• 한국환경과학회지
• /
• 제18권10호
• /
• pp.1071-1077
• /
• 2009

A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below $100^{\circ}C$. This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was continued by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below $100^{\circ}C$.

• Korean Chemical Engineering Research
• /
• 제51권4호
• /
• pp.432-437
• /
• 2013

고분자 전해질 연료전지 구동 시 양극 활성 물질에 대한 CO 피독을 방지하기 위해 Cu를 촉매 활성 종으로 사용하고 반응물의 확산이 용이한 몇 가지 메조 세공 물질을 지지체로 이용하여 CO 선택적 산화 반응(PROX반응)을 실시하였다. 그 결과 거대 세공을 가진 SBA-15를 지지체로 사용했을 때 우수한 CO 산화 활성을 보였으며 특히 Cu 담지 량에 비례하여 활성은 증가하였다. 또한 Cu의 분산도를 높이고자 첨가한 Ti 성분은 저온에서 CO 산화 성능을 높이는데 기여하였다. 특히 Ti 성분을 20 wt-% 첨가한 Cu/Ti20-SBA-15 촉매에서 Cu의 분산도가 가장 우수하였으며 CO 산화활성 역시 개선됨을 확인하였다.

• Corrosion Science and Technology
• /
• 제7권3호
• /
• pp.145-151
• /
• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 추계학술대회 논문집
• /
• pp.269-274
• /
• 2001

This paper describes the experimental results on direct selective laser sintering of WC-Co mixture. The experiments were carried out within an air, argon and nitrogen atmosphere. The main problem occurred during sintering within an air atmosphere was oxidation of WC-Co mixture. As the power of laser is increased and scanning speed is decreased, more severe oxidation takes place. Within an argon and nitrogen atmosphere the oxidation is reduced significantly. As the energy density is increased the thickness of the sintered layer is increased.

• Bulletin of the Korean Chemical Society
• /
• 제23권6호
• /
• pp.851-856
• /
• 2002

The Reaction of S-methyl-S-cysteine(L-Smc) with racemic $s-cis-[Co(demba)Cl_2]-1$ (Hydmedba = $NN'-dimethylethylenediamine-NN'-di-\alpha-butyric$, acid) yields ${\Delta}$-s-cis-[Co(dmedba)(L-Smc)] 2 with N, O-chelation. Oxidation of sulfur of 2 with $H_2O_2$ in a 1 : 1 mole ratio gives ${\Delta}$-s-cis[Co(dmedba)(L-S(O)mc)] 3 having an uncoordinated sulfenate group. Oxidation of sulfur of L-Sm with $H_2O_2in$ a 1: 1 mole ratio produces S-methyl-L-cysteinesulfenate (L-S(O)me) 5. Direct reaction of 1 with 5 in basic medium gives an N.O-chelated ${\Delta}$s-cis[Co(dmedba)(L-S(O)mc)-N.O], which turmed out be same as obtained by oxidation of 2, while an N, S-chelated ${\Delta}$-s-cis-[Co(dmedba)(S-S(O)mc)-N,O] complex 4 is obtained in acidic medium from the reaction of 1 with 5. This is one of the rare $[$Co^{III}$(N_2O_2-type$ ligand)(amino acid)] type complex preparations, where the reaction conditions determine which mode of N, O and N, S caelation modes is favored.

• 대한금속재료학회지
• /
• 제48권10호
• /
• pp.907-913
• /
• 2010

Hot-rolled steel plates of SPHC and SS400 were oxidized at 600, 750 and $900^{\circ}C$ for 2 hr in air. With an increase in the oxidation temperature, their oxidation rates increased, and this was accompanied by the formation of pores and cracks in the thickened oxide scales, which were non-adherent. SPHC steels manufactured by either an arc furnace or a blast furnace displayed similar oxidation rates, indicating that their oxidation rates were insensitive to the manufacturing process. Medium-carbon SS400 steel displayed somewhat faster oxidation rates than low-carbon SS400 steel, indicating that the carbon content did not significantly influence the oxidation rates.

