Three-Dimensional Networked Nanoporous Anodic Alumina Films with Vertical and Transverse Pores Fabricated on Al With Different Purity

Abstract

Three-dimensional networked porous anodic alumina (PAA) nanostructures, which consisted of perpendicular cylindrical stem pore arrays (170–310 nm) and periodical transverse branched pores in 20 – 80 nm across the pore walls, were successfully fabricated from industrial pure Al materials of Al-1100 (99%), Al–1N30 (99.3%), and Al-1050 (99.56%) by constant-potential anodizing in phosphoric acidic solutions at 110–190 V. The formation of transverse branched pores was predominantly dependent on the purity of Al materials, and irrespective of the anodizing voltages and solution concentrations. The formation of the transverse branched pores can be mainly ascribed to the anodic and/or the chemical dissolution of impurities like Cu, Fe, Zn, Mg, and Mn components included in the Al base materials, and the corrosive nature of phosphoric electrolytes driven by the high electrical field during the anodization.