Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effect...Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effective strategy to solve the puzzle.Herein,a single source hyperbranched polyborosi-lazane precursor containing hafnium(hb-PBSZ-Hf)is introduced and the SiBCNHf ceramic is obtained by further pyrolysis.The micro-sized tissues including HfC,SiC,HfB 2 nanocrystals and segregated carbons are in situ generated during annealing which not only increase EM wave absorption ability(minimum re-flection coefficient(RC_(min))is-56.71 dB with a thickness of 2.5 mm,effective absorption bandwidth(EAB)is 3.4 GHz),but also improve antioxidation property(less than 2 wt.%mass fluctuation at 1400℃in air).Theoretical simulation of complex permittivity suggests that SiBCNHf ceramic has an RC_(min)of less than-5 dB for the whole X-band even at 1100℃.Such SiBCNHf ceramic with superior high-temperature-resistance and antioxidation performance derived from single source precursors possesses great potential for EM wave absorbing coatings in high-temperature and harsh environments.展开更多
Realizing ultra-wideband absorption,desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials.Herein,we hav...Realizing ultra-wideband absorption,desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials.Herein,we have constructed a porous carbon fiber/polymethacrylimide(CP)structure for acquiring promising microwave absorption performance and withstanding both elevated temperature and high strength in a low density.Given the ability of porous structure to induce desirable impedance matching and multiple reflection,the absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K.Additionally,the presence of imide ring group in polymethacrylimide and hard bubble wall endows the composite with excellent heat and compressive behaviors.Besides,the lightweight of the CP composite with a density of only 110 mg cm^(−3) coupled with high compressive strength of 1.05 MPa even at 453 K also satisfies the requirements in engineering applica-tions.Compared with soft and compressible aerogel materials,we envision that the rigid porous foam absorbing material is particularly suitable for environmental extremes.展开更多
The rising concern over electromagnetic (EM) pollution is re-sponsible for the rapid progress in EM interference (EMI) shielding and EM wave absorption in the last few years, and carbon materials with a large sur-face...The rising concern over electromagnetic (EM) pollution is re-sponsible for the rapid progress in EM interference (EMI) shielding and EM wave absorption in the last few years, and carbon materials with a large sur-face area and high porosity have been investigated. Compared to other car-bon materials, biomass-derived carbon (BC) are considered efficient and eco-friendly materials for this purpose. We summarize the recent advances in BC materials for both EMI shielding and EM wave absorption. After a brief overview of the synthesis strategies of BC materials and a precise out-line of EM wave interference, strategies for improving their EMI shielding and EM wave absorption are discussed. Finally, the existing challenges and the future prospects for such materials are briefly summarized.展开更多
Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nano...Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.展开更多
High-performance electromagnetic(EM)wave absorbers,covalently bonded reduced graphene oxideFe_(3)O_(4) nanocomposites(rGO-Fe_(3)O_(4)),are synthesized via hydrothermal reaction,amidation reaction and reduction process...High-performance electromagnetic(EM)wave absorbers,covalently bonded reduced graphene oxideFe_(3)O_(4) nanocomposites(rGO-Fe_(3)O_(4)),are synthesized via hydrothermal reaction,amidation reaction and reduction process.The microstructure,surface element composition and morphology of rGO-Fe_(3)O_(4) nanocomposites are characterized and corresponding EM wave absorption properties are analyzed in great detail.It demonstrates that Fe_(3)O_(4) nanoparticles are successfully covalently grafted onto graphene by amide bonds.When the mass ratio of rGO and Fe_(3)O_(4) is 2:1(sample S2),the absorber exhibits the excellent EM wave absorption performance that the maximum reflection loss(RL)reaches up to-48.6 dB at 14.4 GHz,while the effective absorption bandwidth(RL<-10 dB)is 6.32 GHz(11.68-18.0 GHz)with a matching thickness of 2.1 mm.Furthermore,radar cross section(RCS)simulation calculation is also adopted to evaluate the ability of absorbers to scatter EM waves,which proves again that the absorption performance of absorber S2 is optimal.The outstanding EM wave absorption performance is attributed to the synergistic effect between dielectric and magnetic loss,good attenuation ability and excellent impedance matching.Moreover,covalent bonds considered to be carrier channels can facilitate electron migration,adjust EM parameters and then enhance EM wave absorption perfo rmance.This work provides a possible method for preparing efficient EM wave absorbers.展开更多
