Studies On Preparation And Property Of Fe₃O₄ Magnetic Fluid

Magnetic fluid which has magnetism and fluidity is a new-style liquid function material, and it has wide application in many fields. Magnetic fluid can be divided into three types which are ferrite type, metals type and iron nitride type. Because the techniques and the equipments of producing ferrite type and metals type magnetic fluid are very complicated and the antioxidation ability of the product is ecumenical weak, so most of the magnetic fluid products are Fe₃O₄ magnetic fluid in actual production and application.This paper prepared Fe₃O₄ magnetic fluid with kerosene as a base liquid through "dry method" and "wet method" which are based on the chemical coprecipitation, and discuss the influence of the preparation techniques to the stability of the Fe₃O₄ magnetic fluid. Analyze the crystal structure of the Fe₃O₄ particles with the XRD, and test the magnetism ability of the Fe₃O₄ powder with the VSM. Observe the microstructure of the magnetic fluid samples with the Transmission Electron Microscope, also test and figure the capabilities of these samples such as stability, magnetism, viscosity in and out of horizontal magnetic field. The result shows that the Fe₃O₄ particles synthesized by chemical coprecipitation method has no impurity face and is the anti-spinel structured compounds (of general formula AB₂O₄). The Ms of the Fe₃O₄ powder is about 60emu/g, and the powder shows well soft magnetic ability with low Mr and Hc. The picture of the TEM shows that the volume ratio of oleic acid and Fe₃O₄ is important to the stability of magnetic fluid. Big ratio leads to well dispersal of the magnetic particles. All samples have different subside condition. But the samples synthesized by "wet method" have better stability than that synthesized by "dry method". Both WA and WB samples have good superparamagnetism, and the magnetism mainly relates to the concentration of the samples. Generally speaking, the magnetism rises with the volume ratio enlarging. The WA samples match the characteristic of the plastic fluid, and the D samples also match the characteristic of the plastic fluid except D2. In the horizontal magnetic field, the viscosity of WA and WB samples enlarges with magnetic field rising. It is showed that n dependents with H as power function approximately except WB3.