Effect of the interface between magnetic particles and carrier liquids on magnetorheological properties and sedimentation of magnetorheological fluids: A molecular dynamics simulation and experimental insights

Abstract

Theoretically, solid-liquid interactions play an important role in the rheological properties of magnetorheological (MR) fluids. In this study, interface molecular models of silicone oil (SO) and ionic liquid (IL)-based MR fluids are established. Based on the two kinds of interface models, molecular dynamics (MD) simulations directly revealed the adsorption behavior and the interaction between magnetic particle surfaces and SO or IL molecules. The main factor for the difference in the magnetorheological properties and sedimentation stability between the two MR fluids is revealed at the atomic scale, combining experimental results. The simulation results confirm that the nonbond attraction, wettability, and interface stability of the Fe/IL interface structure are higher than those of the Fe/SO structure. Moreover, compared to SO molecules, the evolution of the interface microstructure shows that IL molecules are more easily adsorbed on the surface of magnetic particles, resulting in the sedimentation stability of the IL MR fluid being reduced in 100 h. Meanwhile, the rheological properties are enhanced because of the stronger interface binding of Fe/ILs. Therefore, the interface strength between two phases and the aggregation of carrier liquid molecules on the surface of magnetic particles have a great influence on the magnetorheological properties and sedimentation stability of MR fluids.