Electromagnetic Absorption Properties of Carbon Nanotube Nanocomposite Foam Filling Honeycomb Waveguide Structures

Carbon nanotube reinforced polymer foams filling a metallic honeycomb were processed and characterized for the production of hybrid materials with high electromagnetic absorption potential. Electromagnetic modeling and experimental characterization of the hybrids proved that the honeycomb, acting as a hexagonal waveguide, improves the absorption properties in the gigahertz range above the cutoff frequency. The electromagnetic absorption can be tuned by changing the hybrid material properties. The required levels of electrical conductivity are attained owing to the dispersion of low amounts (1-2 wt%) of carbon nanotubes inside the polymer matrix. The combination of the foam and honeycomb architecture contributes to decrease the real part of the relative effective permittivity Re{ε_r,eff }. Varying the cell shape of the honeycomb changes the frequency range for high absorption. An analytical model for the absorption has been developed, showing good agreement with the experimental results.