Tailoring of electromagnetic properties of arc-produced carbon-coated FeNi alloy nanocapsules for highly efficient microwave absorption

Due to the growing harm of electromagnetic radiation, it is extremely urgent to develop high-efficiency microwave absorbers with tunable electromagnetic properties. Herein, a simple strategy for synthesizing hetero-atoms (sulfur) doped carbon-coated FeNi alloy nanocapsules (FeNi@C(Sx) NCs) by DC arc-discharge plasma was demonstrated. The hetero-interface between the FeNi alloy core and the graphitic shell induce interfacial polarization was found. Meantime, many defects produced by substitutional sulfur atoms in the graphitic shell facilitated dipole polarization and conduction loss. Besides, the multiple magnetic resonance produced by FeNi magnetic alloys worked together to optimize impedance matching. The excellent microwave absorption performance was attributed to the core-shell structure, dipole and interface polarizations, as well as favorable impedance matching. Importantly, the first-principles calculation was applied to prove the charge transfer and polarization process. The minimum reflection loss (RL) can reach up to −50.3 dB at a thickness of 1.6 mm.