Synthesis of lightweight, hierarchical cabbage-like composites as superior electromagnetic wave absorbent

•A new 3D hierarchical cabbage-like electromagnetic wave absorbent.•The maximum reflection loss (RL) of Fe/CCMs-500 reached −22.9 dB.•The effective absorption bandwidth (RL ⩽ −10 dB) was 4.32 GHz.•Wide absorption frequency range, strong absorption ability and light weight.

Three-dimensional (3D) hierarchical cabbage-like carbonaceous materials (Fe/CCMs-X, X means treating temperature) have been successfully prepared employing combinatorial processes of cobalt-assisted hydrothermal carbonization (HTC) of furfural and subsequent iron salt impregnation and thermal treatment. This new absorbent was characterized using powder X-ray diffraction (XRD), N2 adsorption–desorption isotherms, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM) techniques. The maximum reflection loss (RL) of Fe/CCMs-500 reached −22.9 dB, and the effective absorption bandwidth (RL ⩽ −10 dB) was 4.32 GHz (7.76–9.84 GHz and 11.20–13.44 GHz) corresponding to an absorber thickness of 2.5 mm, a low loading amount of iron (6.83%) component and high carbon content (69.8%), clearly demonstrating its wide absorption frequency range and strong absorption ability. It is thus believed that the newly synthesized Fe/CCMs-500 can serve as light-weight electromagnetic wave absorbent and can be potentially used in practice.

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