镁基金属复合生物材料的制备及其性能研究

论 文 题 目 镁基金属复合生物材料的制备 及其性能研究 硕士学位论文 摘 要I摘 要镁及镁合金因与自然骨的力学性能相近且具有良好的生物相溶性，作为可降解的骨植入材料受到很大的关注。但是，镁合金易发生电化学腐蚀,过快的腐蚀速率易导致植入失败。通过调整材料成分、组织结构，采用新的材料制备技术及表面处理等方法制备新的镁合金或镁基复合材料降低材料的腐蚀速率是当今生物材料研究的热点。本研究选用纯镁为基体材料，以镁的氧化物（MgO 陶瓷粉末）或将 20.21wt% ZnO 或 20.21wt% ZnO 与 10wt% HA 的混合粉末作为增强相添加添加到镁基体中，采用粉末冶金的方法，制备了三种镁基金属复合材料，即：不同 MgO 含量的 MgO/Mg 复合材料，或通过原位生成 MgO 和 Mg-Zn 合金，制备的 MgO/Mg-Zn/Mg 复合材料或 MgO/Mg-Zn/HA/Mg 复合材料。最后采用阳极氧化法和阳极氧化-聚乳酸涂覆的方法在复合材料的表面分别制备了 MgO 涂层和 PLA/MgO 复合涂层。对复合材料的力学性能（主要包括表面硬度和抗拉强度）进行了测试。通过浸泡法（包括 pH 值测量法和失重法）和电化学方法（动电位扫描法和交流阻抗法） ，研究复合材料和涂层在人工模拟体液（SBF 液）中的腐蚀速率及腐蚀行为。运用 X 射线衍射仪（XRD）和扫描电镜（SEM）等先进设备对复合材料抛光表面、腐蚀表面、腐蚀产物和涂层的物相、成分和形貌进行表征。主要研究结果如下：1）采用粉末冶金的方法制备了第二相含量精确，分布均匀的MgO/Mg 镁基金属复合材料。模拟体液中的浸泡实验和电化学实验的结果一致表明，复合材料与纯镁金属有类似的腐蚀行为；相对于纯镁金属，复合材料中的 MgO 在镁基体中的均匀、连续分布，可以提高镁基金属复合材料整体的耐腐蚀性能，且随着 MgO 的含量的增加，复合材料的腐蚀降解速率减小；然而，MgO/Mg 复合材料的耐蚀性能的提高部分牺牲了力学性能。复合材料的力学性能随着 MgO 的含量的增加呈减小趋势。2）采用粉末冶金的方法，通过原位反应机理制备了 MgO/Mg-Zn/Mg 和 MgO/Mg-Zn/HA/Mg 镁基金属复合材料。XRD 和 SEM 结果显示，均匀分布于镁基体颗粒间的为 MgO 与 Mg-Zn 金属间化合物的混合组硕士学位论文 摘 要II织或 MgO 与 Mg-Zn 金属间化合物和 HA 的复合组织。模拟体液中的浸泡实验和电化学实验分析结果一致表明，MgO/Mg-Zn(/HA)/Mg 复合材料与纯镁有类似的腐蚀行为，相对于 MgO/Mg 复合材料，MgO/Mg-Zn(/HA)/Mg 镁基金属复合材料呈现出更好的耐腐蚀性能；力学性能研究表明，MgO/Mg-Zn(/HA)/Mg 复合材料的力学性能有显著的提高；HA 在复合材料中的存在，能提高材料的力学性能，但对提高复合材料的耐蚀性贡献不大。3）以 MgO/Mg-Zn/Mg 复合材料为基底，在不同的阳极电位下制备了不同厚度的 Mg(OH)2涂层，其中 0.2V 的电位下制备的涂层最致密，但厚度难以提高。致密的 Mg(OH)2涂层经 450煅烧后得到多裂纹的 MgO 涂层，再经聚乳酸 PLA 溶液的涂布后，不仅可以起到封孔的作用，还能在 MgO 涂层的表面覆盖一层新的 PLA 高分子涂层，得到 PLA/MgO 复合涂层。动电位扫描和交流阻抗的结果表明，多裂纹的 MgO 涂层可以对基底材料起到一定的保护作用，但经 PLA 高分涂覆后，可以更有效地阻止介质与基底接触，从而进一步提高材料的耐蚀性能。关键词 镁基金属复合材料，生物降解，耐蚀性，粉末冶金，阳极氧化硕士学位论文 ABSTRACTIIIABSTRACTMagnesium and its alloys are attracting more and more attentions as implant materials for its relative close mechanical properties to natural bone and good biocompatibility. Unfortunately, magnesium alloys degrade too fast due to the positive activities in chemistry, which may cause the implantation failed. Therefore, the study on decreasing the corrosion rate of Mg alloys and Mg-based composites through adjusting the components and structure of the materials and/or adopting new fabrication technology and surface modification becomes a hotspot.In this study three kinds of Mg-based metal matrix composites (MgO/Mg, MgO/Mg-Zn/Mg and MgO/Mg-Zn/HA/Mg) were prepared by powder metallurgy, wherein, pure magnesium, a macro-element of human body, was used as matrix and MgO powder or 20.21wt% ZnO or a powder mixture of 20.21wt% ZnO and 10wt% HA as the addition. MgO coating and MgO/PLA complex coating were fabricated on MgO/Mg-Zn/Mg composite surface, respectively, by using Anodic Oxidation and combined Anodic Oxidation and dip coating of PLA process. The mechanical properties of the composites, i.e. the tensile strength and hardness of the composite were tested. The corrosion properties of the composites with and without coatings were studied in simulated body fluid (SBF) by immersion test (weight loss test and pH value measurement) and electrochemical measurements including potentiodynamic polarization and electrochemical impedance spectra (EIS). The phases and the morphology of the polished, corrosion product and the coating of the specimens were analyzed by means of X-ray diffraction (XRD) and Scanning electron microscope (SEM) equipped with EDX, respectively. The results are summarized as follows:1) MgO/Mg composite materials containing 5wt%, 10wt% and 20wt% MgO as reinforcement phase were fabricated by powder metallurgy. The results of SEM of these four composites show that MgO phases evenly distribute in Mg matrix. The results of immersion tests and electrochemical