Synergistic 2D structure design and high-entropy engineering in MnFeCoNiCu nanoalloy/carbon nanosheet composite to optimize impedance matching for high-attenuation microwave absorption

Abstract

High-entropy alloys (HEAs) are promising for microwave absorption owing to their excellent electrical and magnetic properties, yet achieving high-attenuation performance remains challenging. Herein, we report the synthesis of MnFeCoNiCu high-entropy nanoalloy/carbon nanosheet composites (MnFeCoNiCu/CSs) derived from a gluconate-based MnFeCoNiCu high-entropy solid solution with glucose as a self-foaming agent. A pre-foaming (400 °C) followed by carbothermal shock (1000 °C) strategy is employed, yielding excellent microwave absorption performance. By precisely tuning the carbon content in the MnFeCoNiCu/CSs, the impedance matching is optimized, enabling a synergistic dielectric-magnetic attenuation effect. First-principles calculations reveal that the intrinsic ferromagnetism and high-entropy nature of the MnFeCoNiCu nanoalloy induce magnetic moment resonance, magnetic coupling, and electronic dipole polarization. Meanwhile, the abundant alloy-carbon interfaces and the two-dimensional lamellar carbon skeleton facilitate interfacial polarization and conductive loss. The complementary magnetic-dielectric dissipation mechanisms endow MnFeCoNiCu/CS-1 with excellent impedance matching, achieving a minimum reflection loss (RL_min) of −54.4 dB at a thickness of 1.86 mm. Moreover, MnFeCoNiCu/CS-1 exhibits a maximum radar cross-section (RCS) reduction of 31.96 dB m², demonstrating its potential for practical applications. This work provides a feasible strategy for preparing HEAs/carbon composites with optimized impedance matching toward excellent microwave performance.