A magnetorheological study of an uncoated nanoparticle-dispersed magnetic ionic liquid

Magnetic ionic liquids (MILs) are a new class of materials that embody intrinsic paramagnetic properties due to the presence of transition metals. They have rudimentary characteristics like high ionic conductivity, extreme thermal stability, and unique magnetic response. The present research deals with a solution of an imidazolium-based MIL, 1-butyl-3-methylimidazolium tetrachloroferrate, and uncoated iron oxide nanoparticles. First, the homogeneous dispersion of these nanoparticles in the MIL has been investigated, followed by the characterization of the magneto-rheological shear rate vs. shear stress hysteresis without and with an applied magnetic field. Even in the absence of any steric repulsion among them, these uncoated particles are found to distribute uniformly in the solution. The magnetorheological properties of this solution have been explored by stress-strain analysis and by quantifying the viscoelastic response to an oscillatory shear. It shows a shear thinning behaviour, which diminishes systematically with the applied field. Under an applied magnetic field, the viscosity increases to a saturation value beyond which it remains unaltered. The relaxation time of the fluid drops down considerably due to the applied field, indicating a transformation from viscous to elastic nature. These observations may help in easy synthesis and widening the applications of magnetofluids in various biomedical and engineering fields.