Currently,the develop-ment of low-reflection electromagnetic interference(EMI)shielding composite materials for mitigating secondary electromagnetic wave pollution has become a major research focus.However,achieving t...Currently,the develop-ment of low-reflection electromagnetic interference(EMI)shielding composite materials for mitigating secondary electromagnetic wave pollution has become a major research focus.However,achieving thinness,high toughness,low reflectivity,and multi-functionality in flexible EMI shielding films remains a challenge.To address this issue,this study introduces a“magnetic-electric”Janus structure EMI shielding composite film composed of MXene nanosheets,carbonized ZIF-67(CZIF67)nanop-articles and aramid nanofibers(ANF),balancing thinness,high toughness,low reflectivity,and multifunctionality.As a result,the MXene/ANF-CZIF67/ANF-4(MACA-4)sample exhibits high tensile strength(110.0±7.0 MPa),large strain tolerance(21%),and superior toughness(14.9±0.9 MJ·m^(-3)),reflecting the stress dispersion effect of the three-dimensional(3D)network structure of ANF and the strengthening effect of hydrogen bonding.The sample exhibits excellent flexibility,resistance to rubbing and folding.Even with a thickness of only 80μm,the MACA-4 film exhibits a reflection performance(SER)as low as 4.3 to 4.5 dB in the 8.2 to 9.6 GHz band and the SE_(T)in the X-band reaches 44.8 dB.In addition,the superior conductivity of the MXene/ANF layer and the localized surface plasmon resonance effect give the MACA composite films excellent electrothermal conversion capabilities.Surprisingly,the sample also exhibited excellent infrared stealth and fire alarm properties.This work offers valuable guidance on the fabrication of ultra-thin flexible EMI shielding composites and provides an important scientific basis for the design and application of efficient EMI shielding materials.展开更多
Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fif...Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.展开更多
The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials...The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials with minimum EM waves(EMW)reflection.In this paper,Ag nanoparticles loaded mesoporous carbon hollow spheres(MCHS@Ag)were synthesized by chemical reduction method,and cellulose nanofibers(CNF)/MXene/MCHS@Ag homogeneous composites were prepared.The total EM interference shielding efficiency(SET)of CNF/MXene/MCHS@Ag composite film was 32.83 dB(at 12.4 GHz),and the absorption effectiveness(SEA)was improved to 26.6 dB,which was 63.1%and 195.5%higher than that of CNF/MXene/MCHS composite film.The low dielectric property of MCHS effectively optimized the impedance matching between the composites and air.The hollow porous structure prolonged the transmission path of EMW and increased the absorption loss of the composites.At the same time,Ag nanoparticles located the MCHS were helpful to construct the internal conductive path overcoming the damage of the conductive property caused by the low dielectric of MCHS.This research adopts a straightforward method to construct a lightweight,pliable,and mesoporous composites for EMI shielding,which serves a crucial role in the current era of severe EM pollution.展开更多
Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,...Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.展开更多
In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
The Belle Corporation is a Chinese domestic shoe maker and seller. It also belongs to an industry that has come to be representative of the ubiquitous "Made in China" label. One of the main reasons the compa...The Belle Corporation is a Chinese domestic shoe maker and seller. It also belongs to an industry that has come to be representative of the ubiquitous "Made in China" label. One of the main reasons the company is favored by global investors is due to its unique business pattern-a pattern that sets manufacturing as its base and is active in exploring industrial chain downstream links and establishing its own individual retail channels. Ever since its first inception in the stock market, Belle has set out to acquire several upstream manufacturing companies, indicating its desire for increasing channel terminals. Using a vertically integrated competition strategy, Belle stands out amongst its rivals as being particularly successful in the non-mainstream manufacturing sector. Consequently, its business practices can be used as a model for other domestic manufacturing companies in their efforts to meet the challenges posed by globalization.展开更多
