• Title, Summary, Keyword: 양극분극

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Oxygen Reduction Mechanism and Electrode Properties of (La,Sr)$MnO_3$-YSZ Composite Cathode for Solid Oxide Fuel Cell (Part I: Oxygen Reduction Mechanism) (고체산화물 연료전지용 (La,Sr)$MnO_3$-YSZ 복합체 양극의 산소환원 반응기구 및 전극 특성 (Part I: 산소환원 반응기구))

  • 김재동;김구대;이기태
    • Journal of the Korean Ceramic Society
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    • v.38 no.1
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    • pp.84-92
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    • 2001
  • (La,Sr)MnO$_3$(LSM)-YSZ 복합체 양극의 산소환원 반응기구에 대해 고찰하였다. YSZ를 첨가함에 따라 복합체 양극의 ohmic 저항이 증가하고, 분극 저항은 YSZ를 40 wt%~50 wt% 혼합하였을 때 최소값을 나타내었다. 또한 LSM-YSZ 복합체 양극의 산소환원 반응기구는 1가 산소이온의 표면확산과 산소이온전달반응에 의해서 지배됨을 알 수 있었다. 임피던스 분석 결과에 따르면 고주파수 영역에서 나타나는 반원은 산소이온전달반응으로 산소분압 의존성이 거의 없고, YSZ가 40 wt% 첨가되었을 때 최소값을 나타내었다. 중간주파수 영역에서 나타나는 반원은 1가 산소이온의 표면확산반응으로 산소분압 의존성은 약 1/4이고, YSZ가 40~50 wt% 첨가되었을 때 최소값을 나타냈다. 한편, 저주파수 영역에 나타나는 반원은 가스확산반응으로 산소분압 의존성이 1이고, 온도에 따른 의존성이 거의 없었다.

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Studies on Improved Carbon Cathode Performance in High Rate $Li/SOCl_2$ Cell (고율 방전용 $Li/SOCl_2$ 전지의 카본 양극 개선에 관한 연구)

  • 최정자;조성백;박희숙
    • Journal of the Korean Ceramic Society
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    • v.34 no.3
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    • pp.225-232
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    • 1997
  • The performance characteristics of high rate discharge LiSOCl2 cells are highly affected by carbon cathode. During the cell discharge, SOCl2 reduction takes place at the porous carbon cathode, resulting in the precipitation of reaction products, mainly LiCl, within the pores of the substrate. This leads to eventual passivation of the cathode surface and resulting cell failure. To improve the cathode performance, we ex-amined discharge reactions of cathodes (half-cell, 50 mA/$\textrm{cm}^2$ constant current) with various surface density and thickness. The carbon cathode with the optimum capacity for our application is surface density 0.04 g/$\textrm{cm}^2$ and thickness 1.4mm carbon. The carbon cathode with surface density 0.04g/$\textrm{cm}^2$ and thickness 1.4 mm exhibits decreased polarization, increased discharge duration time and capacity (Ah/$\textrm{cm}^2$) as compared with that with surface density 0.04g/$\textrm{cm}^2$ and thickness 0.8mm. The porosities analyses on the two carbon cathodes show that total pore volume of the carbon cathode with thickness 1.4 mm is larger than that with thickness 0.8mm. The increased volume of mesopores (0.05$\mu$m~0.5$\mu$m) and macropores(>0.5$\mu$m) is ob-served with the carbon cathode with thickness 1.4mm as compared with that with thickness 0.8mm, which can be related with the observed capacity increase. We observed LiCl crystals, cubic crystallites and fused, plate-like aggregates, and some elemental S as discharge products by EDS and XRD.

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Effect of Y on the Corrosion Properties of Mg-Li-AI Alloy (Mg-Li-AI합금의 부식특성에 미치는 Y의 영향)

