Formation mechanism of alumina nanotubes and nanowires from highly ordered porous anodic alumina template

Abstract

Alumina nanotube (ANT) and nanowire (ANW) arrays were produced from highly ordered porous anodic alumina (PAA) by etching in phosphoric acid and subsequent thermal treatment. The domain structures that have small sizes provide more boundaries and break the hexagonal symmetry of the PAA template, thereby inducing star-like splitting modes. Using very thin PAA films, ANTs and their arrays are fabricated, whereas ANWs and their arrays are produced when using thick films. This is due to the thin wall between nanopores. Our results provide some mechanistic and fundamental information pertaining to the fabrication of nanostructures via a PAA template.

Growth of alumina oxide nanowires in an aluminum anodization process

“…The electric field is not present in the case [16] of etching PAAO using a phosphoric acid solution, and a nonuniform electric field develops in the peripheral zones of the sample in this paper. This indicates that pores and nanowires can form when corrosive solutions make contact with aluminum or alumina oxide.…”

“…Previous studies confirm the formation of alumina oxide nanowires via the immersion of PAAO into various kinds of acid or alkaline solutions [14,16]. Nanowires, which grew as a consequence of the treatment using 10 wt% sulfuric acid solution, were concentrated on top of the undissolved porous alumina oxide layers.…”

“…Alumina oxide nanotubes with many branches were fabricated via the anodization of aluminum on a silicon substrate in dilute sulfuric acid [13]. Alumina oxide nanotubes and nanowires were produced by chemically etching PAAO membranes either in sodium hydroxide solution [14,15] or in phosphoric acid solution [15][16][17][18][19][20]. However, to the best of our knowledge, there are few reports of the formation of alumina oxide nanowires in organic acid solution.…”

Formation of dense alumina nanowires from anodic alumina membranes

“…In this sense, several groups of authors reported different alumina nanostructures that were fabricated via a simple etching method in NaOH [4][5][6][7] or in a chromic and phosphoric acid solution [1,7]. Alternatively, Mei et al [8] produced alumina nanotube and nanowire arrays by etching the AAO in 5%w phosphoric acid solution and subsequent thermal treatment. The diameter of the nanowires is about 30-40 nm, which corresponds to the thickness of the wall between the nanopores.…”

Synthesis and characterization high purity alumina nanorods by a novel and simple method using nanocellulose aerogel template

“…These templates could be nanoporous membranes or nanofibers. In this context, aerogels could be used as facile highly porous templates for nanostructured alumina [9, 10, 11, 12].…”