Hydroxyapatite precipitation on nanotubular films formed on Ti-6Al-4V alloy for biomedical applications

•Hydroxyapatite (HA) precipitation on nanotubular films formed on Ti–6Al–4V alloy was investigated using a variety of experimental methods.•HA precipitation treatment was carried out using a cyclic voltammetry method after nanotube formation on Ti–6Al–4V alloy.•Plate-like precipitates were formed on the bulk (not anodized) alloy, and the size of precipitates increased with the number of deposition cycles.•HA precipitates that formed on the nanotube formed alloy had a mixed plate-like and flower-like morphology with number of deposition cycles.

In this study, hydroxyapatite precipitation on nanotubular film-formed Ti-6Al-4V alloy for biomedical applications has been investigated using a variety of techniques. To prepare the substrate samples for hydroxyapatite (HA) deposition, the starting Ti-6Al-4V alloy was polished and heat-treated for 12 h at 1050 °C in an Ar atmosphere, followed by water-quenching at 0 °C. Nanotube formation on the titanium alloy was performed using anodization with a DC power supply at 30 V for 1 h in 1 M H3PO4 + 0.8 wt.% NaF at 25 °C. Subsequent HA precipitation treatment was carried out by cyclic voltammetry over a potential range of −1.5 V to 0 V using a scanning rate of 100 mV/s in 0.03 M Ca(NO3)2 ∙ 4 H2O + 0.018 M NH4H2PO4 at 80° ± 1 °C. Four different numbers of cycles were employed: 10, 20, 30, and 50. Surface morphology and structure were examined by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy.The heat-treated Ti–6Al–4V alloy has a needle-like duplex microstructure containing the martensitic α′ phase and β phase. Plate-like precipitates were formed on bulk Ti–6Al–4V alloy, and the size of these precipitates increased with the number of deposition cycles. The HA precipitates on the nanotube surface showed a mixture of plate-like and flower-like particles with more deposition cycles. The deposited HA phase in the coated layer had an amorphous structure, with particle composition in good agreement with Ca10(PO4)6(OH)2.