IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Effects of Temperature on Thermodynamic parameters and Carbon Nanotubes Growth Rate on Aluminum Electrode in Electrochemical deposition Process Received in : 11 April 2010 Accepte d in : 27 September 2010 A. I. Rasheed Departme nt of Chemistry , College of Science ,Al-Mustansiriyah Unive rsity Abstract The op timum p rocess conditions of the electrochemical deposition of carbon nanotubes (CNT ) have been established by using developed, cheap and simp le sy st em. It has been found that t emp erature affects on t he rate, purity and the y ield of CNT obtained in this p rocess. The electrochemical behavior of CNT deposition, kinetic and thermody namic p arameters were also discussed. Key words: Thermodynamic parame ters, Carbon Nanotubes, Electrochemical deposition Introduction Since the discovery by Sumio Iijima [1], CNT s has a great deal of att ention, and a number of app lications have been p rop osed and demonst rated [2-5] Carbon nanotubes have increasingly been st udied in recent y ears owing to their imp ortant p rop erties and a wide variety of p otential app lications [6]. Elemental carbon has sp 2 hy bridization can form a variety of amazing st ructures [7]. It is well known that graphite carbon can build closed and op en cages as a honeycomb atomic arrangement. The nanotubes consisted of one (so called single-walled carbon nanotubes (SWCNTs) with diameters range from~1nm) or several cylindrical lay ers of rolled up grapheme sheets (so called multi-walled carbon nanotubes (M WCNTs)) with inter lay er sp acing of (0.34-0.36) nm and diameter to~30nm.The length of nanotube is usually over 1µm.These lay ers are in most cases helical i.e., the carbon bonds form a sp iral around the cylinder [8]. The carbon nanotubes may be used, for examp le, as cataly st sup p ort or semiconductor [9-10]. Several main methods are currently used for sy nthesis of carbon nanotubes, i.e. carbon sy nthesis [11]; chemical vapor deposition (CVD)[12] M icrowaves technique [13] laser vaporization [14] electrochemical deposition [15].Although the production of CNT s is quite simple, it is up -to-now very difficult to obtain samples of good quality , containing as less contaminating material (nanoparticales, amorp hous or graphitic microparticales) as p ossible, with tubes showing well-defined graphitized lay ers and tips. The effect of the reaction temp erature on growt h rate, thermody namic p arameters and on the quality and quantity of carbon nanotubes formed in the electrochemical deposition have been studied. Experime ntal All chemicals were reagent grade or the highest available commercial grade and were used as received. Deionized water was obtained from an Auto st ill water sy st em (YAM AT O Co., Ltd. WG25). CNTs were sy nthesized by electrolysis using acetonitrile and de-ionized IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 water (1% v/v) as electrolyte. Electrolysis was carried out at atmosp heric p ressure and the temp erature was varied as (288, 298, 308, 318, 328, 338 and 348) K using hotp late st irrer. Carbon nanotubes were deposited onto Aluminum sheet Size (0.5x30x100mm) att ached to a copp er cathode. Grap hite was used as the counter electrode (anode). Before mounting the substrates on t he cathode, they were thoroughly cleaned and rinsed with de-ionized water and Ethanol solution resp ectively. The electrodes were sep arated by a distance of ~10mm. The app lied d.c. voltage between the electrodes was kep t ~24 V using a d.c. p ower sup p ly cap able of generating Stabilized voltage (24 V, 24A).6264B DC p ower sup p ly HEWLETT .PACKARD. The deposition was carried out for ~ (4-6) h. The deposit was characterized by X-ray Diffraction (XRD) (SHIM ADZU XRD-6000) Fourier Transform Infra Red sp ectroscop y (FT IR) (Shimadzu 8400s). M icroscop e (NIKON ECLIPSE M E600), Scanning Electron M icroscop e (SEM ). Results and Discussion In our p revious st udy , we found that t he hy drocarbon deposition on the nanocry st alline aluminum oxide hy droxide cataly st is created in two forms: one as single-walled carbon nanotubes in colloidal and p recipitant forms and second as a multi-walled carbon nanotubes deposit on aluminum substrate [16] as shown in Figure .1. It was found that acetonitrile can be an effective carbon source for the growt h of multi-walled carbon nanotubes. The quantity and quality of these materials depended on different p arameters, such as: temp erature, reaction time and the CH3CN:H2O ratio. Fig. 2. Illust rates the relation between the CNT s growt h with the time at different temp eratures varying from (288-348) K and have a similar shap es but with different characterist ics and behaviors at all temp eratures of exp eriments. It is an indication that the reaction rate of CNT s deposit formation varies in direct p rop ortion with variation of cell temp erature. From this Figure we can see that low temp erature deposition p rocesses need about 45 minutes to st art flowing ions between electrodes due to p reparing aluminum oxide hy droxide film on aluminum substrate, while high temp erature p rocesses need about 15 minutes to st art CNTs dep osition . In this work, also the relationship between varying temp erature of the electrolyte with the rate of CNT s growt h and with electrolyte conductivity have been st udied as shown in Figures ( 3 and 4) resp ectively. The results indicated that as the temp erature rising from 288 K to 318K the CNT s growt h rate or electrolyte conductivity caused no significance, while above 318 K the rate of CNT s growt h and electroly te conductivity rise vigorously till 338 K and then drop vigorously with rising temp erature because of the growing of the reversible reaction in the electrolyte at high temp eratures. The effect of temp erature on the p urity of CNT s obtained during this p rocess has been followed by IR sp ectroscop y . The IR sp ectra shown in Figure 5(a & b) app eared that CNT s sample p repared at (308 K) the absorp tion band (1350 cm -1 ) which related to t he absorp tion of carbonaceous imp urities (amorp hous carbon) was very st rong, and the absorp tion band (1637cm -1 ) which related to the absorp tion of carbon nanotubes surrounded with imp urities absorp tion bands. While in Fig. 4(b) where the sample p repared at (338 K) CNTs absorp tion band (1637cm -1 ) clearly app ears and imp urities absorp tion bands disap p ears. T hat’s due to the vigorously rising of the rate of reaction with rising cell temp erature and this means that reaction at high temp erature consumes all the amorp hous carbon in building CNT s while at (308 K) the reaction rate was very slow and there is a large amount of non used amorp hous carbon. IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 The rate constants at temp erature range (288-348) K for this p rocess were determined by p lott ing in current versus. time of CNT s growt h, these different results were tabulated in Table(1). These results indicate that the values of rate constant increase with the increase of temp erature as p reviously shown in figure (2). This st udy indicates that t he optimum temperature was 338 K and the amount of CNTs decrease after reaching at 348 K. Plotting ln (t1/2) against ln (current) in Fig.6. shows a linear relationship which p rove that the reaction is first order. The kinetic and thermody namic p arameters were studied in this work. From slop and intercep t of Arrhenius p lot shown in figure -7- get the activation energy and the pre-exp onantional value (A) which equal to 34.8 kJ.mole -1 and 194.9 s -1 resp ectively. From these values the thermody namic p arameters ∆ * H, ∆ * S and ∆ * G were calculated according to equation below [17]: ∆ * H = Ea – RT - - - - - - - - - - - - - - (1) And ∆ * S from A = e (kBT/h) e (∆*S/ R) - - - - - - - - - - (2) Therefore ∆ * G is calculated at different temp eratures from 288 K to 348 K from equation ∆ * G = ∆ * H - T ∆ * S -------------------------- (3) All results are listed in Table .2. Entrop y changes (∆ * S) calculated from p lott ing of Gibbs free energy against temp erature (Fig. 7.), it was found equal to -209.6 Jmole -1 K -1 The p ositive values of ∆ * G gives an indication of non-sp ontaneous p rocess as one exp ected. The p rocess was endothermic due to p ositive values of ∆ * H (increasing temp erature during p rocess) i.e., that higher temp eratures are favored for enhanced removal of carbon ions from graphite electrode to growt h CNT s. Therefore the ∆ * S was negative and small values suggest the decrease in adsorbate concentration in solid-solution interface indicating thereby the increase in sorbate concentration onto the solid p hase, means that the formation of CNTs is less disorder. Conclusion From this work, one can conclude that the reaction temp erature play s a critical role on the rate, y ield and p urity for p roducing CNT . The thermody namic values indicate the non- sp ontaneous, endothermic and more regular sy st em. Re ferences 1. Iijima, s. (1991) "Helical microstructures of graphitic carbon", Nature; 354: 56-57. 2. Cao, S.; Tao-Zu, Z.; Lemaitre, M . G.; Xia, M . G.; Shim, M . and Rogers, J. A. (2006) "Transp arent flexible or ganic thin-film transistors that use p rinted single-walled carbon nanotube electrodes" App lied Physics Letters, 88: 1135111-1135113. 3. Yoo, E.; Habe, T. and Nakamura, J. (2005) "Possibilities of atomic hy drogen st orage by cabon nanotubes or graphite materials", Science and Technology of Advanced M aterials; 6: 615-619. IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 4. Sear, K.; Dumee, L.; Schütz , J.; She, M .; Huy nh, C.; Hawkins, D.M . and Gray , S. (2010) " Recent develop ments in carbon nanotubes membranes for water p urification and gas sep aration", M aterials; 3: 127-149. 5. Baughman, R.H.; Zakhidov, A.A. and de Heer, W.A. (2002) "Carbon nanotubes- the route toward ap p lications- review ", Sience; 297: 787-297. 6. M orinobu, E.; Takuay a, H.; Yoong, A.K.; M auricio, T. and M ilred, S.; D., (2004): "Ap p lications of carbon nanotubes in the twenty -first century ", Phil. Trans. R. Soc. Lond. A 362: 2223–2238. 7. Dong, Q.; Gregory , J.W.; Wing, K.L.; M in-Feng, Y. and Rodney, S.R. (2002) "M echanics of carbon nanotubes", Ap p l. M ech. Rev 55: 495-533. 8. Bonard, J.; M .; Forro, L.; Ugate, D.; De Heer, W.A. and Chatelain, A, (1998) "Phy sics and chemistry of carbon nanostructures", Europ ean Chemisrty Chronicale 3: 9-16. 9. Chen, G.X.; Kim, H.S.; Park, B.H. and Yoon, J.S., (2006) "M ulti-walled carbon reinforced nanotubes ny lon 6 composites" Poly mer; 47: 4760–4767. 10. Samal, S.S.; Bal, S. (2008) "Carbon nanotube reinforced ceramic matrix comp osite-a review" M inerals and M aterials Charactization and Engineering; 7(4): 355-370. 11. Babanejad, S.A.R.; M alekfar, R. and Seyy ed Hosseini, S.M . R., (2009): "Disp ersive M icro Raman Backscatt ering Sp ectroscop y Investigation of Arc Discharge Sy nthesized CNT s Dop ed by Boron and Nitrogen", Acta Phy sica Polonica A.; 116: 217-220. 