Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of preci...Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of precipitates during fabrication,which is strongly correlated with defect concentration.For Fe-Ga alloys,giant magnetostriction can be induced by the precipitation of the nanoscale tetragonal L60 phase.By introducing quenched-in vacancies,we significantly enhance the magnetostriction of the aged Fe81Ga19 polycrystalline alloys to~305 ppm,which is close to the level of single crystals.Although vacancies were found to facilitate the generation of the L60 phase,their impact on the precipitation mechanism and kinetics has yet to be revealed.This study combined transmission electron microscopy(TEM)and time-resolved small-angle neutron scattering(SANS)to investigate the precipitation of the L60 phase during the isothermal aging at 350 and 400℃,respectively.The evolution of L60 nanophase in morphology and number density in as-cast(AC)and liquid nitrogen quenched(LN)Fe81Ga19 alloys with aging time were quantitatively compared.Interestingly,the nucleation of the L60 phase proceeds progressively in AC while suddenly in LN specimens,indicating the homogenous to heterogeneous mechanism switching in-duced by concentrated vacancies.Moreover,excess vacancies can change the shape of nanoprecipitates and significantly accelerate the growth and coarsening kinetics.The magnetostrictive coefficient is opti-mized when the size(long-axis)of L60 precipitates lies between 100 and 110Åwith a number density between 3.2-4.3×10-7Å-3.Insight from this study validates the feasibility of achieving high magnetoe-lastic properties through precise manipulation of the nanostructure.展开更多
Gas targets have been used to measure the scattering length in neutron-proton(n-p)scattering experiments.Changes in electron dynamics within the gas target have a negligible effect on the dynamics of nucleons.However,...Gas targets have been used to measure the scattering length in neutron-proton(n-p)scattering experiments.Changes in electron dynamics within the gas target have a negligible effect on the dynamics of nucleons.However,electron dynamics are sensitively related to the specific form of the n-p interaction during the scattering process.We propose a theoretical approach to explore electron dynamics and determine the parameters of the n-p interaction.This approach is based on a three-body scattering process involving a neutron,a proton and an electron.Numerical results indicate significant differences in electron dynamics with varying values of n-p interaction parameters,providing additional information beyond scattering cross-sections to accurately determine these parameters.展开更多
High entropy alloys(HEAs)constituted of single solid solution phase,but remains chemical inhomogeneity in nature due to its multi-principal composition.Currently,existence of nanoscale spinodal decomposition(SD)phase ...High entropy alloys(HEAs)constituted of single solid solution phase,but remains chemical inhomogeneity in nature due to its multi-principal composition.Currently,existence of nanoscale spinodal decomposition(SD)phase in matrix was found to have significant impact on the properties of HEAs.Nevertheless,the morphology evolution and the kinetics of SD is not clear,which hinders in-depth understanding of the structure-property relationship.In this study,we examine the spinodal structures in(FeCoCrNi)85(AlCu)15 HEAs at different states using in-situ small-angle neutron scattering(SANS),in conjunction with transmission electron microscopy technique.The result demonstrates that SD occurred when aging the HEA samples at temperatures ranging from 500 to 800℃,which leads to the phase constitution of NiAlCu-rich and FeCoCr-rich spinodal phases,L1_(2)ordered phases,and FCC matrix.The characteristic wavelength of SD(λ_(SD))grows from 5.31 to 51.26 nm when aging temperature rises from 500 to 800℃,which explains the enhancement of the alloy’s microhardness.The SD kinetics was unraveled by fitting the time-dependentλ_(SD)through in-situ SANS measurement at 700℃.During isothermal treatment at 700℃,theλ_(SD)increases from 10.42 to 17.43 nm with prolonged time,and SD is in the late stage from the exponential trend of theλ_(SD)over time.Moreover,comparing with aging temperature,the aging time has a relatively minor impact on the coarsening of SD.展开更多
The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam...The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam at the Dalat <span>Nuclear Reactor (DNR). The system is used for research and training in the</span> field <span>of material structure analysis by neutron scattering and diffraction tech</span>nique</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "="">. It is designed on the basis of inheriting the neutron measurement spectrometer systems at the DNR and the scattered neutron measurement systems in the world. The measuring system, which was installed at the hori<span>zontal channel</span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">4 of the DNR, consists of </span></span><span><span style="font-family:;" "="">5-helium-3 detectors and a fully</span></span><span><span style="font-family:;" "=""> electronic system to record the scatter counts <span>and a mechanical system with the possibility of rotating at 15</span></span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "="">-</span></span><span><span style="font-family:;" "="">75</span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">angles. The constructed system is tested for <span>evaluation of the accuracy, stability and reliability of the mechanical and</span> electronic systems of moving detector</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "=""> by angles.</span></span>展开更多
