• E2M - 전기 전자와 첨단 소재
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• 제7권1호
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• pp.25-31
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• 1994

Properties of oxynitride films reoxidized by $N_2{O}$ gas after thermal oxidation and $N_2{O}$ oxide films directly oxidized by using $N_2{O}$ gas on the bare silicon wafer have been studied. From the AES analysis, nitrogen pile-up at the interface of Si/oxynitride and Si/$N_2{O}$ oxide has observed. $N_2{O}$ oxide and oxynitride films have the self-limited characteristics. Therefore, it will be possible to obtain ultra-thin films. Nitrogen pile-up at the interfaces of Si/oxynitride and Si/$N_2{O}$ oxide strengthens film structure and improves dielectric reliability. Although fixed charge densities and interface trap densities of N20 oxide and oxynitride films have somewhat higher than those of thermal $SiO_2{O}$, $N_2{O}$ oxide and oxynitride films showed improved I-V characteristics and constant current stress.

• 한국표면공학회지
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• 제51권6호
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• pp.415-420
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• 2018

The possibility of an improvement in heat dissipation performance of aluminum alloy heat sink for shipboard LED luminaries through plasma electrolytic oxidation (PEO) was investigated. Four different PEO coatings were produced on aluminum alloy 5052 in silicate based alkaline solution by varying current density ($50{\sim}200mA/cm^2$). On voltage-time response curves, three stages were clearly distinguished at all current densities, namely an initial linear increase, slowdown of increase rate, and steady state(constant voltage). It was found that the increase in current density caused the breakdown voltage to increase. Two different surface morphologies - coralline porous structure and pancake structure - were confirmed by SEM examination. The coralline porous structure was predominant in the coatings produced at lower current densities (50 and $100mA/cm^2$) while under high current densities(150 and $200mA/cm^2$) the pancake structure became dominant. The coating thickness was measured and found to be in a range between about $13{\mu}m$ and $44{\mu}m$, showing increasing thickness with increasing current density. As a result, $100mA/cm^2$ was proposed as an effective process parameter to improve the heat dissipation performance of aluminum alloy heat sink, which could lower the LED operating temperature by about 30%.

• Corrosion Science and Technology
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• 제12권6호
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• pp.288-294
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• 2013

When the automotive body enters an electrocoating tank while applying an electric current, its steel surface is exposed to a very low induced current. Consequently, surface defects of coating may arise if the steel surface has lack of electric uniformity due to local defects such as local oxide. In this study, we investigated the preceding assessment methods to evaluate steel susceptibility of the low induced current during electrocoating before mass production. Prior to general electrocoating, we applied low constant voltage such as 3V or low constant current densities such as $0.35mA/cm^2$ and $0.50mA/cm^2$. In result, we confirmed that such methods were efficient for assessing steel susceptibility of low induce current during electrocoating.

• 대한기계학회논문집B
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• 제32권12호
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• pp.963-969
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• 2008

The performance behavior of solid oxide fuel cell using $H_2$ and CO as fuels was investigated. The power densities and impedance results showed a little variation as the ratio of $H_2$ and CO changed. However, when the pure CO was used as a fuel, area specific resistance (ASR), especially low frequency region, was increased. This might be due to carbon deposition on anode. The maximum power density was 60% lower using CO than using $H_2$. Carbon deposition reduced after constant current was applied. The SOFC performance was recovered from the carbon deposition after applying constant current during 100h.

• Journal of Advanced Marine Engineering and Technology
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• 제29권1호
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• pp.107-115
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• 2005

The effects on the formation of anodic oxide films on Mg-Al alloy (AZ91) in 1M-NaOH solution was investigated using parameters of current density and time during anodizing The general tendency has been confirmed that the increase of anodizing time improves the corrosion resistance. It is considered that the formation of anodic oxide film was increased by increasing the applied current and the anodizing time to generate active dissolution reaction In anodizing at constant current density. passivity potentials shifted to noble direction with increasing current densities. It was confirmed that oxygen quantify in anodic oxide films increased with anodizing time. The compact films above 4 $mA/cm^2$ were formed with the shape of an island in grooves at early stage and then grew with combination of the islands

• Corrosion Science and Technology
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• 제8권4호
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• pp.143-147
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• 2009

