Ferromagnetic Fe 3 O 4 nanoparticles were synthesized and then self-assembled into microparticles via a solvothermal method,using FeCl 3 ·6H 2 O as the iron source,sodium oleate as the surfactant,and ethylene glycol as the reducing agent and solvent.The obtained Fe 3 O 4 microparticles were characterized by X-ray powder diffraction (XRD),X-ray photoelectron spectroscopy (XPS),Raman spectroscopy and vibrating sample magnetometer (VSM).The size and morphology of the particles were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM).The Fe 3 O 4 microparticles of nearly monodisperse diameters,controllable in the range of 120-400 nm,consist of assemblies of Fe 3 O 4 nanoparticles with a diameter of 22 nm.The effects of reaction time,amount of surfactant and NaAc on the products were discussed.Interestingly,by using the pre-synthesized Fe 3 O 4 microparticles as the growth substrates,spherical and smooth-looking Fe 3 O 4 microparticles with average diameter of 1 m were obtained.A plausible formation process was discussed.
