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연구논문초록(’81-’90) : Au , O2/CO2 CO2-3 고온기준전극의 제작 및 특성 연구
윤승열,정도양,목승곤 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.1
For electochemical approaches of the corrosion of materials used in molten carbonate fuel cells, a high temperature reference electrode utilizing the half cell reaction of 1/2 O₂+CO₂+2e=CO₃^(2-) was fabricated and ite properties were investigated. The half cell Au, O₂/CO₂ CO₃^(2-) contained in a mullite membrane displayed clear reversibility showing both Nernstian behavior and no hysteresis in the cyclic polarization experiments near equilibrium potentials. It gave also high potential stability, and good reproducibility as well. As an electrolyte 62m/o Lip CO₃+38m/o K₂CO₃ eutectic melt was employed in which 99.99% Au foil was partially dipped to function as an electron source. The standard gas composition over the melt was 2/3 atm CO₂+ 1/3 atm O₂ flowint at a ratc of 100 cc/min. A thecoretical analysis indicated that the equilibrium potential should be insensitive to the small variation of gas composition in the neighborhood of the above mentioned atandard gas composition.
연구논문초록(’81-’90) : 인산연료전지용 탄소재료의 전기화학적 분극특성
윤승열,신진교,정도양 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.1
Electrochemical polarization behaviors, of various carbon electrodes were measured using potentiodynamic, potentiostatic and cyclicvoltametric method under phosphoric acid fuel cell conditions at ambient pressure. The carbon electrodes were made of various carbon sources such as carbon blacks bonded with polytetraffuoroethylene, commercial carbon papers, a glassy carbon and a graphite. The shape of potentiodynamic anodic polarization curves for the carbon electrodes could be classified into four types with different Tafal-like slopes and polarized current values depending on carbon species. The results of tests revealed that the larger the Tafel-like slope and current values, the greater the degree of disorder on the carbon surface. Measurements of current efficiency for CO₂ evolution and cyclic votamogram indicated that at least two anodic processes occurred in the corrosion of carbon : the evolution of CO₂ and the formation of a surface oxide. At all potentials a linear relationship was observed between logarithms of the potentiostatic anodic current, i and polarization time, t. The Slope of the log i vs. log t plot was dependent on carbon species and electrode potential. It had a larger value at lower potentials. This phenomenon was ascribed to the reduction of active sites on carbon surface as the polarization time elapsed.
윤승열 대한금속재료학회(대한금속학회) 1973 대한금속·재료학회지 Vol.11 No.1
염소산이온의 농도 0.001∼0.025molar, 온도범위 28°∼70℃에서 구리의 부식반응속도에 관하여 연구하였다. 산화반응속도는 용액내에 축적되는 구리이온의 양을 시간에 따라 측정하면서 조사하였고, 상온에서 구리시편의 전극전위 측정도 병행하였다. 용해반응이 일어나는 동안에 수소이온의 감소량은 생성된 구리이온 양의 두배로 나타났고 염소이온이 반응 생성물로 확인되었다. 용액내에 축적되는 구리이온의 양, [Cu^(++)]와 시간, t에 대한 log-log plot를 하면 다음과 같은 실험식을 얻을 수 있었다. [Cu^(++)]^(5/4)=s·(t-t_0) 여기에서 s와 t_0는 실험조건에 따르는 상수이며 특히 t_0는 구리시편의 표면처리에 따라 변하는 상수로 나타났다. 구리의 용해속도는 pH 0∼3.5 범위에서 수소이온 농도에 무관한 것으로 나타났다. 용해속도는 구리이온 농도와 용액의 pH가 Cu₂O를 형성하는 데 적합한 조건이 되었을 때 급격히 변화하는 것을 볼 수 있었다. 구리시편의 부식전위는 Cu/Cu^(++)평형전극전위의 값에 매우 가까운 값을 나타내었고, 초기 수조이온 농도가 일정할 때 염소산이온의 농도가 증가함에 따라 부식 전위가 증가하는 것이 관찰되었다. 구리의 용해속도는 염소산이온 농도에 1/2승에 의존하는 것을 알 수 있었다. 위에 관찰된 모든 현상에 알맞는 부식기구에 대한 가설은 염소산 이온이 구리시편에 흡착한 뒤 염소산이온 내부의 산소원자와 금속구리 사이에서 일어나는 charge transfer반응이 부식반응의 slow step이 되기 때문일 것이라고 생각하였다. 앞에 나타난 특이한 반응차수도 구리시편의 부식전위가 부식반응 속도에 영향을 주는 것으로 해석하여 이론적으로 유도할 수 있었다.
Au , O2/CO2 CO2-3 고온기준적긍의 제작 및 특성 연구
윤승열,정도양,목승곤 한국부식학회 1989 Corrosion Science and Technology Vol.18 No.1
For electrochemical approaches to the corrosion of materials used in molten carbonate fuel cells, a high temperature reference electrode utilizing the half cell reaction of 1/2 O₂ + CO₂ + 2e = CO₃^(2-) was fabricated and its properties were investigated. The half cell Au, O₂/CO₂ CO₃^(2-) contained in a mullite membrane displayed clear reversibllity showing both Nernstian behavior and no hysteresis in the cyclic polarization experiments near equilibrium potentials. It gave also high potential stability, and good reproducibility as well. As an electrolyte 62 m/o Li₂CO₃ + 38 m/o K₂CO₃ eutectic melt was employed in which 99.99% Au foil was partially dipped to function as an electron source. The standard gas composition over the melt was 2/3 atm CO₂ + 1/3 atm O₂ flowing at a rate of 100 cc/min. A theoretical analysis indicated that the equilibrium potential should be insensitive to the small variation of gas composition in the neighborhood of the above mentioned standard gas composition.