Study On Preparation And Properties Of Perfluorinated Oil-based Magnetic Liquids

In this paper,Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle were prepared by the type of VZD-400direct-current arc plasma which mix with 60%Ar+30%H2+10%SiH4 atmosphere.Under 8×104Pa pressure,Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle were prepared by evaporating of pure Ni and Fe-Ni alloys.By using fluorocarbon oil as based fluid,oleic acid and dodecyl benzene sulfonic acid sodium as surfactant,Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle as magnetic particles which prepared perfluorinated carbon oil-based magnetic fluid.The phase composition,size,morphology,surface properties and magnetic properties of Ni@SiO₂ and Fe-Ni@SiO₂ nanometer particles have been characterized by Transmission Electron Microscope（TEM）,X-Ray Diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,and vibrating sample magnetometer（VSM）.The magnetic properties of the perfluorinated oilbased magnetic liquids were studied by Vibrating Sample Magnetometer（VSM）.Viscosity and rheological properties were studied by viscometer.The results show that Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle are spherical.The size of Ni@SiO₂ nanoparticle distribution is 10-35 nm.The thickness of SiO₂ is 2-5nm.Ni@SiO₂ nanoparticle of magnetization intensity increases with the enhancement of the magnetic field.When magnetic field is up to 200 KA/m,magnetization reaches saturation,saturated magnetization is 25 Am2 / kg.The size of Fe-Ni@SiO₂ nanometer particles distribution is 20-60 nm.The thickness of SiO₂ is 3-4nm.Saturation magnetization of Fe-Ni@SiO₂ nanometer particle at room temperature is 60-70Am2/kg.When temperature exceed 200℃,the saturation magnetization is decreased rapidly.As oil-based magnetic fluids,along with the nanoparticle concentration increasing,the viscosity of Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle are increased.In the meantime,the viscosity of these two types of fluid will be decreased when the temperature is increased.As oil-based magnetic fluids,along with the nanoparticle concentration increasing,the saturation magnetization intensity of Ni@SiO₂ and Fe-Ni@SiO₂ nanoparticle are increased.The relationship between saturation magnetization intensity and nanoparticle concentration are not strictly linear.The viscosity of perfluorinated oil-based magnetic fluid with Ni@SiO₂ nanoparticle（5wt%-50wt%）at normal temperature,the range of viscosity is between 1.47×10³mPa·S and 1.96×10³mPa·S,the range of saturation magnetization intensity is between 0.41Am2/kg and 4.5Am2/kg.Concentration of Fe-Ni@SiO₂ nanometer particles（10wt%-45wt%）,the range of viscosity is between 1.92×10³mpa·S and 2.53×10³mPa·S at 25℃,the range of viscosity is between 1.33×10³m Pa·S and 1.66×10³mPa·S at 85℃,the range of saturation magnetization intensity is between 0.45Am2/kg and 9.2Am2/kg.As oil-based magnetic fluids,along with the increase of shear stress increasing,the viscosity is decreased.Until the stress of shear is up to a certain degree,its viscosity keeps stability.For example,the concentration 5wt% of Ni@SiO₂ nanoparticle,when the stress of shear is up to 272017 mPa,its viscosity keeps stabilise in 1307 m Pa·S.