Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radi...Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function（RDF）. The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function（DRDF）. The calculation of the geometric model shows that octahedrally six-coordinated Mg（H2O）62＋, with an Mg2＋…OW bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair（CIP） in the more concentrated solution（1：18, H2O/salt molar ratio） with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42– ion happens in the solution. The S…OW bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.展开更多
Propellant ionization in the Hall thruster discharge channel is a significant process and has strong influence on the thruster＇s efficiency. In this work, the functional relation has been established between the ioni...Propellant ionization in the Hall thruster discharge channel is a significant process and has strong influence on the thruster＇s efficiency. In this work, the functional relation has been established between the ionization density distribution and the function of the ion energy distribution through the basic equations governing the ion flow in the Hall thruster channel and the method achieved for reconstructing the ionization density distribution inside the channel by ordinary plasma diagnosis of the potential distribution and ion energy spectrum of the plasma jet. The ionization density distributions of single and double charged ions in an ATON-thruster channel have been reconstructed according to the experimental data of the potential distribution along the axis of the channel and the ion energy spectrum of the plasma jet. The agreement between the calculation and experimental results of the percentage of double charged ions proves the validity of our method achieved in this work.展开更多
The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the t...The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the third generation synchrotron facility and spallation neutron source worldwide, the PDF method has developed quickly both experimentally and theoretically in recent years. Recently this method was successfully implemented at the Shanghai Synchrotron Radiation Facility（SSRF）. The data quality is very high and this ensures the applicability of the method to study the subtle structural changes in complex materials. In this article, we introduce in detail this new method and show some experimental data we collected.展开更多
The increased use of rechargeable batteries in portable electronic devices and the continuous develop-ment of novel applications （e.g. transportation and large scale energy storage）, have raised a strong de-mand for...The increased use of rechargeable batteries in portable electronic devices and the continuous develop-ment of novel applications （e.g. transportation and large scale energy storage）, have raised a strong de-mand for high performance batteries with increased energy density, cycle and calendar life, safety andlower costs. This triggers significant efforts to reveal the fundamental mechanism determining batteryperformance with the use of advanced analytical techniques. However, the inherently complex character-istics of battery systems make the mechanism analysis sophisticated and difficult. Synchrotron radiationis an advanced collimated light source with high intensity and tunable energies. It has particular ad-vantages in electronic structure and geometric structure （both the short-range and long-range structure）analysis of materials on different length and time scales. In the past decades, synchrotron X-ray tech-niques have been widely used to understand the fundamental mechanism and guide the technologicaloptimization of batteries. In particular, in situ and operando techniques with high spatial and temporalresolution, enable the nondestructive, real time dynamic investigation of the electrochemical reaction,and lead to significant deep insights into the battery operation mechanism. This review gives a brief introduction of the application of synchrotron X-ray techniques to the inves-tigation of battery systems. The five widely implicated techniques, including X-ray diffraction （XRD）, PairDistribution Function （PDF）, Hard and Soft X-ray absorption spectroscopy （XAS） and X-ray photoelectronspectroscopy （XPS） will be reviewed, with the emphasis on their in situ studies of battery systems during cycling.展开更多
