Heterostructure design of 3D hydrangea-like Fe3O4/Fe7S8@C core-shell composite as a high-efficiency microwave absorber

In an era dominated by electronic equipment, the development of high-efficiency electromagnetic wave (EMW) absorbers is of great significance in solving the problem of electromagnetic (EM) pollution. Heterointerface engineering for optimizing EMW absorption performance depends on the design of vacancy, defect, and heterogeneous interface, which remains a considerable challenge in adjusting the micro and macro-interface effects. In this work, S atoms are incorporated into a dielectric-magnetic complementary system (Fe3O4/Fe7S8@C) to arouse the polarization effect of vacancies, defects, and non-uniform interfaces, thus tremendously boosting the EM energy attenuation capacity. Besides, the carbon shell provides more propagation paths for the dissipation of EMWs, and dielectric-magnetic synergy improves impedance matching. Eventually, in comparison with Fe2O3 and Fe3O4@C composites, interface-engineered Fe3O4/Fe7S8@C acquires a much better EM wave absorption performance. Its minimum reflection loss value reaches as much as −56.2 dB with a thickness of only 1.6 mm, and the corresponding effective absorption bandwidth (EAB) is up to 4.5 GHz. This unique hydrangea-like layered structure provides space to facilitate non-uniform coupling between the layers and has strong anisotropy to enhance the magnetic response. The high density of magnetic flux in the nanosheets builds a three-dimensional magnetic coupling network, which is supported by off-axis electron holography. Besides, the radar cross section from HFSS simulation further confirms that S-doping can favor the best synergy between dielectric and magnetic losses, facilitating the composite to achieve a more optimal impedance matching and improve the absorption capacity. In conclusion, this work presents new ideas for the design of excellent absorbing materials.