Mesoporous Hollow Carbon Spheres with Engineered Nanoarchitecture and Tunable Graphitization for Ultra-Broadband Electromagnetic Wave Attenuation

Carbonaceous materials have garnered significant attention as promising candidates for microwave attenuation applications, due to their remarkable dielectric tunability and structural adaptability. Nevertheless, the fundamental mechanisms underlying microwave absorption, along with the persistent challenge of optimizing the balance between conduction and polarization losses, continue to pose critical scientific hurdles. In this study, mesoporous hollow carbon spheres (MHCS) were synthesized using a silica-templated etching-pyrolysis approach. Characterization of their morphology, microstructure, and electromagnetic parameters reveals that the dielectric loss behavior of MHCS can be strategically modulated through synergistic nanoarchitecture engineering and controlled graphitization. Notably, when the carbonization temperature is set at 700 °C, the as-prepared MHCS sample exhibits remarkable microwave absorption performance, achieving a minimum reflection loss (RLmin) of −57.4 dB at a thickness of 2.5 mm and an ultrawide effective absorption bandwidth of 7.5 GHz (RLmin ≤ −10 dB). This superior performance is primarily attributed to the hierarchical porosity, which promotes interfacial charge accumulation, an optimized graphitization degree for impedance matching, and defect-mediated enhancement of dipole polarization. Furthermore, computational simulations reveal that employing this material as a coating on the F-22 “Raptor” fighter jet markedly enhances radar stealth capabilities. These findings highlight the potential for developing lightweight, high-performance stealth coatings with practical applicability in advanced defense technologies.