An investigation of thermal decomposition of β-FeOOH nanowire arrays assembled in AAO templates

beta-FeOOH nanowire arrays were assembled into porous anodized aluminum oxide (AAO) templates by electrochemical deposition in the mixture solution of FeCl3 and (NH4)(2)C2O4. In order to obtain well-crystallized alpha-Fe2O3 and other iron oxides nanowires, beta-FeOOH nanowire arrays with amorphous crystal structure were heat-treated at different temperatures from 200 to 600 degrees C. The decomposition products were characterized by DTA, XRD, FTIR, and Mossbauer spectroscopy. When heat-treated at 200 degrees C, only 65% of beta-FeOOH decomposed, whereas, when the temperature was up to 300 degrees C, it was completely decomposed and formed poorly crystallized beta-Fe2O3. This transition temperature is higher than the 200 degrees C obtained on other beta-FeOOH materials. However, when heated above 300 degrees C, the main products are characterized as poorly well-crystallized alpha-Fe2O3 nanowires, whereas, well-crystallized arrays can be formed when the temperature was up to 600 degrees C, and this temperature is also higher compared with those temperatures observed on other beta-FeOOH materials. From Mossbauer results, the alpha-Fe2O3 nanowires were composed of fine particles in which 66% of the particles are superparamagnetic. (c) 2006 Elsevier B.V. All rights reserved.