Synthesis of Nanostructured Hydroxides and Oxides of Iron: Control Over Morphology and Physical Properties

This paper reports on the surfactant-assisted synthesis of nanotubes and nanorods of β-FeOOH and hence α-Fe₂O₃ (hematite) with remarkable stability against temperature under different reaction conditions. Characterization and a comprehensive study of their nanosized properties are carried out by powder X-ray diffraction, thermal analysis, transmission electron microscope, and vibrating sample magnetometer. Upon calcination at 300°C, β-FeOOH nanostructures transform to α-Fe₂O₃ with some change in morphology. The samples convert to layered rod-like structures and further into some sort of a disc resembling stacked structures upon heat treatment. Even for magnetic fields up to 10 000 G, the magnetization curves for the nanotubes/nanorods of hematite do not attain the saturation magnetization. All the materials exhibit a very low coercivity even at room temperature and hence are potential materials for magnetic applications.