Physical aging in a soft-glassy electrorheological fluid

In this work, we have rheologically investigated how the electric field intensity and temperature influence the physical aging dynamics in a soft-glassy electrorheological (ER) fluid. Our ER fluid is a dispersion of silylated carbon nanofibers (SiCNF, 4 wt. %) in silicone oil, which exhibits physical aging as well as demonstrates the ER effect. We have captured the waiting time-dependent relaxation modulus decay under parametric variations of the electric field and temperature. These curves have been transformed in the effective-time domain to obtain the time-waiting time master curves along with the corresponding aging exponent (μ) values as a measure of the rate of the aging process. In the study window, it was observed that a rise in the magnitude of either electric field or temperature accelerates the aging process, driving the system more rapidly toward a lower free energy state (greater degree of structural arrest). We believe that fundamentally, these two stimuli alter the reorganization process of constituent particles/molecules. Our findings provide new insight into how these external stimuli can be employed to regulate the aging phenomenon.