Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative stru...Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption.Particularly,hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials,providing immense potential for creating versatile electromagnetic wave absorption materials.Herein,an exceptional multi-dimensional hierarchical structure was meticulously devised,unleashing the full microwave attenuation capabilities through in situ growth,selfreduction,and multi-heterogeneous interface integration.The hierarchical structure features a three-dimensional carbon framework,where magnetic nanoparticles grow in situ on the carbon skeleton,creating a necklace-like structure.Furthermore,magnetic nanosheets assemble within this framework.Enhanced impedance matching was achieved by precisely adjusting component proportions,and intelligent integration of diverse interfaces bolstered dielectric polarization.The obtain Fe_(3)O_(4)-Fe nanoparticles/carbon nanofibers/Al-Fe_(3)O_(4)-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss(RLmin)value of−59.3 dB and an effective absorption bandwidth(RL≤−10 dB)extending up to 5.6 GHz at 2.2 mm.These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.展开更多
Self-healing superhydrophobic polyvinylidene fluoride/Fe3O4@polypyrrole （F- PVDF/FeBO4@PPyx） fibers with core-sheath structure were successfully fabricated by electrospinning of a PVDF/Fe3O4 mixture and in situ chem...Self-healing superhydrophobic polyvinylidene fluoride/Fe3O4@polypyrrole （F- PVDF/FeBO4@PPyx） fibers with core-sheath structure were successfully fabricated by electrospinning of a PVDF/Fe3O4 mixture and in situ chemical oxidative polymerization of pyrrole, followed by chemical vapor deposition with fluoroalkyl silane. The F-PVDF/Fe3O4@PPy0.075 fiber film produces a superhydrophobic surface with self-healing behavior, which can repetitively and automatically restore superhydrophobicity when the surface is chemically damaged. Moreover, the maximum refection loss （Ru） of the F-PVDF/Fe304@PPy0.075 fiber film reaches -21.5 dB at 16.8 GHz and the RL below -10 dB is in the frequency range of 10.6-16.5 GHz with a thickness of 2.5 mm. The microwave absorption performance is attributed to the synergetic effect between dielectric loss and magnetic loss originating from PPy, PVDF and Fe3O4. As a consequence, preparing such F-PVDF/Fe3O4@PPyx fibers in this manner provides a simple and effective route to develop multi-functional microwave absorbing materials for practical applications.展开更多
Developing efficient metal-free bi-functional electrocatalysts is required to reduce costs and improve the slow oxygen reduction reaction （ORR） and oxygen evo- lution reaction （OER） kinetics in electrochemical sys...Developing efficient metal-free bi-functional electrocatalysts is required to reduce costs and improve the slow oxygen reduction reaction （ORR） and oxygen evo- lution reaction （OER） kinetics in electrochemical systems. Porous N-doped carbon nanotubes （NCNTs） were fabri- cated by KOH activation and pyrolysis of polypyrrole nanotubes. The NCNTs possessed a large surface area of more than 1,000 m2 g-1. NCNT electrocatalysts, particu- larly those annealed at 900 ℃, exhibited excellent ORR electrocatalytic performance. Specifically, they yielded a more positive onset potential, higher current density, and long-term operation stability in alkaline media, when compared with a commercially available 20 wt% Pt/C catalyst. This resulted from the synergetic effect between the dominant pyridinic/graphitic-N species and the porous tube structures. The NCNT electrocatalyst also exhibited good performance for the OER. The metal-free porous nitrogen-doped carbon nanomaterials were prepared from low cost and environmentally friendly precursors. They are potential alternatives to Pt/C catalysts, for electrochemical energy conversion and storage.展开更多
Oil sorbents are an attractive option for oil-spill cleanup as they may be used for collection and complete removal of oil without adversely affecting the environment. However, traditional oil sorbents exhibit low oil...Oil sorbents are an attractive option for oil-spill cleanup as they may be used for collection and complete removal of oil without adversely affecting the environment. However, traditional oil sorbents exhibit low oil/water separation efficiency and/or low oil-sorption capacity. In this study, an ultra-high performance graphene/polyurethane （PU） sponge has been successfully obtained by in situ polymerization in the presence of graphene dispersed in N-methylpyrrolidone （NMP）. During polymerization, the NMP/graphene dispersion not only serves as a weak amine catalyst for the formation of the sponge, but promotes fixation of the graphene sheets in the framework of the PU sponge owing to the strong dipole interaction between NMP and graphene. The as-prepared graphene/PU sponge was used as an absorbing material for the continuous removal of oil from oil-spill water. The graphene/PU sponge can continuously and rapidly remove oils from immiscible oil/water mixtures in corrosive solutions, including strong acids and bases, hot water, and ice water, with an excellent separation efficiency of above 99.99%. In addition, the as-prepared graphene/PU sponge was effective in separating surfactant-stabilized emulsions with a high separation efficiency of 〉99.91%.展开更多
基金funded by the National Natural Science Foundation of China(No.51873004).
