Efficient and environmentally friendly production of high-quality continuous fiber coatings using current preparation methods is highly challenging due to issues such as scale and batch processing restrictions,low dep...Efficient and environmentally friendly production of high-quality continuous fiber coatings using current preparation methods is highly challenging due to issues such as scale and batch processing restrictions,low deposition rate,high energy consumption,and utilization of multiple environmentally hazardous steps.To address these challenges,we propose a stable and efficient wet chemical deposition coating method for high-throughput online continuous preparation of boron nitride(BN)coatings on ceramic fibers under an ambient environment.Our process involves surface modification,in-situ wet chemical deposition,and heat treatment,and all seamlessly connecting with the ceramic fiber preparation process through continuous stretching.Hydrophilic groups were introduced via surface modification enhancing wettability of the fiber surface with impregnating solution.An in-situ reaction and atom migration improve uniformity and binding of the coating.As a result,outstanding impregnation and adhesion properties are achieved.A comprehensive analysis to evaluate the impact of the BN coatings was conducted,which demonstrates that the BN-coated fibers exhibit a remarkable 36%increase in tensile strength,a 133%increase in fracture toughness,and enhanced temperature resistance of up to 1600℃.It provides a secure and efficient platform for cost-effective production of functional and high-quality coatings through targeted surface modification and rapid stretching impregnation.展开更多
Ceramic nanofibers with robust mechanical properties,high-temperature resistance,and superior thermal insulation performance are promising thermal insulators used under extreme conditions.However,developing of ceramic...Ceramic nanofibers with robust mechanical properties,high-temperature resistance,and superior thermal insulation performance are promising thermal insulators used under extreme conditions.However,developing of ceramic fibers with both low solid thermal conductivity(λs)and low infrared radiation thermal conductivity(λr)is still a great challenge.Herein,according to the Ioffe-Regel limit theory,we report a novel SiZrNOC nanofiber membrane(NFM)with a typically amorphous structure by combining the electrospinning method and high-temperature pyrolysis technique in a NH3 atmosphere.The prepared SiZrNOC NFM has a high tensile strength(1.98±0.09 MPa),excellent thermal stability(1100℃in air),and superior thermal insulation performance.The thermal conductivity of SiZrNOC NFM was 0.112 W·m^(−1)·K^(−1) at 1000℃,which is obviously lower than that of the traditional ceramic fiber membranes(>0.2 W·m^(−1)·K^(−1) at 1000℃).In addition,the prepared SiZrNOC NFM-reinforced SiO2 aerogel composites(SiZrNOCf/SiO2 ACs)exhibited ultralow thermal conductivity of 0.044 W·m^(−1)·K^(−1) at 1000℃,which was the lowest value for SiO2-based aerogel composites ever reported.Such superior thermal insulation performance of SiZrNOC NFMs was mainly due to significant decreasing of solid heat conduction and thermal radiation by the fancy amorphous microstructure and high infrared shielding compositions.This work not only provides a promising high-temperature thermal insulator,but also offers a novel route to develop other high-performance thermal insulating materials.展开更多
The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent ga...The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete{001}facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete{001}facets is 70%higher than that of defective TiO2 nanoplates, which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 can be contributed to fewer adsorption sites and blocked electron transfer. This work presents a more direct evidence for explaining the important role of the complete{001}crystal facets in high sensitivity of TiO2 and also provides a new insight for preparing high sensitivity sensing materials.展开更多
Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated in...Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated into highly conductive frameworks, simultaneously providing more active sites and higher conductivity. The NG was in situ grown on carbon fibers derived from silk cocoon (SCCf) using a simple one-step thermal treatment. The resulting product (NG-SCCf), possessing a meso-/macroporous structure with three-dimensional (3D) interconnected networks, exhibits an onset potential that is only 0.1 V less negative than that of Pt/C and shows stability and methanol tolerance superior to those of Pt/C in alkaline media. Moreover, in the absence of Pt as co-catalyst, NG-SCCf shows a photocatalytic H2 production rate of 66.0 ~tmol-h l.g 1, 4.4-fold higher than that of SCCf. This outstanding activity is intimately related to the in situ grown NG, hierarchically porous structure, and 3D interconnected networks, which not only introduce more active sites but also enable smooth electron transfer, mass transport, and effective separation of electron-hole pairs. Considering the abundance of the green raw material in combination with easy and low-cost preparation, this work contributes to the development of advanced sustainable catalysts in energy storage/conversion fields, such as electro- and photocatalysis.展开更多
