We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond f...We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond fission is the dominant fragmentation pathway at these wavelengths,yielding SD fragments in both the ground(X)and excited(A)electronic states.Most S(^(1)D)atoms arising via 21A′21A′the rival S atom elimination channel when exciting at~139.1 nm are formed with D_(2)partners,in a wide range of rovibrational levels.The partially resolved structure in the total translational energy distributions,P(ET),derived from the S(^(1)D)atom images,implies two dynamical routes into S(^(1)D)+D_(2)products following non-adiabatic coupling from the photo-excited Rydberg state to the dissociative potential energy surface(PES).Similar D_(2)products are evident in the P(ET)spectra derived from analysis of S(^(1)D)images from D_(2)S photolysis at~129.1 nm,but their contribution is overshadowed by a feature attributable to three-body dissociation to S(^(1)D)+2D fragments.These atomic products are deemed to arise via a natural extension of the dynamics responsible for the previously observed highly rotationally excited SD(A)fragments arising via the rival S–D bond fission pathway:asymmetric bond extension together with a dramatic opening of the interbond angle driven by torques generated after coupling to the highly anisotropic 2^(1)A′PES,leading to a centripetally-driven break-up.展开更多
An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-...An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, field-emission scanning electron microscopy（SEM）, and Brunauer-Emmett-Teller analysis（BET） techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C-H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold（1201 m2/g for activated PG/C vs. 106 m2/g for PG/C） after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.展开更多
A 0.66 mm-diameter AZ31 alloy wire with ultimate tensile strength of 400 MPa and elongation of 28.5%was successfully prepared via the combination of cold-drawing and electropulsing treatment processing(EPT).Microstruc...A 0.66 mm-diameter AZ31 alloy wire with ultimate tensile strength of 400 MPa and elongation of 28.5%was successfully prepared via the combination of cold-drawing and electropulsing treatment processing(EPT).Microstructure observation showed that the grain size of EPTed samples was refined to about 1μm and the basal texture strength with maxima texture index was weakened to 7.18.EPT can significantly accelerate recrystallization by enhancing the mobility of dislocation and atomic diffusion due to the coupling of the thermal and athermal effects.Finally,uniform ultrafine-grained structure was obtained in the EPTed samples by static recrystallization completed in a very short time(30 s)at relatively low temperature(433 K).展开更多
The CeO_(2)/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 characteriz...The CeO_(2)/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 CeO_(2) nanoparticles(NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO_(2) 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 CeO_(2)/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 CeO_(2)/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
This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging(MSHF) and subsequent spheroid...This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging(MSHF) and subsequent spheroidizing annealing(MSHFA). To this end, the present study mainly employed stereo microscopy, Optical Metallurgical Microscopy(OMM), Scanning Electron Microscopy(SEM), and Electron Backscatter Diffraction(EBSD) to characterize and analyze the workpiece at each processing stage of MSHF while performing microhardness measurement and uniaxial tensile experiment to test and analyze the mechanical properties of the workpiece. Macro-structure observation showed that the simulation results of flow lines at each stage were consistent with the experimental results. Microscopic observation showed that, after MSHF, deformation gradually became less significant along the outward radial direction of the bearing ring. After MSHFA,the microstructures of the bearing ring became uniform, whereas primary carbides did not dissolve.The mechanical properties were better in the axial direction(AD) than in the radial(RD) and circumferential directions(CD) after MSHF due to the smaller grain width. After MSHFA, the mechanical properties in the ADs and CDs were better than those in the RDs, which was due to the large cross-sectional area of carbides along the flow-line direction.展开更多
