Layered double hydroxides derived 3D flower-like FeNi@C microspheres as lightweight and high-efficient electromagnetic wave absorber

Abstract

Layered double hydroxides (LDH) are employed as a promising template to prepare magnetic polymetallic alloys with hierarchical or hollow structure, being regarded as the promising candidates for the lightweight and high-performance electromagnetic wave (EMW) absorption materials. However, the application of LDH-derived magnetic alloys in EMW absorption is still limited by the single loss mechanism and poor impedance matching properties. Coupling with dielectric materials is a viable strategy to solve the issue. Herein, flower-like hierarchical FeNi@C microspheres are fabricated by pyrolysis of FeNi-LDH precursors, which display excellent EMW absorption performance. Good impedance matching and strong absorption capability of the FeNi@C microspheres can be realized by regulating the phase composition and microstructure under different pyrolysis temperatures. When pyrolyzed at 700 °C, the FeNi@C microspheres exhibit a strong reflection loss (RL) of −30.4 dB with ultra-thin matching thickness of only 1.2 mm, achieving the widest effective bandwidth (RL < −10 dB) of 4.6 GHz at 1.4 mm. The superior EMW absorption performance of the FeNi@C-700 sample is ascribed to the synergistic effects of hierarchical structure with multiple reflection, FeNi particles with magnetic loss and carbon matrix with dielectric loss. Thus, the as-obtained FeNi@C microspheres can be a prospective lightweight EMW absorber. This work can also provide guidance for design and development of hierarchical LDH derivatives in EMW absorption.