• Bulletin of the Korean Chemical Society
• /
• 제17권7호
• /
• pp.625-630
• /
• 1996

The cobalt-substituted polyoxotungstate [(CoPW11O39)5-] has been used as a catalyst in olefin epoxidation and alkane hydroxylation reactions. The epoxidation of olefins by iodosylbenzene in CH3CN yielded epoxides predominantly with trace amounts of allylic oxidation products. cis-Stilbene was streoselectively oxidized to cis-stilbene oxide with small amounts of trans-stilbene oxide and benzaldehyde formation. The epoxidation of carbamazepine (CBZ) by potassium monopersulfate in aqueous solution gave the corresponding CBZ 10,11-oxide product. Other transition metal-substituted polyoxotungstates (M=Mn2+, Fe2+, Ni2+, and Cu2+) were inactive in the CBZ epoxidation reaction. The cobalt-substituted polyoxotungstate also catalyzed the oxidation of alkanes with m-chloroperbenzoic acid to give the corresponding alcohols and ketones. The presence of CH2Br2 in the hydroxylation of cyclohexane afforded the formation of bromocyclohexane, suggesting the participation of cyclohexyl radical. In the 18O-labeled water experiment, there was no incorporation of 18O into the cyclohexanol product when the hydroxylation of cyclohexane by MCPBA was carried out in the presence of H218O. Some mechanistic aspects are discussed as well.

• Journal of Electrical Engineering and Technology
• /
• 제6권2호
• /
• pp.280-283
• /
• 2011

In the present work, a new approach is proposed for via interconnects of semiconductor devices, where multi-wall carbon nanotubes (MWCNTs) are used instead of conventional metals. In order to implement a selective growth of carbon nanotubes (CNTs) for via interconnect, the buried catalyst method is selected which is the most compatible with semiconductor processes. The cobalt catalyst for CNT growth is pre-deposited before via hole patterning, and to achieve the via etch stop on the thin catalyst layer (ca. 3nm), a novel 2-step etch scheme is designed; the first step is a conventional oxide etch while the second step chemically etches the silicon nitride layer to lower the damage of the catalyst layer. The results show that the 2-step etch scheme is a feasible candidate for the realization of CNT interconnects in conventional semiconductor devices.

• Journal of Electrical Engineering and Technology
• /
• 제6권2호
• /
• pp.233-238
• /
• 2011

In the present work, a new approach is proposed for via interconnects of semiconductor devices, where multi-wall carbon nanotubes (MWCNTs) are used instead of conventional metals. In order to implement a selective growth of carbon nanotubes (CNTs) for via interconnect, the buried catalyst method is selected which is the most compatible with semiconductor processes. The cobalt catalyst for CNT growth is pre-deposited before via hole patterning, and to achieve the via etch stop on the thin catalyst layer (ca. 3nm), a novel 2-step etch scheme is designed; the first step is a conventional oxide etch while the second step chemically etches the silicon nitride layer to lower the damage of the catalyst layer. The results show that the 2-step etch scheme is a feasible candidate for the realization of CNT interconnects in conventional semiconductor devices.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.263-263
• /
• 2010

High temperature annealing is required to synthesize graphene using CVD. When thin metal catalyst is used for the synthesis, the high temperature pre-annealing makes the thin catalyst highly agglomerated. We investigated the agglomeration effect on the shape of the synthesized graphene. It is found that high temperature annealing makes randomly distributed many hole or blister on metal catalyst, and the synthesized graphene features floral pattern around the hole. The floral patterns of graphene turned out to be multi-layers and higher D peaks in raman spectrum.

