Optimization of the rheological properties of alumina slurries for ceramic processing applications Part II: Spray-drying

The present work deals with the preparation of stable alumina, titania and alumina–titania slurries with a high solid content for the production of spray-dried powders. The compatibility of commercial dispersants with various commercial binders, with respect to slurry stability and viscosity, was first studied on alumina slurries. It was shown that binders such as carboxy-methyl-cellulose significantly increase the slurry viscosity whereas acrylic-based binders have a high tendency for foaming. Among the various combinations of the three different commercial dispersants and the four commercial binders studied, it was found that the pair Darvan C–polyethylene glycol (PEG) produced the best results in terms of slurry rheological properties; therefore, this combination was subsequently used for the stabilization of titania and alumina–titania slurries as well. The optimum dispersant–binder concentrations were determined for all three kinds of slurries with the aid of viscosity and zeta-potential measurements. High solid content slurries (70–80 wt.%) of alumina and alumina–titania were spray-dried successfully to produce spherical spray-dried powders with well-defined and uniform size distribution.