Abstract
Si3N4/ 5 wt% SiC composites with Y2O3 and Al2O3 as sintering additives were fabricated by the gas pressure sintering. The influence of ultra-fine SiC particles addition to the silicon nitride on microstructural evolution and mechanical properties with starting powder was investigated. The added ultra-fine SiC particles were distributed within the Si3N4 grains and at the grain boundaries. The fraction of SiC particles located at grain boundaries was much higher in the specimen prepared from β-Si3N4 powder than that in the specimen prepared from α-Si3N4 powder. When the β-Si3N4 was used as a starting powder, the strength of Si3N4/SiC remained room temperature strength at temperature 1000oC. It is considered that the improvement in the high temperature strength of composites was attributed to the SiC particles located at the grain boundaries.
