Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial i...Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable electronics.In this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"method.Janus(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/cm.And Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 dB.The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa.It also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).展开更多
Carbon nanotubes(CNTs)incorporated polymeric composites have been extensively investigated for microwave absorption at target frequencies to meet the requirement of radar cross-section reduction.In this work,a strateg...Carbon nanotubes(CNTs)incorporated polymeric composites have been extensively investigated for microwave absorption at target frequencies to meet the requirement of radar cross-section reduction.In this work,a strategy of efficient utilization of CNT in producing CNT incorporated aramid papers is demonstrated.The layer-by-layer self-assembly technique is used to coat the surfaces of meta-aramid fibers and fibrils with CNT,providing novel raw materials available for the large-scale papermaking.The hierarchical construction of CNT networks resolves the dilemma of increasing CNT content and avoiding the agglomeration of CNT,which is a frequent challenge for CNT incorporated polymeric composites.The composite paper,which contains abundant heterogeneous interfaces and long-range conductive networks,is capable of reaching a high permittivity and dielectric loss tangent at a low CNT loading,its complex permittivity is,so far,adjustable in the range of(1.20−j0.05)to(25.17−j18.89)at 10 GHz.Some papers with optimal matching thicknesses achieve a high-efficiency microwave absorption with a reflection loss lower than−10 dB in the entire X-band.展开更多
探讨消防员灭火防护服的研发现状及发展趋势。介绍了国内外消防员灭火防护服的发展现状;对三个标准的整体热防护性能、阻燃性能、耐热性能和耐静水压性能进行了对比和分析,包括美国的NFPA1971:2018《Stangard on Protective Ensembles f...探讨消防员灭火防护服的研发现状及发展趋势。介绍了国内外消防员灭火防护服的发展现状;对三个标准的整体热防护性能、阻燃性能、耐热性能和耐静水压性能进行了对比和分析,包括美国的NFPA1971:2018《Stangard on Protective Ensembles for Strucral Fire Fighting and Proximity Fire Fighting》、欧盟的BS EN 469:2014《Protective Clothing for Firefightingters-Performance Requirements for Protective Clothing for Firefighting》和我国的GA 10-2014《消防员灭火防护服》。对消防员灭火防护服的研发方向进行了展望。认为:消防员灭火防护服应进一步提高热防护性能,减少整体质量,增加舒适性,引入多功能性及高科技智能技术,实现综合防护。展开更多
Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical propert...Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical properties of MXene fibers because of the high rigidity of MXene sheets and insufficient inter-sheet interactions.Herein,we demonstrate a core-shell wet-spinning methodology for fabricating highly conductive,super-tough,ultra-strong,and environmentally stable Ti_(3)C_(2)T_(x) MXene-based core-shell fibers with conductive MXene cores and tough aramid nanofiber(ANF)shells.The highly orientated and low-defect structure endows the ANF@MXene core-shell fiber with supertoughness of~48.1 MJ m^(-3),high strength of~502.9 MPa,and high conductivity of~3.0×10^(5)S m^(-1).The super-tough and conductive ANF@MXene fibers can be woven into textiles,exhibiting an excellent electromagnetic interference(EMI)shielding efficiency of 83.4 dB at a small thickness of 213μm.Importantly,the protection of the ANF shells provides the fibers with satisfactory cyclic stability under dynamic stretching and bending,and excellent resistance to acid,alkali,seawater,cryogenic and high temperatures,and fire.The oxidation resistance of the fibers is demonstrated by their wellmaintained EMI shielding performances.The multifunctional core-shell fibers would be highly promising in the fields of EMI shielding textiles,wearable electronics and aerospace.展开更多
Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to...Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to provide additional functionalities for various artificial-intelligence-driven systems,such as tactile sensing ability.Herein,a layering design strategy is proposed to fabricate ultrathin Ti_(3)C_(2)T_(x)MXene-aramid nanofiber(MA)films by a layer-by-layer assembling process.Compared to that of randomly mixed films,the designed MA films exhibited a higher EMI shielding efficiency at an ultrathin thickness of 9 pm,which increased from 26.4 to 40.7 dB,owing to the additional multiple-interface scattering mechanism.Importantly,the novel MA films displayed strong EMI shielding ability even after heating/cooling treatments within a wide temperature range of-196 to 300℃.Moreover,the same material displayed a tensile strength of 124.1±2.7 MPa and a toughness of 6.3±1.1 MJ·m^(-3),which are approximately 9.1 times and 45 times higher than those of pure MXene films,respectively.The MA film is also capable of detecting tactile signals via the triboelectric effect.A 2×4 tactile sensor array was developed to achieve an accurate signal catching capability.Therefore,in addition to the shielding performance,the manifestation of tactile perception by the MA films offers exciting opportunities in the fields of soft robotics and human-machine interactions.展开更多
The practical application of solid polymer electrolytes in high-energy Li metal batteries is hindered by Li dendrites,electrochemical instability and insufficient ion conductance.To address these issues,flexible compo...The practical application of solid polymer electrolytes in high-energy Li metal batteries is hindered by Li dendrites,electrochemical instability and insufficient ion conductance.To address these issues,flexible composite polymer electrolyte(CPE)membranes with three dimensional(3D)aramid nanofiber(ANF)frameworks are facilely fabricated by filling polyethylene oxide(PEO)-lithium bis(trifluoromethylsulphonyl)imide(Li TFSI)electrolyte into 3D ANF scaffolds.Because of the unique composite structure design and the continuous ion conduction at the 3D ANF framework/PEO-Li TFSI interfaces,the CPE membranes show higher mechanical strength(10.0 MPa),thermostability,electrochemical stability(4.6 V at 60℃)and ionic conductivity than the pristine PEO-Li TFSI electrolyte.Thus,the CPEs display greatly improved interfacial stability against Li dendrites(≥1000 h at 30℃under 0.10 m A cm-2),compared with the pristine electrolyte(short circuit in 13 h).The CPE-based all-solid-state LiFePO4/Li cells also exhibit superior cycling performance(e.g.,130 mA h g-1 with 93%retention after 100 cycles at 0.4 C)than the ANF-free cells(e.g.,82 mA h g-1 with 66%retention).This work offers a simple and effective way to achieve high-performance composite electrolyte membranes with 3D nanofiller framework for promising solid-state Li metal battery applications.展开更多
The high power density and intelligence of next-generation flexible electronic devices bring many challenges to fabricate flexible composite films with electromagnetic interference(EMI)shielding effectiveness(SE)prope...The high power density and intelligence of next-generation flexible electronic devices bring many challenges to fabricate flexible composite films with electromagnetic interference(EMI)shielding effectiveness(SE)property and excellent toughness via a simple method.Herein,inspired by the layered structure and biopolymer matrix networks in natural nacre,nacre-like layered Ti_(3)C2TX(MXene)/aramid nanofiber(ANF)films were fabricated through sol-gel,vacuum-assisted filtration,and hot-pressing.Three-dimensional(3D)interconnected aramid nanofibers networks between adjacent layered MXene result in an ultralong strain-to-failure of the film.Even though the functional filler MXene contents are as high as 60 wt.%and 70 wt.%,the strain-to-failure of the films could reach astonishing values of 18.34%±1.86%and 14.43%±1.26%,respectively.And the tensile strength could maintain about 85 MPa.Excitingly,with such a high filler,the film can also withstand double folding and vigorous rubbing without damage,which could better adapt to a harsh application environment.The result means that this work provides a convenient way to prepare other high functional filler composite films with excellent mechanical performance.The EMI SE values could reach 45 and 52.15 dB at 60 wt.%and 70 wt.%MXene in 8.2–12.4 GHz.Meanwhile,the films have prominent Joule heating properties,high sensitivity(<15 s),small voltage operation(0.5 V),and high operation constancy(1300 s).Therefore,nacre-inspired MXene/ANF composite films in this work have ability to apply in many areas including communication technology,military,and aerospace.展开更多
基金The authors are grateful for the support and funding from the Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120093)Foundation of National Natural Science Foundation of China(Nos.U21A2093 and 51973173)Technological Base Scientific Research Projects(Highly Thermal conductivity Nonmetal Materials).
