• YAKHAK HOEJI
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• v.37 no.1
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• pp.95-99
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• 1993

Peroxidase activity of cytochrome P-450 was examined using N, N-dimethylaniline (NDA) as a substrate and cumene hydroperoxide (CHP) as an oxidant. The initial rates of the N-demethylation for varied concentrations of NDA (0.05-0.5 mM) by P-450 at different fixed concentrations of CHP (0.02-0.2 mM) were determined. The results suggest that P-450 proceeds its peroxidative reaction by the rapid equilibrium random bi bi mechanism to form a ternary complex with substrate and oxidant as an active intermediate.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.522-532
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• 1985

The reactions of p-nitrophenyldiphenylphosphate (p-NPDPP) with anions of benzimidazole (BI) and its 2-alkyl derivatives (R-BI) are strongly catalyzed by the micelles of cetyltrimethyl ammonium bromide (CTABr). On the other hand, the first order rate constants $(k'_{R-BI^-})$ and the second order rate constants $(k_{m(R-BI^-)})$ of the reactions mediated by R-$BI^-$in the micellar pseudophase are much smaller than those mediated by $BI^-$. In order to explain the slower rates of the micellar reactions mediated by R-$BI^-$, we compared the concentration-ratios ([R-$BI^-$]/[$BI^-$]) with the first order rate constant-ratios $(k'_{R-BI^-}/k'_{BI^-})$ and the second order constant-ratios $(k_{m(R-BI^-)}/k_{m(BI^-)})$ for the reactions taking place in the micellar pseudophase. The rate constant-ratios were much smaller than the concentration-ratios. For example in a 5 ${\times}10^{-4}$M butyl-BI solution, the two ratios were 0.089 and 0.430 (for the first order) respectively, and in a $10^{-4}$M butyl-BI solution the former was 0.100 (for the second order). This predicts that the reactivities of R-$BI^-$ in the micellar pseudophase are much smaller than that of $BI^-$. Based on the values of several kinetic parameters measured for dephosphorylation of p-NPDPP mediated by R-$BI^-$, a schemetic model is proposed. Due to the hydrophobicity and the steric effect of the alkyl substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long cetyl groups of CTABr. Consequently, the movements of R-$BI^-$ bound to the micelle should be restricted, leading to decreased collison frequencies between the nucleophiles and p-NPDPP. We refer this as an "anchor effect". This effect became more predominent when a larger alky group in R-BI was employed and when a greater concentration of R-BI was used.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.81-81
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• 2018

Bi-Te계 열전소자는 상온에서의 열전 효율이 우수하기 때문에 항공, 컴퓨터 등의 열전발전 또는 열전냉각 모듈에 널리 사용된다. 이 열전소자를 활용한 열전모듈은 다수의 n형 및 p형 열전소자가 세라믹 위에 형성된 Cu 전극에 전기적으로 직렬이 되도록 서로 솔더링 접합이 되어 있는 구조를 가지고 있다. 이처럼 직렬 연결된 방식에서는 높은 접합강도를 필요로 한다. 열전모듈 제작 시 Bi-Te 계 소자를 바로 Cu 기판에 접합시키면 솔더에 들어있는 Sn과 기판의 Cu가 접합하는 과정에서 소재 내로 확산하여 접합강도를 저하시킨다. 이러한 열전모듈의 접합강도 저하를 막기 위해 무전해 Ni-W-P 도금층을 확산 방지층으로 적용하였다. 본 연구에서는 Ni-W-P 도금이 Bi-Te 계 열전 모듈의 접합강도에 미치는 영향을 조사하였다. 본 연구에서는 Bi-Te계 열전소자에 양호한 밀착성을 가지는 Ni-W-P 도금층을 형성시키기 위해서 알루미나 분말을 이용한 sand-blasting 방법을 사용하여 Bi-Te 소재 표면에 분사하는 방법으로 표면을 거칠게 하였다. 그 후 무전해 Ni-W-P 도금을 $85^{\circ}C$에서 20분간 실시하여 약 4um의 Ni-W-P 도금층을 형성시켰다. 열전 모듈은 Sn-Ag-Cu 솔더를 사용하여 제작하였으며 접합강도는 Bonding tester를 사용하여 측정하였다. 제작한 열전 모듈의 단면 및 파단면 관찰을 통하여 접합강도가 변하는 요인을 조사하였다. 제작한 열전 모듈의 단면을 FE-EPMA로 관찰한 결과 Ni-W-P 도금층이 Bi-Te 소자와 Sn과 Cu사이의 확산을 방지하는 확산방지층 역할을 하는 것을 관찰할 수 있었다. 또한 열처리 전 열전모듈과 200도, 150시간 열처리 후 접합강도를 각각 측정해 본 결과, 열처리 후의 접합강도가 상승하는 것을 확인 할 수 있었다. 따라서 Bi-Te계 열전모듈 제작에 무전해 Ni-W-P 도금층을 형성시키므로 인해 확산방지층의 생성과 접합강도의 상승에 도움을 주었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.311-315
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• 2000

