▎ 摘　　要

To meet the demand for accurate shielding of stealth aerospace, a tunable and high performance electromagnetic (EM) absorber based on unidirectional graphene foams (UGFs) is demonstrated in this work. Taking advantage of anisotropic design, a highly porous structure with long-range alignment has been pertinently constructed and the EM absorption performance was investigated in 2-18 GHz as a function of the intersection angle 4 between the aligned direction and polarized direction of incident EM wave. By in-plane rotating the samples, it was suggested that both the reflection loss (R-L) and peak frequency of UGFs were readily tunable. The specific regularities were closely related to the thermal reduction degree determined by annealing temperature. A dual-absorption mechanism arising from dielectric loss and induced current was also proposed, through which the tunable absorption was attributed to variation of coupling alignment between aligned structure and their directionalities upon the fields of EM wave. Particularly at the optimal alignment, a maximum R L up to -65 dB has been obtained, which is the highest value for all the graphene based EM absorption materials. Besides, owing to the dual absorption feature, a qualified bandwidth of 10.9 GHz was also achieved. (C) 2018 Elsevier Ltd. All rights reserved.