Graphene Shield by SiBCN Ceramic: A Promising High-Temperature Electromagnetic Wave-Absorbing Material with Oxidation Resistance.

As cutting-edge emerging electromagnetic (EM) wave-absorbing materials, the Achilles' heel of graphenes is vulnerable to oxidation under high temperature and oxygen atmosphere, particularly at temperatures more than 600 °C. Herein, a graphene@Fe3O4/siliconboron carbonitride (SiBCN) nanocomplex with a hierarchical A/B/C structure, in which SiBCN serves as a "shield" to protect graphene@Fe3O4 from undergoing high-temperature oxidation, was designed and tuned by polymer-derived ceramic route. The nanocomplexes are stable even at 1100-1400 °C in either argon or air atmosphere. Their minimum reflection coefficient (RCmin) and effective absorption bandwidth (EAB) are -43.78 dB and 3.4 GHz at ambient temperature, respectively. After oxidation at 600 °C, they exhibit much better EM wave absorption, where the RCmin decreases to -66.21 dB and EAB increases to 3.69 GHz in X-band. At a high temperature of 600 °C, they also possess excellent and promising EW wave absorption, for which EAB is 3.93 GHz, covering 93.6% range of X-band. In comparison to previous works on graphenes, either the EAB or the RCmin of these nanocomplexes is excellent at high-temperature oxidation. This novel nanomaterial technology may shed light on the downstream applications of graphenes in EM-wave-absorbing devices and smart structures worked in harsh environments.