微弧氧化镁表面致密层外延生长构建生物活性陶瓷涂层及腐蚀行为

Modified hydroxyapatite coating formed on magnesium alloy by micro-arc oxidation. A gradient bioactive ceramic coating is prepared on the surface of micro-arc oxidation (MAO) coating by cathodic electrodeposition technique. So it can realize the epitaxial growth of the dense layer. The corrosion resistance of the MAO coating can be improved, and the bonding strength between the layers is brought up. The growth of the gradient coating can be controlled by adjusting the composition of the electrolyte and the parameters of the power. The effect of parameters on the structure and composition of the coating is studied, and so on the properties of the coatings. The relationships between the composition and the coating process are discussed. The relationships between the composition and the properties are further studied. The factors of micro-arc discharge are considered by the prefabricated coating, emission spectroscopy, EIS and Mott-Schottky. Based on the theory of dielectric breakdown, the breakdown mechanism of gas film and solid film is studied. The stress corrosion cracking behavior of the MAO coating and the composite coating in Hank’s solution are studied by EIS. The mechanism of stress corrosion of the coatings is researched. The biocompatibility of the coatings is tested in vitro. So the relationships between the microstructure of the coating and the biocompatibility can be created, which provide the data for clinical trial of magnesium alloy.

对镁合金进行微弧氧化处理，在其表面制备改性羟基磷灰石涂层。利用阴极微弧电沉积技术在微弧氧化涂层表面制备梯度生物活性陶瓷涂层，实现微弧氧化致密内层的外延式生长。提高涂层耐蚀性能的同时，使涂层与涂层间具有较高的结合强度。通过调控电解液组成和电源工艺参数，可以实现梯度涂层的可控式生长。研究工艺参数对涂层组成结构及性能的影响，建立涂层制备工艺-涂层组成结构-涂层性能之间的对应关系。通过预制涂层、发光光谱分析、EIS及Mott-Schottky测试，研究微弧放电击穿的影响因素；在此基础上结合电介质击穿理论，研究气膜击穿和固膜击穿的击穿机制；利用EIS技术研究微弧氧化涂层及复合梯度涂层在Hank’s溶液中的应力腐蚀行为，探讨其应力腐蚀失效机制。采用体外试验评价改性后镁合金的生物相容性，建立涂层显微组织结构与生物相容性的关系。为镁合金的临床试验和实用提供基础性的数据。

镁及镁合金合金具有优异的生物相容性、良好的机械性能，作为一种新型的可降解生物医用金属材料，近年来已经得到越来越多的研究。但镁合金的耐腐蚀性较差，植入人体后，短时间会失去原有的机械性能，与骨骼愈合的时间不匹配，所以将镁合金作为植入材料，则需要提高其耐腐蚀性能。本项目通过微弧氧化的方法在镁合金表面制备了含羟基磷灰石的陶瓷涂层，为了进一步改善该陶瓷涂层的耐腐蚀性能，采用阴极微弧电沉积技术在微弧氧化涂层表面制备梯度生物活性陶瓷涂层，实现了微弧氧化致密内层的外延式生长。提高涂层耐蚀性能的同时，使涂层与涂层间具有较高的结合强度。通过调控电解液组成和电源工艺参数，实现了梯度涂层的可控式生长。研究了工艺参数对涂层组成结构及性能的影响，建立涂层制备工艺-涂层组成结构-涂层性能之间的对应关系。通过预制涂层、发光光谱分析、EIS及Mott-Schottky测试，研究微弧放电击穿的影响因素；在此基础上结合电介质击穿理论，研究了气膜击穿和固膜击穿的击穿机制；利用EIS技术研究微弧氧化涂层及复合梯度涂层在Hank’s溶液中的应力腐蚀行为，探讨了应力腐蚀失效机制。采用体外试验评价了改性后镁合金的生物相容性，建立涂层显微组织结构与生物相容性的关系。通过调节电源制备工艺参数可以在镁合金表面制备厚度达80微米、涂层与基体的结合强大大于35 MPa的复合陶瓷涂层，涂层材料在模拟体液中的降解速率比基体镁合金低一个数量级；拉应力作用会加速镁合金基体、涂层材料的降解腐蚀腐蚀速率，拉应力越大降解越快，但是在相同的拉应力作用下镁合金基体的降解速率始终大于微弧氧化涂层材料；微弧氧化既存在固膜击穿，也存在气膜击穿。微弧氧化前期以气膜击穿为主，后期以固膜击穿为主。