Raba’ah Syahidah Azis

Morphology and dielectric properties of single sample Ni 0.5 Zn 0.5 Fe 2 O 4 nanoparticles prepared via mechanical alloying

Nickel-zinc ferrite nanoparticles are important soft magnetic materials for high and low frequency device application and good dielectric materials. Nickel-zinc ferrite nanoparticles with composition Ni0.5Zn0.5Fe2O4 were prepared using mechanical alloying to analyze the effect of sintering temperature on microstructure evolution of a single sample with dielectric properties. The single sample with nanosized pellet was sintered from 600 °C to 1200 °C and analyzed by X-ray diffraction (XRD) to investigate the phases of the powders and by field emission scanning electron microscopy (FESEM) for the morphology and microstructure analyses. Dielectric properties such as dielectric constant (ɛ′) and dielectric loss (ɛ″) were studied as functions of frequency and temperature for Ni0.5Zn0.5Fe2O4. The dielectric properties of the sample were measured using HP 4192A LF impedance analyzer in the low frequency range from 40 Hz to 1 MHz and at temperature ranging from 30 °C to 250 °C. The results showed that single phase Ni0.5Zn0.5Fe2O4 cannot be formed by milling alone and therefore requires sintering. The crystallization of the ferrite sample increased with increasing sintering temperature, while the porosity decreased and the density and average grain size increased. Evolution of the microstructure resulted in three activation energies of grain growth, where above 850 °C there was a rapid grain growth in the microstructure. Dielectric constant and loss factor decreased with the increase in frequency. The optimum sintering temperature of Ni0.5Zn0.5Fe2O4 was found to be 900 °C which had high dielectric constant and low dielectric loss.

Magnetic and Microwave Properties of Polycrystalline Gadolinium Iron Garnet

The microwave loss in nanosized GdIG particles synthesized using mechanical alloying technique was investigated. There were very few of research on the microwave properties of nanosized particle GdIG and there is no attempt investigating on the material at C-band frequency range and its correlation with the microstructure. Gadolinium (III) iron oxide and iron (III) oxide, α-Fe2O3 were used as the starting materials. The mixed powder was then milled in a high-energy ball mixer/mill SPEX8000D for 3 hours. The samples were sintered at temperature 1200°C for 10 hours in an ambient air environment. The phase formation of the sintered samples was analyzed using a Philips X’Pert Diffractometer with Cu-Kα radiation. Complex permeability constitutes of real permeability and magnetic loss factor were measured using an Agilent HP4291A Impedance Material Analyzer in the frequency range from 10 MHz to 1 GHz. A PNA-N5227 Vector Network Analyzer (VNA) was used to obtain the information on ferromagnetic linewidth broadening, ΔH that represents the microwave loss in the samples in in frequency range of 4 to 8 GHz (C-band). The ΔH value was calculated from the transmission (S21) data acquired from VNA. The single phase GdIG showed low initial permeability and low magnetic loss when applied with low-frequency range energy. From these data, it is validated that GdIG is a suitable material for microwave devices for the high-frequency range.

Effect of Variation Sintering Temperature on Magnetic Permeability and Grain Sizes of Y3Fe5O12 via Mechanical Alloying Technique

This work will focus on the preparation of yttrium iron garnet (Y3Fe5O12, YIG) via mechanical alloying technique derive by steel waste product. The Fe2O3 powder derived from the steel waste purified by using magnetic and non-magnetic particles (MNM) and Curie temperature separation (CTS) technique. The purified powder was then oxidized in air at 500 °C for 9 hours in air. The Fe2O3 was mixed with Y2O3 using high energy ball milling for 9 hours. The mixed powder obtained was pressed and sintered at different temperature 500/600/700/800/900/1000/1100 °C. X-ray diffraction (XRD) shows the YIG is completely form at 1100 °C. The field emission scanning electron microscopy (FESEM) images shows the grain size increases as increase the sintering temperatures. The frequency dependence on the complex permeability, µ’ and magnetic loss, µ’’ in the frequency range 10 MHz to 1 GHz were measured in this study. The results showed that the highest μ΄ is 5.890 obtained from 1100 °C.

