Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and...Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and oxygen）, milling time （from 0 to 30 h） and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600℃ for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated.展开更多
This study involves an investigation to ascertain the effect of sintering temperature on the particle size distribution of Co0.5 Zn0.5 Fe2O4 nano-particle. The effect of the sintering temperature towards diffusion of ...This study involves an investigation to ascertain the effect of sintering temperature on the particle size distribution of Co0.5 Zn0.5 Fe2O4 nano-particle. The effect of the sintering temperature towards diffusion of CoO and ZnO into the tetrahedral and octahedral sites was also reported. In this study, CoO, ZnO and Fe2O3 powders were mechanically alloyed to synthesize fine powders of Co0.5 Zn0.5 Fe2O4 nano-particles. The synthesized powder was then sintered at various temperatures which were employed to study the effect of sintering temperature on the materials. Further analysis was done using XRD to investigate the phases of the powder and the crystallite size using Scherrer equation, SEM and EDX for the morphology and elemental composition of samples. The XRD spectra indicated that Both ZnO and CoO powder reacted well during sintering, however, ZnO was first to diffuse into its crystallographic sites before CoO. While the particle size distribution increases as the sintering temperature increases. Amongst other findings, it was confirmed that sintering temperature affects the particle size distribution of samples and samples begin to agglomerate at temperature above 700°C.展开更多
Nanocrystalline CoZn-ferrite was fabricated by a high-energy milling method by mixing Fe3O4+CoO+ZnO. The structural properties of the milled powder at different milling times were analysed so to ascertain the diffusio...Nanocrystalline CoZn-ferrite was fabricated by a high-energy milling method by mixing Fe3O4+CoO+ZnO. The structural properties of the milled powder at different milling times were analysed so to ascertain the diffusion of CoO and ZnO into the tetrahedral and octahedral sites using mechanical alloying method. The effect of mechanical alloying towards particle size was also investigated. The XRD spectra indicated the precursors reacted during milling with the diffusion of ZnO and followed by CoO into their respective crystallographic sites. SEM micrographs showed the agglomeration of powders due to high energy milling and TEM images confirmed that the particles of the materials were of nanosize dimension. In addition, the results show that the grain possesses a single-phase CoZn-ferrite structure in a typical size of ~16–30 nm. The experiment reveals that nanosize CoZn-ferrite can be obtained after the powder is milled for about 8 hours at room temperature. The mechanism and efficiency of the synthesis of the technique are also discussed in this paper.展开更多
ZrC nanoparticles in the matrix of Fe were produced by the mechanically activated self-propagating hightemperature method using ZrO2/C/Mg/Fe powder mixtures. The effects of milling time, Fe content, and combustion tem...ZrC nanoparticles in the matrix of Fe were produced by the mechanically activated self-propagating hightemperature method using ZrO2/C/Mg/Fe powder mixtures. The effects of milling time, Fe content, and combustion temperature as well as the formation route for synthesizing ZrC powder particles were studied. The samples were characterized by XRD, SEM, TEM, and DTA. The XRD results revealed that, after 18 h of mechanical activation, ZrO2/ZC/Mg/Fe reacted with the self-propagating combustion（SHS） mode at 870 °C producing the ZrC–Fe nanocomposite. It was also found that both mechanical activation and Fe content played key roles in the ZrC synthesis temperature. With a Fe content of（5–40） wt%, the SHS reaction proceeded favorably and both the ZrC formation temperature and the adiabatic temperature（Tad） decreased. The Mg O content was removed from the final products using a leaching test process by dissolving in hydrochloric and acetic acids.展开更多
A series of polycrystalline M-type hexagonal ferrites with the formula BaFe12-2xZnx NbxO19 (x = 0.2, 0.4, 0.6, 0.8 mol%) have been synthesized by the sol-gel method. The composition and microstructure govern the magne...A series of polycrystalline M-type hexagonal ferrites with the formula BaFe12-2xZnx NbxO19 (x = 0.2, 0.4, 0.6, 0.8 mol%) have been synthesized by the sol-gel method. The composition and microstructure govern the magnetic properties of ferrites. The XRD analysis shows the formation of pure magneto plumbite phase without any other impurity phases. The Zn-Nb substitutions in barium hexaferrite have been confirmed through magnetic measurements. The results show that the magnetic properties are closely related to the distributions of Zn-Nb ions on the five crystallographic sites. The saturation magnetization and coercivity increase with increasing Zn-Nb concentration.展开更多
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 Ni_(0.5)Zn_(0.5)Fe...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 Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)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℃to 1200℃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(e″)and dielectric loss(e′)were studied as functions of frequency and temperature for Ni_(0.5)Zn_(0.5)Fe_(2)O_(4).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℃to 250℃.The results showed that single phase Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)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℃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 Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)was found to be 900℃which had high dielectric constant and low dielectric loss.展开更多
The desirable characteristics of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54)include high dielectric constant,low loss tangent,and high quality factor developed a new field for electronic applications.The microwave dielectric prop...The desirable characteristics of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54)include high dielectric constant,low loss tangent,and high quality factor developed a new field for electronic applications.The microwave dielectric properties of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54),with x?0:15 ceramics at different sintering temperatures(600–1300C)were investigated.The phenomenon of polarization produced by the applied electric field was studied.The dielectric properties with respect to frequency from 1MHz to 1.5 GHz were measured using Impedance Analyzer,and the results were compared and analyzed.The highest dielectric permittivity and lowest loss factor were defined among the samples.The complex dielectric modulus was evaluated from the measured parameters of dielectric measurement in the same frequency range,and used to differentiate the contribution of grain and grain boundary.展开更多
基金Project supported by the University Putra Malaysia Graduate Research Fellowship Section
文摘Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and oxygen）, milling time （from 0 to 30 h） and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600℃ for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated.
