Reduced graphene oxide(rGO)-Ferrite composite inks and their printed meta-structures as an adaptable EMI shielding material

Abstract

ABSTRACT Electromagnetic interference (EMI) shielding inks are generally conducting inks and therefore, are mostly reflection based. EMI shielding based on reflection are sometimes not suitable for certain applications apart from the fact that they themselves act as secondary source of EM waves. Here, we develop reduced graphene oxide (rGO)- zinc nickel ferrite (ZNF) and rGO-manganese (Mn)-doped zinc nickel ferrite inks for EM absorption in X-band, which have been tested in liquid state, coatings, and as printed meta-structures demonstrating versatile use of the inks. As a coating, the average EMI shielding of more than 30 dB is achieved in the 8 to 12 GHz range. The absorption properties of the rGO based ink can be increased from 50% to more than 80% by addition of a ferrite composite and can further be tuned by Mn doping. The dielectric measurement studies reveal that addition of Mn creates sites for interfacial polarization. The interfaces between polymer matrix, rGO, ZNF, and Mn contribute to conductivity, dipole and interfacial polarization losses, thereby augmenting absorption dominated EMI shielding. Cole-cole plot for the inks also indicates multiple relaxation processes confirming the role interfaces in absorption properties of the composite ink.