Joule-Heating-Driven Synthesis of a Honeycomb-Like Porous Carbon Nanofiber/High Entropy Alloy Composite as an Ultralightweight Electromagnetic Wave Absorber.

High entropy alloys (HEA) have garnered significant attention in electromagnetic wave (EMW) absorption due to their efficient synergism among multiple components and tunable electronic structures. However, their high density and limited chemical stability hinder their progress as lightweight absorbers. Incorporating HEA with carbon offers a promising solution, but synthesizing stable HEA/carbon composite faces challenges due to the propensity for phase separation during conventional heat treatments. Moreover, EMW absorption mechanisms in HEAs may be different from established empirical models due to their high-entropy effect. This underscores the urgent need to synthesize stable and lightweight HEA/carbon absorbers and uncover their intrinsic absorption mechanisms. Herein, we successfully integrated a quinary FeCoNiCuMn HEA into a honeycomb-like porous carbon nanofiber (HCNF) using electrostatic spinning and the Joule-heating method. Leveraging the inherent lattice distortion effects and honeycomb structure, the HCNF/HEA composite demonstrates outstanding EMW absorption properties at an ultralow filler loading of 2 wt %. It achieves a minimum reflection loss of -65.8 dB and boasts a maximum absorption bandwidth of up to 7.68 GHz. This study not only showcases the effectiveness of combining HCNF with HEA, but also underscores the potential of Joule-heating synthesis for developing lightweight HEA-based absorbers.