Effects of sintering temperature and V2O5 additive on the properties of SiC-Al2O3 ceramic foams

In this study, a series of SiC-Al2O3 ceramic foams (SACFs) were fabricated from the powders of commercial silicon carbide and fused white corundum by polymeric foam replication method combined with reaction sintering process. Effects of sintering temperature (1250 °C-1350 °C) and addition amounts of V2O5 (0-3 wt%) on the sintering properties and post-sintering properties of as-prepared SACFs such as appearances, microstructures, phase compositions, apparent porosity, bulk density, cold compressive strength and thermal shock resistance have been investigated. During the sintering process, SiC was oxidized in air and formed SiO2, then part of as-formed SiO2 reacted with Al2O3 to produce Al6Si2O13 ceramic phase. The mechanical properties of as-prepared SACFs were found to be remarkably increased due to the increase of the sintering temperature and the introduction of V2O5. The phase transformation towards mullite was also found to be promoted, and the mullitization temperature was reduced because of the formation of Si-rich liquid phase due to the addition of V2O5. The improvements in sintering properties, cold compressive strength and thermal shock resistance of as-prepared SACFs were attributed to the formation of mullite and silica ceramic bonding phases in the ceramic matrix during the sintering process in air. The SACFs doped with 1 wt% V2O5 and sintered at 1450 °C for 2 h, achieved their maximum cold compressive strength of 2.45 MPa, and the apparent porosity was still 69.08%.