Electron diffraction was used to study the local atomic structure of Cu49Hf42Al9 metallic glasses (MGs). The amorphous nature of the MG was fully retained after the compression test. The partial radial distribution fu...Electron diffraction was used to study the local atomic structure of Cu49Hf42Al9 metallic glasses (MGs). The amorphous nature of the MG was fully retained after the compression test. The partial radial distribution functions (PRDFs) of the MG structure obtained from the atomic model using reverse Monte Carlo and density functional theory optimization display that the peaks of the first nearest-neighbour distances for Cu-Cu, Hf-Cu and Hf-Hf atomic pairs were located at 2.56 A, 2.78 A and 3.23 A, respectively. The wide distribution of PRDF for Hf-Hf atomic pair explained the high plasticity of the material.展开更多
Zr-based Zr_50Pd_40Al_10 metallic glasses has not only crystalline phases of about 5 nm in diameter but also amorphous phases. In this work, the radial distribution functions(RDFs) of amorphous structure of Zr_50Pd_40...Zr-based Zr_50Pd_40Al_10 metallic glasses has not only crystalline phases of about 5 nm in diameter but also amorphous phases. In this work, the radial distribution functions(RDFs) of amorphous structure of Zr_50Pd_40Al_10 metallic glasses were firstly measured by electron diffraction, and then Reverse Monte Carlo(RMC) optimization accompanied by density functional theory(DFT) calculations. The amorphous structure has not only short-range order but also good medium-range order. In the RDFs of its amorphous structure, the first and the second peaks are located at 2.96 ? and 4.79 ?, respectively. Partial radical distribution functions(PRDFs) show that the contributions of the first and the second nearest-neighbor distances of various atom pairs to the G(r) peak values, and the first nearest-neighbor distances of Pd–Zr and Zr–Zr atom pairs are the sources of main G(r) peak values between 2? and 6?. The competition mechanism for generating the Pd_25Zr_55 Al_20 amorphous phase and the intermetallic crystalline phase Pd_11Zr_9 is associated with the differences of atomic radius, the proportion, and the melting point of different atoms, as well as the heat of mixing between atoms, leading to an equilibrium state of the two phases. Accordingly, a composite system with intertwined nanocrystals and amorphous phases is in turn formed, and improves the stability of the material.展开更多
The energy materials performance is intrinsically determined by structures from the average lattice structure to the atom arrangement, valence, and distribution of the containing transition metal(TM) elements. Underst...The energy materials performance is intrinsically determined by structures from the average lattice structure to the atom arrangement, valence, and distribution of the containing transition metal(TM) elements. Understanding the mechanism of the structure transition and atom rearrangement via synthesis or processing is key to expediting the exploration of excellent energy materials. In this work, in situ neutron scattering is employed to reveal the real-time structure evolution, including the TM-O bonds, lattice,TM valence and the migration of the high-voltage spinel cathode LiNi_(0.5)Mn_(1.5)O_(4). The transition-metalmediated spinel destabilization under the annealing at the oxygen-deficient atmosphere is pinpointed.The formation of Mn^(3+) is correlated to the TM migration activation, TM disordered rearrangement in the spinel, and the transition to a layered-rocksalt phase. The further TM interdiffusion and Mn^(3+) reduction are also revealed with multi-stage thermodynamics and kinetics. The mechanisms of phase transition and atom migrations as functions of temperature, time and atmosphere present important guidance on the synthesis in various-valence element containing oxides.展开更多
Bi-Sb alloys are appealing anode materials for potassium ion batteries(PIBs)but challenged by their enormous volumetric variation during operation.Herein,a facile one-step dealloying protocol was devised and utilized ...Bi-Sb alloys are appealing anode materials for potassium ion batteries(PIBs)but challenged by their enormous volumetric variation during operation.Herein,a facile one-step dealloying protocol was devised and utilized to prepare the Bi-Sb alloys that manifest an exotic bicontinuous hierarchical nanoporous(np)microstructure ideal for volume-change mitigation and K+transport percolation.The growth mechanism fostering the peculiar morphology of the np-(Bi,Sb)alloys was investigated and clarified via operando X-ray(XRD)and ex-situ scanning electron microscopy(SEM).In particular,the np-Bi6Sb2 electrode,optimized for comprehensive electrochemical performance,achieves decent reversible capacities and a superior lifespan,as benchmarked with the monometallic references and other Bi-Sb alloy electrodes.The(de)potassiation mechanism of the np-(Bi,Sb)alloys was studied by operando XRD and further rationalized by density functional theory(DFT)calculations,whereby a homogeneous(segregation-free)and robust two-step electrochemically-driven phase transformations’catenation of(Bi,Sb)↔K(Bi,Sb)2↔K3(Bi,Sb)was reliably established to substantiate the outstanding reversibility of the np-(Bi,Sb)anodes in PIBs.展开更多
