Yolk-shelled Co@SiO@Mesoporous carbon microspheres: Construction of multiple heterogeneous interfaces for wide-bandwidth microwave absorption.

Nowadays, in the practical application of microwave absorption, it is still urgent and challenging to develop the microwave absorber with broadened bandwidth at a single thickness. Constructing composites with multi-component and multi-structure has been an effective strategy to obtain enhanced microwave absorption performance. Herein, yolk-shelled Co@SiO@Mesoporous carbon (Co@SiO@MC) microspheres were prepared by in-situ one-pot synthesis, carbonization reduction, and subsequent etching. The mesoporous carbon shell and hollow cavity structure were obtained simultaneously by controlling the etching of SiO. The large carbon-air interface in the mesoporous shell and interior voids extend the propagation path of electromagnetic wave and enhance scattering. Owing to strong dielectric/magnetic loss, synergistic effect between different components and microstructures, as well as excellent impedance matching, Co@SiO@MC microspheres exhibit desirable microwave absorption performance. Notably, for the sample with mesoporous carbon shell thickness of 25 nm, the effective absorption bandwidth (reflection loss below -10 dB) is as wide as 9.6 GHz (8.4-18 GHz), completely covering the whole X and Ku bands at 3.7 mm. The ultra-wide absorption bandwidth of the yolk-shelled Co@SiO@MC microspheres highlight their potential application in the field of microwave absorption. Furthermore, this work provides new insights for the preparation of multi-component/multi-structure microwave absorbers.