• Journal of Microbiology and Biotechnology
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• v.19 no.7
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• pp.666-674
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• 2009

An electrochemical bioreactor (ECB) composed of a cathode compartment and an air anode was used in this study to characterize the ethanol fermentation of Zymomonas mobilis. The cathode and air anode were constructed of modified graphite felt with neutral red (NR) and a modified porous carbon plate with cellulose acetate and porous ceramic membrane, respectively. The air anode operates as a catalyst to generate protons and electrons from water. The growth and ethanol production of Z. mobilis were 50% higher in the ECB than were observed under anoxic nitrogen conditions. Ethanol production by growing cells and the crude enzyme of Z. mobilis were significantly lower under aerobic conditions than under other conditions. The growing cells and crude enzyme of Z. mobilis did not catalyze ethanol production from pyruvate and acetaldehyde. The membrane fraction of crude enzyme catalyzed ethanol production from glucose, but the soluble fraction did not. NADH was oxidized to $NAD^+$in association with $H_2O_2$reduction, via the catalysis of crude enzyme. Our results suggested that NADH/$NAD^+$balance may be a critical factor for ethanol production from glucose in the metabolism of Z. mobilis, and that the metabolic activity of both growing cells and crude enzyme for ethanol fermentation may be induced in the presence of glucose.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.211-218
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• 2004

The objective of this study is to enhance the ultimate bearing capacity of piles embedded in marine clay by electrokinetic(EK). The focus of improvement is at interlace between soil and pile. A series laboratory test was performed in EK cell. In each of test, the pile in the centre as anode is surrounded by cathode and it was installed in the vicinity of pile with triangular layout. The pile was made by stainless and embedded with 30cm of depth. Afterward, the DC voltage was applied to electrode over period of time. It caused flowing water from anode to cathode, thus the soil in the center of box has higher bearing capacity value than in the side of box has. It is shown by increasing of un-drained shear strength(Cu) near the pile and also ultimate bearing capacity of pile increase after EK treatment. In the future work, the continuous of this study is finding the effective DC voltage and makes EK treatment more applicable in the field.

• Journal of Hydrogen and New Energy
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• v.23 no.1
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• pp.8-18
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• 2012

This paper presents a three-dimensional, transient cold-start polymer electrolyte fuel cell (PEFC) model to numerically evaluate the effects of membrane electrode assembly (MEA) design and cell location in a PEFC stack on PEFC cold start behaviors. The cold-start simulations show that the end cell experiences significant heat loss to the sub-freezing ambient and thus finally cold-start failure due to considerable ice filling in the cathode catalyst layer. On the other hand, the middle cells in the stack successfully start from $-30^{\circ}C$ sub-freezing temperature due to rapid cell temperature rise owing to the efficient use of waste heat generated during the cold-start. In addition, the simulation results clearly indicate that the cathode catalyst layer (CL) composition and thickness have an substantial influence on PEFC cold-start behaviors while membrane thickness has limited effect mainly due to inefficient water absorption and transport capability at subzero temperatures.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.250-254
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• 1999

Synthesis of the spinel $LiMn_2O_4$ by emulsion method was investigated. $LiOH.H_2O \;and \;Mn(NO_3)_2.6H_2O$ were used as starting materials to prepare mixed aqueous solution (0.5 mol/$\ell$ for the $LiMn_2O_4$). Kerosene, paraffin oil and span 80 were used for organic phase. The aqueous solutioin and organic phase were mixed in the ratio of 2:1 and emulsified at the speed of 4000 rpm for 5 min. The prepared emulsions were dropped into the petroleum heated at $170^{\circ}C$ to evaporate water in the silicon oil bath, dried at $120^{\circ}C$ in the oven the remove petroleum and calcined at temperature ranges from 600 to $900^{\circ}C$ for 48 hrs. The characteristics of powders were investigated by XRD, SEM, BET and electrochemical properties of synthesized cathode materials were measured with Galvanostatic system. $Li_{1.05}Mn_2O_4$ calcined at $800^{\circ}C$ for 48 hrs showed initial discharge capacity of 125.9mAH/g.

• Advances in Energy Research
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• v.2 no.1
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• pp.21-31
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• 2014

The use of a microporous membrane along with Au/C catalyst for direct glycerol alkaline fuel cell was investigated. In comparison with Nafion 112, the microporous Celgard 3401 membrane provides a better cell performance due to the lower ionic resistance as confirmed by impedance spectra. The single cell using Au/C as anode catalyst prepared by using PVA protection techniques provided a higher maximum power density than the single cell with commercial PtRu/C at $18.65mW\;cm^{-2}$ The short-term current decay studies show a better stability of Au/C single cell. The higher activity of Au/C over PtRu/C was owing to the lower activation loss of Awe. The magnitude of current decay indicates a low problem of glycerol crossover from anode to cathode side. The similar performance of single cell with and without humudification at cathode points out an adequate transport of water through the microporous membrane.

