Three-dimensional(3D)porous aerogels have been regarded as lightweight and effective electromagnetic(EM)absorbers,but the rational design of components with ordered macroscopic structures at low cost is still a major ...Three-dimensional(3D)porous aerogels have been regarded as lightweight and effective electromagnetic(EM)absorbers,but the rational design of components with ordered macroscopic structures at low cost is still a major challenge.In this work,we constructed an ultralight biomass-derived carbon nanosheet/MXene(CNMX)composite aerogel with an ordered porous connected network via an ice template method.Two-dimensional(2D)hybrid nanosheets are parallelly arranged with constant spacing and interconnected by a tentacle bridge to form a 3D oriented porous cellular structure.Furthermore,the interlamellar spacing can be effectively tuned by regulating the content of carbon nanosheets(CNs).The optimized 3D-oriented network effectively extends EM wave transmission paths and improves impedance matching.When the thickness is 2.5 mm,CNMX3 achieves a strong reflection loss(RL)intensity of-48.5 dB and a broad effective absorption bandwidth(EAB)of 5.2 GHz under a filling ratio of only 7 wt%.Moreover,CNMX4 reaches a broad EAB of 5.8 GHz at a thickness of only 2.1 mm.Computer simulation technology(CST)analyses were also performed to reveal the microwave absorption mechanism and demonstrate the potential application of the aerogel in EM stealth technology.展开更多
Development of high-performance microwave absorption materials(MAM)with stabilized magnetic properties at high temperatures is specifically essential but remains challenging.Moreover,the Snoke's limitation restrai...Development of high-performance microwave absorption materials(MAM)with stabilized magnetic properties at high temperatures is specifically essential but remains challenging.Moreover,the Snoke's limitation restrains the microwave absorption(MA)property of magnetic materials.Modulating alloy components is considered an effective way to solve the aforementioned problems.Herein,a hollow medium-entropy FeCoNiAl alloy with a stable magnetic property is prepared via simple spray-drying and two-step annealing for efficient MA.FeCoNiAl exhibited an ultrabroad effective absorption band(EAB)of 5.84 GHz(12.16–18 GHz)at a thickness of just 1.6 mm,revealing an excellent absorption capability.Furthermore,the MA mechanism of FeCoNiAl is comprehensively investigated via off-axis holography.Finally,the electromagnetic properties,antioxidant properties,and residual magnetism at high temperatures of FeCoNiAl alloys are summarized in detail,providing new insights into the preparation of MAM operating at elevated temperatures.展开更多
Magnetic/dielectric composite materials with numerous heterointerfaces are highly promising functional materials, which are widely applied in the fields of electromagnetic wave absorption. Constructing heterogeneous s...Magnetic/dielectric composite materials with numerous heterointerfaces are highly promising functional materials, which are widely applied in the fields of electromagnetic wave absorption. Constructing heterogeneous structure is beneficial to further enhance the microwave absorption performance of composite materials. However, the process of constructing multi-heterogeneous interfaces is extremely complex. In this work, hollow porous FeCo/Cu/CNTs composite microspheres are prepared by the simple spray drying method and subsequently two-step annealing treatment, which possess abundant heterogeneous interfaces, unique three-dimensional conductive network and magnetic coupling network. This unique structure is beneficial to improving the ability of dielectric loss and magnetic loss, and then achieving an excellent microwave absorption performance. The prepared FeCo/Cu/CNTs-1 composite microspheres maintain a minimum reflection loss (RL) of −48.1 dB and a maximum effective absorption bandwidth of 5.76 GHz at a thickness of 1.8 mm. Generally, this work provides a new idea for designing multi-heterogeneous of microwave absorbing materials.展开更多
Yolk–shell urchin-like porous Co_(3)O_(4)/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere.High reversible specific capacity,long cyc...Yolk–shell urchin-like porous Co_(3)O_(4)/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere.High reversible specific capacity,long cycling stability,and excellent rate capability were achieved for the material due to its specific yolk–shell urchin-like porous structure and coated carbon layers.The pores distributed on the yolk and shell,as well as the gap between the yolk and shell,provide numerous pathways for the penetration of electrolyte,and enhance the reversible specific capacity(the initial discharge specific capacity was as high as 1405.7 mA h g^(-1) at 0.1 C).Meanwhile,the stress and volume expansion could be greatly released and relieved through the pores,and long cycling stability was achieved(a high reversible specific capacity of 502.7 mA h g^(-1) was maintained after 1000 cycles at 5 C).The coated carbon layers greatly enhance the conductivity of the yolk–shell urchin-like porous Co_(3)O_(4)/NiO microspheres,accelerate the transmission of electrons,and improve their rate performance(a reversible specific capacity of 397.5 mA h g^(-1) was achieved when the current density was increased to 10 C).展开更多
基金support of the National Natural Science Foundation of China(Nos.52302110,52202105,and 52101093)the Shanghai Pujiang Program(No.22PJ1401000)+1 种基金the Scientific Research Program of Shaanxi Provincial Science and Technology Department(No.2024JC-YBQN-0538)the Innovation Capability Support Program of Shaanxi(No.2024ZC-KJXX-082).
