High-temperature stability and oxidation behavior of SiOC/HfO2 ceramic nanocomposite in air

High temperature stability (1100 -1500 degrees C) and oxidation behavior at 1500 degrees C of the SiOC/HfO2 ceramic nanocomposite were investigated in air. Consumption of free carbon dominated thermal stabilities of the bulk at below 1200 degrees C. Whereas, the continuous cristobalite scale, rather than HfSiO4, was responsible for the improved oxidation resistance at exceeding 1200 degrees C. At 1500 degrees C, HfSiO4, with maximum 30 vol. % concentration for duration of similar to 15 h, suffered ruptured spherical-bubbles by volatilized species and did not consolidate into a completely protective scale. Thus, the bulk exhibited limited resistance to oxidation at 1500 degrees C for long-term applications.