Study on direct current electro-deposition of copper nanowires in anodic alumina membrane pores

Abstract

Aluminum alloy plays an important role in industrial applications, but has a high friction coefficient and a high wear rate. On the basis of anodic oxidation treatment on an aluminum alloy surface, copper nanowires are deposited into the anodic alumina membrane pores by direct current (DC) electrolytic treatment to prepare a composite alumina membrane, which significantly improves the tribological properties of the aluminum alloy surface. In this process, in order to obtain a highly-ordered nanoporous alumina membrane with a thin enough barrier layer for further processing, after the first anodic oxidation in phosphoric acid (0.3 mol/L), the obtained alumina membrane is modified by anodizing it in a phosphoric acid-ammonium hexafluorosilicate bath, in combination with a step-by-step voltage drop without oxide removal. By this method, the resistance of the modified alumina membrane is also reduced greatly, which facilitates the deposition of copper nanowires in the sulfate bath. It is found that the composite alumina membrane filled with copper nanowires has a low friction coefficient of about 0.25 and effectively improves the friction condition, giving the surface a self-lubricating property.