Enhanced microwave absorption of coral-like Co@Co7Fe3 at ultralow filler loading

Abstract

Due to their high density, it has been a big problem for metal materials to achieve high electromagnetic wave absorption (EWA) capabilities at low filler loading. Effective composition optimization and structural design are the key to solving this problem. Herein, a novel magnetic EWA composite (Co@Co₇Fe₃) with a unique coral-like three-dimensional hierarchical network (3DHN) structure was synthesized through a suitable thermal reduction process of Co₇Fe₃. The coral-like Co@Co₇Fe₃ composites possess high permeability and matched permittivity, resulting in excellent EWA performance. Typically, the sample synthesized by the thermal reduction of Co₇Fe₃ at 500 °C, denoted as CFA-5, displays an impressive minimum reflection loss (RL_min) of −61.99 dB at 5.82 GHz under low filler loading (5 wt%) and low thickness (2.49 mm) conditions, and a wide effective absorption bandwidth (EAB) of 5.62 GHz at a thickness of 4.00 mm. Moreover, the sample synthesized by the thermal reduction of Co₇Fe₃ at 600 °C (CFA-6) also shows a satisfactory RL_min of −35.62 dB at 1.40 GHz under extreme conditions with the filler loading of 2 wt% and a thickness of 1.41 mm. This work provides a facile structural design strategy to promote the practical application of metal magnetic materials in the electromagnetic absorption (EMA) field.