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 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°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.