Synergy effects in the electrical conductivity behavior of onion‐like carbon and multiwalled carbon nanotubes composites

The dielectric/electric properties of polyurethane composites filled with carbon nanotubes (CNT), onion-like carbon (OLC), and mixed OLC/CNT are compared across a wide frequency range from hertz to terahertz. The dielectric/electric properties of composites filled with OLC are very attractive and can be improved by addition of small amounts of CNTs due to a strong synergism between the two carbon allotropes. Moreover, in composites with mixed OLC/CNT inclusions, the value of the percolation threshold is lower than the value predicted by the excluded-volume theory. In composites with mixed OLC/CNT inclusions, the dielectric permittivity and electrical conductivity increase due to a decrease in the average distance between nanocarbon clusters. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim