Construction of FeNi₃ and core–shell structured FeNi₃@C microspheres toward broadband electromagnetic wave absorbing

The rational design of electromagnetic wave absorption (EMA) materials featured with broadband and high-efficiency in gigahertz (GHz) is still a great challenge. In this study, we prove fabricating FeNi₃ and FeNi₃@C core–shell microspheres to solve the challenge. The as-prepared FeNi₃ microspheres exhibits extremely broad effective absorption bandwidth (EAB, RL ≥ 10 dB, > 90 % absorbing) of 10.3 GHz (7.7–18.0 GHz) at only 2.0 mm, occupying 64.4 % of the investigated frequency range with a single matching thickness. Such an outstanding EMA performances is credited to strong dielectric loss and magnetic loss. Compared with pristine FeNi₃, the delicate design of core–shell structure and tailored synergistic effect of FeNi₃ and carbon produce positive reinforcement both in magnetic loss and dielectric loss, endowing FeNi₃@C samples with optimized impedance matching and appropriate attenuation ability. As a result, FeNi₃@C samples present impressive EMA performances from C to Ku band, especially for FeNi₃@C-3, demonstrating its potential of effectively dissipates electromagnetic wave in 6.1–18.0 GHz (RL ≥ 20 dB, > 99 % absorbing) by simply regulating a thickness of 1.5–2.5 mm. FeNi₃ and FeNi₃@C feature with optional broad bandwidth (completely covering C, X and Ku band), strong absorption, and thin thickness ensure them a superior EMA material.