[EN] 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 structure 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 °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 obtained 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 ∼11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption characteristics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.

This research was supported by the Estonian Research Council (ETAG) under the personal grant PRG643 (I. Hussainova). R.E. Rojas-Hernandez acknowledges the financial support of the Estonian Research Council (ETAG) through PSG466. The RawMatTERS Finland infrastructure (RAMI) facilities based at Aalto University is acknowledged for low temperature electronic transport measurements. Aalto University Nanomicroscopy Center, OtaNano facilities are acknowledged for TEM images. Johanna Rosen acknowledges funding from the Knut and Alice Wallenberg (KAW) Foundation for a Fellowship/Scholar Grant and Project funding (KAW 2020.0033). The contribution of Niraj Kumar Singh is acknowledged for Hall measurements. The authors acknowledge the originality of all figures, including the TOC graphics.

Appendix A. Supplementary data The following is the Supplementary data to this article: Fabrication procedure of the composites; additional Raman spectroscopy data; additional dielectric data.

Peer reviewed