• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.42-48
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• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Proceedings of the Korean Magnestics Society Conference
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• 2006.06a
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• pp.42-43
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• 2006

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.203.1-203.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2011.12a
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• pp.74-74
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• 2011

• Proceedings of the Korean Magnestics Society Conference
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• 2005.12a
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• pp.140-140
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• 2005

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.16-16
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• 2002

The presently commercialized lithium-ion batteries use layer structured LiCoO₂ cathodes. Because of the high cost and toxicity of cobalt, an intensive search for new cathode materials has been underway in recent years. Recently, a concept of a one-to-one solid state mixture of LiNO₂ and LiMnO₂, i.e., Li[Ni/sub 0.5/Mn/sub 0.5/]O₂, was adopted by Ohzuku and Makimura to overcome the disadvantage of LiNiO₂ and LiMnO₂. Li[Ni/sub 0.5/Mn/sub 0.5/]O₂ has the -NaFeO₂ structure, which is characteristic of the layered LiCoO₂ and LiNiO₂ structures and shows excellent cycleability with no indication of spinel formation during electrochemical cycling. Layered Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials with high homogeneity and crystallinity were synthesized using a mechanical alloying method. The Li[Ni/sub 0.475/Co/sub 0.05/Mn/sub 0.475/]O₂ electrode delivers a high discharge capacity of 187 mAh/g between 2.8 and 4.6 V at a high current density of 0.3 mA/㎠(30 mA/g) with excellent cycleability. The charge/discharge and differential capacity vs. voltage studies of the Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials showed only one redox peak up to 50 cycles, which indicates that structural phase transitions are not occurred during electrochemical cycling. The magnitude of the diffusion coefficients of lithium ions for Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂(x = 0.5 and 0.475) are around 10/sup -9/ ㎠/s measured by the galvanostatic intermittent titration technique (GITT).

• Journal of Surface Science and Engineering
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• v.34 no.5
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• pp.494-498
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• 2001

Ferromagnets(FM)-Al-$O_{x}$ -Ferromagnets (FM) tunneling junctions were evaluated by changing the fabricating conditions of an Al-X$/_{x}$ layer. The junction composed of a thicker Al-$O_{x}$ shows the low resistance and the stable MR ratio about 16% in a wide range of oxidation time. For the junctions with the thinner Al-$O_{x}$ , they showed a fast increase of the barrier width as an increase of an oxidation time and exhibited a strong bias dependence. As oxidation time increased, the coercivity ($H_{c}$ ) of bottom Co layer increased gradually due to the local oxidation of Co bottom layer at a interface. However, the small formation of Co oxide did not largely influence on the deterioration of MR ratio.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.985-991
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• 1999

Corrosion behaviors of Incoloy 800H, KSA(Kaeri Superalloy)-6, Inconel 600 and Hastelloy C-276 in molten salts were investigated in the temperature range of 650 ~ $850^{\circ}C$. Due to $\textrm{Li}_{2}\textrm{O}$-induced basic fluxing mechanism, the corrosion rates of the alloys in mixed molten salt of LiC1-$\textrm{Li}_{2}\textrm{O}$ were significantly higher than those in molten salt of LiCl. In the mixed molten salt, Fe-base alloys showed higher corrosion resistance than the Ni-base alloys. and Hastelloy C-276 with high Mo and W contents exhibited the highest corrosion rate among the examined alloys. The single layer of $\textrm{LiCrO}_{2}$ was formed in molten salt of LiCl and two phase structure of a scale consisted of oxides and Ni was formed in the mixed molten salt.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.294-295
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• 1997

CO-Cr 수직자기기록 매체의 우수한 하지층을 개발하기 위하여, 스피넬 결점막$(Fe,M)_3O_4$ (M=Ni,Zn)이 스핀스프레이 페라이트 플레이팅 방법으로 유리 기판 위에 제작되었다. 반응액과 산화액은 기판이 회전하는 반응용기로 분사되었다. 반응은 기판의 회전소독, 반응온도, 반응액과 산화액의 유속 그리고 반응액과 산화액의 농도에 의해 영향받았다. 반응액과 산화액의 유속은 60(ml/min)으로 하고, 반응온도는 90[$^{\circ}C$] 그리고 기판의 회전속도는 150[rpm]의 조건하에서, 페라이트 플레이팅 반응에 미치는 반응액과 산화액 농도의 영향이 화학적 조성, 결정학적 및 자기적 특성의 관점에서 연구되었다. $Ni_{0.34}Zn_{0.66}Fe_2O_4$의 조성에서, 우리는 가장 안정한 결정학적 및 자기적 특성을 얻었다.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.245-250
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• 1999

The effect of substrate and oxidization time on $substrate /Py/Al_2O_3/Co\;(Py=Ni_{81}Fe_{19})$ tunnel junction was studied. Samples were prepared without breaking vacuum by changing shadow masks in-situ. The resistance of tunnel junctions increased, but measured MR decreased with oxidization time. Negative MR observed for samples of tunnel resistivity lower than 0.17 M$\Omega$ $({\mu}m)^2$. MR resistivity decreased with the change of substrates in the order of thermally oxidized Si(111), Si(100), Coring Glass 2948, Corning Glass 7059. Sign change and the variation of MR was explained with non uniform current effect.