Carbon-based electromagnetic wave(EMW)absorbing materials attached with metal sulfides famous for good dielectric properties are favored by researchers,which can form heterogeneous interfaces and thus provide suppleme...Carbon-based electromagnetic wave(EMW)absorbing materials attached with metal sulfides famous for good dielectric properties are favored by researchers,which can form heterogeneous interfaces and thus provide supplementary loss mechanisms to make up for the deficiencies of a single material in energy attenuation.Here,Co_(9)S_(8)/Co@coral-like carbon nanofibers(CNFs)/porous carbon hybrids are successfully fabricated by hydrothermal and chemical vapor deposition.The samples have exceptional EMW absorb-ing properties,with a minimum reflection loss of-57.48 dB at a thickness of 2.94 mm and an effective absorption bandwidth of up to 6.10 GHz at only 2.20 mm.The interlocking structure formed by Co@coral-like CNFs,interfacial polarization generated by heterostructure of Co_(9)S_(8),abundant defects and large specific surface area resulted from porous properties are important factors in attaining magnetic-dielectric balance and excellent absorption performance.Different matrixes are selected instead of paraffin to investigate the effect of matrix materials on EMW absorbing capacity.Besides,the EMW attenuation potential for practical applications is also demonstrated by radar cross-section simulations,electric field intensity distribution and power loss density.This work provides a novel strategy for designing outstanding EMW absorbers with unique microstructures using facile and low-cost synthetic routes.展开更多
Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface s...Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.展开更多
Abstract： PAN （Polyacrylonitrile）-based carbonaceous fibers were prepared at the heat treatment temperature （HTT） range of 650 to 900 ℃. The relationships among HTT, carbon content and volume resistivity of the ...Abstract： PAN （Polyacrylonitrile）-based carbonaceous fibers were prepared at the heat treatment temperature （HTT） range of 650 to 900 ℃. The relationships among HTT, carbon content and volume resistivity of the carbonaceous fibers were investigated. The carbonaceous fibers/PTFE （Polytetrafluoroethylene） antistatic coatings were prepared by the spraying technology and the effects of carbonaceous fibers and pigments on surface resistivity of the coatings were systematically discussed. Micrographs provide insight into the antistatic mechanism of the coating. The results show that carbon content of the carbonaceous fibers increases from 68.8% to 74.8% （mass fraction） and the volume resistivity decreases drastically from 1.94× 10^-3 to 8.27× 10 ^-2.cm. The surface resistivity of the antistatic coating is adjustable between 10^5 and 10^8Ω2 to fit the different antistatic materials. Static is dissipated by a conductive network of short fibers and the tunneling effect between the neighboring fibers and conductive pigments. Conductive pigments make the conductive network more perfect and improve the antistatic ability, but insulating pigments acting as barriers for the formation of conductive channel increases the surface resistivity of the coatings. The influence of pigments on the surface resistivity drops gradually with the decrease of the carbonaceous fibers volume resistivity.展开更多
The novel fabrication of multiple components and unique heterostructure can inject infinite vitality into the electromagnetic wave(EMW)attenuation field.Herein,through the self-assembly of polyimide com-plexes and cat...The novel fabrication of multiple components and unique heterostructure can inject infinite vitality into the electromagnetic wave(EMW)attenuation field.Herein,through the self-assembly of polyimide com-plexes and catalytic chemical vapor deposition,porous carbon microflowers were synthesized accompa-nied by carbon nanotubes(CNTs).By regulating the metal ions,the composition and structure of the as-obtained hybrids are modified correspondingly,and thus the adjustable thermal management and EMW absorption capabilities are obtained.In detail,the rich pores and huge specific surface area endow the hierarchical structures with distinguished thermal insulation ability(λ<0.07).The carbon framework and CNTs are beneficial for consuming EMWs via conductive loss and defect polarization loss while reduc-ing the filling ratio and thickness.The doped heteroatoms and abundant heterointerfaces generate ample dipole polarization and interface polarization losses(supported by DFT calculation).The metal nanopar-ticles uniformly embedded in the carbon framework offer optimized impedance matching,proper de-fect polarization,and suitable magnetic loss.Accordingly,the synergy of magnetic-dielectric balance and flower-like superstructure enables FNCFN2 and NNCFN2 to accomplish remarkable microwave absorbing capacity with thin thickness(14 wt.%).Therefore,respectable specific reflection loss and specific effec-tive absorption bandwidth are acquired(215.39 dB mm^(-1) and 22.10 GHz mm^(-1),257.23 dB mm^(-1) and 22.12 GHz mm^(-1) respectively),superior to those of certain renowned carbon-based absorbers.The simu-lation results of electric field intensity distributions,power loss density,and radar cross section reduction(maximum value of 36.02 dBm2)also verify the prominent radar stealth capability.Moreover,the cus-tomizable approach can be applied to other metals to obtain fulfilling behaviors.Henceforth,this work provides profound insights into the relationship between structure and performance,and proposes an efficient path for mass-producing multifunctional and high-performance EMW absorbers with excellent thermal properties.展开更多
