High-temperature oxidation behavior of advanced fuel cladding SiC under various oxygen partial pressures

摘要

SiC is gaining increasing attention in nuclear fuel cladding applications as a promising fuel cladding. To understand its soundness, the high-temperature oxidation behavior of high-density bulk SiC was investigated in air and vacuum (10 Pa)) and the validity of the experimental results was confirmed by thermodynamic calculations. The high-density bulk SiC was prepared from powder using spark plasma sintering (SPS). Bulk SiC and that in contact with the Al_2O_3 plate were heat treated in both air and vacuum, at 1573 K and 1773 K. The phases in the heat-treated samples were identified by X-ray diffraction and their microstructures were analyzed by scanning electron microscopy. For the samples heat-treated in air, we observed a SiO_2 layer on the surface with a thickness of ～1 μm and some cracks. Alternatively, a highly porous surface layer was observed for the samples heat treated in a vacuum. The thicknesses of the SiO_2 and porous layers increased with increasing heat-treatment temperature. In addition, it was found that SiC did not react with Al_2O_3 in vacuum at 1573 K, but did react at 1773 K. These results will make an important influence on the development of advanced fuel claddings.