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RISS 인기검색어
- 검색키워드
- 저자 : Katsuhiko Yamaji (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Degradation of SOFC Cell/Stack Performance in Relation to Materials Deterioration
Yokokawa, Harumi,Horita, Teruhisa,Yamaji, Katsuhiko,Kishimoto, Haruo,Brito, M.E. The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1
The characteristic features of solid oxide fuel cells are reviewed from the viewpoint of the thermodynamic variables to be developed inside cells/stacks particularly in terms of gradients of chemical potential, electrical potential and temperature and corresponding flows of air, fuel, electricity and heat. Examples of abrupt destruction of SOFC systems were collected from failures in controlling their steady flows, while continuous degradation was caused by materials behaviors under gradients of chemical potentials during a long operation. The local equilibrium approximation has been adopted in NEDO project on the durability/reliability of SOFC stacks/systems; this makes it possible to examine the thermodynamic stability/reactivity as well as mass transfer under the thermodynamic variable gradients. Major results of the NEDO project are described with a focus on degradation/deterioration of electrolyte and electrode materials.
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Materials Chemical Point of View for Durability Issues in Solid Oxide Fuel Cells
Yokokawa, Harumi,Horita, Teruhisa,Yamaji, Katsuhiko,Kishimoto, Haruo,Brito, M.E. The Korean Ceramic Society 2010 한국세라믹학회지 Vol.47 No.1
Degradation in Solid Oxide Fuel Cell performance can be ascribed to the following fundamental processes from the materials chemical point of view; that is, diffusion in solids and reaction with gaseous impurities. For SOFC materials, diffusion in solids is usually slow in operation temperatures $800\sim1000^{\circ}C$. Even at $800^{\circ}C$, however, a few processes are rapid enough to lead to some degradations; namely, Sr diffusion in doped ceria, cation diffusion in cathode materials, diffusion related with metal corrosion, and sintering of nickel anodes. For gaseous impurities, chromium containing vapors are important to know how the chemical stability of cathode materials is related with degradation of performance. For LSM as the most stable cathode among the perovskite-type cathodes, electrochemical reduction reaction of $CrO_3$(g) at the electrochemically active sites is crucial, whereas the rest of the cathodes have the $SrCrO_4$ formation at the point where cathodes meet with the gases, leading to rather complicated processes to the degradations, depending on the amount and distribution of reacted Cr component. These features can be easily generalized to other impurities in air or to the reaction of nickel anodes with gaseous impurities in anode atmosphere.
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Materials Chemical Point of View for Durability Issues in Solid Oxide Fuel Cells
Harumi Yokokawa,Teruhisa Horita,Katsuhiko Yamaji,Haruo Kishimoto,M. E. Brito 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.1
Degradation in Solid Oxide Fuel Cell performance can be ascribed to the following fundamental processes from the materials chemical point of view; that is, diffusion in solids and reaction with gaseous impurities. For SOFC materials, diffusion in solids is usually slow in operation temperatures 800~1000oC. Even at 800oC, however, a few processes are rapid enough to lead to some degradations; namely, Sr diffusion in doped ceria, cation diffusion in cathode materials, diffusion related with metal corrosion, and sintering of nickel anodes. For gaseous impurities, chromium containing vapors are important to know how the chemical stability of cathode materials is related with degradation of performance. For LSM as the most stable cathode among the perovskitetype cathodes, electrochemical reduction reaction of CrO3(g) at the electrochemically active sites is crucial, whereas the rest of the cathodes have the SrCrO4 formation at the point where cathodes meet with the gases, leading to rather complicated processes to the degradations, depending on the amount and distribution of reacted Cr component. These features can be easily generalized to other impurities in air or to the reaction of nickel anodes with gaseous impurities in anode atmosphere.
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Degradation of SOFC Cell/Stack Performance in Relation to Materials Deterioration
Harumi Yokokawa,Teruhisa Horita,Katsuhiko Yamaji,Haruo Kishimoto,M. E. Brito 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1
The characteristic features of solid oxide fuel cells are reviewed from the viewpoint of the thermodynamic variables to be developed inside cells/stacks particularly in terms of gradients of chemical potential, electrical potential and temperature and corresponding flows of air, fuel, electricity and heat. Examples of abrupt destruction of SOFC systems were collected from failures in controlling their steady flows, while continuous degradation was caused by materials behaviors under gradients of chemical potentials during a long operation. The local equilibrium approximation has been adopted in NEDO project on the durability/reliability of SOFC stacks/systems; this makes it possible to examine the thermodynamic stability/reactivity as well as mass transfer under the thermodynamic variable gradients. Major results of the NEDO project are described with a focus on degradation/deterioration of electrolyte and electrode materials.
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