain boundary segregation, precipitation…) during ageing at the service temperature, modifying the mechanical properties of the polycrystalline materials. a new narrow gap design of dissimilar metal welds (dmw) for nuclear plants has been developed recently using inconel52 as filler metal, in order to join the main components of the nuclear island made of bainitic low alloy steel (las), with the main coolant line pipes made of austenitic stainless steel 304l type. in this work, the [inconel52/las] side of the dmw is studied, since the rupture of fracture toughness specimens in the brittle to ductile domain takes place in this area. due to the temperature gradient cause by the welding procedure, four different zones are generated in the joint vicinity, exhibiting different structural and chemical properties: i) a carbide band at the [inconel52/las] interface, a heat affected zone deeper in the las composed of two zones ii) a carbon depleted zone and iii) a carbon non-depleted zone, and finally iv) the base las metal. the aim of this work is to study the metallurgical changes in these four zones due to thermal ageing. x-ray diffraction, ebsd, sem, and atom probe tomography are used to investigate both structural (dislocation density…) and chemical (grain boundary segregation, precipitation…) evolutions, in the case of five different ageing states, obtained by five different annealing conditions. this work is a first attempt to establish a link with the mechanical behavior of dmws. keywords: dmws, ageing, apt, segregation, mechanical behavior https://sites.google.com/site/tramp2019marrakech/ mailto:ilyes.medouni@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p52 or022 enhanced of magnetoelectric coupling in mfe2o4/pzt/ mfe2o4 (m=ni,co) : a monte carlo simulation m. ait tamerd1*, b. abraime1,2 , a. lahmar4, m. el marssi4, m. hamedoun2, a. benyoussef2,3, a. el kenz1 1lamcsci (ppr15), faculty of science, mohammed v university, rabat, morocco 2 institute of nanomaterials and nanotechnology, mascir, rabat, morocco 3 hassan ii academy of science and technology, rabat, morocco. 4laboratoire de physique de la matière condensée (lpmc), université de picardie, amiens, france email*/ aittamerd@gmail.com abstract based on the monte carlo simulation, ferroelectric, magnetic and magnetoelectric properties of nife2o4/pzt (nfo/pzt), cofe2o4/pzt (cfo/pzt), nife2o4/pzt/cofe2o4 (nfo/pzt/cfo) and nife2o4/pzt/nife2o4 (nfo/pzt/nfo) heterostructures were carried out. the effect of the temperature on magnetization, electric polarization and their susceptibilities have been examined. the determination of the interfacial magnetoelectric coupling interaction jme in nfo/pzt interface and cfo/pzt interface permitted to predicte the magnetoelectric voltage coefficient innfo/pzt/cfo and nfo/pzt/nfo heterostructures. interestingly, a high magnetoelectric voltage coefficient of 762.7 and 2080 mv/(cm.oe) was predicted in nfo/pzt/cfo and nfo/pzt/nfo, respectively. moreover, the effect of jme on m-h and p-h hysteresis loops and magnetoelectric voltage coefficient was studied. keywords : monte carlo simulation ;magnetoelectric properties ; heterostructures; m-h and p-h hysteresis loops ; magnetoelectric voltage coefficient. https://sites.google.com/site/tramp2019marrakech/ mailto:aittamerd@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p53 or023 synthesis and characterization of bi2o3 by self assembly phenomenon for rhodamine b photodegradation m a. baabou 1,*, m a. frémy 1, s. villain 1, c. favotto 1 1institut matériaux microélectronique et nanosciences de provence, umr cnrs 7334, université de toulon cs 60864 f-83041 toulon cedex 9, france. email*/ mohamed-anass.baabou@im2np.fr abstract in recent years, semiconductor photo-catalysts attracted many researchers due to their promising applications in the removal of environmental pollutants, such as the photo-degradation of organic dyes. furthermore, self-assembled 3d architectures of these materials can increase their catalytic performances. for this purpose, we investigate the relationship between the architecture via the selfassembly phenomenon of bismuth oxide (bi2o3), a semiconductor which exhibit an interesting bandgap, and its photo-catalytic activity for the degradation of one of the most important organic dye. in our study, we report the fabrication of various morphological bismuth oxides (bi2o3) by a self-assembly process of bismuth oxalate at room temperature. under controlled ph, bismuth oxide was successfully synthetized from oxalate precursor, by an aqueous precipitation method using bismuth (iii) nitrate hydrate, nitric acid and oxalic acid. the elaborated sample was dried and calcined for two hours. the powders were structurally, morphologically and thermally characterized using x-ray diffraction (xrd), scanning electron microscopy (sem) coupled with energy dispersive x-ray analysis (eds), thermogravimetric analysis coupled with differential thermal analysis (tga/tda). the photodegradation performance of the as prepared photo-catalyst was evaluated on the degradation of rhodamine b using uv visible spectrometer. keywords: bismuth oxide bi2o3, self-assembly phenomenon, photo-degradation, rhodamine b https://sites.google.com/site/tramp2019marrakech/ mailto:mohamed-anass.baabou@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p54 or024 structural, electronic, magnetic, and magnetocaloric properties in semiconductors tri-chalcogenides (tmtc) with the chemical formula abx3 w. bazine 1,*, n. tahiri 1, o. el bounagui 2, h. ez-zahraouy 1 1 laboratory of condensed matter and interdisciplinary sciences department of physics, faculty of sciences, mohammed v university p. o. box 1014, rabat, morocco 2ephe, modeling & simulations, faculty of science, mohammed v university, rabat, morocco e mail*/ w.bazine@gmail.com abstract as one of the rare ferromagnetic semiconductors tri-chalcogenides (tmtc) with the chemical formula abx3 (a = mn, cr; b = si, ge; x = s, se, te) has recently attracted a great deal of attention as a potential candidate for next-generation high-performance nanospintronic devices. in this study, the density of states, band structure and optical properties have been studied by ab-initio calculation. respectively, the magnetic and magnetocaloric properties have been performed using monte carlo simulation by adopting various models, including the three-dimensional (3d) ising model and the 3d heisenberg model. the curie temperatures were reported to increase as the number of layers is reduced. [1-2] keywords : magnetocaloric, heisenberg, tri-chalcogenides, optical properties, nanospintronic. https://sites.google.com/site/tramp2019marrakech/ mailto:w.bazine@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p55 or025 structural, dielectric and electrocaloric properties of (ba0.85ca0.15)(ti0.9zr0.1-xsnx)o3 ceramics elaborated by sol-gel method s. belkhadira*, a. neqalia, m. amjouda, d. mezzanea, a.alimoussaa, e.choukria ,i.raevskib, , y.gagouc,* , m. el marssic, igor a. luk'yanchukc, z. kutnjakd, b. rožičd a laboratoire de la matière condensée et nanostructures lmcn, f.s.t.g. université cadi ayyad, bp 549, marrakech, morocco b research institute of physics and faculty of physics, southern federal university, 194 stachki ave., 344090, rostov-on-don, russia c laboratoire de physique de la matière condensée lpmc, université de picardie jules verne, 33 rue saint-leu, 80039, amiens cedex, france d laboratory for calorimetry and dielectric spectroscopy, condensed matter physics department, jozef stefan institute, ljubljana, slovenia. e-mail*/ saad_nlp@hotmail.fr abstract ferroelectric ceramics (ba0.85ca0.15)(ti0.9zr0.1-xsnx)o3 (x=0.00, 0.02, 0.04, 0.06) were prepared by a sol-gel method. structural investigation revealed the co-existence of tetragonal (p4mm) and orthorhombic (pmm2) symmetries at room temperature for the undoped ceramic, while only a tetragonal structure (p4mm) was observed for the doped ceramics. dielectric measurements indicate a dielectric relaxation process at high temperatures which is essentially related to the hopping of oxygen vacancies v..𝑂. furthermore, a down shifting of the curie temperature (tc) with increasing sn4+ doping rate has been revealed. the temperature profiles of the raman spectra unveiled the existence of polar nanoregions (pnrs) above the curie temperature in all ceramics. the ferroelectric properties were found to be related to the microstructure. electrocaloric effect was investigated in this system that revealed an electrocaloric responsivity of 0.225×10-6 k m/v for the composition with x = 0.04 sn doping, where other remarkable physical properties were also observed. keywords: sol-gel, polar nanoregions, phase transition, electro-caloric. https://sites.google.com/site/tramp2019marrakech/ https://www.researchgate.net/profile/igor_raevski_raevskii_rayevsky_raevsky_rayevskiy https://scholar.google.ru/citations?view_op=view_org&hl=en&org=14375333802498491015 mailto:saad_nlp@hotmail.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p56 or026 arsenene monolayer as an outstanding anode material for (li/na/mg)-ion batteries: density functional theory hind benzidi1*, marwan lakhal1, mourad garara1, mustapha abdellaoui1, abdelilah benyoussef2, abdallah el kenz1, and omar mounkachi1 1laboratoire de matière condensée et sciences interdisciplinaires (lamcsci), b.p. 1014, faculty of science, mohammed v university, rabat, morocco 2materials and nanomaterials centre, moroccan foundation for advanced science, innovation and research, mascir, rabat, morocco e-mail*/ hind.benzidi@gmail.com abstract arsenene, a single layer arsenic nanosheet with a honeycomb structure, has attracted increasing attention recently due to its many exceptional properties. in this paper, the density functional theory (dft) calculations are employed to investigate and compare the interaction of li, na or mg ions with the arsenene monolayer. on purpose, to be used as anodes in lithium, sodium, and magnesium ion rechargeable batteries. the results indicate that the li, na and mg adatom preferably adsorbed on the valley sites, with a negative adsorption energy of -2,55; -1,91 and -1,10 ev, respectively, introducing strong binding between alkali-metal and arsenene monolayer which is important fact for battery application. also, it is found the arsenene exhibit a high theoretical specific capacity up to 1430,91 mah/g for li and mg and 1073,18 mah/g for na, which are extremely higher than the commercially used graphite anode (372 mah/g) in li-ion batteries. furthermore, the diffusion barrier energies of li, na and mg ions are calculated using the nudged elastic band method. the activation energy barriers of these ions show isotropic behavior for the different pathway (x, y, and diagonal directions) where the obtained values are 0,16; 0,05 and 0,016 ev, for li, na, and mg ion, respectively. our findings indicate that the high capacity, low open circuit voltage, and ultrahigh barrier diffusion make the arsenene a good candidate for application as an anode material for rechargeable batteries. keywords: first principal calculations, 2d materials, li-batteries, nabatteries, mg-ion batteries https://sites.google.com/site/tramp2019marrakech/ mailto:hind.benzidi@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p57 or027 structural, dielectric and magnetic properties of multiferroic (1-x) la0.5ca0.5mno3 (x) bati0.8sn0.2o3 laminated composites s. ben moumen1*, y. gagou2, s. belkhadir1, d. mezzane1, m. amjoud1, b. rožič3, l. hajji1, z. kutnjak3, z. jaglicic4, m. jagodic4, m. el marssi2, y. kopelevich5 and igor a. luk’yanchuk2. 1lmcn, f.s.t.g. université cadi ayyad, bp 549, marrakech, morocco 2lpmc, université de picardie jules verne, 33 rue saint-leu, 80039 amiens cédex, france 3jozef stefan institute, jamova cesta 39, 1000 ljubljana, slovenia 4institute of mathematics, physics and mechanics, jadranska 19, 1000 ljubljana, sloven 5instituto de fisica gleb wataghin, universidade estadual de campinas, unicamp 13083-970, campinas, sao paulo, brazil email*/ said.benmoumen@yahoo.fr abstract high performance lead-free multiferroic composites are desired to replace the lead-based ceramics in multifunctional devices applications. laminated compounds were prepared from ferroelectric and ferromagnetic materials are step toward this aim. in this work, we present laminated ceramics compound by considering the ferromagnetic la0.5ca0.5mno3 (lcmo) and the ferroelectric bati0.8sn0.2o3 (btso) in two different proportions. compounds (1-x)lcmo(x)btso with x=1 and 0 (pure materials) were synthesized by the sol gel method and x=0.7 and 0.5 (laminated) compounds were elaborated by welding appropriate mass ratios of each pure material by using the silver paste technique. structural, dielectric, ferroelectric, microstructure and magnetic characterizsation were conducted on these samples. x-ray scattering results showed pure perovskite phases confirming the successful formation of both lcmo and btso. sem images evidenced the laminated structure and good quality of the interfaces. the laminated composite materials have demonstrated a multiferroic behaviour characterized by the ferroelectric and the ferromagnetic hysteresis loops. the enhancement of the dielectric constant in the laminated composite samples is mainly attributed to the maxwell-wagner polarization. keywords: ferroelectric, ferromagnetic, laminated composites, multiferroics. https://sites.google.com/site/tramp2019marrakech/ mailto:said.benmoumen@yahoo.