文摘This study involves an investigation to ascertain the effect of sintering temperature on the particle size distribution of Co0.5 Zn0.5 Fe2O4 nano-particle. The effect of the sintering temperature towards diffusion of CoO and ZnO into the tetrahedral and octahedral sites was also reported. In this study, CoO, ZnO and Fe2O3 powders were mechanically alloyed to synthesize fine powders of Co0.5 Zn0.5 Fe2O4 nano-particles. The synthesized powder was then sintered at various temperatures which were employed to study the effect of sintering temperature on the materials. Further analysis was done using XRD to investigate the phases of the powder and the crystallite size using Scherrer equation, SEM and EDX for the morphology and elemental composition of samples. The XRD spectra indicated that Both ZnO and CoO powder reacted well during sintering, however, ZnO was first to diffuse into its crystallographic sites before CoO. While the particle size distribution increases as the sintering temperature increases. Amongst other findings, it was confirmed that sintering temperature affects the particle size distribution of samples and samples begin to agglomerate at temperature above 700°C.
文摘Nanocrystalline CoZn-ferrite was fabricated by a high-energy milling method by mixing Fe3O4+CoO+ZnO. The structural properties of the milled powder at different milling times were analysed so to ascertain the diffusion of CoO and ZnO into the tetrahedral and octahedral sites using mechanical alloying method. The effect of mechanical alloying towards particle size was also investigated. The XRD spectra indicated the precursors reacted during milling with the diffusion of ZnO and followed by CoO into their respective crystallographic sites. SEM micrographs showed the agglomeration of powders due to high energy milling and TEM images confirmed that the particles of the materials were of nanosize dimension. In addition, the results show that the grain possesses a single-phase CoZn-ferrite structure in a typical size of ~16–30 nm. The experiment reveals that nanosize CoZn-ferrite can be obtained after the powder is milled for about 8 hours at room temperature. The mechanism and efficiency of the synthesis of the technique are also discussed in this paper.
文摘ZrC nanoparticles in the matrix of Fe were produced by the mechanically activated self-propagating hightemperature method using ZrO2/C/Mg/Fe powder mixtures. The effects of milling time, Fe content, and combustion temperature as well as the formation route for synthesizing ZrC powder particles were studied. The samples were characterized by XRD, SEM, TEM, and DTA. The XRD results revealed that, after 18 h of mechanical activation, ZrO2/ZC/Mg/Fe reacted with the self-propagating combustion（SHS） mode at 870 °C producing the ZrC–Fe nanocomposite. It was also found that both mechanical activation and Fe content played key roles in the ZrC synthesis temperature. With a Fe content of（5–40） wt%, the SHS reaction proceeded favorably and both the ZrC formation temperature and the adiabatic temperature（Tad） decreased. The Mg O content was removed from the final products using a leaching test process by dissolving in hydrochloric and acetic acids.
文摘A series of polycrystalline M-type hexagonal ferrites with the formula BaFe12-2xZnx NbxO19 (x = 0.2, 0.4, 0.6, 0.8 mol%) have been synthesized by the sol-gel method. The composition and microstructure govern the magnetic properties of ferrites. The XRD analysis shows the formation of pure magneto plumbite phase without any other impurity phases. The Zn-Nb substitutions in barium hexaferrite have been confirmed through magnetic measurements. The results show that the magnetic properties are closely related to the distributions of Zn-Nb ions on the five crystallographic sites. The saturation magnetization and coercivity increase with increasing Zn-Nb concentration.
基金The authors acknowledge the Fundamental Research Grant Scheme(FRGS)Project No.01-04-10-862 FR,Graduate Research Fellowship given to the graduate student(Rafidah Hassan)and the Physics Department,Faculty of Science,UPM.
文摘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 Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)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℃to 1200℃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(e″)and dielectric loss(e′)were studied as functions of frequency and temperature for Ni_(0.5)Zn_(0.5)Fe_(2)O_(4).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℃to 250℃.The results showed that single phase Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)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℃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 Ni_(0.5)Zn_(0.5)Fe_(2)O_(4)was found to be 900℃which had high dielectric constant and low dielectric loss.
基金This research was financially supported from the Research University Grant Scheme(RUGS)Project No.:05-02-12-2180RUUniversiti Putra Malaysia(UPM).The authors also acknowledged the Department of Physics,Faculty of Science,UPM and Institute of Advanced Technology(ITMA),UPM.
文摘The desirable characteristics of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54)include high dielectric constant,low loss tangent,and high quality factor developed a new field for electronic applications.The microwave dielectric properties of Ba_(6-3x)Nd_(8+2x)Ti_(18)O_(54),with x?0:15 ceramics at different sintering temperatures(600–1300C)were investigated.The phenomenon of polarization produced by the applied electric field was studied.The dielectric properties with respect to frequency from 1MHz to 1.5 GHz were measured using Impedance Analyzer,and the results were compared and analyzed.The highest dielectric permittivity and lowest loss factor were defined among the samples.The complex dielectric modulus was evaluated from the measured parameters of dielectric measurement in the same frequency range,and used to differentiate the contribution of grain and grain boundary.
