title: Ultra-high density single nanometer-scale anodic alumina nanofibers fabricated by pyrophosphoric acid anodizing.
abstract: Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (10(10) nanofibers/cm(2)) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices.
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kikuchi
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishinaga
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Nakajima
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kawashima
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Shungo
authors.initials: S
authors.lastname: Natsui
authors.affiliation: Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Norihito
authors.initials: N
authors.lastname: Sakaguchi
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Ryosuke O
authors.initials: RO
authors.lastname: Suzuki