Deterministic role of frequency, amplitude and concentration regimes on the complex dielectric relaxation of colloidal complex fluids

Abstract

The present article explores the governing roles played by concentration regimes, frequency and amplitude of the forcing electric field on the dynamic dielectric responses of nanocolloidal non-polar suspensions. Frequency dependent complex dielectric constants were determined in the band of 1 to 107 Hz at constant temperature via dielectric spectroscopy. In addition to prevalant literature measurements, influence of field amplitude has also been performed to investigate the role of electric field intensity upon the relaxation behaviors. The experimental observations reveal that variation of frequency, as well as choice of particle material significantly influences the dielectric responses of nanocolloids. Further, the amplitude of field is found to induce differences in the dielectric response. It is also observed that the relaxation responses are grossly different for concentrated dispersions than the dilute counterparts. The concentration regimes are observed to bring about overlapping relaxation responses in the colloids. Good degree of quantitative agreement has been found between the experimental observations and the generic Havriliak-Negami relaxation model. It has been shown that for a given nanomaterial, reduction of relaxation timescale is a direct consequence of enhancement in concentration and the colloids transit from predominantly storage to leaky systems with concentration regimes. Additionally, the reported volume diffusion mechanism (VDM) is found to be in compliance with the experimental findings. The occurrence and shift of peaks and valleys in the dielectric spectra has been explained based on dielectric response theories for electrically heterogeneous media.