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

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 degrees C in static air. The SiBCN/HfC composites have an oxidation rate constant K5-20 of 1.1 mu m(2)/h at 1500 degrees C, which is less than that for other SiBCN-based ceramics (5.4 mu m(2)/h). After oxidation at 1750 degrees C, HfO2 and HfSiO4 spherical 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. (C) 2019 Published by Elsevier B.V.