Preparation And Transport Phenomena Of Manganese-Zinc Ferrite Nanoparticles

As an important magnetic material, manganese-zinc ferrite, due to the great application and long-term basic research, has been widely used in the various areas such as transformers, coil cores, magnetic heads and so on. In recent years, the interests in Mn-Zn ferrite nanoparticles are growing based on their potential applications in magnetic fluid hyperthermia and magnetorheological fluid because of its soft magnetic property, high stability and other characteristics.The preparation, characterization and application of Mn-Zn ferrites are investigated. Details are as follows:1. The Mn-Zn ferrite nanoparticles were prepared by chemical co-precipitation using FeC13·6H2O, MnSO4·H2O and ZnSO4·7H2O as the starting materials. During the co-precipitation, the effects of the ratio of Mn2+ and Zn2+ concentration on the magnetic properties were considered. To prevent the aggregation of nanoparticles, oleic acid was used as surfactant. The obtained nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and thermogravimetry (TG). The aggregate size was significantly reduced after modification, leading to the high dispersibility of nanoparticles in thermoplastic vulcanizate (TPV). Compared with the bare nanoparticles, the modified nanoparticles are proved to improve the tensile strength and elongation of TPV.2. The Mn0.8Zn0.2Fe2O4 magnetic nanoparticles were synthesized by co-precipitation; A and B were used as the surface modifier, respectively. Mn0.8Zn0.2Fe2O4 magnetic nanoparticles modified with bilayer surfactants were also prepared by co-precipitation. The results demonstrated that the nanoparticles modified by A had an average size of 80 nm and the saturation magnetization reached 41emu/g. Octahedral shaped Mn0.8Zn0.2Fe2O4 ferrites were synthesized using B as the surfactant and the evolution of these octahedra was examined by SEM and the mechanism was briefly discussed. VSM measurements revealed that the saturation magnetization was about 51emu/g at room temperature. Moreover, those different shaped Mn0.8Zn0.2Fe2O4 ferrites could be used to prepare magnetic fluid, which had potential applications in hyperthermia. The in-vitro heating experiments were performed, and the effect of Mn0.8Zn0.2Fe2O4 concentration and magnetic field intensity on heating effect was also investigated. The bilayer-modified nanoparticles had an average size of 15 nm, which could be used for fluid preparation. The magnetic fluid demonstrated fast magneto-temperature response, which had the potential application in both magnetic resonance imaging and magnetic fluid hyperthermia.3. Nanometer Mn-Zn ferrites have many unique characteristics which can enhance the anti-reunite ability, the anti-settling ability and the mechanics capability of the aqueous magnetorheological fluids. By changing the dosage of magnetic nanoparticles and coupling agent, the properties of the fluids have been systematically investigated, which includes sedimental stability, viscosity and magnetorheology properties.