Core-shell structured Fe3O4@SiO2 nanoparticles fabricated by sol–gel method and their magnetorheology

Using a sol–gel method, silica-coated magnetite (Fe3O4@SiO2) core-shell nanoparticles were fabricated following a two-step process. In the first step, the Fe3O4 nanoparticles were prepared via a solvothermal method. In the second step, the Fe3O4 nanoparticles were coated with SiO2 formed through the hydrolyzation of tetraethyl orthosilicate. The structure and properties of the core-shell Fe3O4@SiO2 nanoparticles were characterized and the results showed that Fe3O4@SiO2 nanoparticles are a soft magnetic material. A magnetorheological (MR) suspension was prepared based on the synthesized Fe3O4@SiO2 nanoparticles dispersed in silicone oil and measured using a rotational rheometer at various magnetic field strengths. Using a rotational rheometer, the MR properties of the Fe3O4@SiO2 in silicone oil, including shear stress, shear viscosity, and yield stress were examined under an applied magnetic field.