Effect of pore size on the flexural strength of porous silicon carbide ceramics

Porous silicon carbide (SiC) ceramics with three different pore sizes (∼7, ∼45, and ∼98 μm) and three different porosities (∼40 %, ∼54 %, and ∼63 %) were prepared from mixtures of SiC, polysiloxane, boron carbide, phenolic resin, and polymer microbeads to investigate the effect of the pore size of porous SiC ceramics on their flexural strength. As the pore size increased from ∼7 to ∼98 μm, the flexural strength decreased from 116.3 to 80.8 MPa at a constant porosity of 40 %, owing to the increased defect size. The typical flexural strengths of porous SiC ceramics fabricated using ∼8 and ∼100 μm templates were 84.9 and 60.9 MPa respectively, at 54 % porosity; the flexural strengths were 58.7 and 43.9 MPa, respectively, at 63 % porosity. These results suggest that depending on the application, the mechanical properties of porous SiC ceramics can be successfully tuned by adjusting their pore size and porosity.