Chemical composition and structural changes of porous templates obtained by anodising aluminium in phosphoric acid electrolyte

Ordered anodic aluminium oxide (AAO) films were first prepared by anodising in a phosphoric acid electrolyte and then studied extensively and characterised by field emission gun‐scanning electron microscopy (FEG‐SEM), X‐ray diffraction, Raman and infrared spectroscopy at a macroscopic scale. These analyses showed that the as‐prepared AAO film is in fact amorphous, partially hydrated and that its initial global chemical composition can be described, in agreement with previous works, as: Al2O3, 0.186AlPO4 · 0.005H2O. Additional analyses (thermogravimetric analysis, differential thermal analysis and FEG‐SEM) showed geometrical changes of the film structure at different scales, explained by various steps of dehydration and allotropic transformations of the resulting crystallised alumina. However, because their structure remains unchanged up to 900 °C, the phosphoric templates appear to be particularly suitable for applications or processes at medium or high temperatures, such as the preparation of carbon nanotubes or oxide rods. Copyright © 2010 John Wiley & Sons, Ltd.