镍钛合金表面钛酸锶生物薄膜的水热合成

目的：改善镍钛合金的耐蚀性和添加锶离子用于治疗骨质疏松症。方法采用氢氧化钠和硝酸锶混合溶液对镍钛合金进行水热处理，处理温度180℃，处理时间分别为1、3和6 h。采用扫描电镜、X射线能谱、X射线衍射和X射线光电子能谱对试样进行显微结构和化学成分分析，采用接触角测量仪评价试样的亲水性，在无钙Hank’s平衡盐液中进行动电位极化实验评价试样的耐蚀性，采用粘结拉伸法测量钛酸锶薄膜与镍钛合金基体之间的结合强度。结果镍钛合金经过水热处理后表面形成了由钛酸锶颗粒组成的薄膜，颗粒尺寸约240~490 nm，薄膜中含有少量镍元素。抛光镍钛试样的水接触角约70°，水热处理试样的接触角大幅上升，达到120°左右。在钝化区内，水热处理3 h试样的阳极电流密度比抛光试样降低了大约一个数量级，因此水热处理试样具有更好的耐蚀性。水热处理3 h制备的钛酸锶薄膜与镍钛基体之间的表观结合强度值为14.1 MPa。结论水热处理不仅改善了镍钛合金的耐蚀性，也在合金表面添加了锶离子，可用于治疗骨质疏松症。

Hydrothermal Synthesis of Strontium Titanate Biofilms on NiTi Alloy

ABSTRACT:Objective To improve the corrosion resistance of NiTi alloy and add strontium ions for the treatment of os-teoporosis.Methods The mixture solution of sodium hydroxide and strontium nitrate was used for hydrothermal treatment of NiTi alloy. The treatment temperature was 180℃ and the treatment duration was 1 h, 3 h and 6 h, respectively. The micro-structure and chemical composition of the samples were analyzed by scanning electron microscopy, energy dispersive of X-ray, X-ray diffraction and X-ray photoelectron spectroscopy. Hydrophilicity of the samples was assessed by contact angle measure-ment. The corrosion resistance was tested by potentiodynamic polarization test in the Ca-free Hank’s balanced salt solution, and the bonding strength of the hydrothermally prepared film on NiTi substrate was measured by pull-off test.Results Films con- sisting of strontium titanate particles were formed on NiTi alloy after the hydrothermal treatments, with the particles size ranging 240~490 nm, and small amount of nickel existed in the films. Water contact angle of the polished NiTi sample was 70°, and it was significantly increased to around 120° after the hydrothermal treatments. Within the passivation zone, the anodic current density of the hydrothermally treated (3 h) sample was decreased by about one order compared with that of the polished sample, and thus the hydrothermally treated sample had much better corrosion resistance. The apparent bonding strength value of the hydrothermally prepared (3 h) SrTiO3 film on NiTi substrate was 14.1 MPa. Conclusion The hydrothermal treatment improved the corrosion resistance of NiTi alloy, and the strontium ions added on the alloy surface could be used to treat osteoporosis.