Combined high permittivity and high electrical conduc­tivity of carbon nano-onion/polyaniline composites

• A dielectric relaxation mechanism recorded by Broadband Dielectric Spectroscopy.
• The relaxation dynamics is studied from 15 K to room temperature.
• A microscopic model links the carbon nano-onions with huge dielectric constant.
• The multi-layered structure of carbon nano-onions is related with huge capacitance.

We report high dielectric permittivity values for electrically conducting carbon nano-onion/polyaniline (CNO/PANI) composites. Broadband Dielectric Spectroscopy (BDS) measurements conducted under isothermal conditions from 16 K to room temperature in the frequency range between 1 mHz and 1 MHz, revealed a Cole–Cole relaxation mechanism. The intensity of the relaxation is comparable with the observed huge static dielectric constant values, and indicates a correlation between the intense capacitance effects and the relaxation. The relaxation dynamics involve single or two phonon assisted tunneling of the relaxing electric charge carriers (protons and electrons) at low temperatures, which transition to multi-phonon assisted tunneling relaxation above 100 K. Within the Mott–Davis model describing phonon-assisted tunneling relaxation in disordered media, the typical spatial scale relaxation occurs and is found to correlate with the size of the CNOs. The capacitance correlates with the large effective CNO surface areas.

We report high dielectric permittivity values for electrically conducting carbon nano-onion/polyaniline (CNO/PANI) composites. Broadband Dielectric Spectroscopy (BDS) isothermal measurements detected a relaxation mechanism of intensity which is comparable to the observed huge static dielectric constant. Correlation between the intense capacitance effects and the relaxation are interpreted along within the Mott–Davis model describing phonon-assisted tunneling relaxation in disordered media. It was found that the typical spatial scale relaxation occurs and is found correlate with the size of the CNOs. The capacitance correlates with the large effective CNO surface areas. Pani/CNO composites prove to be a promising electrode material for ultracapacitors.Figure optionsDownload as PowerPoint slide