Carbon nanofiber aerogel/silicon oxycarbide composites for enhanced electromagnetic interference shielding

Lightweight electromagnetic interference (EMI) shielding materials under harsh environments are in urgent need to tackle the increasing electromagnetic pollution and hazards. Herein, carbon nanofiber aerogel (CNFA) modified silicon oxycarbide (CNFA/SiOC) composites were prepared following a precursor infiltration pyrolysis procedure by using three-dimensional CNFA as a skeleton. Their structures and mass densities (0.28-1.35 g cm−3) were tunable by adjusting the content of polysiloxane precursor in impregnating solution. The lightweight CNFA/SiOC composite featured with continuous conductive network and highly porous structure in SiOC matrix, resulting in high specific shielding effectiveness (up to 68.9 dB·cm3 g−1 with SETotal of 19.3 dB) due to enhanced conductance loss and multi reflection/scattering. When increasing the density, the CNFA/SiOC composite can deliver EMI shielding effectiveness as high as 27.5 dB due to the generation of defective carbon and carbon dangling bonds as well as abundant interfaces between CNFs and SiOC which induce polarization loss. Moreover, the CNFA/SiOC composite exhibits good oxidation resistance with SETotal retention of above 98% after heat treatment at 600°C for 2 h in air, which arises from the effective protection of CNFs by SiOC.