The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)at...The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)attenuation behavior remain poorly understood.To address this gap,a thermodynamically controlled periodic coordination strategy is proposed to achieve precise modulation of magnetic nanoparticle spacing.This approach unveils the evolution of magnetic domain configurations,progressing from individual to coupled and ultimately to crosslinked domain configurations.A unique magnetic coupling phenomenon surpasses the Snoek limit in low-frequency range,which is observed through micromagnetic simulation.The crosslinked magnetic configuration achieves effective low-frequency EM wave absorption at 3.68 GHz,encompassing nearly the entire C-band.This exceptional magnetic interaction significantly enhances radar camouflage and thermal insulation properties.Additionally,a robust gradient metamaterial design extends coverage across the full band(2–40 GHz),effectively mitigating the impact of EM pollution on human health and environment.This comprehensive study elucidates the evolution mechanisms of magnetic domain configurations,addresses gaps in dynamic magnetic modulation,and provides novel insights for the development of high-performance,low-frequency EM wave absorption materials.展开更多
Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship betw...Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.展开更多
Considering the challenges posed by severe electromagnetic wave pollution and escalating international tensions,there is a critical need to develop advanced electromagnetic wave absorbing(EMWA)materials that integrate...Considering the challenges posed by severe electromagnetic wave pollution and escalating international tensions,there is a critical need to develop advanced electromagnetic wave absorbing(EMWA)materials that integrate radar stealth and thermal insulation capabilities.In this study,we have synthesized three-dimensional(3D)porous composites comprising V_(2)O_(3) nanoparticles embedded in Juncus effusus cellulose-derived carbon aerogels(VCA)using a self-templating method followed by high-temperature pyrolysis.The V_(2)O_(3) nanoparticles possess a 3D V-V framework and a relatively narrow bandgap,facilitating the Mott transition for enhanced conductivity.Furthermore,their uniform dispersion on hollow carbon tubes of Juncus effusus promotes efficient electron transfer and creates numerous heterogeneous interfaces.Consequently,VCA-2 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.92 dB at a matching thickness of 2.0mm and a maximum effective absorption bandwidth of 8.24 GHz at a thickness of 2.44mm,covering nearly half of the tested frequency range.Additionally,the radar cross-section reduction reaches a peak value of 29.40 dB m^(2),underscoring the excellent radar stealth capabilities of the material.In summary,VCA exhibits exceptional EMWA,radar stealth,and thermal insulation properties,highlighting its potential for multifunctional applications in EMWA material development.展开更多
The swift advancement of electronics technology has led to a burgeoning interest in multifunctionaliz-ing electromagnetic wave(EMW)absorption materials as a prospective avenue for future development.However,the effect...The swift advancement of electronics technology has led to a burgeoning interest in multifunctionaliz-ing electromagnetic wave(EMW)absorption materials as a prospective avenue for future development.However,the effective integration of diverse functions within a single material continues to present chal-lenges.This work successfully fabricated a three-dimensional(3D)porous Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC frame-work with carbon microspheres through uncomplicated freeze-drying and high-temperature pyrolysis techniques.The resultant magnetic bimetallic carbide(Co_(6)Mo_(6)C_(2) and Mo_(2)C)nanoparticles are uniformly and densely embedded within the carbon layer,facilitated jointly by a rigid template(molybdenum salt)and a flexible template(glucose),thus realizing an exceptional dual loss mechanism involving dielectric and magnetic components.The establishment of the 3D porous conductive network enhances EMW ab-sorption through multiple reflections and scattering mechanisms.Impressively,the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework attains remarkable EMW absorption characteristics with ultralightweight(0.1567 g cm^(-3)),ul-trathin matching thickness(1.7 mm),and robust absorption(reflection loss R_(L) value of-65.89 dB).Fur-thermore,it achieves a noteworthy effective absorption bandwidth(EAB,R_(L)≤-10 dB)spanning 6.4 GHz,ensuring complete absorption of 100%within the X band(8-12 GHz)at a matching thickness of 2 mm.In addition,the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework exhibits pronounced hydrophobicity and magnetic respon-siveness,bestowing upon it appealing attributes including self-cleaning,flame retardancy,and thermal insulation,on par with those observed in commercial products.The radar cross-sectional area(RSC)re-duction value of the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework can reach 35.2 dB m^(2) by RSC simulation,which can effectively lower the likelihood of detection by radar detectors for the target.This study presents a viable strategy for the advancement of novel lightweight and multifunctional materials that demonstrate exceptional performance in absorbing electromagnetic waves.展开更多
Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic h...Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.展开更多
Five new transition metal complexes [Cu（HL）2（H20）2] （1）, [Cu（HL）z（phen）] （2）, [Cu（HL）2（H20）]2（4,4′-bipy） （3）, [Zn（HL）2（HzO）2].（4,4′-bipy） （4）, [Ag（HL）（4,4′-bipy）]n （5）, （H2L=5-chl...Five new transition metal complexes [Cu（HL）2（H20）2] （1）, [Cu（HL）z（phen）] （2）, [Cu（HL）2（H20）]2（4,4′-bipy） （3）, [Zn（HL）2（HzO）2].（4,4′-bipy） （4）, [Ag（HL）（4,4′-bipy）]n （5）, （H2L=5-chloro-l-phenyl-lH-pyrazole-3,4-dicarboxylic acid, phen=1,10-phenanthroline; 4,4′-bipy = 4,4′bipyridine） have been synthesized and characterized. Complexes 1, 2 and 4 exhibit monomeric structures, 3 shows a dinuclear structure, 5 displays 1D chain structure, and all extend to 3D supramolecular network via rich hydrogen bonds. Complexes 1, 2, 3, 5 comprise single helical chains, while complex 4 generates quadruple-stranded helical chains. Furthermore, the antibacterial activities of the titled complexes against bacterial species, three Gram positive bacteria （Staphylococcus aureus, Bacillus subtilis and Candida albicans） and two Gram negative bacteria （Escherichia coli and Pseudomonas aeruginosa） were stud-ied and compared to the activities of free ligands by using the microdilution method.展开更多
基金supported by the National Natural Science Foundation of China(22265021,52231007,and 12327804)the Aeronautical Science Foundation of China(2020Z056056003)Jiangxi Provincial Natural Science Foundation(20232BAB212004).
文摘The precise tuning of magnetic nanoparticle size and magnetic domains,thereby shaping magnetic properties.However,the dynamic evolution mechanisms of magnetic domain configurations in relation to electromagnetic(EM)attenuation behavior remain poorly understood.To address this gap,a thermodynamically controlled periodic coordination strategy is proposed to achieve precise modulation of magnetic nanoparticle spacing.This approach unveils the evolution of magnetic domain configurations,progressing from individual to coupled and ultimately to crosslinked domain configurations.A unique magnetic coupling phenomenon surpasses the Snoek limit in low-frequency range,which is observed through micromagnetic simulation.The crosslinked magnetic configuration achieves effective low-frequency EM wave absorption at 3.68 GHz,encompassing nearly the entire C-band.This exceptional magnetic interaction significantly enhances radar camouflage and thermal insulation properties.Additionally,a robust gradient metamaterial design extends coverage across the full band(2–40 GHz),effectively mitigating the impact of EM pollution on human health and environment.This comprehensive study elucidates the evolution mechanisms of magnetic domain configurations,addresses gaps in dynamic magnetic modulation,and provides novel insights for the development of high-performance,low-frequency EM wave absorption materials.
基金supported by the National Natural Science Foundation of China(22265021)the Aeronautical Science Foundation of China(2020Z056056003)Jiangxi Provincial Natural Science Foundation(20232BAB212004).
文摘Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.
基金supported by the National Natural Science Foundation of China(No.22265021)the Aeronautical Science Foundation of China(No.2020Z056056003)。
文摘Considering the challenges posed by severe electromagnetic wave pollution and escalating international tensions,there is a critical need to develop advanced electromagnetic wave absorbing(EMWA)materials that integrate radar stealth and thermal insulation capabilities.In this study,we have synthesized three-dimensional(3D)porous composites comprising V_(2)O_(3) nanoparticles embedded in Juncus effusus cellulose-derived carbon aerogels(VCA)using a self-templating method followed by high-temperature pyrolysis.The V_(2)O_(3) nanoparticles possess a 3D V-V framework and a relatively narrow bandgap,facilitating the Mott transition for enhanced conductivity.Furthermore,their uniform dispersion on hollow carbon tubes of Juncus effusus promotes efficient electron transfer and creates numerous heterogeneous interfaces.Consequently,VCA-2 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.92 dB at a matching thickness of 2.0mm and a maximum effective absorption bandwidth of 8.24 GHz at a thickness of 2.44mm,covering nearly half of the tested frequency range.Additionally,the radar cross-section reduction reaches a peak value of 29.40 dB m^(2),underscoring the excellent radar stealth capabilities of the material.In summary,VCA exhibits exceptional EMWA,radar stealth,and thermal insulation properties,highlighting its potential for multifunctional applications in EMWA material development.
