Preparation And Characterization Of Fe₃O₄@SiO₂ Silicon Oil Based Magnetic Fluid

Silicone-based magnetic fluid has a unique application in the aerospace field,especially in the field of damping and sealing,in terms of its excellent viscosity-temperature performance and excellent physical and chemical properties.In order to break the monopoly of foreign technology,to prepare silicone oil-based magnetic fluid with excellent performance,the subject carried out some meaningful exploration.The core-shell nano-magnetic particles Fe₃O₄@SiO2 were prepared by chemical coprecipitation method and hydrolysis method of ethyl orthosilicate and coated with silane coupling agent A1120.The magnetic particles were dispersed in silicone oil by the dispersion method of ultrasonic dispersion and high energy ball milling to prepare silicone oil based magnetic fluid.Using transmission electron microscopy,vibrating sample magnetometer,infrared spectroscopy,X-ray diffraction,energy spectrum analyzer,contact angle tester and other testing methods to analyse particle size,particle composition and surface element content,saturation magnetization,the wettability between magnetic particles coated and silicone oil of core-shell magnetic nanoparticles.Using MCR302,rotational rheometer,LC oscillator circuit,vibrating sample magnetometer to analyse rheological properties,stability,saturation magnetization of silicon oil based magnetic fluid prepared.Among them,both contact angle tester to test the wettability of particles and LC oscillator circuit to test stability of silicon oil based magnetic fluid are innovative characterization means.In the preparation of core-shell nano-magnetic particles Fe₃O₄@SiO2,this research designed orthogonal test analysis and optimized the experimental process steps mainly for addition sequence of reactants,precursor solution pH,coating temperature,the amount of coating agent and other factors;The optimum experimental conditions were as follows:FeCl₂?FeCl3 and precipitant were added firstly,then TEOS and related catalyst were added.The suitable pH of hydrolysis and polycondensation of tetraethyl orthosilicate in solution is 4?5 and 9?10,respectively.The optimum coating temperature is 50?;the optimum molar ratio of Fe₃O₄ to SiO2 is 25:9.The prepared core-shell nano-magnetic particles have a particle size of 15?20 nm,a high monodispersity,a saturation magnetization of 56.2733 emu/g,and a superparamagneti sm.The silicone oil-based magnetic fluid was prepared by two-step method and the influence of magnetic particle content on the performance of silicone oil-based magnetic fluid was analyzed emphatically.Combined with the knowledge of fluid mechanics the rheological properties of magnetic fluid were given a reasonable explanation in this paper.The results show that the higher the particle content,the higher the saturation magnetization of the magnetic fluid and the higher the viscosity.The silica-based magnetic fluid prepared in this paper has a saturation magnetization of 251.33Gs with superparamagnetism and excellent viscosity-temperature performance compared with other types of magnetic fluid.The silicone-based magnetic fluid belongs to Newtonian fluid without external magnetic field,it belongs to quasi-plastic Bingham body with external magnetic field.