Effects of powder processing on colloidal and microstructural characteristics of beta-SiC powders

Three different powder processing methods for introducing sintering aids (yttria and alumina) into a commercial silicon carbide powder are studied: mechanical mixing, heterocoagulation and coprecipitation. The surface characteristics of therawpowders and powder mixtures are analysed by acoustophoretic measurements and compared. The effectiveness of the coprecipitation process for additivation is evaluated by the comparison of ESA measurements and by TEM observations. The powder mixtures are pressureless sintered in argon atmosphere and the microstructure of the sintered materials is analysed. The coprecipitation process allows a higher final density to be obtained in a shorter sintering time, with a finer and more homogeneous microstructure.