FeSn2/defective onion-like carbon core-shell structured nanocapsules for high-frequency microwave absorption

The rapid development of microelectric devices has stimulated the research interest of GHz frequency electromagnetic wave absorbing materials. FeSn2/defective onion-like carbon core-shell structured nanocapsules have been synthesized by an arc-discharge method, in which liquid ethanol works as carbon source. The electromagnetic properties of FeSn2/C nanocapsules (40 wt%)-paraffin composite have been investigated in 2-18 GHz. Three Debye dipolar relaxation processes may exist in FeSn2@C nanocapsules, originating from an integrally dielectric polarization of defective onion-like carbon and FeSn2 nanoparticles and the interfacial polarization between FeSn2 core and C shell. FeSn2@C nanocapsules present resonant dielectric loss and antiresonant magnetic loss in 12-18 GHz, revealing energy transform from the permeability to permittivity. Based on a transmission line theory, more than 90% of the electromagnetic power can be attenuated at 2-18 GHz when an appropriate absorber thickness between 1.6 and 10.0 mm is chosen. Impedance matching and the EM wave attenuation in the interior of the absorber are used to understand the good EM performance. The good performances are ascribed to the defective onion-like carbon shell, the interface between core and shell and the desirable impedance match. (C) 2016 Elsevier B.V. All rights reserved.