Vanadate glass in the $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ system containing 10mol% glass fonner, $P_2O_5$ and $Bi_2O_3$ was prepared by melting the batch in pt. crucible followed by Quenching on the copper plate. We found that $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass-ceramics obtained from nucleation of glass showed signifieantly higher capacity and longer cycle life than conventionally made crystalline $LiV_3O_{8}$. In the present paper, we describe the charge / discharge properties during crystallization process and find the best crystallization condition of $LiO_2-P_2O_5-Bi_2O_3-V_2O_5$ glass as cathod material.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.11a
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• pp.469-472
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• 2006

BI 및 ETABr의 농도변화에 따른 속도상수의 변화는 이 반응이 단순한 1차 및 2차 반응 속도식에 맞지 않는다. 이와 같은 현상은 용액 속에서 두 반응 시약인 p-NPDPIN 및 BI와 상전이촉매인 ETABr 사이에 많은 수의 작은 응집된 입자(aggregates)을 형성함을 의미한다. 수용액 속에서는 불용성인 p-NPDPIN과 수용성인 BI가 충돌하여 반응할 기회가 적은데 반하여 ETABr은 이 두 시약을 함께 수용하여 세 분자 사이에 응집현상이 일어남으로 p-NPDPIN과 BI가 반응하기에 충분한 거리 내에 있게 된다. 바꾸어 말하면, 이 두 반응물질이 1:1 adducts로 반응하기보다는 여러 ETABr과 함께 많은 수의 반응분자들이 회합(응집) 되어 있음을 뜻한다.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.678-683
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• 1996

In the fabrication processes of thin film thermoelectrics, a subsequent annealing treatment is inevitable to reduce the defects and residual stresses introduced during the film growth, and to make the uniform carrier concentration of the film. However, the diffusion-induced atomic redistribution and the broadening of p/n junction region are expected to affect the thermoelectric properties of thin film modules. The present study intends to investigate the diffusion at the p/n junctions of thermoelectric thin films and to relate it to the property changes. The film junctions of p-type(Bi0.5Sb1.5Te3)and n-type(Bi2Te2.4Se0.6)were prepared by the flash evaporation method. Aluminum thin layer was employed as a diffusion barrier between p-and n-type films of the junction. This was found to be an effective barrier by showing a negligible diffusion into both type films. After annealing treatment, the thermoelectric properties of p/n couples with aluminum barrier layer were accordingly retained their properties without any deterioration.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.46-47
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• 1994

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.623-626
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• 2002

High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, Tsub, and ozone gas pressures, pO$_3$. The correlation diagrams of the BSCCO phases with Tsub and pO$_3$are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputterina Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on Tsub and pO$_3$. From these results, the thermodynamic evaluation of ΔH and ΔS, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.550-553
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• 2001

$Li_{2}O-P_{2}O_{5}-Bi_{2}O_{3}-V_{2}O_{5}$ glass containing glass former, $P_{2}O_{5}$ and $Bi_{2}O_{3}$ was prepard by melting the glass batch in pt. erucible followed by guenching on the copper plate. We found that $Li_{2}O-P_{2}O_{5}-Bi_{2}O_{3}-V_{2}O_{5}$ glass-ceramics obtained from the crystallization of glass showed signifieantly higher capacity and longer cycle life tham $LiV_{3}O_{8}$ made from powder synthesis. In this paper, we described crystallization process and $LiV_{3}O_{8}$ crystal growth in glass matrix by increasing temperature. The electrochemical properties were strongly affected by $LiV_{3}O_{8}$ crystal growth in matrix

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.550-553
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• 2001

Li$_2$O-P$_2$O$_{5}$-Bi$_2$O$_3$-V$_2$O$_{5}$ glass containing glass former, P$_2$O$_{5}$ and Bi$_2$O$_3$ was prepard by melting the glass batch in pt. erucible followed by quenching on the copper plate. We found that Li$_2$O-P$_2$O$_{5}$-Bi$_2$O$_3$-V$_2$O$_{5}$ g1ass-ceramics obtained from the crystallization of glass showed significantly higher capacity and longer cycle life tham LiV$_3$O$_{8}$ made from powder synthesis. In this paper, we described crystallization process and LiV$_3$O$_{8}$ crystal growth in glass matrix by increasing temperature. The electrochemical properties were strongly affected by LiV$_3$O$_{8}$ crystal growth in matrix.rowth in matrix.