S‐parameters, electrical permittivity, and absorbing energy measurements of carbon nanotubes‐based composites in X‐band

Composites based on carbon nanotubes (CNT) have recently received great attention as a possible new generation of radar absorbing materials (RAM), due to their efficient microwave attenuation capacity and low density. However, RAM performance can vary significantly depending on the CNT being used. Aiming to directly show the influence of CNT from two different suppliers, both multi‐walled and non‐functionalized (CNT‐B and CNT‐K), the electromagnetic behaviors of RAM processed in epoxy resin are compared. Scattering parameters (S‐parameters), complex electrical permittivity and magnetic permeability, and absorbed energy of the composites in the X‐band (8.2–12.4 GHz) are evaluated. The results clearly show the influence of the two different CNT on the electromagnetic characteristics of composites. CNT‐B based composites behave as broadband RAM with the tendency of better attenuation results above 12.4 GHz. On the other hand, CNT‐K based composites show good attenuation results in the X‐band (>99%). Undoubtedly, the results confirm that the longer length of CNT‐K favored the interconnection among the filaments, as well as, the formation of compact agglomerates surrounded by resin rich regions, which favored the impedance matching and mechanisms of losses in the processed RAM.