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p58 or028 effect of mineralizer on microstructure and electrical properties of forsterite s. el asria,b*, h. ahamdanea, l. hajjib , m. a. el idrissi raghnia, m. el hadria and m. mansoric alaboratory of materials science, faculty of sciences-marrakech. blaboratory of condensed matter and nanostructure, faculty of sciences and thecnologymarrakech. claboratory of chemistry of materials and environment, faculty of sciences and thecnologymarrakech. e-mail*/ saloua.el.asrii@gmail.com abstract olivine materials were recently subjected to extensive studies, due to their high performance as cathode for mg rechargeable battery. previous works were focused on the study the effect of microstructure and element doping on electrical properties and electrochemistry performance of mg2sio4. in this work, the effect of cation alkaline salts mcl (m=na+, k+) used as mineralizer on structural, microstructural and electrical properties of mg2sio4 was investigated. pure forsterite single phase mg2sio4 was synthesized by sol-gel method and the final powder was characterized by x-ray diffraction and confirms the synthesis of pure materials. tga shows that the synthesized samples with nacl have a lower temperature of the initial formation of forsterite than those prepared with kcl. sem was carried out to evaluate the morphology of sintered ceramics and their bulk densities were measured by archimedes method and electrical measurements were carried by electrical impedance spectroscopy. keywords: forsterite; mg-battery; sol-gel route; electrical impedance spectroscopy https://sites.google.com/site/tramp2019marrakech/ mailto:saloua.el.asrii@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p59 or029 co-substitution effect on tuning the physical properties in the new perovskite series ba1-xlaxti1-xfexo3 (0 ≤ x ≤ 1): structural, magnetic and optical investigations toward high performance materials fatima el bachraoui1, 2, z. chchiyai2, y. tamraoui1, s. louihi2, h.el moussaoui3, j. alami1 and b.manoun1,2,* 1materials science and nano-engineering department, university mohammed vi polytechnic, benguerir, morocco. 2univ hassan 1er, laboratoire rayonnement-matière et instrumentation, faculty of sciences and technology settat,university hassan 1st morocco. 3institute of nanomaterials and nanotechnologies, materials and nanomaterials center mascir foundatio, rabat, morocco e-mail* / fatima.elbachraoui@um6p.ma abstract the search of new cheap, efficient and stable materials in different fields such as energy storage, solid oxides fuel cells, catalysis or electrocatalysis [1] has brought perovskites materials to be the foremost studied materials. perovskite materials crystallize in different structures under the general formula (abo3), where a is a rare or alkaline earth element and b is a transition metal cation. their extremely thermodynamically stable atomic arrangement and their structural flexibility and ability to accommodate a wide range of the periodic table elements make it possible for researcher to enhance, tune or induce their macroscopic properties [2]. the present work report the physical properties dependence to the structural and composition variation of a novel perovskite series abo3type material. a solid solution of perovskite series ba1-xlaxti1-xfexo3 with 0 ≤ x ≤ 1 has been prepared using the conventional solid state reaction technique. the structural investigation using the rietveld refinement method allowed the identification of two phase transitions. the optical response of the studied perovskites showed large board absorption in the uv-vis domain with a shift toward the visible domain as the amount of la3+ and fe3+ ions increases. magnetic measurements were carried out and strong response of ferromagnetic behavior where the temperature dependent magnetization at 500 oe under field-cooled (fc) and zero field cooled (zfc) modes shows characteristic of magnetic frustration or spin glass-like behavior. keywords: perovskites, phase transition, band gap, ferromagnetic, visible light absorption. references 1. jun a, kim j, shin j, kim g (2016). chemelectrochem 3:511–530. 2. manoun b, ezzahi a, benmokhtar s, et al (2013). j mol struct 1045:1–14. https://sites.google.com/site/tramp2019marrakech/ mailto:fatima.elbachraoui@um6p.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p60 or030 role of fe3+ and cr3+ cations substitution on the magnetic and magnetocaloric properties of (la0.6pr0.1)sr0.3mno3 l. fkhar(1, 2)*, m. ait ali(1), o. mounkachi(2,3), m. hamedoun(2), a. el kenz(3), a. benyoussef(2,3) , e.-k. hlil(5) and k. el maalam( 2, 3,*) 1 coordination chemistry laboratory, cadi ayyad university, faculty of sciences semlalia (uca-fssm), b.p. 2390 40000 marrakech, morocco. 2 materials and nanomaterials center, mascir foundation, b.p. 10100-rabat, morocco. 3 laboratory of condensed matter and interdisciplinary sciences (lamcsci) , b.p. 1014, faculty of science, mohammed v university, rabat, morocco. 4 institut néel, cnrs-ujf, b.p. 166, 38042 grenoble cedex, france e-mail*/ fkhar.lahcen@gmail.com & khadija.elmaalam@gmail.com abstract in this work, we report the effect of (fe/cr) doping on structural, magnetic and magnetocaloric properties of (la0.6pr0.1)sr0.3mn0.95(fe/cr)0.05o3 polycrystalline manganite compounds. the samples were prepared using a standard solid state reaction, x-ray powder diffraction (xrd) shows that all the samples crystallize in a rhombohedral phase with r-3c space group. the morphological study showed that the grains are irregularly sphericallyshaped and have a micrometric size, while the chemical composition spectra confirm the presence of all the predicted elements. magnetic measurements indicate that the ferromagnetic double exchange interaction is weakened with mn-site doping, resulting in a shift in tc from 360 k (for undoped mn-site) to 320 k (for fe doped mn-site) and to 350 k (for cr doped mn-site). the samples present a high saturation magnetization which exceeds 78 emu/g and a very low coercive field ranging from 60 oe to 170 oe at 5 k. the magnetic entropy change (δsm) and the relative cooling power (rcp) values have been estimated from the magnetization measurements at temperature beside the curie temperature. the maximum of magnetic entropy change, under an applied magnetic field of 5 t, reaches a value of 2.73 j/(kg.k) in the case of la0.6pr0.1sr0.3mno3 compound. this value decreases in the case of the (fe/cr) doped products. the rcp values have been found in the range of 300-320 j/kg. these results confirm the effect of mn-site doping on the studied properties, which were explained by the weakening of the double exchange interaction. keywords: magnetocaloric properties, manganite, double exchange interaction, magnetic entropy change, relative cooling power. https://sites.google.com/site/tramp2019marrakech/ mailto:fkhar.lahcen@gmail.com mailto:khadija.elmaalam@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p61 or031 photocatalytic activity of tio2/zirconium phosphate nanocomposites for the removal of orange g from aqueous solutions i.boualia* , b.rhoutaa a laboratoire de matière condensée et nanostructures (lmcn), faculté des sciences et techniques guéliz, université cadi ayyad, bp 549, marrakech, morrocco email*/ bouali.imane@gmail.com abstact zirconium phosphates (zrp) organomodified by cetyltrimethylammonium bromide (ctab) were functionalized by the titanium precursor. the tio2 photocatalyst attached to zirconium phosphates were then characterized using various techniques such as x-ray diffraction (xrd), infrared spectroscopy (ir).the calcination at different temperatures of the raw precursor samples thus obtained has allowed the development of inorgano-inorganic tio2zrp nanocomposite materials in which tio2 crystallizes under the most photoactive variety: anatase and which remains remarkably stable until at 900 °c as shown by temperatureprogrammed xrd. further, the photocatalytic activity of the resulting nanocomposites samples were evaluated for the removal of orange g (og) from aqueous solution as a model dye pollutant. the photocatalytic activity performances were found to be better for tio2zrp nanocomposite treated at 900 °c, compared to the supported photocatalyst treated at 500 and 600 °c. keywords: zirconium phosphates, cetyltrimethylammonium bromide, organomidification, photocatalyst. https://sites.google.com/site/tramp2019marrakech/ mailto:bouali.imane@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p62 or032 negative capacitance investigations in pb(zr0.2ti0.8)o3 /srtio3 superlattices m. gharbi1*, a. sené1, j. l. dellis1, a. sylvestre2, f. le marrec1, m.g. karkut1, c. davoisne3, l. dupont3, i. luk’yanchuk1, and n. lemée1 1 lpmc, ea 2081, university of picardie jules verne, 80039 amiens, france 2 university of grenoble alpes, cnrs, grenoble inp, g2elab, f-38000 grenoble, france 3 lrcs, umr cnrs 7314, university of picardie jules verne, 80039 amiens, france e-mail*/ mariem.gharbi@etud.u-picardie.fr / gharbi.mariem92@gmail.com abstract the negative capacitance phenomenon, evidenced in ferroelectric/paraelectric heterostructures, has aroused a great interest since it could provide a way to reduce the power consumption of field-effect transistors (1). this negative capacitance effect was shown to be strongly related to 180° stripe domain structure, produced to minimize the electrostatic energy, arising from the depolarization field. ferroelectric/paraelectric superlattices geometry provides a means to investigate the negative capacitance phenomenon as shown by zubko et al (2). by alternating individual ferroelectric layers with dielectric layers, it is possible (1) to produce ferroelectric domains, which are isolated from surface or film-substrate interfaces, and (2) to modify the electrostatic boundaries and mechanical strains, which strongly influence the negative capacitance effect. here we present experimental results on a series of pb(zr0.2ti0.8)o3 /srtio3 superlattices in which we evidence 180° stripe polar nanodomains. the structural characteristics of these superlattices and the influence of the multidomain state on the ferroelectric phase transitions, as well as the temperature dependent dielectric susceptibility will be presented. the electrostatic effect in the superlattice is confirmed by a noticeable reduction of the curie temperature. the temperature dependent dielectric susceptibility measurements, between 300k and 680k, give the indication that a negative capacitance was stabilized within the ferroelectric layers. we will show that these experimental results validate the ginzburg-landau model that predicted a stable negative regime in the ferroelectric layers within the pb(zr0.2ti0.8)o3 /srtio3 superlattices. references [1] s. salahuddin and s. datta, nano lett.8, 405 (2008) [2] p. zubko et al., nature, 534, 524–528, (2016) keywords: ferroelectric, superlattice, negative capacitance, dielectric measurements, xrd. https://sites.google.com/site/tramp2019marrakech/ mailto:mariem.gharbi@etud.u-picardie.fr mailto:gharbi.mariem92@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p63 or033 monte carlo simulation of the magnetic properties of bulk cofe2o4 vs cofe2o4 nanoparticles r. lamouri1,2*, o. mounkachi1, e. salmani1, m. hamedoun2, a. benyoussef1,2,3, h. ezzahraouy1 1 lamcsci/ faculty of science/mohammed v university, rabat, morocco 2 mnm center/ mascir foundation/ rabat design center, rabat, morocco 3 hassan ii academy of science and technology, rabat, morocco e mail/ rachida.lamouri@gmail.com abstract nano-structured materials, counter to bulk the ones, have proven their various applicabilities with the increased demand for size reduction materials. cobalt ferrite is considered as one of the most important material in the spinel family because of its interesting properties such as good chemical stability, low