In Situ Analysis on Carbon Infiltration into Ni-YSZ Cermet Anode of Solid Oxide Fuel Cell

In Situ Analysis on Carbon Infiltration into Ni-YSZ Cermet Anode of Solid Oxide Fuel Cell
Issue Date
2011 MRS Fall Meeting & Exhibit
Many people intend that SOFC possesses capability to directly utilize carbon-containing fuels such as hydrocarbons and carbon monoxide for power generation. However, carbon deposition and consequent carbon infiltration induced by carbon-containing fuels easily deactivate Ni-YSZ cermets commonly used for SOFC anode and finally lead to catastrophic fracture of Ni composites by the expansion of carbon filament. Carbon infiltration alters electrical and mechanical properties of Ni-YSZ cermets. In this work, electrical conductivity measurement, TGA analysis and volumetric expansion measurement by CCD camera were used to monitor change of electrical and mechanical properties in Ni-YSZ cermets in the midst of carbon infiltration. Electrical conductivity of Ni-YSZ specimens decreased when Ni-YSZ specimens were exposed to feeding gases where carbon formation by carbon-containing fuels was thermodynamically favorable, which means that the carbon activity > 1. The decrease in electrical conductivity is likely to be resulted from the breakage of the electron conducting network composed of Ni particles by carbon infiltration and formation of Ni carbide and filamentous carbon. Moreover, the decrease rate of electrical conductivity was correlated to the carbon activity determined by mole fraction of carbon-containing fuels and addition of steam to the feeding gas and actual amount of carbon formation confirmed by the conventional TGA analysis. Therefore, electrical conductivity measurement can be utilized as a facile means to directly investigate carbon infiltration in the Ni-based anode. Additionally, the expansion of the filamentous carbon inside of Ni-YSZ specimens leaded to overall volumetric expansion of the specimens and evolution of change in volume was recorded when carbon infiltration occurred.
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