In biomedical implants and dental fields, titanium has been widely utilized for excellent corrosion resistance and biocompatibility. However, Ti and its alloys are nonbioactive after being implanted in bone. In this study, for the purpose of improvement in biocompatibility the anodic $TiO_2$ layer on Ti-xNb alloys were fabricated by electrochemical method in phosphate solution, and the effect of Nb content on the pore size, the morphology and crystallinity of Ti oxide layer formed by the anodic oxidation method was investigated. The Ti containing Nb up to 3 wt%, 20 wt% and 40 wt% were melted by using a vacuum furnace. The sample were cut, polished, and homogenized for 24 hr at $1050^{\circ}C$ for surface roughness test and anodizing. Titanium anodic layer was formed on the specimen surface in an electrolytic solution of 1 M phosphoric acid at constant current densities ($30mA/cm^2$) by anodizing method. Microstructural morphology, crystallinity, composition, and surface roughness of oxide layer were observed by FE-SEM, XRD, EDS, and roughness tester, respectively. The structure of alloy was changed from $\alpha$-phase to $\beta$-phase with increase of Nb content. From XRD results, the structure of $TiO_2$ formed on the Ti-xNb surface was anatase, and no peaks of $Nb_2O_5$ or other Nb oxide were detected suggesting that Nb atoms are dispersed in $TiO_2$-based solid solution. Surface roughness test and SEM results, pore size formed on surface and surface roughness decreased as Nb content increased. From the line analysis results, intensity of Ti peak was high in the center of pore, whereas, intensity of O peak was high in the outside of pore center.

• 전기학회논문지P
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• 제51권2호
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• pp.77-81
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• 2002

In this study, PZT thin films were fabricated using sol-gel processing onto Si/$SiO_2$/Ti/Pt substrates. PZT sol with different Zr/Ti ratio(20/80, 30/70, 40/60, 52/48) were prepared, respectively. The films were fabricated by using the spin-coating method on substrates. The films were heat treated at $450^{\circ}C$, $650^{\circ}C$ by rapid thermal annealing(RTA). The preferred orientation of the PZT thin films were observed by X-ray diffraction(XRD), and Scanning electron microscopy(SEM). All of the resulting PZT thin films were crystallized with perovskite phase. The fine crystallinity of the films were fabricated. Also, we found that the ferroelectric properties from the dielectric constant of the PZT thin films were over 600 degrees, P-E hysteresis constant. And the leakage current densities of films were lower than $10^{-8}A/cm^2$. It is concluded that the PZT thin films by sol-gel process to be convinced of application for ferroelectric memory device.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.261-268
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• 2022

In this study, electrochemical treatment of urban wastewater with electrical conductivity of 1000 μS cm^-1 and chemical oxygen demand of 250 mg L^-1 was investigated using the variables of initial pH value, current density and flow rate. Electrocoagulation was used, in which aluminum and stainless steel were selected, as the electrochemical treatment process. The electrocoagulation process was operated in continuous mode. The data obtained in experimental studies show that the best COD removal efficiency occurred in experiments where the initial pH value was 6. The increase in current density from 5 A to 15 A decreased the removal efficiency from 79 to 67%. The increase in flow rate under constant current density also reduced the efficiency of removal as expected. In experiments in which current density and flow rate were examined together, the increase in flow rate allowed the application of higher current densities. This situation led to considerable reductions in energy consumption values, even if the COD removal efficiency did not significantly increase. The high COD removal obtained with the use of high flow rate and high current density indicates that the electrocoagulation process can be used for high flow rate municipal wastewater treatment.

• 전기화학회지
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• 제19권3호
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• pp.114-121
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• 2016

본 연구에서는 리튬이온전지의 충방전시 발생하는 발열특성을 CFD 모델링하고, 발열에 따른 충방전 특성을 해석하였다. 리튬이온전지는 직교 파우치형 구조로서 두께방향으로의 1차원계로 설정하여, 전류밀도 방정식, 열 및 물질전달 지배방정식을 도입하였다. Cut-off 전압이 3 V에서 충방전 전류밀도가 1C($17.5A/m^2$), 3C($52.5A/m^2$) 와 5C($87.5A/m^2$)에 대하여, 298K의 등온계와 충방전 전류밀도 별 발열계로 각각 설정하였다. 등온계와 발열계에서 모두 충방전 전류밀도가 높을수록 전지의 용량은 감소되는 것으로 나타났다. 등온계에 비하여 발열계에서 충방전 시간이 증가하였으며, 이는 발열에 의한 온도의 증가로 인해 전극의 평형전위가 감소하고, 리튬이온의 확산계수가 증가하기 때문인 것으로 고려된다. 또한, 리튬이온전지의 충전과 방전에 의한 열 발생 영향을 제어하기 위한 냉각효과를 분석하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.198-199
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• 2006

$SrTa_2O_6$(STA) thin films were fabricated by sol-gel method. The films annealed below $700^{\circ}C$, showed amorphous phase and crystallization phase was observed after annealing over $800^{\circ}C$. From high frequency capacitance-voltage measurements, 24nm thick STA thin film annealed at $900^{\circ}C$, has an EOT of 5.7nm and a dielectric constant of 16. Leakage current characteristics were improved by the insertion of chemical oxide between STA and Si. Leakage current densities are around $3.5{\times}10^{-7}A/cm^2$ at 5V for the structure inserted chemical oxide but $1.4{\times}10^{-6}A/cm^2$ at 5V without chemical oxide.