The effect of particle deformation zone(PDZ) on the microstructure and mechanical properties of SiC_(p)/Mg-5Zn composites was studied.Meanwhile,the work hardening and so ftening behavior of SiC_(p)/Mg-5Zn composites i...The effect of particle deformation zone(PDZ) on the microstructure and mechanical properties of SiC_(p)/Mg-5Zn composites was studied.Meanwhile,the work hardening and so ftening behavior of SiC_(p)/Mg-5Zn composites influenced by PDZ size were analyzed and discussed using neutron diffraction under in-situ tensile deformation.The evolution of FWHM(full width at half maximum) extracted from the diffraction pattern of SiC_(p)/Mg-5Zn composites was used to interpret the modification of dislocation density during in-situ tension,which discovered the effect of dislocation on the work hardening behavior of SiC_(p)/Mg-5Zn composites.In addition,the tensile stress reduction(△P_i) values during in-situ tension test were calculated to analyze the effect of PDZ size on the softening behavior of SiC_(p)/Mg-5Zn composites.The results show that the work hardening rate of SiC_(p)/Mg-5Zn composites increased with the enlargement of PDZ size,which was attributed to the grain size of SiC_(p)/Mg-5Zn composites increased with the enlargement of PDZ size.Moreover,the stress reduction(△P_i) values increased continuously during in-situ tensile for SiC_(p)/Mg-5Zn composites due to the increased stored energy produced during plastic deformation,which provided a driving force for the softening effect.However,the effect of grain size on the softening behavior is greater than that of the stored energy,which led to the tensile stress reduction(△P_i) values of P30(d_(PDZ)=30 μm)-SiC_(p)/Mg-5Zn composite were higher than that of P60(d_(PDZ)=60 μm)-SiC_(p)/Mg-5Zn composite when the ε_(ri) were 0.25,0.5,0.75 and 1,respectively.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
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
AZ61 Mg alloy with homogeneous refined microstructure and exceptional mechanical properties was obtained by the combined technology of equal-channel angular pressing(ECAP)and electropulsing treatment(EPT)in this paper...AZ61 Mg alloy with homogeneous refined microstructure and exceptional mechanical properties was obtained by the combined technology of equal-channel angular pressing(ECAP)and electropulsing treatment(EPT)in this paper.Based on an ECAP die with an intersection angle of 160,the lower temperature is particularly adapted for AZ61 alloy to be deformed,in which accompanied by high accumulated defects density.The recrystallization of EPTed samples during different stages indicated that the recrystallization behavior of the deformed Mg alloy was mainly affected by the processing time and duration of EPT.Compared to those of the as-received samples,the average grain size of the EPTed samples was refined from 89μm to 1.0μm,accordingly the yields stress(YS)and ultimate tensile strength(UTS)were increased from 100 MPa and 260 MPa to 330 MPa and 448 MPa,respectively.The mechanisms of microstructure transformation and the reinforced mechanical properties were analyzed based on the strain of single ECAP,cumulative storage energy and the athermal effect of EPT.展开更多
Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after ext...Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles. As a result, it leads to a severe capacity fading and an increase in internal impedance. Herein, Ti-elemental MXene was employed as a matrix for the intermediate product of Si electrodes. The boundary between the inner core of pristine Si and its outer shell of amorphous Li x Si alloy was reconstructed. Smaller amorphous aggregates were observed in the MXene&Si hybrid electrode after 500 cycles by using transmission electron microscopy. Consequently, an enhanced specific capacity was achieved as MXene as a matrix enables loading amorphous Si.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
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
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
N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates fro...N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),respectively.As the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.展开更多
Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important r...Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.展开更多
Aluminum nitride （AIN） nanowires, serrated nanoribbons, and nanoribbons were selectively obtained through a simple chloride assisted chemical vapor deposition process. The morphologies of the products could be contr...Aluminum nitride （AIN） nanowires, serrated nanoribbons, and nanoribbons were selectively obtained through a simple chloride assisted chemical vapor deposition process. The morphologies of the products could be controlled by adjusting the deposition position and the flux of the reactant gas. The morphologies and structures of the AIN products were investigated in detail. The formation mechanism of the as-prepared different morphologies of AIN one-dimensional （ID） nanostructures was discussed on the basis of the experimental results.展开更多