The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the...The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the experimental data of quasi-elastic neutron scattering（QENS） spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum（HWHM） Γ;（Q） and Γ;（Q）,the self-diffusion coefficients D;and D;of water molecules,the average residence times τ;and τ;,and the proton mean squared displacement（MSD）(u;) are obtained.The results show that the QENS spectra can be fitted very well not only for small Q（≤1 A;） but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A;（the MSD of bound/immobile water） as the Q increases to 1.9 A;no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of D;,τ;,and Γ;（Q）,a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores（LGPs） and/or small gel pores（SGPs） contained in the C-S-H gel sample with 30% water content.展开更多
The correlation between aggregates and bound rubber structures in silicone rubbers(S(phr)) with various silica fractions(ΦSi) has been investigated by contrast matching small-angle neutron scattering(SANS), swelling ...The correlation between aggregates and bound rubber structures in silicone rubbers(S(phr)) with various silica fractions(ΦSi) has been investigated by contrast matching small-angle neutron scattering(SANS), swelling kinetics, and low-field nuclear magnetic resonance(NMR).Mixed solvents with deuterated cyclohexane fractions of 4.9% and 53.7% were chosen to match the scattering length densities of the matrix(SMP(phr)) and the filler(SMS(phr)), respectively. All the data consistently suggest that:(i) There is a critical threshold ΦSic between 10 and 30 phr;below ΦSic, the isolated aggregates are dominant, while beyond ΦSic, some rubber fraction is trapped among the agglomerate;(ii) ΦSiindependent thicknesses around 7.5 nm(NMR) and 8.6 nm(SANS) suggest that the bound rubber formation is determined by inherent properties of the components, and the power-law around 4.2 suggests an exponential changed gradient density of the bound rubber;(iii) SMS(80) presents a bicontinuous bound rubber with three characteristic lengths of 41, 100, and 234 nm. The expanded correlation length, a 20 nm smaller aggregate sizes suggest that such existent bicontinuous network in dry samples with less ΦSi is kind of impacted by swelling. With the obtained bound rubber models, the reinforcing mechanism of filled silicone rubber is elucidated.展开更多
The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It...The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It is found that the striking effects of the influence of the pseudogap on the incommensurability of the spin excitation spectrum are that in the superconducting state the pseudogap makes the intensity of the incommensurate peak increase, in the normal state the pseudogap not only makes the intensity of the incommensurate peak increase, but also sharpens the incommensurate peak and increases incommensurability.展开更多
A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scat...A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.展开更多
Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the s...Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the samples with different milling time.Interesting fractal-like behavior of the sample system have been found and attempts have been made to determine the fractal dimensions. It is expected that the fractal dimension can be related to the different stages of MA to some extent.展开更多
In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a vari...In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a variety of different intermolecular potentials from simple classic pair-wise (rigid and non-rigid molecule) potentials to sophisticated polarisable potentials. It was found that MCY makes stretching and bending interactions too weak while others do them well. We demonstrate that in order to reproduce the measured neutron spectrum, greater anisotropy (or orientational variation) is required than these potentials presently provide.展开更多
The dynamics of methanol within prototype methanol synthesis catalysts were studied using quasi-elastic neutron scattering.Three Cu-exchanged zeolites(mordenite,SSZ-13 and ZSM-5)were studied after methanol loading and...The dynamics of methanol within prototype methanol synthesis catalysts were studied using quasi-elastic neutron scattering.Three Cu-exchanged zeolites(mordenite,SSZ-13 and ZSM-5)were studied after methanol loading and showed jump diffusion coefficients between 1.04×10^(−10)and 2.59×10^(−10)m^(2)·s^(-1).Non-Arrhenius behavior was observed with varying temperature due to methoxy formation at Brønsted acid sites and methanol clustering around copper cations.展开更多
Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micr...Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, Dll in Grenoble, was built in 1972, new collimation techniques, focusing optics （multi-beam converging apertures, material or magnetic lenses, and focusing mirrors） and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source （CSNS） is thereby presented.展开更多
