Nanocomposites of Fe₃O₄ nanoparticles decorated on WS₂ nanosheets with controlled magnetorheological properties and enhanced sedimentation stability

Achieving a balance between high yield stress and superb sedimentation stability remains a great challenge for magnetorheological (MR) fluids. Developing nanocomposites by integrating magnetic particles with low-dimensional nanomaterials is an effective strategy to address this issue. In this study, Fe₃O₄/WS₂ nanocomposites were designed and synthesized involving the hydrothermal growth of Fe₃O₄ nanoparticles onto the exfoliated WS₂ nanosheets. A detailed characterization was conducted using a range of analytical tools such as SEM, XRD, Raman, XPS and VSM to confirm the successful construction of Fe₃O₄/WS₂ nanocomposites. The MR fluid was subsequently prepared by dispersing the resulting Fe₃O₄/WS₂ nanocomposites into silicone oil. The MR properties were measured under different magnetic field intensities in both steady shear and oscillatory shear modes. The rheological parameters including shear viscosity, shear stress, storage modulus and loss modulus demonstrated a strong dependence on the applied magnetic field intensity. The mechanism involved the formation of more extensive and robust field-induced chain-like structures with increasing field strength. Finally, the sedimentation stability was quantitatively monitored over time and it was revealed the Fe₃O₄/WS₂-based MR fluid exhibited possessed significantly improved sedimentation stability relative to the conventional carbonyl iron particles.