Lithium(Li) metal anodes(LMAs) that employ three-dimensional lithiophilic frameworks are among the most promising options for constructing high-energy-density rechargeable batteries.Herein,hollow ZnS nanosheets with t...Lithium(Li) metal anodes(LMAs) that employ three-dimensional lithiophilic frameworks are among the most promising options for constructing high-energy-density rechargeable batteries.Herein,hollow ZnS nanosheets with the coating of N-doped carbon are modified on the surface of carbon cloth(NCHZS@CC) to serve as the host material for Li metal.It is revealed that the high surface area of NCHZS@CC can significantly reduce local current density and mitigate volume change during cycling.More importantly,the lithiated product of ZnS,confined within the carbon cage,facilitates the uniform deposition of Li metal on carbon fibers and promotes the formation of a stable solid electrolyte interphase enriched with Li_(2)S,thereby improving long-term performance as the cycling progresses.Consequently,the LMAs based on NCHZS@CC demonstrate an impressive cycle life beyond560 h with an ultralow overpotential of 38 mV at a current density of 5 mA cm^(-2)with a capacity of 1 mAh cm^(-2)in the symmetric cell.In addition,when matched with a high mass loading cathode of LiFePO_(4)(11.5 mg cm^(-2)),the assembled full cell displays outstanding performance,achieving 900 cycles at a rate of 2C.展开更多
Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powde...Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powders were self-assembled and anchored onto the aerogel framework,followed by the deposition of carbon nanotubes(CNTs)via catalytic chemical vapor deposition,yielding MIL-88C/CuCo_(2)S_(4)-derived bamboo-like CNTs/carbon nanofiber aerogels(FCC@CC series).By modulating component loading ratios,the formation of a three-dimensional conduction network,the presence of heterogeneous interfaces,enhanced magnetic loss,and engineered defects synergistically optimized dielectric and magnetic loss.This adjustment improved the impedance matching of the composite carbon aerogel,resulting in exceptional EMW absorption performance.The FCC@CC2 sample achieved a minimum reflection loss of−71.15 dB and an effective absorption bandwidth of 6.10 GHz.CST simulations further demonstrated the practical applicability,showing a maximum radar cross-section reduction of 34.92 dB·m^(2).Power loss density and electric field distribution analyses corroborated the superior electromagnetic attenuation capabilities of the FCC@CC.This work establishes a methodology for developing lightweight multifunctional aerogels with pressure resistance,thermal insulation,and infrared stealth properties,providing a novel strategy for the fabrication of microwave absorbers for use under complex conditions.展开更多
In the microelectronics era,electromagnetic radiation and thermal accumulation from electronic devices can detrimentally impact sensor performance and seriously damage human health.Despite the pressing need,synthesizi...In the microelectronics era,electromagnetic radiation and thermal accumulation from electronic devices can detrimentally impact sensor performance and seriously damage human health.Despite the pressing need,synthesizing high-performance multifunctional composite remains a formidable challenge.Herein,we report the fabrication of heterostructured carbon fiber(CF)@SnO_(2)nanosheet using CF as a template,followed by activation pretreatment,hydrothermal in-situ growth,and sulfur-oxygen substitution.This approach yielded CF reinforced polyether ether ketone(CF/PEEK)composites with enhanced interfacial performances,exceptional electromagnetic interference(EMI)shielding effectiveness,and high thermal conductivity(TC).The interlaminar shear strength(ILSS)of the composite achieved a remarkable 87.86 MPa,underscoring the robust interfacial integration that significantly bolsters EMI shielding and TC.As a result,the composite demonstrated a notable enhancement in EMI shielding effectiveness and TC by 22.85%and 52.83%,respectively.The strategy of integrating structural and functional elements is instrumental in the advancement of innovative high-performance multifunctional composite.These composites are poised to serve not only as critical structural components in aerospace applications but also to extend their utility into the realm of precision electronics,offering a promising horizon for future technological innovations.展开更多
