Study on the Effect of Structural Scale of Hollow Particles and Core-Shell Particles on the Properties of Magnetorheological Fluids

Sedimentation resistance is undoubtedly the most relevant rheological property of magnetorheological fluids. Typically, researchers use hollowing or coating of magnetic particles to reduce the density difference between the particles and the carrier liquids, thereby improving the anti-sedimentation properties of magnetorheological fluids. However, the treated particles lose their magnetic properties, which in turn reduces the yield stress of magnetorheological fluids. In order to study the effects of coating thickness and hollow radius on yield stress and settlement velocity, the expressions of relative shear stress and relative settlement velocity of particles under the two structures were established based on the two-particle configuration, and the mechanical properties and anti-settlement properties of the two particle structures were compared. It is found that there is a scale range, and when the hollowness and coating thickness of the particles are within this range, the hollow structure not only exhibits better anti-sedimentation but also has less loss of yield stress. In other words, within this scale range, hollow structures are better than coating structures. This research has a theoretical guide for the preparation of high-performance magnetorheological fluids.