As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted ele...As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted electrodeposition is used to improve the surface quality and properties of Zn–Ni–Mo coatings,with investigation of how laser energy in the range of 0–21.1μJ affects their element content,surface morphology,crystal phase,microhardness,residual internal stress,and corrosion resistance.The laser irradiation accelerates the electrodeposition,refines the grain size,improves the hydrogen adsorption,and reduces the residual tensile stress,and a laser energy of 15.4μJ gives the highest Ni and Mo contents and the lowest Zn content,as well as the optimum surface morphology,microhardness,residual internal stress,and corrosion resistance of the coating.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22241304,22225303,22403091,22173100)the Major Program of the National Natural Science Foundation of China(Nos.42494850 and 42494853)+5 种基金the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics(No.22288201))the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB0970000 and XDB0970200)the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)the Liaoning Revitalization Talents Program(No.XLYC2402046)the Shenzhen Science and Technology Program(No.ZDSYS20200421111001787)Zhenxing Li thanks the Guangdong Science and Technology Program(No.2025A1515012671)。
文摘We report high-resolution velocity map imaging studies of S(^(1)D)atoms formed following excitation on two intense absorption bands of gas phase D_(2)S molecules,centred at wave-lengths~139.1 and~129.1 nm.DS–D bond fission is the dominant fragmentation pathway at these wavelengths,yielding SD fragments in both the ground(X)and excited(A)electronic states.Most S(^(1)D)atoms arising via 21A′21A′the rival S atom elimination channel when exciting at~139.1 nm are formed with D_(2)partners,in a wide range of rovibrational levels.The partially resolved structure in the total translational energy distributions,P(ET),derived from the S(^(1)D)atom images,implies two dynamical routes into S(^(1)D)+D_(2)products following non-adiabatic coupling from the photo-excited Rydberg state to the dissociative potential energy surface(PES).Similar D_(2)products are evident in the P(ET)spectra derived from analysis of S(^(1)D)images from D_(2)S photolysis at~129.1 nm,but their contribution is overshadowed by a feature attributable to three-body dissociation to S(^(1)D)+2D fragments.These atomic products are deemed to arise via a natural extension of the dynamics responsible for the previously observed highly rotationally excited SD(A)fragments arising via the rival S–D bond fission pathway:asymmetric bond extension together with a dramatic opening of the interbond angle driven by torques generated after coupling to the highly anisotropic 2^(1)A′PES,leading to a centripetally-driven break-up.
基金financially supported by the National Natural Science Foundation of China (No. 51002042, No. 40902020 and No. 51072044)the Fundamental Research Funds for the Central Universities (No. 2013HGQC0015)+1 种基金Scientific Research Foundation for the Returned Scholars from Ministry of Education of China (No. 2013JYLH0774)Project from Ministry of Science and Technology of Anhui Province (No. J2014AKKJ0002)
文摘An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, field-emission scanning electron microscopy（SEM）, and Brunauer-Emmett-Teller analysis（BET） techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C-H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold（1201 m2/g for activated PG/C vs. 106 m2/g for PG/C） after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.
基金supported financially by the National Natural Science Foundation of China(Nos.U1710118,U1810122,51504162 and 51601123)the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(2018)+1 种基金the Natural Science Foundation of Shanxi Province(No.201801D221139)the Research Project Supported by Shanxi Scholarship Council of China(No.2016-029)。
文摘A 0.66 mm-diameter AZ31 alloy wire with ultimate tensile strength of 400 MPa and elongation of 28.5%was successfully prepared via the combination of cold-drawing and electropulsing treatment processing(EPT).Microstructure observation showed that the grain size of EPTed samples was refined to about 1μm and the basal texture strength with maxima texture index was weakened to 7.18.EPT can significantly accelerate recrystallization by enhancing the mobility of dislocation and atomic diffusion due to the coupling of the thermal and athermal effects.Finally,uniform ultrafine-grained structure was obtained in the EPTed samples by static recrystallization completed in a very short time(30 s)at relatively low temperature(433 K).
