High‐performance microwave absorbers with special features are desired to meet the requirements of more complex modern service environments, especially corrosive environments. Therefore, high‐efficiency microwave absorbers with corrosion resistance should be developed urgently. Herein, a 3D NiAl‐layered double hydroxide/graphene (NiAl‐LDH/G) composite synthesized by atomic‐layer‐deposition‐assisted in situ growth is presented as an anticorrosive microwave absorber. The content of NiAl‐LDH in the composite is optimized to achieve impedance matching. Furthermore, under the cooperative effects of the interface polarization loss, conduction loss, and 3D porous sandwich‐like structure, the optimal NiAl‐LDH/G shows excellent microwave absorption performance with a minimum reflection loss of −41.5 dB and a maximum effective absorption bandwidth of 4.4 GHz at a loading of only 7 wt% in epoxy. Remarkably, the encapsulation effect of NiAl‐LDH can restrain the galvanic corrosion owing to graphene. The epoxy coating with the NiAl‐LDH/G microwave absorber on carbon steel exhibits long‐term corrosion resistance, owing to the synergetic effect of the superior impermeability of graphene and the chloridion‐capture capacity of the NiAl‐LDH. The NiAl‐LDH/G composite is a promising anticorrosive microwave absorber, and the findings of this study may motivate the development of functional microwave absorbers that meet the demands of anticorrosive performance of coatings.

Although graphene aerogels (GA) have been attracted great attention, the easy-operation and large-scale production of GA are still challenges. Further, most GA have a monolith-like appearance, limiting their application-specific needs. Herein, we highlight graphene aerogel spheres with controllable hollow structures (HGAS) that are delicately designed and manufactured via coaxial electrospinning coupled with freeze-drying and calcination. The HGAS exhibit a spherical configuration at the macroscale, while the construction elements of graphene on the microscale showing an interconnected radial microchannel structure. Further, ball-in-ball graphene aerogel spheres (BGAS) are obtained by reference to the triaxial electrospinning technology. The as-prepared spheres possess the controllable integrated conductive networks, leading to the effective dielectric loss and impedance matching, thus bringing on high-performance microwave absorption. The as-obtained HGAS shows a minimum reflection loss of -52.7 dB, and a broad effective absorption bandwidth (f_E) of 7.0 GHz with thickness of 2.3 mm. Further, the f_E reaches 9.3 GHz for BGAS with thickness of 3.4 mm. Aforementioned superior microwave absorption of HGAS and BGAS confirms combination of multiaxial electrospinning and freeze-drying on the multiscale is an effective strategy for scalable fabrication of advanced microwave absorbing functional graphene aerogel spheres. Open image in new window

This article reviews 3D porous biomass-derived carbon materials as microwave absorbers, including their biomass sources, the transformation from biomass to porous carbon, and their corresponding microwave absorption applications and mechanism.