Preparation of Ideally Ordered Anodic Porous Alumina by Prepatterning Process Using a Flexible Mold

Ideally ordered anodic porous alumina with controlled interpore distances was formed by fabricating a resist mask using a flexible mold and subsequent anodization. Prior to forming the resist pattern on the surface of an Al substrate, Al was pre-anodized at 10 V to prepare the fine porous structure, which acts as a resist adhesive layer. After the formation of the resist mask using a flexible mold, an arranged array of cavities with Al exposed at the bottom was formed by the selective dissolution of the oxide layer at resist openings. The subsequent anodization of the sample with the cavity array generated ideally ordered anodic porous alumina because alumina holes were formed at the bottom of cavities during anodization. This process allows the preparation of ideally ordered anodic porous alumina even on a curved Al surface owing to the flexibility of the mold. In addition, this process can also be applied to the preparation of an ideally ordered anodic porous alumina with a large sample area because the Al substrate can be patterned without high pressure. The obtained sample can be used for various applications requiring an ideally ordered hole array structure.

Effects of size and position of an unconnected aluminum electrode on bipolar anodization in an AC electric field

The effects of the size and position of an aluminum bipolar electrode (BPE) on the uniformity of formation of anodic porous alumina in an alternating current electric field were investigated. Anodized specimens were dyed, and the resistance was measured after the specimens were anodized again. Phenomena observed during film formation indicated that the BPEs had unique potential distributions that strongly depended on their length and width. The color variations and electrical resistance of the BPEs were symmetrical and varied from the centers of the BPEs to their ends. When multiple BPEs were processed at the same time, their position in the non-uniform electric field was demonstrated to be an important factor for controlling the uniformity of film formation. The best results were obtained when the BPE was placed at the center of the defined space.

Small-Diameter Magnetic and Metallic Nanowire Arrays Grown in Anodic Porous Alumina Templates Anodized in Selenic Acid

Despite the introduction of selenic acid for anodic porous alumina (APA) preparation with small nanopore diameters (< 20 nm), no attempt has been made to use it in the fabrication of small-diameter magnetic and metallic nanowire arrays. In this paper, considering the high cost of selenic acid, it has been attempted to initially use oxalic acid in preparation of an ordered pattern in the first anodization step, and then employ selenic acid for the second anodization step by matching the appropriate voltage. By investigating the nanopore formation pattern in both acids, it was shown that the nanopores formed in the selenic acid had considerably smaller diameter (13 nm) than that of oxalic acid (35 nm). Under optimized conditions of electrodeposition, various metals were then grown in the selenic APA templates in order to fabricate nanowires with small diameters. The pore filling percentage and crystalline properties were also investigated.