Test Study On Preparation, Characterization And Viscosity Properties Of Fe₃O₄Silicon Oil Based Ferrofluids

Magnetic fluids, also called ferrofuids (FFs), are stable colloidal suspensions that consist of magnetic nanoparticles dispersed in base liquid such as water or oil. As new functional materials, FFs exhibit both liquid behavior and magnetic properties, so they have been widely investigated and used in the area of high and new-type technology such as electronic technology, aviation and spaceflight, information technology, engineering and chemical industry, and biology and medicine, etc.We prepared Fe3O4silicon oil-based magnetic fluids via co-precipitation method in this paper and discussed the preparation procedure on the influence of the magnetic fluids. The magnetic fluids were characterized by the X-ray diffractmeter (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and the vibrating specimen magnetometer (VSM). The viscosity properties of the magnetic fluids were investigated by a rotating viscometer and a torsional oscillation cup viscometer, respectively.When the molar ratio of Fe+and Fe+is1.65:1, the purity of the prepared Fe3O4nanoparticles is higher and the average grain size is smaller. When the usage of oleic acid added to the solution is0.7mol, the silicon oil-based magnetic fluids were obtained with higher dispersity. The XRD characterization indicates that the experimental data can be assigned to Fe3O4, and the sample can be indexed to the cubic spinel structure which is in agreement with the standard data. No obvious impurity peaks can be detected. The SEM results show that the magnetic particles are uniform and the TEM characterization demonstrate that the particles are spherical shape with better dispersity and less agglomeration. In addition, the prepared magnetic fluids have high saturation magnetization intensity with59.25emu/g. Zero remanence and zero coercivity can be observed which indicates that the particles are superparamagnetism.The viscosity experimental results show that the viscosity of the ferrofluids decreases with increasing temperature, and increases with increasing magnetic field intensity due to the existence of the magnetic particles. The hysteresis curve of the viscosity-magnetic field shows that the formation and destruction of chain-like or drop-like structures has obvious effect on the viscosity of the ferrofluids. When the field is relatively strong, the viscosity at the decreasing stage is higher than that at the increasing stage. In contrast, when the field is relatively weak, the viscosity at the decreasing stage is slightly lower than that at the increasing stage. In addition, the relation between viscosity of the FFs and time under the magnetic field shows that time is an effective factor in the evolution of the magnetically induced structures.