Superior electromagnetic(EM)wave absorption properties in 8.2-12.4 GHz(X-band)can be obtained via the effective combination of polyaniline(PANI)and CuS.Herein,novel 3D flower-like hollow CuS@PANI microspheres were fab...Superior electromagnetic(EM)wave absorption properties in 8.2-12.4 GHz(X-band)can be obtained via the effective combination of polyaniline(PANI)and CuS.Herein,novel 3D flower-like hollow CuS@PANI microspheres were fabricated by a solvothermal process followed by in-situ polymerization.EM wave absorption properties of 3D flower-like hollow CuS@PANI microspheres in X-band were systematically studied,indicating the minimum reflection loss(RL_(min))of-71.1 dB and effective absorption bandwidth(EAB)covering 81%of test frequency range were achieved with a thickness of 2.75 mm.Excellent EM wave absorption properties of 3D flower-like hollow CuS@PANI microspheres were mainly ascribed to outstanding impedance matching characteristic and dielectric loss capability(conduction loss,interfacial polarization loss and dipole polarization loss).Moreover,due to the distinctive flower-like hollow struc-ture of CuS@PANI microspheres,an additional wave-absorbing mechanism was provided by increasing the transmission paths of EM waves.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
Conductive polymer composites(CPCs)have attracted significant interest in the field of flexible electro-magnetic protection,but the challenge of balancing high electromagnetic interference shielding effec-tiveness(EMI...Conductive polymer composites(CPCs)have attracted significant interest in the field of flexible electro-magnetic protection,but the challenge of balancing high electromagnetic interference shielding effec-tiveness(EMI SE)and low reflection losses still exists.Herein,thermoplastic polyurethane/silver nanorod(TPU/AgNR)composite foams have been successfully prepared using both the salt template and vacuum-assisted thermal compression methods.By varying the AgNRs content and employing a layer-by-layer bonding approach,a gradient structure with optimized impedance matching is achieved.The“absorb-reflect-reabsorb”EM attenuation mechanismofthe asymmetricgradientEMI shieldingin theinternal structure is exploited,resulting in TPU/AgNR foam(TAF)with high EMI SE and significantly reduced EM reflection.Notably,the three-layer foams exhibit an average shielding efficacy of 35.5 dB and a reflected power coefficient(R)of 0.085 in the X-band,thereby substantially mitigating secondary EM wave reflec-tions.Furthermore,these foams demonstrate exemplary compressive resilience,with the sample main-taining excellent EMI shielding stability even after undergoing 100 compression cycles at 50%strain.Consequently,a straightforward approach is employed to fabricate materials with high EMI SE and low reflectivity,offering the potential for use in EM shielding applications of next-generation flexible elec-tronic devices.展开更多
Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usu...Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usually involves complex procedures and extremely depends on unidirectional freezing technique.Herein,we propose a groundbreaking approach that leverages the assemblies of salting-out protein induced by ammonium metatungstate(AM)as the precursor,and then acquire directional three-dimensional carbon-based foams through simple pyrolysis.The electrostatic interaction between AM and protein ensures well dispersion of WC_(1−x)nanoparticles on carbon frameworks.The content of WC_(1−x)nanoparticles can be rationally regulated by AM dosage,and it also affects the electromagnetic(EM)properties of final carbon-based foams.The optimized foam exhibits exceptional EM absorption performance,achieving a remarkable minimum reflection loss of−72.0 dB and an effective absorption bandwidth of 6.3 GHz when EM wave propagates parallel to the directional pores.Such performance benefits from the synergistic effects of macroporous architecture and compositional design.Although there is a directional dependence of EM absorption,radar stealth simulation demonstrates that these foams can still promise considerable reduction in radar cross section with the change of incident angle.Moreover,COMSOL simulation further identifies their good performance in preventing EM interference among different electronic components.展开更多
