On Growth and Morphology of TiO2 Nanotubes on Ti6Al4V by Anodic Oxidation in Ethylene Glycol Electrolyte: Influence of Microstructure and Anodization Parameters

Abstract

Different studies demonstrated the possibility to produce TiO2 nanotubes (TNTs) on Ti6Al4V alloy by electrochemical anodization. However, the anodizing behavior of α and β-phases in organic electrolytes is not yet clarified. This study reports on the anodizing behavior of the two phases in an ethylene glycol electrolyte using different applied potentials and anodizing times. Atomic force and scanning electron microscopies were used to highlight the anodic oxides differences in morphology. It was demonstrated that the initial compact oxide grew faster over the β-phase as the higher Al content of the α-phase caused its re-passivation, and the higher solubility of the V-rich oxide led to earlier pores formation over the β-phase. The trend was inverted once the pores formed over the compact oxide of the α-phase. The growth rate of the α-phase TNTs was higher than that of the β-phase ones, leading to the formation of long and well defined nanotubes with thin walls and a honeycomb tubular structure, while the ones grown over the β-phase were individual, shorter, and with thicker walls.

Formation of Titania Nanowires and Nanorods on Ti-6Al-4V Alloy Using Electrochemical Anodization

“…10 However, this effect has not been reported in organic media/fluorine-based electrolytes because in organic media the aggressive nature of − F ions reduces, which influences the dissolution rate. 21 Similarly, fluorine-based electrolytes are important to form such nanostructures as hydrochloric acid-based electrolytes with similar acidity cannot produce TiO 2 nanostructures at 60 V. 1 In our work, the length of the nanorods and nanowires is in the range of 500-700 nm. This is in good agreement with the previously reported studies.…”

“…1 The nanostructures on Ti64 were formed at 20 V and 25 V, but not at 15 V. It has been reported that at 10 V, a nanoporous oxide film is formed; at 20-40 V, TiO 2 nanotubes are formed, whereas, at 50 V, a sponge-like porous structure is formed on Ti64 in ammonium sulfate and ammonium fluoride electrolytes. 5,7,21,24 Figures 2b and 2c, show the morphological analysis of nanorods and nanowires at 20 V and 25 V, respectively. In the literature, the formation of such nanostructures on Ti64 by anodization has not been reported.…”

“…For example, the concentration of electrolytes, 1,25,26 oxygen content, 10,27 and water content. 1,20,21 The TiO 2 nanowires of length μ ∼ m 5 can be obtained using the anodization of Ti in sodium hydroxide and sodium fluoride. 1,26 However, a high voltage is required to form nanowires on Ti due to lower electrolyte concentration.…”

“…These limitations can be overcome by the electrochemical anodization method, which is cost-effective, simple, and does not require a vacuum system. [19][20][21][22] The method gives the ability to control the pore size of the nanotubes grown over the surface by tuning the voltage, electrolyte, and anodization time. 1,20,21 However, to the best of the current authors' knowledge, no work has been reported on the formation of nanorods and nanowires using HF-based aqueous electrolytes on Ti64.…”

“…[19][20][21][22] The method gives the ability to control the pore size of the nanotubes grown over the surface by tuning the voltage, electrolyte, and anodization time. 1,20,21 However, to the best of the current authors' knowledge, no work has been reported on the formation of nanorods and nanowires using HF-based aqueous electrolytes on Ti64. In this work, we have synthesized and studied the characteristics of highly ordered TiO 2 nanowires and nanorods by electrochemical anodization of Ti64.…”