Abstract
The Si3N4, /SiC composites were prepared by hot-pressing the Si-C-N powder pre-cursors from CVD. Transmission electron microscopic observations indicated that SiC particles finer than -0.1μ m were dispersed mainly within the matrix grains whereas large SiC dispersions were located at the grain boundaries. No apparent impurity phase was observed at the interface of Si3N4, and SiC. The coefficient of thermal expansion of the composites increased with SiC content according to the composite law, while the thermal conductivity decreased up to about 20 vol% SiC and increased with the increase of SiC dispersion. Thus, the slightly decreased-thermal-shock-fracture-resistance, ΔTc, was observed for the composites as compared with pure Si3N4, although the fracture strength (also toughness) was improved significantly by the SiC dispersions.
