【作者】 李玥；

【导师】 蔡舒；

【作者基本信息】 天津大学 ， 材料学， 2019， 硕士

【摘要】 镁合金作为一种新型医用植入金属材料,具有良好的生物相容性、力学相容性和生物可降解性。但是镁合金在人体内降解速度较快,与体液反应产生大量氢气,人体机体无法承受,因此,改善镁合金的耐腐蚀性,控制镁合金的腐蚀速率成为亟待解决的问题,镁合金表面改性是改善镁合金腐蚀性能的主要方法之一。本研究采用一步水热法在AZ31镁合金表面制备锶掺杂钙磷涂层,优化制备工艺,研究水热温度、锶掺杂量等反应条件对涂层组成、结构、电化学性能的影响,通过人体模拟体液（SBF）浸泡实验,探究涂层包覆镁合金试样的矿化能力和长期耐蚀性能。实验结果表明:水热温度100℃、反应时间3 h、反应溶液p H为6.3条件下,可制得底层致密和上层为散落分布团簇状结构的涂层。锶元素的掺杂也可以减少底部涂层裂纹;电化学测试表明,涂层明显提升了镁合金基体的自腐蚀电位和交流阻抗,降低了腐蚀电流密度,提升了材料的耐蚀性能,当Sr/Ca摩尔比为0.10时制备得到试样底部无裂纹涂层,腐蚀电流密度为2.04?A/cm²,远远低于裸镁片的腐蚀电流密度（46.00?A/cm²）,说明此涂层可为镁合金基体提供良好的保护作用。浸泡实验中,在浸泡1 d后涂层表面形成胶状缺钙钙磷涂层,钙磷涂层可以提高镁合金的生物矿化能力。浸泡1-33 d的过程中,浸泡溶液的p H值始终保持在7.5-8.0范围内,平均降解速率在浸泡33 d后维持在0.17 mg/day?cm²,且交流阻抗值在浸泡33 d后为5800 ohm·cm²,高于浸泡初期的交流阻抗值,说明沉积涂层能够为镁合金基体提供良好的保护作用。在140℃下利用一步水热法制备锶掺杂钙磷涂层时,探究了溶液p H对涂层电化学性能的影响,以及涂层在模拟体液中的耐蚀性能,结果表明:高温下合成涂层结构均匀致密,最佳电化学交流阻抗为500000 ohm·cm²,自腐蚀电流密度为0.08?A?cm^-2,显著提升了镁合金的耐蚀性能。更多还原

【Abstract】 In recent years,magnesium（Mg）and magnesium alloys have received enormous attention for their mechanical properties and degradability in a physiological environment which are similar to the natural bone.Nevertheless,the fast corrosion rate has severely limited their clinical applications.During the process of Mg degradation,large amounts of hydrogen are generated,which will destroy the host tissue.It has been demonstrated that the surface modification is an effective method to enhance the corrosion resistance and control the degradation rate of AZ31 substrateIn this work,in order to enhance the corrosion resistance and mineralization of AZ31 magnesium alloy,a strontium doped apatite coating was successfully synthesized on magnesium alloy substrate via one-step hydrothermal method.The effects of Sr doping content and hydrothermal temperature on the microstructure,composition,electrochemical properties of the coating were investigated,then the corrosion behaviour and mineralization ability was examined by immersion tests.The results showed that when the p H value of solution was 6.3,the temperature was 100℃and the reaction time was 3 h,the Sr doped apatite coating consisted of a dense bottom layer and a loose surface layer.Sr doping could effectively reduce the cracks in the dense bottom layer.The potentiodynamic polarization tests in simulated body fluid（SBF）showed that Sr doping could greatly improve the corrosion resistance.When the Sr/Ca molar ratio was 0.10,a crack-free dense coating was obtained and the corrosion current density of the coated magnesium alloy was 2.04?A/cm²,much lower than that of the uncoated counterpart（46.00?A/cm²）,suggesting that Sr doped apatite coatings could provide a long-time protection for AZ31magnesium alloy substrate in the immersion process.The long-term corrosion behaviors of the coated samples were performed in vitro immersion tests.Calcium-deficient apatite was rapidly formed on the surface of the sample Sr/Ca 0.10 after immersion for only one day,suggesting its excellent mineralization ability and anti-corrosion ability.During the immersion period,the p H value of samples revealed a little variation in the range of 7.40 to 8.39,the average degradation rate was only 0.17 mg/day?cm²after 33 days’immersion and the impedance about samples soaked for 33 days was 5800 ohm·cm²,higher than that of samples soaked at initial stage,which indicating that the deposited apatite layer could provide a favorable protection for the AZ31 magnesium alloy substrate.Samples with high impedance were prepared at hydrothermal temperature of140℃,and p H value of reaction solution and the corrosion behaviour was examined.Results showed that the coating was dense and uniform.The impedance of the coated sample was 500000 ohm·cm²and the corrosion current density was 0.08?A?cm^-2,indicating that the coating could effectively improve the corrosion resistance of magnesium alloy in SBF.更多还原