Effect of Starting SiC Particle Size on Nitridation and Strength of Silicon Nitride-Bonded Silicon Carbide Ceramics

Effect of starting SiC particle size on nitridation rate and flexural strength of Si3N4-bonded-SiC (SNBSC) ceramics was investigated by using SiC particles of different size (similar to 200 mu m, similar to 100 mu m and similar to 45 mu m). The specimen prepared from smaller SiC particles resulted in higher nitridation rate after nitridation at 1450 degrees C, owing to the lower packing density in green body. The flexural strength showed maxima after 1-h nitridation for all specimens and then decreased with prolonged nitridation because of local densification-induced pore coarsening. The specimen prepared from smaller SiC particles showed better flexural strength because of smaller pore size and partly higher nitridation rate in the specimen. A maximal flexural strength of 29 MPa was obtained in the specimen with a density of 2.04 g.cm(3), which was prepared from 45 mu m-SiC particles.