Strengthened electromagnetic absorption performance derived from synergistic effect of carbon nanotube hybrid with Co@C beads

The composite structure of Co beads (200–300 nm) threaded by carbon nanotubes has been synthesized through a facile solvothermal method followed by a carbon reduction process. A carbon layer of ca. 5 nm was coated on the surface of Co beads to form a core-shell structure (CNTs/Co@C), in favor of the anti-oxidation of Co nanoparticles. The CNTs/Co@C hybrid showed a saturation magnetization (M s) of 82.5 emu g−1 and a larger H c value of 258.8 Oe than bulk Co (ca. 10 Oe). Served as an EM wave absorption material, the epoxy resin composites consisting of 60 wt% and 40 wt% CNTs/Co@C hybrid exhibited effective EM absorption (RL < − 10 dB) over the frequency ranges of 1.5–15 and 1.6–20 GHz with the matching thicknesses of 1.0–7.5 and 1.0–10.0 mm, respectively. The superior EM absorption performances of CNTs/Co@C hybrid containing strong absorption, wide frequency range, thin thickness, and light weight are mainly attributed to the synergy of magnetic loss from Co beads and dielectric loss from carbon nanotubes, as well as remarkable impedance matching.