Microwave absorbers based on foamed nanocomposites with graded concentration of carbon nanotubes

A multilayered foamed nanocomposite with graded concentration of carbon nanotubes is proposed as a novel microwave absorber. The dispersion and foaming process enables to control the gradation in conductivity of each layer. Absorption performances are demonstrated through measurements of reflectivity and shielding effectiveness over the frequency range [8-16 GHz]. An improvement of about 5 dB in reflectivity is observed with respect to a foamed composite having a similar uniform concentration, while in both cases the shielding effectiveness is kept higher than 15 dB.