Development of High-Pressure Multigrain X-Ray Diffraction for Exploring the Earth’s Interior

The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.

Highly active and stable Co nanoparticles embedded in nitrogen-doped mesoporous carbon nanofibers for aqueous-phase levulinic acid hydrogenation

Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanoparticles(NPs)embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient catalyst for aqueous-phase LA hydrogenation to GVL.The Co zeolitic imidazolate framework(ZIF-67)nanocrystals were anchored on the sodium dodecyl sulfate modified wipe fiber(WF-S),yielding one-dimensional(1-D)structured composite(ZIF-67/WF-S).Subsequently,Co NPs were uniformly embedded in nitrogen-doped mesoporous carbon nanofibers(Co^(R)NC/SMCNF)through a pyrolysis-reduction strategy using ZIF-67/WF-S as the precursor.Benefiting from introducing modified wipe fiber WF-S to enhance the dispersion of Co NPs,and Co^(0) with Co-N_xdual active sites,the resulting Co^(R)NC/SMCNF catalyst shows brilliant catalytic activity(206 h^(-1) turnover frequency).Additionally,the strong metal-support interactions greatly inhibited the Co NPs from aggregation and leaching from the mesoporous carbon nanofibers,and thus increasing the reusability of the Co^(R)NC/SMCNF catalyst(reusable nine times without notable activity loss).

Fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios

We present a fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios. Utilizing the high flux of the X-rays generated from the third-generation synchrotron source, we can complete a high- resolution tomography scan within a short period of time, after which the three-dimensional （3D） packing structure can be obtained for the subsequent structural analysis. The image phase-retrieval procedure has been implemented to enhance the image contrast. We systematically investigated the effects of particle shape and aspect ratio on the structural properties including packing density and contact number. It turns out that large aspect ratio rod packings will have wider distributions of free volume fraction and larger mean contact numbers.

Temperature-dependent constitutive modeling of a magnesium alloy ZEK100 sheet using crystal plasticity models combined with in situ high-energy X-ray diffraction experiment

A multiscale crystal plasticity model accounting for temperature-dependent mechanical behaviors without introducing a larger number of unknown parameters was developed.The model was implemented in elastic-plastic self-consistent(EPSC)and crystal plasticity finite element(CPFE)frameworks for grain-scale simulations.A computationally efficient EPSC model was first employed to estimate the critical resolved shear stress and hardening parameters of the slip and twin systems available in a hexagonal close-packed magnesium alloy,ZEK100.The constitutive parameters were thereafter refined using the CPFE.The crystal plasticity frameworks incorporated with the temperature-dependent constitutive model were used to predict stress–strain curves in macroscale and lattice strains in microscale at different testing temperatures up to 200℃.In particular,the predictions by the crystal plasticity models were compared with the measured lattice strain data at the elevated temperatures by in situ high-energy X-ray diffraction,for the first time.The comparison in the multiscale improved the fidelity of the developed temperature-dependent constitutive model and validated the assumption with regard to the temperature dependency of available slip and twin systems in the magnesium alloy.Finally,this work provides a time-efficient and precise modeling scheme for magnesium alloys at elevated temperatures.

磁控功能合金功能行为的原位表征——高能X射线与中子衍射技术

报道了课题组在国际上率先开展利用同步辐射高能X射线衍射和中子衍射技术,成功地实现了多场(温度场,磁场,应力场)耦合作用下,铁磁性记忆合金微结构、晶粒取向、磁结构、母相与变体取向及其与功能行为耦合的原位研究。利用原位飞行时间中子衍射技术,跟踪了铁磁性形状记忆合金Ni-Mn-Ga在单轴压力下马氏体变体的转变行为,这是目前其它方法(如EBSD)仍无法实现的。测试了M_s点为393K的Ni_(47)Mn_(25)Ga_(22)Co_4合金在不同的单轴压力(0,-60MPa,-110MPa,-140MPa,-7MPa)下从523～298K之间的中子衍射花样,并利用GSAS软件获得了不同单轴压力下马氏体相的反极图(IPFs)。利用高能球磨及后续热处理的方法制备出了Ni_(51)Mn_(27)Ga_(22)纳米颗粒。铁磁性Ni_2MnGa纳米颗粒功能行为受晶粒尺寸,原子有序度及固有磁结构交互作用的影响,经历了各种不同的结构转变序,这与它们相应的块体材料是完全不同的。通过高能球磨法制备出尺寸分布均匀约10 nm左右的Ni_(51)Mn_(27)Ga_(22)颗粒,其室温晶体结构由原始的体心四方结构转变为一种无序面心立方结构。高能球磨后的纳米颗粒经过623K,4h退火后,又完全转变为Heusler母相结构。利用高能X射线研究了该纳米颗粒在退火过程中结构的原位转变,证明转变动力学由一种具有非晶结构的中间相控制。高能球磨及后续热处理之后的纳米粒子,在约274K下转变为调制马氏体(14M)结构,并且该结构可以稳定到4K。

