• Journal of the Korean Ceramic Society
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• v.18 no.2
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• pp.83-90
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• 1981

In this study, the effect of additions on magnetic properties in the system of [$Ni_{0.32}Zn_{0.68}$] 1-x Mx $Fe_2O_4$ have been investigated. The additions, Co or Mg or Cu, was added in turn in place of M, and its composition was varied from 0.1 mo1% to 0.5 mo1%. The materials were blended by hot petroleum drying method, and sintered with the rate of 30$0^{\circ}C$/h in the air. The sintering temperatures were varied from 110$0^{\circ}C$ to 130$0^{\circ}C$, with the intervals of 5$0^{\circ}C$, and matured for 3hrs. The results are: 1) The permeability decreased when the addition, MgO or CoO, was added, and it increased when CuO was added. 2) Resistivity had the lowest Value when CuO was added.

• Journal of the Korean Institute of Navigation
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• v.22 no.4
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• pp.69-75
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• 1998

The super wideband electromagnetic wave absorber in RF-A-PF type has been proposed, which can be used for an anechoic chamber, wall material to prevent TV ghost, etc, In this paper, $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$ Ferrite Powder has been fabricated. Using this, then, [$Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and its characteristics has been analyzed. As a result, it has been shown that the $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composit with the quantity $_x$ of $Ni_x$ between 0.5 and 0.6 is suitable for the RF-layer in the case of which the grain size is sub-micrometer order.

• Analytical Science and Technology
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• v.5 no.4
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• pp.401-408
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• 1992

The ion-selectrodes based on calcium ferrite were prepared by mixing calcium oxide with ferric oxide on molar ratio of 0.6:1.4, 0.8:1.2, 1.0:1.0, respectively. The specimens were sintered at $1400^{\circ}C$ for 2hrs in $O_2$ and for 20min in $H_2$ atmosphere. The selectrode sintered in hydrogen atmosphere showed better responded potential and wider range of responded concentration than selectrode sintered in oxygen atmosphere. The ion-selectrodes base on calcium ferrite(0.6:1.4 molar ratio.) showed the highest potential to bivalent cations such as $Ca^{2+}$, $Ba^{2+}$, $Mg^{2+}$, $Zn^{2+}$ and halogen anions such as $I^-$, $Br^-$ in the range of $10^{-1}{\sim}10^{-7}M$. It showed good agreement with theoretical nernstian values.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2004.12a
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• pp.12-16
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• 2004

최근 트랜스 및 코일에 쓰이는 소프트 페라이트 코아는 많은 전자$\cdot$통신소자에 응용이 되고 있다. 특히, 전기적 특성 면에서 다른 금속 재료에 비하여 극히 높은 비저항을 갖으며, 주파수 영역 역시 수백 MHz를 넘는 곳에 사용이 된다. 현재 사용되는 용도는 TV 및 퍼스널컴퓨터의 디스플레이에 사용되는 편향요크용, 후라이백, 트랜스용 코아 등에 사용되며 소형 경량화가 요구되고 있다. 따라서 편향 요크용 페라이트 코아에는 고주파수 영역에 있어서 낮은 코아로스 재료가 요구되고 있는 실정이다. 본 연구에서는 Mg-Zn 페라이트에 있어서 화학조성 및 프로세스가 미세구조에 미치는 영향에 대한 구체적인 연구를 검토하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.299-302
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• 2004

최근 트랜스 및 코일에 쓰이는 소프트 페라이트 코아는 많은 전자ㆍ통신소자에 응용이 되고 있다. 특히, 전기적 특성면에서 다른 금속 재료에 비하여 극히 높은 비저항을 갖으며, 주파수 영역 역시 수백 MHz를 넘는 곳에 사용이 된다. 현재 사용되는 용도는 TV 및 퍼스널컴퓨터의 디스플레이에 사용되는 편향요크용, 후라이백, 트랜스용 코아 등에 사용되며 소형 경량화가 요구되고 있다. 따라서 편향 요크용 페라이트 코아에는 고주파수 영역에 있어서 낮은 코아로스 재료가 요구되고 있는 실정이다. 본 연구에서는 Mg-Zn 페라이트에 있어서 화학조성 및 프로세스가 미세구조에 미치는 영향에 대한 구체적인 연구를 검토하였다.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.223-226
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• 2000

The oxygen deficient ferrites $(Ni_x,\; Zn_{1-x})Fe_2O_{4-{\delta}}$ can decompose $CO_2$ as C and $O_2$ at a low temperature of about $300^{\circ}C$. Ultra powders of $(Ni_x,\; Zn_{1-x})Fe_2O_4$ for the $CO_2$ decomposition were prepared by the hydrothermal methods. The XRD result of synthesized ferries showed the spinel structure of ferrites and ICP-AES and EDS quantitative analyses showed the composition similar with the starting molar ratios of the mixed solution prior to reaction. The BET surface area of the synthesized(Ni, Zn)-ferrites was above $110\textrm{m}^2/g$ and its particle size was very as small as about 5~10 nm. The $CO_2$ decomposition efficiency of the oxygen deficient ferrites($(Ni_x,\;Zn_{1-x})Fe_2O_{4-{\delta}}$) was almost independent with composition and the $CO_2$ decomposition efficiency of ternary (Ni, Zn)-ferrites was better than of binary Ni-ferrites.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.393-398
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• 2005

The crystal structure and magnetic properties of the $Mg_{1-x}Zn_xFeAlO_4\;(0{\leq}x\leq1.0)$ have been investigated by means of x-ray diffractometry and $M\ddot{o}ssbauer$ spectroscopy. The samples$(0{\leq}x\leq1.0)$ have been prepared by the ceramic sintering method. The x-ray diffraction pattern shows that the crystal structure of the samples is a cubic spinel type. The lattice constant has been found by extrapolation using the Nelson-Riley function and it increases slightly from $8.3496\AA\;to\;8.4128\AA$ with Zn concentration. The $M\ddot{o}ssbauer$ spectra for x<0.4 show a superposition of two sextets ana a paramagnetic doublet at room temperature. The superparamagnetic doublet for x<0.4 seems to be due to Al ion in tetrahedral site by the superparamagnetic clustering effect.

• Applied Chemistry for Engineering
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• v.2 no.3
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• pp.279-288
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• 1991

Mg- and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituent single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, TG/DTA, ESCA, TEM, and TPD methods were employed. The effects of Cr-substitution were intensively studied by the experimental methods mentioned above. Chromium which showed a preferential tendency to diffuse to the surface acted as a structural promoter by increasing surface area and stability of catalyst structure. In the dehydrogenation of ethylbenzene, catalytic activity, and the effects of Cr-substitution were investigated. Oxygen mobility was decreased with the amount of Cr-substitution in $MgCr_xFe_{2-x}O_4$, which resulted in the increase of selectivity to styrene and the suppression of total oxidation.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.722-729
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• 1992

Mg-and Zn-ferrites having spinel structure, a kind of complex oxides showing the advantageous properties of constituently single metal oxides, were selected to find a relationship between their catalytic activities in the dehydrogenation of ethylbenzene to styrene and the catalytic properties. For the structural and physical analyses of ferrites, XRD, BET, DTA, XPS, TEM and TPD methods were employed. Potassium added to the catalyst played a role of bifunctional promoter which brought the electronic effect as well as the structural one for the increment of particle dispersion. K-addition decreased acid strength of the catalyst by neutralization and increased its acidity. In the dehydrogenation of ethylbenzene, K-addition let the selectivity to styrene be constant throughout the reaction by the proper acid strength of the ferrite for the reaction, which could be obtained from the neutralization of strong acid sites by potassium.