Carbon-based cages with hollow confined structures for efficient microwave absorption: State of the art and prospects

The design of lightweight and efficient electromagnetic wave absorbing materials (EWAMs) is of great significance in the fields of information security and the target stealth. Recently, hollow carbon-based confined structures have been widely concerned due to some unique characteristics of the electromagnetic wave absorption process. First, Hollow structures with resonant cavity characteristics facilitate electromagnetic wave scattering and endow structures with multimode resonance properties. Second, a hollow structure is beneficial to reduce its bulk density and complex permittivity, and its unique confined structure can be used as a “storehouse” for storing air to optimize the impedance matching characteristics of the EWAM. In this paper, the recent research progress on carbon-based hollow EWAMs has been profoundly reviewed, including the categories of pure carbon EWAMs and carbon-based composites, design strategies, synthetic methods, and the structure-function relationship of EWAMs. Finally, the challenges, and prospects for practical applications of hollow carbon-based structures are also discussed. We believe that this critical review is timely and not only highlights the recent advances and advantages of the carbon-based EWAMs, but also inspires new concepts for designing hollow-structure absorbers.