DISPERSION OF 3 CERAMIC POWDERS IN A SLURRY - THE AL2O3-ALN-SIC MIXTURE

This work presents, in a first stage the influence of aluminium nitrid e (AIN) addition to a well dispersed alpha-alumina slurry, and in a se cond stage the influence of silicon carbide (SiC) phase to a Al2O3-AlN slurry. We have shown that the acid-basic character of polymer disper sants and powder surface play a major role in the adsorption phenomena of dispersant onto a surface: an acidic polymer will have a better af finity with a basic powder surface than with an acidic surface and vic e versa. This study has allowed to determine the dispersion conditions of each powder in an azeotrope medium (methyl ethyl ketone-ethanol) w ith phosphoric ester (PE) on Al2O3 powder and polyvinylpyrrolidone (PV P) on SiC and AlN powders. If, for two components (Al2O3-AlN) the best conditions of dispersion lead to a homogeneous material, it is not th e same for three-powder mixtures (Al2O3-AlN-SiC). (C) 1996 Elsevier Sc ience Limited.