• 공업화학
• /
• 제9권4호
• /
• pp.497-503
• /
• 1998

알루미나에 담지한 귀금속 촉매를 이용하여 1.2-dichloroethane의 산화분해반응을 수행하였다. 실험결과 전환율은 Ru > Pt > Pd $${\sim_=}$$ Rh 순으로 높게 나타났으나, 완전산화 반응이 일어날 때의 주생성물인 $CO_2$로의 전환율 및 선택도를 기준으로 활성을 비교할 때 Pt/alumina가 Ru/alumina보다 활성이 높게 나타났다. $CO_2$ 및 vinyl chloride가 반응 주생성물로 검출되었는데, 반응 생성물 분포로부터 1.2-dichloroethane의 분해반응 경로는 1단계로 dehydrochlorination에 의해 vinyl chloride가 생성된 후 2단계로 vinyl chloride가 $CO_2$로 oxidation됨을 알 수 있었다. 염소를 포함하고 있는 반응 주생성물인 HCl의 영향을 살펴보기 위하여 반응물에 HCl을 첨가하여 반응을 수행하였는데 $300^{\circ}C$ 이하에서는 HCl이 촉매 표면에 흡착함에 따라 표면의 산도를 증가시켜 1.2-dichloroethane의 전환율은 증가하지만 $300^{\circ}C$ 이상에서는 HCl과 촉매 표면과의 상호작용이 약해져 전환율에는 큰 영향을 주지 않았다. 또한 촉매 표면에 가역적으로 흡착된 HCl은 1.2-dichloroethane의 $CO_2$로의 완전산화 반응을 방해함을 확인하였다.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.355-356
• /
• 2006

WC-TiC-TaC binderless cemented carbide was oxidized under low partial pressure of oxygen (50ppm) at 873K for 1 to 20 h. Surface roughness was measured using atomic force microscope, and effect of TiC amount on oxidation behavior of the carbide was investigated. WC phase was oxidized more easily than WC-TiC-TaC solid solution phase. With an increase in TiC amount, WC-TiC-TaC phase increased and the oxidation resistance of the carbide increased.

• The Korean Journal of Physiology and Pharmacology
• /
• 제9권3호
• /
• pp.173-177
• /
• 2005

The purpose of this study was to discern the critical point in skeletal muscle fatty acid oxidation by changing plasma free fatty acids (FFA) level in rat. In the study, 3 key steps in lipid oxidation were examined after changing plasma FFA level by acipimox. The rates of both palmitate and palmitoylcarnitine oxidation were decreased by decrease of plasma FFA level, however, carnitine palmitoyl transferase (CPT) 1 activity was not changed, suggesting CPT1 activity may not be involved in the fatty acid oxidation at the early phase of plasma FFA change. In the fasted rats, ${\beta}-hydroxy$ acyl-CoA dehydrogenase (${\beta}$-HAD) activity was depressed to a similar extent as palmitate oxidation by a decrease of plasma FFA level. This suggested that ${\beta}-oxidation$ might be an important process to regulate fatty acid oxidation at the early period of plasma FFA change. Citrate synthase activity was not altered by the change of plasma FFA level. In conclusion, the critical step in fatty acids oxidation of skeletal muscles by the change of plasma FFA level by acipimox in fasting rats might be the ${\beta}-oxidation$ step rather than CPT1 and TCA cycle pathways.

• 생명과학회지
• /
• 제5권2호
• /
• pp.14-14
• /
• 1995

The effect of lipoxygenase (LOX) on the oxidation and co-oxidation of lipid fraction was studied in the model system of rainbow trout. For the reaction in model system 1 g of lipid fraction and 50mL of enzyme extract(LOX, 140 unit in 50mL phosphate buffer solution at pH 7,4)), which were obtained from rainbow trout, were homoginized in the presence of Tween 20 and kept at 23$\circ$C for 3 days. The activity of LOX was decreased to 43% of initial level during the reaction in the model system. The initial composition of rainbow trout lipid was showed to be consisted of trigliceride(TG;82%) and free fatty acid(FFA;0.1%), while this converted to 59% of TG and 20% of FIFA, respectively after reaction in model system. Change of fatty acid composition was also observed and the content of linoleic acid, one of the major fatte acids, was decreased to 13% from 54% in the content of total fatty acids after reaction. The carotenoids in rainbow trout were composed of 0.4% $\alpha$-carotene, 1.6% $\beta$ -carotene, 80% canthaxanthin, 7% lutein and 11% zeaxanthin, thus the canthaxanthin was the major component. This canthaxanthin was the most degraded carotenoid by lipoxygenase catalyzed co-oxidation during the reaction. On the other hand the tocopherol isomers found in the rainbow trout were $\alpha$ and $\beta$ -tocopherol, and $\alpha$-tocopherol had a higher degradation rate by the lipoxygenase catalyzed co-oxidation than of $\beta$-tocopherol in the reaction of model system.