The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollu...The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.展开更多
Ceramic materials have obvious advantages in thermal stability,but impedance mismatch limits their ability to attenuate electromagnetic(EM)waves.Herein,a novel series of high-entropy(V_(0.2)Nb_(0.2)Zr_(0.2)Ta_(0.2)X_(...Ceramic materials have obvious advantages in thermal stability,but impedance mismatch limits their ability to attenuate electromagnetic(EM)waves.Herein,a novel series of high-entropy(V_(0.2)Nb_(0.2)Zr_(0.2)Ta_(0.2)X_(0.2))B_(2)(X=Mo,Ti,and Hf)ceramics were successfully synthesized via ultrafast high-temperature sintering(UHS)apparatus based on joule heating.The results indicated that the effect of high-entropy component on the magnetic loss of the system was relatively small,but the effect on the dielectric loss was larger.Among them,the(V_(0.2)Nb_(0.2)Zr_(0.2)Ta_(0.2)Ti_(0.2))B_(2)(HEB-Ti)sample demonstrated superior absorbing properties due to relatively moderate dielectric loss and optimal EM impedance matching.Moreover,because of its relatively moderate attenuation constant,it could achieve the maximum penetration of the EM wave and the minimum reflection after absorbing wave.As a result,the minimum reflection loss(RL_(min))was as low as−40.7 dB,and the effective absorption band covered the entire low-frequency range from 2 to 8 GHz.Its excellent absorption performance was mainly due to the synergistic effect of various dielectric attenuation mechanisms,including defect polarization,dipole polarization,and conduction loss.Furthermore,thermogravimetric(TG)analysis showed that the sample exhibited excellent thermal stability and could withstand temperatures up to 550℃in air and 1000℃in an argon gas environment.The relevant work could provide meaningful references for the design of new high-performance ceramic wave-absorbing materials.展开更多
Ferrites are the most widely used microwave absorbing materials to deal with the threat of electromagnetic(EM)pollution.However,the lack of sufficient dielectric loss capacity is the main challenge that limits their a...Ferrites are the most widely used microwave absorbing materials to deal with the threat of electromagnetic(EM)pollution.However,the lack of sufficient dielectric loss capacity is the main challenge that limits their applications.To cope with this challenge,three high-entropy(HE)spineltype ferrite ceramics including(Mg_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2))Fe_(2)O_(4),(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2))Fe_(2)O_(4),and(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Fe_(2)O_(4)were designed and successfully prepared through solid state synthesis.The results show that all three HE MFe_(2)O_(4) samples exhibit synergetic dielectric loss and magnetic loss.The good magnetic loss ability is due to the presence of magnetic components;while the enhanced dielectric properties are attributed to nano-domain,hopping mechanism of resonance effect and HE effect.Among three HE spinels,(Mg_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2))Fe_(2)O_(4)shows the best EM wave absorption performance,e.g.,its minimum reflection loss(RL_(min))reaches-35.10 dB at 6.78 GHz with a thickness of 3.5 mm,and the optimized effective absorption bandwidth(EAB)is 7.48 GHz from 8.48 to 15.96 GHz at the thickness of 2.4 mm.Due to the easy preparation and strong EM dissipation ability,HE MFe_(2)O_(4) are promising as a new type of EM absorption materials.展开更多