Controlled high-density interface engineering of Fe_(3)O_(4)-FeS nanoarray for efficient hydrogen evolution

The rational design of double active sites system is vital for constructing high-efficiency iron sulfides electrocatalysts towards hydrogen evolution reaction(HER) in alkaline media. However, it remains a challenge to controllably create the high-density interface of double sites for optimal synergistic effect.Herein, we reported a simple chemical oxidation-induced surface reconfiguration strategy to obtain the interface-rich Fe_(3)O_(4)-FeS nanoarray supported on iron foam(Fe_(3)O_(4)-FeS/IF) using FeS nanosheets as precursors. The abundant Fe_(3)O_(4)-FeS interfaces could improve the dispersion of active sites and facilitate the electron transfer, leading to enhanced hydrogen evolution efficiency. And meanwhile, by altering the oxidation temperature, the content of S and O could be effectively controlled, further achieving the ratio optimization of Fe_(3)O_(4)to FeS. Synchrotron-based X-ray absorption near-edge structure, X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy consistently confirm the changes of electronic structure and d-band center of Fe_(3)O_(4)-FeS after chemical oxidation. Consequently, Fe_(3)O_(4)-FeS/IF exhibits excellent alkaline HER activity with a low overpotential of 120.8 mV to reach 20 mA cm^(-2),and remains stable ranging from 10, 20 to 50 mA cm^(-2) for each 20 h, respectively. Therefore, the facile and controllable chemical oxidation may be an effective strategy for designing high-density interfaces of transition metal-based sulfides towards alkaline HER.

Solvation Structure and Dynamics of Mg(TFSI)_(2) Aqueous Electrolyte

Using ab initio molecular dynamics(AIMD)simulations,classical molecular dynamics(CMD)simulations,small-angle X-ray scattering(SAXS),and pulsed-field gradient nuclear magnetic resonance(PFG-NMR),the solvation structure and ion dynamics of magnesium bis(trifluoromethanesulfonyl)imide(Mg(TFSI)_(2))aqueous electrolyte at 1,2,and 3 m concentrations are investigated.From AIMD and CMD simulations,the first solvation shell of an Mg;ion is found to be composed of six water molecules in an octahedral configuration and the solvation shell is rather rigid.The TFSI^(-)ions prefer to stay in the second solvation shell and beyond.Meanwhile,the comparable diffusion coefficients of positive and negative ions in Mg(TFSI)_(2)aqueous electrolytes have been observed,which is mainly due to the formation of the stable[Mg(H_(2)O_(6))_(2)]^(+)complex,and,as a result,the increased effective Mg ion size.Finally,the calculated correlated transference numbers are lower than the uncorrelated ones even at the low concentration of 2 and 3 m,suggesting the enhanced correlations between ions in the multivalent electrolytes.This work provides a molecular-level understanding of how the solvation structure and multivalency of the ion affect the dynamics and transport properties of the multivalent electrolyte,providing insight for rational designs of electrolytes for improved ion transport properties.

Grain size and structure distortion characterization of α-MgAgSb thermoelectric material by powder diffraction

Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg0.97Sb0.99, with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. Here, we report the average grain size of 24–28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron x-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg0.97Sb0.99.

Concurrent multi-peak Bragg coherent x-ray diffraction imaging of 3D nanocrystal lattice displacement via global optimization

In this paper we demonstrated a method to reconstruct vector-valued lattice distortion fields within nanoscale crystals by optimization of a forward model of multi-reflection Bragg coherent diffraction imaging(MR-BCDI)data.The method flexibly accounts for geometric factors that arise when making BCDI measurements,is amenable to efficient inversion with modern optimization toolkits,and allows for globally constraining a single image reconstruction to multiple Bragg peak measurements.This is enabled by a forward model that emulates the multiple Bragg peaks of a MR-BCDI experiment from a single estimate of the 3D crystal sample.We present this forward model,we implement it within the stochastic gradient descent optimization framework,and we demonstrate it with simulated and experimental data of nanocrystals with inhomogeneous internal lattice displacement.We find that utilizing a global optimization approach to MR-BCDI affords a reliable path to convergence of data which is otherwise challenging to reconstruct.

