2002 Volume 43 Issue 1 Pages 19-23
Si3N4–O’SiAlON composites using waste-Si-sludge was fabricated by gas-pressure-sintering (GPS) process at 1950°C for 3.5 h. The percent nitridation of waste Si compacts showed a lower value than that of using commercial Si powders caused by the high contents of oxygen in the waste Si particles. Some amounts of Si2N2O and Y2Si2O7 phases were also detected in the reaction-bonded Si3N4 (RBSN) although main components were α-Si3N4, β-Si3N4 and residual Si phases. In the post-sintered body by GPS, no residual Si, α-Si3N4, Si2N2O and Y2Si2O7 phases were detected except the β-Si3N4 and O’SiAlON. The grain growth of rod-like Si3N4 grains was inhibited by the dispersion of fine O’-SiAlON particles. The fracture toughness and strength of Si3N4–O’SiAlON composites were 5.6 MPa·m1⁄2 and 456 MPa, respectively.