Abstract: The rapid growth of modern communication technologies leads to increasingly serious electromagnetic interference (EMI) contamination, creating an urgent need for lightweight shielding materials that combine excellent shielding effectiveness (SE) with minimized reflected waves. In this work, an asymmetric bilayer composite aerogel consisting of a top ANF/Fe₃O₄ magnetic absorption layer and a bottom ANF/AgNPs conductive reflective layer using a sequential vacuum filtration technique was fabricated. Fe₃O₄ nanoparticles and AgNPs are in situ deposited onto aramid nanofibers (ANFs), forming tight interfacial contacts. The effects of Fe₃O₄ loading and absorption layer thickness on the microstructure, magnetic properties, and EMI shielding performance are systematically investigated. The optimal sample (Fe-HK/Ag) achieves an EMI SE of 80.6 dB with a reduced reflection coefficient of 0.75. The shielding mechanism follows an “absorption-reflection-reabsorption” multiple-loss pathway, where the conductive ANF/AgNPs layer provides strong reflection, while the ANF/Fe₃O₄ layer contributes magnetic and dielectric losses, and the porous ANF network promotes multiple scattering. Direction-dependent measurements show that incident from the ANF/Fe₃O₄ layer yields lower reflection and higher absorption, favorable for reducing secondary electromagnetic pollution. Moreover, the composite aerogels exhibit outstanding thermal stability and superparamagnetic behavior. This study offers a feasible route to develop lightweight, high-efficiency, and low-reflection EMI shielding materials with potential uses in aerospace, wearable devices, and advanced communication technologies.

Key words: Aramid nanofibers, Fe₃O₄ nanoparticles, Silver nanoparticles, Bilayer aerogel, Electromagnetic interference shielding