Chemical preparation, X-ray single crystal diffraction, thermal analysis, electrochemical measurements, IR, Raman and UV spectroscopic investigations of a novel organic-inorganic hybrid material（CaH7N2）CdCl3（H2O）...Chemical preparation, X-ray single crystal diffraction, thermal analysis, electrochemical measurements, IR, Raman and UV spectroscopic investigations of a novel organic-inorganic hybrid material（CaH7N2）CdCl3（H2O）（1） were described. 1-Methylimidazolium aquapentachlorocadmate（II） crystallized in the monoclinic system with P2 1/n space group. Its structure provided a new interesting example of infinite inorganic layers of [CdCl3（H2O）]n n- centered by （-101） planes. The [CdCl5（H2O）]- anions were interconnected by O-H...Cl hydrogen bonds. Acidic protons of the chloride group were transferred to the organic molecule, giving the singly-protonated cations. The ability of ions to form a spontaneous three-dimensional structure through O-H…Cl and N-H…Cl hydrogen bonds was fully utilized. These hydrogen bonds induced notable vibrational effects. IR and Raman spectra were reported and discussed on the basis of group theoretical analysis and on quantum chemical density theory（DFT） calculation. The molecular HOMO-LUMO compositions and their respective energy gaps were also drawn to explain the activity of our compound. The role of the intermolecular interaction in this crystal was analyzed. The optical study was also investigated by UV-Vis absorption spectrum. Thermal analysis reveals the hydrous character of the compound. Cyclic voltammetry was studied to evaluate the spectral and structural changes accompanying electron transfer.展开更多
基金Supported by the Key Program of the National Natural Science Foundation of China(Nos.20836009 and 20873172)
文摘Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function（RDF）. The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function（DRDF）. The calculation of the geometric model shows that octahedrally six-coordinated Mg（H2O）62＋, with an Mg2＋…OW bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair（CIP） in the more concentrated solution（1：18, H2O/salt molar ratio） with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42– ion happens in the solution. The S…OW bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.
文摘Propellant ionization in the Hall thruster discharge channel is a significant process and has strong influence on the thruster＇s efficiency. In this work, the functional relation has been established between the ionization density distribution and the function of the ion energy distribution through the basic equations governing the ion flow in the Hall thruster channel and the method achieved for reconstructing the ionization density distribution inside the channel by ordinary plasma diagnosis of the potential distribution and ion energy spectrum of the plasma jet. The ionization density distributions of single and double charged ions in an ATON-thruster channel have been reconstructed according to the experimental data of the potential distribution along the axis of the channel and the ion energy spectrum of the plasma jet. The agreement between the calculation and experimental results of the percentage of double charged ions proves the validity of our method achieved in this work.
基金Project supported by the National Natural Science Foundation of China(Grant No.U1232112)the National Key Basic Research Program of China(Grant No.2012CB825700)
文摘The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the third generation synchrotron facility and spallation neutron source worldwide, the PDF method has developed quickly both experimentally and theoretically in recent years. Recently this method was successfully implemented at the Shanghai Synchrotron Radiation Facility（SSRF）. The data quality is very high and this ensures the applicability of the method to study the subtle structural changes in complex materials. In this article, we introduce in detail this new method and show some experimental data we collected.
