Preparation of High-Purity Glasses and Advanced Ceramics Via EPD of Nanopowders

Abstract

AbstractFor shaping of bulk ceramic components and coatings electrophoretic deposition (EPD) is an interesting process especially for nanopowers, where high deposition rates can be reached. As for industrial applications aqueous systems are of main interest, problems with decomposition of water have to be solved. These problems with gas formation at the electrodes can be solved by using a oxidizable electrode or electrolyte, a membrane cell, or utilizing non-linear effects with pulsed AC currents. For nanosized particles EPD seems to be one of the most favorable processes because the deposition rate is independent of particle size in contrast to slip casting. Thus homogenous compacts with the comparatively highest relative green densities can be achieved with nanopowders or mixtures of coarser particles and nanopowders. In this case very high green densities up to 80% could be achieved reducing the linear shrinkage of the compact. This is of great importance for near net-shaping. Furthermore, the EPD process offers the possibility of a large variety of modifications like electrophoretic impregnation (EPI), where particles are deposited inside a porous structure. Thus all kinds of gradient materials and fiber composites can be prepared. The combination of EPD with electrodeposition or in-situ electrochemical reactions offers further possibilities, which have to be investigated for potential applications. Examples are given for the preparation of transparent silica glass, alumina and zirconia optoceramics and, finally, the perspectives of EPD coatings with self-adjusted thickness are shown.KeywordsGreen DensitySilica GlassLinear ShrinkageElectrophoretic DepositionLaser PrinterThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.