Improved properties of bidispersed magnetorheological fluids

We have investigated the influence of nanosized particle concentration on rheological properties when mixed with a magnetorheological (MR) fluid. We have also studied the structural, morphological and magnetic properties of ferrofluid-based MR fluids (F-MRFs). Field-induced rheological and viscoelastic properties of F-MRFs with varying shear rate and strain amplitude have been investigated. The Herschel-Bulkley model was found to fit well with the flow behaviour of F-MRFs. In the oscillatory strain sweep test, F-MRFs show linear viscoelasticity at low strain and the storage modulus (G′) is higher than the viscous modulus (G′′), which indicates the existence of strong links among the particles that form the microscopic structures. The storage modulus increases with increasing weight fraction of nanosized particles. Furthermore, the loss factor (ratio of G′′ and G′) was also investigated as a function of magnetic field strength. In addition, time-dependent relaxation behaviour of magnetically induced chain-like structures has also been described. The study reveals that the addition of nanoparticles to MR fluids increases the viscosity as well as the fluid stability under a magnetic field.