Properties of silicon nitride-molybdenum disilicide particulate ceramic composites

The physical and mechanical properties of hot-pressed Si3N4-MoSi2 particulate composites containing 15 and 30 vol% MoSi2 were studied. The average room-temperature four-point bend strength, fracture toughness, and electrical resistivity are 522 MPa, 3.6 MPa&middot √m, and 6.3 × 105 Ω&middotcm for the 15 vol% MoSi2 composite, and 487 MPa, 5.3 MPa&middot √m, and 0.31 Ω&middotcm for the 30 vol% MoSi2 composite. The mechanical properties of the composites are very close to those of hot-pressed Si3N4 ceramics. The high electrical conductivity of the 30 vol% MoSi2 composite was attributed to the percolation effect of MoSi2 particles. Parabolic oxidation behaviors were observed for the 30 vol% MoSi2 composite during the 1200°C long-term oxidation experiments.