Design and fabrication of durable composite foams with absorption-dominated electromagnetic shielding performance

Abstract

The increasing prevalence of high electromagnetic (EM) wave radiation underscores the critical need for developing effective electromagnetic interference (EMI) shielding materials. Herein, we designed a heterogeneous structure featuring dual-resonance cavity, comprising an absorption layer formed by waterborne polyurethane (WPU)/carbon nanotubes (CNTs) aerogel and a shielding layer consisting of Ag-coated polystyrene (PS) microspheres (Ag@CHPMs) embedded with CNTs and Ag-coated hollow carbon nanospheres (AgHCSs). The shielding layer established a dual-resonance cavity through strategically incorporating AgHCSs into the Ag@CHPMs, which optimized impedance matching characteristics and significantly enhanced EM shielding performance. This innovative structure enabled multimodal EM wave dissipation through synergistic conductive loss, interfacial polarization, and cavity resonance effects. The EMI shielding performance of the composite foam was optimized when it consisted of a 1.3 mm thick shielding layer (Ag@CHPMs substrate layer) and a 2.7 mm thick absorption layer (the CNTs/WPU aerogel layer). In this case, the employing Ag@CHPMs with 100 μm microspheres in the shielding layer demonstrated exceptional X-band EM shielding effectiveness (SE) of 45.5 dB, coupled with a high absorption coefficient of 0.7. Furthermore, the foam exhibited exceptional flexibility and fatigue resistance, retaining high performance after 500 bending cycles. This work presents an innovative design strategy for the development of highly efficient absorption-dominated EMI shielding materials, offering significant potential for advancements across various applications.