The conductive polymer composites(CPCs) with highly efficient electromagnetic interference(EMI)shielding effectiveness(SE) are always accompanied with excessive reflectivity, which would cause serious secondary EMI po...The conductive polymer composites(CPCs) with highly efficient electromagnetic interference(EMI)shielding effectiveness(SE) are always accompanied with excessive reflectivity, which would cause serious secondary EMI pollution. In this regard, the significant reduction of EMI reflection of CPCs to alleviate secondary pollution is deemed to be very important. Herein, a promising cyanate ester(CE) based composite was successfully fabricated by compounding carbonized spent coffee grounds(C-SCG) and graphene nanosheets(GNSs) via a facile solution blending followed by a hot-pressing method. Benefiting from the porous structure of C-SCG and the layered structure of GNSs, a three-dimensional(3 D)multi-interface conductive network in the CE was easily constructed. The EMI SE of the resultant 9 wt%C-SCG/CE composite(C9) is 15.38 d B and dramatically enhanced to 31.09 d B with the presence of 3 wt% GNSs. The remarkable enhancement is mainly attributed to the formation of the efficient conductive pathways as well as the well-dispersion of the incorporated fillers. Meanwhile, the absorption-dominated shielding mechanism in the prepared composites gets benefit from the synergistic effect of porous C-SCG and lamellar GNSs, which effectively captures and attenuates electromagnetic waves. These encouraging findings extend the practical applications of porous biocarbon materials in EMI shielding field.展开更多
Researching and manufacturing materials that possess both electromagnetic interference(EMI)shielding and infrared stealth capabilities is of great significance.Herein,an ultrathin polyimide-based nonwoven fabric with ...Researching and manufacturing materials that possess both electromagnetic interference(EMI)shielding and infrared stealth capabilities is of great significance.Herein,an ultrathin polyimide-based nonwoven fabric with low-reflection EMI shielding/infrared stealth performance is successfully fabricated by in-situ loading of Fe_(3)O_(4)/Ag nanoparticles on the surface of polyimide(PI)fiber(PFA),and followed by bonding with a commercial Cu/Ni mesh.The synergistic assembly of PFA and Cu/Ni promotes the rational construction of hierarchical impedance matching,inducing electromagnetic waves(EMW)to enter the composite and be dissipated as much as possible.Meanwhile,the existence of Cu/Ni mesh on back of PFA facilitates the formation of electromagnetic resonance and destructive interference of EMW reflected from composite,leading to a lowerreflectivity(0.26)EMI shielding performance of 58 dB within 24–40 GHz at a thinner thickness(430μm).More importantly,the fluffy PFA nonwoven fabric and metal Cu/Ni mesh endow composite with good thermal insulation and low infrared emissivity,resulting in excellent infrared stealth performance in various environments.As a result,such excellent compatibility makes it possible to become a promising defense material to be applied in military tent for preventing electromagnetic and infrared radiation.展开更多
The multiplexing ability of a novel multiplexing fiber Bragg grating （FBG） method based on Optical Time Domain Reflecto meter （OTDR） and Time Division Multiplexing TDM technologies has been theoretically analyzed ...The multiplexing ability of a novel multiplexing fiber Bragg grating （FBG） method based on Optical Time Domain Reflecto meter （OTDR） and Time Division Multiplexing TDM technologies has been theoretically analyzed and studied. This method permits the interrogation of hundreds of identical FBGs with low reflectivity in a single fiber, making the FBG sensors more applicable in the aerospace health monitoring engineering. The analysis shows that the multiplexing ability can be greatly improved if the FBG reflectivity is sufficiently low. And hence, an inexpensive large-scale distributed sensing system based on this method can be realized, When evaluating the multiplexing ability of this system, we propose for the first time that the interference effect of multi-reflections among FBGs should be taken into consideration.展开更多
