Carbon nanotubes films in glass fiber polymer matrix forming structures with high absorption and shielding performance in X-Band

Abstract

Thin films based on carbon nanotubes materials are used to form layered structures for electromagnetic absorption and shielding applications over X-Band. Measurements in a WR-90 waveguide with a Vector Network Analyzer are carried out to determine the dielectric characteristics of the materials. Samples of graphene and carbon nanotubes are constructed in an epoxy resin polymeric matrix as a one-layer structure. A two-layer structure based on epoxy resin and glass fiber combined with carbon nanotubes films is also examined. Films have a thickness of around 70 μm and have a significant effect in the attenuation of the electromagnetic field. A decrease of more than 20 dB in the Transmission Coefficient can be achieved even with few carbon nanotubes films placed intermediately in a glass fiber polymer matrix. Simulated results compared to measurements of the waveguide setup show satisfactory agreement. Planar layers composed of the above materials are also examined for electromagnetic absorption and shielding performance. A one-layer planar structure that consists of the above carbon nanotubes films in a glass fiber polymer matrix and has a total thickness of 2.7 mm is proposed. It is intended for high shielding effectiveness applications presenting a shielding effectiveness variating between 27 dB and 42 dB over X-Band. However, for both high shielding and absorption applications, a two-layer planar structure with a total thickness of 5.7 mm is designed. The structure consists of successive carbon nanotubes films in a glass fiber polymer matrix as the bottom layer and carbon nanotubes in an epoxy resin matrix as the top layer. The structure presents a shielding effectiveness between 27 dB and 40 dB over X-Band while absorption can reach 95% around 10 GHz. As shown, adding carbon nanotubes in film structure, even with a thickness in the order of μm, inside a polymer matrix can greatly increase the electromagnetic shielding and absorption performance showing also a high attenuation of electromagnetic field.