Pore-size control in porous SiC ceramics prepared by spark plasma sintering

Porous SiC ceramics were prepared at 19002000° C without holding time at 50200° C/min under a pressure of 15MPa in Ar with Al₂O ₃, Y₂O₃, and AlN additives by spark plasma sintering. The effects of heating rate, heating temperature, and sintering additive on the porosity, pore size, microstructure, and flexural strength of the porous SiC ceramics were investigated. As the heating rate increased, the size of SiC grains in the samples decreased, the porosity increased, and the flexural strength decreased. The strength of the samples increased with an increase in heating temperature. The growth of SiC grains was suppressed in the sample prepared at 1950°C, and the sample had both high porosity (42%) and high strength (95 MPa). In the samples prepared with AlNY₂O ₃ and AlNAl₂O₃ additives at 1950°C the porosities were 3239%. The addition of AlN to Y₂O₃ and Al₂O₃ additives resulted in the inhibition of grain growth and a decrease in the pore size of the samples. The maximum strength was 167MPa in the prepared porous SiC ceramics