A Study On Assemble System Of AAO Template And V₂O₅ Nanotubes

Due to their surprising physical and chemical properties nano-materials have great potential applications in catalyst, filtrating light, light absorption, medicine, magnetism media. At the same time, nano-materials will also promote the development of the foundational researches. Anodic aluminium oxide membrane (AAO) that is fabricated by anodic oxide of Al not only has a simple process, but also contains uniform parallel pores and high pore density. Furthermore, the pore diameter is controllable according to practical needs. These characteristics allow the use of AAO as template. One-dimensional nano-material synthesized by AAO template has attracted many researchers and has been studied deeply in recent years. Firstly this thesis summarized the newest progress of using AAO template to prepare functional nano-materials. On this base, we prepared V₂O₅ nanotube arrays by combining sol-gel and template methods. The main results and conclusions can be summarized as follows:AAO template with highly ordered pores was fabricated in acidic solution by using anodization method. XRD result showed the AAO membrane was amorphous. The AAO membrane had two layers: the porous layer and the barrier layer. The barrier layer was compact and imperforate. In the porous layer, the pores were hexagonally distributing, and parallel each other, the pores were perpendicular to the membrane surface and had great aspect ratio.The pretreatment of high temperature anneal had evident effect on the orderliness of the AAO. The experiment results showed that two-step anodization method was better than one-step anodization method. The membrane pores of one-step anodization method were polygonally distributing and not circle. While that of two-step anodization method were hexagonally distributing within several microns. The pore apertures were same and parallel with each other. The pores were ideally circle. The cell structures which were left from the first anodization had induced the second anodization, so two-step anodization method could form order pores quickly and didn't need a long time.With the increase of reaction time, acidic concentration, temperature and anodize voltage, the membrane would become thick and the pore density become small. But the effect of these factors on pore apertures and orderliness were different: two-step anodization method could form order pores quickly, the pore apertures would increase with the prolong of time. The effect of acidic concentration on orderliness was small. With the increase of acidic concentration, the pore apertures were reduced first, and then increase. The orderliness was good at high temperature, but the reaction was instable if the temperature was too high and the orderliness would become bad. With the increase of anodize voltage, the orderliness became bad. The best conditions of preparation in oxalic acid were 0.3mol/L, 20℃, 40V. The AAO membranes with different parameters could be obtained by changing anodize conditions. The electric field played a dominant role in the forming process of porous alumina and final ordered membrane. The high transmittance of AAO was the important precondition for optical nano-material preparation.Highly ordered V₂O₅ nanorube arrays were synthesized in the pores of AAO by sol-gel method. Investigation of XRD and SAED demonstrated that V₂O₅ nanotubes were orthorhombic. XPS analysis further proved that valance of vanadium in nanotubes was +5. SEM and TEM results showed that V₂O₅ nanotubes with uniform diameter form highly ordered arrays. A blue shift of the optical absorption edge of V₂O₅ nanotubes in AAO was observed, which was ascribed to the quantum size effect and superficial effect. The pore walls were negatively charged and the sol particles were positively charged, which caused sol particles to adsorb to the pore walls of the template and resulted in the formation of V₂O₅ nanotubes.