TiO2 nanotubes grown on Ti and Ti6Al4V alloy spheres by bipolar anodization

Abstract

In this work, the anodization of spheres of Ti and Ti6Al4V alloy (TiAlV) in glycerol-based electrolytes using bipolar electrochemistry is shown for the first time. TiO2 nanotube (TNT) layers were found over the entire surface area of the Ti and TiAlV spheres using a square wave potential of +60 V and +65 V with 5.56 x 10(-4) Hz. The TNTs' inner diameter on the extremities of the Ti spheres was similar to 63 nm and similar to 78 nm, for +60 V and +65 V, respectively. The inner diameter of the TNTs fabricated on the TiAlV spheres was similar to 36 nm and similar to 43 nm for +60 V and +65 V, respectively. The effect of the alloying elements of the TiAlV spheres on the TNT layers was also investigated. To estimate the effective potential on the spheres contributing to the TNT layer formation, also the conventional anodization was performed on flat Ti and TiAlV foils for comparison. It was found that the effective potential reached on the extremities of the Ti and TiAlV spheres near the feeder electrodes was only 29 % and 16 % of the applied potential, respectively.