Carbon fiber(CF)has emerged as a promising candidate for microwave absorbers to resolve the escalating electromagnetic wave(EMW)pollution issue,not just serving as a structural reinforcement.However,the drawbacks,such...Carbon fiber(CF)has emerged as a promising candidate for microwave absorbers to resolve the escalating electromagnetic wave(EMW)pollution issue,not just serving as a structural reinforcement.However,the drawbacks,such as high conductivity,limit its ability to strongly absorb EMWs over a wide bandwidth.To address these challenges,graphite wrapped FeNi_(3)/Co with carbon nanotubes(CNTs)anchored on MgO@CF heterostructures were synthesized by introducing MgO nanofilms on a CF surface and subsequent chemical vapor deposition catalyzed by two-phase catalysts.The synthesis of MgO sup-presses the etching of CF during the experimental processes,effectively maintaining the inherent structure of CF,which is conducive to constructing rich conductive networks and developing excellent mechanical properties.By modulating the catalyst concentration,deposited CNTs with appropriate defects increase the conduction loss and stimulate defect polariza-tion loss.The abundant interfaces formed by multiple components lead to fulfilling interface polarization,while the doping of O heteroatoms causes dipole polarization.In addition,the introduction of FeNi_(3)/Co generates effective magnetic loss and optimizes electromagnetic parameters to form more matching impedance conditions.At a low filler loading of 23 wt%,the stable sample obtains a remarkable minimum reflection loss of up to-72.08 dB at merely 1.38 mm with an effective absorption bandwidth reaching 4.88 GHz at only 1.44 mm,which is superior to that of numerous distinguished carbon-based composites in regard to being“thin,light,wide and strong”.CST simulation reveals that the maximum radar cross section reduction acquires 26.88 dBm2,ascertaining the radar stealth capability of the distinctive heterostructure.Moreover,great mechanical and electromagnetic interference shielding performance is demonstrated by epoxy composites.Henceforth,this study proposes profound insights into the intricate relationship between the structure and EMW absorbing mechanism,and elucidates an attractive strategy for mass-producing modified CF-based hybrids for versatile applications.展开更多
The exploitation of antennas with both electromagnetic stealth and efficient power transmission is of great significance in the information age.Therefore,from the perspective of multi-component composite and microtopo...The exploitation of antennas with both electromagnetic stealth and efficient power transmission is of great significance in the information age.Therefore,from the perspective of multi-component composite and microtopography engineering,Ni/C@ZrO_(2) ternary nanofibers are synthesized through electrospinning and subsequent carbonization.Profiting from the reasonable selection of components and exquisite micro-structure,the synergistic effect is fully developed,with the simultaneous achievement of perfect impedance matching and superior attenuation capacity.Precisely speaking,compared with carbon nanofibers and binary nanofibers,Ni/C@ZrO_(2) exhibits the minimum reflection loss values of−60.1 dB at 11.0 GHz,an ultrawide bandwidth up to 7.6 GHz at 3.3 mm,and radar cross-section values less than−20 dBm^(2) at most observation angles.A patch antenna with Ni/C@ZrO_(2) acted as dielectric substrate is designed and displays efficient transmission efficiency,which means the theoretical feasibility of research on stealthy information transmission equipment,and enhances the competitiveness in comparison with other absorbent candidates.Hence,this study successfully prepares a high-performance electromagnetic wave absorbent,and sheds light on the future development of fibrous functional materials.展开更多
Electromagnetic interference(EMI)shielding materials principally attain shielding by reflecting electromagnetic waves through impedance mismatch caused by high conductivity,which inevitably leads to secondary electrom...Electromagnetic interference(EMI)shielding materials principally attain shielding by reflecting electromagnetic waves through impedance mismatch caused by high conductivity,which inevitably leads to secondary electromagnetic wave pollution.Consequently,the development of multifunctional,low-reflection electromagnetic shielding materials remains a significant challenge.Materials that are lightweight,possess high mechanical strength,exhibit excellent electromagnetic shielding absorption,and demonstrate low reflectivity have historically been the focus of significant interest.Natural silk,lightweight and strong,is an ideal composite matrix.Regenerated silk fibroin(RSF)synthesized via a bottom-up approach and cross-linked with polyvinyl alcohol(PVA)forms an aerogel matrix with remarkable compressive strength.In accordance with the principle of integrating functional design with structural design,spherical NiFe_(2)O_(4)particles were grown on the MXene surface via electrostatic self-assembly and combined with RSF/PVA as the aerogel absorptive layer,while RSF/PVA/MXene served as the reflective layer.A vertically oriented structure of Janus aerogel was prepared through sequential directed freezing.The resulting aerogel with 0.058 g/cm^(3) reveals the high compression strength(3.52 MPa).Reasonable functional and structural design enables aerogel to effectively dissipate incident electromagnetic waves through absorption,reflection,and reabsorption processes,achieving an average SET value of 48.05±1.75 dB and reaching a minimum reflection coefficient of 0.19.Furthermore,the aerogel displays remarkable infrared stealth capabilities.This lightweight,rigid,multifunctional aerogel is poised to play a significant role in the field of next-generation electronic devices.展开更多
