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.