After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the ...After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the superconducting Cooper pairs.The recent discovery of high-temperature superconductivity near 80 K in the bilayer nickelate La_(3)Ni_(2)O_(7)under pressure provides a new platform to elucidate the origins of high-temperature superconductivity.We perform elastic and inelastic neutron scattering studies on a polycrystalline sample of La_(3)Ni_(2)O_(7-δ)at ambient pressure.No magnetic order can be identified down to 10 K.The absence of long-range magnetic order in neutron diffraction measurements may be ascribed to the smallness of the magnetic moment.However,we observe a weak flat spin-fluctuation signal in the inelastic scattering spectra at~45 meV.The observed spin excitations could be interpreted as a result of strong interlayer and weak intralayer magnetic couplings for stripe-type antiferromagnetic orders.Our results provide crucial information on the spin dynamics and are thus important for understanding the superconductivity in La_(3)Ni_(2)O_(7).展开更多
Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can ...Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.展开更多
Over last decades,the development of new organic materials has contributed to the rapid increase of high-power conversion efficiency of photovoltaic cells.At this stage,to understand the structure and the dynamic of m...Over last decades,the development of new organic materials has contributed to the rapid increase of high-power conversion efficiency of photovoltaic cells.At this stage,to understand the structure and the dynamic of materials is of significant importance for designing novel low-cost photovoltaic cells with superior performance.Neutron scattering is a powerful tool to provide unique and non-destructive information for the organic photovoltaic materials with particular advantages of addressing different parts of organic system by deuterium or tritium substitution.In addition,by employing several neutron scattering methods together,it is possible to further access the static structure and dynamic relaxation of the materials.With this perspective review,we introduce three neutron scattering techniques,including neutron reflectivity,small angle neutron scattering,grazing incidence small angle neutron scattering and quasi-elastic neutron scattering,and their applications on the organic photovoltaic materials.展开更多
Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the ho...Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the hole overdoped Ba_(0.4)K_(0.6)Fe_(2)As_(2) near a Lifshitz transition,where the electron pocket at M point is nearly replaced by four hole pockets.In the normal state,the spin excitations is observed at incommensurate wave vectors with a chimney-like dispersion.By cooling down to the superconducting state,a neutron spin resonance mode emerges with a peak energy of Er=14-15 meV,weakly modulated along the L-direction.The incommensurability notably increases at low energies,giving rise to downward dispersions of the resonance mode.This behavior contrasts sharply with the upward dispersions of resonance observed in optimally doped Ba_(0.67)K_(0.33)Fe_(2)As_(2) contributed by the hole to electron scattering,but resembles those in KFe_(2)As_(2) and KCa_(2)Fe_(4)As_(4)F_(2) where the fermiology is dominated by hole pockets.These results highlight the critical role of electronic structure modifications near the Fermi level,especially in governing interband scattering under imperfect nesting conditions,which fundamentally shape the spin dynamics of FeSCs.展开更多
A method is proposed to characterize the fast neutron scattering cross-section ( s f) quantitatively by the combina-tion of inelastic gamma rays and captured gamma rays, so as to realize the gas saturation evaluation ...A method is proposed to characterize the fast neutron scattering cross-section ( s f) quantitatively by the combina-tion of inelastic gamma rays and captured gamma rays, so as to realize the gas saturation evaluation of CO_(2)-injected heavy oilreservoirs based on the three-de tector pulsed neutron logging technology. Factors influencing of the evaluation effect of thismethod are analyzed and the effectiveness of this method is verified by a simulation example. By using the Monte Carlo simu-lation method and the physical model of bulk-volume rock, the relationship between s f and CO_(2) saturation is studied, and thesaturation interpretation model is established. The influences of formation temperature and pressure, heavy oil density, bore-hole fluid and reservoir methane content on the evaluation results of CO_(2) saturation are analyzed. The results show that thecharacterization of s f by the combination of secondary gamma information can eliminate the influence of formation lithology,borehole fluid and methane content are the main factors affecting the quantitative monitoring of CO_(2) saturation, and the ef-fects of formation temperature and pressure and heavy oil density are negligible. The simulation example verified the feasibilityof the method for evaluating the CO_(2) saturation of CO_(2)-injected heavy oil reservoirs.展开更多