synthesis cost, high coercivity and significant saturation magnetization. these properties influence the magnetic properties of the material, in particular, the maximum energy product (bh) max, which is the main characteristic of a permanent magnet. in this study, we report the magnetic properties of bulk cofe2o4 ferrite and the size effect on the magnetic properties of single nanoparticles of cofe2o4 using monte carlo simulation with the ising model. periodic and free boundaries conditions were used to simulate bulk and nanoparticles, respectively. saturation magnetization increases with the increase of the particle size towards bulk value. small squareness ration (mr/ms) is observed for bulk particles, while a large values was shown in single nanoparticles. the performance of the cubic shaped cofe2o4 ferrite was evaluated in term of the maximum energy product. it is found that bulk cobalt spinel ferrite exhibits a maximum energy product of 0.19 mg.oe at room temperature. however, a large value of 2.83 mg.oe was found for cubic shaped nanoparticles of 21nm. the obtained results pave the way for the development of cofe2o4 spinel ferrites for permanent magnet applications. keywords: cofe2o4 ferrite, monte carlo, energy product, permanent magnet. https://sites.google.com/site/tramp2019marrakech/ mailto:rachida.lamouri@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p64 or034 novel biohybrid aerogels based on cellulosic and cobalt metallic nanoparticles: efficient catalysts for green reduction reactions nouaamane el idrissi1*, hamid kaddami, larbi belachemi 1laboratory of organometallic and macromolecular chemistry-composite materials, department of chemical sciences, faculty of science and technology, cadi ayyad university marrakech, morocco. e-mail*/ nouaamane.elidrissi@edu.uca.ac.ma abstract heterogeneous catalysis has played an important role in chemical reactions and environmental remediation, there is a growing need for environmentally benign, economic and highly active catalysts. metal and metal oxide nanoparticles (nps) have attracted a lot of attention due to their excellent catalytic activities in different organic transformation reactions. but, their applications is limited because of their self-agglomeration in solution which reduces their catalytic performance. in this study, a cellulose nanomaterial (cellulose nanofiber, cnf) was employed as solid support and stabilizer agent for the highly active cobalt nanoparticles via in situ green and facile synthesis as an environmentally benign material. the structure of synthesized organic-inorganic hybrids co/cnf is characterized by field emission scanning electron microscopy, energy dispersive spectroscopy, fourier transform infrared spectroscopy and x-ray diffraction. the hybrid aerogel nanocomposites co/cell-cnf demonstrated excellent catalytic activity for the reduction of 4-nitroaniline (4-na) to 4aminoaniline (4-aa) in water with nabh4. even with a very low amount of catalyst was also found to be good enough to achieve 100% reduction of 4-na with a higher reaction rate (8 min). the heterogeneous nanocomposite catalyst was easily isolated from the reaction mixture by simple filtration and reused 5 times without significant loss of its catalytic activity. keywords: cobalt nanoparticles; composite; green chemistry; nanocellulose; recyclability. https://sites.google.com/site/tramp2019marrakech/ mailto:nouaamane.elidrissi@edu.uca.ac.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p65 or035 effects of (cao, nio and zno) additives on the crystallization behavior and mechanical properties of cordierite synthetized from a moroccan clay h. hajjou 1, l. saâdi 1, and m. waqif 1 1nanostructures and condensed materials laboratory (lmcn), faculty of science and technology, marrakech, morocco email*/ hajjou.hanaa@gmail.com , la.saadi@yahoo.fr , m.waqif@yahoo.fr abstract the cordierite (2mgo, 2al2o3, 5sio2) is a magnesium aluminosilicate that presents a very significant technological interest, and constitutes a promising candidate in many applications thanks to its physicochemical properties. cordierite precursors were prepared by solid-state reaction from a moroccan clay named “ghassoul”. this later contain a large amount of silica sio2 and has the ability to consolidate by heat treatment at 1000 ° c, hence its use as a raw material for the synthesis of cordierite. the purpose of this study is to investigate the effects of additives on the crystallization behavior of cordierite. in this regard, three additives were used (zno, nio and cao) with a percentage of 5%. the mineralogical analysis show that the use of additives affect the nature of the secondary phases present. the use of zinc oxide and nickel oxide leads to the formation of an appreciable amount of spinel and protoenstatite. unfortunately, the presence of nickel oxide and zinc oxide could not improve the crystallization temperature of cordierite; while, the presence of the calcium oxide blocks completely the formation of cordierite. the addition of the additives has a strong influence on the mechanical behavior of the sample; it leads to the deterioration of the mechanical properties following the increase of the porosity. nevertheless, the sample without adding additive remains to have the best mechanical properties. keywords: cordierite, ghassoul, additives, mechanical properties. https://sites.google.com/site/tramp2019marrakech/ mailto:hajjou.hanaa@gmail.com mailto:la.saadi@yahoo.fr mailto:m.waqif@yahoo.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p66 or036 effect of bao-bi2o3-p2o5 glass additive on structural and dielectric properties of batio3 ceramics e. haily a, l. bih a, b, b. manoun c, d, a. azrour e. a equipe physico-chimie la matière condensée (pcmc), faculté des sciences de meknès, maroc. b département matériaux et procédés, ensam meknès, université moulay ismail, meknès, maroc. c université hassan 1er, laboratoire des sciences des matériaux, des milieux et de la modélisation (ls3m), fst settat, morocco. d materials science and nano-engineering, mohammed vi polytechnic university, lot 660 hay moulay rachid, ben guerir, morocco. e equipe sciences des matériaux, bp509, fst-errachidia, morocco. e-mail*/ hailyelmehdi@gmail.com / +212659168872 abstract a phosphate bi2o3-bao-p2o5 (bbp) glass is added to batio3 ceramics (bt) to investigate its influence on densification, rearrangement of structural units, and dielectric properties of the elaborated composites. the bt ceramic is elaborated by the solid-state method while the glasses bao-bi2o3-p2o5 (bbp) are synthetized by melting-quench process. the synthesized composites are labeled bt-xbbp (x = 2.5, 5, and 7.5 wt %) where x stands for the glass content in weight percent. it is found that the glass addition induces a decrease of their densification and helps their sintering at lower temperatures. a composite (x=5) exhibits the lowest sintering temperature at 900°c. the composition dependence of the dielectric properties shows that a material (x= 5) has the highest dielectric constant at room temperature. the p-e plots are carried out and the energy storage parameters (density and efficiency) of the composites are determined. these parameters are affected by the porosity and the remnant polarization of the composites. keywords: phosphate, glasses, composite, dielectric properties, energy storage. https://sites.google.com/site/tramp2019marrakech/ mailto:hailyelmehdi@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p67 or037 magneto(di)electric effects in barium-lead m-type hexaferrites mikheykin a.s.1*, razumnaya a.g.1, alyabyeva l. n.2, shirokov v.b.1,3, anokhin a.s.3 1southern federal university, rostov-on-don, russian federation 2moscow institute of physics and technology, moscow, russian federation 3southern scientific centre, russian academy of sciences, rostov-on-don, russian federation e-mail*/ aleksey.mikheykin@gmail.com abstract hexagonal ferrites (ba,pb)fe12o19 are completely new family of magnetic quantum paraelectrics and significance of the feo5 bipyramid structural units of m-type hexaferrites goes beyond quantum paraelectrics only. in principle, a variety of dielectric materials could be expected on the basis of the non-d0 electric dipole while electric polarization in conventional ferroelectric oxides usually involves nonmagnetic transition-metal ions with an empty d-shell. the deviation from «rule of empty shell» will lead to the appearance of new magnetoelectric multiferroic. we investigated interaction of dynamically disordered magnetic ion in a bipyramidal unit with a stereo-active lone pair of lead ion in the crystal structure of solid solutions ba1xpbxfe12o19 (x =0, 0.3, 0.5, 0.7, 0.9, 1) by single-crystal x-ray diffraction (beamline p24 chemical crystallography, petra iii at desy) and thz-spectroscopy in temperature range of 10-300 k. spectroscopic studies shown the presence of a number of low-frequency lines (below 50 cm-1) below 100 k for solid solutions with x = 0.9. this indicate the activation of lattice vibrations involving large structural blocks or/and appearing of electromagnon excitation. reciprocal space maps inspection clearly shown significant thermal diffuse scattering for ba0.1pb0.9fe12o19 single crystal in contrast to other investigated samples. thereby, active disorder in the magnetic subsystem can be controlled by substituting a divalent metal with a stereoactive lone pair in m-type hexaferrites ba1-xpbxfe12o19. previously, a similar result for m-type hexaferrites was achieved only by substitution of iron ions in the multisublattice magnetic system. we shown a simpler and more technologically advanced way of influencing the magnetoelectric effect in these compositions. the proper balance between the long-range coulomb interaction and short-range pauli repulsion in a feo5 bipyramid would favor an off-center displacement of the magnetic fe3+ ions, which induces a local electric dipole in m-type hexaferrites ba1-xpbxfe12o19 solid solutions. the reported study was funded by rfbr, project number 17-02-01247. keywords: quantum paraelectrics, multiferroics, xrd, thz-spectroscopy, hexaferrites https://sites.google.com/site/tramp2019marrakech/ mailto:aleksey.mikheykin@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p68 or038 electrostatic energy storage density in 𝐍𝐚𝟎.𝟓𝐁𝐢𝟎.𝟓𝐓𝐢𝐎𝟑 based materials for potential high-temperature capacitor application manal benyoussef, jamal belhadi, abdelilah lahmar, mimoun el marssi university of picardie jules verne/ laboratory of condensed matter physics e mail*/ manalbenyoussef@gmail.com/phone:+33322827837 abstract energy storage is one of the vital technologies for a judicious utilization of energy, aiming to meet the challenge of fossil fuel depletion. furthermore, due to the concern about climate change and atmospheric pollution, great interest has been devoted to energy storage devices based on lead-free materials that present high storage capacity. one of the new areas of interest is a high energy density at high operating temperatures (>300°c) for use in applications in which materials are subjected to harsh operating conditions, such as in power electronics, deep-well oil and gas exploration, and hybrid vehicles applications. sodium bismuth titanate (abbreviated as nbt) is considered as one of the promising candidates for energy storage applications due to its interesting properties. however, pure nbtsuffers fromhigh conductivity andlarge coercive field. doping with rare earth elements was found as an appropriate way toenhance the physical properties of nbt. in the present work, we examine the influence addition of dysprosium element on the structural, electrical, and energy storage properties ofna0.5(bi1−xdyx)0.5tio3 (xdynbt) system. interestingly, the inclusion of dy3+ allows not only asubstantial decrease of the coercive fieldand increasethe resistivity of pure nbt but also to ahigh stability of the dielectric permittivity (ɛ) over a wide temperature range (~90 − 510°c) with ∆ɛ ≤ ±15% variation. further, the studied system was found to exhibit improved energy storage density of (1.2 j/cm3) at high temperatures (200°c). the obtained results are very promisingand open a great potential for high temperature power electronics applications. keywords: nbt, dielectric properties, high temperature stability, energy storage, capacitor https://sites.google.com/site/tramp2019marrakech/ mailto:manalbenyoussef@gmail.com/phone:+33322827837 third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p69 posters https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p70 p001 the theoretical and experimental characteristics of novel material based on strandberg-type hybrid complex (c6h10n2)2[co(h2o)4p2mo5o23].6h2o n. baaalla 1,2*, y. ammari3, e.k. hlil 4, r. masrour 2, a. el kenz 1 1lamcsci, laboratory of condensed matter and interdisciplinary sciences, b.p. 1014, faculty of science, mohammed v university, rabat, morocco. 