Polyacrylonitrile(PAN)fiber is an important precursor fiber for high performance carbon fiber.The properties of the final carbon fiber depend strongly on the nature of the PAN fibers.The PAN fibrils were separated suc...Polyacrylonitrile(PAN)fiber is an important precursor fiber for high performance carbon fiber.The properties of the final carbon fiber depend strongly on the nature of the PAN fibers.The PAN fibrils were separated successfully from fibers by ultrasonic etching and were systematically investigated by field emission scanning electron microscopy(FESEM)and high resolution transmission electron microscopy(HRTEM).It is found that in certain ultrasonic etching conditions(at 75±2oC for 6 h with a frequency of 40 kHz)the PAN fibers are dissolved in the 95 wt.%aqueous dimethylsulphoxide(DMSO)solution;the fibrils consisting of numerous periodic lamellae with thickness of 30-45 nm and perpendicular to the fiber axis are separated in the 90 wt.%aqueous DMSO solution;and the fibrils with smooth surface exfoliated from the PAN fibers are obtained in the 70-90 wt.%aqueous DMSO solutions.Inner periodical structure of fibrils was observed in HRTEM,which indicates that there are different densities and two phases in fibrils.The PAN fibers are dissolved layer by layer with increasing ultrasonic etching time.The fiber surface experiences ultrasonic cleaning,selective etching,excessive etching and dissolution,and then the sublayer experiences the same process.There are numerous periodic lamellae in fibrils of nascent fibers.This means that the fibrils with lamellae are formed by orientation and crystallization in shearing field of spinning pipe and drawing stress field of coagulation bath.展开更多
Refining the electromagnetic wave absorption characteristics of traditional metal–organic framework(MOF)-derived carbon composites remains a challenge because of their discontinuous conductive path.To overcome this l...Refining the electromagnetic wave absorption characteristics of traditional metal–organic framework(MOF)-derived carbon composites remains a challenge because of their discontinuous conductive path.To overcome this limitation,in this work,MOF-derived hierarchical Cu_(9)S_(5)/C nanocomposite fibers are fabricated by electrospinning and subsequent carbonization-sulfurization process.Morphological analyses show that MOF-derived octahedral Cu_(9)S_(5)/C particles are evenly monodis-persed inside carbonaceous fibers.This configuration creates a unique hierarchical structure,ranging from Cu_(9)S_(5)particle embedding,MOF-derived skeleton,to a three-dimensional network.The optimized composite fibers(Cu_(9)S_(5)/C-40)exhibit extraordinary electromagnetic wave absorption performance at a low mass fraction(20 wt%):the minimum reflection loss value reaches-69.6 dB,and the maximum effective absorption bandwidth achieves 5.81 GHz with an extremely thin thick-ness of only 1.83 mm.Systematic investigations demonstrate that constructing the three-dimensional conductive network to connect MOF derivatives is crucial for activating performance enhancement.The unique nano-micro hierarchical structure synergized with elaborate-configured components endows the materials with optimal impedance matching and amplifies the loss capacity of each part.This work provides a reliable example and theoretical guidance for fabricating new-generation high-efficiency MOF-derived fibrous electromagnetic wave absorbers.展开更多
Stimuli-responsive materials with switchable wettability have promising practical applications in oil/water separation.A novel CO_(2)-responsive cotton fabric for controlled oil/water separation was fabricated based o...Stimuli-responsive materials with switchable wettability have promising practical applications in oil/water separation.A novel CO_(2)-responsive cotton fabric for controlled oil/water separation was fabricated based on mussel-inspired reaction and polymerized with 2-(dimethylamino)ethyl methacrylate(DMAEMA).As expected,the modified fabric exhibited switchable hydrophilicity and hydrophobicity after CO_(2)/N_(2)alternation,and it could be used for gravity-driven CO_(2)-controlled oil/water separation.Water was selectively penetrated through the fabric and separated from oil after treating by CO_(2).A reversed wettability could be generated through simply treated with N2.It is expected that the as-prepared fabrics could be applied in smart oil/water separation due to the attractive properties of CO_(2)-switchable system.展开更多
Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyanili...Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyaniline.It was discovered that KOH acted as porogen and had an etching-bridging-reaction effect during the activation process.As a microwave absorber,the composite/paraffin with a filler loading of 16 wt%reaches a minimum reflection loss of−52.8 dB and an effective absorption bandwidth of 4.72 GHz.Moreover,microwave absorption can be maintained within 45 days in air.Compared with untreated MXene,the absorber shows long-term functional stability in an oxygen-containing environment.As for electromagnetic interference shielding,the composite/paraffin at a filler loading of 50 wt%achieves 30.5 dB from 8.0 to 12.4 GHz.Additionally,the heterostructure delivers a desirable specific capacitance of 1,096.3 F g^(−1) at 0.5 A g^(−1).The trifunctional characteristics enrich the application trials of MXene derivatives and satisfy the strong need for versatile materials.展开更多
基金financially supported by the Natural Science Foundation of Shandong Province(Nos.ZR2021ME194,2022TSGC2448,and 2023TSGC0545)the Key Technology Research and Development Program of Shandong Province(No.2021ZLGX01).