measurement in SBF show that MgO/Mg composite materials have similar corrosion mechanism as pure Mg metal and the 硕士学位论文 ABSTRACTIVdistribution of MgO in Mg matrix plays an important role in the improvement of corrosion resistance of composite materials. The corrosion resistance increases with the increase of MgO addition. The MgO/Mg composite material with 20wt% MgO exhibits the best enhanced corrosion resistance. However, the mechanical properties of MgO/Mg composite deteriorate with the increase in the amount of MgO. 2）MgO/Mg-Zn/Mg composite and MgO/Mg-Zn/HA/Mg composite reinforced with MgO ceramics and Mg-Zn intermetallics and with MgO ceramics, Mg-Zn intermetallics and HA ceramics, respectively, were fabricated using pure magnesium powder and 20.2wt%ZnO powder by powder metallurgy. The results of XRD and SEM indicate that compound of MgO and Mg-Zn or compound of MgO, Mg-Zn and HA uniformly and consecutively dispersed in Mg matrix. The results of immersion tests and electrochemical measurements in SBF are consistent, indicating that the corrosion mechanism of the composite is the same as that of pure Mg, and compared with pure Mg, the uniformly and consecutively distributed compound in Mg matrix, together with the addition of Zn element greatly contribute to the improvement of corrosion resistance and mechanical properties of the composite. Meanwhile, mechanical properties of the composites were close to those of natural bone. The research also indicates that the existence of HA in matrix was helpful to the enhancement of mechanical properties while do little to corrosion resistance.3）The as-grown Mg(OH)2 coating on the surface of MgO/Mg-Zn/Mg composite was deposited under four anodic voltages. The results show that the coating deposited at 0.2V was the most compact, whereas its thickness can hardly increase. After heat-treated under 450, the compact coating was converted to multi-cracked MgO. Complex coating of MgO and PLA on composite surface was prepared by dipping the composite substrate with MgO coating into PLA solution. The PLA not only functions as a sealant, but also as a new PLA macromolecule cover on the surface of MgO. The electrochemical measurement results of composite with MgO coating and MgO+PLA complex-coating disclose that porous MgO coating can slightly protect the substrate while the 硕士学位论文 ABSTRACTVcomplex-coating could significantly improve the corrosion resistant of the composite.KEY WORDS Mg-based metal matrix composite, bio-degradable, corrosion resistance, powder metallurgy, anodic electro-deposition硕士学位论文 目录VI目 录摘 要 .IABSTRACT.III目 录 .VI符号、图形符号说明 .IX第一章 绪 论 .11.1 生物材料及其发展现状与趋势 .11.1.1 生物材料概述 .11.1.2 生物材料的现状 .21.1.3 生物材料发展趋势 .31.2 镁及其相关材料概况 .31.2.1 纯镁及镁合金的临床实验 .31.2.2 镁基复合材料及其研究现状 .51.3 镁元素及合金元素对人体的意义 .71.3.1 镁元素对人体的意义 .71.3.2 锌元素对人体的意义 .81.3.3 合金元素对人体的意义 .81.4 提高镁及其相关材料耐蚀性能的方法 .91.5 本研究的选题思路、目的与意义 .121.5.1 本研究的选题思路 .121.5.2 材料设计原理 .131.5.3 本研究的目的 .141.5.4 拟开展的研究内容 .151.5.5 本研究的意义 .15第二章 实验过程 .162.1 研究方案 .162.2 实验材料、试剂、仪器及设备 .172.3 材料极样品的制备 .192.3.1 HA 的制备 .192.3.2 镁基 MMC 的制备 .202.3.3 材料预处理 .22硕士学位论文 目录VII2.3.4 涂层的制备 .222.4 实验方法 .232.4.1 力学性能的研究 .232.4.2 失重腐蚀 .232.4.3 电化学实验 .242.4.4 涂层的腐蚀性能测试 .242.5 元素、相成分及形貌分析 .24第三章 MgO/Mg 复合材料的性能研究 .253.1 MgO/Mg 复合材料的显微组织 .253.2 MgO/Mg 复合材料的力学测试 .273.3 MgO/Mg 复合材料的浸泡实验 .283.4 MgO/Mg 复合材料的电化学腐蚀 .303.5 MgO/Mg 复合材料在 SBF 溶液中腐蚀机理 .323.5.1 基相（纯镁）的腐蚀机理 .323.5.2 第二相的作用 .353.6 性能综合分析 .373.7 本章小结 .38第四章 MgO/Mg-Zn(/HA)/Mg 复合材料的性能研究 .394.1 HA 与 MgO/Mg-Zn(/HA)/Mg 复合材料的表征 .394.1.1 HA 的表征 .394.1.2 MgO/Mg-Zn(/HA)/Mg 复合材料的表征 .404.2 MgO/Mg-Zn(/HA)/Mg