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 degrees-1550 degrees C, The strength retained at 1400 degrees C was between 70% and similar to 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.