• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.161-166
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• 2001

• 한국전기화학회:학술대회논문집
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• 2004.06a
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• pp.277-280
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• 2004

• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.692-694
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• 1994

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.607-614
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• 1996

Yttrium(Y) coating was incorporated by ion-plating method either directly on the TiAl substrate or after pack aluminizing on TiAl to improve the oxidation resistance of TiAl alloy. After Y-coating, heat treatment at low oxygen partial pressure was carried out. Performance of various coating was evaluated by isothermal and cyclic oxidation tests. A simple Y-coating without pack aluminizing can give a detrimental effect on the. oxidation resistance of TiAl alloy, because it enhances formation of $TiO_2$. On the other hand, a composite coating of aluminide-yttrium has shown excellent oxidation resistance. A continuous protective $Al_2O_3$ scale is formed on the aluminized TiAl, and Y-coating improves $Al_2O_3$ scale adherence and substantially prevents depletion of Al in the aluminide-coating layer.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.105-114
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• 2004

This study investigated the thermal behavior of the nuclear graphite waste generated from the decommissioning of the Korean nuclear research reactor, The first part study investigated the decomposition rate of the nuclear graphite waste up to $1000^{\circ}C$ under various oxygen partial pressures using a thermo-gravimetric analyzer (TGA). Tested graphite waste sample not easily destroyed in the oxygen-deficient condition. However, the gas-solid oxidation reaction was found to be very effective in the presence of oxygen. No significant amount of the product of incomplete combustion was formed even in the limited oxygen concentration of 4% $O_2$. The influence of temperature and oxygen partial pressure was evaluated by the theoretical model analysis of the thermo-gravimetric data. The activation energy and the reaction order of graphite oxidation were evaluated as 128 kJ/mole and 1.1, respectively. The second part of this study investigated the behavior of radioactive elements under graphite oxidation atmosphere using thermodynamic equilibrium model. $^{22}Na$, $^{134}Cs$ and $^{137}Cs$ were found be the semi-volatile elements. Since volatile uranium species can be formulated at high temperatures above $1050^{\circ}C$, the temperature of incinerator furnace should be minimized. Other corrosion/activation products, fission products and uranium were found to be the non-volatile species.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.238-246
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• 1994

Partial oxidation of cyclohexane by HOOH was carried out with the transition metal complexes composed of Fe(II) or Fe(III)/picolinic acid derivatives. The major products were turned out to be cyclohexanone and cyclohexanol wlth the one/ol ratios of 3~10. The best performance was observed in a mixed solvent of pyridine/acetic acid(volume ratio 2.5:1, pH 5.3) and optimal temperature was $25{\sim}40^{\circ}C$. It was known that cyclohexyl hydroperoxide is the reaction intermediate, and that the reaction dominantly follows non-radical pathways which was ascertained from the results of the adamantane oxidation and radical trap experiments.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.669-673
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• 2002

Ni catalyst (Ni: 15 wt%) supported on precalcined SiO2 has been investigated in reforming reactions of methane to synthesis gas. The catalyst exhibited fairly good activity and stability in partial oxidation of methane (POM), whereas it deactivated in steam reforming of methane (SRM). Pulse reaction results of CH4, O2, and CH4/O2 revealed that Ni/SiO2 has high capability to dissociate methane. The results also revealed that both CH4 and O2 are activated on the surface of metallic Ni, and then surface carbon species react with adsorbed oxygen to produce CO and CO2 depending on the bond strength of the oxygen species on the catalyst surface.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.499-502
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• 2008

고정층반응기에서 니켈이 치환된 하이드로탈사이트($Ni_3Mg_3Al_2(CO_3)(OH)_{{16}{\cdot}n}H_2O$ ; n=3$\sim$5)를 합성하고 여기에 세리아를 첨가 후 소성하여 얻은 촉매를 사용하여($Ce_xNi_3$-HTlc ; x=0.3$\sim$1.2) 메탄의 부분산화 반응실험을 수행하였다. 세리아가 첨가되지 않은 촉매는 반응 초기 활성이 세리가가 소량 첨가된 ($Ce_{0.3}Ni_3$-HTlc) 촉매보다 우수하였으나 장시간 반응에서는 차차 활성이 저하되었으나, $Ce_{0.3}Ni_3$-HTlc의 활성은 30시간까지 일정하게 유지 되었다. 세리아 함량이 많아 질수록 촉매 활성은 점차 저하되었으며, $Ce_{1.2}Ni_3$-HTlc 는 촉매활성이 매우 낮았다.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.68-71
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• 2011

[ $Ti_{1-x}W_xO_{2-y}$ ]solid solutions with compositions of x = 0.01(TW-1), x = 0.02(TW-2), x = 0.03(TW-3) and x = 0.04(TW-4) were prepared at 1,073 K in air under atmospheric pressure. All the solutions exhibited tetragonal symmetries. Nonstoichiometric chemical formulas have been obtained from oxidation-reduction titration and the partial substitution of $W^{6+}$ ions mainly caused the formation of $Ti^{3+}$ ion, rather than oxygen excess. Resistivities of the samples were highly dependent on humidity. The increase of the W amount resulted in an increase of $Ti^{3+}$ content, decrease of resistivity values and finally degradation of photocatalytic activities.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.1-7
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• 2006

A reaction mechanism of methane partial oxidation, which consists of thermal and plasma chemistry reaction pathways, has been investigated using with an arc-jet reactor. The reaction zone of the arc-jet reactor is spatially separated into thermal and non-thermal plasma zone. Methane conversion rates, selectivity of $H_2$ and $C_2$ chemicals in each zone are obtained, which reveals clearly different characteristics of reaction pathways depending on the temperature conditions. The conversion rates obtained in thermal plasma zone is higher than those in non-thermal plasma zone. The selectivity, however, obtained in non-thermal plasma zone is significantly higher than those in thermal plasma zone. Further parametric study on $O_2/C$ ratio, arc length and SED shows that the present process is mainly governed by thermal chemistry pathways.