• 제목/요약/키워드: electrode polarization

검색결과 364건 처리시간 0.028초

고분자전해질 연료전지의 환원전극 백금 담지촉매의 백금 담지비에 따른 성능변화 (Effect of Pt amount in the Pt/C for cathode catalyst on the performance of PEMFC)

  • 조용훈;조윤환;박현서;성영은
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2006년도 춘계학술대회
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    • pp.107-109
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    • 2006
  • This study focuses on a determination of amount of Pt in the Pt/C for catalysts of polymer electrolyte membrane fuel cells (PEMFC). PEMFC offer low weight and high power density and being considered for automotive and stationary power applications. The PEMFC performance is influenced by several factors, including catalysts and structure of electrode and membrane type. Catalyst of electrode is important factor for PEMFC. One of the obstacles prevent ing polymer electrolyte membrane fuel cells from commercialization is the high cost of noble metals to be used as catalyst, such as platinum To effectively use these metals, they have to be will dispersed to small particles on conductive carbon supports. The optimal amount of Pt in Pt/C for cathode catalyst was investigated by using polarization curves in single cell with $H_2/O_2$ operation.

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Micro-droplet cell을 이용한 Fe-17Cr 합금의 공식 발생에 대한 연구 (A Study on the Initiation of Pitting Corrosion of Fe-17Cr Alloy Using Micro-Droplet Cell Technique)

  • 김재중;이재봉
    • 대한금속재료학회지
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    • 제46권12호
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    • pp.809-816
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    • 2008
  • The influences of various parameters such as inclusions, surface roughness, exposed areas and chloride ion concentrations on the initiation of pitting of Fe-17Cr alloy were investigated, using micro-droplet cell technique. Micro-droplet cell allows one to align the micro-electrode to the desired spot of the working electrode and measure directly local currents with the potentiodynamic polarization. Micro electrochemical tests were carried out at the inclusions after EDX analysis of inclusion. EDX analysis identified inclusions as Cr-oxides. It was found that some active inclusions among Cr-oxide inclusions acted as initiation sites for pitting corrosion. In addition, the rougher surface and the denser chloride ion concentration offered easier pit initiation sites, causing the more susceptible to pitting corrosion.

Structural and Magnetic Properties of Co2MnSi Heusler Alloy Films

  • Lim, W.C.;Okamura S.;Tezuka N.;Inomata K.;Bae, J.Y.;Kim, H.J.;Kim, T.W.;Lee, T.D.
    • Journal of Magnetics
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    • 제11권1호
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    • pp.8-11
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    • 2006
  • Recently half-metallic full-Heusler alloy films have attracted significant interests for spintronics devices. As these alloys have been known to have a high spin polarization, very large TMR ratio is expected in magnetic tunnel junctions. Among these alloys, $Co_2MnSi$ full-Heusler alloy with a high spin polarization and a high Curie temperature is considered a good candidate as an electrode material for spintronic devices. In this study, the magnetic and structural properties of $Co_2MnSi$ Heusler alloy films were investigated. TMR characteristics of magnetic tunnel junctions with a $Co_2MnSi/SiO_2/CoFe$ structure were studied. A maximum MR ratio of 39% with $SiO_2$ substrates and 27% with MgO(100) substrates were obtained. The lower MR ratio than expectation is considered due to off-stoichiometry and atomic disorder of $Co_2MnSi$ electrode together with oxidation of the electrode layer.

