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
Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_...Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.展开更多
Application of aerogel fibers in thermal insulating garments have sparked a substantial interest.However,achieving a high porosity and low thermal conductivity for aerogel fibers remain challenging,despite the innovat...Application of aerogel fibers in thermal insulating garments have sparked a substantial interest.However,achieving a high porosity and low thermal conductivity for aerogel fibers remain challenging,despite the innovative designs of porous struc-ture.Herein,we fabricated lightweight and super-thermal insulating polyimide(PI)aerogel fibers via freeze-spinning by using polyvinyl alcohol(PVA)as a pore regulator.The high affinity of PVA with water enables it to accelerate the ice crystal nucleation,adjust pore formation,and construct a controllable porous structure of PI aerogel fiber.The as-fabricated PI aerogel fiber has a considerable reduced pore size,high porosity(95.6%),improved flexibility and mechanical strength,and can be woven into fabrics.The PI aerogel fabric exhibits low thermal conductivity and excellent thermal insulation in a wide range of temperature(from-196 to 300℃).Furthermore,the PI aerogel fabrics can be easily functionalized to expand their applications,such as in intelligent temperature regulation and photothermal conversion.These results demonstrate that the aerogel fibers/fabric are promising materials for next-generation textile materials for personal thermal management.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 Basic Science Research Program of the National Research Foundation(NRF)of South Koreafunded by the Ministry of Science&ICT and Future Planning(NRF-2020M3H4A3081889)KIST Institutional Program of South Korea(Project Nos.2E31860)。
文摘Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.
基金supported by the National Natural Science Foundation of China(52073053)Shanghai Rising-Star Program(21QA1400300)+2 种基金Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-03-E00108)Science and Technology Commission of Shanghai Municipality(20520741100)China Postdoctoral Science Foundation(2021M690596).
文摘Application of aerogel fibers in thermal insulating garments have sparked a substantial interest.However,achieving a high porosity and low thermal conductivity for aerogel fibers remain challenging,despite the innovative designs of porous struc-ture.Herein,we fabricated lightweight and super-thermal insulating polyimide(PI)aerogel fibers via freeze-spinning by using polyvinyl alcohol(PVA)as a pore regulator.The high affinity of PVA with water enables it to accelerate the ice crystal nucleation,adjust pore formation,and construct a controllable porous structure of PI aerogel fiber.The as-fabricated PI aerogel fiber has a considerable reduced pore size,high porosity(95.6%),improved flexibility and mechanical strength,and can be woven into fabrics.The PI aerogel fabric exhibits low thermal conductivity and excellent thermal insulation in a wide range of temperature(from-196 to 300℃).Furthermore,the PI aerogel fabrics can be easily functionalized to expand their applications,such as in intelligent temperature regulation and photothermal conversion.These results demonstrate that the aerogel fibers/fabric are promising materials for next-generation textile materials for personal thermal management.
