Decomposing growth rate of total factor productivity(TFP)into internal growth effect and the effect of factor reallocation formed by the flow of capital,labor and energy between sectors,we took 23 subsectors as the re...Decomposing growth rate of total factor productivity(TFP)into internal growth effect and the effect of factor reallocation formed by the flow of capital,labor and energy between sectors,we took 23 subsectors as the research object and adopted the multi-sector growth accounting framework(MSGAF)to verify the‘structural bonus hypothesis’from 2005 to 2017.The study drew the following conclusions:First,internal growth effect represented by sectoral technology progress was still the main contributor to TFP growth of the overall economy,but the contribution rate had decreased.Second,the reallocation effect of capital changed from structural burden to structural bonus.Third,the reallocation effect of labor showed a trend of first rising and then falling,changing from structural bonus to structural burden.Forth,the effect of energy reallocation was gradually emerging,with a shift from structural burden to structural bonus.Based on these research results,we argue that more attention should be paid to the efficiency of factor reallocation in addition to the technology progress.The inefficiency of factor reallocation caused by imperfect market and asymmetric information would partially offset the effect of technology progress and hinder the high-quality economic development.In view of the reallocation of capital,labor and energy,we propose the following suggestions:For capital,macro-control and market mechanism should be comprehensively accounted for.Further,capital must be allocated per the principle of profit maximization to ensure that its elasticity and allocation efficiency will be improved.The reallocation of labor should not only be limited to the 3-sector level.More attention should be paid to the marginal output differences within the secondary sector.For energy,attention should be paid to the elasticity of energy output between sectors to avoid inefficient allocation.It is also necessary to accelerate the phase-out of industries with high energy consumption and high pollution,promote the development of low energy industries to encourage‘energy conservation and emission reduction’as well as‘green development’by increasing the effect of energy reallocation.展开更多
Electrochemical production of hydrogen peroxide(H_(2)O_(2))via the two-electron(2e-)pathway of oxygen reduction reaction(ORR)supplies an auspicious alternative to the current industrial anthraquinone process.Nonethele...Electrochemical production of hydrogen peroxide(H_(2)O_(2))via the two-electron(2e-)pathway of oxygen reduction reaction(ORR)supplies an auspicious alternative to the current industrial anthraquinone process.Nonetheless,it still lacks efficient electrocatalysts to achieve high ORR activity together with 2e-selectivity simultaneously.Herein,a boron-doped defective nanocarbon(B-DC)electrocatalyst is synthesized by using fullerene frameworks as the precursor and boric oxide as the boron source.The obtained B-DC materials have a hierarchical porous structure,befitting boron dopants,and abundant topological pentagon defects,exhibiting a high ORR onset potential of 0.78 V and a dominated 2e-selectivity(over 95%).Remarkably,when B-DC electrocatalyst is employed in a real device,it achieves a high H_(2)O_(2) yield rate(247 mg·L^(-1)·h^(-1)),quantitative Faraday efficiency(~100%),and ultrafast organic pollutant degradation rate.The theoretical calculation reveals that the synergistic effect of topological pentagon defects and the incorporation of boron dopants promote the activation of the O_(2) molecule and facilitates the desorption of oxygen intermediate.This finding will be very helpful for the comprehension of the synergistic effect of topological defects and heteroatom dopants for boosting the electrocatalytic performance of nanocarbon toward H_(2)O_(2) production.展开更多
Si alloying in the surface layer of NdFeB magnets was realized by thermal diffusion combined with magnetron sputtering.The surface composition,phase structure and morphology of NdFeB(S-Si)specimens were characterized ...Si alloying in the surface layer of NdFeB magnets was realized by thermal diffusion combined with magnetron sputtering.The surface composition,phase structure and morphology of NdFeB(S-Si)specimens were characterized by an X-ray diffractometer,an X-ray photoelectron spectrometer and a field emission scanning electron microscope,respectively.The corrosion resistance of bare NdFeB(S-Si)was analyzed by static full immersion corrosion test and electrochemical experiments.Effects of sputtering and thermal diffusion on the microstructure and corrosion resistance of the surface layer were studied.Results show that surface alloying layer can effectively improve the corrosion resistance of bare NdFeB with the optimized static total immersion corrosion test time in NdFeB(1S-Si)-800 of 36 h,which is much longer than that of the pristine NdFeB(less than 0.5 h).The E_(corr)of NdFeB(1S-Si)-800 positively shifts from-1.05 to-0.92 V,indicating that the corrosion tendency is obviously lower.The J_(corr)is1.45×10^(-6)A/cm^(2)which is 2 orders of magnitude lower than that of the pristine NdFeB(5.25×10^(-4)A/cm^(2)).The intergranular composite oxides existing in Nd-rich phase contribute to the enhancement of corrosion resistance of Si-surface-alloying NdFeB.展开更多