  • Kim, Sun-Ho;Kim, Gyeong-Hyeon;Bae, Cha-Heon;Kim, In-Bae
    • Korean Journal of Materials Research
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    • v.6 no.11
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    • pp.1074-1081
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    • 1996
  • Mg-8Li-4AI 합금의 부식특성에 미치는 Y의영향을 전기화학적 분극시험 및 침지시험을 통하여 조사하였다. 전기 화학적 분극시험에서는 Y첨가량이 증가함에 따라 활성화 영역이 감소하엿고 부식전위가 증가하였으며, Y이 4.08wt% 첨가된 경우가 Y이 첨가되지 않은 경우에 비해 부식속도가 크게 감소하였다. 침지시험에서도 Y의 첨가량이 증가함에 따라 Y을 첨가하지 않은 시편에 비하여 무게감량 및 부시속도가 감소하였으며, Y이 첨가되지 않은 합금의 부식속도는 침지시간에 따라 급격히 증가하였지만 Y이 첨가되지 않은 합금의 부식속도는 침지시간에 따라 급격히 증가하였지만 Y이 4.8wt% 첨가된 합금은 96시간 이후부터 더 이상 증가하지 않았다. 이러한 결과는 Y 화합물(Mg24Y5)이 $\alpha$/$\beta$계면에서 희생 양극으로 작용하였기 때문이라고 생각된다. 따라서 Y의 첨가는 Mg-Li-AI 합금의 내식성을 향상시키는 역할을 한 것으로 판단된다.

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Numerical Analysis of the electrochemical performance of a zinc-air fuel cell (수치해석을 이용한 아연공기전지의 전기화학적 성능 연구)

  • Kim, Jungyun;Park, Sangmin;Oh, Taeyoung;Lee, Hoil
    • 한국신재생에너지학회:학술대회논문집
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    • pp.74.1-74.1
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    • 2010
  • 수치해석을 이용하여 형상 및 운전 조건에 따른 금속공기전지의 전기화학적 성능 변화를 조사하였다. 저전류밀도 영역에서의 전지 성능은 농도손실에 의한 영향이 미미하므로 활성화 손실과 저항손실만을 고려한 수치해서 모델을 적용하였다. 지배방정식은 전기전도식을 이용하였으며 전극 표면의 활성화손실을 모사하기위해 아연극(음극)에는 butler-volmer식을, 공기극(양극)에는 tafel식을 적용하였다. 실험결과와의 비교/분석을 통하여 수치해석 모델의 타당성을 검증하였다. 또한, 아연극과 공기극 사이의 간격과 전해질 농도 변화에 따른 아연공기전지 내부에서의 전류밀도분포를 조사하였으며, 분극곡선을 통해 전기화학적 성능을 평가하였다.

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Structure of Calcareous Coating Films and Their Characteristics in Natural Seawater with Dissolved CO2 Gas (해수 중 CO2 기체의 유입에 의해 제작한 코팅막의 구조와 특성)

  • Gang, Jae-Uk;Park, Jun-Mu;Gang, Jun;Lee, Myeong-Hun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.309-309
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    • 2014
  • 음극방식법은 피방식체에 외부전원을 인가하거나 보다 활성인 금속을 전기적으로 연결하여 피방식체의 전위가 일정 전위까지 음극분극 되도록 하여 부식을 억제하는 방법이다. 이러한 음극 방식의 결과로 $OH^-$이온이 금속 표면 부근에 생성되고 금속/해수 사이의 pH 증가를 유발하게 되며, 높은 pH는 $Mg(OH)_2$$CaCO_3$의 석출을 유발한다. 전착 박막은 각각 1, 3, 6, 12시간 및 5, 15, $20mA/cm^2$의 전류 밀도 조건에서 자연 해수, $CO_2$ 가스가 용해된 해수 용액 내에서 스틸 기판 상에 전기적 증착기술을 가해 형성되었다. 상기 조건에서 증착 된 박막의 내용물은 주사 전자 현미경 (SEM) 및 X-선회절(XRD)에 의해 조사되었다. 또한 코팅 박막의 내식성은 전기화학적 양극 분극시험에 의해 평가되었다.

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Cryogenic fracture behaviors and polarization characteristics according to sensitizing heat treatment on structural material of the nuclear fusion reactor (핵 융합로 구조재료의 예민화 열처리에 따른 극저온 파괴거동 및 분극특성)

  • Kwon, Il-Hyun;Chung, Se-Hi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.2
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    • pp.311-320
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    • 1998
  • The cryogenic fracture behaviors of austenitic stainless steel HN2 developed for nuclear fusion reactor were evaluated quantitatively by using the small punch(SP) test. The electrochemical polarization test was applied to study thermal aging degradation of HN2 steel. The X-ray diffraction(XRD) analysis was conducted to detect carbides and nitrides precipitated on the grain boundary of the heat treated HN2 steel. The mechanical properties of the HN2 steel significantly decreased with increasing time and temperature of heat treatment or with decreasing testing temperature. The integrated charge(Q) obtained from electrochemical polarization test showed a good correlation with the SP energy(ESP) obtained by means of SP tests. From the results observed in the x-ray diffraction and anodic polarization curve, it was known that the material the grain boundary. Combining SP test and electrochemical polarization test, it could be useful tools to non-destructively evaluate the cryogenic fracture behaviors and the aging degradation for cryogenic structural material.

