• Journal of Magnetics
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• v.6 no.3
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• pp.90-93
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• 2001

Co/$Al_O_3$/NiFe and CO/$Al_O_3$/Co tunnel junctions were fabricated by a radio frequency magnetron sputtering at room temperature with hard mask on glass and $4^{\circ}$ tilt cut Si (111) substrates. The barrier layer was formed through two steps. After the Al layer was deposited, it was oxidized in the chamber of a reactive ion etching system (RIE) with $O_2$plasma at various conditions. The dependence of the TMR value and junction resistance on the thickness of Al layer (before oxidation) and oxidation parameters were investigated. Magnetoresistance value of 7% at room temperature was obtained by optimizing the Al layer thickness and oxidation conditions. Circular shape junctions on $4^{\circ}$tilt cut Si (111) substrate showed 4% magnetoresistance. Photovoltaic energy conversion effect was observed with the cross-strip geometry junctions on Si substrate.

• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.311-317
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• 1981

A new nickel(II) compound, $Ni(CH_2SiMe_3)_2((C_6H_5)_2PCH_2CH_2P(C_6H_5)_2)$, 1, has been prepared by the reaction of $NiCl_2((C_6H_5)_2PCH_2CH_2P(C_6H_5)_2)$ with $Me_3SiCH_2Li$. The compound, 1, is stable under nitrogen at room temperature both in solution and in the solid state. Thermal decomposition of 1 in solution or in the solid produces the reductive coupling product, $Me_3SiCH_2CH_2SiMe_3$ which is also afforded by the reactions of 1 with CO and $O_2$ at room temperature, and with $(C_6H_5)_2PCH_2CH_2P(C_6H_5)_2$ at 80${\circ}$C.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.44-45
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• 2006

초고용량 캐패시터(Supercapacitor)는 이차전지와 더불어 차세대 전지로 분류되는 신형에너지 장치로서 충 방전 속도가 다르고 순간 전력공급이 가능하며 충 방전 수명이 반영구적으로 길고 고출력을 내기 때문에 이차전지가 갖지 못하는 영역에서 동력에너지원으로 사용된다. 본 연구에서는 초고용랑 캐패시터의 전극소재인 탄소계 재료를 대신하여 비탄소계 전극소재인 $Li_4Ti_5O_{12}$의 고상법 제조를 위한 Li/Ti의 최적 조성과 혼합 방법으로 Li-Ti 계에 $Fe_2O_3$, NiO, $Nb_2O_5$, $Sb_2O_3$ 그리고 ZnO와 같은 금속산화물로 치환시켜 합성된 Li -Ti계 금속산화물의 특성 및 충 방전 효과에 미치는 영향을 관찰하고자 하였다.

• Korean Journal of Environmental Agriculture
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• v.18 no.4
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• pp.321-326
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• 1999

This study was performed to evaluate the quality of produced compost and to analyse the change of a component during the reduction compost according to the input volume. The volume of pilot scale used in this study was about 300㎥. The pile of 2m width, 20m length and 1.2m height was constructed. Woodchip was used as bulking agent to enhance pore volume of composting bay and to control water content of food waste in starting time. Food waste was turned using a mechanical tumer twice a day. The result are as follows : In these cases of input volume of $2m^3$ and $3.5m^3$, temperature of composting pile was maintained over $60^{\circ}C$ and water content was 43.6% and 47.2%, respectively. It was proved that microorganisms activity was maintained high in each input volume. After operation of step 1 and step 2, pH and organic matter in the final compost were 6.2, 6.6 and 84.3%, 79.6%, respectively. Cation concentration such as $K_2O,$ CaO and NaCl was accumulated in the compost during the composting period. NaCl concentration in the final compost was 4.62%, 4.92%, respectively. Hence, If was recommended that this compost should be applied to others expect agricultural area or mixed with a low concentration other compost. In the steps 1, input volume of $2m^3$, heavy metal concentration of Pb, Cu, Cr, Ni. Cd were 37.82㎎/㎏, 56.87㎎/㎏, 9.8㎎/㎏. 22.21㎎/㎏ and 3.69㎎/㎏, and 44.55㎎/㎏, 95.54㎎/㎏, 12.22㎎/㎏, 24.94㎎/㎏, and 3.86㎎/㎏ in the step 2.

• Journal of Environmental Science International
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• v.20 no.6
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• pp.687-700
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• 2011

A new $N_3-O_2$ pentadentate ligand, H-BHPT, was synthesized. Hydrochloric acid salts of Br-BHPT, Cl-BHPT, $CH_3O$-BHPT and $CH_3$-BHPT, having Br-, Cl-, $CH_{3-}$ and $CH_3O-$ substituents at the para position of the phenol hydroxyl group of H-BHPT were synthesized. Hydrochloric acid salts of 3OH-BHPT and 4OH-BHPT, having different position of the phenol hydroxyl group of H-BHPT were also synthesized. The synthesis of each ligand was confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible, and mass spectra. The calculated proton dissociation constants ($log{K_n}^H$) of the phenol hydroxyl group and secondary amine group of the synthesized $N_3-O_2$ ligands showed five steps of the proton dissociations. The order of the overall proton dissociation constants ($log{\beta}_p$) of the ligands was Br-BHPT < Cl-BHPT < H-BHPT < $CH_3O$-BHPT < $CH_3$-BHPT. The order agreed with that of Hammett substituent constants (${\delta}_p$). However, dissociation steps of 3OH-BHPT were four and that of 4OH-BHPT was three. The calculated stability constants ($logK_{ML}$) between the ligands and transition metal ions agreed with the order of $log{\beta}_p$ values of the ligands. The order of the stability constants between the transition metal ions with the synthesized ligands was Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II). The order agreed well with that of the Iriving-Williams.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.21-21
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• 2006

