Combustion-Assisted construction of Defect-Enriched hierarchical carbon composites towards efficient Low-Frequency electromagnetic wave absorption

Due to the high intrinsic conductivity of graphitized carbon-based composite materials, it induces a serious skin effect of incident electromagnetic waves, which deteriorates impedance matching and limits the wave absorption performance in the low-frequency regions. The introduction of defects can change the electrical and physical and chemical properties of carbon-based materials, affect the density of skin current, and thereby improve the overall performance of carbon-based absorbers. Therefore, it is important to develop a simple, low-cost, and fast preparation method for defect-rich structures. Herein, the defect-enriched hierarchical composites have been synthesized successfully via the soaking-burning-annealing process. The combustion treatment introduced numerous defects and oxygen vacancies while inducing a non-graphitization transition that reduced conductivity and improved electromagnetic balance in the low-frequency region. As expected, the charred sample exhibited notable enhancements in reflection loss (RL) and the effective absorption bandwidth within the low-frequency range of 2–8 GHz. The value of RL reached −52.2 dB, marking a 199 % increase over the unburned sample, while the effective absorption bandwidth increased by 28 % to 2.70 GHz. Even at a filling rate of only 10 %, the RLmin values of the optimal sample were lower than −30 dB across the S, C, X, and Ku bands. Additionally, the combination-induced defects led to phonon scattering, thereby reducing the thermal conductivity of the material. Thus, combustion can enhance the low-frequency microwave properties and thermal insulation of carbon-layered composites.