The Preparation Of Machine Oil-based Magnetic Liquid And Thermal Magnetic Studies

Ni and Fe-Ni alloy coated with SiO2/SiC nanoparticles were prepared by direct-currentarc plasma in a mixture of (15%SiH4+15%CH4+10%H2+60%Ar) atmosphere and the totalpressure was2×104Pa, respectively. Composition, morphology, size, surface properties,oxidation resistance and magnetic of nanoparticles were investigated with TEM、XRD、XPS、VSM and other measurement technologies. Result shows that the preparation ofSiO2/SiC coated were spherical Ni nanoparticles, size in range from10nm to35nm and thesurface coating layer thickness in range from3nm to5nm. Saturation magnetization was25Am2/kg at room temperature. When the temperature was at200℃and300℃, thesaturation magnetization intensity decreased to12.4Am2/kg and8.5Am2/kg, respectively.Size of Fe-Ni alloy nanoparticles was in range from10nm to40nm and the surface coatinglayer thickness in range from2nm to3nm. The saturation magnetization was60Am2/kg atroom temperature. When the temperature was at200℃and300℃, the saturationmagnetization intensity decreased to58.5Am2/kg and53.2Am2/kg, respectively.In the process of production of machine oil-based magnetic liquid, Ni, Fe-Ni alloynanoparticles were selected as the magnetic particles, oleic acid as surfactant and machineoil as the base. The viscosity and magnetic of machine oil-based magnetic liquid werestudied by viscometer and VSM. Result shows the viscosity of magnetic liquid, which hasselected Ni coated with SiO2/SiC as magnetic particle, was in range from1.05×103mPa·S to9.86×103mPa·S at25℃. When temperature was at85℃, the viscosity was in range from0.06×103mPa·S to2.91×103mPa·S. At room temperature, the saturation magnetization is inrange from0.7Am2/kg to5.5Am2/kg. The saturation magnetization of machine oil-basedmagnetic liquid with12wt%Ni nanoparticles was2.2Am2/kg at200℃. The viscosity ofmachine oil-based magnetic liquid in Fe-Ni alloy coated with SiO2/SiC as the magneticparticle was in range from1.51×103mPa·S to5.21×103mPa·S at25℃. The viscosity was inrange from0.21×103mPa·S to0.69×103mPa·S at85℃. At room temperature, the saturationmagnetization was in range from2.1Am2/kg to5.6Am2/kg. The saturation magnetization ofmachine oil-based magnetic liquid with12wt%Fe-Ni alloy nanoparticles was5.5Am2/kg at200℃.Machine oil-based magnetic liquid viscosity increased with the content of nano particles increasing; decreased with temperature increasing, but was not completely linearrelationship.Saturation magnetization of machine oil-based magnetic liquid increased with thecontent of nanoparticles increasing, when the temperature is below200℃, the saturationmagnetization of machine oil-based magnetic liquid almost did not change with temperature.