Electrochemical Formation of Self-Organized Nanotubular Oxide Layers on Niobium (Review)

Background: This mini-review paper is focused on the anodic formation of selforganized nanotubular oxide layers on niobium as a nontoxic and allergy-free metallic biomaterial. Objective: The main purpose of the work was to outline the research activities being undertaken on the electrochemical modification of niobium to obtain its porous oxide with enhanced biocompatibility. Method: The effect of various parameters, such as concentration of fluoride anions in electrolyte, pH of electrolyte, and current-voltage-time conditions on the anodic formation of Nb2O5 nanotubes, was summarized. Results: Thirty-seven references were included in this mini-review and they were divided into main five parts. First part outlined the electrochemical formation of self-organized nanotubular oxide layers on niobium via anodic oxidation. The mechanism of the electrochemical formation of niobium oxide nanotubes was discussed. Second part presented the influence of the electrolyte type used for anodic oxidation of niobium and the fluoride ion concentration in the electrolyte on the type and dimensions of the obtained oxide niobium nanotubes. The influence of the applied voltage during anodic oxidation of niobium on the morphological parameters of the formed nanotube arrays was described in third part. The importance of the selection of the electrolyte pH for tailoring the length of niobium oxide nanotubes was demonstrated in fourth part. The last part outlined the structure of niobium oxide nanotubes. Conclusion: Key results were extracted and reviewed from publications of research activity in anodic oxidation of niobium introduced basics of that process and the current trends in electrochemical improvement of biocompatibility of metallic nanobiomaterials were presented.