Reduced graphene oxide@carbon sphere based metacomposites for temperature-insensitive and efficient microwave absorption

With the increasing advance of fifth generation (5G) network and the gradual expansion of digital devices, harsh working environment for electronic devices has spawned higher requirements for microwave absorbing materials (MAMs). Since both the electromagnetic response and energy conversion character vary with temperature, to achieve temperature insensitive microwave absorption behaviour in wide temperature range has become extremely challenging. In this work, structured metacomposites containing sub-wavelength reduced graphene oxide (RGO)@carbon spheres were fabricated, and the microwave absorption was further improved through structural and composition design of the RGO@carbon units. Due to the unique anti-reflection effect on microwave of the metacomposites, the temperature-insensitive electromagnetic performance at elevated temperature could be exhibited. Moreover, both the dielectric relaxation behaviour and microwave absorption proformance of the system could be further increased. As a result, the effective absorption bandwidth (reflection loss (RL) < -10 dB) of the metacomposites with only 3.0 wt.% filler content could cover the entire X-band (8.2-12.4 GHz) frequency ranging from 298 to 473K. The metacomposite proposed in this work provides a "de-correlating" strategy to break the linkage between microwave absorption behaviour and temperature, which offers an interesting plateau for fabricating efficient high-temperature microwave absorption structures with tunable and designable advantages.