A multi-layer core–shell structure CoFe2O4@Fe3C@NiO composite with high broadband electromagnetic wave-absorption performance

Abstract

Enhancing the absorption strength of electromagnetic waves and broadening the absorption band are constant goals in designing and preparing absorbing materials. The use of composites has shown to be a very efficient method for acquiring broadband-absorbing materials, while the construction of a core–shell structure has demonstrated a significant enhancement in absorption capability. In this paper, the nanocomposite metal–organic framework (MOF) derivative CoFe₂O₃@C with a double core–shell structure and the nanocomposite MOF derivative CoFe₂O₄@Fe₃C@NiO with a three-layered core–shell structure have been prepared using a chemical compound. The multi-layer structure provides more active sites for the multiple reflection and scattering of electromagnetic waves, effectively improving the attenuation capability. The effective absorption band (EAB) (reflection loss (RL) ≤ −5 dB) of both CoFe₂O₃@C and CoFe₂O₄@Fe₃C@NiO are broadened compared to that of the ZIF-67 derivative. In particular, the minimum reflection loss (RL_min) of CoFe₂O₃@C was −52.7 dB at 13.3 GHz and 2.04 mm, and the EAB (RL ≤ −5 dB) is as wide as 9.35 GHz. Compared with the ZIF-67 derivative, the EAB exhibits a twofold rise, accompanied by a corresponding thickness increase of just 0.24 mm. At a matched thickness of 2.2 mm, the EAB of CoFe₂O₄@Fe₃C@NiO can even reach 11.9 GHz.