Ti 3 C 2 T X MXene has been proven to be a material of high application potential in the field of electromagnetic (EM) protection. Considering the density, MXene/polymer films (MPFs) are fabricated by employing the simple tape casting process and exhibit excellent electromagnetic shielding performance with respect to the MXene content. However, the absorption properties of as-fabricated MPFs are not satisfactory due to the impedance mismatch. Herein, a multilayer impedance gradient absorber with MPFs arranged in order has been successfully designed and prepared. The developed absorber possesses excellent EM wave absorption properties owing to the well-matched impedance and adjustment of permittivity. Moreover, the effect of the thickness of MPFs on the EM wave absorbing properties has been investigated by theoretical calculations and experimental measurements. The HFSS calculation reveals that the effective absorption bandwidth is capable to cover the whole X-band (8.2–12.4 GHz) with only a micro-adjustment of the thickness, with the minimum reflection coefficient (RC min) reaching up to −26.10 dB. In addition, the synergistic effect of the multiple loss mechanisms has been discussed in detail. This study not only proposes the effective design of a novel multilayer impedance gradient absorber, but also provides new fundamental basis for combining the simulation technology and material design.
Junjie Pan,Xinji Li,Wei Xia,Hongjiao Qu,Jingjing Li,Cheng Jiang,Tao Wang,Jianping He
Low-dimensional carbon matrix magnetic nanocomposites exhibit expansive prospects as lightweight microwave absorbers due to their large specific surface area and multiple attenuation characteristics. The two-dimensional (2D) flaky MOF-derived porous nanocomposites are synthesized successfully by acid etching and subsequent thermal reduction. An in-depth study of composition and flaky porous structure shows that acid etching increases multiple interfaces and carbon defects, proving beneficial for improving multiple interfacial polarization and relaxation polarization loss. In addition, the generated ferromagnetic products (Ni 4 N, CoFe) are beneficial in improving the magnetic loss ability. More importantly, the multilayer impedance gradient design optimizes the impedance matching characteristic. As a result, the prepared bilayer absorbing coating exhibits excellent microwave absorption properties with an effective absorption bandwidth (EAB) of 6.32 GHz at a thickness of 2.5 mm with a filling amount less than 15 wt%. When the total thickness is 3 mm, it can exhibit the widest EAB of about 7.1 GHz and the minimum reflection loss ( RL min ) value of about −54.5 dB. The RCS simulation shows that the multilayer coatings exhibit good microwave scattering and absorption ability under different pitching angles, proving potential candidates for excellent microwave absorbers.
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