Collective orientation of CNT coated magnetic microchains for effective microwave absorption in S and C band

The control of undesired electromagnetic radiation in S- and C-band spectra requires novel microwave absorbing materials (MAMs) having high microwave attenuation capability together with optimal impedance matching. CNTs are conformally coated onto the surface of one-dimensional FeCo-based magnetic microchains via electrostatic self-assembly, and then the magnetic inclusions are collectively oriented in matrices by applying an external magnetic field. The proper incorporation of CNTs with magnetic microchains demonstrates a feasible pathway for effectively absorbing microwaves in the S and C band. MAMs consisting of oriented microchains have anisotropic complex permittivity, of which the real part ranges from 6.1 to 30.4 at 2 GHz. When the electric field is parallel to microchains, the 5-mm-thick MAM has an effective absorbing bandwidth (EAB) in the range of 2.3 to 2.9 GHz, and reduces the radar cross section to be lower than ‒15.9 dB m2 from the vertical to the glancing incidence. When the magnetic field is parallel to microchains, the MAM adsorbs C-band microwaves with an EAB of 1.5 GHz, and achieves maximal reflection loss of ‒46.4 dB. The collective orientation of shape-anisotropic magnetic materials, in addition to the composition and microstructure, is a new variable for the design of effective MAMs.