Hydroxyapatite based and anodic Titania nanotube biocomposite coatings: Fabrication, characterization and electrochemical behavior

The main challenges of biological implants are suitable strength, adhesion, biocompatibility and corrosion resistance. This paper discusses fabrication, characterization and electrochemical investigation of anodized Ti6Al4V without and with a hydroxyapatite (HA) layer, HA/TiO2 nanoparticles (NPs) and HA/TiO2 nanotubes (HA/anodized). X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) were used to characterize and compare properties of different samples. Dense HA with uniform distribution and 12.8 +/- 2 MPa adhesive strength enhanced to 19.2 +/- 4 MPa by the addition of TiO2 nano particles and enhanced to 23.1 +/- 4 MPa by the deposition of a TNT interlayer was fabricated by an anodic oxidation process. EIS analysis divulged the polarization behavior of various layers formed, on a Ti6Al4V substrate. Electrochemical measurements indicated polarization passivation due to incorporation of TiO2 nanoparticles to HA. Hydroxyapatite on a TNT layer revealed lower corrosion resistance than a HA/TiO2 nanoparticle sample due to the vacuolar nature of TNT conformation. The passivation current density of the Ti6Al4V alloy coated with a HA/TiO2 nanocomposite (0.125 mu A/cm(2)) was less than 1% of the bare substrate. (C) 2015 Elsevier B.V. All rights reserved.