Origin of self-organisation in porous anodic alumina films derived from analogy with Rayleigh-Benard convection cells
Origin of self-organisation in porous anodic alumina films derived from analogy with Rayleigh-Benard convection cells
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DOI：
10.1039/c1jm13898g
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发表时间：
2011-01-01
影响因子：
--
通讯作者：
Schneider, Joerg J.
中科院分区：
文献类型：
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作者：
Pashchanka, Mikhail;Schneider, Joerg J.
多孔阳极氧化铝（PAOX）具有不同的实际应用（如：G.具有均匀孔径的过滤器、吸附剂、用于功能性纳米材料的多孔模板），但对形成机理仍然知之甚少。铝在一定浓度、温度和较高的电极电位下，在某些酸的水溶液中进行阳极氧化时，会形成六方有序孔。今天，有限的范围内的孔径和六方有序的程度达到经验发现的条件。本文提出了一个理论模型来解释多孔阳极氧化铝中蜂窝状结构的出现。所提出的机制是基于一个耗散的自组织过程，而不是早期接受的预形成致密氧化铝的场辅助溶解。我们的分析基于这样的概念，即铝阳极附近的电解质电流以与众所周知的Rayleigh-Benard对流相同的方式组织。一个简单而有效的方法来预测孔隙形成的未开发的电解质的建议。理论上的考虑的有效性，实验证实了在一种新的电解质甲酸水溶液中的六边形排列的多孔氧化铝的生长。
Porous anodic aluminium oxide (PAOX) has different practical applications (e. g. filters with uniform pore sizes, adsorbers, porous templates for functional nanomaterials), but the formation mechanism is still poorly understood. Equal-sized hexagonally ordered pores are formed during anodic oxidation of aluminium in water solutions of some acids at certain concentrations and temperatures, and comparatively high electrode potentials. Today, a limited range of pore diameters and the degree of hexagonal ordering are reached with empirically found conditions. Here, a theoretical model explaining the appearance of honeycomb structure in porous anodic alumina is presented. The proposed mechanism is based on a dissipative self-organization process, but not on the earlier accepted field-assisted dissolution of pre-formed dense alumina. Our analysis rests on the concept that electrolyte currents near aluminium anode are organized in the same way as well-known Rayleigh-Benard convection currents. A simple yet effective way to predict pore formation in unexplored electrolytes is suggested. The validity of theoretical considerations is experimentally confirmed by the growth of hexagonally arranged porous alumina in a new electrolyte-aqueous formic acid solution.