High-resolution interface analysis of SiC-whisker-reinforced Si₃N₄ and Al₂O₃ ceramic matrix composites

Whisker/matrix interfaces between β-SiC whiskers and β-Si₃N₄ or α-Al₂O₃ matrices in composites were examined by high-resolution electron microscopy (HREM), and electron energy loss (ELS) and energy dispersive X-ray (EDS) spectroscopies. Most whisker/matrix interfaces were crystalline, with whiskers directly bonded to matrix crystals. Some whisker/matrix interface regions contained amorphous thin films and these occurred more often in the Si₃N₄ composite, which contained sintering additives, than in the Al₂O₃ matrix composite, which did not. No evidence for light element segregation at crystalline whisker/matrix interfaces was detected by ELS or EDS at 5 nm spatial resolution. Impurities were concentrated in glassy regions in matrix grain boundaries, triple junctions, or at infrequent whisker/matrix interfaces containing amorphous films.