SiBN fibers are one of the most admirable microwave-transparent reinforced materials for high Mach number aircrafts.Currently,the detailed high-temperature oxidation behavior of SiBN fibers has not been studied yet.In...SiBN fibers are one of the most admirable microwave-transparent reinforced materials for high Mach number aircrafts.Currently,the detailed high-temperature oxidation behavior of SiBN fibers has not been studied yet.In this work,we studied the high-temperature oxidation behavior of SiBN fibers with different boron contents at the temperature range of 1000-1400℃in air.SiBN fibers started to be oxidized at 1100℃,with Si_(3)N_(4) and BN phase oxidized to SiO2 and B_(2)O_(3),respectively.Due to the gasification and the escape of molten B_(2)O_(3) at high temperatures,amorphous SiO_(2) could be remained at the fiber surface.As the fiber further oxidized,the molten B_(2)O_(3) at the inside may infiltrate into the fiber interior to react with Si_(3)N_(4),causing the precipitation of hexagonal boron nitride(h-BN)nanoparticles and the formation of SiO_(2)/BN layer.Finally,complex oxidation layers with two distinct concentric sublayers accompanied with two transition sublayers could be formed after the oxidizing treatment.展开更多
The strategy of combining highly conductive frameworks with abundant active sites is desirable in the preparation of alternative catalysts to commercial Pt/C for the oxygen reduction reaction (ORR). In this study, N...The strategy of combining highly conductive frameworks with abundant active sites is desirable in the preparation of alternative catalysts to commercial Pt/C for the oxygen reduction reaction (ORR). In this study, N-doped graphene (NG) and carbon nanotubes (CNT) were grown in-situ on Co-containing carbon nanofibers (CNF) to form three-dimensional (3D) interconnected networks. The NG and CNT bound the interlaced CNF together, facilitating electron transfer and providing additional active sites. The 3D interconnected fiber networks exhibited excellent ORR catalytic behavior with an onset potential of 0.924 V (vs. reversible hydrogen electrode) and a higher current density than Pt/C beyond 0.720 V. In addition, the hybrid system exhibited superior stability and methanol tolerance to Pt/C in alkaline media. This method can be extended to the design of other 3D interconnected network architectures for energy storage and conversion applications.展开更多
Silicon carbide (SIC) has been considered a promising metal-free photocatalyst due to its unique photoelectrical properties and thermal/chemical stability. However, its performance suffers from the fast recombinatio...Silicon carbide (SIC) has been considered a promising metal-free photocatalyst due to its unique photoelectrical properties and thermal/chemical stability. However, its performance suffers from the fast recombination of charge carriers. Herein, we report mesoporous SiC nanofibers with in situ embedded graphitic carbon (SiC NFs-Cx) synthesized via a one-step carbothermal reduction between electrospun carbon nanofibers and Si powders. In the absence of a noble metal co-catalyst, the hydrogen evolution efficiency of SiC NFs-Cx is significantly improved under both simulated solar light (180.2 μmol.g-1.h-1) and visible light irradiation (31.0 ~amol-g-l-h-~) in high-pH solution. The efficient simultaneous separation of charge carriers plays a critical role in the high photocatalytic activity. The embedded carbon can swiftly transfer the photogenerated electrons and improve light absorption, whereas the additional hydroxyl anions (OH-) in high- pH solution can accelerate the trapping of holes. Our results demonstrate that the production of SiC NFs-Cx, which contains exclusively earth-abundant elements, scaled up, and is environmentally friendly, has great potential for practical applications. This work may provide a new pathway for designing stable, low- cost, high efficiency, and co-catalyst-free photocatalysts.展开更多
Electrocatalytic conversion of oxygen holds great potential for clean energy technologies, including water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. The development of highly efficie...Electrocatalytic conversion of oxygen holds great potential for clean energy technologies, including water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. The development of highly efficient and inexpensive oxygen electrocatalysts as replacements for precious metal-based catalysts is vitally important for large-scale practical application in the future. A bifunctional oxygen electrocatalyst based on FeCo nanoparticles/N-doped carbon core-shell spheres supported on N-doped graphene sheets was prepared via one-step pyrolysis of graphitic carbon nitride and acetylacetonates. The optimized product exhibited an oxygen electrode activity of 0.87 V and excellent durability. The remarkable performance is mainly attributed to the synergetic effect arising from the FeCo nanoparticles and N-doped carbon shell. This study introduces an inexpensive and simple way to develop highly active bifunctional oxygen electrocatalysts.展开更多
