Schwirn Kathrin, Lee Woo, Hillebrand Reinald, Steinhart Martin, Nielsch Kornelius, Gösele Ulrich
Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany.
ACS Nano. 2008 Feb;2(2):302-10. doi: 10.1021/nn7001322.
The self-ordering of nanoporous anodic aluminum oxide (AAO) in the course of the hard anodization (HA) of aluminum in sulfuric acid (H2SO4) solutions at anodization voltages ranging from 27 to 80 V was investigated. Direct H2SO4-HA yielded AAOs with hexagonal pore arrays having interpore distances D(int) ranging from 72 to 145 nm. However, the AAOs were mechanically unstable and cracks formed along the cell boundaries. Therefore, we modified the anodization procedure previously employed for oxalic acid HA (H2C2O4-HA) to suppress the development of cracks and to fabricate mechanically robust AAO films with D(int) values ranging from 78 to 114 nm. Image analyses based on scanning electron micrographs revealed that at a given anodization voltage the self-ordering of nanopores as well as D(int) depend on the current density (i.e., the electric field strength at the bottoms of the pores). Moreover, periodic oscillations of the pore diameter formed at anodization voltages in the range from 27 to 32 V, which are reminiscent of structures originating from the spontaneous growth of periodic fluctuations, such as topologies resulting from Rayleigh instabilities.
研究了在硫酸（H₂SO₄）溶液中，于27至80V的阳极氧化电压下对铝进行硬阳极氧化（HA）过程中纳米多孔阳极氧化铝（AAO）的自排序情况。直接进行硫酸-HA得到的AAO具有六边形孔阵列，其孔间距D(int)在72至145nm范围内。然而，这些AAO在机械性能上不稳定，会沿着晶胞边界形成裂纹。因此，我们修改了先前用于草酸-HA（H₂C₂O₄-HA）的阳极氧化程序，以抑制裂纹的产生，并制备出D(int)值在78至114nm范围内的机械性能稳健的AAO薄膜。基于扫描电子显微镜图像的分析表明，在给定的阳极氧化电压下，纳米孔的自排序以及D(int)取决于电流密度（即孔底部的电场强度）。此外，在27至32V范围内的阳极氧化电压下形成的孔径会出现周期性振荡，这让人联想到源自周期性波动自发生长的结构，例如由瑞利不稳定性产生的拓扑结构。