The CeO2/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized ...The CeO2/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized by a scanning electron microscope and an X-ray diffractometer. The micro hardness of the composite coating was evaluated by a microhardness tester. The corrosive behaviors of the coatings were studied by potentiodynamic polarization curve, electrochemical impedance spectroscopy and neutral salt spray tests. The concentration of CeO2 nanoparticles(NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO2 NPs can enhance the microhardness of the composite coatings. Moreover, the nanoparticles disperse uniformly in the matrix when the concentration is lower than 30 g/L. The microhardness of CeO2/epoxy resin(30 g/L) composite coating is about 63% higher than that of the blank epoxy resin coating. And the NSS time of the CeO2/epoxy resin(30 g/L) composite coated sample can reach 1248 h.Meanwhile, the composite coatings possess no deteriorate influence on the magnetic properties of NdFeB substrates. The anticorrosion mechanisms of the composite coatings on the NdFeB substrate are deeply discussed.展开更多
Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the corro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a...Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the corro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a scanning electron microscope.Corrosion behaviors of the samples with different bias voltages were studied by electrochemical methods and neutral salt spray test,respectively.The bias voltage during the deposition process was optimized according to the coating structures and corrosion resistances.The density and flatness of Al coating increase with increasing the bias voltage,and at the same time the thickness decreases.The coating density and thickness turn to be stable when bias voltage is 1800 V.Also,the corrosion behaviors of PA-PVD Al coatings in different media,such as NaOH,HNO_(3) and NaCl solutions,were studied.The self-corrosion potentials(E_(corr)) of PA-PVD Al coatings almost keep constant in NaOH and HNO_(3) solutions with diffe rent concentrations.However,the self-corrosion current densities(J_(corr)) decrease with the increasing concentrations.E_(corr) shifts to negative potential and J_(corr)decreases gradually when increasing the concentration of NaCl solution.The corrosion mechanisms of Al coatings are discussed based on the corrosion behaviors in different media.展开更多
Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by sca...Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm^(2) and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.展开更多
A novel glucose biosensor based on graphene nanosheets(GNs)modified gold nanowire arrays(AuNWAs)electrode was constructed.Highly ordered gold nanowire arrays were prepared by direct electrodeposition in anodic aluminu...A novel glucose biosensor based on graphene nanosheets(GNs)modified gold nanowire arrays(AuNWAs)electrode was constructed.Highly ordered gold nanowire arrays were prepared by direct electrodeposition in anodic aluminum oxide templates.GNs were synthesized through a public route involving graphite oxidation,exfoliation,and chemical reduction.Field emission scanning electron microscope and high-resolution transmission electron microscope were employed to characterize the asprepared AuNWAs and GNs.Glucose oxidase was immobilized on the surface of GNs-AuNWAs modified electrode via a cross-linking method.The cyclic voltammetry results showed that the GNs-AuNWAs-based glucose biosensors have high catalysis activity to hydrogen peroxide(H2O2)than those modified with GNs or AuNWAs only.Furthermore,amperometric response was employed to detect glucose concentration owing to its simplicity,high selectivity,and relative low cost.Glucose biosensors based on GNs-AuNWAs showed excellent performance with high sensitivity of 40.25 lA cm-2(mmol/L)-1,low detection limit of 0.02 mmol/L,and a linear range from 0.02 to 3 mmol/L.展开更多
A ligand-free nickel-catalyzed Kumada cross-coupling of aryl bromides and tert-butyl Grignard reagents led to the formation of a series of tert-butyl aryls in moderate to good yields, excellent tBu/iBu ratios, and goo...A ligand-free nickel-catalyzed Kumada cross-coupling of aryl bromides and tert-butyl Grignard reagents led to the formation of a series of tert-butyl aryls in moderate to good yields, excellent tBu/iBu ratios, and good functional group compatibility. A radical coupling process is indicated and a mechanism with a Ni(Ⅰ)-Ni(Ⅲ) catalytic cycle is proposed.展开更多
