Study On Preparation And Performance Of Turbine Oil-based Magnetic Liquid

In this paper, Fe-Co and Fe-Ni nanometer particles coated with SiO2 were prepared by use of direct-current arc plasma in a mixture of (55%Ar+25%H2+20%SiH4) atmosphere and the total pressure was 9x104Pa. The phase composition, morphology, size, surface properties, oxidation resistance and magnetic properties of Fe-Co and Fe-Ni nanometer particles coated with SiO2 have been characterized with XRD, TEM, XPS, IR, DSC-TG and VSM. Results show that Fe-Co and Fe-Ni nanometer particles coated with SiO2 are spherical. The size distribution of Fe-Co nanometer particles coated with SiO2 is 25-120nm and the thickness of SiO2 is 3-5 nm. Oxidation takes place at 220 ℃; oxidation rate is accelerated at higher than 300℃. Saturation magnetization of Fe-Co 10% nanometer particles coated with SiO2 at room temperature and 300 ℃ is 91-112Am2/kg and 25Am2/kg, respectively. The size distribution of Fe-Ni nanometer particles coated with SiO2 is 20-60nm and the thickness of SiO2 is 3-4nm. Oxidation hardly takes place at lower than 200 ℃, while oxidation takes place at higher than 200℃. Saturation magnetization of Fe-Ni78% nanometer particles coated with SiO2 at room temperature,200℃ and 300℃ is 58-70Am2/kg,54Am2/kg and 33 Am2/kg, respectively.Turbine oil-based magnetic liquid was prepared by selecting Fe-Co and Fe-Ni nanometer particles coated with SiO2 as magnetic particles, using the mixture of two methyl silicone and oleic acid as surface active agent, turbine oil as the base fluid. The viscosity and magnetic properties of turbine oil-based magnetic liquid have been investigated with VSM and viscometer. Results show that the viscosity of turbine oil-based magnetic liquid with Fe-Co45% nanometer particles coated with SiO2 as the magnetic particle (1wt%-7wt%) is 1.6×103mPa·S-5.9×103mPa·S at 25℃. The saturation magnetiza-tion of turbine oil-based magnetic liquid with Fe-Co30%nanometer particles coated with SiO2 as the magnetic particle(8wt%-12wt%) is 7.2Am2/kg-12.1 Am2/kg at 25℃. The viscosity of turbine oil-based magnetic liquid with Fe-Ni45% nanometer particles coated with SiO2 as the magnetic particle (2wt%-8wt%) is 2.3×103mPa·S-7.3×103mPa·S at 25℃ and 0.5×103-2.9×103mPa·S at 85 ℃. The saturation magnetization of turbine oil-based magnetic liquid with Fe-Ni45% nanometer particles coated with SiO2 as the magnetic particle (1wt%-12wt%) is 0.69Am2/kg-11.3 Am2/kg at 25 ℃. The saturation magnetization of turbine oil-based magnetic liquid with Fe-Ni45% nanometer particles coated with S1O2 as the magnetic particle (3.5wt%) is 2Am2/kg at 200℃ and almost no changes with temperature.