文摘Carbon-based electromagnetic wave(EMW)absorbing materials attached with metal sulfides famous for good dielectric properties are favored by researchers,which can form heterogeneous interfaces and thus provide supplementary loss mechanisms to make up for the deficiencies of a single material in energy attenuation.Here,Co_(9)S_(8)/Co@coral-like carbon nanofibers(CNFs)/porous carbon hybrids are successfully fabricated by hydrothermal and chemical vapor deposition.The samples have exceptional EMW absorb-ing properties,with a minimum reflection loss of-57.48 dB at a thickness of 2.94 mm and an effective absorption bandwidth of up to 6.10 GHz at only 2.20 mm.The interlocking structure formed by Co@coral-like CNFs,interfacial polarization generated by heterostructure of Co_(9)S_(8),abundant defects and large specific surface area resulted from porous properties are important factors in attaining magnetic-dielectric balance and excellent absorption performance.Different matrixes are selected instead of paraffin to investigate the effect of matrix materials on EMW absorbing capacity.Besides,the EMW attenuation potential for practical applications is also demonstrated by radar cross-section simulations,electric field intensity distribution and power loss density.This work provides a novel strategy for designing outstanding EMW absorbers with unique microstructures using facile and low-cost synthetic routes.
基金supported by the National Basic Research Program of China (No. 2011CB605602)
文摘Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.
基金Project(2011CB605601)supported by the National Basic Research Program(973 Program)of ChinaProject(50902088)supported by the National Natural Science Foundation of China+1 种基金Project(ZR2011EMM002)supported by the Natural Science Foundation in Shandong Province,ChinaProject(2009AA035301)supported by the National High Technology Research and Development Program(863 Program)of China
文摘Abstract： PAN （Polyacrylonitrile）-based carbonaceous fibers were prepared at the heat treatment temperature （HTT） range of 650 to 900 ℃. The relationships among HTT, carbon content and volume resistivity of the carbonaceous fibers were investigated. The carbonaceous fibers/PTFE （Polytetrafluoroethylene） antistatic coatings were prepared by the spraying technology and the effects of carbonaceous fibers and pigments on surface resistivity of the coatings were systematically discussed. Micrographs provide insight into the antistatic mechanism of the coating. The results show that carbon content of the carbonaceous fibers increases from 68.8% to 74.8% （mass fraction） and the volume resistivity decreases drastically from 1.94× 10^-3 to 8.27× 10 ^-2.cm. The surface resistivity of the antistatic coating is adjustable between 10^5 and 10^8Ω2 to fit the different antistatic materials. Static is dissipated by a conductive network of short fibers and the tunneling effect between the neighboring fibers and conductive pigments. Conductive pigments make the conductive network more perfect and improve the antistatic ability, but insulating pigments acting as barriers for the formation of conductive channel increases the surface resistivity of the coatings. The influence of pigments on the surface resistivity drops gradually with the decrease of the carbonaceous fibers volume resistivity.
基金supported by the Natural Science Foundation of Shandong Province(Nos.ZR2021ME194,2022TSGC2448,and 2023TSGC0545)the Key Technology Research and Development Program of Shandong Province(No.2021ZLGX01).
文摘The novel fabrication of multiple components and unique heterostructure can inject infinite vitality into the electromagnetic wave(EMW)attenuation field.Herein,through the self-assembly of polyimide com-plexes and catalytic chemical vapor deposition,porous carbon microflowers were synthesized accompa-nied by carbon nanotubes(CNTs).By regulating the metal ions,the composition and structure of the as-obtained hybrids are modified correspondingly,and thus the adjustable thermal management and EMW absorption capabilities are obtained.In detail,the rich pores and huge specific surface area endow the hierarchical structures with distinguished thermal insulation ability(λ<0.07).The carbon framework and CNTs are beneficial for consuming EMWs via conductive loss and defect polarization loss while reduc-ing the filling ratio and thickness.The doped heteroatoms and abundant heterointerfaces generate ample dipole polarization and interface polarization losses(supported by DFT calculation).The metal nanopar-ticles uniformly embedded in the carbon framework offer optimized impedance matching,proper de-fect polarization,and suitable magnetic loss.Accordingly,the synergy of magnetic-dielectric balance and flower-like superstructure enables FNCFN2 and NNCFN2 to accomplish remarkable microwave absorbing capacity with thin thickness(14 wt.%).Therefore,respectable specific reflection loss and specific effec-tive absorption bandwidth are acquired(215.39 dB mm^(-1) and 22.10 GHz mm^(-1),257.23 dB mm^(-1) and 22.12 GHz mm^(-1) respectively),superior to those of certain renowned carbon-based absorbers.The simu-lation results of electric field intensity distributions,power loss density,and radar cross section reduction(maximum value of 36.02 dBm2)also verify the prominent radar stealth capability.Moreover,the cus-tomizable approach can be applied to other metals to obtain fulfilling behaviors.Henceforth,this work provides profound insights into the relationship between structure and performance,and proposes an efficient path for mass-producing multifunctional and high-performance EMW absorbers with excellent thermal properties.
