EMI shielding effectiveness of silver nanoparticle-decorated multi-walled carbon nanotube sheets

With the aim of exploring the excellent properties of multi-walled carbon nanotubes (MWNTs) in modern composite technologies, various macrostructures of nanotubes have been developed from one to three dimensions, e.g. fibers, networks, sheets (buckypapers) and pellets. The MWNT sheets discussed here were fabricated by a vacuum filtration procedure, a process that has potential for large-scale manufacturing. In order to further enhance the transport properties of MWNT sheets by reducing the contact resistance between nanotubes, highly conductive silver nanoparticles were introduced by an in situ photochemical reduction method. TEM analysis showed that highly acid-treated MWNTs dispersed in the presence of Triton X-100 (TX-100) under UV light was a controllable processing method for preparation of a narrow size distribution of silver nanoparticles that were anchored onto the nanotubes. The free-standing MWNT/Ag nanohybrid sheets possessed a sharp increase in electrical conductivity from 27.7 to 40.0 S/cm, which consequently led to a much improved electromagnetic interference shielding effectiveness (SE). In principle, the SE could reach 3500 dB/cm with a thickness of 110 μm, which matched the experimental results well. In addition, the nanohybrid sheets are robust and can be folded with a thickness of 30 μm, which opens a promising way to integrate MWNT sheets into conventional composite laminates.