Effect of pre-oxidation on strength and thermal shock behavior of ZrB ₂-SiC-graphite ceramic composites

A novelty technique, namely, pre-oxidation, has been proposed to improve the strength and thermal shock behavior of ZrB ₂-SiC-graphite ceramic composites, which is a promising candidate for ultra-high temperature ceramics (UHTCs) in aerospace engineering. The composite is pre-oxidized at temperatures of 900°C and 1100°C for 1 h and 3 h in air. A theoretical model considering surface heat transfer has been given and analyzed. A water-quenching technique is adopted at different temperatures from 300°C to 600°C in order to investigate the thermal shock behavior of pre-oxidized composites. The critical thermal shock temperature improves more than 40% after pre-oxidizing at 1100°C for 3 h. However, the composites strength is not improved as a result of the insensitivity to surface defects.