镁合金智能自修复防护体系的构建及自修复防护机理研究

Magnesium and its alloys have limited application in corrosive environments because of their poor corrosion resistance. To greatly improve the corrosion resistance of magnesium alloys and thus extend their applications in rigorous environments, the "smart" self-healing anticorrosion protective systems for magnesium alloys, which can promptly respond to changes in the local environment and heal the coating defects, are urgently desired. In this proposal, the construction strategies of such "smart" self-healing anticorrosion protective systems are proposed and the "smart" self-healing anticorrosion mechanism is expected to elucidate..First, the self-healing anticorrosion protective systems for magnesium alloys will be developed, which are based on the inhibitor-containing hybrid sol-gel coating matrix. Secondly, the pH-dependent triggered release structure, which has the pH-sensitive polymer shell and the effective inhibitor core, will be induced to endow the protective system with intelligence. The "smart" self-healing anticorrosion protective system can promptly respond to the pH changes in the corrosive medium that caused by the coating damage and release the effective inhibitor to heal the coating defects, which will automatically stop as the corrosion stops and the medium pH recovers. In order to elucidate the "smart" self-healing anticorrosion mechanism, the EIS technique will be employed to evaluate the self-healing anticorrosion protective ability of the system. The in situ techniques such as SKP/SVET, AFM, Raman and IR as well as the ex-situ techniques such as SEM, TEM, EDS and XPS, will be used in monitoring the "smart" self-healing process and in characterization of the "smart" self-healing anticorrosion protective systems. The self-healing dynamics will be studied and the correlative parameters will be calculated based on the physical chemistry theories. Finally, the "smart" self-healing anticorrosion mechanism will be proposed, which can guide the optimizing of the system construction. .The achievements of this project will undoubtedly promote the engineering applications of magnesium alloys and create countless new opportunities for developing and applying of the "smart" self-healing anticorrosion protective techniques.

镁合金化学性质活泼，并且其表面防护体系作用有限、不具有自修复功能，这导致镁合金耐蚀性差，严重阻碍其发挥性能优势。.本项目拟构建镁合金智能自修复防护体系并研究其自修复防护机理，具体包括：基于对成膜基质、有效缓蚀组分的优选，借助溶胶-凝胶模板技术构建镁合金自修复防护体系；基于对有效缓蚀组分（"核"）、pH敏感性高分子材料（"壳"）的优选，借助原位模板/自组装技术构筑"核/壳"纳米结构将pH敏感性刺激-响应系统引入自修复防护体系中，实现其智能化。采用电化学阻抗谱方法评价体系的自修复防护效果，采用电镜、能谱等技术表征体系的微观形貌及组成，采用扫描开尔文探针/扫描振动电极技术、原子力显微镜、拉曼光谱、红外光谱等原位微区技术获取自修复界面的动态特征；利用物理化学理论求算自修复过程的动力学参数；提出自修复防护机理，指导体系优化。本项目将为奠定镁合金工程应用基础、发展金属智能自修复防护技术提供指导和参考。

镁合金化学性质活泼、极易腐蚀，其现有的表面防护体系作用有限、不具有自修复功能，严重阻碍了镁合金的应用。.针对上述问题，本项目构建了镁合金智能自修复防护体系并研究了其自修复防护机理。主要研究内容包括：(1)采用稀土盐溶液水热的方法制备了具有网状结构的稀土（氢）氧化物膜层作为防护体系的底膜，采用溶胶-凝胶法制备了致密的无机-有机杂化硅膜作为防护体系的外膜；(2)采用极化曲线等测试优选出了硅酸钠和硫脲两种镁合金高效缓蚀组分作为“核/壳”结构缓蚀剂的“核”材料，以pH敏感区间、润湿性质等为指标优选出了聚乙烯亚胺/聚苯乙烯磺酸钠高分子材料作为“核/壳”纳米结构缓蚀剂的“壳”材料；在此基础上，经过大量工艺摸索和优化，制备了pH 值敏感性“核/壳”结构缓蚀剂并对其进行了系列表征。结果显示，制备的“核/壳”结构缓蚀剂呈球形，粒径约为150纳米，壳厚约为20-30纳米，其壳为聚乙烯亚胺/聚苯乙烯磺酸钠亲水材料，核则为负载了缓蚀组分硅酸钠或硫脲的疏水性聚苯乙烯基质，该“核/壳”结构缓蚀剂具有高度pH值敏感性，“壳”材料可以灵敏地响应腐蚀介质pH值的改变而可控性释放作为“核”的缓蚀组分。(3)采用自组装方法将pH 值敏感性“核/壳”纳米结构缓蚀剂引入到稀土（氢）氧化物底膜中，然后喷涂无机-有机杂化硅膜，从而构建出镁合金智能自修复防护体系。对该体系的自修复防护测试结果显示，该体系被划伤后，膜层破损、金属腐蚀引起腐蚀介质局部pH值升高，pH值敏感性“核/壳”结构缓蚀剂的“壳”灵敏响应介质pH值改变、智能性释放高效缓蚀组分“核”，可以在不到6小时内有效修复膜层，抑制腐蚀的进一步发生。(4)对体系智能自修复防护机理的分析表明：pH值敏感性壳材料受pH值影响发生构象改变、可控性释放高效缓蚀组分“核”是实现智能自修复防护的关键。.上述结果对于拓展镁合金的工程应用具有积极推动作用，对于发展其他金属智能自修复防护技术可以提供有益参考。