High performance electromagnetic wave absorbers derived from PC/SAN blends containing multiwall carbon nanotubes and Fe3O4 decorated onto graphene oxide sheets

Abstract

A high performance electromagnetic wave absorber with high surface resistivity (i.e. minimum surface reflection) and an enhanced attenuation constant (i.e. maximum absorption) was designed using uneven distribution of lossy materials like multiwall carbon nanotubes (MWNTs) and magnetic ferrite (Fe₃O₄) nanoparticles (of 2–5 nm) nucleated on reduced graphene oxide sheets (rGO–Fe₃O₄) in biphasic polymeric blends of polycarbonate (PC) and poly(styrene-co-acrylonitrile) (SAN). The uneven distribution of MWNTs and rGO–Fe₃O₄ in the blends, which acted as micro-absorbers resulted in outstanding electromagnetic wave absorption (93%). Various parameters like transmission coefficient, attenuation constant and skin depth were assessed for a clear understanding of the attenuation mechanism in each of the blends containing different nano-inclusions like MWNTs and Fe₃O₄, only rGO–Fe₃O₄ and a combination of MWNTs and rGO–Fe₃O₄. It is understood that the absorption was significantly enhanced due to selective localization of nano-inclusions in the PC phase that provided heterogeneous dielectric media with multiple interfaces. The penetration of the high frequency electromagnetic waves into the shield was facilitated by high surface resistivity and high volume electrical conductivity (5 S cm⁻¹). Further, in combination with lossy nano-inclusions the incoming EM radiation was attenuated through multiple scattering. This is realized in the blends containing both MWNTs and rGO–Fe₃O₄ which manifested in a total shielding effectiveness of −50.7 dB (at 18 GHz), indicating >99.9% attenuation of the incoming microwave radiation, in striking contrast to blends containing either only MWNTs or only rGO–Fe₃O₄. Taken together, this study clearly demonstrates that lightweight polymeric nanocomposites can be designed for high frequency electromagnetic wave absorption through unique synergism of MWNTs and ultra-small magnetic ferrite nanoparticles nucleated on rGO sheets.