文摘Three-dimensional(3D)porous aerogels have been regarded as lightweight and effective electromagnetic(EM)absorbers,but the rational design of components with ordered macroscopic structures at low cost is still a major challenge.In this work,we constructed an ultralight biomass-derived carbon nanosheet/MXene(CNMX)composite aerogel with an ordered porous connected network via an ice template method.Two-dimensional(2D)hybrid nanosheets are parallelly arranged with constant spacing and interconnected by a tentacle bridge to form a 3D oriented porous cellular structure.Furthermore,the interlamellar spacing can be effectively tuned by regulating the content of carbon nanosheets(CNs).The optimized 3D-oriented network effectively extends EM wave transmission paths and improves impedance matching.When the thickness is 2.5 mm,CNMX3 achieves a strong reflection loss(RL)intensity of-48.5 dB and a broad effective absorption bandwidth(EAB)of 5.2 GHz under a filling ratio of only 7 wt%.Moreover,CNMX4 reaches a broad EAB of 5.8 GHz at a thickness of only 2.1 mm.Computer simulation technology(CST)analyses were also performed to reveal the microwave absorption mechanism and demonstrate the potential application of the aerogel in EM stealth technology.
基金supported by the Ministry of Science and Technology of China(No.2021YFA1200600)the National Natural Science Foundation of China(Nos.52231007,12327804,22088101,51725101,and T2321003)+4 种基金the Science and Technology Research Project of Jiangxi Provincial Department of Education(No.GJJ200338)Key Research Project of Zhejiang Lab(No.2021PE0AC02)the“Chenguang Program”by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA04)sponsored by Shanghai Sailing Program(No.21YF1401800)the Fund of Science and Technology on Surface Physics and Chemistry Laboratory(No.JCKYS2023120201).
文摘Development of high-performance microwave absorption materials(MAM)with stabilized magnetic properties at high temperatures is specifically essential but remains challenging.Moreover,the Snoke's limitation restrains the microwave absorption(MA)property of magnetic materials.Modulating alloy components is considered an effective way to solve the aforementioned problems.Herein,a hollow medium-entropy FeCoNiAl alloy with a stable magnetic property is prepared via simple spray-drying and two-step annealing for efficient MA.FeCoNiAl exhibited an ultrabroad effective absorption band(EAB)of 5.84 GHz(12.16–18 GHz)at a thickness of just 1.6 mm,revealing an excellent absorption capability.Furthermore,the MA mechanism of FeCoNiAl is comprehensively investigated via off-axis holography.Finally,the electromagnetic properties,antioxidant properties,and residual magnetism at high temperatures of FeCoNiAl alloys are summarized in detail,providing new insights into the preparation of MAM operating at elevated temperatures.
基金supported by the National Natural Science Foundation of China(Nos.52231007,12327804,T2321003,and 22088101)in part by the National Key Research Program of China(No.2021YFA1200600)+2 种基金the Science and Technology Research Project of Jiangxi Provincial Department of Education(No.GJJ200338)the Fund of Science and Technology on Surface Physics and Chemistry Laboratory(No.JCKYS2023120201)the Fund of Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE(No.KB202401).
文摘Magnetic/dielectric composite materials with numerous heterointerfaces are highly promising functional materials, which are widely applied in the fields of electromagnetic wave absorption. Constructing heterogeneous structure is beneficial to further enhance the microwave absorption performance of composite materials. However, the process of constructing multi-heterogeneous interfaces is extremely complex. In this work, hollow porous FeCo/Cu/CNTs composite microspheres are prepared by the simple spray drying method and subsequently two-step annealing treatment, which possess abundant heterogeneous interfaces, unique three-dimensional conductive network and magnetic coupling network. This unique structure is beneficial to improving the ability of dielectric loss and magnetic loss, and then achieving an excellent microwave absorption performance. The prepared FeCo/Cu/CNTs-1 composite microspheres maintain a minimum reflection loss (RL) of −48.1 dB and a maximum effective absorption bandwidth of 5.76 GHz at a thickness of 1.8 mm. Generally, this work provides a new idea for designing multi-heterogeneous of microwave absorbing materials.
基金supported by the National Natural Science Foundation of China(51725101,11727807,51672050,61790581)the Ministry of Science and Technology of China(973 Project No.2018YFA0209102)the science and technology research project of Jiangxi Provincial Department of Education(GJJ200338).
文摘Yolk–shell urchin-like porous Co_(3)O_(4)/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere.High reversible specific capacity,long cycling stability,and excellent rate capability were achieved for the material due to its specific yolk–shell urchin-like porous structure and coated carbon layers.The pores distributed on the yolk and shell,as well as the gap between the yolk and shell,provide numerous pathways for the penetration of electrolyte,and enhance the reversible specific capacity(the initial discharge specific capacity was as high as 1405.7 mA h g^(-1) at 0.1 C).Meanwhile,the stress and volume expansion could be greatly released and relieved through the pores,and long cycling stability was achieved(a high reversible specific capacity of 502.7 mA h g^(-1) was maintained after 1000 cycles at 5 C).The coated carbon layers greatly enhance the conductivity of the yolk–shell urchin-like porous Co_(3)O_(4)/NiO microspheres,accelerate the transmission of electrons,and improve their rate performance(a reversible specific capacity of 397.5 mA h g^(-1) was achieved when the current density was increased to 10 C).
