Controllable synthesis, formation mechanism and magnetic properties of hierarchical α-Fe2O3 with various morphologies

In this paper, a simple and efficient route had been developed for morphology-controlled synthesis of hierarchical α-Fe2O3 superstructures assembled by nanocrystallites. All chemicals used were low-cost compounds and environmentally benign. The morphologies and structures of the α-Fe2O3 crystals were characterized by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Fourier-transform IR spectroscopy (FTIR). The results showed that different shapes of hierarchical α-Fe2O3 nanostructures such as peanuts-like, capsule-like, cantaloupe-like and almond-shaped could be prepared by simply varying the concentration of silicate anions and other inorganic reagents. The as-prepared α-Fe2O3 architectures were composed of nanorods or nanosheets at different synthesis temperature. The possible formation mechanism was described based on the experimental results. Magnetic hysteresis measurements revealed the as-prepared superstructures displayed ferromagnetic behavior with higher remanence and coercivity at room temperature, which was attributed to the superstructure or the shape anisotropy of the samples.

► Hematite nanostructures were prepared though template-free hydrothermal reaction.
► All chemicals used were low-cost compounds and environmentally benign.
► The shapes of hematite nanostructures could be well controlled.
► The building blocks of hematite were finely controlled by varying temperature.
► The as-prepared superstructures display higher remanent magnetization and coercivity.