Activation Energy and Dielectric Properties of Epoxy Nanocomposites with Carbon Nanotubes and Carbon Black

This study presents a comparative analysis of multiwall carbon nanotube–epoxy (MWCNT–EP) and carbon black–epoxy (CB–EP) nanocomposites to evaluate the influence of filler concentration and frequency on activation energy and dielectric properties. Activation energy was obtained from the slopes of Arrhenius plots (ln sigma vs. 1/T) at 0.5, 5, and 10 kHz. Both composites showed higher activation energy at 0.5 kHz due to long-range charge-carrier hopping, whereas higher frequencies promoted localized transport between adjacent defect sites. Increasing filler concentration further reduced activation energy, reflecting saturation of dangling bonds, lower density of states, and reduced domain boundary potential. Dielectric analysis revealed that CB–EP composites consistently possessed higher dielectric constants than MWCNT–EP composites at equivalent filler loadings, owing to CB's smaller particle size and greater surface area. For both composites, the dielectric constant decreased with increasing frequency, consistent with interfacial polarization effects. These findings clarify how carbonaceous fillers influence the electrical and dielectric behavior of epoxy nanocomposites.