Reduction behaviour of Fe3+/Al2O3 obtained from the mixed oxalate precursor and the formation of the Fe0–Al2O3 metal–ceramic composite

Abstract

Reduction behaviour of Fe3+/A1,0, obtained by the decomposition of the oxalate precursor has been investigated by employing X-ray diffraction (XRD), Mossbauer spectroscopy and electron paramagnetic resonance (EPR)spectroscopy. Calcination of Fe3+/Al,0, at or below 1070 K yields mainly a poorly ordered, fine particulate form of ~-AI,-,Fe,O,. Calcination at or above 1220 K yields a-AI,-,Fe,O,. Reduction of Fe3+/AI,0, samples calcined at or below 1070 K gives the FeAI,O, spinel on reduction at 870 K; samples calcined at or above 1220 K give AI,-,Fe,O, with a very small proportion of metallic iron. Fe3+/A1,0, samples calcined at 1220 K or above yield metallic iron and a very small proportion of the spinel on reduction below 1270 K. In the samples reduced at or above 1270 K, the main product is metallic iron in both ferromagnetic and superparamagnetic forms. The oxalate precursor route yields more metallic iron than the sol-gel route.