• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.119-120
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• 2008

In this paper, viologen derivative is used as charge transfer material to develop sensors for detecting the organic pollutants which are the main reason of harbor pollution. We fabricated self-assembled monolayers of viologen derivative on gold electrode of QCM and investigated an electrochemical behavior property. We also determined electrochemical sensing property about environmental pollution materials such as bezene, phosphate and surfactant through quantitative and qualitative analysis of charge transfer using intrinsic property of viologen derivative by temperature and concentration change. From the achieved results, we can apply and develope the detecting sensors for harbor pollutants.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.314-319
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• 2001

Most parts of facilities in domestic petroleum plants and power plants are needed to be abandoned, repaired or replaced, because in Korea they were built in the 1960s and, they have been used under severe conditions and exposed corrosive environments. 2.25Cr- lMo steels have excellent high-temperature mechanical properties. Therefore, the material have been widely used as heat exchanger tubes, boiler headers and its tubes in such industries. But, those microstructural evolutions in high temperature such as precipitation and carbide coarsening give a reason to degrade the material. Especially, in case of this material, carbides induced embrittlement(CIE) is the primary reason for degrading mechanical properties at over 50$0^{\circ}C$. In this paper, we introduce a electrochemical polarization method for detecting CIE quantitatively.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1365-1366
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• 2007

Cobalt oxide was composite with MWNT to attain cycle stable by chemical method. We have been considered CoOx is the ideal material for high energy density electrochemical capacitor due to pseudo capacitor reaction. In this study we found that decrease in resistance due to composite MWNT. Also CoOx/MWNT composite material have resulted larger capacitance and exhibits better electrochemical behavior. The structural feature was investigated by using SEM. The CoOx/MWNT composite is not only a promising ultracapacitor material for energy storages but also has a good possibility because of its great capacitive properties, simple preparation and low cost.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.602-606
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• 2003

Silicon has been developed as an alternate anode material for lithium secondary batteries. A simple approach to improve the electrical contact of silicon powder has described. Carbon-coated and silver-coated silicon have been prepared by chemical vapor deposition and electroless plating respectively. Assembled cells, which consisted of surface modified silicon, lithium foil and $Li^+$ contained organic electrolyte, have been studied using electrochemical methods. Carbon-coated silicon was improved in the electrochemical performance such as reversibility and resistance compared to surface-unmodified silicon.

• 한국전기화학회:학술대회논문집
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• 2001.04a
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• pp.42-42
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• 2001

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.139-139
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• 2010

LSM is widely used as a cathode material in SOFC, because of its high electrochemical activity, good stability and compatibility with YSZ electrolyte at high temperature. However, LSM in traditional cathode materials will not generate a satisfactory performance at intermediate temperature. In order to reduce the polarization resistance of cell with the operating temperature of SOFC system, the cathode material of LSCF is one of the most suitable electrode materials because of its high mixed ionic and electronic conductivity. In this report, cathode material, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ powder for intermediate temperature SOFC was synthesized by Pechini method using the starting materials such as nitrate of La, Sr, Co and Fe including ethylene glycol, etc. As a result, the synthesized powder that calcined above $700^{\circ}C$ exhibits successfully perovskite structure, indicating phase-pure of LSCF. Moreover, the particle size, surface area, crystal structure and morphology of the synthesized oxide powders were characterized by SEM, XRD, and BET, etc. In order to evaluate the electrochemical performance for the synthesized powder, slury mixture using the synthesized cathode material was coated by screen-printing process on the anode-supported electrolyte which was prepared by a tape casting method and co-sintering. Finally, electrochemical studies of the SOFC unit cell, including measurements such as power density and impedance, were performed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.727-734
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• 2017

The electrochemical conversion of $CO_2$ is one of the methods for reducing $CO_2$. Four materials (Ag, Ni, Pt, and Ir) were selected as the electrodes. The electrochemical conversion was performed under a cell voltage of 4.0 V at $600^{\circ}C$. The amounts of $CO_2$ reduction and carbon production were at the highest for Ag, followed by, Pt, Ni, and then Ir. The produced carbon samples were analyzed by thermogravimetric analysis and XRD. The thermogravimetric analysis results indicated that all the carbon produced at each electrode exhibited similar thermal reactivity. The XRD results showed that the crystallization of carbon was different depending on the electrode utilized. Although electrochemical conversion was the highest for the Ag electrode, a loss of material accompanied it. Therefore, for this study, the optimal electrode is Pt, taking into account reactivity and material losses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.300-312
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• 1993

