Long-Range-Ordered Anodic Porous Alumina with Reduced Hole Interval Formed in Highly Concentrated Sulfuric Acid Solution

Long-range-ordered anodic porous alumina with a reduced hole interval could be obtained by anodization using highly concentrated H2SO4 solutions. The self-ordering of the hole arrangement of alumina occurred at a low applied voltage of 18 V in highly concentrated H2SO4 solution of more than 6 M, which generated long-range-ordered anodic porous alumina with a hole interval of 45 nm. The ordered composite structure of Co/alumina was also fabricated using the obtained long-range-ordered porous alumina.