Nowadays, to tackle the increasingly severe electromagnetic pollution problem, developing high-performance electromagnetic wave (EMW) absorption materials with lightweight and broadband is emergently desirable. In this work, hollow structured CoFe@C@hydrothermal carbon (CFCHC) nanocomposites were synthesized by in situ carbon reduction encapsulation of glucose-coated CoFe-nitrilotriacetic acid (CoFe-NTC) precursors, in which magnetic CoFe@C nanocapsules were densely dispersed and confined in ultrathin carbon shells. In addition, samples with controlled calcination and different thicknesses of glucose-carbon shells were synthesized and investigated. The special hollow and mesh-like fiber structure, excellent conductive loss, multiple polarization relaxation, and suitable impedance matching endow CFCHC samples with good attenuation ability for incident EMW. As a result, for the CFCHC-0.6 sample with a glucose-carbon shell of only 7 nm, the minimum reflection loss (RL) of − 61.35 dB and wide effective absorption bandwidth (EAB) of 6.72 GHz were achieved with a filler loading of 10 wt%. Meanwhile, the radar cross section (RCS) simulation revealed that the largest RCS reduction value of CFCHC-0.6 is up to 22.04 dBm2 at 0° incidence angle, demonstrating its strong radar wave attenuation ability. Consequently, the as-prepared CFCHC-0.6 nanocomposites hold the potential to serve as a strong broadband absorber for practical application. It is believed that this systematic study may provide a novel inspiration for the design and development of lightweight and high-efficiency EMW absorbing materials.
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