Investigations on colloidal and dry formed alumina parts under pressure and pressure-less conditions

Abstract

Pressure assisted casting of advanced ceramics is an emerging preparation technique as it permits using a colloidal slips in shaping under pressure. Application of pressure provides flexibility in forming of complex shapes in combination with high homogeneity, superior green density, strength and high productivity. Current study compares conventional slip casting (CSC), pressure slip casting (PSC) and cold isostatic pressing (CIP) used for preparation of alumina green bodies. Since particle size is a limitation in PSC process due to the defined pore size of the mould, the same starting alumina powder obtained by mixing of powders with two different average particle size (7 ?m and 1.43 ?m) in the proportion of 65:35 was employed in all three processes. Green densities of 65%TD at 35 bar in case of PSC and 66%TD at 1200 bar after CIP were obtained; however, density of the CSC samples was only 50%TD. Flexural strength and fractographic studies were carried out and correlated with the respective processes. The samples were also sintered at 1600 ?C to evaluate their sinterability.