Evaluation on Damage Behavior of Al-4.5%Mg-0.6%Mn Al Alloy with Potentiostatic Experiment Time (Al-4.5%Mg-0.6%Mn 알루미늄 합금의 정전위 시간 변수에 따른 손상거동 평가)

  • Kim, Seong-Jong;Woo, Yong-Bin;Han, Min-Su;Jang, Seok-Ki
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.18 no.6
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    • pp.569-576
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    • 2012
  • In general, aluminum alloys forms the passive film($Al_2O_3$, $Al_2O_3{\cdot}3H_2O$) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

Anodic Oxidation of Potassium Iodide Solution (Ⅰ) (요오드화칼륨 수용액의 양극산화 (제1보))

  • Nam, Chong-Woo;Kim, Hark-Joon
    • Journal of the Korean Chemical Society
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    • v.17 no.5
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    • pp.378-384
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    • 1973
  • To investigate the mechanism of the reaction of electrolytic oxidation of iodide to iodate ions, polarization curves are determined in various kinds of solution using electrodeposited lead peroxide and platinum anodes. It was observed from the polarization curves that the limiting current is exists at concentration 1.5 M of potassium iodide, and these limiting current disappeared as potassium hydroxide was added up to concentration of 0.1 M. while in case of platinum anode, limiting current did not appear in dilute potassium iodide solution. These results are owing to the chemical reaction, $PbO_2+2I^{-}+2H^+{\to}PbO+I_2+H_{2}O$ ocurring at the surface of lead peroxide anode. Also, we studied to obtain the optimum conditions of electrolytic preparation of iodate from iodide solution using a cell without the diaphragm. The results are that; (a) addition of potassium dichromate at the anti-reducing agent is proper in concentration of 0.1 g/l, (b) electrolytic temperature is not so much effective in raising the current efficiency, (c) current efficiency is increased with current density, and (d) electrolysis is the most effective in weak alkaline solutions.

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Corrosion mitigation of photovoltaic ribbon using a sacrificial anode (희생양극을 이용한 태양광 리본의 부식 저감)

  • Oh, Wonwook;Chan, Sung-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.3
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    • pp.681-686
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    • 2017
  • Degradation is commonly observed in field-aged PV modules due to corrosion of the photovoltaic ribbon. The reduced performance is caused by a loss of fill factor due to the high series resistance in the PV ribbon. This study aimed to mitigate the degradation by corrosion using five sacrificial anodes - Al, Zn and their alloys - to identify the most effective material to mitigate the corrosion of the PV ribbon. The corrosion behavior of the five sacrificial anode materials were examined by open circuit potential measurements, potentiodynamic polarization tests, and galvanic current density and potential measurements using a zero resistance ammeter. Immersion tests for 120 hours were also conducted using materials and damp heat test tests were performed for 1500 hours using 4 cell mini modules. The Al-3Mg and Al-3Zn-1Mg sacrificial anodes had a low corrosion rate and reduced drop in power, making then suitable for long-term use.

The Study on the Electrochemical Polarization Characteristics of Hydrogen Embrittlement for Ferrite Stainless Steel with Welding Conditions (용접조건에 따른 페라이트 스테인리스강에 대한 수소취성의 전기화학적 분극특성에 관한 연구)

  • Choi, Byung-Il;Lim, Uh-Joh
    • Journal of the Korean Institute of Gas
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    • v.9 no.4
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    • pp.30-35
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    • 2005
  • In order to examine the electrochemical polarization characteristics of hydrogen embrittlement far STS444 with welding conditions, this paper carried out the accelerated hydrogen osmosis test and the electrochemical polarization test. That is, in $0.5M\; H_2SO_4+0.001M\;As_2O_3$ solution, the hydrogen embrittlement behavior of STS444 added to load of $1,400kg/cm^2$ together with hydrogen osmosis by current of $30mA/cm^2$ far 60 min. was considered. In researching the electrochemical polarization characteristics of hydrogen embrittlement for STS444 with welding conditions, the previous study clarified that tensile strength or elongation became low influenced by absorption of oil or water before welding. In this paper, we proposed the advanced mechanism of hydrogen embrittlement that integrated electrochemical corrosion with the existing mechanism of hydrogen embrirtlement.

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