Silicon nitride/silicon carbide nanocomposite materials: II, hot strength, creep, and oxidation resistance

The mechanical properties of Si3N4/SiC nanocomposite materials that contained nanosized intercrystalline SiC dispersions that originated from different starting powders and were made via different fabrication routes were studied in the temperature range of 1400°-1550°C. The strength retained at 1400°C was between 70% and about 100% of the room-temperature strength. Both creep and oxidation resistance were very high and were comparable to or better than those of the best Si3N4-based materials published previously. The effect of SiC particles on the creep properties can be understood in terms of a recent model of dilatational creep; however, the model invokes a series of microstructural, micromechanical, and chemical modifications.