Self-supported transition-metal single-atom catalysts(SACs)facilitate the industrialization of electrochemical CO_(2) reduction,but suffer from high structural heterogeneity with limited catalytic selectivity.Here we ...Self-supported transition-metal single-atom catalysts(SACs)facilitate the industrialization of electrochemical CO_(2) reduction,but suffer from high structural heterogeneity with limited catalytic selectivity.Here we present a facile and scalable approach for the synthesis of self-supported nickel@nitrogen-doped carbon nanotubes grown on carbon nanofiber membrane(Ni@NCNTs/CFM),where the Ni single atoms and nanoparticles(NPs)are anchored on the wall and inside of nitrogen-doped carbon nanotubes,respectively.The side effect of Ni NPs was further effectively inhibited by alloying Ni with Cu atoms to alter their d-band center,which is theoretically predicted and experimentally proved.The optimal catalyst Ni_(9)Cu_(1)@NCNTs/CFM exhibits an ultrahigh CO Faradic efficiency over 97%at-0.7 V versus reversible hydrogen electrode.Additionally,this catalyst shows excellent mechanical strength which can be directly used as a self-supporting catalyst for Zn-CO_(2) battery with a peak power density of~0.65 mW/cm^(2)at2.25 mA/cm^(2) and a long-term stability for 150 cycles.This work opens up a general avenue to facilely prepare self-supported SACs with unitary single-atom site for CO_(2) utilization.展开更多
基金This work was supported by the Natural Science Foundation for Excellent Young Scholars of Hunan Province(No.2021JJ20048).
文摘Efficient and environmentally friendly production of high-quality continuous fiber coatings using current preparation methods is highly challenging due to issues such as scale and batch processing restrictions,low deposition rate,high energy consumption,and utilization of multiple environmentally hazardous steps.To address these challenges,we propose a stable and efficient wet chemical deposition coating method for high-throughput online continuous preparation of boron nitride(BN)coatings on ceramic fibers under an ambient environment.Our process involves surface modification,in-situ wet chemical deposition,and heat treatment,and all seamlessly connecting with the ceramic fiber preparation process through continuous stretching.Hydrophilic groups were introduced via surface modification enhancing wettability of the fiber surface with impregnating solution.An in-situ reaction and atom migration improve uniformity and binding of the coating.As a result,outstanding impregnation and adhesion properties are achieved.A comprehensive analysis to evaluate the impact of the BN coatings was conducted,which demonstrates that the BN-coated fibers exhibit a remarkable 36%increase in tensile strength,a 133%increase in fracture toughness,and enhanced temperature resistance of up to 1600℃.It provides a secure and efficient platform for cost-effective production of functional and high-quality coatings through targeted surface modification and rapid stretching impregnation.
基金supported by the Defense Industrial Technology Development Program (No.JCKY2017****)the National Natural Science Foundation of China (Nos.51773226,52002400,and 51872329)+2 种基金Natural Science Foundation of Hunan Province (No.2018JJ3603)Key Research and Development of Hunan Province (No.2022GK2027)Research Project of National University of Defense Technology (No.ZK20-08).
文摘Ceramic nanofibers with robust mechanical properties,high-temperature resistance,and superior thermal insulation performance are promising thermal insulators used under extreme conditions.However,developing of ceramic fibers with both low solid thermal conductivity(λs)and low infrared radiation thermal conductivity(λr)is still a great challenge.Herein,according to the Ioffe-Regel limit theory,we report a novel SiZrNOC nanofiber membrane(NFM)with a typically amorphous structure by combining the electrospinning method and high-temperature pyrolysis technique in a NH3 atmosphere.The prepared SiZrNOC NFM has a high tensile strength(1.98±0.09 MPa),excellent thermal stability(1100℃in air),and superior thermal insulation performance.The thermal conductivity of SiZrNOC NFM was 0.112 W·m^(−1)·K^(−1) at 1000℃,which is obviously lower than that of the traditional ceramic fiber membranes(>0.2 W·m^(−1)·K^(−1) at 1000℃).In addition,the prepared SiZrNOC NFM-reinforced SiO2 aerogel composites(SiZrNOCf/SiO2 ACs)exhibited ultralow thermal conductivity of 0.044 W·m^(−1)·K^(−1) at 1000℃,which was the lowest value for SiO2-based aerogel composites ever reported.Such superior thermal insulation performance of SiZrNOC NFMs was mainly due to significant decreasing of solid heat conduction and thermal radiation by the fancy amorphous microstructure and high infrared shielding compositions.This work not only provides a promising high-temperature thermal insulator,but also offers a novel route to develop other high-performance thermal insulating materials.
