Carbon nanotube composites with high dielectric constant at low percolation threshold

TLDR

The large aspect ratio and high conductivity of MWNTs can cause a low percolation threshold in MWNT/PVDF composites. This study investigates the dielectric properties of untreated MWNT/PVDF composites. The dielectric constant of MWNT/PVDF composites reaches about 300 at low frequencies with only 2.0 vol % MWNT, while the percolation threshold is 1.61 vol % and dielectric loss stays below 0.4, demonstrating substantial dielectric enhancement without chemical functionalization.

Abstract

In this letter, the dielectric properties of the untreated multiwall carbon-nanotubes∕poly(vinylidene fluoride) (MWNT∕PVDF) composites are studied. Towards low frequencies, the dielectric constant of a composite with about 2.0vol% of MWNT increases rapidly and the value of the dielectric constant is as high as 300. However, by a calculation, the percolation threshold of the MWNT∕PVDF composites is only 1.61vol% (0.0161 volume fraction) of MWNT. Both the large aspect ratio and the high conductivity of the MWNT may lead to the low percolation threshold of the MWNT∕PVDF composites. For the percolation composite, the dielectric loss value is always less than 0.4, irrespective of the frequency. Therefore, the experimental results suggest that the dielectric properties of MWNT∕PVDF composites may be improved significantly without the chemical functionalization to carbon nanotubes.