基于Mg-4Zn-xNd镁合金植入体的制备及其生物可降解性能的研究

发布时间：2018-05-16 00:07

本文选题：镁合金 + 生物降解性能　；参考：《太原理工大学》2016年硕士论文

【摘要】：生物可降解镁合金作为新一代的医用工程材料受到人们越来越多的关注。与传统的医用金属植入材料不锈钢、钛合金等相比,镁合金铸造性能良好,比刚度、比强度高,弹性模量(E=41-45 GPa)、密度(ρ=1.74-2.0g?cm-3)与人体骨骼接近(E=3-20GPa,ρ=1.8-2.1g?cm-3),在组织修复过程中不会造成应力遮挡。研究表明镁合金在人体内具有良好的生物相容性,但作为植入材料,镁合金在人体内降解过快且腐蚀降解不均匀会导致其机械完整性提前丧失。同时,镁合金植入材料在快速降解过程中发生的副反应会影响材料植入部位的pH平衡,并产生大量氢气囊,影响骨骼生长,无法满足植入后的骨支撑、骨诱导等服役性能要求。本文针对镁合金作为生物医用材料降解速率过快的弊端,采用重力铸造法制备出掺杂有生物活性元素Zn和能大幅度提升合金基体电位的稀土元素Nd的Mg-4Zn-xNd(x=0,1,2,3 wt.%)铸态镁合金,先后通过电化学实验(极化曲线、阻抗谱)和浸渍试验(失重法)等方法研究了Nd含量和热处理过程(固溶处理工艺、热挤压工艺和退火工艺)对Mg-4Zn-xNd镁合金生物降解性能的影响,并对它的腐蚀机制进行了探讨。并进一步通过体外生物相容性实验,研究了Mg-4Zn-xNd合金的降解过程对其细胞相容性的影响。研究结果表明:(1)二元Mg-4Zn合金中的主要物相为α-Mg基体和少量的二元相Mg0.97Zn0.03,三元Mg-4Zn-xNd合金中的主要物相为α-Mg基体和二元相Mg12Nd。稀土元素Nd的添加导致大量Mg12Nd第二相沿晶界位置析出,并使合金的晶粒尺寸显著细化,同时三元合金的腐蚀速率降低30%左右。铸态合金先后在420oC、24h和510oC、4h条件下进行固溶处理后,第二相含量明显降低,晶粒尺寸增大,合金的腐蚀速率降低40%左右,其中Mg-4Zn-2Nd表现出最好的耐腐蚀性能。(2)固溶态Mg-4Zn-2Nd合金在挤压比为16:1,挤压速度为2mm/s,挤压温度分别为350oC,370oC,390oC,410oC条件下进行热挤压处理后,晶粒尺寸减小,且随着温度升高,挤压态合金的晶粒尺寸增大、第二相含量降低,合金的耐腐蚀性能得到不同程度的提高,当挤压温度为370oC时,腐蚀速率最低,达到3.4mm/y。(3)370oC挤压态合金在退火温度为420oC,退火时间分别为5min,15min,30min,60min,120min的退火工艺条件下进行退火处理,随着退火时间延长,合金的晶粒尺寸持续增大,第二相持续析出,加工残余应力逐渐减小,导致合金的腐蚀速率逐渐增大。(4)对比铸态、固溶态、挤压态和退火态合金的腐蚀速率与细胞实验结果表明,镁合金的腐蚀速率对MC3T3-E1成骨细胞在其表面的粘附、活性及分化影响较大;适量的Nd掺杂在提高合金耐腐蚀性能的同时促进细胞的粘附、铺展;热处理工艺导致合金第二相含量及晶粒尺寸发生变化,影响合金的耐腐蚀性能,腐蚀速率的加快抑制了细胞的粘附、增殖及分化过程。
[Abstract]:As a new generation of medical engineering materials, biodegradable magnesium alloys have attracted more and more attention. Compared with traditional medical metal implant materials, such as stainless steel and titanium alloy, magnesium alloy has good casting properties, high specific stiffness, high specific strength, elastic modulus of 41-45 GPaan, density (蟻 _ (1.74-2.0) g / cm ~ (-3) close to that of human skeleton (E _ (3-20), 蟻 _ (1.8-2.1) g / cm ~ (-3), and does not cause stress shielding in the process of tissue repair. The results show that magnesium alloy has good biocompatibility in human body, but as implant material, magnesium alloy degrades too quickly and corrosion degradation inhomogeneously in human body will lead to early loss of mechanical integrity of magnesium alloy. At the same time, the side effects of magnesium alloy implant during rapid degradation will affect the pH balance of the implanted site and produce a large number of hydrogen balloon, which can not meet the requirements of service performance such as bone support and bone induction. In this paper, aiming at the disadvantage of rapid degradation rate of magnesium alloy as biomedical material, magnesium alloy Mg-4Zn-xNdndndndndndndndndndnndndcndndndndndndndndndndnd0OO012wt.g doped with biological active element Zn and rare earth element ND with biological active element Zn and ND were prepared by gravity casting method. The ND content and heat treatment process (solid solution treatment) were studied by electrochemical experiment (polarization curve, impedance spectroscopy) and impregnation test (weightlessness method). The effect of hot extrusion and annealing on the biodegradability of Mg-4Zn-xNd magnesium alloy and its corrosion mechanism were discussed. The effect of degradation process on the biocompatibility of Mg-4Zn-xNd alloy was studied by biocompatibility experiment in vitro. The results show that the main phases in binary Mg-4Zn alloy are 伪 -Mg matrix and a small amount of binary phase Mg0.97Zn0.03, and the main phases in ternary Mg-4Zn-xNd alloy are 伪 -Mg matrix and binary phase Mg12Nd. The addition of rare earth element ND resulted in the precipitation of a large number of Mg12Nd second phases along the grain boundary, and the grain size of the alloy was significantly refined, and the corrosion rate of the ternary alloy was reduced by about 30%. After solution treatment at 420oC ~ (2 +) for 24 h and 510oC _ (4) for 4 h, the content of the second phase decreased obviously, the grain size increased, and the corrosion rate of the alloy decreased by about 40%. Mg-4Zn-2Nd shows the best corrosion resistance.) the grain size of Mg-4Zn-2Nd alloy decreases with increasing temperature after hot extrusion treatment under the condition of extrusion ratio of 16: 1, extrusion speed of 2mm / s and extrusion temperature of 350oC ~ 370oC ~ 390oC ~ (410oC). When the grain size of extruded alloy increases and the second phase content decreases, the corrosion resistance of the alloy is improved to some extent. When the extrusion temperature is 370oC, the corrosion rate is the lowest. When the annealing temperature is 420 OC and the annealing time is 5 min ~ 15 min ~ 30 min ~ 60 min ~ 120 min respectively, the 3.4mm/y.(3)370oC extruded alloy is annealed. With the increase of annealing time, the grain size of the alloy increases and the second phase continues to precipitate. The results of cell experiments show that the corrosion rate of as-cast, solid solution, extruded and annealed alloys is higher than that of as-cast, extruded and annealed alloys. The corrosion rate of magnesium alloy has a great effect on the adhesion, activity and differentiation of MC3T3-E1 osteoblasts on its surface. The second phase content and grain size of the alloy were changed by heat treatment, which affected the corrosion resistance of the alloy, and the accelerated corrosion rate inhibited the cell adhesion, proliferation and differentiation.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG146.22;TG166.4;TG379

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