Tuning dendritic structure at nanoporous alumina/aluminium interface for uniform electrodeposition of metals for nanocomposite coatings

Highly ordered nanoporous structures developed by anodising aluminium and its alloys have potential applications in various fields, including wear-resistant coatings in tribology. Filling nanopores with different metals and solid lubricants provide a nanocomposite coating which has a higher hardness. A major hurdle in developing the nanocomposite coatings is that a thick non-conducting barrier layer at the interface between the nanoporous alumina and aluminium substrate. Creating a conducting path at the interface between nanoporous alumina and aluminium without weakening the interfacial strength are expected to have significant advantages for developing tribological coatings. In this work, we systematically modified the interface by the voltage reduction process at different rates and created a dendritic structure at the interface. The dendritic structures growth at the interface is monitored by measuring the capacitance using an LCR meter. The capacitance exponentially decreased with increase in voltage reduction rate. The cross-sectional view of scanning electron microscopy images interface shows that the dendritic structure thickness linearly increases with a decrease in voltage reduction rate. After interface modification, the copper into the nanopores using pulse electrodeposition method. The scanning electron microscopy images show that the capacitance of 0.8-1.2 mu F and similar to 1 V/15 s voltage reduction rate gives nearly uniform filling of nanopores over a large area.