Goss Texture Evolution of Grain Oriented Silicon Steel by High-Energy X-ray Diffraction

High energy synchrotron diffraction offers great potential to study the recrystallization kinetics of metallic materials. To study the formation of Goss texture （{ [10}（001）） of grain oriented （GO） silicon steel during secondary recrystallization process, an in situ experiment using hi gh energy X-ray diffraction was designed. The results showed that the secondary recrystallization began when the heating temperature was 1,494 K, and the grains grew rapidly above this temperature. With an increase in annealing temperature, the large grains with 7 orientation [〈111〉//normal direction] formed and gradually occupied the dominant position. As the annealing temperature increased even further, the grains with Goss orientation to a very large size by devouring the 7 orientation grains that formed in the early annealing stage. A single crystal with a Goss orientation was observed in the GO silicon steel when the annealing temperature was 1,540 K.

In-Situ Annealing Study of Transformation of α and γ Texture of Interstitial-Free Steel Sheet by High-Energy X-Ray Diffraction

High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. An experimental design to study the recrystallization mechanism of interstitial-free （IF） steel was implemented. The whole annealing process of cold-rolled IF steel with 80% reduction was observed in situ using high-energy X-ray diffraction （HEXRD）. The results show how the main texture component of IF steel change, i.e. the α [∥rolling direction （RD）] fiber texture decreases and the γ [∥normal direction （ND）] fiber texture increases. The important part of the α fiber texture is that both the {100} and {112} texture decrease at the beginning of recrystallization. The γ fiber texture increases at the early stage of recrystallization which stems from the increase of {111}. Nevertheless, the {111} does not change after recrystallization. The dynamic evolution of the main texture components {100}, {112}, {111} and {111} is given by in-situ HEXRD.

Microstructural characterization of polycrystalline materials by synchrotron X-rays

Third generation synchrotron X-rays provide an unprecedented opportu- nity for microstructural characterization of many engineering materials as well as natural materials. This article demonstrates the usage of three techniques for the study of structural materials： differential-aperture X-ray microscopy （DAXM）, three-dimensional X- ray diffraction （3DXRD）, and simultaneous wide angle/small angle X-ray scattering （WAXS/SAXS）. DAXM is able to measure the 3D grain structure in polycrystalline materials with high spatial and angular resolution. In a deformed material, streaked diffraction peaks can be used to analyze local dislocation content in individual grains. Compared to DAXM, 3DXRD is able to map grains in bulk materials more quickly at the expense of spatial resolution. It is very useful for studying evolving microstructures when the materials are under deformation. WAXS/SAXS is suitable for studying materials with inhomogeneous structure, such as precipitate strengthened alloys. Structural informa- tion revealed by WAXS and SAXS can be combined for a deeper insight into material behavior. Future development and applications of these three techniques will also be discussed.

NiTi-Nb原位复合材料的准线性超弹性变形

据文献报道,Nb纳米线增强NiTi记忆合金复合材料可展现超常的准线性超弹特性。为揭示该准线性超弹特性的产生和变形机制,通过真空感应熔炼、锻造、拔丝方法原位合成了NiTi-Nb复合材料丝材。TEM显微分析表明,Nb纳米线沿丝材轴向平行分布在纳米晶NiTi基体中。该材料在经历一次9%的预变形后会展现准线性超弹特性,其屈服强度达1.7 GPa,表观Young's模量约34 GPa,准线性超弹性应变接近5.5%。同步辐射高能X射线原位拉伸实验结果表明,准线性超弹性的产生与以下2点原因有关:(1)复合材料经历预变形后,Nb纳米线和NiTi基体间会产生耦合力,再次加载时,NiTi所受的耦合拉应力可以将局部区域应力诱发马氏体相变所需的外应力降低到零附近,并且耦合力越大,加载初期的相变速率越高,经过适当的预变形后,加载初始就能够持续发生高速率相变;(2) NiTi中耦合拉应力呈梯度分布,使相变应力-应变曲线不再是常见的“平台型”,转变为“硬化型”斜线。

