Graphene oxide co-doped with dielectric and magnetic phases as an electromagnetic wave suppressor
The fabrication of thin multilayer polymer nanocomposite films and their judicious arrangement in a sandwich structure to attenuate incoming electromagnetic (EM) radiation, mostly by absorption, is discussed herein. Two key properties (reasonably high conductivity, with high dielectric loss and magnetic permeability) were targeted here by using multiwall nanotubes (MWCNTs) and BaTiO3/Fe3O4 (BT/Fe) co-doped graphene oxide (GO) sheets to design soft functional nanocomposites using bi-component blends of PC (polycarbonate) and PVDF (polyvinylidene fluoride). High dielectric loss and magnetic permeability were achieved by uniformly distributing BT and Fe nanoparticles on the huge specific surface area provided by the GO sheets. The MWCNTs were non-covalently modified to exfoliate the nanotubes and to get a well-connected structure of the blend components. The MWCNTs were thoroughly characterized by TEM, UV-vis, fluorescence emission, Raman and TGA. This surface modification of the MWCNTs also helps with their specific localization in the continuous bi-component blends. BT and Fe were co-doped onto the GO sheets by a well-designed step-by-step synthesis protocol, and the product can facilitate the absorption of incoming EM radiation. This hybrid structure was thoroughly characterized by various microscopic and spectroscopic techniques. By following a sequential mixing protocol, the BT/Fe co-doped GO sheets can be specifically localized in the PC components of the blends while the MWCNTs localize in the PVDF phase through a process driven by thermodynamics. This provides excellent heterogeneous boundaries with multiple scattering within the engineered nanostructures, in addition to retaining the conducting network and the associated dielectric loss properties. The resultant local field variation of such boundaries and the presence of highly lossy materials readily enhance the EM attenuation coefficient. The bulk compositions exhibited a high shielding effectiveness (SE) of −35 dB at 18 GHz (>85% absorption), and when rationally stacked into a multilayer architecture with absorption–multiple reflection–absorption pathways, the SE was further enhanced to −46 dB for a thin shield of 0.9 mm thickness. Such a high SE indicates >99.99% attenuation of the incoming EM radiation. This new-generation EM suppressor, distinguished by its multifunctionality and tunable dielectric and magnetic properties, hence offers an amendable, cost-effective replacement to existing solutions.