Preparation and Characterization of Porous Anodic Alumina Nanostructures

Abstract

This thesis describes the preparation and chacacterization of porous anodic alumina (PAA) membranes and synthesis of metal nanostructures based on PAA templates. The aim of this investigation is to optimize the process parameters and prepare metal nanostructures on the pores of PAA membranes using chemical methods. The effect of process parameters such as anodizaton duration, temperature of electrolytic bath and electrolyte concentration are systematically investigated. In this way pore diameter was found to be tunable from 20 to 100 nm and template thickness acheived varied from 20 to 100 mm. Hexagonal pore array with honeycomb-like structures were obtained via self-organised oxidation process. The pore diameters and interpore distances were varied by changing anodization conditions and pore widening time. The regularity ratio (RR) of the PAA membranes were studied in detail using 2D fast Fourier transform (FFT) analysis. Mechanical properties of PAA membranes such as hardness and Youngs modulus were studied using micro and nanoindentation techniques. PAA membranes obtained in sulphuric acid exhibited an extremely high hardness of 7.5 GPa and Young’s modulus was 146.5 GPa. The optical absorbance and photoluminscenc of PAA membranes were investigated. The PL spectra of PAA membranes showed an assymetrical behaviour in the blue region. This spectrum was divided into two subbands by Gaussian analysis, originating from two kinds of oxygen-deficient centers, F+ (oxygen vacancy with one electron) and F centers (oxygen vacancy with two electrons) respectively. Contact angle measurements of PAA membranes were analysed at different anodization time and pore widening durations. Synthesis of metal nanostructures (Silver and Copper) by chemical method were studied and presented in detail.