Temperature effect on the magneto-rheological behavior of magnetite particles dispersed in an ionic liquid

The magneto-rheological properties of iron(II, III) oxide particles dispersed in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate were investigated in the temperature range from 25 °C to 76 °C. The experimental results have revealed that the apparent viscosity of the dispersion slightly changes with the temperature when a constant magnetic field is applied and its value mainly depends on the shear rate and the strength of the magnetic field. The viscosity of the dispersion remains practically unmodified with both the temperature and the magnetic field intensity as the magnetic saturation of the material is reached; in this regime the viscosity will only depend on the applied shear rate. In contrast, the yield stress values of the dispersion as well as the corresponding shear stress vs. shear rate curves have shown and inversely proportional behavior with temperature for a constant magnetic field. Moreover, a power law model was utilized to predict the temperature dependence of the yield stress under the presence of a constant magnetic field.