Microstructure and Properties of Nanostructured Coating on Ti6Al4V

Abstract

Implant surface properties of Ti6Al4V alloy that is currently used as a biocompatible material because of a variety of unique properties can be improved by a self-organized TiO2 layer. The TiO2 nanotubes forming on the titanium-based materials is a relatively recent technology for the surface properties modification and represents pronounced potential in promoting cell adhesion, proliferation, and differentiation that facilitate an implant osseointegration. This work focuses on the influence of surface treatment quality and anodic oxidation parameters on the structure features and properties of TiO2 nanotube coatings. The nanotubes were formed on Ti6Al4V alloy substrates by simultaneous surface oxidation and controlled dissolving of an oxide film in the presence of fluorine ions. The anodization process on ground or polished samples was performed at experimental condition of 30 V for 1 h. The selected anodized samples were heat treated for 2 h at 500 °C under flowing argon. All samples were characterized by scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The corrosion rate in physiological solution reached 0.0043, 0.0182, and 0.0998 mm per year for the samples in polished and not-anodized, as-anodized, and anodized-heat treated conditions, respectively.

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

“…As mentioned before, one particular aspect of the produced anodized layers over the Ti6Al4V alloy was the non-uniform growth of the nanotubes over α and β phases. This lack of uniformity was previously reported by several authors, confirming that, over the α-phase, a well-defined nanotubular structure is generally grown, while, over the β-phase, pits are observed with an oxide not quite developed, which may or may not present a nanotubular structure, depending on the anodization process conditions [ 14 , 19 , 26 , 27 , 31 ].…”

“…On the other hand, not all authors recognize the dual nature of morphology of the oxide produced over the Ti6Al4V alloy, which could be related to the different compositions of the electrolytes used in the anodization processes [ 31 , 35 , 36 ]. In Figure 4 and Figure 5 , FESEM micrographs at high magnifications of the anodic oxides over α- and β-phases, respectively, are reported for specimens anodized for 60 min at different applied potentials.…”

“…Among the vast assortment of titanium alloys, the ternary Ti6Al4V alloy is one of the most technologically relevant, mainly in the biomedical field, and different studies demonstrated the possibility to produce TNTs on it using both water based [ 8 , 23 , 24 , 25 , 26 ] and organic based electrolytes [ 27 , 28 , 29 , 30 , 31 ]. In water based electrolytes, starting from Zwilling [ 8 ], different studies [ 23 , 24 , 25 , 26 ] highlighted that the biphasic microstructure of the underlying alloy (α-phase enriched in Al and β-phase enriched in V) affected markedly the size and the distribution of pores in the anodic oxide layer.…”

“…In particular, Macak et al [ 23 ], by performing potentiostatic anodization at the same conditions on Ti6Al4V and Ti6Al7Nb, pointed out that TNTs could grow only on β grains enriched in Nb and not on β grains enriched in V, attributing this behavior to the high solubility of V-rich anodic oxide and, hence, its early passivity breakdown. The use of organic electrolytes for the anodization of Ti6Al4V instead was reported in few works, and most of them were related to ethylene glycol based electrolytes containing NH 4 F and water [ 27 , 28 , 29 , 30 , 31 ]. Among them, only the work of Jordanovová et al [ 31 ] clearly showed the differences on the morphology of the anodic oxides grown over α and β-phases.…”

“…The use of organic electrolytes for the anodization of Ti6Al4V instead was reported in few works, and most of them were related to ethylene glycol based electrolytes containing NH 4 F and water [ 27 , 28 , 29 , 30 , 31 ]. Among them, only the work of Jordanovová et al [ 31 ] clearly showed the differences on the morphology of the anodic oxides grown over α and β-phases.…”