During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other...During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other than advanced battery materials,in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery.Advanced characterization techniques,especially neutron-based techniques,have greatly promoted Li-ion battery researches.In this review,the characteristics or capabilities of various neutron-based characterization techniques,including elastic neutron scattering,quasi-elastic neutron scattering,neutron imaging,and inelastic neutron scattering,for the related Li-ion-battery researches are summarized.The design of in-situ/operando environment is also discussed.The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.展开更多
Amorphous materials are ubiquitous and widely used in human society, yet their structures are far from being fully understood. Metallic glasses, a new class of amorphous materials, have attracted a great deal of inter...Amorphous materials are ubiquitous and widely used in human society, yet their structures are far from being fully understood. Metallic glasses, a new class of amorphous materials, have attracted a great deal of interests due to their exceptional properties. In recent years, our understanding of metallic glasses increases dramatically, thanks to the development of advanced instrumentation, such as in situ x-ray and neutron scattering. In this article, we provide a brief review of recent progress in study of the structure of metallic glasses. In particular, we will emphasize, from the scattering perspective, the multiscale structures of metallic glasses, i.e., short-to-medium range atomic packing, and phase transitions in the supercooled liquid region, e.g., crystallization and liquid-to-liquid phase transition. We will also discuss, based on the understanding of their structures and phase stability, the mechanical and magnetic properties of metallic glasses.展开更多
Empirical potential structure refinement is a neutron scattering data analysis algorithm and a software package.It was developed by the disordered materials group in the British spallation neutron source(ISIS)in 1980s...Empirical potential structure refinement is a neutron scattering data analysis algorithm and a software package.It was developed by the disordered materials group in the British spallation neutron source(ISIS)in 1980s,and aims to construct the most-probable atomic structures of disordered materials in the field of chemical physics.It has been extensively used during the past decades,and has generated reliable results.However,it implements a shared-memory architecture with open multi-processing(OpenMP).With the extensive construction of supercomputer clusters and the widespread use of graphics processing unit(GPU)acceleration technology,it is now possible to rebuild the EPSR with these techniques in the effort to improve its calculation speed.In this study,an open source framework NeuDATool is proposed.It is programmed in the object-oriented language C++,can be paralleled across nodes within a computer cluster,and supports GPU acceleration.The performance of NeuDATool has been tested with water and amorphous silica neutron scattering data.The test shows that the software can reconstruct the correct microstructure of the samples,and the calculation speed with GPU acceleration can increase by more than 400 times,compared with CPU serial algorithm at a simulation box that has about 100 thousand atoms.NeuDATool provides another choice to implement simulation in the(neutron)diffraction community,especially for experts who are familiar with C++programming and want to define specific algorithms for their analysis.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12275154)the Guangdong Basic and Applied Basic Research Foundation,China(Project No.2021B1515140028)+1 种基金the Youth Innovation Promotion Association,CAS(No.2020010)the National Key Research and Development Program of China,grant number(Nos.2021YFA1600701 and 2021YFB3501201).
文摘Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of precipitates during fabrication,which is strongly correlated with defect concentration.For Fe-Ga alloys,giant magnetostriction can be induced by the precipitation of the nanoscale tetragonal L60 phase.By introducing quenched-in vacancies,we significantly enhance the magnetostriction of the aged Fe81Ga19 polycrystalline alloys to~305 ppm,which is close to the level of single crystals.Although vacancies were found to facilitate the generation of the L60 phase,their impact on the precipitation mechanism and kinetics has yet to be revealed.This study combined transmission electron microscopy(TEM)and time-resolved small-angle neutron scattering(SANS)to investigate the precipitation of the L60 phase during the isothermal aging at 350 and 400℃,respectively.The evolution of L60 nanophase in morphology and number density in as-cast(AC)and liquid nitrogen quenched(LN)Fe81Ga19 alloys with aging time were quantitatively compared.Interestingly,the nucleation of the L60 phase proceeds progressively in AC while suddenly in LN specimens,indicating the homogenous to heterogeneous mechanism switching in-duced by concentrated vacancies.Moreover,excess vacancies can change the shape of nanoprecipitates and significantly accelerate the growth and coarsening kinetics.The magnetostrictive coefficient is opti-mized when the size(long-axis)of L60 precipitates lies between 100 and 110Åwith a number density between 3.2-4.3×10-7Å-3.Insight from this study validates the feasibility of achieving high magnetoe-lastic properties through precise manipulation of the nanostructure.
