Electromagnetic interference shielding material for super-broadband: multi-walled carbon nanotube/silver nanowire film with an ultrathin sandwich structure

High-performance electromagnetic interference (EMI) shielding materials that are effective under a wide range of conditions are highly attractive for eliminating electromagnetic pollution in fifth-generation communication. Here, we report a sandwich-layered hybrid film (12 μm) constructed by multi-walled carbon nanotubes (MWCNTs) and silver nanowires (Ag NWs) via vacuum-assisted filtration. In the ultra-wideband (4–40 GHz), the EMI shielding effectiveness (EMI SE) was higher than 45 dB with a maximum of 72 dB at 10 GHz. This superb EMI SE can be attributed to the design of the alternating Ag NW/MWCNT structure, in which the Ag NWs with high conductivity provide ohmic loss, and the MWCNTs with abundant defects induce polarization loss. Such a structure improves impedance matching through the top layer of the MWCNTs and enhances multiply reflected absorption by the macroscopic interface between the MWCNT layer and the Ag NW layer. Moreover, DFT calculations verified that the existence of an Ag/C micro-interface caused uneven distribution of charges, which contributed to dipole polarization. Considering practical applications, the film maintained superior EMI SE under complex environments (hot, cold, and bending) and exhibited excellent heat dissipation properties. This work facilitates the further development of super-wideband EMI shielding materials for broad applications.