Effect of hydrolysed aluminium treatment on rheological characteristics ofalpha-alumina slurries

This paper describes the process for the hydrolysed aluminium treatment (HA ) on alumina surface and its influence on the rheological characteristics o f alumina slurries. Three different commercial grade aluminas were provided with the surface treatment with hydrolysed aluminium using aluminium nitra te and hexamethylenetetramine (HMTA) under controlled conditions. The HA tr eatment increased the concentration of Al-OH surface sites resulting in hig her H+ adsorption on the alumina surface. A highly concentrated (> 55 vol%) electrostatically stabilized alumina slurry was prepared from HA treated a lumina powders. The rheology of such slurry was studied and the results on the viscosity and yield stress are presented. The alumina slurries followed the Casson Model flow behaviour. The 'wet' and 'flow' behaviour of the alu mina with and without HA treatment was also studied and the results are com pared. The surface treatment showed the advantage of maintaining low viscos ity and yield stress of alumina slurries even at higher solids loading (> 5 5 vol%) that are prepared in the acidic aqueous medium. The results on visc osity and yield stress were compared with that of the polyelectrolyte dispe rsed system. (C) 2001 Kluwer Academic Publishers.