Oxide ceramics with unidirectional pore channels by electrophoretic deposition

Disc-shaped alumina, alumina-toughened zirconia, and mullite green bodies, few millimetres in thickness, with parallel aligned pore channels were produced by an electrophoretic deposition method that takes advantage of the gas generation by electrolysis in aqueous suspensions. Appropriate amounts of an anionic polyelectrolyte, chosen on the basis of zeta potential measurements, and ammonia solution were used as additives. Adding ammonia promoted the gas evolution at a given polyelectrolyte amount. The electrolyte content influenced the porosity values and the diameters of the pore channels. Volume fractions of the pore channels in the sintered bodies up to 40% were determined by computed tomography in combination with 3D image analysis. The maxima of the pore diameter distributions of the sintered samples were in the range between 200 and 300 μm.