Abstract:
The present article reports the governing influence of substituting the M
2+ site in nanoscale
MFe2O4 spinel ferrites by different magnetic metals (Fe/Mn/Co/Ni) on magnetorheological and
magneto-elastoviscous behaviors of the corresponding magnetorheological fluids (MRFs).
Different doped MFe2O4 nanoparticles have been synthesized using the polyol-assisted
hydrothermal method. Detailed steady and oscillatory shear rheology have been performed on
the MRFs to determine the magneto-viscoelastic responses The MRFs exhibit shear thinning
behavior and augmented yield characteristics under influence of magnetic field. The steady state
magnetoviscous behaviors are scaled against the governing Mason number and self-similar
response from all the MRFs have been noted. The MRFs conform to an extended Bingham
plastic model under field effect. Transient magnetoviscous responses show distinct hysteresis
behaviors when the MRFs are exposed to time varying magnetic fields. Oscillatory shear studies
using frequency and strain amplitude sweeps exhibit predominant solid like behaviors under field
environment. However, the relaxation behaviors and strain amplitude sweep tests of the MRFs
reveal that while the fluids show solid-like behaviors under field effect, they cannot be termed as
typical elastic fluids. Comparisons show that the MnFe2O4 MRFs have superior yield
performance among all. However, in case of dynamic and oscillatory systems, CoFe2O4 MRFs
show the best performance. The viscoelastic responses of the MRFs are noted to correspond to a
three element viscoelastic model. The study may find importance in design and development
strategies of nano-MRFs for different applications.
