Formation of unidirectional nanoporous structures in thickly anodized aluminum oxide layer

摘要

A series of anodic aluminum oxide(AAO) was grown on the commercially pure 1050 aluminum sheet by controlling electrolyte temperature(2-15 ℃) and anodizing time(0.5-6 h),using a fixed applied current density of 3 A/dm2 in diluted sulfuric acid electrolyte.A crack-free thick AAO with the thickness of 105-120 μm and containing unidirectional nano sized pores(average pore diameter of 5-7 nm) is successfully achieved in the specimens anodized for 2 h,irrespective of electrolyte temperature.When anodizing time reaches 6 h,very thick AAO with the thickness of 230-284 μm is grown,and average diameter of unidirectional pores is in the range of 6-24 nm.The higher values in both the AAO thickness and pore diameter are attained for the specimens anodized at higher temperatures of 10-15 ℃.A crack is observed to exist in the AAO after anodizing up to 4 h and more.A higher fraction(more than 9%) of the crack is shown in the specimens anodized at higher temperatures of 10-15 ℃ for 6 h and a considerable amount of giant cracks are contained.