Effect of TiO2 and ZrO2 on sintering of sillimanite

Sintering of sillimanite from Kerala (India) beach sand was studied. Titania, zirconia and a combination of the two were used as sintering aids. With titania as the additive, the formation of fine needles of mullite was observed, whereas, in the case of the other two additives, mullite was plate-like. It is suggested that the relatively large amount of liquid-phase formation during sintering is responsible for the formation of acicular mullite. The average value of flexural strength of sintered sillimanite with the various additives varies from 45.2 MPa to 93.5 MPa