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

The Fe3O4 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 oil-based 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.