2 laboratory of materials, processes, and quality, cady ayyed university, national school of applied sciences, safi, morocco. 3 laboratoire de chimie des matériaux, faculté des sciences de bizerte, université de carthage, 7021 zarzouna, bizerte, tunisia. 4 institut néel, cnrs, université grenoble alpes, grenoble, france. e-mail*/ nora.baaalla@um5s.net abstract the hybrid strandberg complex materials have attracted intensive interest due to their multifunctional properties. in this work, we report the structural, electronic and optical properties of the novel synthetized compound (c6h10n2)2[co(h2o)4p2mo5o23].6h2o, investigated successfully by the first principle calculations, based on the density functional theory (dft). the nanocrystals of (c6h10n2)2[co(h2o)4p2mo5o23].6h2o with triclinic structure were characterized by x-ray powder diffraction (xrd). the profiles of the density of states and the optical spectra including the real and imaginary part of dielectric function were presented and analyzed in detail, the results are in good agreement with experimental measurement. it is found that the compound presents a high absorption coefficient in the visible range. a systematic analysis of the experimental and theoretical results shows a good band gap and a high optical property, which reveals promising original material for advanced in optoelectronic and photovoltaic applications. keywords: (c6h10n2)2[co(h2o)4p2mo5o23].6h2o, optical properties, absorbance, electronic structure, dft. https://sites.google.com/site/tramp2019marrakech/ mailto:nora.baaalla@um5s.net third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p71 p002 features of sintering of multilayer objects baranovskyi d. i*. frantsevich institute for problems of materials science of nasu, nanotechcenter llc e-mail*/ baranovskyi.dmytro@gmail.com abstract the development of nanotechnology stimulates the improvement of methods for obtaining and researching thin films. today, thin films have a very wide range of applications, from functional coatings to the manufacture of multilayer systems such as capacitors or fuel cells. one of the most productive methods for obtaining thin films is tape casting. with this method, our team managed to get film about 1 μm in thickness. but this thickness has been reached in the green body sample, that ıs why more interesting fact is thickness after heat treatment. after all, the removal of the organic component can lead to significant shrinkage during sintering. thus, the main aim of this study is optimization of sintering process of thin films and the study of competing processes of mass transfer at different heating rates. thin films were prepared from paste based on nanosized batio3 powder with a particle size of 20-25 nm. the study of the kinetics of sintering process will be carried out in a dilatometric installation. and ınvestigation of grain growth and porous structure will be conducted at various stages of sintering, at temperatures range from 700 to 1200 °с. the resulting samples wıll be examined by using a number of techniques: optical profilometry method, xrd, microscopy, and others. keywords: thin films, tape casting, kinetics of sintering, dilatometry, profilometry method. https://sites.google.com/site/tramp2019marrakech/ mailto:baranovskyi.dmytro@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p72 p003 structural and dielectric properties of sodium niobate ceramic nanbo3 with glass additions s. benyounoussy(1,*), l.bih2,3a. el bouari1, 1. laboratory of physico-chemical of materials applied (lpcma), faculty of sciences ben m’sik, university hassan ii of casablanca, 20670, morocco 2. group of physico-chemistry of condensed matter (pcmc), faculty of sciences meknes, university moulay ismail, meknes, morocco 3. department materials and processes, ensam meknes, university moulay ismail, meknes, maroc. e-mail* : sanaa.benyounoussy@gmail.com abstract nanbo3 is a ferroelectric material which has claimed the attention of researchers and designers of equipment owing to its unique physical properties and as a basis for a class of ecologically benign active materials. hence, nanbo3 has been studied by several workers. however, less work has been reported on nanbo3 glass-ceramics. in the present work, nanbo3 has been synthesized by solid state sintering technique while the glasses has been synthesized by the conventional melt-quenching technique. the nanbo3 ceramics were synthesized by adding different contents of glass into nanbo3. two composites with different glass weight percentage have been elaborated and sintering at different temperatures. density measurements, raman spectroscopy, and scanning electron microscopy are used to characterize their structural study. electrical properties of the composite samples are carried out by impedance spectroscopy in the frequency range of 10 hz to 1 mhz under various temperatures from 300 to 473 k. keywords: phosphate glasses, sodium niobate, composite, raman spectroscopy, sem, dielectric properties. https://sites.google.com/site/tramp2019marrakech/ mailto:sanaa.benyounoussy@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p73 p004 large elastocaloric effect in liquid crystal elastomers dejvid č.*,1 marta l.,1 andraž r.,1 nikita d.,1 boštjan z.,1 zdravko k.,1 brigita r.1 1 jožef stefan institute, ljubljana, slovenia email*/ dejvid.cresnar@ijs.si abstract caloric effects are manifested in the heating or cooling a caloric material due to the application or removal, respectively, of the external field under nearly adiabatic conditions. materials with large caloric effects, such as the elastocaloric (ec) effect, have the promise of realizing new solid-state refrigeration techniques [1]. soft materials, called liquid crystal elastomers (lces), are good candidates exhibiting a large elastocaloric effect with potentially better elastocaloric responsivity than shape memory alloy wires, in which the ec temperature change of 40 k was observed at 0.8 gpa stress field [2, 3]. in this contribution a review of recent direct measurements of the ec effect in lces will be given. the ec temperature change of about 1 k was observed in mclces at relatively small stress field of 0.6 mpa [4]. soft materials can play a significant role as active cooling elements and parts of thermal diodes or regeneration material in the development of new cooling devices. references [1] x. moya et al., nature mater. 13, 439 (2014). [2] e. a. pieczyska et al., exp. mech. 46, 531 (2006). [3] i. lelidis and g. durand, phys. rev. lett. 76, 1868 (1996). [4] m. lavrič, b. zalar, b. rožič, z. kutnjak, to be published keywords: elastocaloric, liquid crystal, liquid crystal elastomers https://sites.google.com/site/tramp2019marrakech/ mailto:dejvid.cresnar@ijs.si third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p74 p005 magnetocaloric properties of the lafe13–xsix alloys: ab initio calculations and monte carlo simulation k. daoudi 1, *, h. zaari 1, a. el kenz 1, a. benyoussef 1,2,3 1 laboratory of condensed matter and interdisciplinary sciences, faculty of sciences, mohammed v university, rabat, morocco 2 materials and nanomaterials center, mascir foundation , rabat design center rue mohamed al jazouli – madinat al irfane , rabat 10 100 – morocco 3 hassan ii academy of science and technology, rabat, morocco email*/ daoudikhadijaa@gmail.com abstract magnetic refrigeration techniques based on the magnetocaloric effect (mce) have recently been demonstrated as a promising alternative to conventional vapor-cycle refrigeration. in the present work, the lafe13–xsix alloys (1.0 ≤ x ≤ 1.6) has been studied by using density functional theory implemented in quantum espresso package. giant magnetocaloric properties are determined in the framework of monte carlo simulation and the means field theory. these properties are summarized into thermodynamic quantities. the results indicate that the lafe13–xsix alloys exhibit a large magnetic entropy change over a wide temperature range. keywords: lafe13–xsix alloys, magnetocaloric materials, dft, monte carlo, means field theory. https://sites.google.com/site/tramp2019marrakech/ mailto:daoudikhadijaa@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p75 p006 cobalt doped copper oxide thin films for solar selective absorbers application hind alaakib1 e-mail*/ hind.elaakib@gmail.com abstract: in this study, undoped and cobalt doped copper oxide thin films were deposited by rf sputtering. in addition, the covered surface was varied to investigate the effect of doping percentage on the structural, electrical, morphological and optical properties of the obtained thin films. all the obtained thin film samples have good solar selectivity (>12) with low thermal emittance (<7%) and high solar absorptance (>92%). the co:cuo thin films possess high solar-selectivity value of 12 and thus could be suitable and used as a novel candidate material for selective absorber films in solar collectors for thermal energy conversion. keywords: cobalt doped cuo; thin films; optical properties; structural and electrical properties; rf sputtering; selective absorber and emissivity. https://sites.google.com/site/tramp2019marrakech/ mailto:hind.elaakib@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p76 p007 zinc chloride as precursors to elaborate zinc oxide with spin coating technique e. elmahboub, a. elhichou, and m. mansori. groupe d'étude des matériaux optoélectroniques (g.e.m.o.) f.s.t. bp 549, cadi ayyad university, marrakech, morocco e mail*/ elmahbobeelyazid@gmail.com abstract the zinc chloride is one of the precursors used to deposited the zinc oxide (zno) thin films by sol-gel spin coating technique from aqueous solution onto glasses substrates at optimum conditions. the effect of the concentration of precursor on the structural, optical and electrical properties of zno thin films has been investigated. the x-ray diffraction analysis showed typical patterns of the hexagonal zno structure for all films. the films were polycrystalline with the (002) preferred orientation. the grain size and optical band gap were evaluated for different concentrations. the optical transmittance measurements of zno thin films showed that all films are transparent in the visible regions and decrease with increase the zncl2 concentration. the film with 0.4 m zncl2 has a high crystallographic quality with an energy band gap of 3,36 ev. the produced zno thin films at optimum conditions may be useful for specific applications as transparent n-type windows in solar cells for sensor devices where large surface areas are needed. keywords: zinc oxide; thin films; nanoparticles; zinc chloride; spin coating. https://sites.google.com/site/tramp2019marrakech/ mailto:elmahbobeelyazid@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p77 p008 al:zno properties improvement by mg codoping as optical window a. el hamidi*, k. meziane, a. elhichou, a. almaggoussi groupe d’etude des matériaux optoélectroniques (gemo), fst marrakech, university cadi ayyad, bp549, av. a. khattabi, marrakech, morocco e-mail*/ eeasmaaelhamidi@gmail.com abstract in the present work, we first studied the influence of aluminum doping on the structural and optical properties of zinc oxide thin films. thus, thin layers of zinc oxide have been successfully deposited by the sol-gel technique on glass substrates under optimized experimental conditions. the ph of the solution and the annealing temperature were maintained at 10 and 500 ° c respectively. thin layers of zno were doped at different al concentrations (1%, 3%, 5% and 7%). the results of xrd showed that all the films lost the preferential orientation according to the (002) plane, while the uv results showed a decrease of the transmittance as soon as the al concentration exceeded 1%. this deterioration in optical properties led us to co-dope thin layers of zno by (mg, al) in order to improve the optical and structural properties. therefore, in a second step, we opted for codoping by simultaneously introducing aluminum and magnesium in varying proportions. the whole molar amount of impurity was maintained constant and equal to 5%. the results show that with the increase in the mg percentage, the preferential orientation of the films according to (002) improves and the transmittance reaches 80%. the optimized results were obtained for a co-doping concentration (al-mg) with a ratio of 2/1. https://sites.google.com/site/tramp2019marrakech/ mailto:eeasmaaelhamidi@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p78 p009 thermo-raman studies and electrical properties of the sr1.15na1.7nb4w1-xmoxo15 ceramics h. es-soufia* (a) equipe de physico-chimie de la matière condensée, pcmc, faculté des sciences de meknes. université moulay ismail, morocco. e-mail*/hichamessoufi@gmail.com l. biha,b (a) equipe de physico-chimie de la matière condensée, pcmc, faculté des sciences de meknès. université moulay ismail, morocco. (b) département matériaux et procédés, ensam meknès, université moulay ismail, meknès, morocco. bihlahcen@yahoo.fr h. bihc (c) département de chimie, faculté polydisciplinaire de taza, morocco. bih.hssain@usmba.ac.ma a. alimoussad, d. mezzaned (d)laboratoire de la matière condensée et nanostructure–lmcn, faculté des sciences et techniques guéliz-marrakech. morocco. aalimoussa@gmail.com, d.mezzane@gmail.com abstract the sr1.15na1.7nb4w1-xmoxo15 (0≤x≤1) ceramics, labeled snnbwm-x, were elaborated by the solid state route. their structures were studied by x-ray diffraction and raman spectroscopy and their electrical properties were investigated by impedance spectroscopy. x-ray patterns of the ceramics reveal that the substitution of tungsten by molybdenum induces a full solid solution and the compounds crystallized in single-phase tetragonal tungsten bronze (ttb) with space group p4bm. raman spectra of the snnbwm-x compounds highlighted the vibration modes of the different cations involved in the ttb structure and showed a small peak’s displacement according to the mo/w ratio. the raman peak position temperature dependence studies had allowed to identify the presence of a phase transition around the temperature te = 270°c in each compound. the investigation of the electrical properties of the snnbwm-x samples in the frequency range 20 hz–106hz at various temperatures from room temperature to 550°c showed that theses ceramics exhibited a phase transition around 270°c in agreement with the thermo-raman studies. https://sites.google.com/site/tramp2019marrakech/ mailto:hichamessoufi@gmail.com mailto:bihlahcen@yahoo.fr mailto:bih.hssain@usmba.ac.ma mailto:aalimoussa@gmail.com mailto:d.mezzane@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p79 p010 ab-initio calculation and monte carlo simulation of the multiferroic rmno3 fatima zahrae kassimi1*, a. el kenz1 and a.benyoussef123, a.rachadi1 ,h.zaari 1 1 lamcsci, physic departement, faculty of science, mohammed v university, rabat, morocco 2 institute of nanomaterials and nanotechnology, mascir, rabat, morocco 3 hassan ii academy of science and technology, rabat, morocco. e-mail*/ kassimifatimazahra68@gmail.com abstract muliferroic are multifunctionnal materials which exhabit more than one type of ordernig including magnetic, electric and elastic order. while there are numerous technological application for magnetic and ferroelectric. in this work will be focused on the electronic and magnetic properties of the pervoskite rmno3 where r is rare earth (r=tb) using ab-initio calculation and monte carlo simulation (mcs), firstly, we calculate the electronic and magnetic properties using the full-potential augmented wave (fp-lapw) implemented in the wien2ka code, we also present the results of densities of states of two up and down spin polarisations, then we will establish a physical model to describe our system, we calculate the exchange coupling and the crystal filed. finally, we study monte carlo simulation and we will compare these results with the experimental results to prove that this multifarroic exhibit also magneto-caloric coupling and can be used for magnetic refrigeration. keywords: muliferoiic, fp-lapw, monte carlo,magntocaloric,magnetic refrigeration,wien2ka https://sites.google.com/site/tramp2019marrakech/ mailto:kassimifatimazahra68@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p80 p011 synthesis of kesterite thin films: influence of annealing in vacuum m. hamici1*, p. saint-grégoire2, h. far3 1. dosage analysis and characterization laboratory, ebf department faculty of technology, setif-1 university, algeria 2. collaborating academics, 14 avenue frédéric mistral, 34110 frontignan, france 3. department of physics, exact sciences and computer science faculty mohamed seddik university ben yahia – jijel, algeria e-mail*/ hemissi_melia@yahoo.fr abstract in this work, we studied the structural, optical, and electrical properties of the quaternary and ternary compounds of the kesterite structure as a function of the annealing temperature. the chemical solution was an aqueous solution based on copper, zinc, tin and sulfur precursors. the thin layers were deposited on soda lime glass plates by the pneumatic spray method. the product was sprayed onto the glass plates initially put down on a heating plate raised to 380 ° c. the obtained layers were then annealed at 400 ° c and 500 ° c for 20 min in vaccum. we have confirmed the existence of a kesterite phase by xrd. this structure has also been checked by raman spectroscopy which shows the two peaks characteristic of kesterite. the chemical composition of the samples follows the initial stoichiometry giving ratios between the elements of the compound in agreement with the expected composition. the optical transmission of the layers was in average around 60% for quaternary compounds, and lower for the ternary compounds. the optical gaps were determined to lie between 2.02 ev and 2.21 ev in agreement with results reported by a majority of authors. the found optical and electrical properties are encouraging in the perspective of integration of such layers in photovoltaic devices. keywords: czts, czs, xrd, thin films, optical transmission, band gap, photovoltaic https://sites.google.com/site/tramp2019marrakech/ mailto:hemissi_melia@yahoo.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p81 p012 plasma electrolytic of zinc: the formation of micro-arcs or sparks on the zinc at high voltage khadoudj guessoum1*, emmanuel rocca2, delphine veys-renaux2 1. faculté de technologie, université abderrahmane mira, bejaia dz 06000, algeria 2. institut jean lamour-umr cnrs 7198, université de lorraine, bp 70239, vandoeuvre-lèsnancy-54506, france. e-mail*/ gueksabrina05@yahoo.fr abstract for several years, one of the main objectives of many processes is to fulfill the requirements of environmental standards, and to avoid the use of toxic reagents as hexavalent chromium or nickel salts. in this framework, the processes based on electrochemical conversion as anodizing can be interesting alternatives. at low voltage, below the dielectric breakdown of the interface, several processes of zinc anodizing in alkaline media were already studied for anticorrosion properties or photo-catalytic applications. moreover, many works have been devoted to the knowledge of the zinc oxidation mechanism, especially the dissolution– passivation phenomenon at low potential because of the technical importance of aqueous alkaline batteries made from this metal. at low potential, the anodic layers are mainly constituted by zincite, zno, and zinc hydroxide if the alkaline media is at low carbonate concentration. at high voltage, during the dielectric breakdown and the formation of microarcs or sparks, the development of ceramic-type coatings seems to be possible because of the high temperature reached in the electric discharges occurring at the “metal/oxide/electrolyte” interface.the aim of this work is to describe the electrochemical behavior of zinc in a large anodic voltage range (until 300 v namely beyond the dielectric breakdown) by using a dc regime. this study focuses on the influence of the koh concentration and the presence of additives, such as silicates and aluminates. different insitu electrochemical measurements in a two-electrode cell allowed a better understanding of the anodizing process with respect to the composition of the “metal/oxide/ electrolyte” interface. the anodized coatings or oxide layers were characterized by different metallographic analyses: scanning electron microscopy equipped with energy-dispersive xray spectroscopy, and x-ray diffraction. keywords: zinc, micro-arc oxidation (mao), plasma electrolytic oxidation (peo). https://sites.google.com/site/tramp2019marrakech/ mailto:gueksabrina05@yahoo.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p82 p013 structural, dielectric and impedance spectroscopy analysis of lead free(ba0,85ca0,15zr0,1ti0,9o3) ceramics synthesized by sol-gel method s.khardazia* , d.mezzanea, y.gagoub , m.amjouda a laboratoire de la matière condensée et nanostructures lmcn, f.s.t.g. université cadi ayyad, bp 549, marrakech, morocco blaboratoire de physique de la matière condensée lpmc, université jules verne de picardie, 33 rue saint-leu, 80039 amiens cédex, france e mail*/ khardazzisaid@gmail.com abstract in recent decades, there is an increasing attention paid to ferroelectric and ecological materials, both in scientific research and technology developments. in the present work, a lead free ceramics ba 0,85ca0,15zr0,1ti0,9o3(bczt) was prepared by sol-gel method. morphological and structural properties of bczt were investigated by sem and xrd technique confirmed by raman spectroscopy at room temperature, respectively. dielectric characteristics were analyzed by impedance spectroscopy. rietveld refinement indicates the formation of a single phase compound with a tetragonal structure of space group p4mm. the ceramics sintered at 1350°c exhibits a dense microstructure. the dielectric measurements of bczt were studied as a function of temperature in the frequency range of 100hz-500 khz. the variation of dielectric constant (ε’) shows a maximum value of ~4700 at the ferroelectric-paraelectric phase transition (tc= 64°c). the diffuse nature of the transition is well described by santos–eiras phenomenological model. impedance spectroscopy analysis over the frequency range of 100hz to 500 khz presents mainly grain and grain-boundary contribution above 266°c. keywords: dielectric materials, sol-gel method, phase transition, diffuse nature, https://sites.google.com/site/tramp2019marrakech/ mailto:khardazzisaid@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p83 p014 unoccupied electronic structure of graphene derived two-dimensional substrates younal ksari1*, yu-pu lin, luca giovanelli, jean-marc themlina aix-marseille université, cnrs, im2np : umr 7334, faculté des sciences de st-jérôme, 13397 marseille, france. e-mail : younal.ksari@im2np.fr email*/ younal.ksari@im2np.fr abstract the possibility of opening a gap in the electronic structure of the two-dimentional (2d) material known as graphene continues to be investigated for the development of nanoelectronics. another approach consists to further elaborate new 2d materials with original electronic properties. such 2d materials can be derived from a graphene layer or a functionalized graphene layer. by decomposition of silicon carbide sic at 1200 °c under ultra-high-vacuum it is possible to obtain several 2d substrates. depending on the annealing time it is possible to elaborate the so called buffer layer (blg) also named zero-layer graphene, a monolayer graphene above the blg, a bilayer graphene above a blg and so on until full graphitization resulting in a multi-layer graphene substrate. hydrogenation of a blg substrate under different temperature conditions allows to obtain two additional substrates called h-blg and qfsg for quasi free standing graphene, this qfsg being a decoupled monolayer graphene floating above an underlying hydrogenated substrate.all these 2d substrates have distinct electronic behaviour which may be interesting for the development of nano-electronic devices including zero gap seconductor, correlated insulator... using photoemission an inverse photoemission experiments we have studied the electronic properties of these substrates. we show for example that it is possible to modify these properties by performing nitrogen implantation in mono or bilayer graphene. from the respective properties of the h-blg and qfsg a route is suggested for the large scale production of graphene based devices [1]. references [1] yu-pu lin, younal ksari and jean-marc themlin, hydrogenation of the buffer-layer graphene on 6h-sic (0001): a possible route for the engineering of graphene-based devices nanoresearch, 8-3, p. 839-850, 2015 keywords : graphene, electronic properties, 2d materials, nanoelectronics. https://sites.google.com/site/tramp2019marrakech/ mailto:younal.ksari@im2np.