Anodic Alumina Nano-hole Formation Process

Traditional theory claims that the main mechanism for the formation of porous anodic alumina (PAA) is acidic electricfield-assisted dissolution, but it cannot give a reasonable explanation for the structure of hexagonal cells and hemispherical pore base in PAA. In order to study the growth mechanism of PAA, we chose several electrolytes to perform aluminum anodization. The anodization process and PAA films were characterized by means of Voltage-time curves. The result indicates that acidity of electrolyte is not the necessary condition. We also find the regular porous in NH4H2PO4 electrolyte.PAA can also be observed in barrier film-forming electrolyte (ammonium sebacate solution in ethylene glycol) and the pore channels will be much denser with the H₃PO₄ increasing. Augment of constantαand j₀ induces O₂ separating out. Besides we present a new growth model and formation mechanism of PAA, i.e. oxygen bubble mould effect results in regular channels of PAA films. We also give a new explanation for the V-t curve of anodization.Oxygen bubble mould effect can explain the formation mechanism of the plum blossom patterns on PAA and serrated nanopore. The serrated nanopore arrays in PAA could also be used in a wide range of future nanostructure fabrications.