Wideband radar absorbing panels with lossy multilayer graphene and carbon nanofiber-based coating

A novel lightweight wideband radar absorbing material (RAM) for radio-frequency is developed using a rohacell (RC) panel coated with a film of carbon nanostructures. The coating is produced through the dispersion of either commercial graphene nanoplatelets (GNPs) or carbon nanofibers (CNFs) in 1-propanol and the deposition of the so-obtained colloidal suspension onto the RC surface with a bristle brush. Finally, a polymeric film is deposited over the carbon-based lossy layer in order to protect the lossy coating from the external environment. The electromagnetic properties of the produced panels are investigated through reflection coefficient measurements in the X and Ku bands. It is demonstrated that the RAM with the GNP-based lossy layer has a −10 dB bandwidth of ∼7 GHz, but the polymeric top layer degrades its performances, resulting in a minimum reflection coefficient of −9 dB. With the CNF-based lossy layer it is possible to fabricate a RAM with a −10 dB bandwidth of ∼10 GHz. The application of the protective layer reduces the bandwidth to ∼6 GHz.