Surface anodization of the biphasic Ti13Nb13Zr biocompatible alloy: Influence of phases on the formation of TiO2 nanostructures

摘要

Here we report for the first time that the anodization of the biphasic (alpha'+beta) Ti13Nb13Zr alloy form arrays of TiO2 nanotubes with well-defined circular geometry in the alpha' phase, while nanopores of TiO2 are formed in the beta phase. Samples of the Ti13Nb13Zr alloy were severely plastic deformed using High-Pressure Torsion (HPT) to refine the microstructure and to redistribute alpha' and beta phases. The anodization was performed using an organic electrolyte (glycerol) containing fluoride ions and a few percentages of water. All the specimens coated with nanotubes were annealed at 550 degrees C to crystallize the modified surface of the as-anodized samples. XRD analyses confirmed that the as-anodized amorphous nanostructures crystallize in a mixture of anatase and rutile after heat treatment, and SEM observations showed no significant morphological changes in the surface phases. The evaluation of corrosion resistance showed that anodized samples have much better corrosion properties than polished ones without any evidence of pitting corrosion. Quantitative comparison between anodized coarse-grained (alpha'+beta)-Ti alloy and ultra-fine grained (alpha'+beta)-Ti one showed that the nanostructuring of the (alpha'+beta)-Ti alloy by HPT helped to improve the bioactivity when compared with the coarse-grained sample. (C) 2019 Elsevier B.V. All rights reserved.