Oxidation, mechanical and thermal properties of hafnia-silicon carbide nanocomposites

Dense nanocomposites constituted from 70/30 vol% of hafnia-silicon carbide and were prepared by spark plasma sintering. Silicon carbide suppresses grain growth. The fracture strength of as prepared composites is 400-600 MPa. Oxidation up to 1600 °C in air for 10 h has minor influence on the mechanical strength, which is ascribed to the dense nature of the oxidation scale. The high density of the oxidation scale is attributed to a volume increase when silicon carbide oxidizes and reacts with hafnia to form hafnium silicate. The composite has a thermal conductivity of 14 W m−1 K−1 at room temperature. Design approaches for further enhancement of ultrahigh temperature properties of oxide/non-oxide composites are discussed.