Ultralight hierarchical skin–core CoSe@C/carbon nanofiber aerogel fibers for broadband microwave absorption

The growing demand for protection against electromagnetic interference has driven the development of ultralight microwave absorbers with strong attenuation capability and broad effective bandwidth. Herein, ultralight hierarchical skin–core CoSe@C/carbon nanofiber aerogel fibers (CoSe@C/CNFAFs) are fabricated by integrating CoSe@C nanoparticles onto aramid-derived carbon nanofiber aerogel fibers through ZIF-67 immobilization and subsequent selenization/carbonization. The resultant aerogel fiber exhibits a distinct skin–core architecture and an interconnected porous network, which not only minimizes density but also improves impedance matching and facilitates multiple scattering and reflection of incident microwaves. Meanwhile, the abundant heterogeneous interfaces between CoSe, carbon shells, and carbon nanofiber frameworks, together with structural defects in the carbon matrix and selenium-related vacancies, synergistically enhance interfacial polarization, dipolar polarization, and conductive loss. Benefiting from these structural and compositional advantages, the optimized CoSe@C/CNFAF800 delivers a minimum reflection loss of −62.51 dB at a thickness of 2.95 mm and an effective absorption bandwidth of 7.4 GHz at 2.7 mm with an ultralow filler loading of only 1 wt%. In addition, radar cross-section simulations reveal an enhanced electromagnetic wave attenuation capability under practical incident conditions, with a maximum reduction of 59.87 dB m 2 . This work highlights the great potential of hierarchical skin–core metal selenide/carbon aerogel fibers for achieving lightweight, broadband, and high-efficiency microwave absorption, and provides a feasible strategy for the design of next-generation ultralight electromagnetic wave absorbers. Download: Download high-res image (619KB) Download: Download full-size image