SLIP-CASTING PROPERTIES OF SI3N4 WITH Y2O3 AND AL2O3 AS SINTERING ADDITIVES

The effects of particle charging and powder-liquid suspension stabilit y on the slip-casting properties of Si3N4 powder were examined. Y2O3 a nd Al2O3, used as sintering additives, were seen to affect the dispers ion stability of the base material (Si3N4). The zeta potentials of the three powders and the rheological behaviour of the 55 wt% solids-load ed slips, involving known concentrations of a polymeric deflocculant ( Dolapix PC33), showed that the multicomponent system can be dispersed stably within the pH range 9-11. Green compacts, obtained by casting t hese slips into plaster moulds, were found to give densities in the ra nge 50-61% of the theoretical value. (C) 1998 Chapman & Hall.