• Korean Journal of Materials Research
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• v.11 no.10
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• pp.846-850
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• 2001

In the present study, nano-size powders of ternary ferrites, $Ni_{0.5}Zn_{0.5}Fe_2O_4$, as the potential catalysts of $CO_2$decomposition, were prepared by the wet processing of hydrothermal synthesis and coprecipitation method, and the catalyzing effects of impregnation of the noble metals, Pt and Pd, onto $Ni_{0.5}Zn_{0.5}Fe_2O_4$for the $CO_2$decomposition were investigated. XRD results of the synthesized ferrites showed a typical spinel structure of ferrite and the particle size was very small as about 6~10 nm. BET surface area of the ternary ferrites was not affected by the impregnation of Pt and Pd. The reactivity of the $CO_2$decomposition to carbon was improved by the impregnation of the noble metals of Pd and Pt. The effect of Pd-impregnation on the $CO_2$decomposition rate was higher than Pt-impregnation.

• Journal of Magnetics
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• v.18 no.1
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• pp.21-25
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• 2013

Nickel substituted manganese ferrites, $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$), were fabricated by sol-gel method. The effects of sintering and substitution on their crystallographic and magnetic properties were studied. X-ray diffractometry of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered above 523 K indicated a spinel structure; particles increased in size with hotter sintering. The M$\ddot{o}$ssbauer spectrum of this ferrite sintered at 523 K could be fitted as a single quadrupole doublet, indicative of a superparamagnetic phase. Sintering at 573 K led to spectrum fitted as the superposition of two Zeeman sextets and a single quadrupole doublet, indicating both ferrimagnetic and paramagnetic phase. Sintering at 673 K and at 773 K led to spectra fitted as two Zeeman sextets due to a ferrimagnetic phase. The saturation magnetization and the coercivity of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered at 773 K were 53.05 emu/g and 142.08 Oe. In $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$) ferrites, sintering of any composition at 773 K led to a single spinel structure. Increased Ni substitution decreased the ferrites' lattice constants and increased their particle sizes. The M$\ddot{o}$ssbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and the octahedral sites of the $Fe^{3+}$ ions. The variations of saturation magnetization and coercivity with changing Ni content could be explained using the changes of particle size.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.31-36
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• 2003

In this study, nano-sized NiCuZn-ferrites for the multi-layered chip inductor application were prepared by a coprecipitation method and its electromagnetic properties were analyzed. Also, the property of low temperature sintering were studied with the initial heat treatment of powder.$(Ni_{0.4-x}Cu_xZn_{0.60})_{1+w}(Fe_2O_4)_{1-w}$ (x=0.2, w=0.03) were calcined at $300^{circ}C~750^{circ}C.$ The sintered NiCuZn-ferrites at $900^{\circ}C$ showed good apparent density $4.90g/cm^3,$ and magnetic properties of initial permeability 164 and quality factor 72. As the calcination temperature increase, the grain size of NiCuZn-ferrite increased with irregular grain distribution and its magnetic properties were deteriorated.

• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.43-47
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• 2008

[ $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ ] nano-glass has been prepared by sol-gel method. The mean particle size was 60.3 nm with narrow size distribution. The nano-galss has been used as a sintering aid for the densification of the NiZnCu ferrites. The ferrite was sintered with nano-glass sintering aids at $840{\sim}900^{\circ}C$, 2 h and the initial permeability, quality factor, density, and saturation magnetization were also measured. The initial permeability of 0.5 wt% nano-glass added toroidal sample for NiZnCu ferrites sintered at $900^{\circ}C$ was 193.3 at 1 MHz. The initial permeability and saturation magnetization were increased with increasing annealing temperature. As a result, $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ nano-glass systems were found to be useful as sintering aids for multilayer chip inductors.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1119-1123
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• 2002

Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.

• Journal of Magnetics
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• v.21 no.1
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• pp.40-45
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• 2016

Nickel substituted nano-sized ferrite powders, $Co_{1-x}Ni_xFe_2O_4$, $Mn_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ($0.0{\leq}x{\leq}0.2$), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in $Co_{1-x}Ni_xFe_2O_4$ ferrite but increased for the $Mn_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites. For the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.2$) ferrite powders, the $M{\ddot{o}}ssbauer$ spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of $Mn_{0.8}Zn_{0.1}Ni_{0.1}Fe_2O_4$ consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explain the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites but increased in the $Mn_{1-x}Ni_xFe_2O_4$ ferrite with nickel substitution. The coercivity decreased in the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites but increased in the $Mn_{1-x}Ni_xFe_2O_4$ ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.93.1-93
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• 2002

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.93.2-93
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• 2002

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.114.2-114
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.22.1-22.1
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• 2008