Heterostructure engineering in electrode materials for sodium-ion batteries:Recent progress and perspectives

Sodium-ion batteries(SIBs)have stepped into the spotlight as a promising alternative to lithium-ion batteries for large-scale energy storage systems.However,SIB electrode materials,in general,have inferior performance than their lithium counterparts because Nat is larger and heavier than Lit.Heterostructure engineering is a promising strategy to overcome this intrinsic limitation and achieve practical SIBs.We provide a brief review of recent progress in heterostructure engineering of electrode materials and research on how the phase interface influences Nat storage and transport properties.Efficient strategies for the design and fabrication of heterostructures(in situ methods)are discussed,with a focus on the heterostructure formation mechanism.The heterostructure's influence on Nat storage and transport properties arises primarily from local distortions of the structure and chemomechanical coupling at the phase interface,which may accelerate ion/electron diffusion,create additional active sites,and bolster structural stability.Finally,we offer our perspectives on the existing challenges,knowledge gaps,and opportunities for the advancement of heterostructure engineering as a means to develop practical,highperformance sodium-ion batteries.

Pt_(1)/Ni_(6)Co_(1)layered double hydroxides/N-doped graphene for electrochemical non-enzymatic glucose sensing by synergistic enhancement of single atoms and doping

The development of novel single-atom catalysts is important for highly efficient electrochemical catalysis and sensing.In this work,a novel Pt single atoms(SAs)supported on Ni_(6)Co_(1)layered double hydroxides/nitrogen-doped graphene(Pt_(1)/Ni_(6)Co_(1)LDHs/NG)was constructed for electrochemical enzyme-free catalysis and sensing towards glucose.The loading of Pt single atoms increases with doping of Co atoms that generate more anchoring sites for Pt SAs.The resulting Pt_(1)/Ni_(6)Co_(1)LDHs/NG exhibits low oxidative potential of 0.440 V with high sensitivity of 273.78μA·mM^(−1)·cm^(−2)toward glucose,which are 85 mV lower and 15 times higher than those of Ni(OH)_(2),respectively.Pt_(1)/Ni_(6)Co_(1)LDHs/NG also shows excellent selectivity and great stability during 5-week testing.Theoretical and experimental results show that the boosted performance of Pt_(1)/Ni_(6)Co_(1)LDHs/NG originates from its stronger binding energy with glucose and the synergistic effect of Pt SAs,Co doping,and NG.This work provides a general strategy of designing highly active SACs for extending their application in electrochemical sensing.

A peroxidase-like single-atom Fe-N_(5)active site for effective killing human lung adenocarcinoma cells

Single-atom catalyst(SAC)is one of the newest catalysts,and attracts people’s wide attention in cancer therapy based on their characteristics of maximum specific catalytic activity and high stability.We designed and synthesized a Fe-N decorated graphene nanosheet(Fe-N5/GN SAC)with the coordination number of five.Through enzymology and theoretical calculations,the Fe-N5/GN SAC has outstanding intrinsic peroxidase-like catalytic activity due to single-atom Fe site with five-N-coordination structure.We explored its potential on lung cancer therapy,and found that it could kill human lung adenocarcinoma cells(A549)by decomposing hydrogen peroxide(H_(2)O_(2))into toxic reactive oxygen species(ROS)under acidic microenvironment in threedimensional(3D)lung cancer cell model.Our study demonstrates a promising application of SAC with highly efficient single-atom catalytic sites for cancer treatment.

Laser additive manufacturing for infrastructure repair:A case study of a deteriorated steel bridge beam

As our transportation infrastructure ages,its deterioration is becoming a growing concern.Rapid and effective methods for repair can reduce the need for time-and cost-intensive replacement of structures such as roadway bridges.In this work,laser-based additive manufacturing(AM)was developed for the repair of damaged beams in steel bridges.A corroded structural beam of low-carbon A36 steel was selected for this case study and 316L stainless steel was used for repair due to its excellent mechanical properties and corrosion resistance.Simulated repair experiments were performed on specimens extracted from the beam,and prepared with various groove shapes(Rectangular,Trapezoidal,and U-shaped).More in-depth parametric and microstructural studies were carried out with a series of U-shaped specimens repaired with the linear laser input energy varied from 19.5 to 30.0 J mm–1.The tensile properties of the repaired specimens and interface structures were also investigated in detail.It was found that the repaired specimens had a slightly higher tensile strength despite a reduction in tensile elongation compared to the A36 steel base metal.The influence of interfacial microstructure and heterogeneity on the mechanical properties of the repaired specimens was discussed.Our work suggests the promising potential to employ AM for structural repair and provides fundamental insights into processing-structure-property relationships in laser AM-repaired materials.

