Iron-cobalt-graphite core-shell nanoparticles as efficient electromagnetic wave absorbers at X-band frequency range

In this reported work, FeCo@C core-shell nanoparticles were synthesised using a novel two-step process. Characterisation of samples confirms the formation of graphite-coated FeCo nanoparticles. The electromagnetic wave absorption of nanocomposites containing 40%wt of FeCo@C and FeCo nanoparticles in the paraffin matrix was measured at 8-12.4 GHz frequency range. Two samples were prepared with thickness of 9 mm for FeCo and FeCo@C nanoparticles, respectively. Then the reflection loss was measured at ten different thicknesses between 9 and 1.4 mm by slicing the samples and measuring the scattering parameter S₁₁ for each sample thickness using a metal backing. Results show that by graphite coating of FeCo nanoparticles the maximum reflection loss (-5.5 dB) grows up to four times higher (-19.2 dB) and the corresponding thickness reduces to half. The reason lies in active dielectric-magnetic loss mechanisms in FeCo@C nanoparticles.