Tunable design of yolk-shell ZnFe2O4@C composites for enhancing electromagnetic wave absorption

This study shows a simple, layer-by-layer coating process and low-temperature chemical etching method for selective preparation of yolk-shell ZnFe2O4@C composites by using SiO2 as the template. Compared with core-shell ZnFe2O4@SiO2@C, the yolk-shell ZnFe2O4@C microspheres exhibited significantly enhanced electromagnetic wave (EMW) absorption performance in terms of effective bandwidth, coating thickness and minimum reflection loss. The void size can be adjusted just by changing volume of added TEOS, obtaining a series of yolk-shell ZnFe2O4@C composites. It was demonstrated that the Y-2 composite was second to none and its RLmin can drop as low as -37.1 dB at the thickness of 1.4 mm. Besides, its effective bandwidth (RL <= -10 dB, 90% absorption) can cover the whole frequency range of 3.8 GHz. Hence, changing void size can reach the best impedance match and tune the EMW absorption performance of samples, which makes yolk-shell ZnFe2O4@C composites be widely used in civil and military fields. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrates a simple layer-by-layer coating process and low-temperature chemical etching method to selectively prepare yolk-shell ZnFe2O4@C composites, showing significantly enhanced electromagnetic wave absorption performance. The void size can be adjusted to tune the performance of the composites.