Effect of Different Sintering Additives on the Reaction-Bonded Si3N4/SiC Composite Ceramics

Effect of different sintering additives on reaction-bonded Si3N4/SiC composite ceramics under pressureless was investigated. Si3N4/SiC composite ceramics were sintered at the temperature 1550 °C under nitrogen atmosphere with different sintering additives Y2O3, Y2O3:Al2O3=1:1, Y2O3:Mg2AlO4 :Mg3(Si4O10)(OH)2: SiO2=5:2:1:1, and ZrO2 by using SiC with different particle sizes, and Si as raw materials. The phases, microstructure and mechanical property were characterized by XRD, SEM, and compressive strength test. The results demonstrated that when the particle gradation consisted of silicon carbide of 74 μm (5 wt.%), 44 μm (10 wt.%) and 0.5 μm(30 wt.%) and silicon powder of 74 μm (42 wt.%), the more dense samples with the bulk density of 2.43 g/cm3 and the higher compressive strength of 324 MPa could be obtained when Y2O3 was used as sintering additives.