Microstructural evolution and performance of carbon fiber-toughened ZrB2 ceramics with SiC or ZrSi2 additive

ZrB2-SiC/ZrSi2 ceramics containing 30 vol% carbon fiber (C-f) additive were fabricated by hot pressing at low temperature (1500 degrees C) using submicron ZrB2 powders, and their microstructural evolution and performance were investigated. The addition of SiC or ZrSi2 significantly reduced the onset sintering temperature and enhanced the densification of ZrB2. ZrB2-ZrSi2-C-f showed poor performance owing to the serious fiber degradation, while the fiber degradation was effectively inhibited in ZrB2-SiC-C-f resulting in high fracture toughness, substantial fiber pull-out, and non-brittle fracture mode for such material. The critical thermal shock temperature difference of ZrB2-SiC-C-f was up to 741 degrees C, significantly higher than those of ZrB2-SiC/ZrSi2 and ZrB2-ZrSi2-C-f. Moreover, this composite displayed a good oxidation resistance at 1500 degrees C in air.