• 한국세라믹학회지
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• 제49권1호
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• pp.78-83
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• 2012

The electrophoretic deposition(EPD) of ZnO nano-sized colloids is investigated by changing the colloid number concentration, applied force, and deposition time. The change of the colloid size in a suspension was examined by the different colloid number concentrations (N = $3.98{\times}10^{15}$, N = $3.98{\times}10^{14}$, and N = $3.98{\times}10^{13}$) with an increase of the deposition time and applied forces. Deposition behavior was investigated by changing the applied fields (from DC 5 V to 50 V) and the deposition time (5 min to 25 min). The surface microstructures of the as-deposited films were investigated by SEM. The dried films were sintered from $850^{\circ}C$ to $1,050^{\circ}C$ for 2 h and then the microstructures were also explored by SEM. The agglomeration rate was enhanced by increasing the colloid number concentration of colloids. Colloid number concentration in a suspension must be rapidly decreased at higher values of the electric field. ZnO nano-sized colloids had the highest zeta potential value of over -28 mV in methanol. A homogeneous microstructure was obtained at colloid number concentration of N = $3.98{\times}10^{13}$, applied DC field of 5 V/cm and 15 min of deposition time at an electrode distance of 1.5 cm. Under these conditions, the deposited films were sintered at $850^{\circ}C$ and $1,050^{\circ}C$ for 2 h. The results show a typical pore-free surface morphology of a uniform thickness of 400 nm under these experimental conditions.

• 전기학회논문지
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• 제58권12호
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• pp.2446-2452
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• 2009

A Ceramic Metal-halide lamp is achieved by adding multiple metals to a basic mercury discharge. Because the vapor pressure of most metals is very much lower than mercury itself, metal-halide salts of the desired metals, having higher vapor pressures, are used to introduce the material into the basic discharge. The metal compounds are usually polyatomic iodides, which vaporize and subsequently dissociate as they diffuse into the bulk plasma. Metals with multiple visible transitions are necessary to achieve high photometric efficiency and good color. Compounds of Sc, Dy, Ho, Tm, Ce, Pr, Yb and Nd are commonly used. The maximum visible efficacy of a Ceramic Metal Halide lamp, under the constant of a white light source, is predicted to be about 450lm/W. This is controlled principally by the chemical fill chosen for a particular lamp. Current these lamps achieve 130lm/W and these life time are the maximum 16,000[hr]. So factors of performance lower are necessary to improve lamp performance. In this paper, we analyzed factors of performance lower by accelerated deterioration test. The lamp was operated with short duration turn-on/turn-off procedure to enhance the effect due to electrode sputtering during lamp ignition. The tested lamp that was operated with a longer turn-on/off(20/20 minutes) showed blackening, changed distance between electrodes and lowered color rendering & color temperature by losses of Dy at 421.18nm, I at 511nm, T1 at 535nm and Na at 588nm compared with the new lamp.

• 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.

• 한국진공학회지
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• 제19권5호
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• pp.331-340
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• 2010

초고주파 다중 중공 음극 방전을 이용한 플라즈마 화학 기상 증착 장치를 3차원 수치 모델링하였다. 기본적인 방전 특성을 파악하기 위하여 알곤 플라즈마를 40 MHz, 100 V, 133.3 Pa (1 Torr)의 조건에 대해서 계산하였다. 6 mm 직경의 홀을 20 mm 간격으로 배열하였고 전극 간격은 10 mm를 가정하였다. 피크 플라즈마 밀도는 홀의 하부 중앙에서 $5{\times}10^{11}#/cm^3$ 였으며 전자 온도는 접지 상태로 가정한 기판과 챔버 벽면 주위에서 가장 높았다. 준안정 상태에 의한 2단 이온화 속도는 전자 충돌에 의한 직접 이온화보다 10배 가량 높았다. 수소에 대한 계산에서는 이온화 이외의 다양한 에너지 소모 경로가 있어서 방전의 국재화가 잘 이루어지지 않았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.389-389
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• 2012

Molybdenum is one of the most important materials used as a back ohmic contact for $Cu(In,Ga)(Se,S)_2$ (CIGS) solar cells because it has good electrical properties as an inert and mechanically durable substrate during the absorber film growth. Sputter deposition is the common deposition process for Mo thin films. Molybdenum thin films were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering technique. The outdiffusion of Na from the SLG through the Mo film to the CIGS based solar cell, also plays an important role in enhancing the device electrical properties and its performance. The structure, surface morphology and electrical characteristics of Mo thin films are generally dependent on deposition parameters such as DC power, pressure, distance between target and substrate, and deposition temperature. The aim of the present study is to show the resistivity of Mo layers, their crystallinity and morphologies, which are influenced by the substrate temperature. The thickness of Mo films is measured by Tencor-P1 profiler. The crystal structures are analyzed using X-ray diffraction (XRD: X'Pert MPD PRO / Philips). The resistivity of Mo thin films was measured by Hall effect measurement system (HMS-3000/0.55T). The surface morphology and grain shape of the films were examined by field emission scanning electron microscopy (FESEM: Hitachi S-4300). The chemical composition of the films was obtained by the energy dispersive X-ray spectroscopy (EDX). Finally the optimum substrate temperature as well as deposition conditions for Mo thin films will be developed.

