Extraordinary Synergy in Attenuating Microwave Radiation with Cobalt-Decorated Graphene Oxide and Carbon Nanotubes in Polycarbonate/Poly(styrene-co-acrylonitrile) Blends

Polymeric nanocomposites were developed using polycarbonate (PC) and poly(styrene-co-acrylonitrile) (SAN) containing cobalt nanoparticles decorated onto partially reduced graphene oxide (rGO) sheets and multiwalled carbon nanotubes (MWNTs). In order to absorb microwave radiations, the PC phase was rendered electrically conducting by selectively localizing the MWNTs in the PC phase of the blends. The synergetic effect from the conducting phase (MWNTs), the dielectric phase (rGO), and the ferromagnetic phase (cobalt nanoparticles) on microwave absorption was assessed by measuring the scattering parameters using a vector network analyzer coupled to a coaxial line. The electromagnetic interference (EMI) shielding effectiveness (SE) was studied over a broad range of frequencies including the X-band (8-12 GHz) and the Ku-band (12-18 GHz). This strategy resulted in enhanced electrical conductivity and facilitated in outstanding microwave absorption. For instance, the PC/SAN blends with MWNTs manifested significantly high total shielding effectiveness (SET) mainly through absorption, in contrast to PC/MWNT composites for which reflection dominated the attenuation mechanism. The interconnected network of MWNTs and cobalt-decorated r-GO (rGO-Co) resulted in enhanced electrical conductivity and EMI shielding effectiveness (SE). This in turn resulted in a shielding effectiveness of -34 dB at 18 GHz. The mechanism of EM wave absorption was systematically evaluated through detailed analysis of relative permittivity and permeability in the measured frequency regime. The absorption of EM radiation was noticeably enhanced due to high dielectric and large magnetic losses in the blends containing rGO-Co and MWNTs. Moreover, it was also realized that the significantly enhanced attenuation constant resulted in maximum microwave absorption in the blend containing MWNT and rGO-Co.