ZrO2-induced crack-healing mechanism of ZrB2-SiC-Graphite composite in high temperature atomic oxygen environment

摘要

The ZrO2-induced crack-healing mechanism of ZrB2-SiC-Graphite (ZSG) composite is investigated under high temperature atomic oxygen atmosphere, which characterizes the real condition of hypersonic flight. This differs greatly from the borosilicate glass-induced crack-healing mechanism in previous studies. The cracks are healed limitedly in high temperature atomic oxygen condition with a 39.09% maximum improvement in residual strength compared to the pre-cracked specimens. The crack-healing is induced by ZrO2, and the crack-healing mechanism involves three main aspects: A. Local particle rearrangement, which is induced by expansion from the chemical reaction (ZrB2 -> ZrO2), the phase transition (t-ZrO2 -> m-ZrO2), and the thermal expansion. B. The crack volume filling by ZrO2 driven by the liberation of the reaction gases. C. Diffusion controlled sintering around the ZrO2 sintering temperature. The spontaneous crack-healing ability in high temperature atomic oxygen atmosphere is helpful to improve the reliability of ZSG composites in service. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.