氧化铝纳米线的制备及其形成机理

采用二次铝阳极氧化技术, 制备高度有序的铝阳极氧化膜(AAO模板). 经X射线衍射(XRD)分析, 模板为无定形结构. 将模板放入腐蚀液中, 可获得大量无定形结构的氧化铝纳米线. 模板在800 ℃下退火4 h后, 变为γ-Al2O3结构, 采用类似腐蚀液溶解模板, 得到大量γ-Al₂O₃纳米线. 研究了腐蚀液种类、腐蚀时间和模板晶体结构等因素对生成氧化铝纳米线的影响, 并利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和XRD对纳米线的形貌与结构进行了表征. 结果表明, 在多种腐蚀液中, 均可获得氧化铝纳米线; 随着腐蚀时间的增加, 纳米线的长度增加, 直径变小, 长径比增大; 氧化铝纳米线的晶体结构与所采用模板的晶体结构一致. 此外, 还采用原子力显微镜(AFM)和SEM对AAO膜的表面形貌及其结构特点进行了详细的观测, 并以此为基础讨论了氧化铝纳米线的形成机理, 认为AAO模板本身存在的花状微结构是形成纳米线的内因, 花瓣间的凹陷部位首先被腐蚀断裂, 形成氧化铝纳米线.

Preparation and Formation Mechanism of Alumina Nanowires

The highly ordered anodic aluminum oxide (AAO) film, was prepared with electrochemical anodization method. The as-synthesized AAO film was amorphous as seen from XRD result. Amorphous alumina nanowires were successfully and easily obtained with high yield by etching AAO films in a mixture of H₃PO₄ and H₂CrO₄, NaOH, HCl, or H₃PO₄ solutions. The AAO film annealed at 800 ℃ for 4 h turned to γ-Al₂O₃. γ-Al₂O₃alumina nanowires were also obtained with high yield by etching γ-Al₂O₃ AAO film. Effects of the type of etching solutions, the etching time and the crystalline structure of AAO film on the preparation of alumina nanowire were carefully investigated. And the morphology and structure of alumina nanowires were studied by SEM, TEM and XRD. The results showed that in many kinds of solutions the alumina nanowire could be fabricated by etching method. The length (L) of the nanowire would increase and the diameter (D) would decrease when the etching time became longer, but the ratio of L /D would increase. The crystalline structure of the alumina nanowire was in accordance with that of the AAO film. Furthermore, the morphology of the AAO film was characterized by atomic force microscope (AFM) and SEM in detail. On the basis of AFM and SEM observations, a possible formation mechanism of the alumina nanowire was discussed, and the plum bloom-shape microstructure of the AAO film was considered to be the essential factor deciding the formation of the alumina nanowire.