文摘Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable electronics.In this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"method.Janus(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/cm.And Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 dB.The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa.It also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).
基金the National Natural Science Foundation of China(No.U21A2093).
文摘Carbon nanotubes(CNTs)incorporated polymeric composites have been extensively investigated for microwave absorption at target frequencies to meet the requirement of radar cross-section reduction.In this work,a strategy of efficient utilization of CNT in producing CNT incorporated aramid papers is demonstrated.The layer-by-layer self-assembly technique is used to coat the surfaces of meta-aramid fibers and fibrils with CNT,providing novel raw materials available for the large-scale papermaking.The hierarchical construction of CNT networks resolves the dilemma of increasing CNT content and avoiding the agglomeration of CNT,which is a frequent challenge for CNT incorporated polymeric composites.The composite paper,which contains abundant heterogeneous interfaces and long-range conductive networks,is capable of reaching a high permittivity and dielectric loss tangent at a low CNT loading,its complex permittivity is,so far,adjustable in the range of(1.20−j0.05)to(25.17−j18.89)at 10 GHz.Some papers with optimal matching thicknesses achieve a high-efficiency microwave absorption with a reflection loss lower than−10 dB in the entire X-band.
文摘探讨消防员灭火防护服的研发现状及发展趋势。介绍了国内外消防员灭火防护服的发展现状;对三个标准的整体热防护性能、阻燃性能、耐热性能和耐静水压性能进行了对比和分析,包括美国的NFPA1971:2018《Stangard on Protective Ensembles for Strucral Fire Fighting and Proximity Fire Fighting》、欧盟的BS EN 469:2014《Protective Clothing for Firefightingters-Performance Requirements for Protective Clothing for Firefighting》和我国的GA 10-2014《消防员灭火防护服》。对消防员灭火防护服的研发方向进行了展望。认为:消防员灭火防护服应进一步提高热防护性能,减少整体质量,增加舒适性,引入多功能性及高科技智能技术,实现综合防护。
基金Financial support from the National Natural Science Foundation of China(51922020,52090034)the Fundamental Research Funds for the Central Universities(BHYC1707B,XK1802-2)。
文摘Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical properties of MXene fibers because of the high rigidity of MXene sheets and insufficient inter-sheet interactions.Herein,we demonstrate a core-shell wet-spinning methodology for fabricating highly conductive,super-tough,ultra-strong,and environmentally stable Ti_(3)C_(2)T_(x) MXene-based core-shell fibers with conductive MXene cores and tough aramid nanofiber(ANF)shells.The highly orientated and low-defect structure endows the ANF@MXene core-shell fiber with supertoughness of~48.1 MJ m^(-3),high strength of~502.9 MPa,and high conductivity of~3.0×10^(5)S m^(-1).The super-tough and conductive ANF@MXene fibers can be woven into textiles,exhibiting an excellent electromagnetic interference(EMI)shielding efficiency of 83.4 dB at a small thickness of 213μm.Importantly,the protection of the ANF shells provides the fibers with satisfactory cyclic stability under dynamic stretching and bending,and excellent resistance to acid,alkali,seawater,cryogenic and high temperatures,and fire.The oxidation resistance of the fibers is demonstrated by their wellmaintained EMI shielding performances.The multifunctional core-shell fibers would be highly promising in the fields of EMI shielding textiles,wearable electronics and aerospace.
基金supported by the National Natural Science Foundation of China(No.51877132).
