Currently,carbon materials derived from biomass are widely sought after as electromagnetic absorbing(EMWA)materials owing to the unique structure,as well as the wide range of natural acquisition pathways,economic viab...Currently,carbon materials derived from biomass are widely sought after as electromagnetic absorbing(EMWA)materials owing to the unique structure,as well as the wide range of natural acquisition pathways,economic viability,and simple processing.However,due to the high dielectric properties,mismatched impedance and single attenuation mechanism,they cannot achieve efficient EMWA performance.Herein,the biomass carbon/Co/porous carbon magnetic composites with a layered gradient structure were fabricated by in-situ deposition of ZIF-67 on the lotus leaf base and then pyrolysis at high temperature.By adjusting the pyrolysis temperature,the sample obtained at 650℃ achieved a minimum reflection value(RLmin)of-34.2dB at a matching thickness of 2.6mm,and a maximum effective absorption bandwidth(EAB)of 7.12GHz.The results indicate that this magnetic composite with a multi-sized layered gradient porous structure has a good electron transport network,a large number of heterogeneous interfaces,and dipole polarization centers,which are conducive to multiple reflection and scattering of microwaves,conduction loss,interface loss,magnetic loss,and impedance matching of materials.Therefore,this work provided a reference for optimizing the EMWA performance of carbon materials and designing a layered gradient porous magnetic composite with multi-sized structure.展开更多
The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,e...The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.展开更多
For potential military applications, a flexible metamaterial absorber(MMA) working on whole K-bands with totalthickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented bas...For potential military applications, a flexible metamaterial absorber(MMA) working on whole K-bands with totalthickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequencyselective surface(FSS). The absorber is composed of polyvinyl chloride(PVC) layer, polyimide(PI) layer, and poly tetra fluoro ethylene(PTFE) layer, with a sandwich structure of PVC–PI–PTFE–metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz–45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section(RCS) is reduced at least 10 dB in 11.48 GHz–43.87 GHz frequency ranges,and absorption remained about 90% when the incident angle changed from 0°to 55°. The purposed absorber is fabricated,measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.展开更多
Electronic skin has showcased superior sensing capabilities inspired from human skin.However,most preceding studies focused on the dermis of the skin rather than the epidermis.In particular,the pseudo-porous structura...Electronic skin has showcased superior sensing capabilities inspired from human skin.However,most preceding studies focused on the dermis of the skin rather than the epidermis.In particular,the pseudo-porous structural domain of the epidermis increases the skin's tolerance while ensuring its susceptibility to touch.Yet,most endeavors on the porous structures failed to replicate the superior sensing performance of skin-like counterparts in terms of sensitivity and/or detection range.Stimulated by the strategy that the epidermis of the skin absorbs energy while producing ionic conduction to the nerves,this work initiatively introduced an easy-to-produce,and low-cost pressure sensor based on ionic-gel foam,and achieved a high sensitivity(2893 kPa^(-1))within a wide pressure range(up to~1 MPa),which ranked among the best cases thus far.Moreover,the factors affecting the sensor performance were explored while the sensing principles were enriched.Inspiringly,the plantar pressure measurement by harnessing the as-prepared sensor unveiled an ultra-broad detection range(100 Pa-1 MPa),thus delivering a huge application potential in the field of robot and health monitoring.展开更多
基金supported by the National Natural Science Foundation of China(Nos.21667019,22066017,and 52173267)the Aviation Science Foundation of China(No.2017ZF56020).
文摘Currently,carbon materials derived from biomass are widely sought after as electromagnetic absorbing(EMWA)materials owing to the unique structure,as well as the wide range of natural acquisition pathways,economic viability,and simple processing.However,due to the high dielectric properties,mismatched impedance and single attenuation mechanism,they cannot achieve efficient EMWA performance.Herein,the biomass carbon/Co/porous carbon magnetic composites with a layered gradient structure were fabricated by in-situ deposition of ZIF-67 on the lotus leaf base and then pyrolysis at high temperature.By adjusting the pyrolysis temperature,the sample obtained at 650℃ achieved a minimum reflection value(RLmin)of-34.2dB at a matching thickness of 2.6mm,and a maximum effective absorption bandwidth(EAB)of 7.12GHz.The results indicate that this magnetic composite with a multi-sized layered gradient porous structure has a good electron transport network,a large number of heterogeneous interfaces,and dipole polarization centers,which are conducive to multiple reflection and scattering of microwaves,conduction loss,interface loss,magnetic loss,and impedance matching of materials.Therefore,this work provided a reference for optimizing the EMWA performance of carbon materials and designing a layered gradient porous magnetic composite with multi-sized structure.
