Self‐Templating Engineering of Hollow N‐Doped Carbon Microspheres Anchored with Ternary FeCoNi Alloys for Low‐Frequency Microwave Absorption

Abstract Rational design and precision fabrication of magnetic‐dielectric composites have significant application potential for microwave absorption in the low‐frequency range of 2–8 GHz. However, the composition and structure engineering of these composites in regulating their magnetic‐dielectric balance to achieve high‐performance low‐frequency microwave absorption remains challenging. Herein, a self‐templating engineering strategy is proposed to fabricate hollow N‐doped carbon microspheres anchored with ternary FeCoNi alloys. The high‐temperature pyrolysis of FeCoNi alloy precursors creates core‐shell FeCoNi alloy‐graphitic carbon nano‐units that are confined in carbon shells. Moreover, the anchored FeCoNi alloys play a critical role in maintaining hollow structural stability. In conjunction with the additional contribution of multiple heterogeneous interfaces, graphitization, and N doping to the regulation of electromagnetic parameters, hollow FeCoNi@NCMs exhibit a minimum reflection loss ( RL min ) of −53.5 dB and an effective absorption bandwidth (EAB) of 2.48 GHz in the low‐frequency range of 2–8 GHz. Furthermore, a filler loading of 20 wt% can also be used to achieve a broader EAB of 5.34 GHz with a matching thickness of 1.7 mm. In brief, this work opens up new avenues for the self‐templating engineering of magnetic‐dielectric composites for low‐frequency microwave absorption.