【作者】 孔令鸿；

【导师】 曾荣昌； 刘成龙；

【作者基本信息】 重庆理工大学 ， 材料学， 2011， 硕士

【摘要】 金属材料作为近几十年来最成功的硬组织植入材料,在修复或替换骨组织的生物材料方面扮演着重要角色。但目前常用的不锈钢、钛合金、钴镍合金等医用金属材料在生物相容性和力学相容性上存在一定缺陷,且不可降解。医用镁基生物材料具有优良的生物力学性能,生物相容性和可降解性,是一种具有广阔前景的新型人体植入材料。然而,镁合金耐蚀性较差,过快的降解速率制约了其在临床应用上的研究和发展。因此近年来镁合金在模拟人体体液中的腐蚀和保护成为国内外的研究热点。本课题制备的新型Mg-Ca、Mg-Li-Ca和Mg-Li-Ca-Y合金,并进行挤压变形处理,分别使用浸涂和电沉积的方法在其表面进行了制备了硅烷涂层和Ca-P涂层。通过浸泡腐蚀实验、析氢和动电位电化学实验研究了Mg-Ca和Mg-Li-Ca合金及其表面涂层在Hank’s人体模拟体液中的腐蚀行为。考察了热挤压前后合金耐蚀性的变化,探讨了Ca、Li、Y元素对镁合金腐蚀性能的影响,研究了涂层的成膜机理及腐蚀保护效果。采用金相显微镜和扫描电子显微镜(SEM)观察了合金组织、腐蚀形貌和涂层形貌,使用能谱分析(EDS)和X射线衍射(XRD)等表面技术分析了合金、涂层以及腐蚀产物等的成分和结构。研究表明,镁合金在挤压变形过程中发生了动态再结晶,晶粒细化,第二相弥散分布,改善了耐蚀性。Ca元素具有细化晶粒的作用,对提高镁合金的耐蚀性有一定帮助,但当Ca含量超过一定范围时形成更多的Mg2Ca相,会加重微电偶腐蚀导致腐蚀速率快速升高。Mg-Li-Ca合金极化曲线的腐蚀电流密度较大,但随着浸泡时间的延长,腐蚀产物的致密度升高,有效降低了镁合金在Hank’s溶液中的腐蚀速率。合金中加入Y元素后,表面形成致密的氧化膜,提高了阴极析氢阻力,明显改善了镁合金的耐蚀性。硅烷预处理工艺提高了Mg-Ca合金的开路电位,缩小了三种Mg-Ca合金在Hank’s溶液中的腐蚀行为差异,在一定程度上提高了Mg-Ca合金的耐腐蚀性。利用电沉积法在Mg-Li-Ca合金表面制备Ca-P涂层,涂层的Ca/P原子比为0. 70~0. 79,Ca-P涂层明显提高了合金基体的耐蚀性能。更多还原

【Abstract】 Metals as the most popular implant biomaterials played an important role in repairing and replacing bones in recent decades. However, metallic biomaterials, including stainless steels, titanium alloys and nickel-cobalt alloys used have currently some weakness in their bio-compatibility and bio-mechanical compatibility. Magnesium alloy are potential implant materials due to their excellent biocompatibility, good mechanical property and biodegradable. Unfortunately, the high susceptibility of Mg alloys to corrosion and thus too rapid degradation rate in human body limit their applications in the potentially clinical practice. Therefore, the study has been focused on corrosion and protection of magnesium alloys in simulated body fluids.Newly developed Mg-Ca, Mg-Li-Ca and Mg-Li-Ca-Y alloys had been extrued. The corrosion behavior of the alloys with and without sliane film and Ca-P film in Hank’s solution had been investigated by immersion tests, hydrogen evolution, and potentiodynamic electrochemical tests. The microstructure before and after the extrusion deformation and the effect of calcium, lithium and yttrium on the corrosion behavior of the alloys were studied. And the preparation and the corrosion resistance of silane film on Mg-Ca alloys and Ca-P coating on Mg-Li-Ca alloy were also investigated. The microstructure, corrosion morphology and coating surface was observed by means of scanning electron microscope (SEM). Meanwhile X-ray diffraction analysis (XRD) and Energy dispersive spectrum (EDS) were employed to characterize chemical makeup of coatings and corrosion products.The results showed that the grain size of magnesium alloy was decreased substantially with the dynamic recrystallization and the second phases were dispersed during the process of extrusion deformation, and refined with an increase in calcium content. The corrosion resistance of magnesium alloys was improved significantly by the extrusion process. Alloying element calcium can refine grains, and enhance the corrosion resistance of magnesium alloys. However, when the content of calcium exceeded a certain range the micro-galvanic corrosion would be promoted due to the formation of more intermetallic compounds Mg2Ca. The corrosion resistance of Mg-Li-Ca alloy was not more pronounced in the early immersion period, in comparison with Mg-Ca alloys. Note that with increasing immersion time corrosion products led to a rapid alkalization and reduction in the corrosion rate of magnesium alloys in Hank’s solution. The addition of yttrium into Mg-Li-Ca alloy hinder hydrogen evolution on cathode, thus improved the corrosion resistance of the alloy.The silane film increased the corrosion potential and corrosion resistance of the substrates, and reduced the difference of corrosion resistance among three Mg-Ca alloys. A Ca-P coating was prepared by means of electric-deposition on the Mg-Li-Ca alloy. The average Ca/P atomic ratio ranges between 0.70-0.79. The coating exhibited a plate-like morphology and boosted the corrosion resistance of the Mg-Li-Ca alloy.更多还原