Electrophoretic deposition and physicochemical characterization of Al 2 O 3 -NiO composite materials

Abstract

Al 2 O 3 -NiO composites were fabricated by electrophoretic deposition (EPD). Suspensions were prepared from the mixture of Al 2 O 3 and NiO powder in a mixed ethanol-water electrolyte and were stabilized with acetic acid. The effects of the NiO content, sintering temperature and the deposition parameters such as the EPD applied voltage and deposition time on the coating weight, microstructure and crystallinity of final composites were studied. Due to the positive charge of Al 2 O 3 and NiO in suspension in the mixed ethanol-water sol-vent, samples were deposited on the cathode and they were not affected by the possible solvent electrolysis. Coatings with defect-free mi-crostructure were then obtained. These investigations have revealed that the deposits weight gain increases linearly with NiO content and theirs thickness was controlled by adjusting the NiO content and/or the time of the deposition. By increasing NiO content, the distribution of NiO nano-particles in Al 2 O 3 matrix became more homogenous forming thereby an interconnected network like-microstructure which inhibits the grain growth of Al 2 O 3 . This illustrates clearly the advantage of EPD for the synthesis of Al 2 O 3 -NiO particles. XRD studies have revealed that apart from Al 2 O 3 and NiO, a cubic nickel spinel (NiAl 2 O 4 like phase is formed in the Al 2 O 3 -NiO composite. The increase of the applied voltage has resulted in a serious reduction of the deposit weight gain and also to the degradation of their microstructures par-ticularly when the NiO content is lower than 40%.