ALUMINA MATRIX CERAMIC-NICKEL COMPOSITES WET PROCESSING

The main advantage of ceramic-metal composites is the increase of fracture toughness of the brittle ceramic matrix. The slip casting moulding method is widely used in the ceramic industry, which gives the possibility to obtain products of complicated shapes without green machining. Good quality and homogeneity of powder consolidation is crucial in the ceramic and ceramic matrix composite fabrication process as it influences the properties of the material. In the case of such complex systems as powder mixture dispersions in a liquid medium (slurry), it is indispensable to investigate the phenomena taking place at the solid-liquid interface which determines dispersion stability and governs the interaction characteristics between the particles of different types (ceramic and metallic). In the paper, the results concerning ceramic matrix ceramic-metal composite fabrication via the slip casting method are presented. The following materials were used: alumina powder (TM-DAR, Tamei Japan) of average particle size D-50 = = 0.21 mu m, specific surface area of S-BET = 14.5 m(2)/g and density of d = 3.8 g/cm(3), and nickel powder (Sigma-Aldrich) of average particle size D-50 = 2.17 mu m, specific surface area of S-BET = 2.1 m(2)/g and density d = 8.9 g/cm(3). Ceramic and metallic powders show great differences in electrokinetic behavior, which can cause the heteroflocculation effect to take place in the suspension. In order to investigate the particles interaction character, the zeta potential of each powder and its mixture was measured. The zeta potential measurements were performed on diluted suspensions that contained deflocculants, as a function of pH. Additionally, the particle size distribution of the diluted slurries was conducted in order to investigate the agglomeration characteristics. Rheological measurements of the slurries were performed. Furthermore, the chosen physical and mechanical properties of sintered bodies were examined (i.e.:bending strength, hardness and fracture toughness)