Effective permittivity of nanocomposites from 3D charge transport simulations

The effective permittivity and stored energy in nanocomposites incorporating dielectric and conducting nanofillers are computed by simulating bipolar charge injection, transport, attachment, and recombination through amorphous polymer using a self-consistent 3D particle-in-cell model with nanofillers treated as extensions to the classical electrical double layer. Effective permittivities computed using an energy conserving scheme is shown to have excellent agreement with the Lichtenecker, Bruggeman, and Maxwell-Garnett mixing rules especially at low volume fraction, low permittivity contrast, and small Clausius-Mossotti factor, and lie well within the Wiener bounds. The energy conserving scheme with Maxwell-Garnett E field interpolation combines the best of the Maxwell-Garnett and fundamental Lichtenecker rules and results in broad validity over the entire volume fraction range. Computed stored energies show monotonic increase with dielectric fillers and a peak at 25 vol % for conducting fillers, attributed to the competing effects of higher energy with increasing E field modification and lower energy with decreasing binder volume. (c) 2015 Wiley Periodicals, Inc.