Electronic devices pervade everyday life,which has triggered severe electromagnetic(EM)wave pollution.To face this challenge,developing EM wave absorbers with ultra-broadband absorption capacity is critically required...Electronic devices pervade everyday life,which has triggered severe electromagnetic(EM)wave pollution.To face this challenge,developing EM wave absorbers with ultra-broadband absorption capacity is critically required.Currently,nano-composite construction has been widely utilized to realize impedance match and broadband absorption.However,complex experimental procedures,limited thermal stability,and interior oxidation resistance are still unneglectable issues.Therefore,it is appealing to realize ultra-broadband EM wave absorption in single-phase materials with good stability.Aiming at this target,two high-entropy transition metal carbides(HE TMCs)including(Zr,Hf,Nb,Ta)C(HE TMC-2)and(Cr,Zr,Hf,Nb,Ta)C(HE TMC-3)are designed and synthesized,of which the microwave absorption performance is investigated in comparison with previously reported(Ti,Zr,Hf,Nb,Ta)C(HE TMC-1).Due to the synergistic effects of dielectric and magnetic losses,HE TMC-2 and HE TMC-3 exhibit better impedance match and wider effective absorption bandwidth(EAB).In specific,the exclusion of Ti element in HE TMC-2 endows it optimal minimum reflection loss(RL_(min))and EAB of−41.7 dB(2.11 mm,10.52 GHz)and 3.5 GHz(at 3.0 mm),respectively.Remarkably,the incorporation of Cr element in HE TMC-3 significantly improves the impedance match,thus realizing EAB of 10.5,9.2,and 13.9 GHz at 2,3,and 4 mm,respectively.The significance of this study lays on realizing ultra-broadband capacity in HE TMC-3(Cr,Zr,Hf,Nb,Ta),demonstrating the effectiveness of high-entropy component design in tailoring the impedance match.展开更多
The key to solve increasingly severe electromagnetic(EM)pollution is to explore sustainable,easily prepared,and cost-effective EM wave absorption materials with exceptional absorption capability.Herein,instead of anch...The key to solve increasingly severe electromagnetic(EM)pollution is to explore sustainable,easily prepared,and cost-effective EM wave absorption materials with exceptional absorption capability.Herein,instead of anchoring on carbon materials in single layer,MoS_(2) flower-like microspheres were stacked on the surface of pomelo peels-derived porous carbon nanosheets(C)to fabricate MoS_(2)@C nanocomposites by a facile solvothermal process.EM wave absorption performances of MoS_(2)@C nanocomposites in X-band were systematically investigated,indicating the minimum reflection loss(RLmin)of-62.3 dB(thickness of 2.88 mm)and effective absorption bandwidth(EAB)almost covering the whole X-band(thickness of 2.63 mm)with the filler loading of only 20 wt.%.Superior EM wave absorption performances of MoS_(2)@C nanocomposites could be attributed to the excellent impedance matching characteristic and dielectric loss capacity(conduction loss and polarization loss).This study revealed that the as-prepared MoS_(2)@C nanocomposites would be a novel prospective candidate for the sustainable EM absorbents with superior EM wave absorption performances.展开更多
SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performa...SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching.Herein,we report ultralight SiC/Si3N4 composite aerogels(~15 mg·cm^(−3))consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons.Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method.The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss(RL,−48.6 dB)and a wide effective absorption band(EAB,7.4 GHz)at a thickness of 2 mm,attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure.In addition,the aerogel exhibits high thermal stability in air until 1000℃and excellent thermal insulation performance(0.030 W·m^(−1)·K^(−1)).These superior performances make the SiC/Si_(3)N_(4) composite aerogel promising to become a new generation of absorption material served under extreme conditions.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025034)National Science and Technology Major Project of China(No.J2019-VI-0017-0132).
文摘Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effective strategy to solve the puzzle.Herein,a single source hyperbranched polyborosi-lazane precursor containing hafnium(hb-PBSZ-Hf)is introduced and the SiBCNHf ceramic is obtained by further pyrolysis.The micro-sized tissues including HfC,SiC,HfB 2 nanocrystals and segregated carbons are in situ generated during annealing which not only increase EM wave absorption ability(minimum re-flection coefficient(RC_(min))is-56.71 dB with a thickness of 2.5 mm,effective absorption bandwidth(EAB)is 3.4 GHz),but also improve antioxidation property(less than 2 wt.%mass fluctuation at 1400℃in air).Theoretical simulation of complex permittivity suggests that SiBCNHf ceramic has an RC_(min)of less than-5 dB for the whole X-band even at 1100℃.Such SiBCNHf ceramic with superior high-temperature-resistance and antioxidation performance derived from single source precursors possesses great potential for EM wave absorbing coatings in high-temperature and harsh environments.