基金financial supports from the National Natural Science Foundation of China(Nos.22279116 and U20A20253)the Natural Science Foundation of Zhejiang Province(Nos.LQ24E020012 and LD22E020006)Jianbing Science and Technology Project of Zhejiang Province(No.2023C01127)
文摘Lithium(Li) metal anodes(LMAs) that employ three-dimensional lithiophilic frameworks are among the most promising options for constructing high-energy-density rechargeable batteries.Herein,hollow ZnS nanosheets with the coating of N-doped carbon are modified on the surface of carbon cloth(NCHZS@CC) to serve as the host material for Li metal.It is revealed that the high surface area of NCHZS@CC can significantly reduce local current density and mitigate volume change during cycling.More importantly,the lithiated product of ZnS,confined within the carbon cage,facilitates the uniform deposition of Li metal on carbon fibers and promotes the formation of a stable solid electrolyte interphase enriched with Li_(2)S,thereby improving long-term performance as the cycling progresses.Consequently,the LMAs based on NCHZS@CC demonstrate an impressive cycle life beyond560 h with an ultralow overpotential of 38 mV at a current density of 5 mA cm^(-2)with a capacity of 1 mAh cm^(-2)in the symmetric cell.In addition,when matched with a high mass loading cathode of LiFePO_(4)(11.5 mg cm^(-2)),the assembled full cell displays outstanding performance,achieving 900 cycles at a rate of 2C.
基金supported by the Natural Science Foundation of Shandong Province(Nos.2024TSGC0550,2023TSGC0545,and 2023TATSGC025)Key Technology Research and Development Program of Shandong Province(No.2021ZLGX01)The authors would like to thank Conghua Qi from Shiyanjia Lab(www.shiyanjia.com)for TEM test.The scientific calculations in this paper have been done on the HPC Cloud Platform of Shandong University.
文摘Multifunctional carbon aerogels have garnered significant attention due to their promising applications in thermal insulation and electromagnetic wave(EMW)absorption.In this study,MIL-88C/CuCo_(2)S_(4) composite powders were self-assembled and anchored onto the aerogel framework,followed by the deposition of carbon nanotubes(CNTs)via catalytic chemical vapor deposition,yielding MIL-88C/CuCo_(2)S_(4)-derived bamboo-like CNTs/carbon nanofiber aerogels(FCC@CC series).By modulating component loading ratios,the formation of a three-dimensional conduction network,the presence of heterogeneous interfaces,enhanced magnetic loss,and engineered defects synergistically optimized dielectric and magnetic loss.This adjustment improved the impedance matching of the composite carbon aerogel,resulting in exceptional EMW absorption performance.The FCC@CC2 sample achieved a minimum reflection loss of−71.15 dB and an effective absorption bandwidth of 6.10 GHz.CST simulations further demonstrated the practical applicability,showing a maximum radar cross-section reduction of 34.92 dB·m^(2).Power loss density and electric field distribution analyses corroborated the superior electromagnetic attenuation capabilities of the FCC@CC.This work establishes a methodology for developing lightweight multifunctional aerogels with pressure resistance,thermal insulation,and infrared stealth properties,providing a novel strategy for the fabrication of microwave absorbers for use under complex conditions.
基金support from the Major Basic Research Project of Natural Science Foundation of Shandong Province(No.ZR2021ZD21)Key Research and Development Plan of Shandong Province(No.2021ZLGX01)+1 种基金National Natural Science Foundation of China for Youths(No.52203264)Natural Science Foundation of Shandong Province for Youths(No.ZR2021QE113).
文摘In the microelectronics era,electromagnetic radiation and thermal accumulation from electronic devices can detrimentally impact sensor performance and seriously damage human health.Despite the pressing need,synthesizing high-performance multifunctional composite remains a formidable challenge.Herein,we report the fabrication of heterostructured carbon fiber(CF)@SnO_(2)nanosheet using CF as a template,followed by activation pretreatment,hydrothermal in-situ growth,and sulfur-oxygen substitution.This approach yielded CF reinforced polyether ether ketone(CF/PEEK)composites with enhanced interfacial performances,exceptional electromagnetic interference(EMI)shielding effectiveness,and high thermal conductivity(TC).The interlaminar shear strength(ILSS)of the composite achieved a remarkable 87.86 MPa,underscoring the robust interfacial integration that significantly bolsters EMI shielding and TC.As a result,the composite demonstrated a notable enhancement in EMI shielding effectiveness and TC by 22.85%and 52.83%,respectively.The strategy of integrating structural and functional elements is instrumental in the advancement of innovative high-performance multifunctional composite.These composites are poised to serve not only as critical structural components in aerospace applications but also to extend their utility into the realm of precision electronics,offering a promising horizon for future technological innovations.
基金supported by the Natural Science Foundation of Shandong Prov-ince(ZR2021ME194,2022TSGC2448,2023TSGC0545)the Key Technology Research and Development Program of Shandong Province(2021ZLGX01).
