PROPERTIES OF WATER-BASED SLURRIES FOR FABRICATION OF CERAMIC-METAL COMPOSITES BY SLIP CASTING METHOD

The main advantage of ceramic-metal composites is the increase of fracture toughness of the brittle ceramic matrix. The slip casting method gives the possibility to obtain products of complicated shapes without green machining. In the work results concerning colloidal and rheological aspects of ceramic-metal composite fabrication via the slip casting method are presented. Slurry consisted of ceramic (alpha-Al2O3) and nickel powder suspended in water with addition of deflocculants composition (citric acid and diammonium citrate), surface-active agents and binder. Ceramic and metallic powders show great differences in electrokinetic behavior, which cause that the heteroflocculation effect in the suspension can take place. In order to investigate the particles interaction characteristics, the zeta potential of each powder was examined. The zeta potential measurements were performed for diluted suspensions as a function of pH. Rheological measurements of the slurries were performed. Although surface of alumina was modified, so that the electrokinetic behavior resembled one of nickel, it turned out that the presence of nickel particles has great influence on the slurry properties. The change of rheological properties for slurries containing nickel particles results probably from strong interaction between alumina and nickel particles.