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

A microstructural evaluation of Si3N4 containing 15-40 vol% SiC platel ets 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 Si C 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 bound ary are also discussed. In addition, homogeneity and isotropy of the c omposite bodies were quantitatively examined by image analysis techniq ues and it was recognized that, for a similar degree of dispersion, th e characteristic of three-dimensional randomness could be preserved on ly at V(f) < 30% in the composites containing high aspect ratio platel ets.