基金supported by the National Natural Science Foundation of China(52172091 and 52172295)the Interdisciplinary Innovation Foundation for Graduates(Nanjing University of Aeronautics and Astronautics,No.KXKCXJJ202009).
文摘Realizing ultra-wideband absorption,desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials.Herein,we have constructed a porous carbon fiber/polymethacrylimide(CP)structure for acquiring promising microwave absorption performance and withstanding both elevated temperature and high strength in a low density.Given the ability of porous structure to induce desirable impedance matching and multiple reflection,the absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K.Additionally,the presence of imide ring group in polymethacrylimide and hard bubble wall endows the composite with excellent heat and compressive behaviors.Besides,the lightweight of the CP composite with a density of only 110 mg cm^(−3) coupled with high compressive strength of 1.05 MPa even at 453 K also satisfies the requirements in engineering applica-tions.Compared with soft and compressible aerogel materials,we envision that the rigid porous foam absorbing material is particularly suitable for environmental extremes.
基金Anusandhan National Research Foundation (ANRF), Department of Science & Technology (DST), New Delhi, India under Ramanujan award (SB/S2/RJN-159/2017)。
文摘The rising concern over electromagnetic (EM) pollution is re-sponsible for the rapid progress in EM interference (EMI) shielding and EM wave absorption in the last few years, and carbon materials with a large sur-face area and high porosity have been investigated. Compared to other car-bon materials, biomass-derived carbon (BC) are considered efficient and eco-friendly materials for this purpose. We summarize the recent advances in BC materials for both EMI shielding and EM wave absorption. After a brief overview of the synthesis strategies of BC materials and a precise out-line of EM wave interference, strategies for improving their EMI shielding and EM wave absorption are discussed. Finally, the existing challenges and the future prospects for such materials are briefly summarized.
基金the National Natural Science Foundation of China(52203100)Shaanxi Province Key Research and Development Plan Project(2024GX-YBXM-386)+3 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2682)Undergraduate Innovation&Business Program of Northwestern Polytechnical University(S202310699322)the Analytical&Testing Center of Northwestern Polytechnical University for SEM tests performed in this work.
文摘Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.
基金financially supported by the National Natural Science Foundation of China(No.51672222)the Joint Fund Project-Enterprise-Shaanxi Coal Joint Fund Project(No.2019JLM-32)the Spaceflight Foundation of China(No.2014-HT-XGD)。
文摘High-performance electromagnetic(EM)wave absorbers,covalently bonded reduced graphene oxideFe_(3)O_(4) nanocomposites(rGO-Fe_(3)O_(4)),are synthesized via hydrothermal reaction,amidation reaction and reduction process.The microstructure,surface element composition and morphology of rGO-Fe_(3)O_(4) nanocomposites are characterized and corresponding EM wave absorption properties are analyzed in great detail.It demonstrates that Fe_(3)O_(4) nanoparticles are successfully covalently grafted onto graphene by amide bonds.When the mass ratio of rGO and Fe_(3)O_(4) is 2:1(sample S2),the absorber exhibits the excellent EM wave absorption performance that the maximum reflection loss(RL)reaches up to-48.6 dB at 14.4 GHz,while the effective absorption bandwidth(RL<-10 dB)is 6.32 GHz(11.68-18.0 GHz)with a matching thickness of 2.1 mm.Furthermore,radar cross section(RCS)simulation calculation is also adopted to evaluate the ability of absorbers to scatter EM waves,which proves again that the absorption performance of absorber S2 is optimal.The outstanding EM wave absorption performance is attributed to the synergistic effect between dielectric and magnetic loss,good attenuation ability and excellent impedance matching.Moreover,covalent bonds considered to be carrier channels can facilitate electron migration,adjust EM parameters and then enhance EM wave absorption perfo rmance.This work provides a possible method for preparing efficient EM wave absorbers.
