Dispersion and reaction sintering of alumina–titania mixtures

Alumina–aluminium titanate (A–AT) composites are typically produced either by mixing the alumina matrix powder with already formed aluminium titanate or by reaction sintering of alumina and titania powders. Reaction-sintered materials usually exhibit limited final density and extensive microcracking. This paper describes the preparation of A–AT nanocomposites by slip casting and reaction sintering, using aqueous suspensions of submicrometre-sized alumina and nanometre-sized titania at a respective weight ratio of 87:13, which is typical for plasma-sprayed coatings. The colloidal stability of aqueous suspensions of the two individual powders and of their respective mixtures was determined first, measuring zeta potential and rheological behaviour as a function of deflocculant content and sonication time. The bimodal distribution yielded green relative densities of up to 70% of theoretical density. Dynamic and static sintering studies showed that aluminium titanate had already formed at 1400 °C.