Electromagnetic interference shielding effectiveness of carbon foam containing in situ grown silicon carbide nanowires

Electromagnetic interference (EMI) shielding effectiveness of the carbon foam containing different amounts of silicon carbide nanowires (SiC NWs) was determined over X-band (8.2-12.4 GHz). Carbon foam was prepared from powdered precursors containing polyurethane, novolac and pitch. In situ SiC NWs were grown inside the porous body by using different weight ratios of silicon powder ranging from zero to 20 wt% and pyrolyzing at 1500 °C under argon atmosphere. Decorated nanowires led to a different cellular structure compared to pristine carbon foam and improved the absorptivity of EM radiations due to a very high level of dielectric loss (loss tangent of 3.1 at 12.4 GHz). A maximum EMI specific shielding effectiveness of ~79.50 dB cm³/g (at 8.2 GHz) was achieved in the carbon foam containing the highest amount of SiC NWs, which was more than two times higher than that of the pristine carbon foam. Presence of NWs with stacking faults, heterostructure interfaces and long tortuous paths in the carbon foam caused a strong dielectric loss and induced higher dielectric permittivity. The study shows that by controlling the amount of SiC NWs, it is possible to improve multiple properties while achieving lightweight material for stealth technology.