基金supported by PhD Research Startup Foundation of Bohai University(No.0521bs021).
文摘Superior electromagnetic(EM)wave absorption properties in 8.2-12.4 GHz(X-band)can be obtained via the effective combination of polyaniline(PANI)and CuS.Herein,novel 3D flower-like hollow CuS@PANI microspheres were fabricated by a solvothermal process followed by in-situ polymerization.EM wave absorption properties of 3D flower-like hollow CuS@PANI microspheres in X-band were systematically studied,indicating the minimum reflection loss(RL_(min))of-71.1 dB and effective absorption bandwidth(EAB)covering 81%of test frequency range were achieved with a thickness of 2.75 mm.Excellent EM wave absorption properties of 3D flower-like hollow CuS@PANI microspheres were mainly ascribed to outstanding impedance matching characteristic and dielectric loss capability(conduction loss,interfacial polarization loss and dipole polarization loss).Moreover,due to the distinctive flower-like hollow struc-ture of CuS@PANI microspheres,an additional wave-absorbing mechanism was provided by increasing the transmission paths of EM waves.
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the National Natural Science Foundation of China(Nos.52273085 and 52303113)the Natural Science Foundation of China of Henan Province(No.222300420541)the Key Scientific Research Projects of Colleges and Universities in Henan Province,China(No.24A430045).
文摘Conductive polymer composites(CPCs)have attracted significant interest in the field of flexible electro-magnetic protection,but the challenge of balancing high electromagnetic interference shielding effec-tiveness(EMI SE)and low reflection losses still exists.Herein,thermoplastic polyurethane/silver nanorod(TPU/AgNR)composite foams have been successfully prepared using both the salt template and vacuum-assisted thermal compression methods.By varying the AgNRs content and employing a layer-by-layer bonding approach,a gradient structure with optimized impedance matching is achieved.The“absorb-reflect-reabsorb”EM attenuation mechanismofthe asymmetricgradientEMI shieldingin theinternal structure is exploited,resulting in TPU/AgNR foam(TAF)with high EMI SE and significantly reduced EM reflection.Notably,the three-layer foams exhibit an average shielding efficacy of 35.5 dB and a reflected power coefficient(R)of 0.085 in the X-band,thereby substantially mitigating secondary EM wave reflec-tions.Furthermore,these foams demonstrate exemplary compressive resilience,with the sample main-taining excellent EMI shielding stability even after undergoing 100 compression cycles at 50%strain.Consequently,a straightforward approach is employed to fabricate materials with high EMI SE and low reflectivity,offering the potential for use in EM shielding applications of next-generation flexible elec-tronic devices.
基金financially supported by the National Natural Science Foundation of China(Nos.22475057 and No.52373262).
文摘Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usually involves complex procedures and extremely depends on unidirectional freezing technique.Herein,we propose a groundbreaking approach that leverages the assemblies of salting-out protein induced by ammonium metatungstate(AM)as the precursor,and then acquire directional three-dimensional carbon-based foams through simple pyrolysis.The electrostatic interaction between AM and protein ensures well dispersion of WC_(1−x)nanoparticles on carbon frameworks.The content of WC_(1−x)nanoparticles can be rationally regulated by AM dosage,and it also affects the electromagnetic(EM)properties of final carbon-based foams.The optimized foam exhibits exceptional EM absorption performance,achieving a remarkable minimum reflection loss of−72.0 dB and an effective absorption bandwidth of 6.3 GHz when EM wave propagates parallel to the directional pores.Such performance benefits from the synergistic effects of macroporous architecture and compositional design.Although there is a directional dependence of EM absorption,radar stealth simulation demonstrates that these foams can still promise considerable reduction in radar cross section with the change of incident angle.Moreover,COMSOL simulation further identifies their good performance in preventing EM interference among different electronic components.
