One component metal oxide sintering additive for β-SiC based on thermodynamic calculation and experimental observations

摘要

This paper examines a range of metal oxides, including those containing relatively safe elements under neutron irradiation, such as Cr, Fe, Ta, Ti, V and W, as well as widely used oxides, Al₂O₃, MgO and Y₂O₃, as a sintering additive for β-SiC theoretically and experimentally. After selecting the most probable SiC oxidation reaction at 1973–2123 K, the condition where the metal oxide additive does not decompose SiC was calculated based on the standard Gibbs formation free energies. Thermodynamic calculations revealed that Al₂O₃, MgO and Y₂O₃ could be an effective sintering additive without decomposing SiC under hot pressing conditions, which was demonstrated experimentally. On the other hand, no one component metal oxide that contains a safe element for nuclear reactor applications was found to be an effective sintering additive due to the formation of metal carbides and/or silicides. Overall, the simulation based on thermodynamic calculations was found to be quite useful for selecting effective metal oxide additives.