轻质合金表面等离子体电解氧化膜生长机制的电子显微学研究

Plasma electrolytic oxidation (PEO) films on light alloys (Al, Mg and Ti) have advantages of facile-fabrication, eco-friendly and enhanced performance, and therefore have potential applications on alloy surface treatment. However, the growth mechanism of PEO films are not yet understood and the quantitatively controlled process for film synthesis are not yet established. Herein, this proposal is focusing on the study of growth mechanism of PEO films on light alloys using advanced aberration-corrected transmission electron microscopy (AC-TEM). By combining AC-TEM investigations, Radical Distribution Function (RDF) and Reverse Monte Carlo (RMC) simulations, the ion distributions and atomic structures of materials within pore base, intrinsic oxide layer and near-surface layer will be investigated at nano- or atomic scale, respectively. Then, the evolution of film microstructures by tuning electrolytes, metals and applied high electric fields will be systematically studied. The growth mechanism of PEO films will be further investigated by correlating the microstructural evolutions and the physical processes. Eventually, the proposed growth mechanism will be employed and hopefully lead to applications to enhance and functionalize the surface of light metals. This study will provide the support for establishing the quantitatively controlled process for PEO films synthesis from microstructural perspective, and meanwhile, promote the understanding on the physical mechanisms in high-electric-field-driven metal oxidized process and electrolyte/oxide interfaces.

轻质合金的等离子体电解氧化技术有工艺简单、环保、强化效果好的优点，在合金表面强化领域有巨大的应用潜力。然而，当前对等离子体电解氧化膜的生长机制尚不清楚，也未能建立定量工艺控制理论。本项目拟利用球差校正透射电子显微分析方法，系统开展铝、镁、钛三类轻质合金表面等离子体电解氧化膜生长机制的研究工作。结合球差校正透射电镜表征和径向分布函数、逆向蒙特卡洛模拟等方法，从纳米/埃尺度上分别测定孔道底部、本征氧化层和近表层中离子分布规律和内部的原子结构；通过对比分析，揭示显微结构在电解质离子、金属类型和强电场调制下的演变规律；建立结构演变和物理机制的关联，探究薄膜生长机制；基于理论模型，推进金属表面防护和表面功能化的应用研究。本项目研究将为轻质合金等离子体电解氧化膜的定量调控提供理论依据，同时推动人们对强电场条件下金属氧化和电解液/氧化膜界面物理机制的认识。

轻质合金的等离子体电解氧化技术有工艺简单、环保、强化效果好的优点，在合金表面强化领域有巨大的应用潜力。然而，当前对等离子体电解氧化膜的生长机制尚不清楚，也未能建立定量工艺控制理论。本项目利用球差校正透射电子显微分析方法，系统开展了铝、镁、钛三类轻质合金表面等离子体电解氧化膜生长机制的研究工作。本项目的突破性进展一在于利用微量氟离子添加直接修饰了镁本征氧化层的显微结构和稳定性，大幅提升了镁合金等离子体电解氧化膜的耐腐蚀性能，为等离子电解氧化工艺设计提供了新思路；进展二在于在机理研究的基础上首创了“大于200伏高压阳极氧化”技术，并利用该技术制备了具有光催化活性和SERS应用潜力的阳极薄膜，这对于深入认识高压下溶液/氧化膜界面物理具有重要的理论意义和应用研究指明了方向。