Three-dimensional foam-like Fe3O4@C core-shell nanocomposites: Controllable synthesis and wideband electromagnetic wave absorption properties.

• The Fe 3 O 4 @C nanocomposite with a foam-like core-shell structure was first prepared. • The foam-like structure was obtained by solution combustion method. • The efficient EMW absorption (RL ≤ −20 dB) band can reach 14.9 GHz (d = 1.4–5.5 mm). Ferrite and carbon nanocomposites are regarded to be excellent electromagnetic wave absorbers due to their compatible dielectric and magnetic loss capabilities. In this article, the three-dimensional (3D) Fe 3 O 4 @C core-shell nanocomposites with foam-like structure have been successfully prepared, which would greatly promote multiple reflection/scattering of the incident microwave. By adjusting the amount of polymeric precursors, the outer carbon can be perfectly controlled within the average thickness range of 9.1–34.8 nm. Meanwhile, through the synergy between 3D foam-like Fe 3 O 4 core and outer carbon, the impedance matching conditions of the nanocomposites can be improved. Besides, the electromagnetic wave absorptivity of the nanocomposites presents a significant dependence on the thickness of outer carbon. When the average thickness of outer carbon is 28.3 nm, the absorber shows the most excellent performance, and the minimum reflection loss (RL) value is −55.5 dB with 2.5 mm absorber thickness. Especially, when the thickness is tuned from 1.4 mm to 5.5 mm, the Fe 3 O 4 @C exhibits efficient absorption (RL ≤ −20 dB) in an ultra-wide band (14.9 GHz). Based on the amazing microwave absorption properties, this nanocomposite can be considered as an ideal absorber. [ABSTRACT FROM AUTHOR]