Influence of the Carrier Fluid Viscosity on the Rotational and Oscillatory Rheological Properties of Ferrofluids.

This work mainly presents a comprehensive experimental study on the magnetorheological behavior of ferrofluids with carrier fluids of different viscosities. Three lubrication oil based ferrofluids of different viscosities and similar saturation magnetization values were prepared and characterized. Static and dynamic rheological tests of the three ferrofluids were performed using an advanced rotational rheometer with a magnetic field generating module. According to the experimental results, the magneto viscous effect, yield stress and storage modulus increase with the viscosity of carrier fluid, indicating that the structures of ferrrofluids tend to be larger and more stable in a carrier fluid with larger viscosity. The emergence and growth of "crossover" region with the increase in carrier fluid viscosity was observed using the strain-rate frequency superposition method, which were explained according to the microscopic mechanism of magnetorheology. These findings contribute to a better understanding of the microscopic mechanism of magnetorheology and provide guidance for practical applications.