Colloidal processing of Al2O3-based composites reinforced with TiN and TiCparticulates, whiskers and nanoparticles

A colloidal processing route has been developed for the preparation of dens e and homogeneous Al2O3-TiN/TiC composites. The dispersion and rheological properties of mixtures of TiN or TiC particulates and Al2O3 particles were investigated using electrokinetics and steady-shear rheology. We found that well-dispersed aqueous suspensions with ion; viscosity; could be: prepared by; adding a poly(acrylic acid) dispersant;Ind controlling pH in the alkal ine range. This processing scheme was also suitable for preparation of whis ker and nanoparticle composite suspensions. The alumina-based composite sus pensions with a secondary-phase concentration of 25 vol.% were freeze-granu lated and hot-pressed, and the resulting bodies were fully densified with w ell-dispersed secondary phases. Homogeneous Al2O3-TiN nanoparticle composit es could only be prepared with additions of up to 5 vol.% nanoparticles; hi gher additions resulted in agglomeration and subsequent grain growth of the nanoparticles. (C) 2001 Elsevier Science Ltd. All rights reserved.