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.587-594
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• 2004

Three-dimensionally ordered macroporous (3DOM) structures of the $LiCoO_2$ electrode materials for Li secondary batteries were fabricated by using the close-packed arrays of PMMA spheres served as templates. In order to successfully fabricate the cathode materials with highly ordered array form, the metal citrates were applied to new precursors. The precursor/template composites were prepared by the infiltration with metal citrate precursors into the voids of template. By removing the PMMA templates, then, the inverse opal structures with the uniform pores of narrow size distribution were resulted. It was confirmed that the 3DOM $LiCoO_2$ material is to take a single phase of rocksalt (R3m) structure. In addition, 3DOM $LiNiO_2$ and $LiMn_{2}O_4$ cathode materials were fabricated using an identical preparation procedure. Also, the morphology of the 3DOM cathode materials calcined at $500^{\circ}C\;to\;700^{\circ}C$ was observed by scanning electron microscope.

• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.3-12
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• 1979

The effects of sintering temperature and sintering atmosphere on magnetic properties and microstructuresof Mn-Zn ferrites have been studied. Mixture of 52.8mole% $Fe_2O_3$, 26.4mole% MnO, 15.1mole0% ZnO and 5.7mole% NiO was prepared, and 0.1mole% CaO, 0.02mole% $SiO_2$ were added as minor additives. After calcining and ball milling the powder was granulated for compacting. The specimens were sintered at $1, 250^{\circ}$, $1, 300^{\circ}$and 1, 35$0^{\circ}C$ in the various atmosphere of $N_2$, $N^_2\DIV0.6% O_2$, $N_2＋2.7% O_2$, $N_2＋4.1% O_2$, $N^2＋8.2% O_2$ and air for 3 hours and cooled in $N_2$ atmosphere. The grian growth rate and densities increase as sintering temperature and oxygen content of atmosphere increase. At the sintering temperature of $1, 250^{\circ}C$ the initial permeabilities increase as oxygen content of atmosphere increase. At the sintering temperature of$ 1, 300^{\circ}$and $1, 350^{\circ}$ the initial permeabilities show maximum values at $N_2＋4.1% O_2$ atmosphere. The secondary peaks of initial permeabilities are observed between 100$^{\circ}$and 20$0^{\circ}C$, and the positions of secondary peaks move to higher temperature as oxygen content of atmosphere increases. Q-factors decrease as sintering temperature increases and oxygen content of atmosphere decreases.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.199-202
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• 2009

본 연구에서는 내부 개질반응에서 사용되는 고함량의 니켈촉매(Ni/Al2O3계열 촉매)제조를 위해, 요소(urea)를 이용한 균일용액 침전법을 이용하여 니켈이 고분산된 52wt% Ni/$Al_2O_3$ 촉매를 제조하였다. 제조 촉매는 BET 표면적, 니켈분산도, 니켈표면적 등 물리.화학적 물성 모두 우수하였으며, 환원 패턴은 상용촉매와 비슷하게 나타났다. 실제 반응온도인 $650^{\circ}C$에서 소성하여 화학흡착을 비교한 결과,상용촉매는 니켈분산도 및 니켈표면적이 감소한 반면 균일용액 침전법으로 제조한 촉매는 거의 변화가 없었다. 개질 성능 또한 상용촉매보다 우수하였는데, 이것은 균일용액 침전법으로 제조한 촉매는 활성점(니켈)이 지지체에 나노사이즈로 고르게 잘 분산되었기 때문이라고 판단하였다. 또한 합성온도 조절을 통해, $650^{\circ}C$ 소성 후에 물성변화를 살펴보았고 합성온도 $85^{\circ}C$에서 고분산 니켈 촉매 제조가 가능하였다.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.40-49
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• 1994

Potentiometric cell oxygen sensors using $CaF_{2}$ were fabricated for monitering the oxygen partial pressure in the low temperature range ($300^{\circ}C{\sim}$500^{\circ}C). The disk type oxygen sensors consist of a reference electrode: Air($O_{2}:21%$)|Pt, a solid electrolyte $CaF_{2}$, and a sensing metel Pt electrode. And the change in open circuit emf of the disk type cell was about 45mV for the oxygen concentration range, $0.1%{\sim}10%$, at the cell temperature of $400^{\circ}C$. Also, the reference electrode incorporated type sensor showed the change of 40mV for 0.1% to 10% oxygen partial pressure range.