Effect of fabrication method on the structure and electromagnetic response of carbon nanotube/polystyrene composites in low-frequency and Ka bands

Casting, forge-rolling, and stretching methods have been used for preparation of polystyrene composites with 0.25 wt.% loading of multiwall carbon nanotubes (MWCNTs). Electromagnetic properties of the composites were studied using impedance spectroscopy and microwave probing in the Ka band. Analysis of impedance spectra revealed capacitive behavior of the forge-rolled composite and charge tunneling through a polystyrene layer separating the nanotubes in two other composite samples. The stretched composite demonstrated anisotropy of microwave response due to predominant orientation of nanotubes along deformation direction. The near-isotropic shielding efficiency of the forge-rolled composite was attributed to strong fragmentation of MWCNTs under applied shear forces.