Thermogelation of Al2O3/Y-TZP films produced by electrophoretic co-deposition

There is a growing interest to develop reliable, economic and environmentally-friendly methods for manufacturing thin and thick coatings and layered systems. Electrophoretic deposition has demonstrated to be a suitable technique for manufacturing laminates and coatings. For thick films, the adhesion to the substrate and the shape retention become important problems that lead to low density, cracking, and heterogeneous surfaces. To overcome these problems, a new idea is proposed consisting in the formation of a thick deposit by EPD in water and its immediate consolidation by thermogelation of polysaccharides, which is introduced in the suspension and forms a gel structure on cooling during withdrawal of the substrate from the suspension bath. In this work the parameters involved in the electrophoretic codeposition of two phase suspensions (Al2O3/Y-TZP) containing carrageenan, on nonporous graphite substrates are studied. Dense self-supported films with thickness between 10 and 500 pm are obtained after a thermal treatment in which the graphite substrate burns out and the subsequent sintering cycle. The performance of gel-deposition is studied as a function of the concentration of carrageenan, the solids loading and the electrical conditions. (C) 2003 Elsevier Ltd. All rights reserved.