Extrusion characteristics of alumina-aluminium titanate composite using boehmite as a reactive binder

Alumina-aluminium titanate composite was fabricated through paste extrusion using boehmite gel as a binder. The rheological characteristics of alumina paste containing various amounts of boehmite binder were studied at differ ent shear rates. The results of investigations on the development of torque , yield stress, viscosity and fluidity are presented. In general, Bingham t ype plastic behavior was observed. Alumina pastes containing 18.5 vol.% of boehmite exhibits adequate plasticity and fluidity for extrusion. The torqu e value for this composition is 68 kPa at shear rate 28.5 s(-1). The viscos ity curves of alumina pastes showed "shear thinning" flow behavior. The mix ture of 54.15 vol.% alumina and 18.5 vol.% boehmite resulted in 61% of theo retical green density on extrusion. These conditions were extended to synth esis of alumina-aluminium titanate composites, and the extrusion was carrie d out using 18.5 vol.% boehmite. Aluminium titanate was synthesized through sol-gel method and dispersed uniformly in alumina matrix through colloidal process. The composites could be sintered at 1400 degreesC to 98% of its t heoretical value. The SEM fractograph of sintered composite showed reasonab ly dense, uniformly distributed grains in the order of 2-3 mum. The present study shows that boehmite binder phase yields good workability for extrusi on and contributes high green and sintered densities to the composites. (C) 2000 Elsevier Science Ltd. All rights reserved.