Porous alumina based ordered nanocomposite coating for wear resistance

Controlled Growth of Highly Aligned Cu Nanowires by Pulse Electrodeposition in Nanoporous Alumina

“…For instance, we have found that same pulse duration with slightly lower potential than the negative pulse, could prevent the uneven growth. 35 Once the porous template was filled with CuNWs, the current increased suddenly as shown in Figure 3(b). This can be used to define the end point of the nanowire deposition.…”

“…This non-conducting barrier layer in-between the porous alumina and the aluminium substrate is then reduced using the stepwise reduction of voltage just after the second anodisation in the same electrolyte as shown in Figure 2(b). Yadav et al 35 had found that the dendritic structure formed by reducing the voltage stepwise by 1 V/15 s resulted in more than 95% of pore barrier layers being removed over a 10 mm × 10 mm area. Choosing a linear reduction of voltage offers fine control over the resulting dendritic structure at the pore base.…”

“…Choosing a linear reduction of voltage offers fine control over the resulting dendritic structure at the pore base. 35 In order to remove the irregularities in the dendritic structure a mild chemical etching was done in 0.63 M C 2 H 2 O 4 solution at 25 C after the voltage reduction. This process is different from the one reported by Nielsh et al 16 wherein the pore widening is carried out before barrier thinning.…”

“…The positive pulse was applied first which resulted in copper growing uniformly in the pores. 35 Initially, during the dendritic filling the current fluctuated for about 30 s, and then the growth of CuNWs started with very little variation in the current pulse. It was observed that the current increased slightly at the start of the positive pulse and then exponentially decayed to a value of about ∼250 mA/cm 2 after less than a millisecond ( Fig.…”

“…Thereafter the barrier layer was thinned gradually by reducing the anodising voltage from 40 V to 0 V linearly in steps of 1 V every 15 seconds. 35 After barrier layer thinning, the mild chemical etching was carried out in 0.63 M C 2 H 2 O 4 solution at 25 C for 2 hrs. The samples obtained were rinsed in distilled water several times and then dried under a nitrogen purge.…”