Effect of Copper Sulfide Nanosphere Shell on Microstructure and Microwave Absorption Properties of Carbon Nanotube@Cobalt Ferrite Composites

Copper sulfide/cobalt ferrite/multi-walled carbon nanotube (CuS/CoFe2O4/MWCNT) microwave absorbing composites were prepared using a one-step hydrothermal method. The MWCNTs serve as skeletons with small CoFe2O4 spheres and CuS nanoparticles attached to the surface, developing a tube-sphere microstructure. We observed that CoFe2O4 connects MWCNTs and CuS by forming the C-O and S-O covalent bonds, respectively. CuS plays an important role in the adjustment of electromagnetic parameters, i.e., increasing the electromagnetic wave attenuation capacity and decreasing the characteristic impedance. The optimized composite exhibits good microwave absorption properties with a maximum microwave absorption bandwidth of 5.26 GHz at the matching thickness of 1.77 mm. In particular, the minimum reflection loss of the composite can reach − 58.74 dB at 17.52 GHz with the matching thickness of 4.64 mm, showing a great application prospect in the field of high-frequency electromagnetic wave absorption, e.g., in the Ku band range. The theoretical calculations demonstrate that the electronic structure of the material has changed in the presence of CuS. The energy barrier for electron transfer is reduced, promoting the formation of a specific charge transfer channel, which strengthens the microwave absorption properties of the composites.