In-situ fabrication of catalytic metal oxide films in microchannel by plasma electrolytic oxidation

In an attempt to develop new methods to fabricate in-situ catalytic layers for microreactor, the plasma electrolytic oxidation (PEO) process for coating deposition was utilized and the growth behavior of the oxide film was studied. PEO coatings containing TiO2-Al2O3 composite oxides were formed on the aluminum substrate engraved with a microchannel on the surface, and the effects of applied voltage on the microstructure and composition of the obtained coatings were investigated. It was found that the morphology and composition of the layers were strongly influenced by process parameters, high applied voltage gave rise to the amount of Ti in the layers, and decreased the porosity of the coating surface. Moreover, the comparison of the coatings formed inside and outside the microchannel clearly indicates a significant change in their microstructure, which could be explained by the shielding and mass transfer effects induced by the deep and narrow channel.