EFFECT OF BORON-NITRIDE ON THE PHASE-STABILITY AND PHASE-TRANSFORMATIONS IN SILICON-CARBIDE

High-resolution transmission electron microscopy has been used to stud y the effect of hexagonal boron nitride (h-BN) on the stability of SiC polytypes in Si3N4-particulate-reinforced SIC composites in which h-B N particles appeared as a trace contaminant. In contrast to previous t ransmission electron microscopy work on SiC-BN composites, our results imply that there is no clear preference for a particular SIC polytype to be stabilized by h-BN nearby, Instead, we propose that previous ob servations suggesting that the 3C SIC polytype is stabilized by h-BN c an be simply explained in terms of it being stabilized indirectly by n itrogen arising from BN dissociation during processing.