Electrospinning Construction of 3D Networked CuS/Fe ₃ O ₄ /C Nanocomposites for Broadband Microwave Absorption

The development of electromagnetic microwave (EMW) absorbers featuring broad bandwidth, low cost, and engineering feasibility is considered strategically important to address the application demands of 5G/6G communications and stealth technologies. In this study, the CuS/Fe3O4/C nanocomposites with enhanced absorption properties were synthesized through the incorporation of CuS into a polyacrylonitrile (PAN) precursor using electrospinning technology. The obtained composites demonstrate an ultrawide effective absorption bandwidth (EAB) in the X and Ku bands, achieving a minimum reflection loss (RLmin) of −50.37 dB at 15.44 GHz with a thickness of 1.9 mm, along with an EAB of 4.8 GHz (RL ≤ −10 dB, 13.2–18 GHz). For the CuS/Fe3O4/C nanocomposites with 10% CuS loading, optimal EMW absorption performance was observed at 3.5 mm, exhibiting an RLmin of −40.09 dB at 6.96 GHz and an ultrawide EAB covering 9.6 GHz (RL ≤ −10 dB, 8.4–18 GHz). Based on Cole–Cole curve analysis, the nanocomposite with 20% CuS loading is characterized by five distinct and well-defined relaxation arcs, confirming its remarkable dielectric loss capability. Furthermore, CST simulation results indicate that the radar cross-section (RCS) values of compressed samples were significantly reduced, which is attributed to improved magnetic absorption. These findings substantiate that the superior EMW absorption performance of the nanocomposites stems from a strong polarization loss mechanism and considerable eddy current loss. This study underscores the significant potential of the CuS/Fe3O4/C nanocomposites in ultrabroadband EMW absorption research and offers valuable guidance for further in this area.