Electrophoretic deposition from aqueous suspensions for near-shape manufacturing of advanced ceramics and glasses - applications

Due to high deposition rates and the avoidance of inflammable, often hazardous organic solvents EPD from aqueous suspensions is a fast and low-cost shaping technique for ceramics and glasses. Since the deposition rate is independent of particle size EPD has an outstanding ability for the shaping of nano-particles. In this paper the shaping of complex silica glass and zirconia components, like tubes or structured parts by means of the membrane method is shown. Three-dimensional shaped porous polymer moulds were used as ion-permeable deposition surface. To enable near-shape manufacturing, mixtures of nanosized and microsized particles were electrophoretically deposited. No size-dependent separation was observed. Due to the very high green density of these green bodies (up to 84% of the theoretical value) shrinkage could be reduced to 4.7%. Not only oxide ceramics but also silicon carbide was deposited from aqueous suspensions. Apart from bulk SiC, protective coatings with a thickness of app. 60 mum were applied on top of CFC substrates by EPD. Good adhesion was observed and no cracking occurred. Furthermore, electrophoretic impregnation was used for the modification of porous green bodies. Thus silica glasses with graded density and pore size as well as functionally graded composites were prepared. (C) 2004 Kluwer Academic Publishers.