基金supported by the National Natural Science Foundation of China(Grant Nos.12088101 and No.U2330401)。
文摘Gas targets have been used to measure the scattering length in neutron-proton(n-p)scattering experiments.Changes in electron dynamics within the gas target have a negligible effect on the dynamics of nucleons.However,electron dynamics are sensitively related to the specific form of the n-p interaction during the scattering process.We propose a theoretical approach to explore electron dynamics and determine the parameters of the n-p interaction.This approach is based on a three-body scattering process involving a neutron,a proton and an electron.Numerical results indicate significant differences in electron dynamics with varying values of n-p interaction parameters,providing additional information beyond scattering cross-sections to accurately determine these parameters.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFA1600701)the Guangdong Basic and Applied Basic Research Foundation,China(Project No.2021B1515140028)the National Natural Science Foundation of China(Grant No.12275154)。
文摘High entropy alloys(HEAs)constituted of single solid solution phase,but remains chemical inhomogeneity in nature due to its multi-principal composition.Currently,existence of nanoscale spinodal decomposition(SD)phase in matrix was found to have significant impact on the properties of HEAs.Nevertheless,the morphology evolution and the kinetics of SD is not clear,which hinders in-depth understanding of the structure-property relationship.In this study,we examine the spinodal structures in(FeCoCrNi)85(AlCu)15 HEAs at different states using in-situ small-angle neutron scattering(SANS),in conjunction with transmission electron microscopy technique.The result demonstrates that SD occurred when aging the HEA samples at temperatures ranging from 500 to 800℃,which leads to the phase constitution of NiAlCu-rich and FeCoCr-rich spinodal phases,L1_(2)ordered phases,and FCC matrix.The characteristic wavelength of SD(λ_(SD))grows from 5.31 to 51.26 nm when aging temperature rises from 500 to 800℃,which explains the enhancement of the alloy’s microhardness.The SD kinetics was unraveled by fitting the time-dependentλ_(SD)through in-situ SANS measurement at 700℃.During isothermal treatment at 700℃,theλ_(SD)increases from 10.42 to 17.43 nm with prolonged time,and SD is in the late stage from the exponential trend of theλ_(SD)over time.Moreover,comparing with aging temperature,the aging time has a relatively minor impact on the coarsening of SD.
文摘The objective of this study is to design an elastic neutron scattering system<span><span style="font-family:;" "=""> according to the angle with a sample using thermal neutron beam at the Dalat <span>Nuclear Reactor (DNR). The system is used for research and training in the</span> field <span>of material structure analysis by neutron scattering and diffraction tech</span>nique</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "="">. It is designed on the basis of inheriting the neutron measurement spectrometer systems at the DNR and the scattered neutron measurement systems in the world. The measuring system, which was installed at the hori<span>zontal channel</span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">4 of the DNR, consists of </span></span><span><span style="font-family:;" "="">5-helium-3 detectors and a fully</span></span><span><span style="font-family:;" "=""> electronic system to record the scatter counts <span>and a mechanical system with the possibility of rotating at 15</span></span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "="">-</span></span><span><span style="font-family:;" "="">75</span></span><span><span style="font-family:;" "=""><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span><span><span style="font-family:;" "=""> </span></span><span><span style="font-family:;" "="">angles. The constructed system is tested for <span>evaluation of the accuracy, stability and reliability of the mechanical and</span> electronic systems of moving detector</span></span><span><span style="font-family:;" "="">s</span></span><span><span style="font-family:;" "=""> by angles.</span></span>
文摘The dynamic behaviors of water contained in calcium-silicate-hydrate（C-S-H） gel with different water content values from 10%to 30%（by weight）,are studied by using an empirical diffusion model（EDM） to analyze the experimental data of quasi-elastic neutron scattering（QENS） spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum（HWHM） Γ;（Q） and Γ;（Q）,the self-diffusion coefficients D;and D;of water molecules,the average residence times τ;and τ;,and the proton mean squared displacement（MSD）(u;) are obtained.The results show that the QENS spectra can be fitted very well not only for small Q（≤1 A;） but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A;（the MSD of bound/immobile water） as the Q increases to 1.9 A;no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of D;,τ;,and Γ;（Q）,a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores（LGPs） and/or small gel pores（SGPs） contained in the C-S-H gel sample with 30% water content.
