【作者】 颜廷亭；

【导师】 熊党生； 杨柯；

【作者基本信息】 南京理工大学 ， 材料学， 2010， 博士

【摘要】 镁及镁合金作为一种新型可降解植入材料,具有优异的生物相容性和综合力学性能,近年来正吸引着越来越多研究者的关注。但是由于镁及镁合金较差的耐蚀性能导致的局部碱化、氢气释放和局部镁离子浓度过高等问题,会影响到其在临床上的应用。本文针对AZ31B镁合金作为新型生物可降解医用植入材料,在材料表面上成功地制备出稀土转化涂层、氧化锰转化涂层、电镀锌涂层和氟转化涂层,并对各涂层的制备工艺、微观形貌、相组成、成膜机理、耐蚀性能等进行了系统研究。在此基础上,本文选择氟转化涂层作为重点研究对象,对其在体内外的耐蚀性能和生物相容性进行了深入研究。论文得到以下主要研究结果：(1)在AZ31B镁合金表面制备了稀土转化涂层,并采用正交试验对涂层制备工艺进行了优化设计。涂层均匀致密,厚度为2-4μm,主要成分为CeO2和MgO。腐蚀实验结果表明,稀土转化处理能够显著改善AZ31B镁合金在生理盐水及SBF溶液中的耐蚀性能。体外凝血实验结果表明,转化处理AZ31B镁合金表现出较好的抗凝血性能,具有与316L不锈钢相当的良好血液相容性。(2)在AZ31B镁合金表面制备了氧化锰转化涂层。涂层与基体结合紧密,表面均匀分布有网状微裂纹,涂层厚度为4-6μm,主要成分为MgO、Mg(OH)2、MnO2、Mn2O3和Mn304。耐蚀性能研究结果显示,氧化锰处理能够有效提高AZ31B镁合金在SBF溶液中的耐蚀性能。体外溶血实验结果表明,转化处理能够有效抑制AZ31B镁合金的溶血反应。(3)采用脉冲电镀方法,在AZ31B镁合金表面制备了电镀锌涂层。镀锌涂层均匀,与基体结合紧密。电镀锌涂层后的AZ31B镁合金在SBF中浸泡时,表面会不断沉积Ca和P元素,表明涂层具有一定的生物活性。然而浸泡实验与电化学实验结果表明,电镀锌涂层未能有效改善AZ31B镁合金的耐蚀性能,不能作为镁合金表面的防护涂层单独使用,需要进行进一步的复合涂层处理。(4)在AZ31B镁合金表面制备了氟转化涂层,并研究了处理工艺对涂层耐蚀性能及厚度的影响。涂层的主要成分为MgO与MgF2。氟转化处理能显著提高AZ31B镁合金在SBF溶液中的耐蚀性能。此外,氟处理将镁合金的主要腐蚀形式由点蚀转变为面腐蚀为主要腐蚀形式,使氟转化处理后的镁合金表现出“滞后”的降解行为。氟转化处理AZ31B镁合金具有优异的细胞相容性、血液相容性及抗菌性能。动物植入实验结果表明氟转化处理能够有效改善AZ31B镁合金样品在动物体内的耐蚀性能,提高植入样品表面的成骨活性,有利于材料在骨组织植入领域的应用。更多还原

【Abstract】 Recently, magnesium (Mg) and its alloys have attracted much attention as potential biodegradable implant materials owing to their good biocompatibility and better mechanical properties combination such as high strength and the elastic modulus close to that of natural bones, compared with those of biodegradable polymers. However, problems such as alkalization, hydrogen release and high concentration of magnesium ions, caused by high corrosion rate in body’s fluid, will affect their clinical applications. Rare earth conversion coating, manganese oxide conversion coating, eletrogalvanizing zinc coating, fluoride conversion coating were respectively prepared on the surfaces of AZ31B magnesium alloy in order to better control the degradation of the alloy and further improve its biocompatibility. Surface characterizations, corrosion resistance and biocompatibility of the different coatings were systematically studied. The corrosion resistance and biocompatibility of fluoride conversion coating were specially studied by both in vitro and in vivo tests. The main conclusions of the dissertation were summarized as following:(1) In order to improve the corrosion resistance of biodegradable AZ31B magnesium alloy, a rare earth conversion coating was prepared on the surface of AZ31B alloy. An orthogonal experiment was designed to optimize the processing parameters for formation of dense conversion coating. The SEM study revealed that the thickness of the coating was 2-4μm. The XRD analysis indicated that the composition of the coating was composed of CeO2 and MgO. It was found that the coating prepared from optimized processing possessed good corrosion resistance in both of physiological saline and SBF, as well as good anti-clotting property.(2) A manganese oxide contained coating was prepared on biodegradable AZ31B magnesium alloy in order to control the degradation of AZ31B and improve its biocompatibility. Morphology, composition and corrosion resistance of the coating were studied. The SEM observations showed that the coating was approximately 4-6μm in thickness with net-like microcracks. The XPS analysis indicated that the coating was mainly composed of MgO, Mg(OH)2, MnO2, Mn2O3 and Mn3O4. It was found that AZ31B with such coating behaved better corrosion resistance in SBF through electrochemical and immersion tests. The hemolytic assay indicated that the treated AZ31B had no hemolytic effect.(3) An eletroglavanizing zinc coating was prepared on the surface of AZ31B alloy by pulse plating treatment. XRD and SEM analyses were used to examine the composition and morphology of the zinc film. The zinc coating was compact and bonding well to the substrate of AZ31B. The deposition of Ca-P on the surface of zinc coating revealed that the coating behaved bioactivity to a certain extent. Immersion and electrochemical tests indicated that the zinc coating could not effectively improve the resistance of AZ31B and not be suitable to be singly used as the protectable coating for magnesium alloy.(4) A compact fluoride conversion coating was prepared on AZ31B magnesium alloy by reaction with hydrofluoric acid. The SEM observation showed that a compact film with some irregularly distributed pores was formed on the surface of sample. The TF-XRD and XPS analyses indicated that the coating was mainly composed of MgO and MgF2. The relationship between treatment parameters and anti-corrosion property or thickness of the coating was systematically studied. Electrochemical and immersion tests revealed that the corrosion type of fluoride treated AZ31B was homogenuous corrosion and the fluoride conversion coating could effectively improve the corrosion resistance of AZ31B in SBF. The corrosion type, combined with the anti-corrosion property, could ensure a constant mechanical property of AZ31B in the corrosion environment. In vitro biocompatibility tests showed that fluoride treated AZ31B had superior cell compatibility, blood compatibility and antibacterial capability. In vivo study indicated that fluoride treated AZ31B exhibited better corrosion resistance than the bare one. The pathological examination demonstrated that the fluoride treated AZ31B exhibited significantly good osteogenesis, which would benefit the early healing process of bone tissue.更多还原