Ultra-lightweight hollow bowl-like carbon as microwave absorber owning broad band and low filler loading

With the development of military aircraft equipment and wearable civilian electronic equipment, lightweight is becoming more and more important in the design of absorbing materials. In this work, hollow bowl-like carbon (HBC) materials are controllably constructed by the hard template method, its tunable pore structure, surface properties as well as shell thicknesses lead to the excellent performance. The HBC with shell thickness of 3 nm shows the best wave-absorbing performance at the absorber content of 4%. Its minimum value of reflection loss is −50 dB with at a thin thickness of 2.26 mm, while its effective absorption bandwidth, at a fixed thin thickness of 2 mm, can be as wide as 7.04 GHz (10.96–18 GHz). On the one hand, thin shells are the key to achieve light weight, on the other hand, the bowl-like shape prevents the formation of percolative networks. Percolative behavior analysis demonstrates that with the low mass fraction of absorber content, the HBC materials can obtain the modest dielectric constant and loss, thus achieve good impedance matching and sufficient attenuation capacity. This work provides an effective and sustainable way to utilize porous carbon materials for developing lightweight and high-performance wave-absorbing materials.