Self-ordered hard anodization in malonic acid and its application in tailoring alumina taper-nanopores with continuously tunable periods in the range of 290-490Â nm

Self-ordered anodic alumina taper-nanopores with continuously tunable periods in the range of 290-490 nm have been realized. An intrinsic self-ordered hard anodization regime for malonic acid with the ability to generate the larger and continuously modulated periods of cylindrical nanopores at the higher potentials of 150-230 V was demonstrated. To avoid the burning so as to ensure stable malonic acid hard anodization at the higher potentials, we adopt a simple but powerful strategy, anodizing at a stepwise potential-rising model and simultaneously enhancing the heat-dissipating ability of cooling waterflow. The self-ordering of porous alumina films in malonic acid was studied under different potentials and anodizing time, where current-time transients were also monitored. As a result, pre-patterned aluminum foils with different periods of ordered nanopits, formed after removal of porous oxide layer, can be used for the in situ growth of taper-nanopores, which feasibility has been well verified by four examples with the periods of 300 nm, 358 nm, 385 nm and 432 nm, after preliminarily grasping the growth and etching dynamic of alumina nanopores.