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

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 degrees C in an Ar atmosphere, followed by water-quenching at 0 degrees 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 degrees 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) center dot 4 H2O + 0.018 M NH4H2PO4 at 80 degrees +/- 1 degrees 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 alpha' phase and beta 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 Ca-10(PO4)(6)(OH)(2). (C) 2013 Elsevier B.V. All rights reserved.