Construction of advanced electromagnetic interference(EMI)shielding materials with miniaturized,programmable structure and low reflection are promising but challenging.Herein,an integrated transition-metal carbides/ca...Construction of advanced electromagnetic interference(EMI)shielding materials with miniaturized,programmable structure and low reflection are promising but challenging.Herein,an integrated transition-metal carbides/carbon nanotube/polyimide(gradient-conductive MXene/CNT/PI,GCMCP)aerogel frame with hierarchical porous structure and gradient-conductivity has been constructed to achieve EMI shielding with ultra-low reflection.The gradient-conductive structures are obtained by continuous 3D printing of MXene/CNT/poly(amic acid)inks with different CNT contents,where the slightly conductive top layer serves as EM absorption layer and the highly conductive bottom layer as reflection layer.In addition,the hierarchical porous structure could extend the EM dissipation path and dissipate EM by multiple reflections.Consequently,the GCMCP aerogel frames exhibit an excellent average EMI shielding efficiency(68.2 dB)and low reflection(R=0.23).Furthermore,the GCMCP aerogel frames with miniaturized and programmable structures can be used as EMI shielding gaskets and effectively block wireless power transmission,which shows a prosperous application prospect in defense industry and aerospace.展开更多
MXene-based multilayered composite films show great promise in electromagnetic interference(EMI)shielding field,but the trade-off between mechanical properties,oxidation resistance and EMI shielding performance remain...MXene-based multilayered composite films show great promise in electromagnetic interference(EMI)shielding field,but the trade-off between mechanical properties,oxidation resistance and EMI shielding performance remains a huge challenge.Herein,inspired by the architecture of millefeuille,alternating multilayered MXene/carbon nanotube(CNT)films were successfully prepared using an alternating vacuum-assisted filtration method,in which the alternating CNT layers not only act as the mechanical frame and oxidation barrier,but also synergistically enhance the EMI shielding effect of MXene layers through the distinctive“absorption-reflection-reabsorption”mechanism.By optimizing the alternating multilayered structure,the MXene/CNT film with a thickness of 36µm can achieve a remarkable EMI shielding effectiveness(SE)of 81.4 dB across the frequency range of 8.2–26.5 GHz.Meanwhile,the mechanical strength and toughness of the MXene/CNT film reach 83.4 MPa and 7.20 MJ/m^(3),respectively.Moreover,the CNT layer can effectively isolate MXene layer from oxygen,thus enabling the fire/oxidation resistance of the multilayer film in complex environments.Besides,the multilayered composite film exhibits impressive Joule heating capacity,which can reach 237℃within 10 s at an applied voltage of only 2.0 V.Therefore,the alternating multilayered MXene/CNT film breaks through the performance balance limit,showing a great prospect for the future.展开更多
Herein,N-Ti3C2@CNT microspheres are successfully synthesized by the simple spray drying method.In the preparation process,HCl-treated melamine(HTM)is selected as the sources of carbon and nitrogen.It not only realizes...Herein,N-Ti3C2@CNT microspheres are successfully synthesized by the simple spray drying method.In the preparation process,HCl-treated melamine(HTM)is selected as the sources of carbon and nitrogen.It not only realizes in situ growth of CNTs on the surface of MXene nanosheets with the catalysis of Ni,but also introduces efficient N-doping in both MXene and CNTs.Within the microsphere,MXene nanosheets interconnect with CNTs to form porous and conductive network.In addition,N-doped MXene and CNTs can provide strong chemical immobilization for polysulfides and effectively entrap them within the porous microspheres.Above-mentioned merits enable N-Ti3C2@CNT microspheres to be ideal sulfur host.When used in lithium–sulfur(Li–S)battery,the N-Ti3C2@CNT microspheres/S cathode delivers initial specific capacity of 927 mAh g−1 at 1 C and retains high capacity of 775 mAh g−1 after 1000 cycles with extremely low fading rate(FR)of 0.016%per cycle.Furthermore,the cathode still shows high cycling stability at high C-rate of 4 C(capacity of 647 mAh g−1 after 650 cycles,FR 0.027%)and high sulfur loading of 3 and 6 mg cm−2 for Li–S batteries.展开更多
Composite structures are sensitive to impact damage in practical engineering.Electric resistance change method(ERCM)is an ideal technique for damage monitoring of composite structures.Due to the anisotropy of fiber-re...Composite structures are sensitive to impact damage in practical engineering.Electric resistance change method(ERCM)is an ideal technique for damage monitoring of composite structures.Due to the anisotropy of fiber-resin matrix composites,impact location monitoring is difficult,and research on impact location of fiber composite laminates(FRPs)is limited.A preparation method of MXene/CNT/CuNps thin film sensor is proposed.According to the modeling simulation and theoretical calculation,the resistance change characteristics of the thin film sensor are obtained,the relationship between the impact distance and the resistance change is established,and the sensor array is designed.A three-point localization algorithm and a weight function compensation localization algorithm are proposed,which can improve the imaging accuracy of the impact position.The impact point location was observed and analyzed using ultrasonic C-scan technology.The results show that the weight function compensation positioning algorithm can accurately locate the impact of the composite structure,and the error in the X direction is 7.1%,the error in the Y direction is 0.03%,which verifies the effectiveness of the method.展开更多
基金the National Natural Science Foundation of China(52073053,52233006)Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)+3 种基金Shanghai Rising-Star Program(21QA1400300)Innovation Program of Shanghai Municipal Education Commission(2021-01-0700-03-E00108)Science and Technology Commission of Shanghai Municipality(20520741100)China Postdoctoral Science Foundation(2021M690596)。
文摘Construction of advanced electromagnetic interference(EMI)shielding materials with miniaturized,programmable structure and low reflection are promising but challenging.Herein,an integrated transition-metal carbides/carbon nanotube/polyimide(gradient-conductive MXene/CNT/PI,GCMCP)aerogel frame with hierarchical porous structure and gradient-conductivity has been constructed to achieve EMI shielding with ultra-low reflection.The gradient-conductive structures are obtained by continuous 3D printing of MXene/CNT/poly(amic acid)inks with different CNT contents,where the slightly conductive top layer serves as EM absorption layer and the highly conductive bottom layer as reflection layer.In addition,the hierarchical porous structure could extend the EM dissipation path and dissipate EM by multiple reflections.Consequently,the GCMCP aerogel frames exhibit an excellent average EMI shielding efficiency(68.2 dB)and low reflection(R=0.23).Furthermore,the GCMCP aerogel frames with miniaturized and programmable structures can be used as EMI shielding gaskets and effectively block wireless power transmission,which shows a prosperous application prospect in defense industry and aerospace.
