Lightweight asymmetric C/SiC nanofiber film with conductive-dielectric gradient for adjustable electromagnetic interference shielding

Design novel interfacial structure material to achieve highly efficient electromagnetic interference (EMI) shielding is one of the biggest challenges. Herein, the asymmetric C/SiC nanofiber film with conductive-dielectric gradient was precisely in situ prepared through the carbon thermal reduction reaction during the Flash Joule Heating (FJH) process. For the Fick diffusion of SiO₂ vapor, the SiC nanoparticles were gradually anchored on the carbon fibers with a gradient distribution from bottom to top. The electrical conductivity of the asymmetric C/SiC nanofiber film was thus continuously increasing from about 7.97 S cm⁻¹ (bottom) to 0.59 S cm⁻¹ (top). As a result, the asymmetric C/SiC nanofiber film achieved a maximum EMI shielding effectiveness (62.0 dB) in the X-band with a thickness of 1.5 mm, and superior stability in various extreme conditions. Moreover, the EMI shielding effectiveness of the asymmetric C/SiC nanofiber film can be adjusted by altering the incident direction or the film thickness. The effects of gradient structure on the potential distribution and electromagnetic wave loss for the asymmetric film were investigated by the Kelvin probe force microscope and finite element simulation analysis. This work provides a novel insight into designing reasonable interfacial structure to modulate EMI shielding performance.