فاضل ومحمد وزينب Al-Khwarizmi Engineering Journal,Vol. 12, No. Physical and Mechanical Properties Fadhil A. Chyad* *,**,***Department of (Received Abstract Nanoferrite materials have been synthesized by sol percentages of Y2O3 (0.34 µ m) on the 0.9(Co4Fe2O4) 0.1] by adding 10% Cobalt ferrite absorption) were affected by the doping, where drastically decreased about 80% at 6% strength and Vickers microhardnss). The fracture strength at 1 % and then decreased. The same behavior shows with microscopy ) micrographs revealed that the microstructure of the fracture surface of the samples consist of detached approximately closely packed particles and also showed the formation of By doping with Y2O3 the pores decreased and a dense material obtained Keywords: Nanoferrite, Y2O3, density, splitting 1. Introduction Nano crystalline lithium ferrite has been investigated with last years due to its potential use in the microwaves field as a replacement for garnets or as a memory core [1, 2 important in construction and engineering of many electromagnetic and microwave lithium ferrite has been widely investigated material [2,3]. This material crystallizes in t spinal structure AB2O4, where A and B denote lattice site tetrahedrally and octahedrally coordinated by oxygen respectively[4] .Lithium ferrite is an unusual and in the same respect, a remarkable material. Where, several research programs have been undertaken to study its fundamental properties and to develop high-power microwave materials from it. distinctive properties of lithium ferrite are the following: 1- The lithium ion is monovalent; i.e., in order to preserve charge balance, L��enters the lattice in combination with F��� ion. The compound may Khwarizmi Engineering Journal,Vol. 12, No. 2, P.P. 10- 17 (2016) Mechanical Properties of Synthesized Doped Nanoferrite * Mohammed S. Hamza** Zainab Department of Materials Engineering/ University of Technology *Email: fchyad_2009@yahoo.de **Email: Dr.msh2013@yaho.com (Received 26 June 2015; accepted 27 January 2016) Nanoferrite materials have been synthesized by sol-gel auto combustion method. The effect of doping different ) on the physical and mechanical properties of selected mixed by adding 10% Cobalt ferrite was studied. Physical properties (i.e. .density, porosity doping, where the density increased about 32% at 6 wt% Y Y2O3 and has a correlation effect on the mechanical properties( The fracture strength at 1 % wt. of Y2O3 has doubled value of the undoped sample same behavior shows with the testing of Vickers micro hardness micrographs revealed that the microstructure of the fracture surface of the samples consist of detached approximately closely packed particles and also showed the formation of micro agglomerated the pores decreased and a dense material obtained splitting strength, Vickers micro hardness. Nano crystalline lithium ferrite has been investigated with last years due to its potential use field as a replacement for , 2]. Due to its important in construction and engineering of many electromagnetic and microwave devices, lithium ferrite has been widely investigated material [2,3]. This material crystallizes in the where A and B denote lattice site tetrahedrally and octahedrally oxygen ions Lithium ferrite is an unusual and in the same respect, a remarkable material. Where, several research programs have been undertaken to study its fundamental properties and to develop power microwave materials from it. The hium ferrite are the The lithium ion is monovalent; i.e., in order to enters the lattice in ion. The compound may be thought of as (L��.