Improved thermal shock resistance of SiBCN ceramics with in-situ HfB₂ addition

High-temperature impacts can easily break SiBCN's dense oxide film, making the ceramic matrix vulnerable to sustained damage in harsh conditions. In this paper, to enhance the high-temperature stability, HfB₂/SiBCN composite ceramics were prepared by introducing nano-HfB₂ into the SiBCN matrix. To evaluate their thermal shock resistance, the residual strength was measured after water quenching. The ultrahigh-temperature phase HfB₂ was able to transform the original SiO₂ into a dense and homogeneous HfO₂-HfSiO₄ oxide layer to prevent further oxidation. Introducing HfB₂ resulted in a substantial increase in the residual strength of HfB₂/SiBCN composite ceramics, in which the residual strength of the 30 % HfB₂-containing SiBCN ceramics was increased by 97 MPa compared with that of pure SiBCN ceramics when the temperature difference was up to 1200 ℃.