The material deterioration of service-exposed boiler tube steels in fossil power plant was evaluated by using the electrochemical technique namely, modified electrochemical potentiokinetic reactivation(EPR). It was focused that the passivation of Mo$_{6}$C carbide which governs the mechanical properties of Mo alloyed steels did not occur even in the passivity region of steel in sodium molybdate solution and the reactivation peak current (Ip) observed as the result of non-passivation indicating the precipitation of Mo$_{6}$C carbides. To obtain the optimal test conditions for the field test by using the specially designed electrochemical cell, the effects of scan rate, the surface roughness and the pH of electrolyte on Ip value were also investigated. Furthermore, the change of mechanical properties occurred during the long time exposure at high temperature was evlauated quantitatively by small punch(SP) tests and micro hardness test taking account of the metallurgical changes. It is known that reactivation peak current (Ip) has a good relationship with Larson-Miller Parameter(LMP) which represents the information about material deterioration occurred at high temperature environment. In addition it was possible to estimate the ductile-brittle transition temperature (DBTT) by means of the SP test. The Sp test could be, therefore, suggested as a reliable test method for evaluating the material degradation of boiler tube steels. From the good correaltion between the SP DBTT and Ip values shown in this study, it was knows that the change of mechanical properties could be evaluated non-destructively by measurring only Ip values.ues.

• Environmental Engineering Research
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• v.22 no.2
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• pp.186-192
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• 2017

The carbon paste electrode (CPE) was modified with the pristine bentonite and hybrid material (HDTMA-modified bentonite). The modified-CPEs are then employed as working electrode in an electrochemical detection of As(V) from aqueous solutions using the cyclic voltammetric measurements. Cyclic voltammograms revealed that As(V) showed reversible behavior onto the working electrode. The hybrid material-modified carbon paste electrode showed significantly enhanced electrochemical signal which was then utilized in the low level detection of As(V). Moreover, the studies were conducted at neutral pH conditions. The electrochemical studies were conducted with scan rates (20 to 200 mV/s) to deduce the mechanism of redox processes involved at the electrode surface. The anodic current was linearly increased, increasing the concentration of As(V) from 5.0 to $35.0{\mu}g/g$ using the hybrid material-modified electrode. This provided fairly a good calibration line for As(V) detection. The presence of varied concentrations of As(III) in the determination of total arsenic was studied. The influence of several cations and anions viz., Cu(II), Mn(II), Zn(II), Pb(II), Cd(II), Fe(III), $Cl^-$, $NO_3{^-}$, $PO_4{^{3-}}$, EDTA and glycine in the detection of As(V) from aqueous solution was also studied. Further, in an attempt to simulate the real matrix analysis, the tap water sample was spiked with As(V) and subjected for As(V) detection using the modified-CPE.

• Journal of Powder Materials
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• v.26 no.1
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• pp.49-57
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• 2019

Layered $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode materials single- and dual-doped by the rare-earth elements Ce and Nd are successfully fabricated by using a coprecipitation-assisted solid-phase method. For comparison purposes, non-doping pristine $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode material is also prepared using the same method. The crystal structure, morphology, and electrochemical performances are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, and electrochemical techniques. The XRD data demonstrates that all prepared samples maintain a typical ${\alpha}-NaFeO_2$-layered structure with the R-3m space group, and that the doped samples with Ce and/or Nd have lower cation mixing than that of pristine samples without doping. The results of SEM and EDS show that doped elements are uniformly distributed in all samples. The electrochemical performances of all doped samples are better than those of pristine samples without doping. In addition, the Ce/Nd dual-doped cathode material shows the best cycling performance and the least capacity loss. At a 10 C-rate, the electrodes of Ce/Nd dual-doped cathode material exhibit good capacity retention of 72.7, 58.5, and 45.2% after 100, 200, and 300 cycles, respectively, compared to those of pristine samples without doping (24.4, 11.1, and 8.0%).