The studied sample is a metallic glass in Fe-Si-B system. It is developed with the nominal composition of Fe735-Cu1-Ta3-Si13.5-B9 by single-roller melt spinning technique in air. The dielectric constant and loss facto...The studied sample is a metallic glass in Fe-Si-B system. It is developed with the nominal composition of Fe735-Cu1-Ta3-Si13.5-B9 by single-roller melt spinning technique in air. The dielectric constant and loss factor have been measured both for as cast and annealed samples using Agilent Impedance analyzer. They are found to decrease with frequency up to 10 MHz and remain constant afterwards. The decrease of dielectric constant and loss factor with frequency is due to ceasing of orientational polarizability. Their constancy is owing to presence of only electronic contribution to its polarizability above 10 MHz. Three distinct regions （1-4 MHz, 4-10 MHz and 10 MHz-1 GHz） also noticed from its frequency dependence, which might make it useful in switching and sensor devices. The temperature dependence of dielectric constant and loss factor maintain inverse relationship： （1） dielectric constant increases, and （2） loss factor decreases with annealing temperature for structural relaxation due to thermal agitation.展开更多
Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is chal...Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is challenging.Herein,we report a general and feasible strategy to combine electrospinning with a phase conversion method to decorate polyacrylonitrile nanofibers(PAN NFs)with CuMOF(HKUST-1).The strategy is based on the combination of surface pretreatment of the NFs with Cu(OH)_(2) and a subsequent phase conversion into HKUST-1 crystals(PCHKUST-1).A significant higher loading of HKUST-1 in the PAN NF matrix was achieved by the phase conversion method compared with direct electrospinning of MOF slurries or insitu growth of MOF crystals on NFs.As a result,the hierarchical structured PC(phase conversion)-HKUST-1 NFs revealed the highest gravimetric storage capacity of 86 cm^(3) g^(-1)(STP)at 3500 kPa and 298 K for methane(CH_(4)),which is higher than other HKUST-1 NFs reported previously.The improved CH_(4) uptake can be explained by the high loading of HKUST-1 due to the high availability of Cu-ions localized on the surface of the NFs during the phase conversion process,resulting in high surface area and excellent gas access of the phase converted HKUST-1.Thus,the developed strategy of structuring MOFs could be of interest for the fabrication of tailor-made MOF NF architectures for other energy and environmental applications.展开更多
Electrospinning is firstly used to one-pot synthesis of Li3VO4@C nanofibers in a large scale. Although with the presence of organic sources in synthesis process, the pure phase Li3VO4 with superior nanofibrous morphol...Electrospinning is firstly used to one-pot synthesis of Li3VO4@C nanofibers in a large scale. Although with the presence of organic sources in synthesis process, the pure phase Li3VO4 with superior nanofibrous morphology is still successfully obtained through adjusting different heat treatment processes and different vanadium sources. The prepared Li3VO4@C nanofibers exhibit a unique structure in which nanosized Li3VO4 particles are uniformly embedded in amorphous carbon matrix. Compared with LiBVO4/C powder, Li3VO4@C nanofibers display enhanced reversible capacity of 451 mAhg^-1 at 40mAg^-1 with an increased initial coulombic efficiency of 82.3%, and the capacity can remain at 394 mAh g ^-1 after 100 cycles. This superior electrochemical performance can be attributed to its unique structure which ensures a high reactivity by nanosized Li3VO4, more stable electrode/electrolyte interface by carbon encapsulation, improved electronic conductivity and buffered volume changes by flexible carbon matrix. The electrospinning technology provides an effective method to obtain high performance Li3VO4 as a promising anode material for lithium-ion batteries.展开更多
文摘The studied sample is a metallic glass in Fe-Si-B system. It is developed with the nominal composition of Fe735-Cu1-Ta3-Si13.5-B9 by single-roller melt spinning technique in air. The dielectric constant and loss factor have been measured both for as cast and annealed samples using Agilent Impedance analyzer. They are found to decrease with frequency up to 10 MHz and remain constant afterwards. The decrease of dielectric constant and loss factor with frequency is due to ceasing of orientational polarizability. Their constancy is owing to presence of only electronic contribution to its polarizability above 10 MHz. Three distinct regions （1-4 MHz, 4-10 MHz and 10 MHz-1 GHz） also noticed from its frequency dependence, which might make it useful in switching and sensor devices. The temperature dependence of dielectric constant and loss factor maintain inverse relationship： （1） dielectric constant increases, and （2） loss factor decreases with annealing temperature for structural relaxation due to thermal agitation.
基金supported by the Grande Solution Project“HiGradeGas”(48279)Innovation Fund Denmark,exploring NFs-based adsorbents for biogas upgrading and storage+1 种基金the Danish Research Council to provide funding to support fundamental research on electrospinning(8022-00237B)for investigating NFs structures for enzyme immobilization(6111-00232B)。
文摘Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is challenging.Herein,we report a general and feasible strategy to combine electrospinning with a phase conversion method to decorate polyacrylonitrile nanofibers(PAN NFs)with CuMOF(HKUST-1).The strategy is based on the combination of surface pretreatment of the NFs with Cu(OH)_(2) and a subsequent phase conversion into HKUST-1 crystals(PCHKUST-1).A significant higher loading of HKUST-1 in the PAN NF matrix was achieved by the phase conversion method compared with direct electrospinning of MOF slurries or insitu growth of MOF crystals on NFs.As a result,the hierarchical structured PC(phase conversion)-HKUST-1 NFs revealed the highest gravimetric storage capacity of 86 cm^(3) g^(-1)(STP)at 3500 kPa and 298 K for methane(CH_(4)),which is higher than other HKUST-1 NFs reported previously.The improved CH_(4) uptake can be explained by the high loading of HKUST-1 due to the high availability of Cu-ions localized on the surface of the NFs during the phase conversion process,resulting in high surface area and excellent gas access of the phase converted HKUST-1.Thus,the developed strategy of structuring MOFs could be of interest for the fabrication of tailor-made MOF NF architectures for other energy and environmental applications.
基金supported by the National Natural Science Foundation of China (21571073, 51302099, 51472097)the Ministry of Science and Technology of China (2015CB932600)+2 种基金the Hubei Provincial Natural Science Foundation (2016CFA031)the Program for Huazhong University of Science and Technology (HUST) Interdisciplinary Innovation Team (2015ZDTD038)the Fundamental Research Funds for the Central University (2017KFKJXX007)
文摘Electrospinning is firstly used to one-pot synthesis of Li3VO4@C nanofibers in a large scale. Although with the presence of organic sources in synthesis process, the pure phase Li3VO4 with superior nanofibrous morphology is still successfully obtained through adjusting different heat treatment processes and different vanadium sources. The prepared Li3VO4@C nanofibers exhibit a unique structure in which nanosized Li3VO4 particles are uniformly embedded in amorphous carbon matrix. Compared with LiBVO4/C powder, Li3VO4@C nanofibers display enhanced reversible capacity of 451 mAhg^-1 at 40mAg^-1 with an increased initial coulombic efficiency of 82.3%, and the capacity can remain at 394 mAh g ^-1 after 100 cycles. This superior electrochemical performance can be attributed to its unique structure which ensures a high reactivity by nanosized Li3VO4, more stable electrode/electrolyte interface by carbon encapsulation, improved electronic conductivity and buffered volume changes by flexible carbon matrix. The electrospinning technology provides an effective method to obtain high performance Li3VO4 as a promising anode material for lithium-ion batteries.
