• 한국세라믹학회지
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• 제42권12호
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• pp.846-853
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• 2005

For the performance prediction of a planar-type solid oxide fuel cell, the computational analysis of transport phenomena with a simplified treatment of heat generation by the electrochemical reaction is conducted. From the result of the computational analysis, it is shown that the electrochemical reaction is closely related to the transport phenomena inside a solid oxide fuel cell. Transport phenomena including heat and mass transfer influences on the distribution of local current density and, as a result, on the performance characteristics of the fuel cell. Computational analysis is also extended to the parametric study to investigate the performance behavior of the fuel cell with different amount of supplied fuel flow rates. It is also demonstrated that the mathematical formulation and computational procedures proposed in this study can be applied to prove the importance of the specific TPB area in the manufacturing process of electrodes in solid oxide fuel cells.

• 대한화학회지
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• 제37권8호
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• pp.730-734
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• 1993

비양성자성 용매인 N,N-dimethylformamide(DMF) 중에서 Biliverdin(BV)의 전기화학적인 환원거동을 직류폴라로그래프법, 순환전압전류법 및 정전위 전기량법으로 조사하였다. 또한 BV의 최종 환원생성물을 UV-Vis spectroscopy로 조사하였다. DMF 용매 중에서 BV는 -0.71 V vs. Ag/Ag$^+$와 -0.91 V vs. Ag/Ag$^+$ 에서 2개의 환원파를 보였다. 각 환원파의 전류유형은 제 1환원파는 확산지배적인 전류였으며, 제 2환원파는 반응성 전류가 약간 포함된 확산전류이었다. 그리고 제 1단계의 환원과정은 비가역적이었다. 각 환원단계에 관여하는 전자수는 1개씩 이었으며, BV은 DMF 용액 중에서 1전자 2단계의 환원과정을 거쳐서 Bilirubin으로 환원되었다.

• 한국표면공학회지
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• 제48권6호
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• pp.354-359
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• 2015

Stainless steel has poor corrosion resistance in marine environment due to the breakdown of a passive film caused by chloride. It suffers electrochemical corrosion like pitting corrosion, crevice corrosion, and stress corrosion crack (SCC) in marine environment. In general, it indicates that the passive film of $Al_2O_3$ has better corrosion resistance than that of $Cr_2O_3$ in seawater. This paper investigated the damage behavior 304 stainless steel and hot-dip aluminized 304 stainless steel in seawater solution. Various electrochemical experiments were carried out including potential measurement, potentiodynaimic experiment, Tafel analysis and galvanostatic experiment. As a result of anodic polarization experiment, higher pitting damage depth was indicated at 304 stainless steel than hot-dip aluminized 304 stainless steel. In addition, relatively higher corrosion current density was shown at hot-dip aluminized stainless steel as a result of Tafel analysis.

• 한국표면공학회지
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• 제48권6호
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• pp.343-348
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• 2015

In this paper, arc Zn thermal spray coating was carried out on the SS400 steel, and then various electrochemical characteristics and surface damage behavior of Zn thermal spray coating layer were analyzed. As the results, the potential of Zn thermal spray coating layer presented driving voltage above 300 mV compare to that of SS400 steel. The passivity characteristic in anodic polarization curve was not presented. It was adequate to as sacrificial anode material. In the surface damage after galvanostatic experiments, uniform corrosion tendency of Zn thermal spray coating layer was clearly observed with acceleration of the dissolution reaction. In conclusion, Zn thermal spray coating could be determined to represent the corrosion protection effect by stable sacrificial anodic cathodic protection method in seawater because it had sufficient driving voltage and uniform corrosion damage tendency for the SS400 steel.

• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1751-1756
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• 2003

An electrochemical study related to the electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazin-5-one(I), 6-methyl-3-thio-1,2,4-triazin-5-one(II), and 2,4-dimetoxy-6-methyl-1,3,5-triazine(III) in dimethylformamide at glassy carbon electrode has been performed. A variety of electrochemical techniques, such as differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry, and coulometry were employed to clarify the mechanism of the electrode process. The compounds I and II with thiol group exhibited similar redox behavior. Both displayed two cathodic peaks, whereas the third compound, III, without thiol group showed only one cathodic peak in the same potential range of the second peak of I and II. The results of this study suggest that in the first step the one electron reduction of thiol produced a disulfide derivative and in the second reduction step the azomethane in the triazine ring was reduced in two electron processes. A reduction mechanism for all three compounds is proposed on this basis. In addition, some numerical constants, such as diffusion constant, transfer coefficient, and rate constant of coupled chemical reaction in the first reduction peak were also reported.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2949-2954
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• 2010