• 공업화학
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• 제25권4호
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• pp.386-391
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• 2014

본 연구에서는 상압 저온 코로나 방전 플라즈마를 화산암재(스코리아) 분말의 살균에 적용하였다. 스코리아 분말에 Escherichia coli (E. coli) 배양액을 살포하여 균일하게 혼합한 후, 코로나 방전 플라즈마 특성 인자인 방전전력, 방전시간, 주입기체, 전극간격 등의 조건을 변화시키며 E. coli 살균효율을 조사하였다. 실험 결과 상압 저온 코로나 방전 플라즈마는 분말상의 스코리아 살균에 아주 효과적인 것으로 나타났으며, 방전전력 15 W에서 5 min 동안 살균한 결과 E. coli가 99.9% 이상 사멸하였다. 방전전력, 방전시간, 인가전압이 증가할수록 사멸율이 향상되었다. 반응기에 주입되는 기체의 종류에 따른 살균력 실험 결과, 산소 > 모사공기(산소 20%) > 질소 순으로 나타났다. 코로나 방전 플라즈마에 의한 E. coli 살균은 자외선과 활성산화종(산소라디칼, OH라디칼, 오존 등)에 의한 세포막 침식 및 에칭, 그리고 플라즈마 방전 스트리머에 의한 대장균 세포막 파괴로 설명할 수 있다.

• 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.

• 자원리싸이클링
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• 제18권3호
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• pp.62-68
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• 2009

마그네슘 용융염 전해시 적정 조업조건을 확립하고자 자체 설계 제작한 150A급 mono-polar형 전해조를 사용하여 24시간 연속 전해 조업을 수행하였다. $MgCl_2$ 25%, NaCl 55%, $CaCl_2$ 19%, $CaF_2$ 1%의 전해욕 조성으로 전해온도 $720{\sim}740^{\circ}C$, 전해전압 7V, 음극 전류 밀도 $0.7-0.75A/cm^2$, 전극 간격 6cm의 운전조건에서 24시간 연속 조업을 수행하였으며, 전해 전압 및 전류 변화, 전해 욕 조성 변화, 전류 효율 등을 조사하였다. 시험결과 제작한 전해셀의 조업성이 양호하였으며, 순도 99% 이상의 금속 마그네슘을 회수하였고 전류효율 89%를 달성할 수 있었다. 본 연구를 통하여 마그네슘 용융염 전해장치 제작에 필요한 기초자료를 축적할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1699-1701
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• 2000

The dynamic behavior of fatty acid monolayers at the air-water interface was investigated using a displacement current-measuring technique coupled with the so-called Langmuir film technique and also the dipole moment of the acids was determined. The displacement current flowing though a short circuit wan generated only when induced charges on an electrode flowing though suspended in air was changed by monolayer compression. The displacement current measurement was found to be a very sensitive method used for a better understanding of the relationship between the structure and function of the monolayers placed on the water surface and it was also found to be a very useful method for detecting the dynamic motion of molecules in the entire range from the so-called gaseous state to solid state at the same time. In the paper investigate fatty monolayer dynamic state and electric property character. As result. Displacement current generate higher nearly distance electrodel and water surface. Also, Molecule behavior was found pocess active higher thermal.

• 전기전자학회논문지
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• 제19권4호
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• pp.535-540
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• 2015

디지털 X-선 촬영 장치에 응용되는 MSGC형 검출기를 설계 및 제작하였다. 기판의 재질은 실리콘기판과 유리기판을 사용하였으며, 기판위에 증착된 전극물질은 포토리소그래피 공정을 이용하였으며, 크롬을 전극의 재료를 이용하였다. 양전극의 폭은 $10{\mu}m$, 음전극의 폭은 $290{\mu}m$로 각각 제작하였다. 양전극과 음전극 사이의 거리는 $100{\mu}m$ 이고, 검출기의 유효영역은 $50{\times}50mm^2$로 설계하였다. 그리고 양전극의 수는 80개로 하였고, 양전극의 전압이 600 Volt 이상 인가한 경우 양전극과 음전극 부분이 방전되어 끊어진 현상을 확인하였다. 결과적으로 검출기체인 Ar(90%) + $CH_4$(10%) 기체 하에서 X-선관의 전압은 42 kV, 최대전류 1 mA까지 인가하여 연구를 수행하였다.