Preparation of reaction-formed porous SiC ceramics

The carbon foam template was produced from the mixture of mesophase pitch and 55% Si particles(mass fraction). The SiC porous ceramics were fabricated by infiltrating Si into the carbon foam template at 1500°C for 1-6 h in the vacuum furnace under argon atmosphere. The micrograph and identify phase of porous SiC ceramics were observed by means of SEM and XRD respectively. Moreover, the mechanism of reactive infiltration of molten Si into carbon foam was also discussed. The results show that the microstructure of porous SiC ceramics is identical with carbon foam template. The bending strength of porous ceramics is increasing first and then decreasing with holding time prolonged at 1500°C, however, the porosity is reverse. The porous SiC ceramics obtained at 1500°C for 4h is composed of the major phase β-SiC. The bending strength and porosity are 26.2 MPa and 45% respectively. Both the outer molten Si and inner Si of carbon foam react with C simultaneously to form SiC, and then bonds together to form densest porous SiC ceramics.