Fabrication and characterization of cordierite-bonded porous SiC ceramics

A reaction bonding technique was used for the preparation of cordierite-bonded porous SiC ceramics in air from α-SiC, α-Al2O3 and MgO, using graphite as the pore-forming agent. Graphite was burned out to produce pores and the surface of SiC was oxidized to SiO2 at high temperature. With further increasing the temperature, SiO2 reacted with α-Al2O3 and MgO to form cordierite. SiC particles were bonded by the cordierite and oxidation-derived SiO2. The reaction bonding characteristics, phase composition, open porosity, pore size distribution and mechanical strength as well as microstructure of porous SiC ceramics were investigated. The pore size and porosity were strongly dependent, respectively, on graphite particle size and volume fraction. The porous SiC ceramics sintered at 1350 °C for 2 h exhibited excellent combination properties, the flexural strength of 26.0 MPa was achieved at an open porosity of 44.51%.