2.5 D carbon/carbon composites modified by in situ grown hafnium carbide nanowires for enhanced electromagnetic shielding properties and oxidation resistance

Hafnium carbide nanowires (HfCnw) were in-situ grown in 2.5 D needle-punched carbon felts by a catalyst-assisted chemical vapor deposition method. Subsequently, the carbon felts were densifled to obtain HfCnw reinforced carbon/carbon (HfCnw-C/C) composites via chemical vapor infiltration. Effects of HfCnw on electrical conductivity, electromagnetic shielding properties and oxidation resistance of C/C composites were investigated for the first time. The results show that the SET of C/C composites with 1.75 wt % HfCnw exceeds 40 dB in the whole frequency range of 8.2-12.4 GHz, implying more than 99.99% of the incident beam was shielded. Moreover, it is found that the relative magnitude relationship of the total shielding effectiveness of composites (SEr(s-2h) > SEr(s-ah) > SEr(s-0h)) is similar with the conductance (sigma(S-2h) > sigma(S-3h) > sigma(S-0h)), which indicates the conductance can effectively predict the relative magnitude of the SET. In addition, the analysis based on oxidation curves demonstrates that HfCnw significantly enhance the oxidation resistance of the composites even with a small amount of HfCnw. The high electromagnetic interference (EMI) shielding effectiveness coupled with relatively low density and good oxidation resistance of HfCnw-C/C composites make itself exhibit remarkable potential as light-weight and high-performance structural-functional integrated materials for future EMI shielding application. (C) 2020 Elsevier Ltd. All rights reserved.