Preparation and characterization of high stability silicone-based colloidal magnetic fluids

The Fe 3 O 4 magnetic nanoparticles were prepared using a chemical co-precipitation and were coated with surface -active agents including silane coupling agents KH550 and KH792, carboxyl-functionalized silicone oil, and amine-functionalized silicone oil. In this study, the four types of magnetic nanoparticles coated with different surface -active agents were characterized using XRD, FTIR, TEM, VSM, etc. to determine the effects of different surface -active agents on the magnetic nanoparticles. Furthermore, four different types of silicone oilbased colloidal magnetic fluids were prepared, and their stability was analyzed using an LC oscillation circuit. The results show that the magnetic nanoparticles coated with carboxyl-functionalized silicone oil have an average particle size of about 12.4 nm and a saturation magnetization of 65.2 emu/g. They exhibit the strongest dispersion stability in the base fluid, and the prepared silicone oil-based colloidal magnetic fluids can remain stable under a magnetic field for up to 2 months without sedimentation. Moreover, they exhibit excellent viscosity-temperature performance, which enhances the practical application value of silicone oil-based colloidal magnetic fluids.