Ning Zhu, Jingyuan Ding, Zhengyu Zhang, Zhuo Sun, Rongzhi Zhao, Yuping Duan, Yixing Li
High-entropy alloys (HEAs) have recently emerged as promising candidates for electromagnetic compatibility (EMC) applications due to their unique compositional complexity and the synergistic interactions among constituent elements. However, their inherently limited dielectric loss capability significantly restricts their effectiveness in the high-frequency microwave region. To overcome this limitation, we report a plasma-assisted arc-discharge strategy for the in situ encapsulation of HEAs within multilayer graphitic shells, featuring heteroatom sulfur substitution. In this architecture, the graphitic carbon shells act not only as an effective dielectric loss medium but also as a reactive matrix for heteroatom-doped interface construction. Sulfur substitution induces the formation of localized heterostructures and interfacial dipoles, thereby enhancing interfacial polarization and improving dielectric loss. As a result, the FeCoNiCrCu@C composite exhibits a dramatically enhanced microwave absorption performance, with a minimum reflection loss (RLmin) of -53.55 dB and a broadened effective absorption bandwidth (≤-10 dB) of 5.45 GHz at a thickness of just 2.05 mm. This work presents a novel and scalable route for engineering high-efficiency microwave absorbers through tailored dielectric architectures in HEA-based systems.