Role of fibrillation on the magnetorheological and viscoelastic effects in Fe, Ni, and Co nanocolloids

Abstract

Magnetic metallic nanoparticle (NP)-based colloidal systems have the ability to show highly augmented magnetorheological (MR) and magnetoviscoelastic responses under the influence of magnetic fields. Magnetic metal NPs, viz., iron (Fe), nickel (Ni), and cobalt (Co) have been employed to formulate oleo magnetic-nanocolloids. The magnetocolloids have been characterized for rheological behavior and have been observed to demonstrate superior magnetoviscous effects under magnetic field due to fibrillation by the particles. The magnitude of maximum dynamic yield stress and viscosity of Fe magnetocolloids attained is 18 kPa and 4 kPa.s, respectively, for 15 wt% particle concentration and at ∼1.2 T magnetic field intensity. Furthermore, Fe-based colloids are found to be the best candidate among the three types of metallic colloids in terms of high MR effect under magnetic field. The same has been observed for magnetoviscoelastic effects in terms of the enhanced linear viscoelastic range, thixotropy, and strain creep behavior. The experimental observations also show that formulated colloids have highly stable structure under magnetic field even at high shear loads and demonstrate reversible behavior when subjected to rise and decay of magnetic fields.