Preparation and Electrochemical Performance of CNT Electrode with Deposited Titanium Dioxide for Electrochemical Capacitor

  • Kim, Hong-Il;Kim, Han-Joo;Morita, Masayuki;Park, Soo-Gil
    • Bulletin of the Korean Chemical Society
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    • 제31권2호
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    • pp.423-428
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    • 2010
  • To reduce polarization of electrochemical capacitor based on carbon nanotube, titanium oxide nanoparticles were deposited by ultrasound. The pore distribution of $TiO_2$/CNT nanoparticle exhibited surface area of $341\;m^2g^{-1}$ when $TiO_2$ content was 4 wt %, which was better than that of pristine CNT with surface area of $188\;m^2g^{-1}$. The analyses indicated that titanium oxide (particle diameter < 20 nm) was deposited on the CNT surface. The electrochemical performance was evaluated by using cyclic voltammetry (CV), impedance measurement, and constant-current charge/discharge cycling techniques. The $TiO_2$/CNT composite electrode showed relatively better electrochemical behaviors than CNT electrode by increasing the specific capacitance from $22\;Fg^{-1}$ to $37\;Fg^{-1}$ in 1 M $H_2SO_4$ solution. A symmetric cell assembled with the composite electrodes showed the specific capacitance value of $11\;Fg^{-1}$ at a current loading of $0.5\;mAcm^{-2}$ during initial cycling.

적층형 세라믹 압전 액추에이터의 전계강도와 압축응력에 따른 변위특성 해석 (Electric Field Strength and Compressive Stress Effects on the Displacement of Multilayered Ceramic Actuators)

  • 송재성;정순종;김인성;민복기
    • 한국전기전자재료학회논문지
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    • 제18권3호
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    • pp.248-252
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    • 2005
  • The effects of electric field strength and mechanical compressive stress on the displacement of multilayered ceramic actuator, stacked alternatively 0.2 (PbM $n_{1}$3/N $b_{2}$3/ $O_3$)-0.8(PbZ $r_{0.475}$ $Ti_{0.525}$ $O_3$) ceramic thin films and 70Ag-30Pd electrodes were investigated. Because the actuators were designed to stack ceramic layer and electrode layer alternatively, the ceramic-electrode interfaces may act as a resistance to motion of domain wall. so the polarization and strain were affected by the amount of 180$^{\circ}$domain, electric field strength and mechanical compressive stress. Consequently, the change of polarization, displacement with respect to field strength, and mechanical compressive stress were likely to be caused by readiness of the domain wall movement around the ceramic-electrode interfaces.ces.

황산 용액중의 분극시 나타나는 탄소전극들의 계면반응 (Study on the surface reactions of carbon and graphite electrodes in sulfuric acid solution)

  • 오한준;김인기;이종호;이영훈
    • 한국결정성장학회지
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    • 제6권4호
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    • pp.648-662
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    • 1996
  • 임피던스 스펙트럼을 이용하여 황산 용액에서 glassy carbon과 인조흑연(PVDF 합성 흑연)의 전극표면에 cyclic 분극을 부하 하였을 경우 전극표면에서 나타나는 표면반응에 대하여 조사하여 . 두 재료 표면에서 산소의 산화 혹은 환원과 관련되거나 또는 탄소재료 표면에 화학흡착된 표면작용기(surface functional group)의 변화와 관련되는 것으로 생각되는 산화환원 피크가 potentio-dynamic곡선에서 나타났다. 이러한 전극 표면에서의 표면작용기의 산화환원은 glassy carbon과 PVDF합성 흑연의 임피던스 스펙트럼에도 커다란 영향을 미치는 것으로 나타났다. 또 glassy carbon과 PVDF합성 흑연에서의 임피던스 파라미터는 분극부하에의해 현저한 변화가 나타났다.가 나타났다.

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소결식 니켈극 제조기술 개발 (Development of Preparation Technique of Sintered Ni Electrode)

  • 김찬중;김대룡
    • 한국수소및신에너지학회논문집
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    • 제10권3호
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    • pp.159-170
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    • 1999
  • Recently Ni/MH secondary battery have been studied very extensively because of containing no pollutants as well as superior performance. However comparing to widely studying high capacity of hydrogen storage alloys electrode, the capacity of Ni electrode is inferior. Using for high capacity Ni/MH battery as a anodic materials, the study about high capacity Ni electrode is necessary. To making high capacity Ni electrode, active materials were impregnated in various polarization impregnation conditions. Plaque, milling for 6hr and sintered at $800^{\circ}C$, indicated porosity over 80%, and porosity were increased with proper condition electrochemical etching treatment. Proper impregnation condition was 40~80mA/cm, polarizing time was 5~10min.