(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnet...(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester,an electrochemical workstation,a microhardness tester,a bending tester,a scanning electron microscope and an X-ray diffractometer.Results show that the addition of Ho can change the main phase structure,optimize the distribution of rare-earth rich(RE-rich) phases in grain boundary,and improve the corrosion resistance and mechanical properties of NdFeB magnets.When the content of Ho increases from 0 to 21.0 wt%,the weight loss of magnets decreases from 2.672 to 0.933 mg/cm^(2),and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa,respectively.展开更多
Rare earth passivation was conducted on Zn coated NdFeB magnets by chemical reaction to enhance the corrosion resistance performance.Morphologies,micro structures and compositions of different passivated coatings were...Rare earth passivation was conducted on Zn coated NdFeB magnets by chemical reaction to enhance the corrosion resistance performance.Morphologies,micro structures and compositions of different passivated coatings were studied by X-ray diffraction,field emission scanning electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion behavior was evaluated by electrochemical measurement and neutral salt spray test.The results show that the rare earth passivation can enhance the corrosion resistance of Zn coated NdFeB magnets.When the concentration of cerium nitrate is 5 g/L,the passivated specimens can achieve the longest NSS time of 360 h,which is 144 h longer than that of the pristine Zn/NdFeB magnets.The passivation layer on the Zn coating surface contributes to the enhancement of the magnets’corrosion resistance.展开更多
文摘Decomposing growth rate of total factor productivity(TFP)into internal growth effect and the effect of factor reallocation formed by the flow of capital,labor and energy between sectors,we took 23 subsectors as the research object and adopted the multi-sector growth accounting framework(MSGAF)to verify the‘structural bonus hypothesis’from 2005 to 2017.The study drew the following conclusions:First,internal growth effect represented by sectoral technology progress was still the main contributor to TFP growth of the overall economy,but the contribution rate had decreased.Second,the reallocation effect of capital changed from structural burden to structural bonus.Third,the reallocation effect of labor showed a trend of first rising and then falling,changing from structural bonus to structural burden.Forth,the effect of energy reallocation was gradually emerging,with a shift from structural burden to structural bonus.Based on these research results,we argue that more attention should be paid to the efficiency of factor reallocation in addition to the technology progress.The inefficiency of factor reallocation caused by imperfect market and asymmetric information would partially offset the effect of technology progress and hinder the high-quality economic development.In view of the reallocation of capital,labor and energy,we propose the following suggestions:For capital,macro-control and market mechanism should be comprehensively accounted for.Further,capital must be allocated per the principle of profit maximization to ensure that its elasticity and allocation efficiency will be improved.The reallocation of labor should not only be limited to the 3-sector level.More attention should be paid to the marginal output differences within the secondary sector.For energy,attention should be paid to the elasticity of energy output between sectors to avoid inefficient allocation.It is also necessary to accelerate the phase-out of industries with high energy consumption and high pollution,promote the development of low energy industries to encourage‘energy conservation and emission reduction’as well as‘green development’by increasing the effect of energy reallocation.
基金supported by the National Natural Science Foundation of China(Nos.22001084,21925104,and 92261204)Princess Nourah bint Abdulrahman University Researchers Supporting Project number(PNURSP2023R398)Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘Electrochemical production of hydrogen peroxide(H_(2)O_(2))via the two-electron(2e-)pathway of oxygen reduction reaction(ORR)supplies an auspicious alternative to the current industrial anthraquinone process.Nonetheless,it still lacks efficient electrocatalysts to achieve high ORR activity together with 2e-selectivity simultaneously.Herein,a boron-doped defective nanocarbon(B-DC)electrocatalyst is synthesized by using fullerene frameworks as the precursor and boric oxide as the boron source.The obtained B-DC materials have a hierarchical porous structure,befitting boron dopants,and abundant topological pentagon defects,exhibiting a high ORR onset potential of 0.78 V and a dominated 2e-selectivity(over 95%).Remarkably,when B-DC electrocatalyst is employed in a real device,it achieves a high H_(2)O_(2) yield rate(247 mg·L^(-1)·h^(-1)),quantitative Faraday efficiency(~100%),and ultrafast organic pollutant degradation rate.The theoretical calculation reveals that the synergistic effect of topological pentagon defects and the incorporation of boron dopants promote the activation of the O_(2) molecule and facilitates the desorption of oxygen intermediate.This finding will be very helpful for the comprehension of the synergistic effect of topological defects and heteroatom dopants for boosting the electrocatalytic performance of nanocarbon toward H_(2)O_(2) production.
