Nanoporous anodic aluminium oxide for magnetic, mechanical and energy efficient systems

Abstract

This dissertation presents four different aspects of magnetism in relation to Anodic Aluminium Oxide (AAO) membranes. The fabrication of nanoporous AAO templates has been extensively studied in last two decades using the conventional mild (MA) and hard anodization (HA) techniques but, less attention has been paid to the newly developed pulse anodization (PA) method. Electrochemical growth of HA-AAOs under magnetic fields has been studied. It surprisingly resulted in the formation of superplastic, peel-able amorphous AAO nanotubes with tens of microns of length and ~100 nm outer diameters and ~30 nm inner diameter. Quantitative force measurements with AFM microscope were performed on the oxide nanotubes and the results showed a breaking strain of 81% which is over 100 times higher than conventional crystalline aluminium oxide. Many AAO templates were grown by MA and HA methods in a PTFE electrochemical cell using a solution containing 0.3 M oxalic acid with applied voltages ranging from 5 to 140 V. The resulting samples show a weak ferromagnetic magnetization on average of 45 Am-1.