Carbon foam decorated with silver particles and in situ grown nanowires for effective electromagnetic interference shielding

Carbon foam filled with silver particles was fabricated by a powder molding process using polyurethane as pore former, novolac resin as binder, coal-tar pitch as densification additive, and silver foils as a filler. High-temperature treatment at 1200 degrees C, transformed the silver into spherical particles covered with in situ grown Ag nanowires. Their microstructure, electromagnetic interference (EMI) shielding effectiveness (SE), and shielding mechanism was investigated. It was found that the micron-sized silver foils converted into particles during heat treatment and strongly bonded in carbon matrix. The addition of silver significantly enhanced both conductivity and SE. Carbon foam containing 1.5 wt% silver exhibited very impressive total SE and dielectric loss tangent owing to the more conductive network of silver particles providing fast electron-transport channels. A maximum specific EMI SE value of 58.21 dB g(-1) cm(3) at 12 GHz was achieved in the carbon foam at 1.5 wt% Ag loading. The dominant mechanism was absorption with only 6-10 % reflectance, resulting from the multiple reflections at interfaces inside the foam. Due to controlled attachment of silver particles and in situ reactions, this novel substrate has unique opportunities for future surface tailoring required in various commercial and aerospace fields.