基金supported by Hefei Municipal Natural Science Foundation(2021026)the Key Research and Development Project of Anhui Province(202004a05020048,202004a05020051)the Fundamental Research Funds for the Central Universities(PA2020GDJQ0026)。
文摘Si alloying in the surface layer of NdFeB magnets was realized by thermal diffusion combined with magnetron sputtering.The surface composition,phase structure and morphology of NdFeB(S-Si)specimens were characterized by an X-ray diffractometer,an X-ray photoelectron spectrometer and a field emission scanning electron microscope,respectively.The corrosion resistance of bare NdFeB(S-Si)was analyzed by static full immersion corrosion test and electrochemical experiments.Effects of sputtering and thermal diffusion on the microstructure and corrosion resistance of the surface layer were studied.Results show that surface alloying layer can effectively improve the corrosion resistance of bare NdFeB with the optimized static total immersion corrosion test time in NdFeB(1S-Si)-800 of 36 h,which is much longer than that of the pristine NdFeB(less than 0.5 h).The E_(corr)of NdFeB(1S-Si)-800 positively shifts from-1.05 to-0.92 V,indicating that the corrosion tendency is obviously lower.The J_(corr)is1.45×10^(-6)A/cm^(2)which is 2 orders of magnitude lower than that of the pristine NdFeB(5.25×10^(-4)A/cm^(2)).The intergranular composite oxides existing in Nd-rich phase contribute to the enhancement of corrosion resistance of Si-surface-alloying NdFeB.
基金Project supported by the China Postdoctoral Science Foundation(2017M612065)Natural Science Foundation of Anhui Province(1408085MKL73,1408085MKL72)+1 种基金Anhui Key Research and Development Plan(1704a0902020)Fundamental Research Funds for the Central Universities(2016bh2x0004)
文摘The CeO2/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized by a scanning electron microscope and an X-ray diffractometer. The micro hardness of the composite coating was evaluated by a microhardness tester. The corrosive behaviors of the coatings were studied by potentiodynamic polarization curve, electrochemical impedance spectroscopy and neutral salt spray tests. The concentration of CeO2 nanoparticles(NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO2 NPs can enhance the microhardness of the composite coatings. Moreover, the nanoparticles disperse uniformly in the matrix when the concentration is lower than 30 g/L. The microhardness of CeO2/epoxy resin(30 g/L) composite coating is about 63% higher than that of the blank epoxy resin coating. And the NSS time of the CeO2/epoxy resin(30 g/L) composite coated sample can reach 1248 h.Meanwhile, the composite coatings possess no deteriorate influence on the magnetic properties of NdFeB substrates. The anticorrosion mechanisms of the composite coatings on the NdFeB substrate are deeply discussed.
基金Project supported by Fundamental Research Funds for the Central Universities(JZ2019YYPY0291)。
文摘Al coated NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the corro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a scanning electron microscope.Corrosion behaviors of the samples with different bias voltages were studied by electrochemical methods and neutral salt spray test,respectively.The bias voltage during the deposition process was optimized according to the coating structures and corrosion resistances.The density and flatness of Al coating increase with increasing the bias voltage,and at the same time the thickness decreases.The coating density and thickness turn to be stable when bias voltage is 1800 V.Also,the corrosion behaviors of PA-PVD Al coatings in different media,such as NaOH,HNO_(3) and NaCl solutions,were studied.The self-corrosion potentials(E_(corr)) of PA-PVD Al coatings almost keep constant in NaOH and HNO_(3) solutions with diffe rent concentrations.However,the self-corrosion current densities(J_(corr)) decrease with the increasing concentrations.E_(corr) shifts to negative potential and J_(corr)decreases gradually when increasing the concentration of NaCl solution.The corrosion mechanisms of Al coatings are discussed based on the corrosion behaviors in different media.
