• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1130-1132
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• 2009

We propose a novel way for enhancement of efficiency on a quasi solid-state dye-sensitized solar cell (DSSC). It contained gel type electrolyte mixing the liquid crystal (LC) of specific concentration and applied voltage for alignment of the LC. Aligned LC is supported charge transfer inside electrolyte and efficiency is increased in DSSC. We made a quasi solid-state DSSC which applied DC voltage or not and have measured the power conversion efficiency (PCE) and the fill factor. From measurement, we obtain high performances in case of cell applied voltage compare to reference cell.

• 센서학회지
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• 제13권1호
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• pp.72-77
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• 2004

In this paper, we fabricated an apparatus of the electro-chemical discharge drilling for boring narrow through-hole into a glass. In the electrolyte, electro-chemical discharge creates high temperature condition by the electro-discharge energy. Therefore, glass are removed by the accelerated chemical reaction with glasses and chemicals in the high temperature condition. For optimization of the electro-chemical discharge drilling, the process condition was studied experimentally as a function of the electrolyte concentration, supply voltage and process time. The optimum condition was from DC25V to DC30V of applied voltage, 35 wt% NaOH solution.

• 한국정밀공학회지
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• 제21권6호
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• pp.172-178
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• 2004

Tungsten carbide microshaft can be used as various micro-tools for MEMS because it has high hardness and high rigidity. In this study, experiments are performed to produce tungsten carbide micro-shaft using electrochemical etching. H$_2$SO$_4$ solution is used as electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and machining voltage satisfying uniform shape, good surface quality, and high MRR of workpiece are experimentally found. By controlling the various machining parameters, a straight micro-shaft with 5 ${\mu}{\textrm}{m}$ diameter, 3 mm length, and 0.2$^{\circ}$taper angle was obtained.

• 열처리공학회지
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• 제22권4호
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• pp.223-227
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• 2009

The feasibility of plasma electrolytic polishing technology of stainless steel was examined. The results show that austenitic stainless steel can be polished clearly using potentiostatic regimes with various concentration of ammonium sulfate ($(NH_4)_2SO_4$) solution above certain initial temperature. The equipment and deposition produces for polishing process are described and the effect of processing parameters on the characterizations polished-samples has been investigated.

• 한국지하수토양환경학회지:지하수토양환경
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• 제8권3호
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• pp.56-60
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• 2003

전기분해에 의한 부상현상을 이용하여 유류로 오염된 토양 세정 후 발생되는 유출수 중 유분 등을 분리하기 위한 적정 운전조건을 찾고자 하였다. 전기분해 반응조(200${\times}$10${\times}$15cm)를 이용하여 혼합계면활성제($POE_5$ : $POE_{14} $, 1:1) 1%용액에 디젤을 1,000 mg/L 농도로 용해시켜 실험하였다. 양극에는 티타늄 코팅전극, 음극으로는 스테인레스 스틸전극을 이용하였다. 반응시간은 62분(반응 :60분, 부상시간 :2분)이었으며 전압은 6V였다. 전해질 첨가에 의한 영향을 알아보기 위하여 실험한 결과, 전해질을 첨가하였을 경우 첨가하지 않았을 때보다 40% 정도의 효율이 증가하였다. 적정 전해질, 주입농도 및 반응시간을 알아보기 위하여 1N NaCl과 NaOH의 농도를 변화시켜 가면서 실험하였다. NaCl의 경우 더 좋은 효율을 나타내었다. 전해질의 농도는 0.2-1.0%의 농도범위에서 NaCl와 NaOH 모두 농도에 따라 순차적으로 효율이 증가하였다. 두 전해질 모두 0.4-1.0% 농도 범위에서 평형에 도달하는 시간은 20분으로 나타났다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.149-149
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• 2017

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the seawater upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification showed a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.153-153
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• 2016

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the sea water upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Afterward, the irregular oxide film that was created in the first step surface modification was removed. For the second step surface modification process (identical to the step 1), etching was performed using mixture of chromic acid (1.8 wt.%) and phosphoric acid (6 wt.%) at $60^{\circ}C$ temperature for 30 minutes. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification presented a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.527-530
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• 2013

이 논문은 콜로이드 입자가 기름-물 사이의 계면으로 흡착될 때 필수적으로 존재하는 정전기적 반발력에 대한 실험적, 이론적 연구이다. 광집게(optical laser tweezers)와 피에조(piezo controller)를 사용하여, 개별 입자를 트랩(trap)한 후, 계면으로 강제 전이시킨다. 이때 수용액이 전해질을 포함한 경우에만, 입자가 계면으로 전이되며, 포함하지 않을 경우에는 흡착이 일어나지 않는다. 이러한 현상을 근본적으로 이해하기 위해, 광학 트랩핑 힘(optical trapping force)과 입자와 계면 사이에 존재하는 정전기적 분리압력(electrostatic disjoining pressure)를 정량적으로 계산하였다. 이를 바탕으로, 입자가 계면으로 흡착될 때, 그들 사이에는 필연적으로 문턱 에너지(threshold energy)가 존재함을 밝혀냈다. 콜로이드 입자가 에멀젼(emulsions)이나 거품(foams)등 두 개 이상의 섞이지 않는 유체계면을 안정화 시키는 "콜로이드 계면 활성제(colloid surfactants)" 역할을 한다는 사실을 고려했을 때, 본 연구는 이러한 입자의 흡착 현상을 근본적으로 이해하는데 있어서 중요한 지식을 제공한다.

• Elastomers and Composites
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• 제39권1호
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• pp.36-41
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• 2004

Poly(ethylene oxide)(PEO)와 epoxy diacrylate(EDA) 및 금속염인 LiClO_4$를 블렌드하고 자외선 가교시킴으로써 이온전도특성을 나타내는 고체 전해질을 제조하고, 제조된 전해질의 이온 전도도를 블렌드조성 염농도 및 온도 변화에 따가 측정하였다. PEO/EDA의 조성비가 70/30 wt%이고 ethylene $oxide/Li^+$의 몰비가 10인 전해질이 $25^{\circ}C$에서 $1.2{\times}10^{-5} S/cm$에 달하는 높은 이온전도도를 나타내었다. 제조된 전해질 필름은 투명하였으며 고무와 같은 탄성을 나타내었다. DSC, XRD 및 편광현미경을 이용한 모폴로지 분석으로부터 에폭시 사슬이 PEO의 결정화를 억제함으로써 완전히 무정형인 블렌드를 제조할 수 있음을 확인할 수 있었다.

• 한국수소및신에너지학회논문집
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• 제32권4호
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• pp.245-255
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• 2021

Various studies about metallic bipolar plates have been conducted to improve fuel cell performance through flow field design optimization. These research works have been mainly focused on fuel cells for vehicle, but not fuel cells for building. In order to reduce the price and volume of fuel cell stacks for building, it is necessary to apply a metallic flow field, In this study, for a metallic flow field applied to a fuel cell for building, the effect of a change in the flow field shape on the performance of a polymer electrolyte membrane fuel cell was confirmed using a model and experiments with a down-sizing single cell. As a result, the flow field using a metal foam outperforms the channel type flow field because it has higher internal differential pressure and higher reactants velocity in gas diffusion layer, resulting in higher water removal and higher oxygen concentration in the catalyst layer than the channel type flow field. This study is expected to contribute to providing basic data for selecting the optimal flow field for the full stack of polymer electrolyte membrane fuel cells for buildings.