基金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 CeO_(2)/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 CeO_(2) nanoparticles(NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO_(2) 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 CeO_(2)/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 CeO_(2)/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the financial support from the National Natural Science Foundation of China (No. 51974099)。
文摘This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging(MSHF) and subsequent spheroidizing annealing(MSHFA). To this end, the present study mainly employed stereo microscopy, Optical Metallurgical Microscopy(OMM), Scanning Electron Microscopy(SEM), and Electron Backscatter Diffraction(EBSD) to characterize and analyze the workpiece at each processing stage of MSHF while performing microhardness measurement and uniaxial tensile experiment to test and analyze the mechanical properties of the workpiece. Macro-structure observation showed that the simulation results of flow lines at each stage were consistent with the experimental results. Microscopic observation showed that, after MSHF, deformation gradually became less significant along the outward radial direction of the bearing ring. After MSHFA,the microstructures of the bearing ring became uniform, whereas primary carbides did not dissolve.The mechanical properties were better in the axial direction(AD) than in the radial(RD) and circumferential directions(CD) after MSHF due to the smaller grain width. After MSHFA, the mechanical properties in the ADs and CDs were better than those in the RDs, which was due to the large cross-sectional area of carbides along the flow-line direction.
基金supported financially by the National Natural Science Foundation of China(Nos.51771128 and 51771129)the Shanxi Province Science and Technology Major Projects(No.20181101008)the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi。
文摘The effect of particle deformation zone(PDZ) on the microstructure and mechanical properties of SiC_(p)/Mg-5Zn composites was studied.Meanwhile,the work hardening and so ftening behavior of SiC_(p)/Mg-5Zn composites influenced by PDZ size were analyzed and discussed using neutron diffraction under in-situ tensile deformation.The evolution of FWHM(full width at half maximum) extracted from the diffraction pattern of SiC_(p)/Mg-5Zn composites was used to interpret the modification of dislocation density during in-situ tension,which discovered the effect of dislocation on the work hardening behavior of SiC_(p)/Mg-5Zn composites.In addition,the tensile stress reduction(△P_i) values during in-situ tension test were calculated to analyze the effect of PDZ size on the softening behavior of SiC_(p)/Mg-5Zn composites.The results show that the work hardening rate of SiC_(p)/Mg-5Zn composites increased with the enlargement of PDZ size,which was attributed to the grain size of SiC_(p)/Mg-5Zn composites increased with the enlargement of PDZ size.Moreover,the stress reduction(△P_i) values increased continuously during in-situ tensile for SiC_(p)/Mg-5Zn composites due to the increased stored energy produced during plastic deformation,which provided a driving force for the softening effect.However,the effect of grain size on the softening behavior is greater than that of the stored energy,which led to the tensile stress reduction(△P_i) values of P30(d_(PDZ)=30 μm)-SiC_(p)/Mg-5Zn composite were higher than that of P60(d_(PDZ)=60 μm)-SiC_(p)/Mg-5Zn composite when the ε_(ri) were 0.25,0.5,0.75 and 1,respectively.
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.
基金supported in part by National Natural Science Foundation of China(U1710118,U1810122,51504162 and 51601123)Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(2018)+1 种基金the Natural Science Foundation of Shanxi Province(201801D221139)Research Project Supported by Shanxi Scholarship Council of China(2016029)
文摘AZ61 Mg alloy with homogeneous refined microstructure and exceptional mechanical properties was obtained by the combined technology of equal-channel angular pressing(ECAP)and electropulsing treatment(EPT)in this paper.Based on an ECAP die with an intersection angle of 160,the lower temperature is particularly adapted for AZ61 alloy to be deformed,in which accompanied by high accumulated defects density.The recrystallization of EPTed samples during different stages indicated that the recrystallization behavior of the deformed Mg alloy was mainly affected by the processing time and duration of EPT.Compared to those of the as-received samples,the average grain size of the EPTed samples was refined from 89μm to 1.0μm,accordingly the yields stress(YS)and ultimate tensile strength(UTS)were increased from 100 MPa and 260 MPa to 330 MPa and 448 MPa,respectively.The mechanisms of microstructure transformation and the reinforced mechanical properties were analyzed based on the strain of single ECAP,cumulative storage energy and the athermal effect of EPT.