基金financially supported by the National Key R&D Program of China (No. 2018YFB0704200)the National Natural Science Foundation of China (Nos. 11605171 and 11705173)the Foundation of President of CAEP (No. YZJJLX2018004)。
文摘The correlation between aggregates and bound rubber structures in silicone rubbers(S(phr)) with various silica fractions(ΦSi) has been investigated by contrast matching small-angle neutron scattering(SANS), swelling kinetics, and low-field nuclear magnetic resonance(NMR).Mixed solvents with deuterated cyclohexane fractions of 4.9% and 53.7% were chosen to match the scattering length densities of the matrix(SMP(phr)) and the filler(SMS(phr)), respectively. All the data consistently suggest that:(i) There is a critical threshold ΦSic between 10 and 30 phr;below ΦSic, the isolated aggregates are dominant, while beyond ΦSic, some rubber fraction is trapped among the agglomerate;(ii) ΦSiindependent thicknesses around 7.5 nm(NMR) and 8.6 nm(SANS) suggest that the bound rubber formation is determined by inherent properties of the components, and the power-law around 4.2 suggests an exponential changed gradient density of the bound rubber;(iii) SMS(80) presents a bicontinuous bound rubber with three characteristic lengths of 41, 100, and 234 nm. The expanded correlation length, a 20 nm smaller aggregate sizes suggest that such existent bicontinuous network in dry samples with less ΦSi is kind of impacted by swelling. With the obtained bound rubber models, the reinforcing mechanism of filled silicone rubber is elucidated.
文摘The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It is found that the striking effects of the influence of the pseudogap on the incommensurability of the spin excitation spectrum are that in the superconducting state the pseudogap makes the intensity of the incommensurate peak increase, in the normal state the pseudogap not only makes the intensity of the incommensurate peak increase, but also sharpens the incommensurate peak and increases incommensurability.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0702400)。
文摘A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.
文摘Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the samples with different milling time.Interesting fractal-like behavior of the sample system have been found and attempts have been made to determine the fractal dimensions. It is expected that the fractal dimension can be related to the different stages of MA to some extent.
基金We would like to thank National Natural Science Foundation of China(Grand No.10144001)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,for their financial supports.
文摘In this article we describe a range of simulations (lattice dynamics and molecular dynamics) of the inelastic incoherent neutron scattering spectra of ices (normal ice, ice Ⅱ and ice Ⅷ). These simulations use a variety of different intermolecular potentials from simple classic pair-wise (rigid and non-rigid molecule) potentials to sophisticated polarisable potentials. It was found that MCY makes stretching and bending interactions too weak while others do them well. We demonstrate that in order to reproduce the measured neutron spectrum, greater anisotropy (or orientational variation) is required than these potentials presently provide.
基金the support of the Australian Centre for Neutron Scattering,ANSTO and the Australian Government through the National Collaborative Research Infrastructure Strategy,in supporting the neutron research infrastructure used in this work via ACNS proposal P13488The ISIS neutron and Muon source also awarded a grant of beamtime(RB2220457).
文摘The dynamics of methanol within prototype methanol synthesis catalysts were studied using quasi-elastic neutron scattering.Three Cu-exchanged zeolites(mordenite,SSZ-13 and ZSM-5)were studied after methanol loading and showed jump diffusion coefficients between 1.04×10^(−10)and 2.59×10^(−10)m^(2)·s^(-1).Non-Arrhenius behavior was observed with varying temperature due to methoxy formation at Brønsted acid sites and methanol clustering around copper cations.
基金Supported by National Natural Science Foundation of China(21474119,11305191)
文摘Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, Dll in Grenoble, was built in 1972, new collimation techniques, focusing optics （multi-beam converging apertures, material or magnetic lenses, and focusing mirrors） and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source （CSNS） is thereby presented.
基金supported by the National Key Research and Development Program of China(2023YFA1406500,2023YFA1406000)the National Natural Science Foundation of China(12304187,12174454,U21301001)+5 种基金the Guangdong Basic and Applied Basic Research Funds(2024B1515020040,2024A1515030030,2022A1515011618)Guangzhou Basic and Applied Basic Research Funds(202201011123,2024A04J4024,2024A04J6417)Shenzhen Science and Technology Program(RCYX20231211090245050)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(2022B1212010008)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(23qnpy57)the open research fund of Songshan Lake Materials Laboratory(2023SLABFN30)。
文摘After several decades of studies of high-temperature superconductivity,there is no compelling theory for the mechanism yet;however,the spin fluctuations have been widely believed to play a crucial role in forming the superconducting Cooper pairs.The recent discovery of high-temperature superconductivity near 80 K in the bilayer nickelate La_(3)Ni_(2)O_(7)under pressure provides a new platform to elucidate the origins of high-temperature superconductivity.We perform elastic and inelastic neutron scattering studies on a polycrystalline sample of La_(3)Ni_(2)O_(7-δ)at ambient pressure.No magnetic order can be identified down to 10 K.The absence of long-range magnetic order in neutron diffraction measurements may be ascribed to the smallness of the magnetic moment.However,we observe a weak flat spin-fluctuation signal in the inelastic scattering spectra at~45 meV.The observed spin excitations could be interpreted as a result of strong interlayer and weak intralayer magnetic couplings for stripe-type antiferromagnetic orders.Our results provide crucial information on the spin dynamics and are thus important for understanding the superconductivity in La_(3)Ni_(2)O_(7).