文摘Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption.Particularly,hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials,providing immense potential for creating versatile electromagnetic wave absorption materials.Herein,an exceptional multi-dimensional hierarchical structure was meticulously devised,unleashing the full microwave attenuation capabilities through in situ growth,selfreduction,and multi-heterogeneous interface integration.The hierarchical structure features a three-dimensional carbon framework,where magnetic nanoparticles grow in situ on the carbon skeleton,creating a necklace-like structure.Furthermore,magnetic nanosheets assemble within this framework.Enhanced impedance matching was achieved by precisely adjusting component proportions,and intelligent integration of diverse interfaces bolstered dielectric polarization.The obtain Fe_(3)O_(4)-Fe nanoparticles/carbon nanofibers/Al-Fe_(3)O_(4)-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss(RLmin)value of−59.3 dB and an effective absorption bandwidth(RL≤−10 dB)extending up to 5.6 GHz at 2.2 mm.These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.
基金The work is supported by the National Natural Sdence Foundation of China （Nos. 51273008, 51473008, and 21103006）, Beijing Natural Science Foundation （No. 2132030） and the National Basic Research Program of China （No. 2012CB933200）.
文摘Self-healing superhydrophobic polyvinylidene fluoride/Fe3O4@polypyrrole （F- PVDF/FeBO4@PPyx） fibers with core-sheath structure were successfully fabricated by electrospinning of a PVDF/Fe3O4 mixture and in situ chemical oxidative polymerization of pyrrole, followed by chemical vapor deposition with fluoroalkyl silane. The F-PVDF/Fe3O4@PPy0.075 fiber film produces a superhydrophobic surface with self-healing behavior, which can repetitively and automatically restore superhydrophobicity when the surface is chemically damaged. Moreover, the maximum refection loss （Ru） of the F-PVDF/Fe304@PPy0.075 fiber film reaches -21.5 dB at 16.8 GHz and the RL below -10 dB is in the frequency range of 10.6-16.5 GHz with a thickness of 2.5 mm. The microwave absorption performance is attributed to the synergetic effect between dielectric loss and magnetic loss originating from PPy, PVDF and Fe3O4. As a consequence, preparing such F-PVDF/Fe3O4@PPyx fibers in this manner provides a simple and effective route to develop multi-functional microwave absorbing materials for practical applications.
基金This work was supported by the National Nat- ural Science Foundation of China （51273008, 51473008）, and the National Basic Research Program of China （2012CB933200）.
文摘Developing efficient metal-free bi-functional electrocatalysts is required to reduce costs and improve the slow oxygen reduction reaction （ORR） and oxygen evo- lution reaction （OER） kinetics in electrochemical systems. Porous N-doped carbon nanotubes （NCNTs） were fabri- cated by KOH activation and pyrolysis of polypyrrole nanotubes. The NCNTs possessed a large surface area of more than 1,000 m2 g-1. NCNT electrocatalysts, particu- larly those annealed at 900 ℃, exhibited excellent ORR electrocatalytic performance. Specifically, they yielded a more positive onset potential, higher current density, and long-term operation stability in alkaline media, when compared with a commercially available 20 wt% Pt/C catalyst. This resulted from the synergetic effect between the dominant pyridinic/graphitic-N species and the porous tube structures. The NCNT electrocatalyst also exhibited good performance for the OER. The metal-free porous nitrogen-doped carbon nanomaterials were prepared from low cost and environmentally friendly precursors. They are potential alternatives to Pt/C catalysts, for electrochemical energy conversion and storage.
文摘Oil sorbents are an attractive option for oil-spill cleanup as they may be used for collection and complete removal of oil without adversely affecting the environment. However, traditional oil sorbents exhibit low oil/water separation efficiency and/or low oil-sorption capacity. In this study, an ultra-high performance graphene/polyurethane （PU） sponge has been successfully obtained by in situ polymerization in the presence of graphene dispersed in N-methylpyrrolidone （NMP）. During polymerization, the NMP/graphene dispersion not only serves as a weak amine catalyst for the formation of the sponge, but promotes fixation of the graphene sheets in the framework of the PU sponge owing to the strong dipole interaction between NMP and graphene. The as-prepared graphene/PU sponge was used as an absorbing material for the continuous removal of oil from oil-spill water. The graphene/PU sponge can continuously and rapidly remove oils from immiscible oil/water mixtures in corrosive solutions, including strong acids and bases, hot water, and ice water, with an excellent separation efficiency of above 99.99%. In addition, the as-prepared graphene/PU sponge was effective in separating surfactant-stabilized emulsions with a high separation efficiency of 〉99.91%.