基金financial support provided by the Joint Foundation of Liaoning Province National Science FoundationShenyang National Laboratory for Materials Science (Grant No. 20180510047)+6 种基金the National Natural Science Foundation of China (Grant Nos. 91545119 , 21761132025 , 21773269 and 51872115)the Youth Innovation Promotion Association CAS (Grant No. 2015152)the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT, 2017TD-09)“Double-First Class” Discipline for Materials Science & EngineeringNatural Science Foundation of Anhui Province (1608085ME93)the Fundamental Research Funds for the Central Universities (JZ2018YYPY0305)the 111 Project “New Materials and Technology for Clean Energy” (B18018)
文摘Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles. As a result, it leads to a severe capacity fading and an increase in internal impedance. Herein, Ti-elemental MXene was employed as a matrix for the intermediate product of Si electrodes. The boundary between the inner core of pristine Si and its outer shell of amorphous Li x Si alloy was reconstructed. Smaller amorphous aggregates were observed in the MXene&Si hybrid electrode after 500 cycles by using transmission electron microscopy. Consequently, an enhanced specific capacity was achieved as MXene as a matrix enables loading amorphous Si.
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 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The experimental work is supported by the National Natural Science Foundation of China(No.22241304,No.22225303)the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics,No.22288201)+3 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.GJJSTD20220001)the Innovation Program for Quantum Science and Technology(No.2021ZD0303304)Xueming Yang also thanks the Guangdong Science and Technology Program(No.2019ZT08L455 and No.2019JC01X091)the Shenzhen Science and Technology Program(No.ZDSYS20200421111001787).
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financially supported by the National Natural Science Foundation of China (Nos. 51572124 and 51702162)the Natural Science Foundation of Jiangsu Province (No. BK20180154and BK20180490)+1 种基金the Fundamental Research Funds for the Central Universities (No. 30920130111003)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, China)。
文摘N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),respectively.As the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.
基金partially financially supported by NSF CBET-2033343.J.Z.thanks the support from National Natural Science Foundation of China(52172293,51772072,and 51672065)the Fundamental Research Funds for the Central Universities(JZ2021HGQB0282 and PA2021GDSK0088)+3 种基金financial support from the Key R&D Projects of Anhui Province(202104b11020016)the 111 Project(B18018)the National Synchrotron Light Source II,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No.DE-SC0012704the use of facilities within the Eyring Materials Center at Arizona State University supported in part by NNCI-ECCS-1542160.
文摘Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.
基金the National Natural Science Foundation of China under grant Nos.10674138 and 20571022.
文摘Aluminum nitride （AIN） nanowires, serrated nanoribbons, and nanoribbons were selectively obtained through a simple chloride assisted chemical vapor deposition process. The morphologies of the products could be controlled by adjusting the deposition position and the flux of the reactant gas. The morphologies and structures of the AIN products were investigated in detail. The formation mechanism of the as-prepared different morphologies of AIN one-dimensional （ID） nanostructures was discussed on the basis of the experimental results.
基金supported by the National Natural Science Foundation of China(Grant Nos.51905226,52075227,and 52105449)the Natural Science Foundation of Jiangsu Province(Grant No.BK20210755)the Postdoctoral Foundation of Jiangsu Province(Grant No.2021K264B).
文摘As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted electrodeposition is used to improve the surface quality and properties of Zn–Ni–Mo coatings,with investigation of how laser energy in the range of 0–21.1μJ affects their element content,surface morphology,crystal phase,microhardness,residual internal stress,and corrosion resistance.The laser irradiation accelerates the electrodeposition,refines the grain size,improves the hydrogen adsorption,and reduces the residual tensile stress,and a laser energy of 15.4μJ gives the highest Ni and Mo contents and the lowest Zn content,as well as the optimum surface morphology,microhardness,residual internal stress,and corrosion resistance of the coating.
