晶界对低压电解电容器铝箔腐蚀结构的影响

Influence of grain boundaries on corrosion structure of low voltage aluminum foil

采用扫描电子显微镜和背散射电子取向成像技术分析研究了低压电解电容器用阳极铝箔的腐蚀结构、晶粒尺寸和晶界分布对比电容的影响及相关机理。结果表明,在铝箔的晶界附近,尤其是大角度晶界附近容易出现尺寸较大的腐蚀孔坑或沟道,造成腐蚀结构的不均匀性并降低比电容。该晶界优先腐蚀的现象起因于晶界的高缺陷密度和与之相应的腐蚀电流密度的局部集中。增加晶界密度可以降低杂质原子偏聚程度和电流密度分布的不均匀性,因此在一些特定的电化学腐蚀条件下可以借助减小晶粒尺寸的方式提高比电容。

The corrosion structure, grain size and boundary distribution of aluminum anode foil for low voltage electrolytic capacitor were analyzed and investigated based on observation of scanning electronic microscope and orientation mapping with electron back scattering diffraction technology. It is indicated that large corrosion holes or channels will appear frequently along the grain boundaries, especially along the high angle grain boundaries, which lead to the inhomogeneity of corrosion structure and reduction of specific capacity. The higher defect density and corresponding local concentration of corrosion current density around grain boundaries induce the preferred corrosion of the boundaries. Increasing the boundary density can reduce the segregation of impurity atoms and the distribution inhomogeneity of current density. Therefore, it is possible to increase the specific capacity by means of reducing the grain size under some electrochemistry corrosion conditions.