Microstructures and Fracture Characteristic of Si_3N_4-O'SiAlON Composites using Waste-Si-Sludge

摘要

Si_3N_4-O'SiAlON composites using waste-Si-sludge WAS FABRICATED BY gas-pressure-sintering (GPS) process at 1950 deg C for 3.5h. 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 Si_2N_2O and Y_2Si_2O_7 phase were also detected in the reaction-bonded Si_3N_4 (RBSN) although main components were alpha- Si_3N_4, beta- Si_3N_4 and residual Si phase. In the post-sintered body by GPS, no residual Si, alpha- Si_3N_4, Si_2N_2O and Y_2Si_2O_7 phases were detected except the beta- Si_3N_4 and O'SiAlON. The grain growth of rod-like Si_3N_4 grains was inhibited by the dispersion of fine O'-SiAlON particles. The fracture toughness and strength of Si_3N_4-O'SiAlON composites were 5.6 MPa centre dot m~(1/2) and 456 MPa, respectively.