Investigation of the electrophoretic deposition behaviour of non-aqueous ceramic suspensions

The topic of the investigations was the electrophoretic shaping of AlN, SiC and Al2O3, respectively, using ethanolic suspensions of the powders. Suitable organic additives were chosen for achieving an effective suspension stabilisation and a sufficiently high electrophoretic mobility of the particles, which are the basic requirements for a successful electrophoretic deposition. Most of the EPD experiments were carried out in the direction of the gravitational force. Either the voltage or the current was kept constant during the deposition. In the case of the EPD of AlN, the dependence of the deposit mass on the experimental parameters has been investigated in detail and explained on the basis of changes in the effective electric field strength. Several factors influencing the effective field strength are discussed in this paper. By EPD from the different suspensions, green bodies with monomodal pore size distributions reflecting a high homogeneity of the particle packing were produced. It was shown that by the simultaneous deposition of non-oxide powders and sintering additives from suspensions with high solid contents deposits with a homogeneous distribution of the sintering additive can be obtained, whereas in diluted suspensions different electrophoretic mobilities cause a separation of the components.