Traditional electromagnetic shielding materials primarily enhance reflection and absorption losses by increasing conductivity.While this approach improves shielding effectiveness,it also leads to issues such as impeda...Traditional electromagnetic shielding materials primarily enhance reflection and absorption losses by increasing conductivity.While this approach improves shielding effectiveness,it also leads to issues such as impedance mismatch,increased surface reflectivity,and irreversible secondary electromagnetic pollution.Consequently,the development of environmentally friendly electromagnetic interference(EMI)shielding materials with high efficiency and low reflectivity has become a key focus of research.This review examines the critical evaluation criteria and factors that influence the performance and reflectivity of EMI shielding materials.It also highlights recent advances in material tuning mechanisms and structural design strategies for the development of low-reflectivity,sustainable EMI shielding materials.By integrating material and structural design considerations,this review provides a comprehensive overview of strategies for constructing polymer-based low-reflectivity shielding materials,identifies persistent challenges in material design,and discusses future research directions in this field.展开更多
Absorption-dominated electromagnetic interference(EMI)shielding fabrics are urgently needed to address the increasingly severe electromagnetic radiation pollution,especially the secondary radiation problem.In this stu...Absorption-dominated electromagnetic interference(EMI)shielding fabrics are urgently needed to address the increasingly severe electromagnetic radiation pollution,especially the secondary radiation problem.In this study,we design novel core-sheath CNT@MXene fibers with a gradient conductive structure and corresponding fabrics to realize absorption-dominated EMI shielding performances.This coaxial structure utilizes carbon nanotubes(CNTs)as the sheath and MXene as the core and is constructed through a wet spinning technique.By virtue of the core-sheath structure,the conductive gradient structure in the fibers is easily optimized by adjusting the core MXene and sheath CNT content.This gradient conductive network of fiber effectively facilitates the incidence of electromagnetic waves and strong interactions between electromagnetic waves and the composites,resulting in excellent EMI absorption ability.Within the X-band frequency range,the fabric exhibits an electromagnetic interference shielding effectiveness of 23.40 dB and an absorption coefficient of 0.63.Due to the protection of polymer,the fiber’s electrical conductivity remains stable under conditions such as multi-cycle bending,stretching,and ultrasonic treatment,and in high relative humidity environments.Additionally,the fabric also demonstrates EMI shielding stability in indoor environments.This work indicates the great potential of the gradient structured fibers to achieve an absorption-dominated mechanism for next-generation eco-friendly EMI shielding fabrics.展开更多
The development of multifunctional materials and synergistic applications of various functions are important conditions for integrated and miniaturized equipment.Here,we developed asymmetric MXene/aramid nanofibers/po...The development of multifunctional materials and synergistic applications of various functions are important conditions for integrated and miniaturized equipment.Here,we developed asymmetric MXene/aramid nanofibers/polyimides(AMAP)aerogels with different modules using an integrated molding process.Cleverly asymmetric modules(layered MXene/aramid nanofibers section and porous MXene/aramid nanofibers/polyimides section)interactions are beneficial for enhanced performances,resulting in low reflection electromagnetic interference(EMI)shielding(specific shielding effectiveness of 2483(dB·cm^(3))/g and a low R-value of 0.0138),high-efficiency infrared radiation(IR)stealth(ultra-low thermal conductivity of 0.045 W/(m·K)and IR emissivity of 0.32 at 3–5μm and 0.28 at 8–14μm),and excellent thermal management performances of insulated Joule heating.Furthermore,these multifunctional AMAP aerogels are suitable for various application scenarios such as personal and building protection against electromagnetic pollution and cold,as well as military equipment protection against infrared detection and EMI.展开更多
基金supported by the Talent Fund of Beijing Jiaotong University(No.2023XKRC015)the National Natural Science Foundation of China(No.52172081)+2 种基金the Key R&D and Promotion Special Projects(Science and Technology)of Henan Province(No.232102240068)the Henan Provincial Department of Education(No.22B150010)Henan Province Key Research and Development Project(No.251111321500).
