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 physical property of magnetorheological fluids. Typically, researchers use hollow or coated magnetizable particles to reduce the density difference between the particles and the carrier liquids, thereby improving the anti-sedimentation performance of magnetorheological fluids. However, the treated particles lose their own 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 formulas of relative shear resistance and relative settlement velocity of particles under the two structures were established based on the two-particle configuration and single-particle system, respectively, and the mechanical properties and anti-settlement performance of the two structural particles were compared and analyzed. The calculation results show that there is a scale range, and when the hollowness and coating thickness of the particles are within this range, the particles with hollow structure not only exhibits better anti-sedimentation but also has less loss of yield stress. In other words, in this dominant scale range, the hollow structure is superior to the core-shell structure. In addition, the relative settlement velocities of the two structural particles were also investigated at different particle densities and carrier liquids densities.