Permittivity of dielectric composite materials comprising graphene nanoribbons. The effect of nanostructure.

New lightweight, flexible dielectric composite materials were fabricated by the incorporation of several new carbon nanostructures into a dielectric host matrix. Both the permittivity and loss tangent values of the resulting composites were widely altered by varying the type and content of the conductive filler. The dielectric constant was tuned from moderate to very high values, while the corresponding loss tangent changed from ultralow to extremely high. The data exemplify that nanoscale changes in the structure of the conductive filler result in dramatic changes in the dielectric properties of composites. A microcapacitor model most explains the behavior of the dielectric composites.

Low-loss, high-permittivity composites made from graphene nanoribbons.

A new composite material was prepared by incorporation of graphene nanoribbons into a dielectric host matrix. The composite possesses remarkably low loss at reasonably high permittivity values. By varying the content of the conductive filler, one can tune the loss and permittivity to desirable values over a wide range. The obtained data exemplifies how nanoscopic changes in the structure of conductive filler can affect macroscopic properties of composite material.

Transient reflection of TM-polarized plane waves from a Lorentz-medium half-space.

The time-domain reflection coefficient for a TM-polarized plane wave obliquely incident on a Lorentz-medium half-space is determined analytically by inversion of the frequency-domain reflection coefficient. The resulting expression contains only the convolution of simple functions. This allows the temporal behavior of the reflection coefficient to be predicted, and the relationship between the material parameters and the oscillation of the response to be easily identified. The time-domain expression is validated numerically through comparison with the inverse fast Fourier transform of the frequency-domain reflection coefficient.

Transient reflection of TE-polarized plane waves from a Lorentz-medium half-space.

The time-domain reflection coefficient for a plane wave obliquely incident on a Lorentz-medium half-space is determined analytically by inversion of the frequency-domain reflection coefficient. The resulting expression contains only simple functions and a single convolution of these functions. Owing to its simplicity, this form of the reflection coefficient provides insight into its temporal behavior, specifically how the relationship between the damping coefficient and the oscillation frequency determines the shape of the response. The simple form of the reflection coefficient is validated numerically through comparison with the inverse fast Fourier transform of the frequency-domain reflection coefficient.