The effect of the particle size and the morphology of alumina powders on the processing of green bodies by electrophoretic deposition

The electrophoretic deposition (EPD) method was investigated for the preparation of compacts from nanosized alumina powders. Ethanol suspensions of commercially available nanosized transition alumina and α-alumina powders were used. In addition, submicron powders were also considered for comparison. Besides the influence of operational pH change, the influence of the addition of three different surfactants – two branched polyethylene imines with molecular masses 1800 and 10,000, and citric acid—on the zeta-potential of the particles in ethanol and afterwards on the EPD was investigated. The packing density of the green parts prepared by the EPD of nanosized α-alumina powders at 30 V/cm was low (the green density was 27 vol. % of the theoretical density—TD), and a bimodal pore size distribution was observed. In contrast, the packing density in deposits made with the transition alumina nanopowder was much higher (the green density was 42 vol. % of the TD) and a monomodal distribution of pores was observed. In general, for all the deposits made from nanosized alumina powders, the particle-packing density was found to be lower than for those made from the submicron alumina powders (a green density equal to 59 vol. % of the TD).