Optimizing the Electromagnetic Wave Absorption Performances of Designed Co₃Fe₇@C Yolk-Shell Structures

Due to the increasing demand for military and commercial applications, magnetic metal-based core@shell nanostructures have attracted extensive attention in the field of electromagnetic wave (EMW) absorption materials. To further improve the overall performance, herein, an effective strategy is designed to fabricate Co₃Fe₇@C yolk-shell structures by using (Co_0.9Fe_0.1)Fe₂O₄@phenolic resin core@shell structures as precursors. The structure parameters, including the size of the CoFe alloy cores, the thickness of the carbon shell, and the void between the core and the shell, can be tailored by controlling the reaction conditions. It is demonstrated that the EMW absorption properties of the as-prepared Co₃Fe₇@C yolk-shell structures are closely related to their structure parameters. The optimized Co₃Fe₇@C yolk-shell structure shows excellent EMW absorption performance, the strongest reflection loss (RL) is up to -35.3 dB at 9.1 GHz with the matching thickness of 2.0 mm, and the effective bandwidth (RL < -10 dB) can reach 8.4 GHz (9.6-18 GHz) with a thickness of only 1.5 mm. It is revealed that the excellent performances stem from the unique yolk-shell structure as well as the complementarities and synergies between the dielectric loss and the magnetic loss. By rational designing, the magnetic metal alloy@carbon yolk-shell structures will be convinced to have the potential as novel high-efficiency EMW absorption materials with lightweight, low thickness, wide absorption frequency, high stability, and strong absorption characteristics.