Li Linwei, Yang Erhui, Yan Zhibin, Xie Xiaomeng, Wei Wu, Li Weizhou
School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China.
School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361024, China.
Materials (Basel). 2022 Jul 28;15(15):5221. doi: 10.3390/ma15155221.
In the current investigation, micro-arc oxidation (MAO) ceramic coatings on aluminum are galvanostatically synthesized at various processing stages in an alkaline silicate system. The resultant coatings are systematically investigated in terms of the following respects: The working voltage and surface sparking evolution over the studied course of MAO are recorded by the signal acquisition system and the real-time imaging, respectively; the phase composition, the surface morphology, and the polished cross-section of the coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) assisted with an energy-dispersive X-ray spectrometer (EDS), respectively. In particular, with the help of a low-rate increase in working voltage, the evolution of the sparks, the energy consumption, and the microstructure development of aluminum in alkaline silicate electrolyte by pre-anodizing are systematically investigated. The results show that the pre-anodized film can accelerate the evolution process of MAO spark and shorten the reaction process in the early stage of MAO reaction, reducing energy consumption and improving the corrosion resistance of the MAO coating. The γ-Al2O3 phase content after pre-anodized is significantly increased in MAO coatings. In particular, the thicker the pre-anodized film (beyond 8 μm) was broken down and fragmentation thinning in the early stage of the MAO process with the presence of micro discharges. This is due to the fact that the electron transition will be released by the emission of radiative recombination and reveals obvious galvanoluminescence (GL) behavior on the surface of the pre-anodized film. Further, based on the present MAO coating microstructure, a model of coating growth after pre-anodized that evolves over time is proposed.
在当前的研究中，在碱性硅酸盐体系的不同加工阶段，通过恒电流法在铝上合成微弧氧化（MAO）陶瓷涂层。从以下几个方面对所得涂层进行了系统研究：分别通过信号采集系统和实时成像记录MAO研究过程中的工作电压和表面火花演变；分别借助X射线衍射（XRD）和扫描电子显微镜（SEM）以及能量色散X射线光谱仪（EDS）对涂层的相组成、表面形貌和抛光横截面进行表征。特别是，借助工作电压的低速率增加，系统研究了预阳极氧化在碱性硅酸盐电解液中铝的火花演变、能耗和微观结构发展。结果表明，预阳极氧化膜可以加速MAO火花的演变过程，缩短MAO反应早期的反应过程，降低能耗并提高MAO涂层的耐腐蚀性。预阳极氧化后MAO涂层中γ-Al2O3相含量显著增加。特别是，较厚的预阳极氧化膜（超过8μm）在MAO过程早期会在微放电的作用下分解并破碎变薄。这是因为电子跃迁会通过辐射复合发射而释放，并在预阳极氧化膜表面呈现出明显的电致发光（GL）行为。此外，基于当前MAO涂层的微观结构，提出了一个预阳极氧化后涂层生长随时间演变的模型。
