Preparation And Characterization Of Silicon Oil Based Ferro Fluid Of CoFe₂O₄ Nano-magnetic Particles

Silicon oil based magnetic fluid whose carrier is silicon oil has the advantanges of high temperature resistance,low viscosity,low vapor pressure and small viscosity change with temperature.And it can be applied to space,military and other fields.But the saturation magnetization which restrict its applications is too low,so this paper mainly improve the saturation magnetization of silicon oil based magnetic fluid by doping other elements.Firstly,the nano-magnetic particles of CoFe₂O₄ were prepared by the chemical precipitation.The optimal processing technology were determined:The molar ratio of Co2+,Fe2+ and Fe3+were 1:1:2;The best temperature and PH were 50? and 10,respectively.The rotational speed is 300rad/min.And the particles were synthesized by X-ray diffraction?XRD?,Transmission electron microscopy?TEM?and Vibrating sample magnetometer?VSM?,respectively.The results show that the particles were nano-magnetic particles of CoFe₂O₄ with a mean size of 10.7nrm,and the saturation magnetization of 53emu/g.The heating method was adopted to analyze the stability of CoFe₂O₄ nano-magnetic particles,and the result shows that the magnetic stability and chemical stability of nano-magnetic particles is improved by doping Co element.Then the nano-magnetic particles of CoFe₂O₄ were coated by silane coupling agent?A1120?in the carrier of absolute ethyl alcohol and the concentrated sulfuric acid oil of vitriol was used as the catalyst.The optimal processing technology were determined:The best temperature is 50?,the PH is 5 and the rotational speed is 400rad/min.And the coated particles were characterized by TEM.The result shows that the particles were coated by A1120 with a mean size of 20nm and the thickness of coating layer was 4.3nm.Then by the method of ultrasonic dispersion and high-energy ball mill,the silicon oil based magnetic fluid was obtained.And the characterization were determined by VSM and magnetic rheometer,respectively.The results show that the silicon based ferrofluid is none-Newtonian fluid.The saturation magnetization is 14.4emu/g and the viscosity is 9.172×10^-2 Pa·s.