Synthesis of a porous oxide layer on a multifunctional biomedical titanium by micro-arc oxidation

To improve apatite forming ability of Ti–24Nb–4Zr–7.9Sn alloy, a porous oxidation layer has been synthesized by micro-arc oxidation in a calcium acetate electrolyte and subsequent heat treatment. These oxide layers were characterized by scanning electron microscopy, thin film X-ray diffraction and X-ray photoelectron spectroscopy. After the above treatments, the surface oxide consists of two layers: a thin, compact and uniform inner layer and a porous outer layer. Ca ions are incorporated into the oxide layer in the form of CaO while Ti, Nb and Sn participate in the oxidation to form TiO2, Nb2O5 and SnO2, respectively. After heat treatment at 600 °C, surfaces with such porous oxides have better apatite forming ability than the ground, smooth surface of the alloy, as evidenced by apatite formation within 7 days of soaking in a simulated body fluid. Preliminary in vitro cell test on rabbit's osteoblast show that these surfaces gain considerable improvement in cell proliferation.