Negative permittivity enhanced reflection and adsorption of electromagnetic waves from carbon fiber felt/carbon nanotubes

Abstract

In order to meet the requirements of various application scenarios, it is necessary to study the electromagnetic interference (EMI) shielding properties and electrothermal properties of negative permittivity materials. Carbon fiber felt (CFF)/carbon nanotube (CNT) composites were prepared in this work using a simple impregnation method. The permittivity modulation of the composites was achieved by controlling the CNT content. Weakly negative permittivity (between −3 and −78) was observed throughout the X-band when the CNT content was 66 wt%, which was attributed to plasma oscillations. Meanwhile, the CFF/CNTs with negative permittivity exhibited an excellent EMI shielding performance of 57 dB, which was better than the reported metamaterials. In addition, we deeply investigated the synergistic effect of negative permittivity and EMI shielding performance. Due to the strong impedance mismatch caused by the negative permittivity, the surface of the metacomposite reflected most electromagnetic waves. In addition, plasma oscillations and the construction of conductive networks of CNTs gave the metacomposites a strong ability to attenuate the electromagnetic waves inside the material, resulting from the high conductivity and polarization loss. Furthermore, the CFF/CNTs also exhibited excellent electrical–thermal conversion and outstanding cycling stability, showing potential applications in extreme working environments.