Multi‐Scale Design of Ultra‐Broadband Microwave Metamaterial Absorber Based on Hollow Carbon/MXene/Mo₂C Microtube

Abstract

of single-layered structures. Because the electromagnetic parameters of the lossy material are constrained by the Kramers-Kronig relationship, the effective absorption bandwidth (EAB) of the single-layered microwave absorbers is restricted, and it is difficult to achieve ultra-broadband absorption from several GHz to several tens of GHz. [8,9] Generally, microwave absorbing materials mainly dissipate electromagnetic wave energy through dielectric loss and magnetic loss. Due to the dependence of resonance thickness, the influence of adjusting the loss ability of single-layered absorbing materials on improving the absorbing bandwidth is limited. [10,11] The absorption bandwidth of the absorber can be effectively widened through structural design such as circuit-analog laminate, 2D frequency selective surface, and 3D metasurface. [12][13][14][15] Among them, the 3D metasurface absorbers which feature a periodic array of sub-wavelength structures have been proven to advantage in achieving broadband absorption at a thin thickness. [16][17][18] The complex geometry of the 3D spatial structure can generate multiple resonance absorption peaks in different frequency bands, and meanwhile distort the electromagnetic field nearby its surface and cause strong resonance and diffraction effects, thereby enhancing the dissipation of electromagnetic waves. [19,20] It should be noted that in order to cover the lowfrequency range, magnetic components are usually introduced into the composites to adjust the wave impedance and increase the loss ability. [21,22] The absolute dielectric loss material without the addition of magnetic components is considered difficult to achieve ultra-broadband absorption at a low thickness.In our previous study, it was found that the broadband absorption of X-band and Ku-band can be achieved by converting the 2D microwave absorbing material Ti 3 C 2 T x MXene nanosheets into a 1D microrod structure. [23,24] Herein, through the multi-scale design from the microscopic composite structure to the macroscopic 3D metasurface, a thin-thickness microwave metamaterial absorber (MMA) based on pure dielectric loss substance composed of hollow carbon/MXene/Mo 2 C (HCMM) microtube is proposed. As shown in Figure 1, the specific design route mainly contains three steps: first, by employing polyethylene terephthalate (PET) non-woven fabric as the substrate, the hierarchical HCMM microtube with a micron-scale cavity is fabricated via a self-assembly method and subsequent heat Developing various nanocomposite microwave absorbers is a crucial means to address the issue of electromagnetic pollution, but remains a challenge in satisfying broadband absorption at low thickness with dielectric loss materials. Herein, an ultra-broadband microwave metamaterial absorber (MMA) based on hollow carbon/MXene/Mo 2 C (HCMM) is fabricated by a multiscale design strategy. The microscopic 1D hierarchical microtube structure of HCMM contributes to break through the limit of thickness, exhibiting a strong reflection loss of -66.30 dB (99....

Constructing interfacial polarization sites within a honeycomb-like porous structureviaa spatially confined-etching strategy for boosting electromagnetic wave absorption

“…36 These analyses further indicate that Mo 2 C and C are successful combined and N element is successful doped, resulting in multiple heterointerfaces that can trigger multiple polarization relaxation to promote electromagnetic dissipation ability. 35 The EMW absorption performance is evaluated by using reection loss (RL) and effective absorption bandwidth (EAB), which are calculated according to transmission line theory as follows: [37][38][39] RL ¼ 20 log…”

“…The EMW absorption performance is evaluated by using reflection loss (RL) and effective absorption bandwidth (EAB), which are calculated according to transmission line theory as follows: 37–39 where Z in and Z 0 represent the input impedance and free space impedance, respectively; d and c refer to the absorber thickness and light velocity, respectively. The PC sample without Mo 2 C nanoparticles but has a honeycomb-like porous structure exhibits unsatisfactory absorption performance (Fig.…”

Three-dimensional biotemplate-loaded nickel sulfide vacancies engineered to promote the absorption of electromagnetic waves

“…In addition to analyzing the conductivity, the Debye relaxation is also an important way to analyze the dielectric loss of absorbing materials. 55 Usually, eqn ( 5) can be derived from eqn (3), (4), and ( 5), 54,56 and can represent the relationship between ε′ and ε″, and the semicircular curve of ε′ − ε″ proves the existence of the Debye relaxation process, also called Cole-Cole semicircles. Each semicircle represents a Debye relaxation process; therefore, the Cole-Cole semicircle can be used to identify the frequency bands in which polarization occurs.…”

MXenes hierarchical architectures: electromagnetic absorbing, shielding and devices

“…MXenes have similar structure to graphene and can also be used to design metastructures to achieve controlled EM functions. As shown in figure 10(a), Wang et al used a multi-scale synergistic modulation strategy to design an ultra-broadband microwave metamaterial absorber (MMA) based on hollow carbon/MXene/Mo 2 C (HCMM) [127]. They designed three different 3D models for simulation and optimization of the design, including a typical square-order structure, a stacked cross structure, and a composite of the two.…”