Efficient broadband electromagnetic wave absorption of flower-like nickel/carbon composites in 2–40 GHz

Flower-like assemblies of nickel/carbon (Nix/C) microspheres (MSs) with Ni-O-C bond and “double-layer” carbon shells have been successfully prepared through a solvothermal route and a sintering process combined with carbon reduction. The electromagnetic wave absorption (EMWA) properties of MSs can be tuned by controlling the Ni content. The Ni2.0/C composite exhibits superior EMWA properties: the reflection loss (RL) can be up to −47.5 dB (34.6 GHz) and the efficient absorption bandwidth (RL < −10 dB) is 37.04 GHz (2.96–40 GHz) via adjusting the thickness from 1 to 5.5 mm. The outstanding EMWA properties can be benefitted from the synergistic effects of carbon with dielectric loss, Ni particles with magnetic loss and hierarchically porous structures.