Effect of hydrolysis on the colloidal stability of fine alumina suspensions

This paper investigates the effect of hydrolysis and the formation of hydrated polycations on the colloidal stability and rheological properties of fine alumina suspensions. This is an important phenomenon in colloidal processing of advanced ceramic materials and nanocomposite materials from fine particles. The aging process and the formation of large polycations in the solution are monitored by nuclear magnetic resonance, and the aggregation rate and viscosity of the suspension are measured under similar conditions. It is observed that aging under acidic conditions increases colloidal stability against aggregation in dispersed suspensions, and reduces the viscosity in flocculated suspensions. This behavior corresponds well to the formation of large polynuclear species through hydrolysis. It is suggested that the hydrated polycations significantly modify the total interaction energy between two particles at short separation distances.