基金Acknowledgements M.R. Eskildsen was supported by the U. S. National Science Foundation through grant DMR-0804887. Collaboration and stimulating discussions are acknowledged with： A. B. Abrahamsen, T. M. Artemova, E. D. Bauer, A. D. Bianchi, T. D. Blasius, S. L. Bud＇ko, P. C. Canfield, P. Das, L. DeBeer-Schmitt, J. M. Densmore, C. D. Dewhurst, Z. Fisk, E. M. Forgan, J. L. Gavilano, S. Gerber, A. I. Coldman, M. Ichioka, R. Ikeda, N. Jenkins, M. Kenzelmann, V. G. Kogan, J. Kohlbrecher, A. Kreyssig, M. Laver, K. Machida, J. Mesot, R. Movshovich, N. Ni, T. O＇Brien, C. Petrovic, R. Prozorov, K. Rovira, J. L. Sarrao, I. S. Veshchunov, L. Ya. Vinnikov. J. S. White and M. Zolliker.
文摘Here we review recent small-angle scattering studies of the vortex lattice in a range of type-II superconductors carried out by our group. Emphasis is placed on providing examples of the kind of information which can be obtained by such measurements, focusing in particular on studies of the vortex lattice structure and form factor in LuNi2B2C, TmNi2B2C, CeCoIn5 and Ba（Fe0.93Co0.07）2As2.
基金supported by the National Natural Science Foundation of China(No.12105306,52072008 and U2032167)Guangdong Natural Science Foundation(No.2019A1515111028)+1 种基金Xiejialin Foundation in the Institute of High Energy Physics(No.E15466U210)National Key R&D Projects(2022YFA1604103 and 2020YFA0406203).
文摘Over last decades,the development of new organic materials has contributed to the rapid increase of high-power conversion efficiency of photovoltaic cells.At this stage,to understand the structure and the dynamic of materials is of significant importance for designing novel low-cost photovoltaic cells with superior performance.Neutron scattering is a powerful tool to provide unique and non-destructive information for the organic photovoltaic materials with particular advantages of addressing different parts of organic system by deuterium or tritium substitution.In addition,by employing several neutron scattering methods together,it is possible to further access the static structure and dynamic relaxation of the materials.With this perspective review,we introduce three neutron scattering techniques,including neutron reflectivity,small angle neutron scattering,grazing incidence small angle neutron scattering and quasi-elastic neutron scattering,and their applications on the organic photovoltaic materials.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406100,2018YFA0704200,2022YFA1403400 and 2021YFA1400400)the National Natural Science Foundation of China(Grant Nos.11822411 and 12274444)+2 种基金the Strategic Priority Research Program(B)of the CAS(Grant Nos.XDB25000000 and XDB33000000)K.C.Wong Education Foundation(GJTD-2020-01)AP by HBNI-RRCAT and MPCST under the FTYS program。
文摘Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the hole overdoped Ba_(0.4)K_(0.6)Fe_(2)As_(2) near a Lifshitz transition,where the electron pocket at M point is nearly replaced by four hole pockets.In the normal state,the spin excitations is observed at incommensurate wave vectors with a chimney-like dispersion.By cooling down to the superconducting state,a neutron spin resonance mode emerges with a peak energy of Er=14-15 meV,weakly modulated along the L-direction.The incommensurability notably increases at low energies,giving rise to downward dispersions of the resonance mode.This behavior contrasts sharply with the upward dispersions of resonance observed in optimally doped Ba_(0.67)K_(0.33)Fe_(2)As_(2) contributed by the hole to electron scattering,but resembles those in KFe_(2)As_(2) and KCa_(2)Fe_(4)As_(4)F_(2) where the fermiology is dominated by hole pockets.These results highlight the critical role of electronic structure modifications near the Fermi level,especially in governing interband scattering under imperfect nesting conditions,which fundamentally shape the spin dynamics of FeSCs.
