α-Fe–Al 2O 3 nanocomposites prepared by sol–gel method

Abstract

Using a sol–gel process, the fabrication of pure α-Fe–Al 2O 3 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). FeAl 2O 4 was observed as an intermediate phase between α-Fe 2O 3 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–Al 2O 3 nanocomposites are resistant to oxidation.