M. Sarraf

Nanomechanical properties, wear resistance and in-vitro characterization of Ta2O5 nanotubes coating on biomedical grade Ti–6Al–4V

Tantalum pentoxide nanotubes (Ta2O5 NTs) can dramatically raise the biological functions of different kinds of cells, thus have promising applications in biomedical fields. In this study, Ta2O5 NTs were prepared on biomedical grade Ti-6Al-4V alloy (Ti64) via physical vapor deposition (PVD) and a successive two-step anodization in H2SO4: HF (99:1)+5% EG electrolyte at a constant potential of 15V. To improve the adhesion of nanotubular array coating on Ti64, heat treatment was carried out at 450°C for 1h under atmospheric pressure with a heating/cooling rate of 1°Cmin-1. The surface topography and composition of the nanostructured coatings were examined by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS), to gather information about the corrosion behavior, wear resistance and bioactivity in simulated body fluids (SBF). From the nanoindentation experiments, the Youngs modulus and hardness of the 5min anodized sample were ~ 135 and 6GPa, but increased to ~ 160 and 7.5GPa, respectively, after annealing at 450°C. It was shown that the corrosion resistance of Ti64 plates with nanotubular surface modification was higher than that of the bare substrate, where the 450°C annealed specimen revealed the highest corrosion protection efficiency (99%). Results from the SBF tests showed that a bone-like apatite layer was formed on nanotubular array coating, as early as the first day of immersion in simulated body fluid (SBF), indicating the importance of nanotubular configuration on the in-vitro bioactivity.

Optimizing PVD conditions for electrochemical anodization growth of well-adherent Ta2O5 nanotubes on Ti–6Al–4V alloy

Well-adherent tantalum pentoxide nanotubes (Ta2O5 NTs) were successfully grown on Ti–6Al–4V alloy (Ti64) through optimization of physical vapor deposition magnetron sputtering (PVDMS) followed by a two-step anodization and subsequent thermal treatment from 450 to 1000 °C for 1 h with a heating/cooling rate of 1 °C min−1, under atmospheric conditions. The effective sputter yield during the magnetron sputtering process was achieved with a DC power of 350 W, temperature of 250 °C and a deposition time of 6 h. The results showed that the anodization time played a key role in the growth of the Ta2O5 NTs and microstructural evolution. The nanotubes pore size and tube length varied from 18 to 30 nm and 73 nm to ∼4 μm as anodizing time rose from 30 s to 20 min, respectively. For the 450 °C annealed sample with the strongest adhesion, the scratch length, failure point and adhesion strength were 1024 μm, 863 μm and 2301 mN, respectively. The 450 °C annealed coating showed the highest wettability (lowest contact angle value) among the specimens. This multi-step approach could be considered for the design of various nanostructured titanium implant surfaces.