Structural and functional thick ceramic coatings by electrophoretic deposition

Electrophoretic deposition (EPD) has been used in the present work to produce thick ceramic films from nanosized powders on different substrates for structural and functional applications. Hydrothermally synthesized ultra-fine (12 nm) yttrium disilicate (Y2Si2O7) powders were used to create an effective oxidation protection layer of 90 μm thickness on bulk SiC/SiC composite and on woven SiC fibre mats by EPD using a constant voltage of 8 V for 1.5 min. EPD was also used to make lead zirconate titanate (PZT) films on Pt wires for functional applications using hydrothermally synthesized PZT powders with an average particle size of 200 nm. EPD was employed to deposit PZT films directly from the hydrothermal PZT suspensions using a deposition voltage of 4 V for 10 min, leading to the formation of a functional PZT film with a thickness of 5 μm around Pt wire. Titania films on different stainless steel substrates (plates, individual fibres, fibre mats) were also produced by EPD at constant voltage conditions. A nonaqueous suspension of TiO2 nanoparticles in acetylacetone with iodine additions was used for optimal results, which were obtained using voltages of 10 V and deposition times of 2 min. Sintering at 800 °C for 2 h resulted in TiO2 coatings with uniform nanoporous structure, which are interesting for biomedical and photocatalytic applications. The effect of the process parameters such as deposition time and voltage as well as the solids-loading of the colloidal suspensions on the quality, thickness and microstructure of the different ceramic films produced is discussed.