Low-temperature fabrication of porous SiC/cordierite composite ceramics from open-celled porous geopolymers

This study demonstrates the successful fabrication of porous SiC/cordierite composite (PSC) ceramics using a geopolymer precursor developed through a combined direct foaming and reactive emulsion templating. This method allows for control over porosity, which significantly affects the material's mechanical properties. The findings indicate that the choice of surfactant, the amount of expired soybean oil, and the curing temperature are critical factors in determining the porosity and pore structure of the SiC/geopolymer ceramic precursor, which subsequently affects its compressive strength. Additionally, higher MgO content and extended holding time promote the formation of the cordierite phase. The resulting PSC ceramics achieved a total porosity of 81.86 vol%, high open porosity (79.78 vol%), compressive strength of 1.96 MPa, and flexural strength of 1.16 MPa. These properties were obtained at a relatively low sintering temperature of 1100 °C for 2h in air without additional sintering aids. The high-temperature oxidation of SiC facilitated in-situ bonding, enhancing structural strength while maintaining high porosity.