Densification of alumina produced by urea formaldehyde sol–gel polymeric route

Abstract

α-Alumina powder was prepared in uniform spherical particles via urea formaldehyde sol–gel polymeric route using aluminium chloride as precursor. Alumina was both tetrahedrally and octahedrally coordinated within the structure of the resin. The α-phase is formed in the powder calcined at 1000°C when the number of Al 3+ substituted in the resin structure reached 2 moles equivalent oxide. The octahedrally coordinated aluminium form nucleation sites that act as seeds for the formation of α-alumina in powders calcined at 700°C. Bodies processed by cold isostatic press (CIP) under 300 and 600 Mpa from this powder show densification approaching to about 94% total density TD when fired at 1550°C . Grain growth was observed in microstructure of bodies fired at 1700°C and densification was lowered to 90.9% TD.