Effect of TiO2 on the interaction of dehydroxylated kaolinite with Al(OH)3 gel in relation to mullitisation

A precursor powder for mullite was prepared in the active state by the aqueous phase interaction of dehydroxylated kaolinite and aluminium hydroxide gel deposited from Al(NO3)3 solution. The magnitude of sintering, as well as the sintered properties of the compacted mass, was found to be influenced by the doping agent, TiO2. TiO2 played a positive role in the formation of mullite. With increase in TiO2 content, porosity of the sintered compacts decreased and bulk density increased. TiO2 probably formed a liquid phase under the experimental conditions (up to 1600 C) which promoted sintering and therefore no titania-bearing crystalline phases were observed in the XRD diagram of the sintered compacts, although the batches contained a higher proportion of alumina compared to conventional mullite composition. 15 refs.