基金financially supported by the National Natural Science Foundation of China(Nos. 51773226, 61701514)the Natural Science Foundation of Hunan Province(No. 2018JJ3603)
文摘The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy{001}crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective{001}facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete{001}facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete{001}facets is 70%higher than that of defective TiO2 nanoplates, which proves that the{001}facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 can be contributed to fewer adsorption sites and blocked electron transfer. This work presents a more direct evidence for explaining the important role of the complete{001}crystal facets in high sensitivity of TiO2 and also provides a new insight for preparing high sensitivity sensing materials.
基金The work was financially supported by National Natural Science Foundation of China (Nos. 51203182 and 51173202), Foundation for the Author of Excellent Doctoral Dissertation of Hunan Province (No. YB2014B004), Aeronautical Science Foundation of China (No. 20143188004), Key Laboratory of Advanced Textile Materials and Manufacturing Technology (Zhejiang Sci-Tech University), Ministry of Education (No. 2015001), Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle, College of Hunan Province (No. 2016kfjj01), Research Project of NUDT. We thank Tengyuan Wang for help in ORR experiment and helpful discussions.
文摘Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated into highly conductive frameworks, simultaneously providing more active sites and higher conductivity. The NG was in situ grown on carbon fibers derived from silk cocoon (SCCf) using a simple one-step thermal treatment. The resulting product (NG-SCCf), possessing a meso-/macroporous structure with three-dimensional (3D) interconnected networks, exhibits an onset potential that is only 0.1 V less negative than that of Pt/C and shows stability and methanol tolerance superior to those of Pt/C in alkaline media. Moreover, in the absence of Pt as co-catalyst, NG-SCCf shows a photocatalytic H2 production rate of 66.0 ~tmol-h l.g 1, 4.4-fold higher than that of SCCf. This outstanding activity is intimately related to the in situ grown NG, hierarchically porous structure, and 3D interconnected networks, which not only introduce more active sites but also enable smooth electron transfer, mass transport, and effective separation of electron-hole pairs. Considering the abundance of the green raw material in combination with easy and low-cost preparation, this work contributes to the development of advanced sustainable catalysts in energy storage/conversion fields, such as electro- and photocatalysis.
基金supported by the National Natural Science Foundation of China(No.52073304).
文摘SiBN fibers are one of the most admirable microwave-transparent reinforced materials for high Mach number aircrafts.Currently,the detailed high-temperature oxidation behavior of SiBN fibers has not been studied yet.In this work,we studied the high-temperature oxidation behavior of SiBN fibers with different boron contents at the temperature range of 1000-1400℃in air.SiBN fibers started to be oxidized at 1100℃,with Si_(3)N_(4) and BN phase oxidized to SiO2 and B_(2)O_(3),respectively.Due to the gasification and the escape of molten B_(2)O_(3) at high temperatures,amorphous SiO_(2) could be remained at the fiber surface.As the fiber further oxidized,the molten B_(2)O_(3) at the inside may infiltrate into the fiber interior to react with Si_(3)N_(4),causing the precipitation of hexagonal boron nitride(h-BN)nanoparticles and the formation of SiO_(2)/BN layer.Finally,complex oxidation layers with two distinct concentric sublayers accompanied with two transition sublayers could be formed after the oxidizing treatment.
基金The work was financially supported by the National Natural Science Foundation of China (Nos. 51203182 and 51173202), Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics (No. KF201312), Key Laboratory of High Performance Fibers & Products, Ministry of Education, Donghua University, Guangxi Key Laboratory of Information Materials (Guilin University of Electronic Technology) (No. 1210908-01-K), Research Project of NUDT (No. JC13-01-05), Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province, and Aid Program for Innovative Group of National University of Defense Technology.
文摘The strategy of combining highly conductive frameworks with abundant active sites is desirable in the preparation of alternative catalysts to commercial Pt/C for the oxygen reduction reaction (ORR). In this study, N-doped graphene (NG) and carbon nanotubes (CNT) were grown in-situ on Co-containing carbon nanofibers (CNF) to form three-dimensional (3D) interconnected networks. The NG and CNT bound the interlaced CNF together, facilitating electron transfer and providing additional active sites. The 3D interconnected fiber networks exhibited excellent ORR catalytic behavior with an onset potential of 0.924 V (vs. reversible hydrogen electrode) and a higher current density than Pt/C beyond 0.720 V. In addition, the hybrid system exhibited superior stability and methanol tolerance to Pt/C in alkaline media. This method can be extended to the design of other 3D interconnected network architectures for energy storage and conversion applications.