文摘Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to provide additional functionalities for various artificial-intelligence-driven systems,such as tactile sensing ability.Herein,a layering design strategy is proposed to fabricate ultrathin Ti_(3)C_(2)T_(x)MXene-aramid nanofiber(MA)films by a layer-by-layer assembling process.Compared to that of randomly mixed films,the designed MA films exhibited a higher EMI shielding efficiency at an ultrathin thickness of 9 pm,which increased from 26.4 to 40.7 dB,owing to the additional multiple-interface scattering mechanism.Importantly,the novel MA films displayed strong EMI shielding ability even after heating/cooling treatments within a wide temperature range of-196 to 300℃.Moreover,the same material displayed a tensile strength of 124.1±2.7 MPa and a toughness of 6.3±1.1 MJ·m^(-3),which are approximately 9.1 times and 45 times higher than those of pure MXene films,respectively.The MA film is also capable of detecting tactile signals via the triboelectric effect.A 2×4 tactile sensor array was developed to achieve an accurate signal catching capability.Therefore,in addition to the shielding performance,the manifestation of tactile perception by the MA films offers exciting opportunities in the fields of soft robotics and human-machine interactions.
基金supported partially by Beijing Natural Science Foundation(L172036)Joint Funds of the Equipment Pre-Research and Ministry of Education(6141A020225)+2 种基金Par-Eu Scholars Program,Science and Technology Beijing 100 Leading Talent Training Project,Beijing Municipal Science and Technology Project(Z161100002616039)China Postdoctoral Science Foundation(2018M631419)the Fundamental Research Funds for the Central Universities(2017ZZD02 and 2019QN001).
文摘The practical application of solid polymer electrolytes in high-energy Li metal batteries is hindered by Li dendrites,electrochemical instability and insufficient ion conductance.To address these issues,flexible composite polymer electrolyte(CPE)membranes with three dimensional(3D)aramid nanofiber(ANF)frameworks are facilely fabricated by filling polyethylene oxide(PEO)-lithium bis(trifluoromethylsulphonyl)imide(Li TFSI)electrolyte into 3D ANF scaffolds.Because of the unique composite structure design and the continuous ion conduction at the 3D ANF framework/PEO-Li TFSI interfaces,the CPE membranes show higher mechanical strength(10.0 MPa),thermostability,electrochemical stability(4.6 V at 60℃)and ionic conductivity than the pristine PEO-Li TFSI electrolyte.Thus,the CPEs display greatly improved interfacial stability against Li dendrites(≥1000 h at 30℃under 0.10 m A cm-2),compared with the pristine electrolyte(short circuit in 13 h).The CPE-based all-solid-state LiFePO4/Li cells also exhibit superior cycling performance(e.g.,130 mA h g-1 with 93%retention after 100 cycles at 0.4 C)than the ANF-free cells(e.g.,82 mA h g-1 with 66%retention).This work offers a simple and effective way to achieve high-performance composite electrolyte membranes with 3D nanofiller framework for promising solid-state Li metal battery applications.
基金Financial support from the Talent Fund of Beijing Jiaotong University(No,2023XKRC015)the National Natural Science Foundation of China(No.52172081)is gratefully acknowledged.
文摘The high power density and intelligence of next-generation flexible electronic devices bring many challenges to fabricate flexible composite films with electromagnetic interference(EMI)shielding effectiveness(SE)property and excellent toughness via a simple method.Herein,inspired by the layered structure and biopolymer matrix networks in natural nacre,nacre-like layered Ti_(3)C2TX(MXene)/aramid nanofiber(ANF)films were fabricated through sol-gel,vacuum-assisted filtration,and hot-pressing.Three-dimensional(3D)interconnected aramid nanofibers networks between adjacent layered MXene result in an ultralong strain-to-failure of the film.Even though the functional filler MXene contents are as high as 60 wt.%and 70 wt.%,the strain-to-failure of the films could reach astonishing values of 18.34%±1.86%and 14.43%±1.26%,respectively.And the tensile strength could maintain about 85 MPa.Excitingly,with such a high filler,the film can also withstand double folding and vigorous rubbing without damage,which could better adapt to a harsh application environment.The result means that this work provides a convenient way to prepare other high functional filler composite films with excellent mechanical performance.The EMI SE values could reach 45 and 52.15 dB at 60 wt.%and 70 wt.%MXene in 8.2–12.4 GHz.Meanwhile,the films have prominent Joule heating properties,high sensitivity(<15 s),small voltage operation(0.5 V),and high operation constancy(1300 s).Therefore,nacre-inspired MXene/ANF composite films in this work have ability to apply in many areas including communication technology,military,and aerospace.
