Dielectric relaxation behaviors and dissipation characteristics of colloidal nanocarbon (graphene and CNTs) complex fluids

Abstract

The present article reports the dynamic complex dielectric responses of non-polar nanocolloids of graphene (G) and carbon nanotubes (CNTs). The frequency dependent complex relaxation behaviors of G and CNT colloids were determined in the range of 100 Hz to 3 × 105 Hz employing dielectric spectroscopy at a constant temperature. The governing roles of nanostructure concentration, conductivity, frequency, and amplitude variation of the forcing electric field on the dielectric response have been examined. The experimental observations reveal that the presence of G or CNT, as well as their concentrations, significantly governs the overall dielectric responses of the nanocolloids. The dilute and concentrated colloids display grossly distinguishable capacitive and dissipative behaviors, hinting at the major role of concentration regimes on the dielectric behavior of such colloids. In addition, the variation of electric field intensity results in altering the dielectric responses of the colloids, which points at the role of polarization of the nanomaterials on the overall dielectric relaxation. To model the complex dipolar interactions, the classical Havriliak-Negami model is employed and good agreement has been achieved against the experimental observations. It has been observed that increasing nanomaterial concentration and field amplitude has a dominant influence upon the relaxation parameters. Further, the effects of colloidal concentration on the AC and DC conductivity modes have also been analyzed. The conductivity response of the colloids has been explained by appealing to percolation theories. The present article may find strong implications toward the design and development of liquid dielectric based electrical and electronics systems.