Improved oxidation resistance properties of Si3N4/O′-SiAlON composite ceramics by a repeated sintering method

Si3N4/O'-SiAlON composite ceramics with superior oxidation resistance properties were fabricated by a repeated sintering method. The effects of sintering time on the phase evolution, microstructure, and oxidation resistance properties of the Si3N4/O'-SiAlON composite ceramics were investigated. The results indicated that the content of the O'-SiAlON phase and the densification of Si3N4/O'-SiAlON composite ceramics increased after two-time sintering. Furthermore, the thickness of the oxide layer of the Si3N4/O'-SiAlON composite ceramics after oxidation at 1100-1500 degrees C for 30 h was not significant. Compared to the oxidation weight gain after the one-time sintering process, the oxidation weight gain of Si3N4/O'-SiAlON composite ceramics was 0.432 mg/cm(2) after two-time sintering when oxidized at 1500 C for 30 h, which was reduced by 43.3%. The mechanism of the improved oxidation resistance properties was ascribed to the formation of more O'-SiAlON and the enhancement of the densification.