Fabrication of High Strength α-SiAlON/BN Composition Ceramics by Hot Pressing

Dense Y3+-dopted alpha-SiAlON/BN composition ceramics were fabricated by hot pressing sintering at 1900 degrees C holding for 1 h, then flexural strength was investigated through three-point bending test at room and 1000 degrees C. The results show that h-BN contributes to the densification of the powder, but which has little affect on the key temperature region of sintering densification of alpha-SiAlON ceramics. When content of BN is lower, which don't affect on the phase transformation of alpha-SiAlON, but when content of BN is higher, besides of major phase alpha-SiAlON, a little of beta-SiAlON were also formed. For the alpha-SiAlON/BN composite ceramics content of 20 wt.% h-BN, the higher flexural strength (room-temperature and 1000 degrees C) is obtained, the formation of beta-SiAlON should be an important reason for the higher strength, more important is, whose flexural strength at 1000 degrees C was higher 50 MPa than at room temperature, the difference of thermal properties between SiAlON and BN should contribute to the improve of high-temperature flexural strength.