�F�� can be prepared with low value of 2- An ionic ordering can be established in lithium ferrite. Lithium enters the spinel lattice on the octahedral sites (i.e., the spinel is inverted). The rare earth ions have unpaired 4f electrons that have a role to originate magnetic anisotropy due to their orbital shape crystalline anisotropy in ferrite in related to 4f coupling between the transition earth ions, thereby doping rare Li-Fe ferrite can improve their electrical and magnetic properties[5]. (2006), investigated the thermal decomposition of freeze - dried Li-Mn (II) precursor by differential thermal analysis thermal gravimetric analysis spectroscopy. It was found that the thermal decomposition of a homogeneous freeze lithium manganese Tiron formats, followed by an annealing, is a suitable method for preparing a single phase solid solution ferrite (Li O4, with 0 X 1), at relatively low temperature [6]. Altavilla et al. (2009), have been studied the Al-Khwarizmi Engineering Journal (2016) Synthesized Doped Nanoferrite Zainab I. Dhary*** Technology method. The effect of doping different properties of selected mixed ferrite [(Li2.5Fe0.5) density, porosity and water Y2O3, while porosity has a on the mechanical properties(Splitting tensile has doubled value of the undoped sample micro hardness.SEM ( Scanning electron micrographs revealed that the microstructure of the fracture surface of the samples consist of detached agglomerated particles with some voids . �.�)Fe2O4. Lithium ferrite can be prepared with low value of ∆H. An ionic ordering can be established in lithium ferrite. Lithium enters the spinel lattice on the octahedral sites (i.e., the spinel is inverted). The rare earth ions have unpaired 4f electrons role to originate magnetic anisotropy due to their orbital shape, where the magneto- crystalline anisotropy in ferrite in related to 4f-3d coupling between the transition metal and rare doping rare-earth into spinal prove their electrical and Wende and Langbein investigated the thermal decomposition of Mn (II)-Fe (III) formatted differential thermal analysis ( DTA), thermal gravimetric analysis (TGA) and mass spectroscopy. It was found that the thermal decomposition of a homogeneous freeze - dried iron formats, followed by an annealing, is a suitable method for preparing a single phase solid solution ferrite (LiXMn1-XFe2-2X 1), at relatively low temperature Altavilla et al. (2009), have been studied the Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 11 synthesis of monodispersed Fe2O4 (M=Fe, Co, Ni) ferrite nanoparticles: effect of reaction temperature on the particle size. The possibility of preparing monodispersed transition metal-oxides nano- particles covered by functionalized long chain organic molecules, in the sub size range of 20 nm, has recently opened an entire field of research [7]. De Fazio et al. (2011), showed the electromagnetic properties of manganese-zinc ferrite with lithium substitution. Polycrystalline manganese-zinc ferrite with lithium substitution of composition Li0.5xMn0.4Zn0.6-xFe 2+ 0.5xO4 (0.0≤ x≤ 0.4) were prepared by the usual ceramic method [8]. Arana et al. (2012) studied the Li- substituted Mn-Zn ferrite structural and magnetic properties after different thermal treatments. Lithium of composition Zn0.6Mn0.4Fe2O4 and Li0.2Zn0.2Mn0.4Fe2.5O4 were prepared by the self- combustion sol-gel method. Incorporating Li to the crystalline lattice increased the saturation magnetization and promoted a decrease in the secondary phase’s segregation [9]. Rosaiah and Hussien (2013) studied the preparation of the ferrite by hydrothermal synthesis. XRD spectrum exhibited predominate (200) orientation peak at 2θ = 43.63 corresponding to cubic structure. Electric and dielectric properties were studied over a frequency range of 1Hz-1MHz [10]. Agami et. al. (2014), investigated the structural, IR, and magnetic studies of annealed Li-ferrite nanoparticles nano-particles of spinel Li-ferrite, Li0.5Fe2.5O4, were prepared by sol-gel auto combustion technique and annealed at different temperatures (Ta = 673, 873, and 1073 K)[11].The aim of this research is studding the physical and mechanical properties of synthesized nnoferrites doped by Y2O3. 2. Experimental Work 2.1. Sample Preparation The numbers of samples and the percentage of Y2O3 are listed in Table (1). Table 1, Shows the numbers of samples and Percentage of Y2O3 2.1. Preparation of Nano-Ferrite by Co- Precipitation 1. Hydrated cobalt nitrate is dissolved in 50/50 % distilled water – ethanol ratio with 0.5(Molarity) M. 2. Hydrated lithium nitrate is dissolved in 50/50 % distilled water – ethanol ratio with 0.5 M. 3. Hydrated iron nitrate is dissolved in 50/50 % distilled water – ethanol ratio with 0.5 M. 4. The cobalt solution is mixed with iron solution, where the ratio of cobalt solution to iron solution was selected according to a definite chemical stoichiometric ratio as (Fe: Co=2:1) by using magnetic stirrer. 