The demand of high-end electromagnetic wave absorbing materials puts forward higher requirements on comprehensive performances of small thickness,lightweight,broadband,and strong absorption.Herein,a novel multi-layer ...The demand of high-end electromagnetic wave absorbing materials puts forward higher requirements on comprehensive performances of small thickness,lightweight,broadband,and strong absorption.Herein,a novel multi-layer stepped metamaterial absorber with gradient electromagnetic properties is proposed.The complex permittivity and permeability of each layer are tailored via the proportion of carbonyliron and carbon-fiber dispersing into the epoxy resin.The proposed metamaterial is further optimized via adjusting the electromagnetic parameters and geometric sizes of each layer.Comparing with the four-layer composite with gradient electromagnetic properties which could only realize reflection loss(RL)of less than−6 dB in 2.0-40 GHz,the optimized stepped metamaterial with the same thickness and electromagnetic properties realizes less than−10 dB in the relevant frequency range.Additionally,the RL of less than−15 dB is achieved in the frequency range of 11.2-21.4 GHz and 28.5-40 GHz.The multiple electromagnetic wave absorption mechanism is discussed based on the experimental and simulation results,which is believed to be attributed to the synergy effect induced by multi-scale structures of the metamaterial.Therefore,combining multi-layer structures and periodic stepped structures into a novel gradient absorbing metamaterial would give new insights into designing microwave absorption devices for broadband electromagnetic protections.展开更多
Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural ...Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 52102113)the Nature Science Foundation of Shaanxi in China (No. 2022JQ-323)+1 种基金the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials LaboratoryNatural Science Foundation and Department of Education of Shaanxi in China (No. 21JK0912)
文摘The demand of high-end electromagnetic wave absorbing materials puts forward higher requirements on comprehensive performances of small thickness,lightweight,broadband,and strong absorption.Herein,a novel multi-layer stepped metamaterial absorber with gradient electromagnetic properties is proposed.The complex permittivity and permeability of each layer are tailored via the proportion of carbonyliron and carbon-fiber dispersing into the epoxy resin.The proposed metamaterial is further optimized via adjusting the electromagnetic parameters and geometric sizes of each layer.Comparing with the four-layer composite with gradient electromagnetic properties which could only realize reflection loss(RL)of less than−6 dB in 2.0-40 GHz,the optimized stepped metamaterial with the same thickness and electromagnetic properties realizes less than−10 dB in the relevant frequency range.Additionally,the RL of less than−15 dB is achieved in the frequency range of 11.2-21.4 GHz and 28.5-40 GHz.The multiple electromagnetic wave absorption mechanism is discussed based on the experimental and simulation results,which is believed to be attributed to the synergy effect induced by multi-scale structures of the metamaterial.Therefore,combining multi-layer structures and periodic stepped structures into a novel gradient absorbing metamaterial would give new insights into designing microwave absorption devices for broadband electromagnetic protections.
基金supported by the National Natural Science Foundation of China(Grant Nos.52102113,52231007)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2021160)the Creative Research Foundation of TSCM。
文摘Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.
