Fe/C Nanocapsule-Decorated Fe₂B/C Nanocapsule Hybrids with Improved Gigahertz Electromagnetic Absorption Properties

We report an obvious improvement in gigahertz electromagnetic (EM) absorption properties in novel core/shell-structured magnetic/dielectric nanocapsule-decorated nanocapsule hybrids, featuring Fe/C nanocapsules of 4 nm mean diameter decorated on the surfaces of Fe₂B/C nanocapsules of 50 nm mean diameter (denoted as Fe/C@Fe₂B/C hybrids), as a result of the simultaneously enhanced dielectric and magnetic losses by an increased interfacial polarization at the Fe/C and Fe₂B/C heterogeneous interfaces and an additional tip effect by the decoration of small Fe/C nanocapsules. The phase, morphology, microstructure, and magnetization of the Fe/C@Fe₂B/C hybrids are investigated using various methods, and their EM absorption properties are evaluated in paraffin-bonded composites with 50 wt.% hybrids over the 2-18 GHz range. The results indicate a giant reflection loss (RL) of-49.5 dB at 10.5 GHz and a broad effective absorption bandwidth (for RL <-10 dB) of 8 GHz at a thin composite thickness of 2.1 mm. An extremely broad coverage of effective absorption bandwidth from 2.5 to 18 GHz is obtained at a very wide composite thickness range of 1-6 mm. The present study provides a new prospective for realizing high-performance EM absorbers at gigahertz frequencies.