Ceramic forming using enzyme catalyzed reactions

Abstract

A new colloidal processing method for near net shaping ceramic components is outlined. The Direct Coagulation Casting (DCC) process offers the opportunity to produce complex shaped components of high mechanical strength and high reliability at low costs. The process relies on electrostatic stabilized ceramic suspensions and it’s destabilization by time delayed in situ reactions. Enzyme catalyzed reactions 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 enzyme/substrate systems are outlined, suitable for 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 characterized by dynamic viscosity measurements as well as by their compressive strength. The resulting wet green strength is highest for fine particle suspensions with high solids loading. The wet green strength may be increased using alkaline swellable thickeners changing their conformation upon the enzymatic reaction. Ceramic processing routes are reported for alumina powders.