Microstructure formation of porous silicon carbide ceramics during β-α phase transformation

The effect of particle size and initial powder phase on the microstructure of porous SiC ceramics was investigated. When β-SiC powder was used as a starting material, porous SiC ceramics were formed by rapid grain growth of α-SiC during the β-α phase transformation. As the particle size of the initial powders decreased, β-α SiC phase transformation and rapid grain growth of α-SiC occurred earlier. Grain and pore size of SiC porous ceramics can be controlled by the addition of α-SiC seed. Grain and pore size decreased as the concentration of α-SiC seed increased. The bending strength of porous SiC ceramics did not depend on pore size.

Porous SiC was fabricated by a β-α SiC phase transformation using β-SiC powders. The effect of particle size and initial powder phase on the microstructure of porous SiC ceramics was investigated. The microstructure of SiC porous ceramics depends on the characteristics of the initial β-SiC powder used, such as particle size and preexisting α-SiC concentration. As the particle size of the raw materials decreased, rapid grain growth accompanied by β-α SiC phase transformation occurred earlier, which resulted in an interconnected porous network structure with huge plate-like α-SiC grains. The addition of α-SiC seed increased the number of nucleation sites and, consequently, the final α-SiC grain size and pore size were reduced. The porosities of the specimens were 44.5-46.5% and the bending strengths were 33-36 MPa.181