Hollow SiC@MnO2 nanospheres with tunable core size and shell thickness for excellent electromagnetic wave absorption

The hollow microstructure can permit more incident waves to enter the absorber and increase the attenuation ability by multiple reflections and diffraction. In addition, different substances can introduce the heterogeneous interface and further attenuate electromagnetic waves through interfacial polarisation relaxation. Here, hollow SiC@MnO2 nanospheres are synthesised with tunable hollow SiC core size and flower-like layered MnO2 shell thickness. By adjusting the concentration of KMnO4, different shell thicknesses of hollow SiC@MnO2 nanospheres can be prepared, ranging from 40 nm to 110 nm. Furthermore, hollow SiC@MnO2 composites with different inner diameters between 300 nm and 470 nm can be obtained by tailoring the amount of tetraethyl orthosilicate. The results indicate that the effective absorbing bandwidth of hollow SiC@MnO2 can reach 5.71 GHz with a core size of 360 nm and a shell thickness of 90 nm at only 1.8 mm. This work provides a valuable core–shell strategy of hollow SiC@MnO2 towards excellent electromagnetic wave-absorbing properties.