Improved consolidation of alumina by agarose gelation

A great effort has been devoted to develop low-cost effective forming metho ds for the production of complex-shaped parts. One of the most promising pr ocesses is low-pressure injection moulding in water in which a slurry gelat es in the presence of a thermogelling binder. For this technique agarose ha s been found to be a suitable gelling additive. This work deals with the ma nufacturing of alumina by agarose gelation. For such purpose the rheologica l behaviour of aqueous alumina slips is studied as a function of the polyel ectrolyte concentration, the solid loading and the temperature, in order to reproduce the injection conditions. The gelation behaviour of agarose solu tions is studied from rheological measurements. Two different routes for pr eparing the injection slip are studied, the first by adding agarose as a so lid powder and then heating the slurry, and the second by preparing indepen dently the slurry and the agarose solution and further mixing at temperatur es higher than 60 degreesC. This second route demonstrates to be suitable f or obtaining reliable alumina parts with a green density of 58% of theoreti cal and a sintered density of 98.7% of theoretical, significantly higher th an the values reported in previous works. (C) 2000 Elsevier Science Ltd. Al l rights reserved.