5. The lithium solution is mixed with iron solution, where the ratio of lithium solution to iron solution was selected according to a definite chemical stoichiometric ratio as (Fe: Li =5:1) by using magnetic stirrer. 6. The two solutions are mixed by using magnetic stirrer. 7. 7. Addition of the resulting cobalt ferrite with different weight percentage (2, 5, 10, 15 and 20 wt. %) to lithium ferrite. 8. Addition of surfactant material (glucose). 9. Addition of ammonium hydroxide drops to the mixed solution until the gel bed was formed. 10. PH of the solution was measured, where the gel formation begins at PH 6.5. 11. Addition of citric acid that leads to hear notifying the combustion which helps in reducing the particle size of produced gel. 12. Filtrate the solution with filter papers to get out the gel. 2.2. Drying and Calcination The filtered gel was then dried at temperature 80°C for 6 hours in a programmed electrical oven. The gel was then crushed and calcined at temperature 800°C at heating rate 10°C/min for 1 hour. The powders were finally cooled by switching off the furnace to room temperature. 2.3. Powder Compaction Poly vinyl alcohol (PVA) with 2 wt. % was mixed with the powder for (30) min. Then, the powder was pressed unixally in Stave stainless steel at (374) MPa pressure to have a compacted specimen with diameter (10mm) and thickness (4 mm). No. Number of samples Percentage of Y2O3 1 3 0.5 2 3 1 3 3 2 4 3 4 5 3 6 Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 12 2.4. Sintering Process The sintering processes of the compact samples were carried out in air atmosphere. The sintering temperature used was 1200 °C for two hours, with a heating rate and cooling rate of 10°C/min as shown in the Figure (1).Then, the dimensions and masses of sintered samples were measured to determine apparent density , porosity and water absorption using Archimedes method while splitting tensile strength measured by Brazilian test and the micro hardness measured by Vickers test . 3. Results and Discussion Physical Properties of Doped Nano-Ferrite Apparent Density and Porosity Figure (2) presents the apparent density versus different weight percentages of Y2O3. It has been shown that the apparent density of prepared nano- ferrite samples is increased with increasing Y2O3 content. This may be due to the removal of micro pores in their microstructure during the sintering process. During the sintering, the time of sintering and the temperature are very important parameters to satisfy the diffusion of particles and then increasing mass flow rate through the pores which leads to increase the apparent density and decrease the porosity, as shown in Figure (2). Sintering at high temperature causes high diffusion rates and higher densification. Fig. 1. Single heating cycle of the applied sintering process. Fig. 2. Density for ferrites at different percentages of Y2O3. Figure (3) shows the effect of Y2O3 addition on the porosity of ferrite system sintered at 1200⁰C for two hours. As seen the porosity decreased rapidly with increasing the Y2O3 content which may be due to the filling of the pores, which gives higher densification as shown in the density results. Fig. 3. Apparent porosity for different percentages of Y2O3. Water Absorption Water absorption is shown in Figure (4) for different weight percentages of Y2O3. The water absorption decareases with increasing the precentage of Y2O3. It is well known that the water absorption is the physical property upon that dopends on the appearent porosity, where the water enters the open pore channel. Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 13 Fig. 4. Water absorption for different weight percentages of Y2O3. 