Template-free synthesis of monodispersed octahedron Fe3O4 particles

Monodispersed octahedron Fe3O4 particles have been directly synthesised on a large-area iron substrate using a template-free hydrothermal route. X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer were used for the structural, morphological and magnetic characterisation of the products, respectively. The influence of the concentration of NaOH solution on the size and shapes of the as-prepared Fe3O4 samples has been studied. It was found that an increase in the concentration of NaOH solution resulted in a decrease in the average size of Fe3O4 particles. The average diameter of the particles reduces from 20 to 0.5 mu m by simply changing the concentration of NaOH solution from 0.5 to 2 M. The octahedron Fe3O4 particles obtained in 2.0 M NaOH at 150 degrees C for 12 h show a high-saturation magnetisation of ca. 165.3 emu/g, a remnant magnetisation of ca. 8.5 emu/g and a coercivity of ca. 87.7 Oe at room temperature. The formation mechanism of octahedron Fe3O4 particles is also discussed.