Effect of template size on microstructure and strength of porous silicon carbide ceramics

Porous silicon carbide (SiC) ceramics with different pore size were prepared from SiC powders, an aluminum yttrium garnet (Y3Al5O12, YAG) as a sintering additive, and three different sizes of templates (polymer microbeads) by a sacrificial template technique. Their microstructure and mechanical strengths were evaluated as a function of template size, i.e., pore size. Porosity of these porous SiC ceramics increased with increasing the template content, regardless of template size. Pore size was proportional with the template size. The growth of faceted grains was accelerated with increasing the template size. Both flexural and compressive strengths decreased with increasing the porosity whereas both strengths increased with decreasing the template size, i.e., pore size. Typical flexural and compressive strengths of the porous SiC ceramics fabricated using 8 mu m-templates were similar to 55 MPa and similar to 240 MPa at similar to 45% porosity, respectively. (c) 2008 The Ceramic Society of Japan. All rights reserved,