Magnetic Properties and Microstructures of Cobalt Substituted Barium Hexaferrites Derived from Steel Waste Product via Mechanical Alloying Technique

The mechanical alloying technique was used to prepare barium hexaferrite (BaM) with 3, 5, 10 and 20 wt% cobalt oxide (Co3O4). In this work, steel waste flakes were cold-rolling steel mill for several hours to form a fine powder. The steel waste powder was purified by using magnetic separation to isolate the magnetic and non magnetic particles. The method was continued for Curie temperature separation technique to separate the magnetic ions by varied Curie temperature of the magnetic powder. The purified powder was then oxidize at 500 °C at 6 °C/mins to form hematite, Fe2O3. The steel waste-derived hematite was used as the raw material in preparing BaM ferrites. The BaCO3, Fe2O3 and different percentages of Co3O4 (Co) were mixed and milled for several hours by using mechanical alloying. The powder were pelletised in 11 × 1 mm (diameter × height) and the sintered at 1200 °C for 10 hours. The addition of Co2+/3+ ions to the BaM shows a varying in the magnetic properties of BaM. By increasing the Co doping, the remanence Mr was reduced from 17.6 emu/g to 6.2 emu/g. The coercivity Hc results varying magnitude from 102 Oe to 1079 Oe. The Mr and Hc of undoped BaM is obtain at 14.6 emu/g and 860 Oe, respectively. The grain size of BaM also increases with Co doping. The densities of the compounds are decreasing with increasing Co doping with a maximum value of 4.2 g/cm3.

Influence of sintering temperature on the structural, electrical and microwave properties of yttrium iron garnet (YIG)

This study investigates the structural, electrical and microwave properties of yttrium iron garnet (YIG) which focuses on the parallel evolving relationship with their dependence on the sintering temperature. The iron oxide obtained from the steel waste product (mill scale) was used to synthesize YIG. The raw mill scale underwent the milling and Curie temperature separation technique to produce high purity iron oxide powder which is the main raw material in preparing and fabricating YIG through high energy ball milling (HEBM) process. Microstructural features such as amorphous phase, grain boundary, secondary phase and intergranular pores contribute significantly to the additional magnetic anisotropy and demagnetizing fields, affecting the electric and microwave properties accordingly. The increment in electrical resistivity and decrement in linewidth while the microstructure was evolving is believed to be a strong indicator of improved phase purity and compositional stoichiometry.

Effects of Calcination Temperature on Microstructure and Superconducting Properties of Y123 Ceramic Prepared Using Thermal Treatment Method

Thermal treatment method was employed to produce YBa2Cu3Ox superconductor ceramic. The effects of calcination temperature at 850 °C, set A, and 910 °C, set B, for 24 h followed by sintering at 930, 950 and 980 °C, were investigate using X-ray diffraction (XRD), scanning electron microscope (SEM) and four point probe measurement. The orthorhombic structure appears after calcination at 850 and 910 °C beside small amount of impurity phase such as Y2BaCuO5 (Y211). The samples exhibited metallic behaviour and the critical temperature, TC(R=0), increases with increasing sintering temperature. The TC(R=0) of samples calcined at 910 °C is higher than that of sample calcined at 850 °C. The highest TC(R=0), 87 K, was found for sample sintered at 980 °C of set B. An increase in grain size and homogeneity was observed as the sintering temperature increases. The set B sample sintered at 980 °C showed compact grains, which could result in the highest Tc (R=0).

Microstructural and Nonlinear Properties of Zn-V-Mn-Nb-O Varistor Ceramics with Gd 2 O 3 Substitution for Low Voltage Application

The effect of Gd2O3 substitution on the microstructural and electrical properties of Zn-V-Mn-Nb-O varistor ceramics sintered at 900°C was investigated. XRD, SEM, and EDAX results show that the GdMnO3 and GdVO4 phases formed at the grain boundaries and triple point junctions. Gd2O3 substitution inhibited the grain growth from 3.85 to 3.06 μm and increased the sintered ceramics density from 5.12 to 5.19 g/cm3.The samples containing the amount of 0.03 mol% Gd2O3 exhibit an optimum nonlinear coefficient α value which is 9.91, highest breakdown electrical field which is 88.48 V/mm and lowest leakage current density which is 0.11 mA/cm2 in low voltage application.

Preparation and Characterization of Sr1−xNdxFe12O19 Derived from Steel-Waste Product via Mechanical Alloying

Steel waste product had been used as the main source of raw material in the preparation of permanent magnets ferrites. Steel waste product is an impure material that contains the iron oxide and impurities. The steel waste product is a form of flakes is grinding for several hours to form a fine powder. The iron oxide powder is separated from magnetic and non-magnetic particle using magnetic particle separation. The magnetic particle was again been purified by using the Curie temperature separation technique. The magnetic powder was carried out from the purification and oxidize at 500 °C for 6 hours at 2 °C/ mins to form the hematite, Fe2O3, used as a raw powder to prepare SrFe12O19. Microstructure of Nd-doped strontium ferrites, Sr1-xNdxFe12O19, with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, were prepared through a mechanical alloying technique. Several characterizations have been done, such as X-ray Diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The magnetic properties of coercivity (Hc) and the energy product BHmax of samples are carried out. The magnetic properties of samples were investigated with an expectation of enhancing the magnetic properties by substitutions of Nd3+ ions on Fe3+ ion basis sites. The saturation magnetization Ms revealed magnetic behavior with respect to Nd3+ doping concentration, showing a decrease. The coercivity Hc increased with increasing Nd3+ doping concentration.