• Advances in environmental research
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• v.6 no.2
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• pp.147-158
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• 2017

This paper represents a set of experimental tests on remediation of nickel-contaminated kaolin by Electrokinetic method. For this purpose, we conducted unenhanced and EDTA-enhanced Electrokinetic tests in one, three, and five days of treatment. In unenhanced tests, we used deionized water as an electrolyte in the anode and the cathode compartments. In the EDTA-enhance tests, we used ethylenediaaminetetra acetic acid 0.1 Molar in the cathode and sodium hydroxide 0.1 Molar in the anode. The average nickel removal for unenhanced tests after three and five days of treatment was 19 and 23 percent, respectively. High buffer capacity of the soil is responsible for low removal efficiency in the unenhanced tests, which maintained pH close to the initial amount that restrained nickel as an adsorbed or precipitated forms. The average nickel removal for EDTA-unenhanced tests after three and five days of treatment was 22 and 12 percent, respectively. Lower ionic mobility of EDTA-Ni complex in comparison with $Ni^{+2}$, which is the main transportation mechanism for this complex, could be responsible for less removal efficiency in EDTA-enhanced test.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.35-38
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• 2007

The comparisons between measured performance of lab-scale PEMFC and calculation were conducted to understand the detail phenomena of PEMFC for the various inlet oxygen humidity of cathode side. Experiments were performed at $65^{\circ}C$ operation temperature and different inlet humidity conditions such as 40%, 60% and 80%. We used the MEA manufactured by oneself which include $Nafion^{(R)}$ 112 membrane, Nafion solution 20%, and carbon paper(E-TEK). As a result of this experiment, cell performance was getting higher by increasing inlet humidity condition at cathode side because ion conductivity of electrolyte membrane is increased. A 3D CFD simulation model of PEMFC was developed using commercially available CFD code that is one of the STAR-CD module, es-pemfc under same operating conditions. Model calculations results were compared with experimental ones on the polarization curves and calculation results are in good agreement with the experimental ones. Local water distribution and current density inside PEMFC are discussed in detail.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.147-151
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• 2007

A serpentine channel geometry often used in a polymer electrolyte membrane fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with relatively high aspect ratio active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compression conditions. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds to that of dropwise condensation in cathode channels.

• Membrane and Water Treatment
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• v.9 no.3
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• pp.189-194
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• 2018

Electrochemical reduction of nitrate was studied using Zn, Cu and (Ir+Ru)-Ti cathodes and Pt/Ti anode in a cell divided by an ion exchange membrane. During electrolysis, effects of the different cathode types on operating parameters (i.e., voltage, temperature and pH), nitrate removal efficiency and by-products (i.e., nitrite and ammonia) formation were investigated. Ammonia oxidation rate in the presence of NaCl was also determined using the different ratios of hypochlorous acid to ammonia. The operating parameter values were similar for all types of cathode materials and were maintained relatively constant. Nitrate was well reduced and converted mostly to ammonia using Zn and Cu cathodes. Ammonia, produced as a by-product of nitrate reduction, was oxidized in the presence of NaCl in the electrochemical process and the oxidation performance was enhanced upon increasing the hypochlorous acid-to-ammonia ratio to 1.09:1. Zn and Cu cathodes promoted the nitrate reduction to ammonia and the produced ammonia was finally removed from solution by reacting with hypochlorite ions. Using Zn or Cu cathodes, instead of noble metal cathodes, in the electrochemical process can be an alternative technology for nitrate-containing wastewater treatment.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.70-70
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• 2017

TSV(through silicon via)는 긴 종횡비를 갖는 패턴에 Cu, Ta, Ti을 높은 conformality를 갖도록 증착하는 공정이다. Magnetron cathode의 자석 배열 설계는 target 물질 종류에 따라서 multitrack, water drop type등이 있으며 target과 substrate 사이의 공간에 플라즈마를 형성시켜서 기판에 이온 입사량을 늘린 후 기판 바이어스를 이용하여 이온 충돌, re-sputtering을 통한 재증착 과정을 통해 치밀한 금속 박막을 연속적으로 형성할 수 있도록 하는 것이 목적이다. 또한 sputter가 사용되고 있는 분야에 효율을 증대시키고, 증착되는 막의 품질향상을 위해 UBMS를 사용하고 있으며, 산업에 사용되어 지는 300 mm wafer용 시스템은 제작비가 약 10억 원 정도 소요되며 다양한 테스트를 진행하기 위해선 많은 비용이 소요된다. 따라서 비용과 소요시간을 줄여 다양한 테스트를 위해 소규모 플라즈마 시스템을 설계하게 되었다. 61 l/sec 터보 분자 펌프와 다이아프램 펌프를 기초로한 TMP station에 2.75 인치 CF flange가 장착된 6 way cross를 main 챔버로 활용하고, 작은 size의 unbalanced magnetron cathode를 제작, 장착한 다음 6 way cross 주변에 전자석을 적절히 배치하여 300 mm wafer system에서와 동일한 물리적 현상을 테스트 할 수 있도록 하였다. Fig1. (a) UBMS system의 사진을 나타내었고, (b)에는 6 way cross 내부에 발생된 플라즈마의 형상을 나타내었다. 전원 장치는 Advanced Energy사의 MDX-1.5K DC power supply를 사용하였고, 방전 전압 - 전류 관계의 가스 압력에 따른 plasma 현상과 magnetron 배율에 따른 plasma 현상 그리고 전자석에 의한 영향을 주로 관찰 하였다.