Achieving absorption-type electromagnetic shielding performance in silver micro-tubes/barium Ferrites/Poly(lactic acid) composites via enhancing impedance matching and electric-magnetic synergism

High conductivity can give materials excellent electromagnetic shielding performance, but it leads to serious impedance mismatching and causes inevitable secondary pollution. Developing materials with both excellent microwave absorption and microwave shielding performance remains a formidable challenge. Herein, absorption-type electromagnetic shielding materials with high electromagnetic shielding effectiveness (EMW SE) values were successfully prepared by combining hollow silver micro-tubes and magnetic nano-barium ferrites. The electromagnetic parameters and impedance matching of the composites could be easily regulated by changing the ratio of silver micro-tubes (C) and nano-barium ferrites (M). Thanks to micro-tube structure and the electric-magnetic synergism of the fillers, the composites with the C:M ratio of 9:1 exhibited a high absorption coefficient (A) value of-0.77 and a high EMW SE value of-100 dB, simultaneously. The absorption-type shielding mechanism of the composites was also evaluated via discussing real and imaginary parts of complex permittivity, real and imaginary parts of complex permeability, and Cole-Cole curves. Furthermore, the com-posites with the C:M ratio of 3:7 exhibited excellent microwave adsorption performance with the minimum reflection loss of-46.3 dB at thickness of 3.0 mm and a maximum effective absorption band-width of 6.13 GHz.