Contribution of the positional and orientational ordering in anisotropic particle-based MR fluids: static and dynamic rheological study

Flake shape-based MR fluids were prepared in a carrier with variable weight fraction of magnetite nanoparticles (0%, 1%, 2%, 3%, and 4%). The spherical shape particle-based MR fluid was purchased from LORD Corporation, USA, for comparison. The magneto-rheology of these fluids under dynamic conditions indicates the orientational ordering of flakes which increases due to the presence of nanoparticles, as it changes the sliding friction between the flakes. The presence of nanoparticles significantly reduces the elastic stress derived from storage modulus compared to that of pure MR fluid. The particle-matrix interaction can be analyzed from the cohesive energy density, E c (the energy required to break all internal structure) using the critical strain amplitude and the storage modulus in the linear regime. The behavior of E c is found to be dependent on the shape of the particles. These results are supported by thermal conductivity, sedimentation, and redispersion study.