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분극저항에 의한 온라인 부식속도 측정 시스템에 관한 연구 (Study on an On-line Measurement System of Corrosion Rate by Linear Polarization Resistance)

  • 문전수;이재근;이재봉;박필양
    • Corrosion Science and Technology
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    • 제11권4호
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    • pp.135-140
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    • 2012
  • The linear polarization resistance method is one of the widely used techniques for the corrosion rate monitoring in the water circulating systems of plants. The measurement is simple and rapid, so that a continuous on-line monitoring is possible without any shutdown of plants. A 2-electrode polarization corrosion rate measurement system was installed in a laboratory using a data acquisition board and PC. The signal processing parameters were optimized for the accurate corrosion rate measurement, and the polarization resistance was compensated with the solution resistance measured by the high frequency sine wave signal of an output channel. The precision of corrosion rate data was greatly improved by removing the initial noise signals on measuring the polarization resistance.

용융 (60 몰% $AlCl_3$-40 몰% NaCl) 염 속에서의 알루미늄전극의 반응속도론적 연구 (A Kinetic Study of the Aluminum Electrode in Molten 60 Mole Percent $AlCl_3$-40 Mole Percent NaCl at 453${\circ}K$)

  • G. F. Uhlig;T. N. Andersen;S. Johns;H. Eyring
    • 대한화학회지
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    • 제18권6호
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    • pp.400-407
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    • 1974
  • 60몰%$AlCl_3$-40몰% NaCl의 용융염($453^{\circ}$<\TEX>K)속에든 알루미늄 전극에 대하여 전류-전압 편극곡선을 얻었다. 50mA/$CM^2$보다 큰 전류밀도에서는 옴-저항에 의한 전위차가 양극전위에 상당히 기여하므로 저항이 큰 $AlCl_3$(혹은 $AlCl_3$ 의 농도가 큰 멜트)의 층이 양극표면에 가까이 형성된다고 결론지었다. IR-전위차에 대하여 보정한 후의 Tafel곡선과 Allen-Hickling 곡선으로 부터 겉보기 transfer-coefficient, ${\alpha}_a$=(2.3RT/F)(dlogi/d${\eta}$)=$1.5{\pm}0.25$가 얻어졌다. 약 30mA/$cm^2$보다 큰 음극전류밀도에서는 느린 이온확산과 dendrite 생장 때문에 속도론적 측정이 방해 받았다.

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Glycine-Nitrate 법으로 제조한 (Ba0.5Sr0.5)0.99Co0.8Fe0.2O3-δ 공기극의 분극저항 (Polarization Resistance of (Ba0.5Sr0.5)0.99Co0.8Fe0.2O3-δ Air Electrode Synthesized by Glycine-Nitrate Process)

  • 문지웅;임용호;오유근;이미재;최병현;황해진
    • 한국세라믹학회지
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    • 제42권12호
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    • pp.800-807
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    • 2005
  • Cathode material, $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$, for low temperature SOFC was prepared by the Glycine-Nitrate synthesis Process (GNP). Characteristics of the synthesized powders were studied with controlling the pH of a precursor solution. Highly acidic precursor solution increased a perovskite forming temperature. It is considered that Ba and Sr cannot complex by carboxylic acid group of glycine, because under highly acidic condition the caboxylic group mainly combined with H+ insead of alkaline earth cations. A lack of bond between cations and glycine resulted in selective precipitation of the elements during evaporation of the precursor solution. In case of using precursor solution with pH %2\~3$, a single perovskite phase was obtained at $1000^{\circ}C$. Polarization resistance of $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ was measured by AC impedance spectroscopy from the two electrode symmetric cell. Area specific resistance of the $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ air electrode at $500^{\circ}C\;and\;600^{\circ}C$ were $0.96{\Omega}{\cdot}cm^2\;and\;0.16{\Omega}{\cdot}cm^2$, respectively.