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p84 p015 hydrogen storage in solid form labrousse jihad1*, a. el kenz and a. benyoussef123, h.zaari1 1lamcsci, physic department, faculty of science, mohammed v university, rabat morocco 2institute of nanomaterials and nanothechnology, mascir, rabat, morocco 3hassan ii academy of science and technology, rabat, morocco email*/ jihadlbs@gmail.com abstract the hopes of using hydrogen as an energy carrier are severely dampened by the fact that there is still no safe, high-density method available for storing hydrogen. we investigate the possibility of storing hydrogen on one of carbon's family ''graphene" , recently, several studies on graphene, the one-atom-thick membrane of carbon atoms packed in a honeycomb lattice, have highlighted the potentialities of this material for hydrogen storage and raise new hopes for the development of an efficient solid-state hydrogen storage device. here we review on-going efforts and studies on functionalized and nanostructured graphene for hydrogen storage and suggest possible developments for efficient storage/release of hydrogen under ambient conditions. we have tried to calculate the storage properties of hydrogen on a graphene sheet by using the pseudo potential quantum espresso and calculate the density of state and band structure by using the gga aproximation and then we calculated the band energy of the complete system. keywords: quantum espresso, hydrogen storage, band structure, density of states, graphene https://sites.google.com/site/tramp2019marrakech/ mailto:jihadlbs@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p85 p016 effect of ionic liquids and humidity on ionic conductivity for carboxymethyl chitin based solid polymer electrolyte m. latifia,b, a. ahmada, h. kaddamib, n.h. hassana a faculty of science and technology, school of chemical sciences and food technology, universiti kebangsaan malaysia, 43600 ukm bangi, selangor darul ehsan, malaysia. b cadi ayyad university, faculty of sciences and technologies, laboratory of organometallic and macromolecular chemistry, avenue abdelkrimelkhattabi, b.p. 549, marrakech, morocco. e-mail*/ latifimeriem@gmail.com abstract carboxymethyl chitin (cmchit) has the potential to be used as a solid polymer electrolyte (spe), it gives an ionic conductivity of the order of 10-6 scm-1 in plain films. 1-butyl-3methylimidazolium chloride and 1-butyl-3-methylimidazolium acetate (bmim[ac]), two types of ionic liquids (ils) were added to the cmchit-spe to improve the ionic conductivity. the films were prepared by solution casting method then conditioned in different atmospheres of different relative humidity. the films prepared were characterized using fourier-transform infrared spectroscopy (ftir), x-ray diffraction (xrd), field-emission scanning electron microscopy (fesem-edx), differential scanning calorimetry (dsc), electrochemical impedance spectroscopy (eis) and linear scanning voltammetry (lsv). in controlled humidity, bmim[cl] showed an optimum of ionic conductivity in the order of 10-4 s cm-1 and electrochemical stability of 1.93 v, by the addition of only 30wt. %. on the other hand, for bmim[ac], the optimum was reached with the addition of 40 wt.% for the same order of ionic conductivity and electrochemical stability of 2.93 v. keywords: carboxymethyl chitin, solid polymer electrolyte, ionic liquids, humidity. https://sites.google.com/site/tramp2019marrakech/ mailto:latifimeriem@gmail.com https://www.sigmaaldrich.com/catalog/product/aldrich/94128?lang=en&region=us https://www.sigmaaldrich.com/catalog/product/aldrich/94128?lang=en&region=us third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p86 p017 pulse-power integrated-decay technique for the measurement of thermal conductivity of nanofluid graphene in glycerol/water m. lotfi1,2, a. bakak1, a. sellam1, d. lahboub1, a. koumina1, r. heyd1 1equipe de physique des nanostructures, cadi ayyad university, ens marrakesh, morocco 2 laboratoire de nanomatériaux pour l’énergie et l’environnement (ln2e), cadi ayyad university fssm, morocco e mail*/ lotfimohamed_1999@yahoo.fr abstract we present experimental results of the thermal conductivity of nanofluid prepared by dispersing nanoparticles of graphene in glycerol/water at various concentrations in mass fraction. the measurements have been performed by the pulse-power integrated-decay technique for the measurement of thermal conductivity of nanofluid. a self-heated thermistor probe is used to deliver heat and also to measure the temperature response. our experimental technique allows a very accurate determination of the enhancement in the thermal conductivity of the fluids due to the presence of dispersed nanoparticles. measured enhancements compare well with some of the values published so far in the literature. keywords: nanofluid, graphene, glycerol, thermal conductivity. https://sites.google.com/site/tramp2019marrakech/ mailto:lotfimohamed_1999@yahoo.fr third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p87 p018 modeling the adsorption of hydrogen in the metal organic framework (mof5, connector): z(c8h4o4)3 m. el kassaoui*, a. benyoussef, a. el kenz, faculty of sciences, mohammed v university, rabat / laboratory of condensed matter and interdisciplinary sciences e-mail*/ psmajid0@gmail.com / 0615293933 abstract metal-organic frameworks (mofs) are thought to be a set of promising hydrogen storage materials; the electronic structure of porous metal-organic framework-5 mof-5 of composition zn4o 1,4benzenedicarboxylate was investigated with an ab initio method. the purpose of this work allowed us to study the structural stability, the electrical properties of the mof-5 type organometallic materials [zn4o(c8h4o4)3] and their connector (metal oxide centers) to zinc base were studied using the first calculations based on the functional density theory (dft) and using the quantum espresso code and the pbe-gga approximation. with determination of adsorption energy to contribute to a better understanding of the fundamental interactions of h2 with mof-5. the adsorption energy of the hydrogen molecule in mof-5 was studied taking into account the favorable adsorption sites (metallic, carboxylic and cyclic) and orientations (vertical, horizontal, inclined) with the energy of coupling based on the calculation of the first and second adsorption sites. in addition, the interaction between the hydrogen molecule and mof-5 is very stable and more adsorption in the organic part (cyclic site). keywords: dft; hydrogen storage; metal organic framework; adsorption energy https://sites.google.com/site/tramp2019marrakech/ mailto:psmajid0@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p88 p019 structural and microstructural analysis of ecological and nanostructured bczt thin films hanane mezzourh1,2, yassine ben cherifi1, m’barek amjoud1, daoud mezzane1, mimoun el marssi2, igor a. luk'yanchuk2 1laboratory of condensed matter and nanostructures, cadi ayyad university, marrakesh, 40000, morocco 2laboratory of condensed matter physics, university of picardy, amiens, 80039, france e-mail*/ mezzourhhanane@gmail.com abstract today, energy storage and environmental protection are the major challenges; therefore, researches have been carrying out studies in order to develop environmentallyfriendly nanomaterials with high energy density. in this study, we have developed thin films of ba0,85ca0,15ti0,9zr0,1o3 (bczt) by sol-gel via spin-coating on pt/ti/sio2/si substrates; and heat-treated at 750°c/30min. the sem micrographs showed that the six-layers bczt films are dense and homogeneous and the xrd reveled the presence of single perovskite phase at room temperature. likewise, in order to prepare bczt nanorods thin films, firstly, uniform and homogeneous tio2 nonorods have grown on fto substrates via the hydrothermal process. then, ca ions were added to the rutile phase of tio2 nonorods to form catio3 (ct) perovskite phase confirmed by x-ray diffraction analysis. in a last step, this ct perovskite nonorods will be doped by ba and zr ions to obtain bczt nanostrctured thin film that is a potential candidate for energy storage application. keywords: bczt, energy storage, hydrothermal, nanorods, sol-gel, spin-coating. https://sites.google.com/site/tramp2019marrakech/ mailto:mezzourhhanane@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p89 p020 cured cuttlebone/chitosan-heated clay composites: microstructural characterization and practical performances abdellah mourak*, mohamed hajjaji, abdelhakim alagui laboratoire de physico-chimie des matériaux et environnement, faculté des sciences semlalia, université cadi ayyad, b.p. 2390, av. pce my abdellah, 40001, marrakech, morocco email*/ abdellah.mourak@edu.uca.ac.ma abstract clay-based materials composed of geopolymers and natural fibbers, among others, could be suitable composites for building construction. so, in this study, composites of a heated kaolinitic-illitic clay and cuttlebone or chitosan (up to 10 mass%) were etched with a naoh solution (6 m), shaped as briquettes and cured at 83 °c for up to 30 days. the microstructure of the cured composites was investigated, and some of their practical performances were evaluated. the results showed that metakaolinite and illite to some extent-, and a portion of na+ ions were involved in the formation of zeolite (chabazite) and na-carbonate respectively. moreover, layers of cuttlebone or chitosan were built up around the clay particles, and the thick layers developed in the cuttlebone and in the chitosan-rich composites affected differently the zeolization process. chitosan versus cuttlebone favoured zeolization by facilitating the ions mobility, and the illite reactivity. by referring to the mechanical/physical properties of the cured naoh-etched heated clay, the bending and the compressive strengths of the cured composites as well as their water absorption increased by two-to three times. the strengthening of the composites was related mainly to the reduction of porosity (up to 40% for the cuttlebone-rich composite). keywords: heated clay-cuttlebone-chitosan-alkali-activation-microstructure https://sites.google.com/site/tramp2019marrakech/ mailto:abdellah.mourak@edu.uca.ac.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p90 p021 composites with ferroelectric properties in as2s3-sb2s3-sbi3 system mykaylo o.a.1, rubish v.m.1, gasinets s.m.1 , hreshchuk o.m.2, makar l.i.1 , pisak r.p.1, rizak i.m.1, solomon a.m.3, yukhymchuk v.o.2, yasinko t.i.1 1institute for information recording, nas of ukraine, 4, zamkovi skhody st.,88000, uzhgorod, ukraine, center.uzh@gmail.com 2v. e. lashkaryov institute of semiconductor physics, nas of ukraine, prospekt nauky, 41, kyiv 03028, ukraine 3institute of electron physics nas of ukraine, 21 universytetska st., 88017, uzhgorod, ukraine email*/ oksanamykaylo@gmail.com abstract studies of nanoscale ferroelectric materials are important in the view of both fundamental and practical aspects. the experience of obtaining crystallites in amorphous matrices, especially well known for ii-vi chalcogenides, also inspires the fabrication and investigation of glass-embedded nanoscale ferroelectric chalcogenidebased materials which are interesting with respect to sizerelated effects and possible applications. in our recent studies we present the technology of synthesis and results of investigations of glasses in new as2s3-sb2s3-sbi3 system.the glasses of as2s3sb2s3-sbi3 system with content as2s3 45, 40, 35 and 30 mol.%, sb2s3 – 27.5, 30, 32.5, 35 mol.% and sbi3 – 27.5, 30, 32.5, 35 mol.% were prepared by vacuum melting method (~0.01 pa) of the relevant mixture of as2s3, sb2s3 and sbi3 components, preliminary synthesized from high-purity elemental substances. glassy as2s3 was obtained by cooling a homogenized for 48 h melt from 780 k in air. polycrystalline sb2s3 and sbi3 were obtained by slow cooling the homogenized for 72 and 12 h melts from 900 and 445 k, respectively, to room temperature. during the synthesis, we applied the stepwise increase in temperature. the melts were periodically mixed. the melts of as2s3-sb2s3-sbi3 system were homogenized at 820-850 k for 24-36 h. cooling of the melts was carried out into cold water. nanoheterogenous structure of glasses in as2s3-sb2s3-sbi system established on the basis of raman spectra investigations. their structural network is formed by only binary structural groups with heteropolar bonds (ass3, sbs3, sbi3, asi3) and contains small amount fragments with s-s bonds. raman spectra of (as2s3)30(sb2s3)35(sbi3)35 glasses annealed at 348 k for 48h and at 328 k for 2h clearly exhibit distinct peaks at 55, 72, 113, 139 and 320 cm-1. all these peaks are characteristic for crystalline sbsi raman spectra measured at 300 k into different scattering configurations. this fact is a good agreement with the earlier data reporting on the annealing induced crystallization of sbsi phase from (as2s3)100 x(sbsi)x and (sb2s3)100-x(assi)x glasses. keywords: nanomaterials, chalcogenides, spectroscopy, glasses, ferroelectrics. https://sites.google.com/site/tramp2019marrakech/ mailto:center.uzh@gmail.com mailto:oksanamykaylo@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p91 p022 effects of volume concentration and temperature on the thermal and rheological properties of aluminum oxide /water nanofluid omar ouabouch1, mounir kriraa2, mohamed lamsaadi1 1laboratory of flows and transfers modelling, sultan moulay slimane university, faculty of sciences and technologies, b.p. 523, beni-mellal, morocco. 