Creep behavior of a carbon-derived Si3N4/SiC nanocomposite

The creep behavior of a silicon nitride–silicon carbide nanocomposite prepared by in situ utilizing C+SiO2 carbothermal reduction is investigated at the temperature from 1200 to 1450 °C in bending under stresses ranking from 50 to 150 MPa in air. The stress exponents are in the interval from 0.8 to 1.28 and the apparent activation energy is 480 kJ/mol. No cavitation was found and grain-boundary sliding accommodated by diffusion through the intergranular glassy phase is considered to be the main creep mechanisms. The higher creep resistance of the nanocomposite compared with the creep resistance of a monolithic silicon nitride with the same amount of sintering additive can be explained by the presence of the intergranularly located SiC nano particles which limit grain boundary sliding and improve viscosity of the intergranular phase due to its changed chemical composition.