Electrophoretic deposition of sol-gel coating comprising alumina and boehmite for organic-inorganic hybrid film

Organic-inorganic hybrid films were prepared by electrophoretic deposition (EPD) with plate-shaped alumina particles dispersed in a sol gel binder, which is prepared by the hydrolysis and condensation reaction of methyltrimethoxysilane (MTMS) in the presence of colloidal boehmite. A layered orientation of the hybrid films was prepared as an crack-free dense films in which plate shaped alumina particles are uniformly distributed in the sol gel binder. The microstructure and the electrical and thermal properties of the hybrid films were compared for various operating conditions of the EPD process, such as deposition time and slurry composition. The hybrid films were prepared by EPD of the sol gel binder with 10-30 wt% plate alumina particles at an applied voltage of 10 V for 1-10 min. The EPD coatings with an increasing coating thickness exhibited a higher electrical insulation. The coating of alumina and boehmite allows higher electric insulation than that of alumina and silica in the same thickness condition. The breakdown voltage was observed to be as high as over 6 kV for a thickness of 110,am when the colloidal boehmite was used to prepare sol-gel binder, which was achieved from boehmite sol gel binder with 10 wt% Al2O3 by EPD at applied voltage of 10 V for 10 min with condition of a distance of 2 cm between electrodes.