基金the National Natural Science Foundation of China (Grant nos.21233004,21303147 and 21473148,etc.)the National Key Research and Development Program (Grant no.2016YFB0901500)
文摘The increased use of rechargeable batteries in portable electronic devices and the continuous develop-ment of novel applications （e.g. transportation and large scale energy storage）, have raised a strong de-mand for high performance batteries with increased energy density, cycle and calendar life, safety andlower costs. This triggers significant efforts to reveal the fundamental mechanism determining batteryperformance with the use of advanced analytical techniques. However, the inherently complex character-istics of battery systems make the mechanism analysis sophisticated and difficult. Synchrotron radiationis an advanced collimated light source with high intensity and tunable energies. It has particular ad-vantages in electronic structure and geometric structure （both the short-range and long-range structure）analysis of materials on different length and time scales. In the past decades, synchrotron X-ray tech-niques have been widely used to understand the fundamental mechanism and guide the technologicaloptimization of batteries. In particular, in situ and operando techniques with high spatial and temporalresolution, enable the nondestructive, real time dynamic investigation of the electrochemical reaction,and lead to significant deep insights into the battery operation mechanism. This review gives a brief introduction of the application of synchrotron X-ray techniques to the inves-tigation of battery systems. The five widely implicated techniques, including X-ray diffraction （XRD）, PairDistribution Function （PDF）, Hard and Soft X-ray absorption spectroscopy （XAS） and X-ray photoelectronspectroscopy （XPS） will be reviewed, with the emphasis on their in situ studies of battery systems during cycling.
基金supported by the National Science Fund for Excellent Young Scholars of China (No. 51422203)the National Natural Science Foundation of China (Nos. 51572091 and 51372001)+4 种基金the Natural Science Foundation of Guangdong Province, China (No. 2018A030313395)the China Postdoctoral Science Foundation(No. 2017M610522)the Science and Technology Program of Guangzhou, China (No. 201604046027)the Fundamental Research Funds for the Central Universities (No. 2017BQ035)the fund of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP201716)
文摘Electron diffraction was used to study the local atomic structure of Cu49Hf42Al9 metallic glasses (MGs). The amorphous nature of the MG was fully retained after the compression test. The partial radial distribution functions (PRDFs) of the MG structure obtained from the atomic model using reverse Monte Carlo and density functional theory optimization display that the peaks of the first nearest-neighbour distances for Cu-Cu, Hf-Cu and Hf-Hf atomic pairs were located at 2.56 A, 2.78 A and 3.23 A, respectively. The wide distribution of PRDF for Hf-Hf atomic pair explained the high plasticity of the material.
基金supported by National Science Fund for Excellent Young Scholars of China (No. 51422203)the National Natural Science Foundation of China (Nos. 51572091 and 51372001)+4 种基金the Natural Science Foundation of Guangdong Province, China (No. 2018A030313395)the China Postdoctoral Science Foundation (No. 2017M610522)the Science and Technology Program of Guangzhou, China (No. 201604046027)the Fundamental Research Funds for the Central Universities (No. 2017BQ035)the fund of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP201716)
文摘Zr-based Zr_50Pd_40Al_10 metallic glasses has not only crystalline phases of about 5 nm in diameter but also amorphous phases. In this work, the radial distribution functions(RDFs) of amorphous structure of Zr_50Pd_40Al_10 metallic glasses were firstly measured by electron diffraction, and then Reverse Monte Carlo(RMC) optimization accompanied by density functional theory(DFT) calculations. The amorphous structure has not only short-range order but also good medium-range order. In the RDFs of its amorphous structure, the first and the second peaks are located at 2.96 ? and 4.79 ?, respectively. Partial radical distribution functions(PRDFs) show that the contributions of the first and the second nearest-neighbor distances of various atom pairs to the G(r) peak values, and the first nearest-neighbor distances of Pd–Zr and Zr–Zr atom pairs are the sources of main G(r) peak values between 2? and 6?. The competition mechanism for generating the Pd_25Zr_55 Al_20 amorphous phase and the intermetallic crystalline phase Pd_11Zr_9 is associated with the differences of atomic radius, the proportion, and the melting point of different atoms, as well as the heat of mixing between atoms, leading to an equilibrium state of the two phases. Accordingly, a composite system with intertwined nanocrystals and amorphous phases is in turn formed, and improves the stability of the material.