文摘Currently,the develop-ment of low-reflection electromagnetic interference(EMI)shielding composite materials for mitigating secondary electromagnetic wave pollution has become a major research focus.However,achieving thinness,high toughness,low reflectivity,and multi-functionality in flexible EMI shielding films remains a challenge.To address this issue,this study introduces a“magnetic-electric”Janus structure EMI shielding composite film composed of MXene nanosheets,carbonized ZIF-67(CZIF67)nanop-articles and aramid nanofibers(ANF),balancing thinness,high toughness,low reflectivity,and multifunctionality.As a result,the MXene/ANF-CZIF67/ANF-4(MACA-4)sample exhibits high tensile strength(110.0±7.0 MPa),large strain tolerance(21%),and superior toughness(14.9±0.9 MJ·m^(-3)),reflecting the stress dispersion effect of the three-dimensional(3D)network structure of ANF and the strengthening effect of hydrogen bonding.The sample exhibits excellent flexibility,resistance to rubbing and folding.Even with a thickness of only 80μm,the MACA-4 film exhibits a reflection performance(SER)as low as 4.3 to 4.5 dB in the 8.2 to 9.6 GHz band and the SE_(T)in the X-band reaches 44.8 dB.In addition,the superior conductivity of the MXene/ANF layer and the localized surface plasmon resonance effect give the MACA composite films excellent electrothermal conversion capabilities.Surprisingly,the sample also exhibited excellent infrared stealth and fire alarm properties.This work offers valuable guidance on the fabrication of ultra-thin flexible EMI shielding composites and provides an important scientific basis for the design and application of efficient EMI shielding materials.
基金supported by the Natural Science Foundation of Anhui Province(No.2308085QE146 and 2208085ME116)the National Natural Science Foundation of China(No.52173039)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210894)the Anhui Provincial Universities Outstanding Youth Research Project(No.2023AH020018).
文摘Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.
基金supported by the National Natural Science Foundation of China(grant no.52273044,52373092)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(grant no.sklpme2023-3-4)+1 种基金the Key Research Program of Zhejiang Province(grant no.2023C01101,2023C01210,2022C01049,2022C01205)the Natural Science Foundation of Zhejiang Province(grant no.LY20E030008).
文摘The increasingly serious electromagnetic(EM)radiation and related pollution effects have gradually attracted people's attention in the information age.Hence,it's crucial to develop adaptive shielding materials with minimum EM waves(EMW)reflection.In this paper,Ag nanoparticles loaded mesoporous carbon hollow spheres(MCHS@Ag)were synthesized by chemical reduction method,and cellulose nanofibers(CNF)/MXene/MCHS@Ag homogeneous composites were prepared.The total EM interference shielding efficiency(SET)of CNF/MXene/MCHS@Ag composite film was 32.83 dB(at 12.4 GHz),and the absorption effectiveness(SEA)was improved to 26.6 dB,which was 63.1%and 195.5%higher than that of CNF/MXene/MCHS composite film.The low dielectric property of MCHS effectively optimized the impedance matching between the composites and air.The hollow porous structure prolonged the transmission path of EMW and increased the absorption loss of the composites.At the same time,Ag nanoparticles located the MCHS were helpful to construct the internal conductive path overcoming the damage of the conductive property caused by the low dielectric of MCHS.This research adopts a straightforward method to construct a lightweight,pliable,and mesoporous composites for EMI shielding,which serves a crucial role in the current era of severe EM pollution.
基金support from the National Natural Science Foundation of China(52373077,52003106,52103074,52233006,52161135302)the Research Foundation Flanders(G0F2322N)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-03-E00108).
文摘Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
文摘The Belle Corporation is a Chinese domestic shoe maker and seller. It also belongs to an industry that has come to be representative of the ubiquitous "Made in China" label. One of the main reasons the company is favored by global investors is due to its unique business pattern-a pattern that sets manufacturing as its base and is active in exploring industrial chain downstream links and establishing its own individual retail channels. Ever since its first inception in the stock market, Belle has set out to acquire several upstream manufacturing companies, indicating its desire for increasing channel terminals. Using a vertically integrated competition strategy, Belle stands out amongst its rivals as being particularly successful in the non-mainstream manufacturing sector. Consequently, its business practices can be used as a model for other domestic manufacturing companies in their efforts to meet the challenges posed by globalization.
