Composition design and performance regulation of three-dimensional interconnected FeNi@carbon nanofibers as ultra-lightweight and high efficiency electromagnetic wave absorbers

Highly dispersed fine FeNi nanoparticles (NPs) encapsulated within carbon nanofibers (FeNi@CNFs) have been fabricated through electrospinning followed by preoxidation and carbonization processes. The influences of FeNi content and filler loading on the electromagnetic (EM) and microwave absorption (MA) properties of the FeNi@CNFs/paraffin wax composites are studied in detail. Benefitting from the special hierarchical micro-structure including zero-dimensional FeNi@graphitic carbon core-shell NPs, one-dimensional CNFs with short carbon nanotubes protrusions and three-dimensional conductive network, as well as the synergistic effect be-tween small-sized magnetic FeNi NPs and lightweight dielectric CNFs, the as-prepared FeNi@CNFs samples exhibit excellent MA performances at the ultralow filler loading, in which the FeNi@CNFs-2 with a filling content of only 5 wt% possesses the strongest absorbing intensity and broadest effective frequency bandwidth primarily due to better balance between EM attenuation capability and impedance matching. The minimum reflection loss (RL) reaches-31.3 dB (more than 99.9% MA) at 16.3 GHz with a small thickness of 1.7 mm, and the maximum effective absorption bandwidth (RL <-10 dB) is up to 5.6 GHz (12.0-17.6 GHz) at 1.9 mm, which are superior to those of many previously reported magnetic carbon-based hybrid absorbers. Our results demonstrate that the proper incorporation of small-sized FeNi NPs into CNFs is an efficient and promising strategy to design light-weight and high-performance EM wave absorbers.