基金supported by the Division of Materials Science and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (DOE)。
文摘The energy materials performance is intrinsically determined by structures from the average lattice structure to the atom arrangement, valence, and distribution of the containing transition metal(TM) elements. Understanding the mechanism of the structure transition and atom rearrangement via synthesis or processing is key to expediting the exploration of excellent energy materials. In this work, in situ neutron scattering is employed to reveal the real-time structure evolution, including the TM-O bonds, lattice,TM valence and the migration of the high-voltage spinel cathode LiNi_(0.5)Mn_(1.5)O_(4). The transition-metalmediated spinel destabilization under the annealing at the oxygen-deficient atmosphere is pinpointed.The formation of Mn^(3+) is correlated to the TM migration activation, TM disordered rearrangement in the spinel, and the transition to a layered-rocksalt phase. The further TM interdiffusion and Mn^(3+) reduction are also revealed with multi-stage thermodynamics and kinetics. The mechanisms of phase transition and atom migrations as functions of temperature, time and atmosphere present important guidance on the synthesis in various-valence element containing oxides.
基金The authors gratefully acknowledge financial support by National Natural Science Foundation of China(51871133,92045302,21972055,21825202,21733012 and 21972133)the support of Taishan Scholar Foundation of Shandong Province,the program of Jinan Science and Technology Bureau(2019GXRC001)+1 种基金National Key R&D Program of China(2018YFB0104400)the Newton Advanced Fellowships(NAF/R2/180603).
文摘Bi-Sb alloys are appealing anode materials for potassium ion batteries(PIBs)but challenged by their enormous volumetric variation during operation.Herein,a facile one-step dealloying protocol was devised and utilized to prepare the Bi-Sb alloys that manifest an exotic bicontinuous hierarchical nanoporous(np)microstructure ideal for volume-change mitigation and K+transport percolation.The growth mechanism fostering the peculiar morphology of the np-(Bi,Sb)alloys was investigated and clarified via operando X-ray(XRD)and ex-situ scanning electron microscopy(SEM).In particular,the np-Bi6Sb2 electrode,optimized for comprehensive electrochemical performance,achieves decent reversible capacities and a superior lifespan,as benchmarked with the monometallic references and other Bi-Sb alloy electrodes.The(de)potassiation mechanism of the np-(Bi,Sb)alloys was studied by operando XRD and further rationalized by density functional theory(DFT)calculations,whereby a homogeneous(segregation-free)and robust two-step electrochemically-driven phase transformations’catenation of(Bi,Sb)↔K(Bi,Sb)2↔K3(Bi,Sb)was reliably established to substantiate the outstanding reversibility of the np-(Bi,Sb)anodes in PIBs.
文摘Chemical preparation, X-ray single crystal diffraction, thermal analysis, electrochemical measurements, IR, Raman and UV spectroscopic investigations of a novel organic-inorganic hybrid material（CaH7N2）CdCl3（H2O）（1） were described. 1-Methylimidazolium aquapentachlorocadmate（II） crystallized in the monoclinic system with P2 1/n space group. Its structure provided a new interesting example of infinite inorganic layers of [CdCl3（H2O）]n n- centered by （-101） planes. The [CdCl5（H2O）]- anions were interconnected by O-H...Cl hydrogen bonds. Acidic protons of the chloride group were transferred to the organic molecule, giving the singly-protonated cations. The ability of ions to form a spontaneous three-dimensional structure through O-H…Cl and N-H…Cl hydrogen bonds was fully utilized. These hydrogen bonds induced notable vibrational effects. IR and Raman spectra were reported and discussed on the basis of group theoretical analysis and on quantum chemical density theory（DFT） calculation. The molecular HOMO-LUMO compositions and their respective energy gaps were also drawn to explain the activity of our compound. The role of the intermolecular interaction in this crystal was analyzed. The optical study was also investigated by UV-Vis absorption spectrum. Thermal analysis reveals the hydrous character of the compound. Cyclic voltammetry was studied to evaluate the spectral and structural changes accompanying electron transfer.
