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

alpha-Alumina powder was prepared in uniform spherical particles via urea f ormaldehyde sol-gel polymeric route using aluminium chloride as precursor. Alumina was both tetrahedrally and octahedrally coordinated within the stru cture of the resin. The alpha-phase is formed in the powder calcined at 100 0 degrees C when the number of Al3+ substituted in the resin structure reac hed 2 moles equivalent oxide. The octahedrally coordinated aluminium form n ucleation sites that act as seeds for the formation of alpha-alumina in pow ders calcined at 700 degrees C. Bodies processed by cold isostatic press (C IP) under 300 and 600 Mpa from this powder show densification approaching t o about 94% total density TD when fired at 1550 degrees C. Grain growth was observed in microstructure of bodies fired at 1700 degrees C and densifica tion was lowered to 90.9% TD. (C) 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved.