Particles cellulation composite (PCC): Dispersion morphology of SiC particles in Si3N4/SiC composites

Dispersion morphology of fine SiC particles in Si3N4/xSiC (x = 0, 10, 20, 30wt%, average size: 0.03 micro m) composites was statistically analyzed, and typical properties of the composites such as creep, electric and thermal conductivity were investigated. The dispersion morphology of SiC particles was analyzed by observing the ECR-plasma etched surface of the sintered composites using scanning electron microscopy. SiC particles in Si3N4/SiC composites were distributed both within Si3N4 grains and on Si4N4 grain boundary, but 90% or more of them was located on the grain boundary. For the composites with 20--30 wt%SiC, the SiC particles on the grain boundary clearly formed a three-dimensional network structure surrounding a few or more Si3N4 crystalline grains. A Si3N4/SiC composite with a three-dimensional network structure of SiC particles, named particles cellulation composite (PCC), was artificially made by pressing the granulated Si3N4 powder (less than 500 micro m diameter) discontinuously coated with SiC particles (average size: 0.4 microm). The creep deformation of PCC was reduced to about 60% of that of the composites with SiC particles randomly dispersed. Electrical and thermal properties were also improved. These results suggest that the formation of three-dimensional network structure by the second phase particles in a composite would considerably improve its mechanical property as well as electrical and thermal properties