Anodic Oxide Film Breakdown Mechanism And Nanopore Formation Mechanism

The anodic alumina membrane was fabricated by anodizing under different conditions. The growth process of anodic alumina membrane was studied systematically by voltage-time (v-t) curves and current-time (i-t) curves. The surface and cross section of anodic alumina membranes were characterized by field emission scanning electron microscopy (FESEM). The transforming mechanism between electronic current (je) and ionic current (jion) and the influence of anion-contaminated alumina (ACA) layer on the pore development was studied.First, the forming processes of barrier anodic alumina membrane and the dielectric breakdown mechanism were analyzed in different current densities, different electrolytes and different gas pressures. Three stages were divided from its growth to breakdown, including oxide membrane growth, oxygen evolution and dielectric breakdown. The reason of dielectric breakdown was that the oxide membrane reached critical thickness and the electronic current appeared. Second, the mixed oxide membrane was fabricated in the mixed electrolyte by potentiostatic anodizing and galvanostatic anodizing. The pores development mechanism was studied through anodizing curves and the SEM images. The results exhibit that the structure of mixed oxide membrane is in contact with barrier membrane and porous membrane, and the formation of pores is affected by the oxygen evolution. Third, we produced anodic oxide membrane in weak acid, alkaline electrolyte and low concentration electrolyte.We di covered nano-channels both on the surface and the cross section, and the inside nano-channels were larger than outside. The results revealed that the nano-channels grew from the bottom of the oxide to the surface. At last, we studied the effect of current density and gas pressure on the nano-channels by analyzing the surface morphologies of the oxide membrane. The ACA and oxide film layers were characterized by EDX. In conclusion, the types of anodic oxide membrane are related with the thickness of ACA. Moreover, the ACA and oxygen bubble mould effect play an important role in the formation of nano-channels.