Sintering aids for silicon carbide and alumina composite ceramics used as ceramic foam filters

The effect of sintering aids such as quartzite, silica-sol, diatomite, perlite and bentonite were investigated for the sintering characteristics and strength of a silicon carbide-alumina composite ceramic used as a foam filter. The addition of ground quartzite to the composition did not promote the formation of the mullite phase due ra the poor reactivity of SiO2-Al2O3 phases. Hence these samples showed high apparent porosity and poor strength. The addition of silica-sol also did nor have a significant effect on the strength, except that it improved the binding properties the compositions. However, the addition of alkaline based additives like bentonite, perlite and also a fine-particle source of silica in the form diatomite improved the strength by promoting the formation of a mullite phase in the sintered compositions.