Variation of the surface state of α-alumina through hydrothermal treatments

α-alumina is a widely used oxide. Yet its interface with water is very sensitive to physical and chemical treatment and a review of the literature showed that the measured Iso Electric Point (I.E.P.) can vary from 4 to 9. A unique powder of high purity grade (99.99% α-Al2O3) was used as the starting material for three different treatments (ageing in cold and hot water and acid leaching). Various surface states could then be produced and characterized through Infrared spectroscopy and potentiometric measurement. The hydrothermal treatment produced an hydrated aluminium hydroxyde gibbsite–bayerite) on the surface of the particles. This revealed the presence of an amorphous layer on the untreated particles. This work belongs to a more general study on the relation between surface states and redispersion properties of dry powders.