Self-ordered Porous Alumina Fabricated via Phosphonic Acid Anodizing

Abstract

Self-ordered periodic porous alumina with an undiscovered cell diameter was fabricated via electrochemical anodizing in a new electrolyte, phosphonic acid (H 3 PO 3 ). High-purity aluminum plates were anodized in phosphonic acid solution under various operating conditions of voltage, temperature, concentration, and anodizing time. Phosphonic acid anodizing at 150-180 V caused the self-ordering behavior of porous alumina, and an ideal honeycomb nanostructure measuring 370-440 nm in cell diameter was successfully fabricated on the aluminum substrate. Conversely, disordered porous alumina grew at below 140 V, and anodizing at above 190 V caused local thickening due to oxide burning. Two-step phosphonic acid anodizing allows the fabrication of high aspect ratio ordered porous alumina. HPO 3 2-anions originated from the electrolyte were incorporated into the porous oxide during anodizing. Consequently, a double-layered porous alumina consisting of a thick outer layer containing incorporated HPO 3 2-anions, and a thin inner layer without anions was constructed via phosphonic acid anodizing.

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al2O3

“…1,2 For instance, porous Al 2 O 3 is widely applied as a catalyst support because of its thermal stability and heat conductivity. [3][4][5][6][7] Dense and compact Al 2 O 3 layers (i.e. without porosity and thus, with a much lower specific surface area) are also of great industrial importance, particularly, for protective and decorative coatings.…”

Fabrication techniques enabling ultrathin nanostructured membranes for separations

“…Anodization most commonly uses very thick layers or foils of a metal as starting material, which sets a trade‐off between thickness and stability. Mechanically stable anodized membranes are usually thick , resulting in very high aspect ratios that significantly compromise on efficient mass flow across the membrane, hindering its potential as separation media. The successful anodization of metallic films deposited on Si wafers and even glass has been reported, which increases the versatility of anodized materials since it expands the processing catalog to conventional silicon technologies.…”

Fabrication of copper nanowires via electrodeposition in anodic aluminum oxide templates formed by combined hard anodizing and electrochemical barrier layer thinning

“…Currently, numerous new strategies are being researched, including anodizing in novel electrolytes [5][6], in viscous electrolytes [7], with additives [8][9],or by changing current or voltage during the anodizing process resulting in a formation of 3D patterns [10][11].…”