基金financial support from the National Natural Science Foundation of China (No. 51773167)the Natural Science Foundation of Shaanxi Province (No. 2019CGXNG-033)+2 种基金the Science and Technology Plan Project of Xi’an (Nos. 2019217814GXRC014CG015-GXYD14.7, and 2019217814GXRC014CG015-GXYD14.8)the China Postdoctoral Science Foundation (No. 2019M650268)the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (No. sklpme2020-4-16)。
文摘The conductive polymer composites(CPCs) with highly efficient electromagnetic interference(EMI)shielding effectiveness(SE) are always accompanied with excessive reflectivity, which would cause serious secondary EMI pollution. In this regard, the significant reduction of EMI reflection of CPCs to alleviate secondary pollution is deemed to be very important. Herein, a promising cyanate ester(CE) based composite was successfully fabricated by compounding carbonized spent coffee grounds(C-SCG) and graphene nanosheets(GNSs) via a facile solution blending followed by a hot-pressing method. Benefiting from the porous structure of C-SCG and the layered structure of GNSs, a three-dimensional(3 D)multi-interface conductive network in the CE was easily constructed. The EMI SE of the resultant 9 wt%C-SCG/CE composite(C9) is 15.38 d B and dramatically enhanced to 31.09 d B with the presence of 3 wt% GNSs. The remarkable enhancement is mainly attributed to the formation of the efficient conductive pathways as well as the well-dispersion of the incorporated fillers. Meanwhile, the absorption-dominated shielding mechanism in the prepared composites gets benefit from the synergistic effect of porous C-SCG and lamellar GNSs, which effectively captures and attenuates electromagnetic waves. These encouraging findings extend the practical applications of porous biocarbon materials in EMI shielding field.
基金National Natural Science Foundation of China(Nos.52373077,52003106,and 52161135302)the Research Foundation Flanders(No.G0F2322N)+1 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_1236)the Innovation Program of Shanghai Municipal Education Commission(No.2021-01-07-00-03-E00108).
文摘Researching and manufacturing materials that possess both electromagnetic interference(EMI)shielding and infrared stealth capabilities is of great significance.Herein,an ultrathin polyimide-based nonwoven fabric with low-reflection EMI shielding/infrared stealth performance is successfully fabricated by in-situ loading of Fe_(3)O_(4)/Ag nanoparticles on the surface of polyimide(PI)fiber(PFA),and followed by bonding with a commercial Cu/Ni mesh.The synergistic assembly of PFA and Cu/Ni promotes the rational construction of hierarchical impedance matching,inducing electromagnetic waves(EMW)to enter the composite and be dissipated as much as possible.Meanwhile,the existence of Cu/Ni mesh on back of PFA facilitates the formation of electromagnetic resonance and destructive interference of EMW reflected from composite,leading to a lowerreflectivity(0.26)EMI shielding performance of 58 dB within 24–40 GHz at a thinner thickness(430μm).More importantly,the fluffy PFA nonwoven fabric and metal Cu/Ni mesh endow composite with good thermal insulation and low infrared emissivity,resulting in excellent infrared stealth performance in various environments.As a result,such excellent compatibility makes it possible to become a promising defense material to be applied in military tent for preventing electromagnetic and infrared radiation.
基金Foundation item： National Natural Science Foundation of China （10376001）
文摘The multiplexing ability of a novel multiplexing fiber Bragg grating （FBG） method based on Optical Time Domain Reflecto meter （OTDR） and Time Division Multiplexing TDM technologies has been theoretically analyzed and studied. This method permits the interrogation of hundreds of identical FBGs with low reflectivity in a single fiber, making the FBG sensors more applicable in the aerospace health monitoring engineering. The analysis shows that the multiplexing ability can be greatly improved if the FBG reflectivity is sufficiently low. And hence, an inexpensive large-scale distributed sensing system based on this method can be realized, When evaluating the multiplexing ability of this system, we propose for the first time that the interference effect of multi-reflections among FBGs should be taken into consideration.
