Fabrication of SiC foam ceramics at a low sintering temperature by adding fly ash

Silicon carbide (SiC) foam ceramics (SFC) have been widely used in various industries owing to their excellent mechanical properties at elevated temperatures. However, fabricating a qualified product at a low sintering temperature is a challenge because of the strong covalent nature of the Si–C bond. In this study, we successfully fabricated a SFC at a low sintering temperature (1150 °C) by adding fly ash (FA) using the polyurethane replication method. The effects of sintering temperature and FA content on the mechanical performance of the ceramics were systematically studied. The phase composition and microstructure of the SFC were characterized using X-ray diffraction and scanning electron microscopy. At 1150 °C, an SFC with 30 wt% FA exhibited optimal properties, i.e., a porosity of 64.43%, bulk density of 0.89 g/cm3, and bending strength of 8.34 MPa. As a sintering aid, FA promoted the formation of the mullite phase at low sintering temperatures, which enhanced the anticorrosion and anti-cracking performance of the SFC. Therefore, adding FA to SiC significantly lowers the sintering temperature and reduces the fabrication cost associated with the SFC. Consequently, its commercial application is considerably enhanced.