基于脉冲阳极氧化的氧化铝结构调控与机理研究

Preparation of anodic aluminum foils with high specific capacitance and excellent performance is the prerequisite for miniaturization, lightweight, and high-quality of aluminum electrolytic capacitor, which is also the key to promote the level of aluminum electrolytic capacitor. The properties of anodic aluminum foils mostly depend on anodization. For traditional DC anodization, space-charge layer is the dominant factor resulting in degradation in performance and reduction in anodic efficiency. In present proposal, pulse anodization technique is first proposed and formation system with same aluminum electrodes is adopted. Alternating electric field is used to suppress the formation of space-charge laryer, resulting in the large improvement in the specific capacitance, anodization efficiency and production efficiency. Firstly, by investigating the evolution law of resistance, capacitance and inductance as well as conversation of energy during anodization, compensating circuit for resistance, capacitance, inductance and energy recovery circuit are designed. The pulse power supply is developed. Secondly, the effect of pulse anodization conditions on formation of hydrated alumina, growth of crystal alumina, generation of joule heat, specific capacitance of aluminum foil, and anodization efficiency is investigated to realize regulation of structure and properties of anodic film as well as obtain anodic aluminum foils with high specific capacitance and excellent performance. Finally, migration characteristics of Al3+ and anion as well as the evolution of space-charge laryer in anodic film during anodizing are studied via inspecting micro-structure and macro-performance of anodic film. Also law of energy conversion is discussed. Then pulse anodization mechanism is revealed.

制备高比容、高性能阳极铝箔是实现铝电解电容器小型化、轻量化、高品质化的前提，也是提升铝电解电容器水平的关键。阳极铝箔性能主要取决于阳极氧化，传统直流阳极氧化中的空间电荷层是阳极铝箔性能劣化、阳极氧化效率低下的主要原因。本项目首次提出正负脉冲阳极氧化技术，采用对称铝电极体系，利用交变电场抑制空间电荷层形成，实现阳极铝箔比容、阳极氧化效率与生产效率的大幅提升：通过探讨阳极氧化过程中电阻、电容和电感的演变规律以及能量转化，设计电阻、电容和电感补偿电路与能量回收电路，优化脉冲电源；通过研究脉冲阳极氧化条件对水合氧化铝形成、晶态氧化铝生长、焦耳热产生、铝箔比容、阳极氧化效率的影响，实现氧化膜结构与性能的调控，获得高比容、高性能阳极铝箔；通过对阳极氧化膜的微观信息与宏观性能的表征，考察Al3+和阴离子在正负脉冲阳极氧化过程中的迁移特性，研究空间电荷层演变过程，探讨能量转化规律，揭示正负脉冲阳极氧化机理。

为了匹配消费电子、通讯及工业领域的小型化、轻量化、高品质化需求，追求高比容、高性能的阳极铝箔是铝电解电容器领域的基本方向，也是竞争高端产品领域的关键。阳极氧化过程对阳极铝箔的电性能至关重要，但传统直流阳极氧化不可避免的伴随着空间电荷层的出现，是阳极铝箔性能劣化、整体能耗增加和阳极氧化效率低下的重要原因。本项目首次提出改变电压加载的方式，利用交变电场抑制空间电荷层形成，实现正负脉冲阳极氧化技术，从而使对称脉冲样相比与直流标样CV值提高了6.98%。考虑到阳极氧化过程中负载的变化，调节实际电路中的电阻、电容和电感，设计出正、负脉冲独立可调，频率范围10~0.001 Hz，微秒级延迟的脉冲电源；通过研究脉冲阳极氧化氧化膜结构和性能，确定其由γ-Al2O3和Al2O3·xH2O组成，耐腐蚀时间延长1.8倍，脉冲样阳极铝箔的耐击穿场强为0.892 V·nm-1，比直流标样高8.1%；通过研究阳极氧化过程，发现脉冲与直流的产气副反应耗电比为0.926：0.957，形成液中Al3+的溶解减少35.9%，氧化膜中B元素含量减少10.0%以及铝箔表面Al2O3·xH2O的减少28.4%，表明脉冲阳极氧化的氧化效率高，副反应少；通过研究阳极氧化膜的微观信息，引入TiO2并观察其分布，表明在正负脉冲阳极氧化过程中Al3+离子和O2-离子的迁移距离比大约为1:2；通过对阴极材料的改性和表征，获得改性阴极材料CNTs/Pt和CNTs/Ni，作为阴极进行阳极氧化，整体能耗可以下降6.18%和2.9%；通过对焦耳热产生及耗散，阳极氧化系统的能耗分析，对称脉冲阳极氧化电源系统能耗2866 J·cm-2，比直流的3153 J·cm-2减小9.1%。对称脉冲化成槽加热系统耗能1764 J·cm- 2比直流3060 J·cm-2节省能量 42.4%。得出对称脉冲阳极氧化综合节能 25.5%。脉冲阳极氧化的阳极箔具有高比容、高性能的同时，相比直流阳极氧化更节能，生产效率更高，因而具有广阔的市场前景。