【作者】 孙勐；

【导师】 张法智；

【作者基本信息】 北京化工大学 ， 应用化学， 2007， 硕士

【摘要】 水滑石（LDHs）作为一种阴离子型层状功能材料，广泛应用于国民经济多个领域，如作为新型高性能催化材料、吸附材料、分离材料、功能性助剂材料、生物材料、医药材料等。如将这种具有巨大应用价值的LDHs材料薄膜化或者固定化，在光、电、磁等领域将会有着更为广泛的应用前景。本论文采用旋涂技术，在AZ31镁合金表面上制备了MgAl-LDHs薄膜，分析了其形貌结构、对AZ31镁合金耐腐蚀性能的改善，并探讨了其腐蚀机制。首先本论文以纳米尺度均分散的水滑石溶胶为前体，采用旋涂法，制备得到了均匀致密的MgAl-CO₃^2--LDHs薄膜。通过XRD、SEM、TEM等表征，探讨了这种LDHs薄膜的形貌结构。研究认为，该薄膜的制备是一个横向切向力与溶剂的高速挥发共同作用的过程。在旋涂法制备过程中，首先是胶体逐渐变簿，多余胶体流到基片周边并以液滴形式脱离为主要特征，只要转速恒定，整个基片上胶体层以均一的速度变薄。随着胶体层的变薄，溶剂的挥发在胶体变薄过程中占主导地位。经历上面两个阶段后，由于粘性效应，胶体内部形成一个微观流体网络，此时，任何挥发性溶剂的挥发将成为主导因素。胶体发生有效的凝结，因为溶剂的挥发使得溶胶的粘度大大提高，加速胶体的凝结。最后，随着溶剂的剧烈挥发，形成了颗粒垂直于c轴取向的LDHs薄膜。然后，本论文将MgAl-CO₃^2--LDHs薄膜旋涂到AZ31镁合金表面上，在一定的工艺条件下，探讨了溶胶浓度和旋涂次数对LDHs薄膜厚度的影响，研究了相对控制LDHs薄膜厚度的可能性。分析了旋涂LDHs薄膜对AZ31镁合金耐腐蚀性能的改善程度，发现旋涂LDHs薄膜使得AZ31镁合金的腐蚀电位升高了286mV，腐蚀电流密度变为原来的1／40，耐腐蚀性能显著提高。最后，通过电化学阻抗谱曲线，分析了旋涂LDHs薄膜的腐蚀过程，结合腐蚀过程的SEM表征，探讨了旋涂LDHs薄膜腐蚀过程中的可能机制，由于旋涂LDHs薄膜中LDHs颗粒呈垂直于c轴取向排布，且层层紧密堆叠，认为旋涂LDHs水滑石薄膜的腐蚀机制为Warburg效应，即切向扩散。更多还原

【Abstract】 Layered double hydroxide （LDHs）, also known as anionic orhydrotalcite-like clays, are currently of intense academic and industrialresearch interests, in part, because of their properties as catalysis and catalystprecursors, adsorption, separation, biology and medicine materials. Filming orimmobilizing LDHs materials will enlarge its usability in optic, electrical,magnetical fields. In our work, LDHs films were prepared by spin-coating thenanosized LDHs sol on AZ31 Mg alloys. The structure of the LDHs films wasdiscussed. Spin-coated with LDHs as the coatings, corrosion resistanceperformance of AZ31 was remarkably improved. The corrosion mechanism ofspin-coated LDHs films were also analyzed.At first, impact and uniform MgAl-CO₃^2--LDHs films were prepared byspin-coating nanosized LDHs sol. By the measurements of XRD, SEM, TEM,the structure of this film was discussed. From the results above, We inferredthat the collaboration of revolving force and the rapid volatilization lead to theformation of this film. During the preparation of spin-coated LDHs films, firstof all, the sol become thincr as the spin-speed increase, the excrescent sol flewto edge of the substrate, then it dropped. When the spin-speed is fixed, the thickness of sol on the substrate decreased at constant velocity. As the solbecome thiner, the rapid volatilization of the solvent dominated the thinningprocess of the film. At last, the LDHs films with the plates perpendicular tothe c-axis were formed.The corrosion resistance performances of spin-coated LDHs films wascharacterized by the EIS and the non-steady state polarization curves. We canconcluded that the corrosion resistance of spin-coated AZ31 was improvedgreatly. The corrosion effects of spin-coated LDHs films could be explained asWarburg effects.更多还原