Ionic liquid-functionalized ordered mesoporous silica SBA-15 modified carbon paste electrode (CISPE) was fabricated and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra. The electrochemical behavior of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ at CISPE was studied by differential pulse anodic stripping voltammetry (DPASV). Compared with carbon paste electrode, the stripping peak currents had a significant increase at CISPE. Under the optimized conditions, the detection limits were $8.0{\times}10^{-8}\;M$ ($Cd^{2+}$), $4.0{\times}10^{-8}\;M$ ($Pb^{2+}$), $6.0{\times}10^{-8}\;M$ ($Cu^{2+}$), $1.0{\times}10^{-8}\;M$ ($Hg^{2+}$), respectively. Furthermore, the present method was applied to the determination of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ in water samples and people hair sample.

• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.174-179
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• 2011

The mesoscopic $Sb_2S_3$-sensitized photoelectrochemical solar cells using cobalt redox electrolyte exhibit nonlinear behavior of power conversion efficiency with illuminated sun intensity. From the measurement of bulk diffusion and electrochemical impedance spectroscopy studies, we suggest that the nonlinearity of device performance with illuminated sun intensity is attributed not to the slow bulk diffusion problem of cobalt electrolyte but to the limited mass transport in narrowed pore volume in mesoscopic $TiO_2$ electrode.

• Journal of Electrochemical Science and Technology
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• 제7권4호
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• pp.251-262
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• 2016

The corrosion protection of mild steel in 1M HCl and 0.5M $H_2SO_4$ solutions by ethanol extract of Vernonia amygdalina (VA) was studied using a combination of experimental and computational methods. The obtained results revealed that VA reduced the corrosion of mild steel in both environments and inhibition efficiency increased with VA concentration but decreased with prolonged exposure. Electrochemical results showed that the extract functioned via mixed corrosion inhibiting mechanism by adsorption of some organic constituents of the extract on the metal/acid interface. Findings from infrared spectroscopy and electron microscopy all confirmed that VA retarded mild steel corrosion in both 1M HCl and 0.5M $H_2SO_4$ through an adsorption process. The adsorption behavior of selected constituents of the extract was modeled using density functional theory computations.

• Corrosion Science and Technology
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• 제15권6호
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• pp.311-313
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• 2016

The anodic dissolution behavior of copper and brass in an electrolyte solution of 0.5M NaCl containing 0.5 mM $NaHCO_3$ was investigated by electrochemical impedance spectroscopy. The Nyquist plots of the copper impedance described a small loop in the high-frequency range and a large locus in the low-frequency range. Additionally, the features of the impedance spectrum of the brass were similar to those of the copper. This indicates that the copper-enriched layer formed on the brass surface due to the selective dissolution of the zinc from the surface. In addition, the rest potential and the anodic polarization curve for each sample were measured in order to discuss the selective dissolution of the zinc from the brass surface.

• Corrosion Science and Technology
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• 제15권6호
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• pp.314-319
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• 2016

Reduced activation ferritic-martensitic steels (RAFM) are envisaged in future fusion technology as structural material which will be in direct contact with a flowing liquid lead-lithium melt, serving as breeder material. Aluminium-based coatings had proven their ability to protect the structural material from corrosion attack in flowing Pb-15.7Li and to reduce tritium permeation into the coolant, significantly. Coming from scales produced by hot dipping aluminization (HDA), the development of electrochemical-based processes to produce well-defined aluminium-based coatings on RAFM steels gained increased attention in research during the last years. Two different electrochemical processes are described in this paper: The first one, referred to as ECA, is based on the electrodeposition of aluminium from volatile, metal-organic electrolytes. The other process called ECX is based on ionic liquids. All three processes exhibit specific characteristics, for example in the field of processability, control of coating thicknesses (low activation criteria) and heat treatment behavior. The aim of this article is to compare these different coating processes critically, whereby the focus is on the comparison of ECA and ECX processes. New results for ECX will be presented and occurring development needs for the future will be discussed.