Alumina slurry formulation intender for spray‐dried powder production

Abstract

AbstractCeramic powders are used to produce coatings using plasma spray processes. The powder granules are required to have a spherical shape, a mean diameter around 40 µm and, moreover, different densities of the powder must be possible. Alumina powders are obtained by spray drying of concentrated aqueous suspensions of particles (slurries). The suspension must contain high solids loading, be stable during the process and have a relatively low viscosity. The aim of this study was to determine how the properties of aqueous alumina slurries influence the characteristics of granules produced by spray drying. The effects of pH and additives (dispersant and binder) on settling and rheological properties of the alumina slurries were investigated. The curves recorded followed the Casson model in the observed range of shear rate. The Casson yield stress values, τc, and the viscosity values, η were determined and used to evaluate particles interaction in the slurries. The dependence of the yield stress and viscosity was measured as a function of polyacrylate dispersant and binder concentration at pH 4 and 9. The corresponding powders have been characterized on a morphological basis.© 2003 Society of Chemical Industry