12. Arjmadi, N.; Sasanpour, P. and Rashidian, B., (2009): "CVD sy nthesis of small- diameter single-walled carbon nanotubes on silicon" Computer Science & Engineering and Electrical Engineering 16(1): 61-64. 13. Kharissova, O.V.; Catanon, M .G.; Pinero, H.J.L. and M endez, U.O., (2009): "Fast p roduction method of Fe-filled carbon nanotubes"M echanics of Advanced M aterials and Structures, 16: 63-68. 14. Puretzky A. A.; Schittenhelm, H.; Fan, X.; Lance, M .J.; Allard, Jr.L. F. and Geohegan, D.B., (2002): "Investigations of single-wall carbon nanotube growt h by time-rest ricted laser vaporization" The American Phy sical Society .; 65: 245-425. 15. Pal, A.K.; Roy , R.K.; M andal, S.K. and Deb, G.B., (2005): Electrodeposited carbon nanotubes t hin films", T hin Soild Films.; 476: 288-294. 16. Hussain, D.H.; Rasheed, A.I. and Faisal, A.D., (2010): "Sy nthesis of carbon nanotubes by electrochemical deposition using Aluminu m subst rate", Sp ecial Edition Researchers of T he 6 th confer ence College of Science Al-M ust ansiriy ah University from 9-10 Februray , Al-M ustansiriy ah Journal of Science.; 21(5) : 168-174. 17. Laidler, K.J.; M eiser, J.H. and Sauctuary, B.C., (2003): "Phsical Chemist ry ", 4 th Edition Houghton M ifflin Comp any Bost on New York pp 383-394. Table(1): the values of rate constant. 348 338 328 318 308 298 288 Temp . K 0.0004 0.0008 0.00069 0.00028 0.00026 0.00016 0.0001 kobs.s -1 0.9909 0.9300 0.9170 0.9524 0.9471 0.9923 0.9565 R 2 IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Table (2): Thermodynami c paramete rs of ∆ * H, ∆ * S and ∆ * G. Temp . K ∆ * H kJ.mole -1 ∆ * S J.mole -1 .K -1 ∆ * G kJ.mole -1 288 32.405 -209.10 92.597 298 32.322 -209.39 94.723 308 32.239 -209.66 96.814 318 32.156 -209.92 98.910 328 32.073 -210.19 101.015 338 31.989 -210.44 103.033 348 31.906 -210.68 105.222 Fig.(1): S chematic diagram and a Photo of CNT deposi t on Aluminum electrode form S EM. Fig. (2): Rel ationship between CNTs growth with deposi tion ti me of different temperatures (288-348) K. IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Fig. (3): The effect of temperature on CNTs Fig.(4): The effect of temperature on growth rate during deposition process. ele ctrolyte conductivity during CNTs growth process. Wavenumber (cm -1 ) T ra n sm it ta n ce % IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 w Fig. (5): IR S pectra of prepared CNTs sample (a) at 308 K (b) at 338 K. Fig. (6): Rel ationshi p between l n t1/2 vs. l n current at 288 K. T ra n sm it ta n ce % b IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Fig. (7): Plot of Arrhe ni us rel ationshi p for CNTs growth. Fig. (8): Changes of Gibbs free ene rgy against te mperature. 2011) 1( 24المجلد مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة القیم الثرمودینامیكیة ومعدل سرعة نمو األنابیب فيتأثیرات درجة الحرارة النانونیة للكربون المترسبة على قطب األلمنیوم بطریقة الترسیب الكهربائي 2010نیسان 11:استلم البحث في 2010أیلول 27: قبل البحث في عبدالجبار إبراهیم رشید الجامعة المستنصریة ،كلیة العلوم ،قسم الكیمیاء الخــالصـــة CNT( هذا البحث تثبیت ظروف العمل المثلى لترسیب االنابیب النانویـة للكربـون تم في s ( باسـتخدام CNT)(ص وبسیط في عملیة الترسیب الكهروكیمیائي للـجهاز مطور ورخی s.اوجد في هذا العمل إن لدرجـة الحـرارة تـأثیر ،اذ CNT(سرعة التفاعل والنقاوة وكمیة الناتج من الــ في s .( ولهذا السبب فإَن مـن الظـروري التحقـق مـن السـلوك الكهروكیمیـائي .ودینامیكیة ودراسة القیم الحركیة والثرم) CNT(لعملیة ترسیب الـ ، األنابیب النانونیة للكاربون،طریقة الترسیب الكهربائي القیم الثرمودینامیكیة : الكلمات المفتاحیة