Oxidation mechanism and kinetics of SiBCN/HfC ceramic composites at high temperatures

摘要

SiBCN/HfC ceramic composites were obtained via mechanical alloying and hot-press sintering. We evaluated the high-temperature oxidation resistance of the SiBCN/HfC ceramic composites after heat treatments at 1500 and 1750?°C in static air. The SiBCN/HfC composites have an oxidation rate constant K5-20of 1.1?μm2/h at 1500?°C, which is less than that for other SiBCN-based ceramics (5.4?μm2/h). After oxidation at 1750?°C, HfO2and HfSiO4spherical nanocrystals resulting from the oxidation of HfC were dispersed in silica layers that acted as a dense continuous protective coating on the surface of the SiBCN/HfC samples and provided a higher resistance to high-temperature exposure.