Oxidation treatments of beta-type Ti-40Nb for biomedical use

Beta-type Ti-40Nb with very low Young's modulus is a promising alloy for long-term bone implant applications but surface states must be tailored for optimum osseointegration. Different anodization methods for surface oxidation were evaluated and oxide layers with characteristic morphologies were obtained. Anodization in fluoride-containing solutions generates oxide nanotubes with higher aspect ratio than those grown on CP2-Ti. The electrolyte composition has some influence on the oxide morphology. Plasma electrolytic oxidation in strongly alkaline solution yields a two-layer oxide structure with a thin compact inner layer and a much thicker outer layer with micropores and microchannels. Inductively coupled RF oxygen plasma anodization causes the formation of microstructured oxides on the Ti-40Nb surface. With increasing processing temperature a transition from random structured to patterned oxides was observed which is opposite to the trend for CP2-Ti. For all three techniques the oxide layer growth on the Ti-40Nb alloy follows the principal mechanisms that are established for Ti. Nb species are involved in the oxidation processes which causes significantly enhanced layer thickness growth, morphological changes and mixed oxides (TixNb1 − x)O2, more specific (Ti0.75Nb0.25)O2. All obtained oxide types appear to be promising as coatings of beta-type implants with appropriate bioactivity to stimulate bone growth.