An angle-insensitive electromagnetic absorber enabling a wideband absorption

Abstract

· This work shows the relationship between the orientation of micro-/nanostructures of the EM absorbers and the associated EM parameters. · A mechanism to describe the underlying mechanism behind the EM incident angle sensitivity of the EM absorbers is proposed in this work. · The proposed mechanism guided the development of a novel class of EM absorbers with wide-angle, high-performance EM absorption. · A graphitized carbon nanospheres derived from bamboo exhibit angle-insensitive and wideband EM absorption performance with an effective absorption band up to 3.5 GHz under a thickness of 1.4 mm only. Electromagnetic (EM) wave absorbers with wideband absorption capability are proposed as a strategy to mitigate environmental pollution by EM waves. However, designing an EM absorber with its performance capacity independent of the EM wave incident angle remains elusive to date. Resolving this challenge requires development of EM absorbers whose EM absorption performance is insensitive to the EM wave incident angle. Herein, we synthesized EM absorbers with a variety of structures with different symmetries (including micro-/nanospheres, nanoflakes and nanotubes) to study the effect of the EM absorbers' structure and the EM wave incident angle on the EM absorption performance. Our analysis reveals that non-magnetic EM absorbers with spatially symmetric nanostructures exhibit excellent EM wave incident angle-insensitivity. Finally, we demonstrate that a class of non-magnetic EM absorbers made from bamboo derived-carbon nanospheres exhibit EM incident angle-insensitivity and wideband EM absorption performance with an effective absorption band up to 3.5 GHz when the thickness is 1.4 mm, a significant improvement from prior studies which used thicknesses as high as 3–4 mm for comparable EM absorption performance.