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.