基金supported by the Base of the Key Technologies R & D Program of Anhui Province (1704c0402195)the Fundamental Research Funds for the Central Universities (PA2019GDPK0043,JZ2019HGBZ0142,JZ2019YYPY0291)。
文摘Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm^(2) and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.
基金supported by the National Natural Science Foundation of China (91023030,51072044,51102071,51172059,and 51272063)the International Scientific and Technological Cooperation Project of Anhui Province (10080703017)
文摘A novel glucose biosensor based on graphene nanosheets(GNs)modified gold nanowire arrays(AuNWAs)electrode was constructed.Highly ordered gold nanowire arrays were prepared by direct electrodeposition in anodic aluminum oxide templates.GNs were synthesized through a public route involving graphite oxidation,exfoliation,and chemical reduction.Field emission scanning electron microscope and high-resolution transmission electron microscope were employed to characterize the asprepared AuNWAs and GNs.Glucose oxidase was immobilized on the surface of GNs-AuNWAs modified electrode via a cross-linking method.The cyclic voltammetry results showed that the GNs-AuNWAs-based glucose biosensors have high catalysis activity to hydrogen peroxide(H2O2)than those modified with GNs or AuNWAs only.Furthermore,amperometric response was employed to detect glucose concentration owing to its simplicity,high selectivity,and relative low cost.Glucose biosensors based on GNs-AuNWAs showed excellent performance with high sensitivity of 40.25 lA cm-2(mmol/L)-1,low detection limit of 0.02 mmol/L,and a linear range from 0.02 to 3 mmol/L.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No. XDB20000000)CAS (No. QYZDY-SSW-SLH029)+2 种基金National Natural Science Foundation of China (Nos. 21725205, 21432007, 21572246)STCSM18520712200K.C. Wong Education Foundation
文摘A ligand-free nickel-catalyzed Kumada cross-coupling of aryl bromides and tert-butyl Grignard reagents led to the formation of a series of tert-butyl aryls in moderate to good yields, excellent tBu/iBu ratios, and good functional group compatibility. A radical coupling process is indicated and a mechanism with a Ni(Ⅰ)-Ni(Ⅲ) catalytic cycle is proposed.
基金Project supported by Anhui Major Science and Technology Projects (17030901063,18030901098)the Key of BGRIMM Technology Group Co.Ltd.(20190898000002)Anhui Key Research and Development Plan(1804a09020068)。
文摘(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester,an electrochemical workstation,a microhardness tester,a bending tester,a scanning electron microscope and an X-ray diffractometer.Results show that the addition of Ho can change the main phase structure,optimize the distribution of rare-earth rich(RE-rich) phases in grain boundary,and improve the corrosion resistance and mechanical properties of NdFeB magnets.When the content of Ho increases from 0 to 21.0 wt%,the weight loss of magnets decreases from 2.672 to 0.933 mg/cm^(2),and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa,respectively.
基金Project supported by the Key Research and Development Project of Anhui Province(202004a05020048,202004a05020051)the Fundamental Research Funds for the Cornell University(JZ2019HGBZ0142,PA2019GDPK0043,JZ2019YYPY0291,PA2020GDJQ0026)。
文摘Rare earth passivation was conducted on Zn coated NdFeB magnets by chemical reaction to enhance the corrosion resistance performance.Morphologies,micro structures and compositions of different passivated coatings were studied by X-ray diffraction,field emission scanning electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion behavior was evaluated by electrochemical measurement and neutral salt spray test.The results show that the rare earth passivation can enhance the corrosion resistance of Zn coated NdFeB magnets.When the concentration of cerium nitrate is 5 g/L,the passivated specimens can achieve the longest NSS time of 360 h,which is 144 h longer than that of the pristine Zn/NdFeB magnets.The passivation layer on the Zn coating surface contributes to the enhancement of the magnets’corrosion resistance.