基金supported by the National Natural Science Foundation of China(Nos.:52271180,51802155,12304020)National Key R&D Program of China(No.:2021YFB3502500)+2 种基金Natural Science Foundation of Jiangsu Province(BK20230909)Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutionsthe Center for Microscopy and Analysis at Nanjing University of Aeronautics and Astronautics.
文摘The utilization of electromagnetic waves is rapidly advancing into the millimeter-wave frequency range,posing increasingly severe challenges in terms of electromagnetic pollution prevention and radar stealth.However,existing millimeter-wave absorbers are still inadequate in addressing these issues due to their monotonous magnetic resonance pattern.In this work,rare-earth La^(3+)and non-magnetic Zr^(4+)ions are simultaneously incorporated into M-type barium ferrite(BaM)to intentionally manipulate the multi-magnetic resonance behavior.By leveraging the contrary impact of La^(3+)and Zr^(4+)ions on magnetocrystalline anisotropy field,the restrictive relationship between intensity and frequency of the multi-magnetic resonance is successfully eliminated.The magnetic resonance peak-differentiating and imitating results confirm that significant multi-magnetic resonance phenomenon emerges around 35 GHz due to the reinforced exchange coupling effect between Fe^(3+)and Fe^(2+)ions.Additionally,Mosbauer spectra analysis,first-principle calculations,and least square fitting collectively identify that additional La^(3+)doping leads to a profound rearrangement of Zr^(4+)occupation and thus makes the portion of polarization/conduction loss increase gradually.As a consequence,the La^(3+)-Zr^(4+)co-doped BaM achieves an ultra-broad bandwidth of 12.5+GHz covering from 27.5 to 40+GHz,which holds remarkable potential for millimeter-wave absorbers around the atmospheric window of 35 GHz.
基金Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. JD2020JGPY0010)the China Post-doctoral Science Foundation (Grant No. 2020M671834)the Anhui Province Post-doctoral Science Foundation, China (Grant No. 2020A397)。
文摘For potential military applications, a flexible metamaterial absorber(MMA) working on whole K-bands with totalthickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequencyselective surface(FSS). The absorber is composed of polyvinyl chloride(PVC) layer, polyimide(PI) layer, and poly tetra fluoro ethylene(PTFE) layer, with a sandwich structure of PVC–PI–PTFE–metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz–45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section(RCS) is reduced at least 10 dB in 11.48 GHz–43.87 GHz frequency ranges,and absorption remained about 90% when the incident angle changed from 0°to 55°. The purposed absorber is fabricated,measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.
基金supported the Chongqing Natural Science Foundation(CSTB2023NSCQ-MSX0459&CSTB2023NSCQ-MSX0231)the Graduate Research and Innovation Foundation of Chongqing,China(CYB23048)+1 种基金the Fundamental Research Program under Grant(JCKY2022603C017)National Natural Science Foundation of China(NSFC 52175281).
文摘Electronic skin has showcased superior sensing capabilities inspired from human skin.However,most preceding studies focused on the dermis of the skin rather than the epidermis.In particular,the pseudo-porous structural domain of the epidermis increases the skin's tolerance while ensuring its susceptibility to touch.Yet,most endeavors on the porous structures failed to replicate the superior sensing performance of skin-like counterparts in terms of sensitivity and/or detection range.Stimulated by the strategy that the epidermis of the skin absorbs energy while producing ionic conduction to the nerves,this work initiatively introduced an easy-to-produce,and low-cost pressure sensor based on ionic-gel foam,and achieved a high sensitivity(2893 kPa^(-1))within a wide pressure range(up to~1 MPa),which ranked among the best cases thus far.Moreover,the factors affecting the sensor performance were explored while the sensing principles were enriched.Inspiringly,the plantar pressure measurement by harnessing the as-prepared sensor unveiled an ultra-broad detection range(100 Pa-1 MPa),thus delivering a huge application potential in the field of robot and health monitoring.
