RHEOLOGY OF ALUMINA SOLS

Alumina sols were obtained by hydrolysis of aluminium sec-butoxide according to Yoldas method. Peptization was carried out with two different quantities of HCl and at two different temperatures. The four sols obtained were stored at 40-degrees-C, and their rheological behaviour was determined for times to 1 year. Rheological measurements were fitted to a slightly modified Casson model. Evolution of adjusting parameters, yield stress, consistency index and flow index, with aging time, are discussed. Samples with higher HCl give a yield stress from the day of preparation. Samples with lower HCl display a Newtonian behaviour initially and shear thinning behaviour with increasing viscosity with aging time.