文摘Carbon fiber(CF)has emerged as a promising candidate for microwave absorbers to resolve the escalating electromagnetic wave(EMW)pollution issue,not just serving as a structural reinforcement.However,the drawbacks,such as high conductivity,limit its ability to strongly absorb EMWs over a wide bandwidth.To address these challenges,graphite wrapped FeNi_(3)/Co with carbon nanotubes(CNTs)anchored on MgO@CF heterostructures were synthesized by introducing MgO nanofilms on a CF surface and subsequent chemical vapor deposition catalyzed by two-phase catalysts.The synthesis of MgO sup-presses the etching of CF during the experimental processes,effectively maintaining the inherent structure of CF,which is conducive to constructing rich conductive networks and developing excellent mechanical properties.By modulating the catalyst concentration,deposited CNTs with appropriate defects increase the conduction loss and stimulate defect polariza-tion loss.The abundant interfaces formed by multiple components lead to fulfilling interface polarization,while the doping of O heteroatoms causes dipole polarization.In addition,the introduction of FeNi_(3)/Co generates effective magnetic loss and optimizes electromagnetic parameters to form more matching impedance conditions.At a low filler loading of 23 wt%,the stable sample obtains a remarkable minimum reflection loss of up to-72.08 dB at merely 1.38 mm with an effective absorption bandwidth reaching 4.88 GHz at only 1.44 mm,which is superior to that of numerous distinguished carbon-based composites in regard to being“thin,light,wide and strong”.CST simulation reveals that the maximum radar cross section reduction acquires 26.88 dBm2,ascertaining the radar stealth capability of the distinctive heterostructure.Moreover,great mechanical and electromagnetic interference shielding performance is demonstrated by epoxy composites.Henceforth,this study proposes profound insights into the intricate relationship between the structure and EMW absorbing mechanism,and elucidates an attractive strategy for mass-producing modified CF-based hybrids for versatile applications.
基金Acknowledgements The authors would like to acknowledge the financial supports from the key research and development program of Shandong Province(Grant No.2021ZLGX01,2021CXGC010903)Natural Science Foundation of Shandong Province(ZR2022ME055).
文摘The exploitation of antennas with both electromagnetic stealth and efficient power transmission is of great significance in the information age.Therefore,from the perspective of multi-component composite and microtopography engineering,Ni/C@ZrO_(2) ternary nanofibers are synthesized through electrospinning and subsequent carbonization.Profiting from the reasonable selection of components and exquisite micro-structure,the synergistic effect is fully developed,with the simultaneous achievement of perfect impedance matching and superior attenuation capacity.Precisely speaking,compared with carbon nanofibers and binary nanofibers,Ni/C@ZrO_(2) exhibits the minimum reflection loss values of−60.1 dB at 11.0 GHz,an ultrawide bandwidth up to 7.6 GHz at 3.3 mm,and radar cross-section values less than−20 dBm^(2) at most observation angles.A patch antenna with Ni/C@ZrO_(2) acted as dielectric substrate is designed and displays efficient transmission efficiency,which means the theoretical feasibility of research on stealthy information transmission equipment,and enhances the competitiveness in comparison with other absorbent candidates.Hence,this study successfully prepares a high-performance electromagnetic wave absorbent,and sheds light on the future development of fibrous functional materials.
基金supported by Key R&D Program of Shandong Province,China(No.2025CXGC010407).
文摘Electromagnetic interference(EMI)shielding materials principally attain shielding by reflecting electromagnetic waves through impedance mismatch caused by high conductivity,which inevitably leads to secondary electromagnetic wave pollution.Consequently,the development of multifunctional,low-reflection electromagnetic shielding materials remains a significant challenge.Materials that are lightweight,possess high mechanical strength,exhibit excellent electromagnetic shielding absorption,and demonstrate low reflectivity have historically been the focus of significant interest.Natural silk,lightweight and strong,is an ideal composite matrix.Regenerated silk fibroin(RSF)synthesized via a bottom-up approach and cross-linked with polyvinyl alcohol(PVA)forms an aerogel matrix with remarkable compressive strength.In accordance with the principle of integrating functional design with structural design,spherical NiFe_(2)O_(4)particles were grown on the MXene surface via electrostatic self-assembly and combined with RSF/PVA as the aerogel absorptive layer,while RSF/PVA/MXene served as the reflective layer.A vertically oriented structure of Janus aerogel was prepared through sequential directed freezing.The resulting aerogel with 0.058 g/cm^(3) reveals the high compression strength(3.52 MPa).Reasonable functional and structural design enables aerogel to effectively dissipate incident electromagnetic waves through absorption,reflection,and reabsorption processes,achieving an average SET value of 48.05±1.75 dB and reaching a minimum reflection coefficient of 0.19.Furthermore,the aerogel displays remarkable infrared stealth capabilities.This lightweight,rigid,multifunctional aerogel is poised to play a significant role in the field of next-generation electronic devices.