基金The work was financially supported by National Natural Science Foundation of China (Nos. 51173202 and 51203182), Hunan Provincial Natural Science Foundation of China (No. 13JJ4009), State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology) (No. 2014-KF-10), the State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology (No. G201501) and Research Project of National University of Defense Technology (No. JC13-01-05). This work was also supported by Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province and Aid Program for Innovative Group of National University of Defense Technology.
文摘Silicon carbide (SIC) has been considered a promising metal-free photocatalyst due to its unique photoelectrical properties and thermal/chemical stability. However, its performance suffers from the fast recombination of charge carriers. Herein, we report mesoporous SiC nanofibers with in situ embedded graphitic carbon (SiC NFs-Cx) synthesized via a one-step carbothermal reduction between electrospun carbon nanofibers and Si powders. In the absence of a noble metal co-catalyst, the hydrogen evolution efficiency of SiC NFs-Cx is significantly improved under both simulated solar light (180.2 μmol.g-1.h-1) and visible light irradiation (31.0 ~amol-g-l-h-~) in high-pH solution. The efficient simultaneous separation of charge carriers plays a critical role in the high photocatalytic activity. The embedded carbon can swiftly transfer the photogenerated electrons and improve light absorption, whereas the additional hydroxyl anions (OH-) in high- pH solution can accelerate the trapping of holes. Our results demonstrate that the production of SiC NFs-Cx, which contains exclusively earth-abundant elements, scaled up, and is environmentally friendly, has great potential for practical applications. This work may provide a new pathway for designing stable, low- cost, high efficiency, and co-catalyst-free photocatalysts.
基金The work was financially supported by the National Natural Science Foundation of China (No. 51173202), Innovation Foundation for Superior Postgraduate of National University of Defense Technology, Hunan Provincial Innovation Foundation for Postgraduate, Research Project of NUDT (No. ZK16-03-32), Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province and Aid Program for Innovative Group of National University of Defense Technology.
文摘Electrocatalytic conversion of oxygen holds great potential for clean energy technologies, including water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. The development of highly efficient and inexpensive oxygen electrocatalysts as replacements for precious metal-based catalysts is vitally important for large-scale practical application in the future. A bifunctional oxygen electrocatalyst based on FeCo nanoparticles/N-doped carbon core-shell spheres supported on N-doped graphene sheets was prepared via one-step pyrolysis of graphitic carbon nitride and acetylacetonates. The optimized product exhibited an oxygen electrode activity of 0.87 V and excellent durability. The remarkable performance is mainly attributed to the synergetic effect arising from the FeCo nanoparticles and N-doped carbon shell. This study introduces an inexpensive and simple way to develop highly active bifunctional oxygen electrocatalysts.
基金financially supported by the National Natural Science Foundation of China(Nos.51773226,61701514)the Natural Science Foundation of Hunan Province(No.2018JJ3603)。
文摘Self-supported transition-metal single-atom catalysts(SACs)facilitate the industrialization of electrochemical CO_(2) reduction,but suffer from high structural heterogeneity with limited catalytic selectivity.Here we present a facile and scalable approach for the synthesis of self-supported nickel@nitrogen-doped carbon nanotubes grown on carbon nanofiber membrane(Ni@NCNTs/CFM),where the Ni single atoms and nanoparticles(NPs)are anchored on the wall and inside of nitrogen-doped carbon nanotubes,respectively.The side effect of Ni NPs was further effectively inhibited by alloying Ni with Cu atoms to alter their d-band center,which is theoretically predicted and experimentally proved.The optimal catalyst Ni_(9)Cu_(1)@NCNTs/CFM exhibits an ultrahigh CO Faradic efficiency over 97%at-0.7 V versus reversible hydrogen electrode.Additionally,this catalyst shows excellent mechanical strength which can be directly used as a self-supporting catalyst for Zn-CO_(2) battery with a peak power density of~0.65 mW/cm^(2)at2.25 mA/cm^(2) and a long-term stability for 150 cycles.This work opens up a general avenue to facilely prepare self-supported SACs with unitary single-atom site for CO_(2) utilization.