2laboratory of engineering, industrial management and innovation, faculty of sciences and techniques, hassan 1st university, settat, morocco. e-mail*/ ouabouch.omar@gmail.com abstract nanofluids are colloidal solutions composed of nano-sized particles suspended in a liquid that surprising thermal properties have been the subject of intense research over the past decade. this work aims to study the influence of the temperature and volume concentration of nanoparticles dispersed in a base fluid on the thermal conductivity and dynamic viscosity of the nanofluid in homogeneous suspension aluminum oxide / water, without surface pretreatment. keywords: nanofluid, nanoparticles, thermal conductivity, dynamic viscosity. https://sites.google.com/site/tramp2019marrakech/ mailto:ouabouch.omar@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p92 p023 electric and thermal insulator glass-ceramic based on cordierite from coal fly ash kamal tabita*, hanaa hajjoua, mohamed waqifa, latifa saâdia a nanostructures and condensed materials laboratory (lmcn), faculty of science and technology, cadi ayyad university, bp 549, marrakech, morocco. e-mail*/ tabit.kamal7@gmail.com abstract cordierite-based glass-ceramics have been successfully produced from coal fly ash (80.74 wt.%), magnesium hydroxide, and aluminum hydroxide. the phase crystallization was followed by thermogravimetric and differential thermal analysis, x-ray diffraction, fourier transform infrared, and scanning electron microscope. the properties of sintered materials in the range 900-1200 °c such as apparent porosity, bulk density, and mechanical parameters were measured. the results show that the increase in firing temperature from 900 °c to 1200°c induces the transformation of coal fly ash component and magnesium oxide to -cordierite with high purity. the formation of cordierite at 1200 °c involves the densification of ceramic body and the decrease in apparent porosity to 22 %. the obtained cordierite-based ceramic exhibit a thermal conductivity (1.12 w/m.°k) and compressive strength (128 mpa), which promote its application as a thermal insulator. also, the dielectric constant ( = 9.5 at 1mhz) measurement shows that the obtained ceramic can be useful as insulator for electric and electronic applications. keywords: cordierite; coal fly ash; thermal insulator; dielectric https://sites.google.com/site/tramp2019marrakech/ mailto:tabit.kamal7@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p93 p024 study of the effect of composition and temperature on the structure stability and optical properties of new tellurium based double perovskites youssef tamraoui1,2,*, f.el bachraoui1,2, f. mirinioui2, p. lazor3, wenge yang4,5, j. alami2, and bouchaib manoun1,2 1 univ hassan 1er, laboratoire rayonnement-matière et instrumentation, faculty of sciences and technology settat,university hassan 1st morocco. 2 materials science and nano-engineering department, mohammed vi polytechnic university, ben guerir, morocco. 3 department of earth sciences, uppsala university, se-752 36, uppsala, sweden 4 high pressure science and technology advanced research (hpstar), shanghai 201203, p.r. china 5 high pressure synergetic consortium (hpsync), geophysical laboratory, carnegie institution of washington, argonne, il 60439, usa e-mail*/ youssef.tamraoui@um6p.ma abstract the continual development of technology has caused a depletion of all kind of energy resources and climate change with non-predictable consequences. extensive efforts to change to renewable energies and implementing new and alternatives energy concept are required. perovskite materials have shown potential in the energy field being one of the most promising materials, such as hybrid perovskites for solar cells, solid oxide fuel cells and refrigeration technologies[1,2]. double perovskite structure typically has the chemical formula a2bb’o6. depending on the elements residing at a and b sites, different crystalline structures are possible, resulting in specific electronic and magnetic properties. fundamental understanding of the structure stability and phase transitions of these materials, under different synthesis conditions, is very important for optimizing the next generation applications-tailored energy conversion devices. in the present study, the mechanisms of self-doping together with continuous composition modulation in the ba3-xsrxteo6 (0≤x≤3) system are investigated. for x≤ 1, the exceeded sr substitutes ba on the b-site as ba2(ba1-xsrx)teo6; while for x>1, sr substitutes partial ba at a-site as (ba2-ysry)srteo6 (here, y=x-1). the structure stability and phase transition of compounds are studied using x-ray diffraction, and raman spectroscopy at ambient and elevated temperatures. at ambient temperature, a systematic structure transition (i41/a → r3m → r3 → r3m → c1) was determined, with x increasing from 0 to 3. at elevated temperatures (up to 570 °c) all structures tend to merge to the single cubic phase fm3m, indicating an expanded bonding length and a greater atomic thermal motion. the optical properties of the ba3-xsrxteo6 (0≤x≤3) system were part of the paper objective in investigating the substitution effect on the optical response. the optical properties of the compounds were significantly dependent to the symmetry change in the system and a shrink in the band gap energy values was observed as the amount of the strontium increase, at some specific amount of the substitution, some unusual behaviour were observed. references: 1. nielsen kk, engelbrecht k, andersen k. 2012;(may 2014). doi:10.1063/1.3695338 2. tamraoui y, manoun b, mirinioui f, et al. j mol struct. 2017;1131. https://sites.google.com/site/tramp2019marrakech/ mailto:youssef.tamraoui@um6p.ma third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p94 p025 a comparative study of structural and dielectric properties in lead-free bati0,89sn0,11o3 ceramics synthesized by solid state and sol-gel y. hadouch1*, d. mezzane1, m. amjoud1, e. choukri1, l. hajji1, s. merselmiz1, s.ben moumen1, s. belkhadir1, h. mezzourh1,2 1laboratory of condensed matter and nanostructures/ cadi ayyad university 2laboratory of condensed matter physics, university of picardy, amiens, 80039, france e-mail*/hadouch.younes@gmail.com abstract ferroelectric barium stannate titanate (btsn) possesses a high dielectric constant coupled with the possibility of shifting the curie temperature toward room temperature by changing the sn content. therefore, it is an interesting material for applications such as capacitor, bolometer, actuator and microwave phase shifter. bati0,89sn0,11o3 ceramics were synthesized by solid state method and sol-gel in order to realize a comparative study of two compounds and to establish a correlation between their structures and their dielectric properties. the crystalline structure, the unit cell parameters and the phase composition were ascertained by the rietveld refinement. the average grain size estimated from the microstructure was found to be about 1.5 μm for the solid-state derived ceramic and 4-14 μm for the sample prepared by sol-gel method, respectively. complex impedance spectroscopy results revealed a classical ferroelectric behavior and diffuse nature of the ferroelectric-paraelectric phase transition in each of the two samples, and highlighted the effect of grain size and density on the dielectric properties: permittivity, dielectric losses and conductivity. keywords: btsn, solid state, sol-gel, structural properties, dielectric properties, impedance spectroscopy, ferroelectricity, phase transition temperature. https://sites.google.com/site/tramp2019marrakech/ mailto:hadouch.younes@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p95 p026 tio2 photocatalysis: hydrogen production f.mezzat *1, h,zaari1, a.el kenz1, a. benyoussef2. 1lamcsci, faculty of sciences, mohammed v university of rabat, 2institute for nanomaterials and nanotechnologies, mascir, rabat, morocco 3hassan ii academy of science and technology, rabat, morocco e-mail*/ mezzat.fatimazahra@gmail.com abstract tio2 is extensively used in a variety of applications for photocatalysis and hydrogen evolution. the development of new materials, is strongly required to provide enhanced performances with respect to the photocatalytic properties and to find new uses for tio2 photocatalysis.to produce the hydrogen by using solar energy, we have been studied the band gap, and optical properties of tio2 compound, which is considerate one of the most promising photocatalyst used of water splitting.for this purpose, the doping of tio2 has been studied with nonmetallic elements and the use of one, two and three dimensional tio2 as a photocatalyst. the aims of this research are studying the crystal structure, the optical properties and the photocatalytic activity of tio2. keywords: photocatalysis, hydrogen, visible-light, tio2, photocatalyst https://sites.google.com/site/tramp2019marrakech/ mailto:mezzat.fatimazahra@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p96 p027 study of the electronic structure and magnetic properties of material dymn2o5 using ab-intio and montecarlo simulation y. kaddar 1*, h. zaari1, a. rachadi1, a. el kenz1, a.benyoussef1,2,3 1 laboratoire de matière condensée et sciences interdisciplinaires, faculty of sciences, mohammed v university of rabat, morocco 2 institute of nanomaterials and nanotechnology, mascir, rabat, morocco 3 hassan ii academy of science and technology, rabat, morocco e-mail*/ younesskaddar@gmail.com abstract we use ab-inition methods with the density functional theory (dft) to study the electronic and magnetic proprieties of multiferioc dymn2o5.our goals are to determine the band gap the magnetic anisotropy and exchanges couplings between the magnetic ions. the density of states show an semiconductor behavior in the ferrimagnetic state of dymn2o5 at fermi level and there is a small band gap, confirming the experimental fact that dymn2o5 as a typical semiconductor. the exchange couplings between the magnetic ions were calculated using the heisenberg model by including only the nearest neighbor interactions, all by selecting stable magnetic configurations. the magnetic properties of the ferrimagnetic dymn2o5 compound were studied using monte carlo simulations. https://sites.google.com/site/tramp2019marrakech/ mailto:younesskaddar@gmail.com third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p97 p028 comparative study of the solid state reaction of ni/gaas and ni/inas s. rabhia,b*, c. perrin-pellegrinoa, m.c. benoudiab , k. hoummadaa a institut matériaux microélectronique nanosciences de provence (im2np), aix-marseille université (amu), france b laboratoire mines métallurgie matériaux (l3m), ecole nationale supérieure des mines et de la métallurgie (ensmm), annaba, algérie. e-mail*/ selma.rabhi@ensmm-annaba.dz abstract recently, research has turned to iii-v semiconductors for the development of future electronic and optoelectronic devices at the nanoscale [1]. the semiconductor iii-v ingaas with well-defined proportions is the most studied to substitute si on mosfet technology [2]. with the same lattice parameter, it can be deposited on si substrate. good electric contact between metal and iii-v still remains a challenging issue for several applications. in one possible integration flow, the fabrication of these contacts is based on the reactive diffusion process in the same way as with si substrates allowing to improve the ohmic resistance contact between iii-v semiconductors and metal [3-4]. however, as a first step to simplify the understanding of the different phenomena that can occur the study of different manufacturing processes has been focused on gaas and inas rather than on ingaas. for this, we have studied the nature and the sequence of the phases formed for the two systems ni / gaas and ni / inas, where ni is deposited by sputtering. we have used in this study xray diffraction in-situ and ex-situ with different diffractometers (two circles and four circles), scanning and transmission electronic microscopies. the solid-state reaction between a ni film and gaas and inas substrates during annealing (below 400 °c) gives a ternary intermetallic as the first phase formed for two systems, they are in epitaxy with the substrate and have the same hexagonal structure. this phases are ni3gaas [5] and ni3inas phases. moreover, the texture of the ni3gaas phase is different from the ni3inas phase. at high temperatures (above 400 ° c), we observe for both systems the presence of new phases. these are hexagonal and cubic structures for the ni / inas system and just one phase hexagonal for the ni/ gaas. references [1] p. srinivasan and al, graphene, ge/iii-v, and emerging materials for post-cmos applications 2, ecs transa, 2010. [2]s. oktyabrsky, y. peide, fundamentals of iii-v semiconductor mosfets, springer, 2010. [3]s. oda, d.k. ferry, nanoscale silicon devices, crc press, 2017. [4]d.b. shiban tiku, iii-v integrated circuit fabrication technology, crc press, 2016. [5] s. rabhi and al, scr. mater. 