4. Mechanical Properties Splitting Tensile Strength (Brazilian Test) Figure (5) shows the effect of Y2O3 percentages on the fracture strength of nano- ferrite which is sintered at 1200℃ for two hours. It is clear a bell shape formed from the relation between Y2O3 percentage and fracture strength of the nano-ferrite which increased with increasing the Y2O3 content having the highest value (51 MPa) at 1wt. % Y2O3 and then decreased. As shown in the figure that the addition of Y2O3, especially at 1wt. % has highly improved the splitting tensile strength of the ferrite system, its value is more than twice that of the ferrite system. The increasing in the splitting tensile strength of the doped ferrite is due to density improvement with less porosity which leads to increasing the particles bonding. After 1wt. % Y2O3, the fracture strength decreases with further addition of Y2O3, and this may be due to the presence of residual porosity in the ferrite system. Residual stresses in the samples are another factor that may have contributed to the reduction in splitting tensile strength [12]. There is a difference in the thermal expansion coefficient between ferrites and Y2O3, and this mismatch in the thermal expansion coefficient could produce residual stresses near ferrites-Y2O3 grain boundaries. And, that could also result in micro cracking which lowers the strength values [13]. Fig. 5. The splitting tensile strength of nano-ferrite at different percentages ofY2O3 sintered at 1200⁰C for 2 hrs. Vickers Micro Hardness The micro hardness of material is an important mechanical property because it relates how much the material will inelastic deformed when a surface load is applied. The indentation diameters of micro Vickers tester for sintered samples are very small and do not appear in Vickers tester instrument. The light optical microscope with a computer program was used to analyze the image and calculate the micro hardness. The Vickers micro hardness value of the ferrite system doped with different percentages of Y2O3 that sintered at 1200⁰ C for 2 hrs is shown in Figure (6). It is clear that the hardness of samples increased with increasing Y2O3 content until 1wt. % and then decreased while has the same behavior of splitting tensile strength. Because the hardness value are highly correlated with the relative density and porosity, so reducing the number of defects in a sample is a common way of decreasing its micro hardness[14]. The hardness has a maximum value at 1 wt.% Y2O3 which will result in a material being more resistance to the indentation at a given load, which will signify that the material will be able to plastically deform more so than the ferrite ceramic. Sometimes, the mechanical properties, such as hardness are decreased when the grain size is decreased in the nano range, as reported by Andrievski and Glezer [15]. Furthermore, in this work, Vickers micro hardness is decreased slightly after 1% Y2O3. Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 14 Fig. 6. Vickers micro hardness for the different percentages of Y2O3. 5. SEM of Doped Nano-Ferrites SEM imaging was conducting to observe the shape and morphology of samples. The SEM micrographs were taken from the fresh fracture surface of a ferrite body compacted and sintered at 1200⁰ C from the composition [(Li0.5Fe2.5O4)1- X(CoFe2O4)X]1-y(Y2O3)y obtained with the classical ceramic technology presented. These micrographs are shown in Figure (7) to Figure (11) . It is clear that the fracture surface is an intergranular fracture (equiaxal), and the microstructure displays an irregular (non- equiaxal) fine grain microstructure with average grain size that are slightly larger than the ferrite powders particle size. It is evident from the micrographs that the microstructure of the surface consists of detached, approximately closely-packed particles. Also, these images show the formation of micro agglomeration particles and some voids, where pores are located at the junctions of agglomerates. The black and dark regions correspond to the ferrites particles and pores respectively, while the lighter areas are for Y2O3 phase. Furthermore, it is clear that by increasing Y2O3, the porosity decreased and denser materials obtained. The crack propagation occurs near the pores in the microstructure, where the pores act as stress density resulting in easy crack propagation path. It is also clear that some of the grains have grown when the sintering at 1200 ℃ in the preferred orientation. The fracture nature of the prepared nano-ferrite from lithium ferrite-10% cobalt ferrite – Y2O3 seems to be brittle which is clear from the fracture samples after the indirect tensile test (Brazilian test). Fig. 7. SEM image of fracture surface for 0.5% Y2O3 additives. Fig. 8. SEM image of fracture surface for 1% Y2O3 additives. Fig. 9. SEM image of fracture surface for 2% Y2O3 additives. Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 15 Fig. 10. SEM image of fracture surface for 4% Y2O3 additives. Fig. 11. SEM image of fracture surface for 6% Y2O3 additives. 6. Conclusions To summarize the main ideas obtained, the following conclusions can be concluded from this work: 1- Mixed ferrites (lithium ferrites-cobalt ferrite) were successfully prepared by sol-gel technique. 2- SEM micrographs are established that the use of nanopowder produced by sol-gel technology leads to uniform and dense ferrite bodies, where the structure is compact with fewer amounts of pores. 3- Physical properties, such as density have incresed with Y2O3 content. 4- Porosity and water absorption decrease with the increasing content of Y2O3. 5- Fracture strength, micro hardness and the other properties are improved by the addition of Y2O3, especially at 1 wt. %. 7. Referances [1] J. Fontuberta , S.Rodrrguez , M.Pernet , G.Longworth and J.B. Good enough “ structured and magnetic characterization of the lithinated iron oxide Lix Fe3O4 “ J. Appl.Phys. , 59 (6) , pp(1918 – 1926 ) , 1986. [2] Qi Xiwei , Ji Zhou , Z. Yue , Z. Gui and L.Li , “ Permeability and microstructure of manganese modified lithium ferrite prepared by sol-gel auto- combustion method “J. Materials Science and Engineering , B99 , pp278 -281 , 2003 [3] S. Dey , A.Roy , D. Das and J.Ghose , “ Preparation and Characterization of nano- crystalline disorderd lithium ferrite by citrate precursor method “ J. of magnatism and magnatic materials , 270 , pp (224 – 229 ) , 2004 . [4] Li Langchao , J. Jiang and F. Xu , synthesis and ferromagnetic properties of noval Sm- subsituted Li – Ni ferrite – polyanaline nanocomposite “ ,J.of Materials letters , 61 pp ( 1091 – 1096 ) , 2007 [5] J.Jiang,L.Li and F Xu,” Preparation and characterization of microwave ferrite msterials’’,edited by Wihelm H. Von Aulock,Acadimic by Press New York and London.Vol.407,pp.(269-271),1985. [6] C. Wende and H. Langbein, “Synthesis and characterization of compounds Lix Mn1- xFe2-2xO4 with spinel structure in the quasiternary system LiO0.5-MnOx-FeOx”, Cryst. Res. Technd, Vol. 41, No.1, PP (16- 18) , 2006. [7] C. Altavilla, C. Leone, D. Sannino, M. Sarno and P. Ciambelli, “Synthesis of monodispersed MFe2O4 (M=Fe, Co, Ni) ferrite nanoparticles: effect of reaction temperature on particle size”,J.of Nanoteach, Vol. 1, PP (143-146), 2009. [8] E. De Fazio , P. G. Bercoff and S. E. Jacobo , “Electromagnetic properties of manganese- zinc ferrite with lithium substitution”, J. of Magnetism and Magnetic Materials, Vol. 323, PP (2813–2817), 2011. [9] M. Arana,P.G. Bercoff and S. E. Jacobo, “Li- substituted Mn-Zn ferrite: structural and Magnetic Properties After Different Thermal Treatments”, Pro. Materials Science,Vol.1, PP(620-627), 2012. [10] P. Rosaiah and O. M. Hussien, “Synthesis, electrical and dielectric properties of lithium iron oxide”, Adv. Mat. Lett., Vol. 4, No. 4, PP (288-289), 2013. Fadhil A. Chyad Al-Khwarizmi Engineering Journal, Vol. 12, No. 2, P.P. 10- 17(2016) 16 [11] W. R. Agami, M. A. Ashmawy and A. A. Sattar, “Structural, IR, and magnetic studies of annealed Li-ferrite nano-particles”, J. of Materials Engineering and Performance, Vol.23, No.2, PP (604-610), 2014. [12] E. Jung, J. Kim, S. Jung and S. Choi, “Synthesis powders by carbothermal and Borothermal reduction”, J. of Alloys and Compound, Vol. 538, PP (164-168), 2012. [13] S. Zhu, W. G. Fahren, G. E. Hilmas, S. Zhang, E. Yadlowsky and M. Ketiz, “Microwave sintering Zro2-Buc particulate ceramic composites”, Composite part A:Applied Science and Manufacturing, Vol. 39, PP (449-453), 2008. [14] L. Hankla, “Mechanical properties of particulate-reinforced boron carbide composite”, M. SC. Thesis, University of South Florida, USA, 2008. [15] R. Andrievski and A. 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