Preparation And Structure Characterization Of The Porous Anodic Alumina Template

With the development of nanotechnology, the structure controllable preparation of porous anodic alumina (PAA) template has attracted people's attention. PAA template has many features, its preparation process is simple and inexpensive preparation of nano-materials has broad application prospects.The sulfuric and oxalic acid was used as electrolyte in the experiments and the two-step anodization method was adopted to fabricate highly ordered porous anodic alumina (PAA) templates. The crystal structure of pure aluminum and the annealed aluminum was characterized by X-ray diffraction (XRD). Field-Emission scanning electron microscope (FE-SEM) and atom force microscope (AFM) was used to observe the surface and cross morphology of porous anodic alumina templates. We can well control the pore diameters(20-100nm),interpore distances(50-130nm),and pore depths(200nm-60μm),pore densities 109-1010/cm2. In this paper, we systematically studied the PAA fabrication techniques. The anodizing process was carried out at different electrolytes, different anodizing voltages and various electrolyte concentrations. The suitable processing conditions have been obtained to prepare the structure controllable PAA templates. The forming process and mechanism of PAA template was discussed also.The results show that:Aluminum pretreatment (such as high temperature annealing, electrochemical polishing) on the preparation of highly ordered PAA templates play an important supporting role. When other anodizing conditions remain unchanged, PAA template aperture increased and pore density decreased with anodizing voltage increased. The PAA template pore sizes were increased and interpore distance remains unchanged when the oxalic acid concentration increased. PAA oxidation time mainly affects the thickness of the template, appropriately increasing the oxidation time, porous anodic alumina template ordering further. The ordered array of pits at aluminum surface is important for formation of highly ordered porous anodic alumina template, the uneven distribution of electric field and self-organization theory can be used to explain the orderly process of hole's nucleation and growth.Highly ordered TiO2 nano-arrays were deposited by electron beam evaporation on the lab-fabricated porous anodic alumina templates. Field-Emission scanning electron microscope (FE-SEM) was used to observe the surface and cross morphology of TiO2 nano-arrays. The results show that:Highly ordered TiO2 nano-arrays was prepared by electron beam evaporation on different structures PAA templates as substrates. TiO2 nano-arrays growing in the plane and vertical directions, the growth of TiO2 nano-arrays formed have the same structure with the base sequence. PAA template structure can be regulated by changing its on TiO2 nano-array structure. The possible mechanism responsible for the nano-arrays formation was also tentatively discussed.