Fe3Si-core/amorphous-C-shell nanocapsules with enhanced microwave absorption

Nanoscale heterostructures, like core-shell structures, show attractive microwave-absorption characteristics because of the synergetic effects of their dielectric shells and soft-magnetic cores. A new type of nanocapsules with amorphous C shell encapsulating Heusler soft-magnetic Fe₃Si alloy has been designed and synthesized in which Si atoms were doped in the C shell to effectively produce a large amount of Si-C bonds to induce the formation of an amorphous C shell. This further significantly improves the dielectric properties of C shells by enhanced dielectric polarization. These tailored Fe₃Si/C nanocapsules, exhibit enhanced microwave-absorption properties because of the desirable impedance match between the amorphous C shell and the soft-magnetic Fe₃Si. The optimal Fe₃Si/C nanocapsules exhibit a highest absorption intensity of −68.3 dB at 13 GHz and an absorption bandwidth of 4.6 GHz (for RL lower than −10 dB) for absorber thicknesses of 2.1 mm and 1.4 mm, respectively. This new type of nanocapsules is of potential interest for application as novel microwave-absorption material.