基金This work was supported by the National Natural Science Foun-dation of China(No.22269010)the Jiangxi Provincial Natural Sci-ence Foundation(No.20224BAB214021)+3 种基金the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province(No.20212BCJ23020)the Science and Technology Project of Jiangxi Provincial Department of Education(No.GJJ211305)the Opening Project of National Engineering Research Center for Do-mestic&Building Ceramics(No.GXZX2302)the Graduate In-novation Fund of Jiangxi Province(YC2023-S799).
文摘The swift advancement of electronics technology has led to a burgeoning interest in multifunctionaliz-ing electromagnetic wave(EMW)absorption materials as a prospective avenue for future development.However,the effective integration of diverse functions within a single material continues to present chal-lenges.This work successfully fabricated a three-dimensional(3D)porous Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC frame-work with carbon microspheres through uncomplicated freeze-drying and high-temperature pyrolysis techniques.The resultant magnetic bimetallic carbide(Co_(6)Mo_(6)C_(2) and Mo_(2)C)nanoparticles are uniformly and densely embedded within the carbon layer,facilitated jointly by a rigid template(molybdenum salt)and a flexible template(glucose),thus realizing an exceptional dual loss mechanism involving dielectric and magnetic components.The establishment of the 3D porous conductive network enhances EMW ab-sorption through multiple reflections and scattering mechanisms.Impressively,the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework attains remarkable EMW absorption characteristics with ultralightweight(0.1567 g cm^(-3)),ul-trathin matching thickness(1.7 mm),and robust absorption(reflection loss R_(L) value of-65.89 dB).Fur-thermore,it achieves a noteworthy effective absorption bandwidth(EAB,R_(L)≤-10 dB)spanning 6.4 GHz,ensuring complete absorption of 100%within the X band(8-12 GHz)at a matching thickness of 2 mm.In addition,the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework exhibits pronounced hydrophobicity and magnetic respon-siveness,bestowing upon it appealing attributes including self-cleaning,flame retardancy,and thermal insulation,on par with those observed in commercial products.The radar cross-sectional area(RSC)re-duction value of the Co_(6)Mo_(6)C_(2)/Mo_(2)C@NC framework can reach 35.2 dB m^(2) by RSC simulation,which can effectively lower the likelihood of detection by radar detectors for the target.This study presents a viable strategy for the advancement of novel lightweight and multifunctional materials that demonstrate exceptional performance in absorbing electromagnetic waves.
基金the National Natural Science Foundation of China(22265021)the Aeronautical Science Foundation of China(2020Z056056003).
文摘Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.
基金This work was supported by the National Natural Science Foundation of China （Nos. 20961007 and 21264011）, the Aviation Fund （No. 2010ZF56023） and the Young Scientists Program of Jiangxi Province （No. 2008DQ00600）.
文摘Five new transition metal complexes [Cu（HL）2（H20）2] （1）, [Cu（HL）z（phen）] （2）, [Cu（HL）2（H20）]2（4,4′-bipy） （3）, [Zn（HL）2（HzO）2].（4,4′-bipy） （4）, [Ag（HL）（4,4′-bipy）]n （5）, （H2L=5-chloro-l-phenyl-lH-pyrazole-3,4-dicarboxylic acid, phen=1,10-phenanthroline; 4,4′-bipy = 4,4′bipyridine） have been synthesized and characterized. Complexes 1, 2 and 4 exhibit monomeric structures, 3 shows a dinuclear structure, 5 displays 1D chain structure, and all extend to 3D supramolecular network via rich hydrogen bonds. Complexes 1, 2, 3, 5 comprise single helical chains, while complex 4 generates quadruple-stranded helical chains. Furthermore, the antibacterial activities of the titled complexes against bacterial species, three Gram positive bacteria （Staphylococcus aureus, Bacillus subtilis and Candida albicans） and two Gram negative bacteria （Escherichia coli and Pseudomonas aeruginosa） were stud-ied and compared to the activities of free ligands by using the microdilution method.