基金Supported by the National Natural Science Foundation of China(41974127,41974155)China University of Petroleum(East China)Graduate Student Innovation Project Funding Project(YCX2020008)。
文摘A method is proposed to characterize the fast neutron scattering cross-section ( s f) quantitatively by the combina-tion of inelastic gamma rays and captured gamma rays, so as to realize the gas saturation evaluation of CO_(2)-injected heavy oilreservoirs based on the three-de tector pulsed neutron logging technology. Factors influencing of the evaluation effect of thismethod are analyzed and the effectiveness of this method is verified by a simulation example. By using the Monte Carlo simu-lation method and the physical model of bulk-volume rock, the relationship between s f and CO_(2) saturation is studied, and thesaturation interpretation model is established. The influences of formation temperature and pressure, heavy oil density, bore-hole fluid and reservoir methane content on the evaluation results of CO_(2) saturation are analyzed. The results show that thecharacterization of s f by the combination of secondary gamma information can eliminate the influence of formation lithology,borehole fluid and methane content are the main factors affecting the quantitative monitoring of CO_(2) saturation, and the ef-fects of formation temperature and pressure and heavy oil density are negligible. The simulation example verified the feasibilityof the method for evaluating the CO_(2) saturation of CO_(2)-injected heavy oil reservoirs.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFA0401503)the National Materials Genome Project of China(Grant No.2016YFB0100106)the National Natural Science Foundation of China(Grant No.11675255)
文摘During the past decades,Li-ion batteries have been one of the most important energy storage devices.Large-scale energy storage requires Li-ion batteries which possess high energy density,low cost,and high safety.Other than advanced battery materials,in-depth understanding of the intrinsic mechanism correlated with cell reaction is also essential for the development of high-performance Li-ion battery.Advanced characterization techniques,especially neutron-based techniques,have greatly promoted Li-ion battery researches.In this review,the characteristics or capabilities of various neutron-based characterization techniques,including elastic neutron scattering,quasi-elastic neutron scattering,neutron imaging,and inelastic neutron scattering,for the related Li-ion-battery researches are summarized.The design of in-situ/operando environment is also discussed.The comprehensive survey on neutron-based characterizations for mechanism understanding will provide guidance for the further study of high-performance Li-ion batteries.
基金supported by Shenzhen Science and Technology Innovation Commission of China(Grant No.R-IND8701)the Croucher Foundation(Project No.City U 9500020)+2 种基金partially supported by the Fundamental Research Funds for the Central Universities of China(Grant No.30915015103)the National Natural Science Foundation of China(Grant No.51501090)partially supported by the National Natural Science Foundation of China(Grant No.51571170)
文摘Amorphous materials are ubiquitous and widely used in human society, yet their structures are far from being fully understood. Metallic glasses, a new class of amorphous materials, have attracted a great deal of interests due to their exceptional properties. In recent years, our understanding of metallic glasses increases dramatically, thanks to the development of advanced instrumentation, such as in situ x-ray and neutron scattering. In this article, we provide a brief review of recent progress in study of the structure of metallic glasses. In particular, we will emphasize, from the scattering perspective, the multiscale structures of metallic glasses, i.e., short-to-medium range atomic packing, and phase transitions in the supercooled liquid region, e.g., crystallization and liquid-to-liquid phase transition. We will also discuss, based on the understanding of their structures and phase stability, the mechanical and magnetic properties of metallic glasses.
基金supported by the National Key Research and Development Program of China(No.2017YFA-0403703)the National Natural Science Foundation of China(No.U1830205,No.21674020).
文摘Empirical potential structure refinement is a neutron scattering data analysis algorithm and a software package.It was developed by the disordered materials group in the British spallation neutron source(ISIS)in 1980s,and aims to construct the most-probable atomic structures of disordered materials in the field of chemical physics.It has been extensively used during the past decades,and has generated reliable results.However,it implements a shared-memory architecture with open multi-processing(OpenMP).With the extensive construction of supercomputer clusters and the widespread use of graphics processing unit(GPU)acceleration technology,it is now possible to rebuild the EPSR with these techniques in the effort to improve its calculation speed.In this study,an open source framework NeuDATool is proposed.It is programmed in the object-oriented language C++,can be paralleled across nodes within a computer cluster,and supports GPU acceleration.The performance of NeuDATool has been tested with water and amorphous silica neutron scattering data.The test shows that the software can reconstruct the correct microstructure of the samples,and the calculation speed with GPU acceleration can increase by more than 400 times,compared with CPU serial algorithm at a simulation box that has about 100 thousand atoms.NeuDATool provides another choice to implement simulation in the(neutron)diffraction community,especially for experts who are familiar with C++programming and want to define specific algorithms for their analysis.
