Structural engineering of nanoporous anodic aluminium oxide by pulse anodization of aluminium

Abstract

Nanoporous anodic aluminium oxide has traditionally been made in one of two ways: mild anodization or hard anodization. The first method produces self-ordered pore structures, but it is slow and only works for a narrow range of processing conditions; the second method, which is widely used in the aluminium industry, is faster, but it produces films with disordered pore structures. Here we report a novel approach termed "pulse anodization" that combines the advantages of the mild and hard anodization processes. By designing the pulse sequences it is possible to control both the composition and pore structure of the anodic aluminium oxide films while maintaining high throughput. We use pulse anodization to delaminate a single as-prepared anodic film into a stack of well-defined nanoporous alumina membrane sheets, and also to fabricate novel three-dimensional nanostructures.

Fabrication of Anodic Porous Alumina by Squaric Acid Anodizing

“…1 summarizes the anodizing electrolytes that have been reported to date for porous alumina fabrication. Sulfuric (H 2 SO 4 ), oxalic ((COOH) 2 ), and phosphoric (H 3 PO 4 ) acids are well-known, self-ordering anodizing solutions for porous alumina fabrication, and highly ordered porous alumina can be obtained by anodizing in these solutions at constant voltages of 18-25 V, 40 V, and 160-195 V, respectively [24][25][26][27][28][29]. Malonic acid (HOOC-CH 2 -COOH) and tartaric acid (HOOC-(CHOH) 2 -COOH), typical dicarboxylic acids, have also been reported to support the fabrication of highly ordered porous alumina fabrication at 120 V and 195 V, respectively [30,31].…”

“…Lee et al studied the rapid formation of ordered porous alumina by a hard anodizing procedure involving a powerful cooling stage and obtained an ultra-high aspect ratio (>1,000) of anodic porous alumina by anodizing in oxalic acid at 120-150 V [24]. They also reported the structural control of porous alumina by the pulse anodizing of aluminum and obtained well-defined three-dimensional nanoporous alumina membranes [26]. The fabrication of self-ordered anodic porous alumina at a previously unutilized ordering voltage was achieved by Almasi-Kashi et al in a mixture of sulfuric and oxalic acid electrolytes [37].…”

Smart Bioinspired Nanochannels and their Applications in Energy‐Conversion Systems

“…Ion and electron beams are often used to create single or multiple nanochannels in ultrathin free standing silicon, [19] silicon nitride, [20] silicon oxide, [21] and graphene membranes. [22] Furthermore, other methods such as electrochemical etching, [23] anodic oxida tion, [24] and laser technology [25] have been adopted depending on the type of materials and application requirements. The ion track etching technology, which can accurately control the diameter and shape of the nano channels, is a fascinating method to prepare polymeric nanochannels.…”

Morphological and chemical characterization of highly ordered conical-pore anodic alumina prepared by multistep citric acid anodizing and chemical etching process

“…It is also possible to design a various shape of pores in AAO by application of a pulse anodization methods [19,20]. Recently, AAOs with tapered pores and pitch size in the range of 100-490 nm were fabricated [21][22][23][24][25][26][27].…”