Synthesis of Fe3O4 nanoparticles without inert gas protection used as precursors of magnetic fluids

Fe3O4 nanoparticles were hydrothermally synthesized under continuous microwave irradiation from FeCl3·6H2O and FeSO4·7H2O aqueous solutions, using NH4OH as precipitating reagent and N2H4·H2O as oxidation-resistant reagent. The results of X-ray powder diffraction (XRD), FT–IR spectroscopy and scanning electron microscopy (SEM) measurements showed that the synthesized magnetite (Fe3O4) nanoparticles had an average diameter of 10 nm. The magnetic properties of the Fe3O4 nanoparticles were measured using a vibrating sample magnetometer (VSM), indicating that the nanoparticles possessed high saturation magnetization at room temperature. The Fe3O4 nanoparticles were used to prepare magnetic fluids (MFs) based on water, and the properties of the MFs were characterized by a Gouy magnetic balance, a capillary rheometer and a rotating rheometer, respectively.