A sandwiched SiBCN@CF/CNTs film with electrically conductive network for electromagnetic interference shielding

High-performance electromagnetic interference (EMI) shielding materials are required for advanced electronic devices and communication systems. Here, a nanocarbon-reinforced-silicon boron carbonitride film (denoted as SiBCN@CF/CNTs) with sandwiched structure was prepared via polyborosilazane (PBSZ) infiltration, lamination and pyrolysis by using carbon nanotubes (CNTs) films as surface layers and carbon foam (CF) as intermediate layer. The SiBCN@CNTs surface layer with high electrical conductivity effectively reflects most of electromagnetic waves, and the SiBCN@CF intermediate layer further increases the absorption of incoming waves via ohmic loss and multiple reflection loss. The construction of the conductive SiBCN@CF layer can effectively enhance the total EMI shielding effectiveness (EMI SE Total ) of the films up to 44.3 dB, much higher than that of 25.8 dB for the sandwiched film with nonconductive intermediate layer. Moreover, increased porosity in the SiBCN@CF layer endows the SiBCN@CF/CNTs film with a high specific EMI SE Total of up to 131.2 dB cm 3 g −1 causes by increased multiple reflection loss. Therefore, it is an ideal route to construct a conductive network and porous structure in sandwiched EMI material for achieving high-efficiency shielding performance.