Iron–cobalt/carbon nanocomposites with adjustable impedance matching and a wide effective absorption bandwidth as outstanding microwave absorbers

Abstract

The spatial confinement effect provides a promising route for fabricating efficient microwave absorbing materials (MAMs) by enabling precise regulation of magnetic metal particle size and distribution in carbon fibers, thereby enhancing their microwave absorption (MA) performance. In this study, confined FeCo@C fibers (FeCo/CNFs) with multiwall carbon nanotubes are fabricated via a two-step process of electrospinning and carbon thermal reduction to investigate the electromagnetic characteristics. By adjusting the loading content of the sample in paraffin, the impedance matching and the effective absorption bandwidth (EAB) of the FeCo/CNF absorbers are regulated. The MA performance is assessed in the 2.0–18.0 GHz range, and as expected, when the loading content of the sample is 20 wt%, the FeCo/CNFs sample shows ideal reflection loss (RL) features, where a high RL value (–49.1 dB at 6.3 GHz), a wide EAB (2.1 GHz (5.3–7.4 GHz), RL ≤ –10.0 dB), and a thin matching thickness (3.9 mm) can be achieved. Moreover, when the matching thickness is regulated to 4.4 mm, the maximum EAB is gained as 4.4 GHz (13.6–18.0 GHz). Notably, the synthesis of confined FeCo@C nanofibers is a facile, recyclable, and low-cost method for fabricating nanoscale carbon-based MAMs. Meanwhile, the FeCo/CNFs nanocomposite offers a valuable reference for developing lightweight dielectric-magnetic absorbers with excellent MA performance.