基金supported by the PhD Start-up Fund of the Science and Technology Department of Liaoning Province(No.2022-BS-306)the General Cultivation Scientific Research Project of Bohai University(No.0522xn058)the PhD Research Startup Foundation of Bohai University(No.0521bs021).
文摘The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.
基金supported by the National Key R&D Program of China(No.2024YFB3816600)the Guangxi Natural Science Foundation(No.2022GXNSFAA035527)+4 种基金the Natural Science Foundation of Tianjin(Nos.23JCZDJC00150 and 22JCZDJC00080)the Science and Technology Major Project of Ningbo(No.2021Z123)the Yongjiang Talent Introduction Programme(No.2021A-108-G)the Youth Fund of the Chinese Academy of Sciences(No.JCPYJJ-22030)Guilin University of Technology Research Startup Fund(No.RD2100000621).
文摘Ceramic materials have obvious advantages in thermal stability,but impedance mismatch limits their ability to attenuate electromagnetic(EM)waves.Herein,a novel series of high-entropy(V_(0.2)Nb_(0.2)Zr_(0.2)Ta_(0.2)X_(0.2))B_(2)(X=Mo,Ti,and Hf)ceramics were successfully synthesized via ultrafast high-temperature sintering(UHS)apparatus based on joule heating.The results indicated that the effect of high-entropy component on the magnetic loss of the system was relatively small,but the effect on the dielectric loss was larger.Among them,the(V_(0.2)Nb_(0.2)Zr_(0.2)Ta_(0.2)Ti_(0.2))B_(2)(HEB-Ti)sample demonstrated superior absorbing properties due to relatively moderate dielectric loss and optimal EM impedance matching.Moreover,because of its relatively moderate attenuation constant,it could achieve the maximum penetration of the EM wave and the minimum reflection after absorbing wave.As a result,the minimum reflection loss(RL_(min))was as low as−40.7 dB,and the effective absorption band covered the entire low-frequency range from 2 to 8 GHz.Its excellent absorption performance was mainly due to the synergistic effect of various dielectric attenuation mechanisms,including defect polarization,dipole polarization,and conduction loss.Furthermore,thermogravimetric(TG)analysis showed that the sample exhibited excellent thermal stability and could withstand temperatures up to 550℃in air and 1000℃in an argon gas environment.The relevant work could provide meaningful references for the design of new high-performance ceramic wave-absorbing materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.51802289 and 51972089)Financial supports of the Science Foundation for the Excellent Youth Scholars of Henan Province(Grant No.212300410089)the Support Program for Scientific and Technological Innovation Talents of Higher Education in Henan Province(Grant No.21HASTIT004)。
文摘Ferrites are the most widely used microwave absorbing materials to deal with the threat of electromagnetic(EM)pollution.However,the lack of sufficient dielectric loss capacity is the main challenge that limits their applications.To cope with this challenge,three high-entropy(HE)spineltype ferrite ceramics including(Mg_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2))Fe_(2)O_(4),(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2))Fe_(2)O_(4),and(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Fe_(2)O_(4)were designed and successfully prepared through solid state synthesis.The results show that all three HE MFe_(2)O_(4) samples exhibit synergetic dielectric loss and magnetic loss.The good magnetic loss ability is due to the presence of magnetic components;while the enhanced dielectric properties are attributed to nano-domain,hopping mechanism of resonance effect and HE effect.Among three HE spinels,(Mg_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2))Fe_(2)O_(4)shows the best EM wave absorption performance,e.g.,its minimum reflection loss(RL_(min))reaches-35.10 dB at 6.78 GHz with a thickness of 3.5 mm,and the optimized effective absorption bandwidth(EAB)is 7.48 GHz from 8.48 to 15.96 GHz at the thickness of 2.4 mm.Due to the easy preparation and strong EM dissipation ability,HE MFe_(2)O_(4) are promising as a new type of EM absorption materials.
