Quinary High‐Entropy‐Alloy@Graphite Nanocapsules with Tunable Interfacial Impedance Matching for Optimizing Microwave Absorption

Abstract Designing heterogeneous interfaces and components at the nanoscale is proven effective for optimizing electromagnetic wave absorption and shielding properties, which can achieve desirable dielectric polarization and ferromagnetic resonances. However, it remains a challenge for the precise control of components and microstructures via an efficient synthesis approach. Here, the arc‐discharged plasma method is proposed to synthesize core@shell structural high‐entropy‐alloy@graphite nanocapsules (HEA@C‐NPs), in which the HEA nanoparticles are in situ encapsulated within a few layers of graphite through the decomposition of methane. In particular, the HEA cores can be designed via combinations of various transition elements, presenting the optimized interfacial impedance matching. As an example, the FeCoNiTiMn HEA@C‐NPs obtain the minimum reflection loss (RL min ) of −33.4 dB at 7.0 GHz (3.34 mm) and the efficient absorption bandwidth (≤−10 dB) of 5.45 GHz ranging from 12.55 to 18.00 GHz with an absorber thickness of 1.9 mm. The present approach can be extended to other carbon‐coated complex components systems for various applications.