A QUANTITATIVE-EVALUATION OF MICROSTRUCTURE IN SI3N4/SIC PLATELET AND PARTICULATE COMPOSITES

A microstructural evaluation of Si3N4 containing 15-40 vol% SiC platelets or particles is presented. All the composites were fully densified by hot isostatic pressing without external addition of sintering aids. Size, morphology, surface roughness and crystal structures of the SiC phases before and after sintering were compared in order to discuss the structural stability of the reinforcements up to 2050-degrees-C in Si3N4 matrix. Morphology and phase characteristics of the grain boundary are also discussed. In addition, homogeneity and isotropy of the composite bodies were quantitatively examined by image analysis techniques and it was recognized that, for a similar degree of dispersion, the characteristic of three-dimensional randomness could be preserved only at V(f) < 30% in the composites containing high aspect ratio platelets.