Self-ordering behavior of nanoporous anodic aluminum oxide (AAO) in malonic acidanodization

Abstract

The self-ordering behavior of anodic aluminum oxide (AAO) hasbeen investigated for anodization of aluminum in malonic acid(H4C3O4) solution. In the present study it is found that a porous oxide layer formed on thesurface of aluminum can effectively suppress catastrophic local events (such asbreakdown of the oxide film and plastic deformation of the aluminum substrate), andenables stable fast anodic oxidation under a high electric field of 110–140 V and∼100 mA cm−2. Studies on the self-ordering behavior of AAO indicated that the cell homogeneity of AAOincreases dramatically as the anodization voltage gets higher than 120 V. Highlyordered AAO with a hexagonal arrangement of the nanopores could be obtained ina voltage range 125–140 V. The current density (i.e., the electric field strength(E) at the bottom of a pore) is an important parameter governingthe self-ordering of the nanopores as well as the interpore distance(Dint) for a givenanodization potential (U) during malonic acid anodization.