Fabrication and characterization of self-organized mixed oxide nanotube arrays by electrochemical anodization of Ti–6Al–4V alloy

Self-organized mixed oxide nanotube arrays were fabricated by anodization of Ti–6Al–4V alloy in H3PO4/NH4F aqueous solution. The nanotubes of 90–180 nm in diameter and 10–20 nm in wall thicknesses could be tuned by changing anodization voltages. Whereas, the as-prepared nanotube arrays were amorphous; to induce crystallinity, the products were annealed at 400 °C, 500 °C and 600 °C, respectively. The UV–Vis spectra of samples annealed at 600 °C gives the maximum absorption in the visible spectra range. Various characterization techniques (viz., FESEM, XPS, XRD, and UV–Vis) were used to study the morphology, composition, phase and band gap of the films.