Versatile graphene-alumina nanofibers for microwave absorption and EMI shielding

Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer struc-ture with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 +/- 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 degrees C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the ob-tained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of-25 dB at similar to 11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption character-istics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.Funding Agencies|Estonian Research Council (ETAG) [PSG466]