镁合金表面自清洁、耐高温复合膜层的制备与表征

目的 在镁合金表面制备自清洁、耐高温复合膜层，拓展镁合金在严酷环境中的应用。方法 采用化学转化-沸水封闭-硬脂酸修饰三步处理，在AZ31镁合金表面制备含有耐高温锆化合物组分的低黏附、超疏水复合膜层。利用场发射扫描电子显微镜(FESEM)表征膜层形貌。利用X射线光电子能谱仪(XPS)表征膜层成分。利用接触角测量仪(CA)和高速摄像机(HSC)表征膜层润湿性和黏附性。以粉笔灰为模拟污染物测试膜层在空气和油相中的自清洁性能。通过高温暴露试验和循环沸水浸泡试验测试膜层的耐高温性能。结果 复合膜层主要由锆/镁的(氢)氧化物及硬质酸盐组成，呈被部分填充的纳米纤维组成的微米网络结构。水在膜层表面的静态接触角为160.4°、滚动角为1°，符合“Cassie-Baxter”模型，膜层具有超疏水、低黏附特性；复合膜层具有优异的自清洁性能和耐高温性能。结论 成功制备了含有耐高温锆化合物组分的低黏附、超疏水复合膜层，该膜层具有自清洁、耐高温性能。

Preparation and Characterization of Self-cleaning and High-temperature-resistant Composite Coating on Magnesium Alloy

The composite coatings with self-cleaning and high-temperature-resistant functions are indispensable for magnesium alloys to widen their application in harsh environments. In this paper, the composite coating that has superhydrophobic and low adhesive characteristics with self-cleaning and high-temperature-resistant functions was prepared on the AZ31 magnesium alloy surface by chemical conversion, boiling-water immersion and stearic-acid modification. The surface morphology of the coating was observed by field emission scanning electron microscopy (FESEM). The chemical composition of the coating was identified by X-ray photoelectron spectroscopy (XPS). The wettability and adhesion of the coating surface to water was evaluated by contact angle measuring instrument (CA) and high-speed camera (HSC). The self-cleaning function of the coating in air and oil (cyclohexane) was measured with chalk powders as the target contaminant. The high- temperature-resistant function of the coating was evaluated by the high-temperature exposure test and boiling-water immersion cycling test. The characterization results indicated that the as-prepared coating was composed of (HYDR) oxides and stearates of Zr and Mg, which presented as partly-filled micro-nets formed by nanofibers. The coating surface had a high static water contact angle of 160.4° and a low roll-off angle of 1°, which indicated that the coating accorded with Cassie-Baxter model and had superhydrophobic and low adhesive characteristics. The coating demonstrated remarkable self-cleaning function in air and oil, and attractive high-temperature-resistant function in air and water. The as-prepared self-cleaning and high-temperature-resistant composite coating in this work is expected to widen the application of magnesium alloys in harsh environments.