Oxidation behavior and effect of oxidation on strength of Si3N4/SiC nanocomposites

The oxidation behavior and the effect of oxidation on the flexural strength of Si3N4/SiC nanocomposites were investigated. Parabolic weight gains, wit h respect to the oxidation time, were observed for all the specimens contai ning different amounts of SiC. However, the parabolic rate constant decreas ed with increasing SiC content. The main oxidation product, being in equili brium with SiO2, was Y2Si2O7. The oxidation product became denser and retai ned more crystalline phase as the amount of SiC increased. The flexural str ength of the nanocomposites increased by up to 40%, while that of pure Si3N 4 decreased after oxidation at 1300 or 1400 degrees C for 100 h. This excel lent oxidation resistance of Si3N4 nanocomposite was attributed to the enha ncement of the crystallization of the oxidation product and the grain bound ary phase by the SiC nanoparticles.