Towards unique shear thinning behaviors under electric and magnetic fields achieved by TiO2 decorated magnetic MoS2 nanosheets: lubricating effects

Abstract

Discovering the relationship of structure and rheological behaviors remains challenging. In this study, the TiO₂ nanoparticle decorated magnetic MoS₂ nanosheets (Fe₃O₄@MoS₂@TiO₂ nanoparticles) exhibited unique rheological behaviors under external electric and magnetic fields owing to their special hierarchical structures. The constructed core–shell structures of the Fe₃O₄@MoS₂@TiO₂ nanoparticles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic behaviors were studied using a vibrating sample magnetometer (VSM). The Fe₃O₄@MoS₂@TiO₂ nanoparticles exhibited both electrorheological (ER) and magnetorheological (MR) properties that result from the decoration of high dielectric TiO₂ nanoparticles on the MoS₂ shell and paramagnetic behavior of Fe₃O₄ nanoparticles in the core, respectively. The MoS₂ nanosheets act as superb lubricant at a high shear rate due to their weak interlayer van der Waals forces. The abrupt decrease of shear stress at a critical shear rate was observed under the external magnetic field and the proposed mechanism was also discussed. The unique rheological behaviors of the Fe₃O₄@MoS₂@TiO₂ nanoparticle based suspensions highlight the great promise of MoS₂-based materials for cornerstone applications in rheological fields.