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多孔阳极氧化铝(PAA)的孔径大小及其均匀性可通过扩孔进行改善。以3%(质量分数)磷酸作为刻蚀液,在实现PAA孔径扩大的同时,详细研究了三维状况下孔径形态的实时演变过程。发现PAA孔加宽在表面和截面2个方向上同时进行。在表面扩孔中,磷酸逐层蚀刻PAA内壁多层结构,随着扩孔时间的增加,扩孔速率不同。在截面扩孔中,当扩孔时间达到某一定值时,由于扩孔速率不同,PAA顶部的扩孔过程较底部相对较早完成,随后顶部扩孔速率逐渐降低,底部扩孔速率逐渐增加。当扩孔完成时,形成均一性良好的理想圆形小孔。同时发现,过度增加扩孔时间,PAA基元结构将被破坏,并由于高纵横比形成纳米线,随后被刻蚀溶液腐蚀。结合多层结构理论详细阐明了三维PAA的实时扩孔机制。
Pore size and uniformity of porous anodic aluminum oxide (PAA) can be improved by reaming. Using 3% phosphoric acid as etching solution, the real-time evolution of pore size under three-dimensional conditions was studied in detail while expanding the pore size of PAA. PAA holes were found widened in both surface and cross-sectional direction simultaneously. In surface reaming, phosphoric acid layer-by-layer etching PAA multi-layer structure, with the reaming time increases, reaming rate. In the reaming process, when the reaming time reaches a certain value, the reaming process at the top of the PAA is relatively earlier than the bottom due to the different reaming rates, and then the reaming speed at the top gradually decreases and the reaming rate at the bottom gradually increases. When the reaming is completed, an ideal circular hole of good uniformity is formed. At the same time, it was found that, when the hole expanding time is increased excessively, the PAA structure will be destroyed and the nanowires will be formed due to the high aspect ratio, which will then be eroded by the etching solution. Combined with the multi-layer structure theory, the real-time reaming mechanism of three-dimensional PAA is elaborated.