Microstructure of the BNf/Si3N4 Composites Prepared by LPCVD

Abstract

The BN/Si 3 N 4 composites were prepared by LPCVD using SiCl 4 -NH 3 -Hr-Ar as precursor at 950°C. The microstructure of the BN/Si 3 N 4 composites was examined by scanning electron microscopy. The phase identification of the nanometer Si 3 N 4 was confirmed by X-ray diffraction. The morphology and growth mechanism of the Si 3 N 4 matrix were investigated using chemical reaction kinetics and supersaturation-condensation-fusion mechanism. Because of the mismatching of the coefficient of the thermal expansion and the poor wettability between the coating and the substrate, the coatings could be easily flaked away. The internal surface of the Si 3 N 4 shell was very smooth, which proved the poor wettability. The external surface of the Si 3 N 4 shell was composed of the amorphous spheroid particles, which proved the S-K growth model.