基金supported by the National Natural Science Foundation of China(52303113 and 52273085)the Key Scientific Projects of Colleges and Universities in Henan Province of China(24A430045)the Key Research and Development Project of Henan Province of China(241111232300).
文摘MXene-based multilayered composite films show great promise in electromagnetic interference(EMI)shielding field,but the trade-off between mechanical properties,oxidation resistance and EMI shielding performance remains a huge challenge.Herein,inspired by the architecture of millefeuille,alternating multilayered MXene/carbon nanotube(CNT)films were successfully prepared using an alternating vacuum-assisted filtration method,in which the alternating CNT layers not only act as the mechanical frame and oxidation barrier,but also synergistically enhance the EMI shielding effect of MXene layers through the distinctive“absorption-reflection-reabsorption”mechanism.By optimizing the alternating multilayered structure,the MXene/CNT film with a thickness of 36µm can achieve a remarkable EMI shielding effectiveness(SE)of 81.4 dB across the frequency range of 8.2–26.5 GHz.Meanwhile,the mechanical strength and toughness of the MXene/CNT film reach 83.4 MPa and 7.20 MJ/m^(3),respectively.Moreover,the CNT layer can effectively isolate MXene layer from oxygen,thus enabling the fire/oxidation resistance of the multilayer film in complex environments.Besides,the multilayered composite film exhibits impressive Joule heating capacity,which can reach 237℃within 10 s at an applied voltage of only 2.0 V.Therefore,the alternating multilayered MXene/CNT film breaks through the performance balance limit,showing a great prospect for the future.
文摘Herein,N-Ti3C2@CNT microspheres are successfully synthesized by the simple spray drying method.In the preparation process,HCl-treated melamine(HTM)is selected as the sources of carbon and nitrogen.It not only realizes in situ growth of CNTs on the surface of MXene nanosheets with the catalysis of Ni,but also introduces efficient N-doping in both MXene and CNTs.Within the microsphere,MXene nanosheets interconnect with CNTs to form porous and conductive network.In addition,N-doped MXene and CNTs can provide strong chemical immobilization for polysulfides and effectively entrap them within the porous microspheres.Above-mentioned merits enable N-Ti3C2@CNT microspheres to be ideal sulfur host.When used in lithium–sulfur(Li–S)battery,the N-Ti3C2@CNT microspheres/S cathode delivers initial specific capacity of 927 mAh g−1 at 1 C and retains high capacity of 775 mAh g−1 after 1000 cycles with extremely low fading rate(FR)of 0.016%per cycle.Furthermore,the cathode still shows high cycling stability at high C-rate of 4 C(capacity of 647 mAh g−1 after 650 cycles,FR 0.027%)and high sulfur loading of 3 and 6 mg cm−2 for Li–S batteries.
基金This work was financially supported by National Natural Science Foundation of China(11902204)Liaoning Revitalization Talents Program(XLYC2007118)+3 种基金Aeronautical Science Foundation(201903054001)Shenyang Youth Technological Innovation Talent Project(RC200030),Shenyang Natural Science Foundation Project(22-315-6-07)Education Department of Liaoning Province’s Item(LJKQZ 20222263)Basic Scientific Research Project of Liaoning Provincial Department of Education(LJKMZ20220566).
文摘Composite structures are sensitive to impact damage in practical engineering.Electric resistance change method(ERCM)is an ideal technique for damage monitoring of composite structures.Due to the anisotropy of fiber-resin matrix composites,impact location monitoring is difficult,and research on impact location of fiber composite laminates(FRPs)is limited.A preparation method of MXene/CNT/CuNps thin film sensor is proposed.According to the modeling simulation and theoretical calculation,the resistance change characteristics of the thin film sensor are obtained,the relationship between the impact distance and the resistance change is established,and the sensor array is designed.A three-point localization algorithm and a weight function compensation localization algorithm are proposed,which can improve the imaging accuracy of the impact position.The impact point location was observed and analyzed using ultrasonic C-scan technology.The results show that the weight function compensation positioning algorithm can accurately locate the impact of the composite structure,and the error in the X direction is 7.1%,the error in the Y direction is 0.03%,which verifies the effectiveness of the method.