• 한국자원리싸이클링학회:학술대회논문집
• /
• 한국자원리싸이클링학회 2003년도 추계정기총회 및 국제심포지엄
• /
• pp.216-219
• /
• 2003

• Bulletin of the Korean Chemical Society
• /
• 제26권10호
• /
• pp.1585-1587
• /
• 2005

• Bulletin of the Korean Chemical Society
• /
• 제21권12호
• /
• pp.1239-1244
• /
• 2000

A study of K addition to the catalyst of CoMo/ ${\gamma}-Al_2O_3$ was studied. The catalyst with 10 at% of K to Mo atoms in 3C10M, the catalyst added 3 wt% CoO to 10 wt% $MoO_3/{\gamma}-Al_2O_3$, showed the highest activity for water gas shift reaction. The addition of K retarded the reducibility of cobalt-molybdenum catalysts. It gave, however, good dispersion and large BET surface area to the catalysts which were attributed to the disappearance of polymolybdate clustyer such as $Mo_7O_{24}^{6-}$ and the formation of small Mo$O_4^{2-}$ cluster. It was confirmed by the analyses of pore size distribution, activation energy, Raman spectroscopy, and electron diffraction. The activation energies and the frequency factors of the catalysts 3C10M and 5KC10M (the catalyst added 5 at% K for Mo to the catalyst 3C10M) were 43.1 and 47.8 kJ/mole, and 4,297 and 13,505 $sec^{-1}$, respectively. These values were also well correlated with our suggestion. These phenomena were attributed to the direct interaction between K and CoMo oxides irrelevant to the support.

• 한국재료학회지
• /
• 제9권7호
• /
• pp.675-679
• /
• 1999

$PdCl_2$를 촉매제로 사용한 수소환원분위기에서 $Co(OH)_2$ 로부터 약 400nm크기인 구형의 코발트분말 제조에 관한 연구를 수행하였다. 본 실험에서 코발트의 환원반응속도는 표면반응 코어모델식에 잘 일치하였으며 이때 활성화 에너지는 $145~195^{\circ}C$에서 약 55.6KJ/mol 이었다. 또한 코발트의 환원속도는 초기 수소분압의 0.63승에 비례하는 가스화학흡착반응식으로 표시할 수 있다.

• 한국재료학회지
• /
• 제32권10호
• /
• pp.408-413
• /
• 2022

The oxygen evolution reaction (OER) is very sluggish compared to the hydrogen evolution reaction (HER). Considering this difference is essential when designing and developing a cost-effective and facile synthesis method for a catalyst that can effectively perform OER activity. The material should possess a high surface area and more active sites. Considering these points, in this work we successfully synthesized sheets of cobalt phosphate hydrate (CP) and sulphurated cobalt phosphate hydrate (CPS) material, using simple successive ionic layered adsorption and reaction (SILAR) methods followed by sulfurization. The CP and CPS electrodes exhibited overpotentials of 279 mV with a Tafel slope of 212 mV dec^-1 and 381 mV with a Tafel slope of 212 mV dec^-1, respectively. The superior performance after sulfurization is attributed to the intrinsic activity of the deposited well-aligned nanosheet structures, which provided a substantial number of electrochemically active surface sites, speeded electron transfer, and at the same time improved the diffusion of the electrolyte.

• Macromolecular Research
• /
• 제13권1호
• /
• pp.2-7
• /
• 2005

A series of ethylene polymerization catalysts based on tridentate bis-imine ligands coordinated to iron and cobalt was reported. The ligands were prepared through the condensation of sterically bulky anilines with allyloxy-and benzyloxy-substituted 2,6-acetylpyridines. The pre-catalyst complexes were penta-coordinate species of the general formula $\{[(ArN=C(Me))_2(4-RO-C_5H_3N)]MCl_2\}$ (Ar=ortho dialkyl-substituted aryl ring; R=allyl, benzyl; M=Fe, Co). In the presence of ethylene and methyl alumoxane cocatalysts, these complexes were active for the polymerization of ethylene, with activities lower than those of metal complexes of the general formula $\{[(2-ArN=C(Me)_2C_5H_3N]MCl_2\}$ (Ar=ortho dialkyl-substituted aryl ring; M=Co, Fe), containing no substituents in 2,6-acetylpyridine ring. The effects of the catalyst structure and temperature on the polymerization activity, thermal properties, and molecular weight were discussed.