Crack healing and strengthening of SiC whisker and ZrO2 fiber reinforced ZrB2 ceramics

Crack healing behavior of ZrB2 based ultra-high temperature ceramics reinforced by ZrO2 fibers and SiC whiskers was investigated by oxidizing a pre-cracked sample. A Vickers indentation was introduced into the sample and the crack was healed at temperature ranging from 800 to 1400 °C, with 1200 °C being the optimum healing temperature. The crack was completely healed with oxidation products consisting of ZrO2 and SiO2, resulting in a recovered strength ~95 MPa higher than that of polished specimens. The good crack-healing ability would make this composite highly useful as it could heal defects and flaws autonomously in practical applications. Our findings may also provide a new insight into improving the strength and structural integrity of ZrB2 based ultrahigh-temperature ceramics.