141 (2017) 28–31. keywords: ni/gaas, ni/inas, epitaxy, ni3gaas, ni3inas, reactive-diffusion, formation kinetics, in-situ structural characterization. https://sites.google.com/site/tramp2019marrakech/ mailto:selma.rabhi@ensmm-annaba.dz third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p98 index adiabatic .......................................................................................................................................... 15, 86 alloys ....................................................................................... 2, 13, 15, 24, 25, 26, 35, 39, 40, 51, 54, 87 anisotropy ................................................................................................................................ 24, 26, 116 atomic ..................................................................................................................... 13, 31, 53, 59, 68, 112 bandgap ........................................................................................................................................... 39, 61 capacity................................................................................................................................ 46, 57, 65, 81 catalysis ..................................................................................................................................... 42, 68, 76 ceramics ........................................ 19, 22, 27, 32, 44, 45, 52, 53, 55, 63, 66, 67, 78, 85, 92, 97, 111, 113 chemistry .......................................................................................................................... 7, 13, 48, 76, 85 coercive ............................................................................................................................... 26, 58, 70, 81 concentrations .............................................................................................................. 39, 57, 90, 91, 102 conductivity ...................................................................... 7, 27, 44, 55, 81, 101, 102, 103, 110, 111, 114 crystal ........................................................................... 15, 17, 26, 31, 32, 33, 52, 57, 79, 86, 87, 93, 115 depolarizing ........................................................................................................................................... 11 dielectric ....... 15, 20, 22, 27, 36, 41, 44, 46, 50, 52, 58, 63, 64, 65, 66, 73, 74, 78, 79, 81, 83, 85, 96, 97, 111, 113, 114 diffraction .......... 32, 38, 44, 51, 52, 53, 56, 58, 59, 62, 70, 72, 76, 79, 83, 90, 92, 96, 101, 105, 111, 112 distribution ............................................................................................................... 10, 11, 31, 38, 45, 48 doping ........................................................................................... 30, 51, 55, 64, 67, 70, 89, 91, 112, 115 elastic ........................................................................................................................ 21, 24, 27, 45, 65, 93 electrocaloric ...................................................................................................................... 19, 52, 58 electrode ..................................................................................................................................... 9, 56, 96 emission ............................................................................................................................. 24, 34, 76, 101 environment .................................................................................................................................... 67, 83 epitaxial ................................................................................................................................................. 32 ferroelectric ..... 11, 15, 19, 20, 22, 27, 30, 32, 36, 50, 52, 53, 58, 60, 64, 66, 73, 79, 85, 93, 97, 108, 113 frequency................................................................................................ 10, 26, 32, 41, 55, 79, 85, 92, 97 gap .............................................................................................. 40, 59, 68, 83, 90, 95, 99, 112, 115, 116 growth .................................................................................................................. 7, 24, 31, 33, 39, 55, 84 heterostructures .................................................................................................................. 32, 60, 61, 73 hysteresis .................................................................................................................. 22, 41, 44, 52, 61, 66 impedance ...................................................................................................... 44, 67, 85, 92, 97, 113, 114 irradiation .............................................................................................................................................. 11 lead ............................................................. 13, 19, 20, 22, 36, 39, 50, 52, 56, 58, 66, 79, 81, 84, 97, 113 magnetic .......................................................................................................................................... 26, 68 memory ..................................................................................................................................... 15, 27, 86 metallic .................................................................................................................................... 10, 31, 115 metals ........................................................................................................................................ 17, 25, 53 microstructure ............................................................ 23, 25, 39, 43, 48, 51, 54, 64, 66, 67, 97, 107, 113 nanodomains ......................................................................................................................................... 73 nanomaterials ........................................................................ 2, 11, 60, 64, 68, 70, 87, 93, 100, 115, 116 nanoregions ........................................................................................................................................... 64 nanostructured ............................................................................................................................ 100, 105 nanostructures ................................................................................... 3, 5, 44, 52, 72, 102, 105, 111, 113 nanotubes ................................................................................................................................................ 7 nanowires ................................................................................................................................................ 8 https://sites.google.com/site/tramp2019marrakech/ third international symposium nanomaterials: microstructure and properties –tramp19– https://sites.google.com/site/tramp2019marrakech/ oaj materials and devices, vol 4 #2, 2912 (2019) – doi: 10.23647/ca.md20192912 p99 organic ............................................................................................................ 43, 50, 61, 76, 84, 103, 104 paraelectric ................................................................................................................... 27, 52, 73, 98, 113 paramagnetic ......................................................................................................................................... 27 passivation ............................................................................................................................................. 96 permittivity ................................................................................................................... 44, 52, 58, 81, 114 perovskite ..................................................................................................................................... 27, 68 photovoltaic .................................................................................................................................... 83, 95 polar .................................................................................................................................... 27, 32, 64, 73 polarization ................................................................................................... 11, 27, 41, 50, 60, 66, 78, 79 raman ......................................................................... 22, 32, 33, 38, 44, 58, 64, 85, 92, 95, 97, 108, 112 relaxor ................................................................................................................................................... 15 semiconductor ................................................................................................ 31, 39, 51, 53, 61, 116, 117 simulation ................................................................................................... 45, 60, 61, 62, 75, 87, 93, 116 sol-gel ............................................................................................... 50, 63, 67, 90, 91, 97, 105, 113, 114 spectra .................................................................................................................... 32, 64, 70, 83, 92, 108 spectroscopy ... 32, 33, 38, 44, 52, 58, 63, 67, 72, 76, 79, 80, 85, 92, 95, 96, 97, 101, 109, 112, 113, 114 spin ................................................................................................................... 27, 29, 43, 68, 90, 93, 105 storage ........................................ 9, 11, 17, 18, 22, 36, 41, 44, 45, 56, 68, 78, 79, 81, 100, 103, 104, 105 strain .................................................................................................................................... 10, 24, 25, 29 structural .. 7, 17, 22, 25, 27, 29, 31, 32, 35, 38, 44, 45, 56, 57, 59, 67, 68, 70, 73, 78, 79, 81, 83, 85, 89, 90, 91, 95, 97, 103, 105, 108, 113, 114, 117 structure7, 9, 17, 21, 22, 23, 24, 29, 30, 31, 33, 44, 45, 50, 52, 53, 54, 55, 56, 62, 64, 66, 73, 76, 79, 83, 84, 90, 92, 95, 97, 99, 100, 103, 108, 112, 113, 115, 117 substitution ...................................................................................................... 17, 22, 52, 70, 79, 92, 112 substrate ............................................................................................... 21, 29, 33, 39, 42, 53, 73, 99, 117 superlattices .............................................................................................................................. 11, 32, 73 susceptibility .......................................................................................................................................... 73 symmetry ............................................................................................................................................. 112 synthesis ............................................................................................................................................ 2, 61 thin ................................................................................................................................... 2, 31, 84, 90, 91 transition .................................... 15, 17, 23, 24, 25, 27, 30, 50, 52, 58, 64, 68, 79, 92, 98, 112, 113, 114 transmission ............................................................................................................................ 14, 42, 117 vibrational ............................................................................................................................................. 38 https://sites.google.com/site/tramp2019marrakech/ slide 1