Fabrication, Characterization Of Porous Anodic Alumina And Its Special Porperties

The PAAs with highly ordered nanopore arrays have attracted more and more attentions, owing their manipulated pores within large range and relatively easy and low-cost processing. The PAAs have diverse applications in the fabrication of nanostructured materials and photonic devices. In this thesis, we focused on an improved two-step anodization technique and the effect of some experimental parameters, as well as the optical constants of the PAA fabricated by the imporved two-step anodization technique and the mechanism of the serreate structure.We gave a brief introduction on the concept of nanotechnology.The main apparatus used for characterizing nanostructured materials were also introduced. Then, the major research developments of PAA films were discussed in details to present a full and accurate knowledge about PAA, including the structure models, formation mechanisms, fabrication techniques, and main applications.We proposed an improved two-step anodization technique through combining the first hard anodization in C2H2O4 with the second mild anodization in H3PO4, which successfully overcome the drawbacks of irregular top surfaces in the conventional two-step hard anodization in C2H2O4 and disordered pore arrays in the two-step mild anodization in H3PO4. The key success of our method is the strong guidance effect of the first hard anodization on the second mild anodization. Highly-ordered (both top and bottom surfaces) porous anodic aluminum (PAA) membranes with interpore spacing from 220-350nm have been realized under anodizing voltages from 100 to 150V. The interpore spacing is only determined by the first anodizing voltage, while the pore diameter can be manipulated in the second step by adding ethanol in the H3PO4 electrolyte, changing the H3PO4 bath temperature, and altering the second anodizing voltage. The bath temperature for the steady growth of ordered structures can be expanded up to 20oC, from which the average activation energy can be yielded.We employed optical transmission measurements for the study of properties in PAA fabricated using improved two-step anodization technique, and calculated the wavelength-dependent refractive index of the PAA obtained under different voltages. We proposed the refractive index decreased with higher impurity concentration of PO43- and was affected by the molecular structure in some extent.When the anodizing voltage is lower than the self-ordered voltage, the PAAs tend to form serrate structure. So we employed the cause and influencing factors of the serrate structure. We proposed that the generating O2 bubbles deformed the oxide to push the oxide grow oblique. When the voltage was low and bath temperature was high, the PAA was loose and easy to form serrate structure. The structure was different with the electrolyte stirring or not and it was also influenced by the electrolyte.This work was supported by the National Major Basic Research Project of 2010CB933702 and the Natural Science Foundation of China under contract 10734020.