Densification, Creep and Oxidation Behavior of ZrB2-SiC Based Ultra-High Temperature Ceramic Composites

ZrB₂-SiC composites are candidate materials for use in thermal protection systems for leading edges and nose-cones of hypersonic vehicles. Densification of ZrB₂ is considered challenging, because of its covalent bonding, which is responsibility for sluggish rate of lattice diffusion. It has been noticed that addition of 20 vol% SiC not only improves the creep and oxidation resistance in air by formation of a protective scale borosilicate glass, but also densification by inhibiting grain growth. Whereas densification and oxidation resistance are improved by addition of Si₃N₄, creep resistance is adversely affected due to increased grain boundary sliding.