Chiral Asymmetric Polarizations Generated by Bioinspired Helical Carbon Fibers to Induce Broadband Microwave Absorption and Multispectral Photonic Manipulation

Abstract

as stealth systems, [1] electromagnetic pollu tion eradicators, [2] and various electronic and communicational devices, [3] etc. [4] Broadband absorption is key factor of MAMs, which derived from two types of materials: [5] dielectric loss materials (graphene, [6] carbon nanotubes, [7] biomass carbon materials, [8] conductive polymer, [9] ZnO, [10] MnO 2 , [11] etc.) and magnetic loss materials (ferrite, [12] carbonyl iron, [13] high entropy alloys, [14] and other ferromagnetic alloys [15] ). Previous studies have demonstrated that MAMs with both dielectric loss (permittivity) and magnetic loss (permeability) were more easily to achieve good impedance match and thus broadband absorption. [16] Common method for fabricating mentioned electromagnetic complexes was mixing dielectric and magnetic matters, the carbonyl iron/carbon nanotubes composite absorbers could exhibit double resonance of the complex permittivity and permeability, thus reach effective absorption (reflection loss (RL) ≤ −10 dB) within 9.7-18 GHz regime under 1.4 mm thickness. [17] However, such addition of ferromagnetic materials brings some disadvantages such as high density and easy oxidation. The mentioned drawback could be avoid by some complicated synthetic method such as doping ferromagnetic ions in dielectric materials, [3] or preparing metal-organic frameworks (MOFs). [18] In addition to the intrinsic parameters of materials, metastructures [19] and microstructures [20] could give MAMs new design freedoms to broad absorption bandwidth. Metastructures can give MAMs additional effect to form metamaterials, [21] which could improve the absorption bandwidth by constructing equivalent circuit models, [22] vortex current loss, [23] overlapped reflections, [24] and polarization rotation, [25] etc., a metamaterial with square unit cells made of carbon black can achieve absorption bandwidth that 2.35-18 GHz (absorptivity more than 96.8%) under thickness of 17 mm, [26] our previous works brought optical rotation of chiral metamaterials based on high entropy alloys to consume microwaves, the effective absorption bandwidth (RL ≤ −10 dB) covered 4-5.54, 6.66-8.12, and 8.84-18 GHz under 20 mm thickness. [27] Whereas the thickness of metamaterials has to close to wavelength, because the loss effects of metamaterials are generated by subwavelength resonance that based on wave theory, thus difficult to broadband Chirality, in which electromagnetic characteristic promotes asymmetric polarization, is expected to realize broadband absorption for microwave absorption materials (MAMs). Herein, inspired by the microstructure of nepenthes, a scalable approach is reported for fabricating hierarchical-chiral helical carbon fibers with broadband microwave absorption as well as multispectral chiral manipulation. The chiral potential barriers are established by applying helically distributed stress to the fiber, which induce helical electric dipoles via positive and negative charges accumulated at the potential barriers. The states of polarization loss by Debye relaxat...

Carbon Nanocoils/Carbon Foam as the Dynamically Frequency‐Tunable Microwave Absorbers with an Ultrawide Tuning Range and Absorption Bandwidth

“…[17] Owing to the chiral parameter, the strong current density at the helix of CNCs may favorably affect the microwave attenuation behavior (Figure S28, Supporting Information). [17,18] When EM waves pass through CNCs, cross-polarization is induced, resulting in the electrical and magnetic coupling that helps widen the frequency tuning range and absorption bandwidth. In consequence, to intuitively affirm the effect of different compression states in attenuating microwaves, the current density of CNCs/ CF-2 is simulated by COMSOL Multiphysics.…”

“…characteristics are ferreted out and can be classified into broad categories as dielectric loss materials, [11][12][13] magnetic loss material, [14][15][16] chiral materials, [17][18][19] and metamaterials. [20,21] Thereinto, some material systems with ingenious designs have nearly satisfied the high-specification using needs, namely thin coating, light weight, wide bandwidth, and strong absorption.…”

Structure–Activity Relationship in Microstructure Design for Electromagnetic Wave Absorption Applications

“…The effective absorption bandwidth (EAB) of the chiral carbon fiber can reach 9.2 GHz. [30] Compared to traditional MAMs, structurally designed absorbing materials offer flexibility in controlling over EM wave absorption, enabling functionality such as multiband absorption, wide-band absorption, and polarization insensitivity. Furthermore, structurally designed absorbing materials allow for ultra-thin and lightweight designs, minimizing the impact on the carrier's performance while enhancing stealth capabilities.…”

Thin layers of microwave absorbing metamaterials with carbon fibers and FeSi alloy ribbons to enhance the absorption properties

“…The broad-bandwidth and strong absorbers of microwave have applications in satellite communications [1,2], stealth [3], eliminating electromagnetic pollutions [4], etc. A lot of microwave absorbing material were developed to achieve broadband absorption by researchers [5], the absorbers according to the mechanism of loss can be classified as dielectric loss and magnetic loss material [6][7][8], the dielectric loss of materials including graphene [9][10][11], carbon nanotubes [12,13], carbon fiber [14], manganese dioxide [15], etc., magnetic loss materials mainly include carbonyl iron [16,17], ferrite [18], iron alloy [19], high entropy alloys [20] and so on. Most of the previous studies combined these two types of materials to improve impedance matching and achieve broadband absorption.…”