基金supported by the National Natural Science Foundation of China(Grant No.50673052)the Major State Basic Research Development Program of China(973 Program)(Grant No.2006CB605314)the Provincial Natural Science Foundation of Shandong Province(Grant No.Z2008F02)
文摘Polyacrylonitrile(PAN)fiber is an important precursor fiber for high performance carbon fiber.The properties of the final carbon fiber depend strongly on the nature of the PAN fibers.The PAN fibrils were separated successfully from fibers by ultrasonic etching and were systematically investigated by field emission scanning electron microscopy(FESEM)and high resolution transmission electron microscopy(HRTEM).It is found that in certain ultrasonic etching conditions(at 75±2oC for 6 h with a frequency of 40 kHz)the PAN fibers are dissolved in the 95 wt.%aqueous dimethylsulphoxide(DMSO)solution;the fibrils consisting of numerous periodic lamellae with thickness of 30-45 nm and perpendicular to the fiber axis are separated in the 90 wt.%aqueous DMSO solution;and the fibrils with smooth surface exfoliated from the PAN fibers are obtained in the 70-90 wt.%aqueous DMSO solutions.Inner periodical structure of fibrils was observed in HRTEM,which indicates that there are different densities and two phases in fibrils.The PAN fibers are dissolved layer by layer with increasing ultrasonic etching time.The fiber surface experiences ultrasonic cleaning,selective etching,excessive etching and dissolution,and then the sublayer experiences the same process.There are numerous periodic lamellae in fibrils of nascent fibers.This means that the fibrils with lamellae are formed by orientation and crystallization in shearing field of spinning pipe and drawing stress field of coagulation bath.
基金supported by the Natural Science Foundation of Shandong Province(ZR2021ME194,2022TSGC2448,2023TSGC0545)the key research and development program of Shandong Province(2021ZLGX01).
文摘Refining the electromagnetic wave absorption characteristics of traditional metal–organic framework(MOF)-derived carbon composites remains a challenge because of their discontinuous conductive path.To overcome this limitation,in this work,MOF-derived hierarchical Cu_(9)S_(5)/C nanocomposite fibers are fabricated by electrospinning and subsequent carbonization-sulfurization process.Morphological analyses show that MOF-derived octahedral Cu_(9)S_(5)/C particles are evenly monodis-persed inside carbonaceous fibers.This configuration creates a unique hierarchical structure,ranging from Cu_(9)S_(5)particle embedding,MOF-derived skeleton,to a three-dimensional network.The optimized composite fibers(Cu_(9)S_(5)/C-40)exhibit extraordinary electromagnetic wave absorption performance at a low mass fraction(20 wt%):the minimum reflection loss value reaches-69.6 dB,and the maximum effective absorption bandwidth achieves 5.81 GHz with an extremely thin thick-ness of only 1.83 mm.Systematic investigations demonstrate that constructing the three-dimensional conductive network to connect MOF derivatives is crucial for activating performance enhancement.The unique nano-micro hierarchical structure synergized with elaborate-configured components endows the materials with optimal impedance matching and amplifies the loss capacity of each part.This work provides a reliable example and theoretical guidance for fabricating new-generation high-efficiency MOF-derived fibrous electromagnetic wave absorbers.
基金the financial support of the National Natural Science Foundation of China(Grant no.51703130)Zhejiang Provincial Natural Science Foundation of China(Grant no.LY18E080018)+1 种基金Shaoxing Public Welfare Project(Grant no.2017B70042)the International Science and Technology Cooperation Project of Shaoxing University(Grant no.2019LGGH1004).
文摘Stimuli-responsive materials with switchable wettability have promising practical applications in oil/water separation.A novel CO_(2)-responsive cotton fabric for controlled oil/water separation was fabricated based on mussel-inspired reaction and polymerized with 2-(dimethylamino)ethyl methacrylate(DMAEMA).As expected,the modified fabric exhibited switchable hydrophilicity and hydrophobicity after CO_(2)/N_(2)alternation,and it could be used for gravity-driven CO_(2)-controlled oil/water separation.Water was selectively penetrated through the fabric and separated from oil after treating by CO_(2).A reversed wettability could be generated through simply treated with N2.It is expected that the as-prepared fabrics could be applied in smart oil/water separation due to the attractive properties of CO_(2)-switchable system.
基金supported by the Natural Science Foundation of Shandong Province(ZR2021ME194,2022TSG-C2448,and 2023TSGC0545)the Key Research and Dev-elopment Program of Shandong Province(2021ZLGX01).
文摘Enormous endeavors have been made to cope with microwave pollution and energy crisis.Here,porous nitrogen-doped C/TiO_(2) composites with absorption/shielding/supercapacitor functions were derived from MXene/polyaniline.It was discovered that KOH acted as porogen and had an etching-bridging-reaction effect during the activation process.As a microwave absorber,the composite/paraffin with a filler loading of 16 wt%reaches a minimum reflection loss of−52.8 dB and an effective absorption bandwidth of 4.72 GHz.Moreover,microwave absorption can be maintained within 45 days in air.Compared with untreated MXene,the absorber shows long-term functional stability in an oxygen-containing environment.As for electromagnetic interference shielding,the composite/paraffin at a filler loading of 50 wt%achieves 30.5 dB from 8.0 to 12.4 GHz.Additionally,the heterostructure delivers a desirable specific capacitance of 1,096.3 F g^(−1) at 0.5 A g^(−1).The trifunctional characteristics enrich the application trials of MXene derivatives and satisfy the strong need for versatile materials.
