Aqueous Ceramic forming of Si3N4 using Direct Coagulation Casting

Abstract

Direct Coagulation Casting is a novel near-net-shape method for forming ceramic green bodies from homogeneous high-solids-loaded particle suspensions. It is based on the principle of the in situ coagulation of a stable concentrated suspension, poured into a nonporous mold, via a time-delayed chemical reaction which leads to its destabilization. Silicon nitride powder aqueous dispersion to achieve near net shape forming and high density of green body was investigated. A high state of silicon nitride dispersion was achieved by using Tetraethylammoniumhydroxid(TEAH), which allowed us to obtained stable higher than 50vol%. The reaction kinetics of liquid-solid transition can be controlled by aluminum acetate. The result greenbodies have no shrinkage after drying 2hours at room temperature, also 2hour in a dry oven and achieve high packing green body density.