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.