The effect of anode surface area on nanoporous oxide formation during anodizing of low purity aluminum (AA1050 alloy)

Leszek Zaraska,Ilona Senyk,Marian Jaskula,Grzegorz D Sulka,Elżbieta Kurowska

doi:10.1007/s10008-013-2215-z

Abstract

Porous anodic alumina layers were obtained by a simple two-step anodization of low purity aluminum (99.5 % Al, AA1050 alloy) in a 0.3 M oxalic acid electrolyte at 45 V and 20 °C. The effect of anode surface area on structural features of nanoporous oxide and process of oxide formation was investigated. An ordered structure composed of nanostripes or nanopores was formed on the Al surface during electrochemical polishing in a mixture of perchloric acid and ethanol. This nanopattern is then replicated during the anodic oxide formation. It was found that the pore diameter, interpore distance, and porosity increase slightly with increasing surface area of the aluminum sample exposed to the anodizing electrolyte. On the other hand, a slight decrease in pore density and cell wall thickness was observed with increasing surface area of the sample. The detailed inspection of current density vs. time curves was also performed. The obtained results revealed that the higher surface area of the anode, the local current density minimum, was reached faster during first step of anodization and the increase in current density corresponding to the pore rearrangement process was observed earlier. Finally, a dense array of Pd nanowires (∼90 nm in diameter) was synthesized by simple electrodeposition of metal inside the channels of through-hole nanoporous anodic alumina templates with relatively large surface areas (4 cm2).

Highlights

During the recent years, fabrication of 1D nanostructures such as nanowires and nanotubes has become a subject of great scientific interest due to extremely promising properties of these materials and their potential applications in many different areas [1]
We demonstrated a successful fabrication of Pd nanowire arrays using nanoporous anodic alumina membranes with relatively large surface areas
The effect of anode surface area on the nanoporous oxide formation during anodic oxidation of low-purity aluminum was studied in detail

Summary

Introduction

Fabrication of 1D nanostructures such as nanowires and nanotubes has become a subject of great scientific interest due to extremely promising properties of these materials and their potential applications in many different areas [1]. Nanoporous alumina templates can be synthesized by a simple and cost-effective two-step anodic oxidation of aluminum in acidic electrolytes [4]. This process, which does not require any sophisticated and expensive equipment, results in formation of aluminum oxide layers with a regular, dense structure of hexagonally arranged nanopores. Structural features of nanoporous alumina membranes such as pore diameter, pore-to-pore distance, thickness of the oxide layer, etc. Some detailed information on the fabrication of anodic alumina membranes and influence of anodizing conditions on structural features and nanopore arrangement of anodic alumina can be found in our previous works [5,6,7,8]

Objectives

Results

Conclusion