Near Net Shaping with Bimodal Powders on Shaped Membranes via EPD

The electrophoretic deposition (EPD) is a very promising process for shaping compacts, especially for nanopowders. Up till now EPD is not used on a large-scale production of ceramic products. Additionally, the higher cost of nanopowders was also a barrier for the development of new products. As the deposition rate at EPD is independent of particle size, it is an ideal process for shaping compacts of powder mixtures with nanopowders. Silica and zirconia powders were used as model systems to demonstrate the advantages of EPD. Applications might be the preparation of high-purity silica glass for processing of semiconductors and zirconia ceramics for near net-shaped dental crowns. In both cases the optimum green density was achieved for approx. 10 % addition of nanopowders to a coarser matrix powder. The compacts were homogenous. Alternatively, compacts of different powders can be prepared in a two-step process. Examples are shown for the electrophoretic impregnation (EPI) and a reactive forming of nanoparticles inside the pore volume of a compact consisting of coarser particles.