基金We gratefully acknowledge the financial support from the National Natural Science Foundation of China(Nos.51972089,51672064,and U1435206).
文摘Electronic devices pervade everyday life,which has triggered severe electromagnetic(EM)wave pollution.To face this challenge,developing EM wave absorbers with ultra-broadband absorption capacity is critically required.Currently,nano-composite construction has been widely utilized to realize impedance match and broadband absorption.However,complex experimental procedures,limited thermal stability,and interior oxidation resistance are still unneglectable issues.Therefore,it is appealing to realize ultra-broadband EM wave absorption in single-phase materials with good stability.Aiming at this target,two high-entropy transition metal carbides(HE TMCs)including(Zr,Hf,Nb,Ta)C(HE TMC-2)and(Cr,Zr,Hf,Nb,Ta)C(HE TMC-3)are designed and synthesized,of which the microwave absorption performance is investigated in comparison with previously reported(Ti,Zr,Hf,Nb,Ta)C(HE TMC-1).Due to the synergistic effects of dielectric and magnetic losses,HE TMC-2 and HE TMC-3 exhibit better impedance match and wider effective absorption bandwidth(EAB).In specific,the exclusion of Ti element in HE TMC-2 endows it optimal minimum reflection loss(RL_(min))and EAB of−41.7 dB(2.11 mm,10.52 GHz)and 3.5 GHz(at 3.0 mm),respectively.Remarkably,the incorporation of Cr element in HE TMC-3 significantly improves the impedance match,thus realizing EAB of 10.5,9.2,and 13.9 GHz at 2,3,and 4 mm,respectively.The significance of this study lays on realizing ultra-broadband capacity in HE TMC-3(Cr,Zr,Hf,Nb,Ta),demonstrating the effectiveness of high-entropy component design in tailoring the impedance match.
基金supported by the PhD Start-up Fund of Science and Technology Department of Liaoning Province(No.2022-BS-306)the General Cultivation Scientific Research Project of Bohai University(No.0522xn058)the PhD Research Startup Foundation of Bohai University(No.0521bs021).
文摘The key to solve increasingly severe electromagnetic(EM)pollution is to explore sustainable,easily prepared,and cost-effective EM wave absorption materials with exceptional absorption capability.Herein,instead of anchoring on carbon materials in single layer,MoS_(2) flower-like microspheres were stacked on the surface of pomelo peels-derived porous carbon nanosheets(C)to fabricate MoS_(2)@C nanocomposites by a facile solvothermal process.EM wave absorption performances of MoS_(2)@C nanocomposites in X-band were systematically investigated,indicating the minimum reflection loss(RLmin)of-62.3 dB(thickness of 2.88 mm)and effective absorption bandwidth(EAB)almost covering the whole X-band(thickness of 2.63 mm)with the filler loading of only 20 wt.%.Superior EM wave absorption performances of MoS_(2)@C nanocomposites could be attributed to the excellent impedance matching characteristic and dielectric loss capacity(conduction loss and polarization loss).This study revealed that the as-prepared MoS_(2)@C nanocomposites would be a novel prospective candidate for the sustainable EM absorbents with superior EM wave absorption performances.
基金support from the National Natural Science Foundation of China (No.52072294)the Characteristic Development Guidance Funds for the Central Universities.
文摘SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching.Herein,we report ultralight SiC/Si3N4 composite aerogels(~15 mg·cm^(−3))consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons.Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method.The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss(RL,−48.6 dB)and a wide effective absorption band(EAB,7.4 GHz)at a thickness of 2 mm,attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure.In addition,the aerogel exhibits high thermal stability in air until 1000℃and excellent thermal insulation performance(0.030 W·m^(−1)·K^(−1)).These superior performances make the SiC/Si_(3)N_(4) composite aerogel promising to become a new generation of absorption material served under extreme conditions.
