Facile synthesis of Mn3O4 hollow polyhedron wrapped by multiwalled carbon nanotubes as a high-efficiency microwave absorber

Investigating lightweight and high-efficiency electromagnetic wave (EM) absorbers is evolving as a desirable approach to solve the electromagnetic pollution. In this study, Mn3O4 hollow polyhedron wrapped by multiwalled carbon nanotubes (Mn3O4/MWCNTs) was successfully prepared by one-step hydrothermal treatment. Interestingly, the Mn3O4 polyhedron as a unique hollow structure can serve as a microwave receiver and the incident EM waves hardly escape in the intricate networks, which could be repetitiously attenuated and consumed. The Mn3O4/MWCNTs composite with a filler loading of 20 wt% exhibits most outstanding EM absorption performance over the whole frequency of 2-18 GHz. The optimal reflection loss (R (L)) achieves - 53.8 dB at 11 GHz, and the effective absorption bandwidth (R-L exceeding -10 dB) reaches 4.1 GHz (9.1-13.2 GHz) with a thickness of 2.5 mm. The effective absorption bandwidth (R-L < -10 dB) up to 13.7 GHz (85% absorption over 2-18 GHz) was achieved by adjusting the thickness from 1.5 to 4 mm. The remarkable EM absorption performances benefit from the synergistic effects of suitable impedance matching, dielectric loss, interfacial polarizations and relaxation polarizations. These results indicate that Mn3O4/MWCNTs composite with lightweight and high-efficiency microwave absorption properties could serve as a prospective microwave absorber in practical applications.