  We demonstrate that polymer composites with a low loading of graphene, below
1.2 wt. %, are efficient as electromagnetic absorbers in the THz frequency
range. The epoxy-based graphene composites were tested at frequencies from 0.25
THz to 4 THz, revealing total shielding effectiveness of 85 dB (1 mm thickness)
with graphene loading of 1.2 wt. % at the frequency f=1.6 THz. The THz
radiation is mostly blocked by absorption rather than reflection. The
efficiency of the THz radiation shielding by the lightweight, electrically
insulating composites, increases with increasing frequency. Our results suggest
that even the thin-film or spray coatings of graphene composites with thickness
in the few-hundred-micrometer range can be sufficient for blocking THz
radiation in many practical applications.
