Mechanism of chain formation in nanofluid based MR fluids

Mechanism of structure formation in bidispersed colloids is important for its physical and optical properties. It is microscopically observed that the mechanism of chain formation in magnetic nanofluid based magnetorheological (MR) fluid is quite different from that in the conventional MR fluid. Under the application of magnetic field the magnetic nanoparticles are filled inside the structural microcavities formed due to the association of large magnetic particles, and some of the magnetic nanoparticles are attached at the end of the chains formed by the large particles. The dipolar energy of the large particles in a magnetic nanofluid matrix becomes effective magnetic permeability (μeff) times smaller than that of the neutral medium. Inclusion of magnetic nanoparticles (∼10 nm) with large magnetic particles (∼3–5 μm) restricts the aggregation of large particles, which causes the field induced phase separation in MR fluids. Hence, nanofluid based MR fluids are more stable than conventional MR fluids, which subsequently increase their application potentiality.

Research highlights
► In bidispersed magnetic colloids nanoparticles are attached at the end of the chains formed by the large particles.
► Inclusion of magnetic nanoparticles (∼10 nm) with large magnetic particles (∼3–5 m) restricts the aggregation of large particles.
► Nanofluid based MR fluids are more stable than conventional MR fluids.