Wave absorbing properties of polymer-carbon nanocomposites in the THz region

We have investigated the absorption characteristics of several kinds of polymer/carbon nanocomposites in the THz region. In the calculation of the absorption, we treated each composite as a dielectric lossy layer in a conductor-backed single-layered electromagnetic wave absorber. To measure the complex permittivity of the composites, we used THz transmission time-domain spectroscopy. A composite of vapor-grown carbon fibers (VGCF, registered trade mark, product of Showa Denko K.K.) dispersed into a polymer matrix exhibited good absorbing performance over the wide frequency range. The complex permittivity of the VGCF composite varied along the non reflection curve as the frequency changed. This means that the peak absorption frequency can be controlled simply by adjusting the layer thickness.