Dielectric response, functionality and energy storage in epoxy nanocomposites: Barium titanate vs exfoliated graphite nanoplatelets

Barium titanate/epoxy and exfoliated graphite nanoplatelets/epoxy nanocomposites were prepared and studied varying the filler content. Morphological characteristics were examined via scanning electron microscopy, while structural changes occurring in barium titanate as a function of temperature were investigated by means of X-ray diffraction. Broadband dielectric spectroscopy was employed for determining the dielectric response of the prepared systems. Based on the conducted analysis it was found that three relaxation processes are present in the spectra of the examined materials. From the slower to the faster one, these are interfacial polarization, glass to rubber transition of the polymer matrix, and rearrangement of polar side groups of the polymer chain. Systems' functionality and energy storing efficiency were assessed in terms of dielectric reinforcing function. Finally, the energy density of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites.

Systems' functionality, electrical relaxations and energy storing efficiency were assessed in terms of dielectric permittivity, electric modulus and dielectric reinforcing function (G). Further, the energy density (U) of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites.Figure optionsDownload as PowerPoint slideHighlights
► Relaxation phenomena were found to be present in all studied systems.
► Two processes emanate from the polymer matrix (α-mode and β-mode).
► Systems' electrical heterogeneity gives rise to interfacial polarization.
► BaTiO3/epoxy composites exhibit functional behavior due to structural changes.
► xGnP/epoxy composites exhibit increased energy storing efficiency.