HYDROLYSIS-ASSISTED SOLIDIFICATION (HAS) - A NEW SETTING CONCEPT FOR CERAMIC NET-SHAPING

A new, hydrolysis-assisted solidification (HAS) concept for net-shapin g of ceramic green parts from aqueous suspensions is presented The pro cess is based on thermally activated hydrolysis of aluminium nitride p owder added to highly loaded ceramic suspensions. During hydrolysis of AlN, water is consumed and ammonia is formed, which in turn may incre ase the pH of the suspension. Both mechanisms can be used to increase the viscosity and ultimately to set a cast or injection-moulded cerami c green belly. Different ceramic suspensions containing various amount s of AlN powder were prepared at ambient temperature without increasin g their viscosity and subsequently set in heated impermeable moulds. T he setting time ranged from a few seconds to a felt, minutes, dependin g on the solids loading, AlN addition and the thickness of the green b ody. (C) 1996 Elsevier Science Limited.