Fe₃O₄/sepiolite magnetic composite particles and their magneto- responsive characteristics

To prepare a new magnetorheological (MR) material of magnetite/clay composite-based MR material and test its rheological characteristics, Fe₃O₄/sepiolite clay nanocomposite particles were fabricated by loading Fe₃O₄ particles on the surface of sepiolite using an in situ chemical co-precipitation method, and their MR characteristics under applied magnetic fields were examined. Scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction confirmed successful composite formation. Vibrating sample magnetometry also revealed their typical superparamagnetic behavior. The synthesized composites were dispersed in mineral oil to form a MR fluid with a particle concentration of 10 vol%. Various magneto-rheological tests of the MR fluids were attempted at different magnetic field strengths, including flow curve and dynamic oscillation test. While shear viscosity, yield stress, and dynamic modulus increased with magnetic field strengths, the yield stress as a function of magnetic field strength demonstrated a slope of 1.0 on a log–log scale.