Radar absorbing properties of carbon nanotubes/polymer composites in the V-band

This research is devoted to the study of radar absorbing properties of the composites, based on the epoxy binder and carbon nanotubes (CNT) in the frequency range of 52-73 GHz. Three species of unmodified multi-walled CNT differing in length and diameter were investigated as fillers. The reflection coefficients (K (refl)) at the radar absorbing material (RAM)-air interface and the electro-magnetic radiation (EMR) absorption coefficients (K (abs)) in the materials with the different content of nanotubes were measured (K (refl) and K (abs) were calculated using the highest (the worst) value of the voltage standing-wave ratio (VSWR) in the frequency range of 52-73 GHz). It was established that the increase in nanotubes aspect ratio (a ratio of CNT length to its diameter) leads to K (abs) rising for polymer composites. Also, CNT diameter decrease leads to K (refl) reduction. CNT of 8-15 nm in diameter and more than 2 mu m in length are the most effective from all investigated fillers. The reflection loss values were calculated and CNT optimal concentrations were obtained at different thickness of RAMs.