Controlling morphological parameters of a nanotubular TiO₂ coating layer prepared by anodic oxidation

Abstract A promising modification route to improve osseointegration of dental and medical titanium devices is a nanostructured titanium oxide coating layer in the form of self-ordered vertically aligned nanotubes (or nanotubular TiO₂). In this work, we report a detailed investigation of nanotubular TiO₂ coating layer on metallic Ti substrate prepared by anodic oxidation. The main goal was to determine an optimized and reproducible route to produce a nanotubular TiO₂ layer with homogenous morphology, narrow distribution and accurate control of the nanotube diameter. The influence of electrolyte temperature, anodizing time and applied voltage were studied, comparing three different electrolytes: 1.5 wt% HF, 0.5 wt% HF, and 0.5 wt% HF + 1 mol l⁻¹ H₃PO₄. Samples were analyzed by SEM, EDS, FIB, and XPS techniques. The most favorable result was achieved by using 0.5 wt% HF + 1 mol l⁻¹ H₃PO₄ electrolyte, for anodizing time of about 90 min, temperature of 20 °C, and anodizing potential from 1 to 25 V. Using these parameters, a uniform self-organized nanotubular TiO₂ layer was prepared with a fine control of the nanotube diameter value over a wide range (10 to 100 nm).