基金This work was generously supported by Professor Luo Zhu from the College of Materials and Metallurgy at Guizhou University.
文摘Traditional electromagnetic shielding materials primarily enhance reflection and absorption losses by increasing conductivity.While this approach improves shielding effectiveness,it also leads to issues such as impedance mismatch,increased surface reflectivity,and irreversible secondary electromagnetic pollution.Consequently,the development of environmentally friendly electromagnetic interference(EMI)shielding materials with high efficiency and low reflectivity has become a key focus of research.This review examines the critical evaluation criteria and factors that influence the performance and reflectivity of EMI shielding materials.It also highlights recent advances in material tuning mechanisms and structural design strategies for the development of low-reflectivity,sustainable EMI shielding materials.By integrating material and structural design considerations,this review provides a comprehensive overview of strategies for constructing polymer-based low-reflectivity shielding materials,identifies persistent challenges in material design,and discusses future research directions in this field.
基金supported by the National Natural Science Foundation of China(No.52102045,No.52173274).
文摘Absorption-dominated electromagnetic interference(EMI)shielding fabrics are urgently needed to address the increasingly severe electromagnetic radiation pollution,especially the secondary radiation problem.In this study,we design novel core-sheath CNT@MXene fibers with a gradient conductive structure and corresponding fabrics to realize absorption-dominated EMI shielding performances.This coaxial structure utilizes carbon nanotubes(CNTs)as the sheath and MXene as the core and is constructed through a wet spinning technique.By virtue of the core-sheath structure,the conductive gradient structure in the fibers is easily optimized by adjusting the core MXene and sheath CNT content.This gradient conductive network of fiber effectively facilitates the incidence of electromagnetic waves and strong interactions between electromagnetic waves and the composites,resulting in excellent EMI absorption ability.Within the X-band frequency range,the fabric exhibits an electromagnetic interference shielding effectiveness of 23.40 dB and an absorption coefficient of 0.63.Due to the protection of polymer,the fiber’s electrical conductivity remains stable under conditions such as multi-cycle bending,stretching,and ultrasonic treatment,and in high relative humidity environments.Additionally,the fabric also demonstrates EMI shielding stability in indoor environments.This work indicates the great potential of the gradient structured fibers to achieve an absorption-dominated mechanism for next-generation eco-friendly EMI shielding fabrics.
基金supported by the National Key R&D Program of China(No.2021YFB3502500)the National Natural Science Foundation of China(Nos.52172091 and 52172295)+1 种基金Open Fund of Key Laboratory of Materials Preparation and Protection for Harsh Environment(Nanjing University of Aeronautics and Astronautics)Ministry of Industry and Information Technology(No.56XCA22042).
文摘The development of multifunctional materials and synergistic applications of various functions are important conditions for integrated and miniaturized equipment.Here,we developed asymmetric MXene/aramid nanofibers/polyimides(AMAP)aerogels with different modules using an integrated molding process.Cleverly asymmetric modules(layered MXene/aramid nanofibers section and porous MXene/aramid nanofibers/polyimides section)interactions are beneficial for enhanced performances,resulting in low reflection electromagnetic interference(EMI)shielding(specific shielding effectiveness of 2483(dB·cm^(3))/g and a low R-value of 0.0138),high-efficiency infrared radiation(IR)stealth(ultra-low thermal conductivity of 0.045 W/(m·K)and IR emissivity of 0.32 at 3–5μm and 0.28 at 8–14μm),and excellent thermal management performances of insulated Joule heating.Furthermore,these multifunctional AMAP aerogels are suitable for various application scenarios such as personal and building protection against electromagnetic pollution and cold,as well as military equipment protection against infrared detection and EMI.
基金supported by the National Natural Science Foundation of China(52103305 and 51973142)Sichuan Science and Technology Program(2023NSFSC0438)the Opening Project of Robotic Satellite Key Laboratory of Sichuan Province.
