Ceramic forming using enzyme catalyzed reactions

A new colloidal processing method For near net shaping ceramic components i s outlined. The Direct Coagulation Casting (DCC) process offers the opportu nity to produce complex shaped components of high mechanical strength and h igh reliability at low costs. The process relies on electrostatic stabilized ceramic suspensions and it's destabilization by time delayed in situ reactions. Enzyme catalyzed reacti ons may be used either to create salt at a constant pH or/and to shift the pH of the suspension to the isoelectric point of the powder. Different enzy me/substrate systems are outlined, suitable far different ceramic powders. The reaction kinetics of the liquid - solid transition can be controlled by the enzyme concentration and temperature. The mechanical properties of the resulting viscoelastic ceramic green bodies in their wet state are charact erized by dynamic viscosity measurements as well as by their compressive st rength. The resulting wet green strengths highest for fine particle suspens ions with high solids loading. The wet green strength may be increased usin g alkaline swellable thickeners changing their conformation upon the enzyma tic reaction. Ceramic processing routes are reported for alumina powders. ( C) 1999 Published by Elsevier Science S.A. All rights reserved.