Shielding properties of carbon nanotubes - amorphous composite coatings

An electric conductive and magnetic permeable composite coating with different mass fractions of multiwalled carbon nanotubes (MWCNTs) and cobalt-base amorphous powder was synthesized for wide frequency electromagnetic interference (EMI) shielding. The results of measurement on surface resistivity and shielding effectiveness (SE) showed that the system percolation threshold is near 40 wt% of MWCNTS and 30 wt% Of amorphous powder. At this point, surface resistivity is minimum and SE is almost higher than 10 dB in the frequencies ranging 100 kHz-1.5 GHz. From SEM image of coating, it is found that fillers of coating are dispersed well. The amorphous powder of high permeability can improve the low frequency shielding effect of the coating significantly and thus obtained SE is better than that of traditional shielding coatings in low frequency band. Owing to its light weight, low filler concentration and easy processability, the composite coating can promisingly be used as an effective and practical wide frequency EMI shielding material.