α-Fe–Al2O3 nanocomposites prepared by sol–gel method

Using a sol–gel process, the fabrication of pure α-Fe–Al2O3 nanocomposites from aluminum isopropoxide precursors and ferric nitrate nonahydrate is described and analyzed. The hydrolysis reaction, polymerization reaction and reduction treatment in hydrogen atmosphere are discussed. In the present sol–gel process, the solution temperature and its pH value are strictly controlled in order to get clear sols and transparent gels, i.e. to avoid the hydrolysis precipitation. Excellent composite homogeneity and dispersion are achieved. The structural and magnetic properties of the obtained nanocomposites are characterized by employing X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). FeAl2O4 was observed as an intermediate phase between α-Fe2O3 and α-Fe, occurring during the reduction treatment. As can be seen during annealing in an oxidizing atmosphere at 300 °C, the processed α-Fe–Al2O3 nanocomposites are resistant to oxidation.