Effect of B₄C addition on the microstructures and mechanical properties of ZrB₂-SiC ceramics

ZrB₂ has a melting point of 3245°C and a relatively low density of 6.1 g/cm³, which makes this a candidate for application to ultrahigh temperature environments over 2000°C. Beside mese properties, ZrB₂ is known to have excellent resistance to thermal shock and oxidation compared with other non-oxide engineering ceramics. In order to enhance such oxidation resistance, SiC was frequently added to ZrB ₂-based systems. Due to nonsinterability of ZrB₂-based ceramics, research on the sintering aids such as B₄C or MoSi ₂ becomes popular recently. In this study, densification and high-temperature properties of ZrB₂-SiC ceramics especially with B₄C are investigated. ZrB₂-20 vol% SiC system was selected as a basic composition and B₄C or C was added to this system in some extents. Mixed powders were sintered using hot pressing (HP). With sintered bodies, densification behavior and high-temperature (up to 1400°C) properties such as flexural strength, hardness, and so on were examined.