Hydrothermal growth of TiO2-CaP nano-films on a Ti–Nb-based alloy in concentrated calcium phosphate solutions

The Ti–Nb-based TLM alloy (Ti–25Nb–3Zr–2Sn–3Mo) was subjected to hydrothermal treatment in the concentrated Ca3(PO4)2, CaHPO4, and Ca(H2PO4)2 solutions for the purpose of calcification. The treated samples are covered by films consisting of Ca-rich nano-crystallites (100–500 nm) and small nano-grains. XPS and XRD analyses reveal the formation of hydroxyapatite, TiO2, and Nb2O5 at the sample surface. The sample hydrothermally treated in CaHPO4 solution exhibits bioactivity by inducing the formation of apatite layer after soaking test in the simulated body fluid for 15 days. The work would provide a good bioactive surface modification method for Ti–Nb alloy implants with complex shapes and even pores.