Robotic pendant drop:containerless liquid for μs-resolved,AI-executable XPCS

The dynamics and structure of mixed phases in a complex fluid can significantly impact its material properties,such as viscoelasticity.Small-angle X-ray Photon Correlation Spectroscopy(SA-XPCS)can probe the spontaneous spatial fluctuations of the mixed phases under various in situ environments over wide spatiotemporal ranges(10−6–103 s/10−10–10−6 m).Tailored material design,however,requires searching through a massive number of sample compositions and experimental parameters,which is beyond the bandwidth of the current coherent X-ray beamline.Using 3.7-μs-resolved XPCS synchronized with the clock frequency at the Advanced Photon Source,we demonstrated the consistency between the Brownian dynamics of~100 nm diameter colloidal silica nanoparticles measured from an enclosed pendant drop and a sealed capillary.The electronic pipette can also be mounted on a robotic arm to access different stock solutions and create complex fluids with highly-repeatable and precisely controlled composition profiles.This closed-loop,AI-executable protocol is applicable to light scattering techniques regardless of the light wavelength and optical coherence,and is a first step towards high-throughput,autonomous material discovery.

Single-Atomic Site Catalyst Enhanced Lateral Flow Immunoassay for Point-of-Care Detection of Herbicide

Point-of-care(POC)detection of herbicides is of great importance due to their impact on the environment and potential risks to human health.Here,we design a single-atomic site catalyst(SASC)with excellent peroxidase-like(POD-like)catalytic activity,which enhances the detection performance of corresponding lateral flow immunoassay(LFIA).The iron single-atomic site catalyst(Fe-SASC)is synthesized from hemin-doped ZIF-8,creating active sites that mimic the Fe active center coordination environment of natural enzyme and their functions.Due to its atomically dispersed iron active sites that result in maximum utilization of active metal atoms,the Fe-SASC exhibits superior POD-like activity,which has great potential to replace its natural counterparts.Also,the catalytic mechanism of Fe-SASC is systematically investigated.Utilizing its outstanding catalytic activity,the Fe-SASC is used as label to construct LFIA(Fe-SASC-LFIA)for herbicide detection.The 2,4-dichlorophenoxyacetic acid(2,4-D)is selected as a target here,since it is a commonly used herbicide as well as a biomarker for herbicide exposure evaluation.A linear detection range of 1-250 ng/mL with a low limit of detection(LOD)of 0.82 ng/mL has been achieved.Meanwhile,excellent specificity and selectivity towards 2,4-D have been obtained.The outstanding detection performance of the Fe-SASC-LFIA has also been demonstrated in the detection of human urine samples,indicating the practicability of this POC detection platform for analyzing the 2,4-D exposure level of a person.We believe this proposed Fe-SASC-LFIA has potential as a portable,rapid,and high-sensitive POC detection strategy for pesticide exposure evaluation.

NiTi-NbTi原位复合材料的Lüders带型变形和载荷转移行为

采用电弧熔炼、锻造和拔丝方法原位合成了一种高Nb含量的NiTi-NbTi记忆合金复合材料。TEM显微分析显示,在材料内部纳米尺度的NbTi和NiTi纤维沿丝材轴向交替分布,NbTi纤维体积分数高达约70%。通过同步辐射高能X射线原位拉伸实验研究了复合材料的变形机制。结果显示,虽然NiTi体积分数仅约30%,但复合材料的变形仍受NiTi的应力诱发相变控制。在加载初期,复合材料先发生均匀变形,并且在拉伸曲线出现屈服平台之前,NiTi已发生均匀相变。当平台出现之后,NiTi转而发生Lüders带型相变,进而诱发NbTi也随之发生Lüders带型变形,使整个复合材料都展现Lüders带型变形。Lüders带前沿存在载荷转移现象,载荷由正在发生相变的B2-NiTi同时转移到NbTi相及之前在均匀相变过程中形成的B19’-TiNi马氏体相。