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.
Highlights
Aluminum alloy is of upmost importance for its characteristics including its light weight, high specific strength, excellent electrical and thermal conductivity, as well as being easy to recycle [1,2], but it has downsides, including a low hardness, a high friction coefficient about 0.4–0.8, and high wear rates of about 10−4 –10−5 mm3 m−1 [3,4]
Anodization, a process by which electricity flows through an electrolyte, is widely applied in engineering to intentionally increase the thickness of the oxide layer [5]
After anodic oxidation of the aluminum alloy, ammonium hexafluorosilicate was added to the electrolyte for further electrolysis, and the barrier layer was modified by a step-by-step voltage drop, which is a thinning treatment
Summary
Aluminum alloy is of upmost importance for its characteristics including its light weight, high specific strength, excellent electrical and thermal conductivity, as well as being easy to recycle [1,2], but it has downsides, including a low hardness, a high friction coefficient about 0.4–0.8, and high wear rates of about 10−4 –10−5 mm m−1 [3,4]. The obtained anodic aluminum oxide (AAO) can solve the above problem, to a certain extent, and has been widely used as a promising template, facilitating the growth of adjustable, self-organized, and highly ordered nanodots, nanorods, nanowires, nanotubes, and nanocomposite materials [6,7,8,9]. Song et al reported super slippery porous AAO surfaces have been fabricated by a simple and reproducible method. Such good materials, with excellent anti-corrosion properties, may be potential candidates for metallic application for anti-corrosion and in extreme environments [11]. Muhammad Irfan et al demonstrated that the fabrication of smooth and long Fe nanowire arrays inside nano-channels of an AAO template with a DC electro-deposition method at room temperature was feasible [15]. The deposition experiment of copper nanowires was carried out
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