【作者】 赵立臣；

【导师】 崔春翔；

【作者基本信息】 河北工业大学 ， 材料学， 2010， 博士

【摘要】 纯镁及其合金由于具有良好的生物相容性和可降解性而有望成为最有潜力的可降解体内植入材料。但由于纯镁及其合金在水溶液中的耐蚀性较差,尤其在含有Cl-的环境中（如人体内的生理环境）耐蚀性更差,因此当镁基材料植入体内后,在受伤的骨组织尚未完全愈合时,镁基材料已因腐蚀而受到严重破坏。鉴于此,目前纯镁及其合金作为体内可降解植入材料使用时迫切需要解决的问题是延缓植入物在体内的降解速率。提高纯镁及其合金在腐蚀介质中耐蚀性的可能途径是成分净化处理、合金化处理或表面涂层改性。本文采用微弧氧化的方法在纯镁和Mg-Zn合金表面制备了一层陶瓷保护层,通过物理屏障将基体金属和腐蚀介质隔离,以延缓基体金属在腐蚀介质中的降解速率。为赋予陶瓷涂层良好的生物相容性,选用无毒元素的电解液进行微弧氧化,系统研究了电解液、电流密度、温度和微弧氧化时间等参数对陶瓷涂层耐蚀性的影响。基于优化的NaOH（30 g/L）、Na₂SiO₃·9H₂O（160 g/L）、Na₂B₄O₇·10H₂O（160 g/L）的水溶液电解液,温度20和25℃,电流密度40 mA/cm2,研究了陶瓷涂层的生长过程。为提高微弧氧化陶瓷涂层的耐蚀性,向电解液中添加三乙醇胺（TEA）有机添加剂和CaO、CaCO3以及羟基磷灰石（HA）粉末等无机添加剂。结果表明,这些添加剂参与了微弧氧化过程中陶瓷涂层的生成反应,生成厚度约为30～50μm的致密陶瓷层。X-射线衍射结果表明陶瓷层具有非晶态的相结构。陶瓷层经硅酸钠水溶液封孔后,孔隙率和孔隙尺寸明显下降,表面光洁度进一步提高。为检验陶瓷层对基体金属的保护作用,覆盖着陶瓷层的纯镁和Mg4Zn合金在模拟体液（SBF）中进行了电化学极化曲线测量和浸泡测试。实验结果表明,微弧氧化陶瓷层能够有效地将基体金属和腐蚀环境隔离,显著提高了纯镁和Mg-Zn合金在模拟体液中的耐蚀性。另外,模拟体液浸泡实验还表明覆盖着陶瓷层的纯镁和Mg4Zn合金能够有效诱导Ca、P沉积,具有良好的生物活性。溶血实验结果表明,覆盖着陶瓷涂层的纯镁和Mg4Zn合金的溶血率均小于5%,符合生物医用材料的溶血要求,具有良好的血液相容性。更多还原

【Abstract】 Pure magnesium and its alloys have excellent biocompatibility and biodegradation which make them the most potential biodegradable implants. However, the degradation rate of pure magnesium and its alloys is so rapid in aqueous solutions, especially in chloride-containing media such as human physiological environments that the implants can be corroded seriously before the diseased or damaged bone tissue becomes healed. Therefore, the inhibition of high corrosion rate is the most urgent problem to be solved for magnesium and its alloys as degradable implants.Current approaches to slow down the degradation rate of magnesium and its alloys include high purity alloys, element alloying and surface coating modification technology. In the present thesis, a protective micro-arc oxidation (MAO) coating has been fabricated on pure magnesium and alloys. The coating can isolate the substrate from corrosive media as a physical shield and inhibit the degradation rate of the metal substrate.The MAO process was performed in aqueous solutions without toxic elements to keep good biocompatibility of MAO coatings. The effects of electrolyte composition, current density, electrolyte temperature and MAO time on corrosion resistance of ceramic coating were investigated systematically. The growth characteristics of MAO coating was investigated in the optimized electrolyte of NaOH (30 g/L), Na2SiO3?9H2O (160 g/L) and Na2B4O7?10H2O (160 g/L) at 20 and 25℃under the condition of 40 mA/cm2.In order to improve the corrosion resistance of MAO coating, some additives such as triethanolamine, calcium oxide, calcium carbonate and hydroxyapatite were added to the optimized electrolyte during MAO process. The results indicate that the additives participate in the growth reactions of ceramic coating. SEM micrographs show that the thickness of the coatings are about 30～50μm. XRD patterns of the coatings show that the coatings are amorphous. After sealing in Na2SiO3 solution, the surface roughness of MAO coating improved and porosity of MAO coating also decreased. The corrosion resistance of Mg and Mg4Zn alloy covered with anodic coating was tested by potentiodynamic polarization tests and immersion tests in simulated body fluid (SBF). The results show that the MAO coatings can efficiently prevent metal substrate from contacting with corrosive media and the corrosion resistance of the samples was improved remarkably.In addition, the immersion tests also show that Mg and Mg4Zn alloy covered with anodic coatings have a good ability for inducing Ca and P deposition.Homolysis tests were used to evaluate the blood compatibility of Mg and Mg4Zn alloy covered with MAO coatings. The results confirm that the hemolysis ratio of the samples was less than 5% and the samples have excellent blood compatibility.更多还原