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

Lightweight electromagnetic-interference (EMI)-shielding materials are urgently needed in harsh environments 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/cm³) were tunable by adjusting the content of the polysiloxane precursor in the impregnating solution. The lightweight CNFA/SiOC composite featured a continuous conductive network and a highly porous structure in the SiOC matrix, resulting in high specific shielding effectiveness (SE) (up to 68.9 dB cm³/g with SE_total of 19.3 dB) due to enhanced conductance loss and multi-reflection/scattering. When the density is increased, the CNFA/SiOC composite can deliver EMI SE as high as 27.5 dB due to the generation of defective carbon and carbon dangling bonds as well as abundant interfaces between carbon nanofibers (CNFs) and SiOC, which induce polarization loss. Moreover, the CNFA/SiOC composite exhibits good oxidation resistance with SE_total 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.