基于蒙特卡罗模拟的透射式XRD背景的定量分析

XRD背景主要来源于空气、装置和样品中光子的散射,XRD分析需准确扣除背景,常用的扣背景方法具有一定的局限。蒙特卡罗模拟可实现光子的甄别与统计,因此可将其用于XRD背景来源的定量分析。相干散射的模拟中需考虑物质的Form Factor,这可由Baró等的拟合式、独立原子模型或德拜公式给出;在20 keV能量及透射几何模式下,通过对骨、尼龙、水等物质的XRD模拟,对探测器中光子来源进行了区分和统计。结果表明,德拜公式计算的空气背景大于独立原子模型;空气散射在小角度时背景占比大,随散射角的增加从100%减小至40%以下,而样品中康普顿散射的计数占比则从0增大至60%以上。该方法可对不同样品组成以及复杂装置结构的XRD背景进行定量分析。

偏光显微镜和XRD在南非Postmasburg锰矿定性分析中的应用

根据南非Postmasburg锰矿田BIF型矿体中的矿石分带和品位差异,识别出了富锰型矿石、砾岩型矿石以及铁质岩型矿石。为确定各类矿石的矿物成分,了解矿石类型与其矿物成分间的对应关系,以各类矿石为研究对象,对其中的矿物成分进行了研究。采用偏光显微鉴定技术结合X射线衍射物相分析,基于矿物偏光特征和特征衍射峰,对矿石中的矿物进行了定性。结果表明,富锰型矿石中的主量矿物为方铁锰矿和褐锰矿;砾岩型矿石中金属矿物几乎全为赤铁矿,黏土矿物以钠珠云母为主;含砾铁质岩中黏土矿物居多,以白云母为主,金属矿物多为赤铁矿。由此可见,偏光显微鉴定和XRD具有良好的一致性和互补性,尤其是对厚层的沉积型矿床,岩性和岩相具有一定变化序列的情况下,更适合二者相结合进行精确定性分析。

基于XRD内标法测定LiF-BeF_2熔盐体系中UF_3含量

在氟化物熔盐相直接将UF6中转化为UF_4是熔盐堆燃料盐的合成及重构的候选工艺之一。其中,UF_(3)是该工艺过程的重要中间产物,其含量是开展工艺研究的关键参数之一。本文采用X射线衍射(X-ray Diffraction,XRD)内标法测量氟化物体系中的UF_(3)含量,分析了不同组分的固态熔盐样品,建立了UF_(3)含量的测量分析方法。首先以刚玉(α-Al_(2)O_(3))为内标,获得了UF_(3)在1.00~10.00 wt%含量范围时,LiF-BeF_(2)-UF_(3)熔盐的XRD峰高度内标曲线(R=0.986)和峰面积内标曲线(R=0.995)。然后应用这两条内标曲线测量已知含量的LiUF_(5)和UF_(3)固体混合样品,结果表明峰面积内标曲线具有更好的准确度,测量相对误差不大于8.7%。最后分别对快速冷却的LiF-BeF_(2)-UF_(3)固态熔盐样品和自然冷却的LiF-BeF_(2)-UF_(3)-LiUF_(5)固态熔盐样品进行测量,测量结果的相对误差不大于5.4%。以上结果表明:本文建立的XRD内标法可以用于混合氟盐样品的UF_(3)分析,并具有较好的测量精度和重复性。

Microstructures and micromechanical behaviors of high -entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: A review

High-entropy alloys(HEAs)possess outstanding features such as corrosion resistance,irradiation resistance,and good mechan-ical properties.A few HEAs have found applications in the fields of aerospace and defense.Extensive studies on the deformation mech-anisms of HEAs can guide microstructure control and toughness design,which is vital for understanding and studying state-of-the-art structural materials.Synchrotron X-ray and neutron diffraction are necessary techniques for materials science research,especially for in situ coupling of physical/chemical fields and for resolving macro/microcrystallographic information on materials.Recently,several re-searchers have applied synchrotron X-ray and neutron diffraction methods to study the deformation mechanisms,phase transformations,stress behaviors,and in situ processes of HEAs,such as variable-temperature,high-pressure,and hydrogenation processes.In this review,the principles and development of synchrotron X-ray and neutron diffraction are presented,and their applications in the deformation mechanisms of HEAs are discussed.The factors that influence the deformation mechanisms of HEAs are also outlined.This review fo-cuses on the microstructures and micromechanical behaviors during tension/compression or creep/fatigue deformation and the application of synchrotron X-ray and neutron diffraction methods to the characterization of dislocations,stacking faults,twins,phases,and intergrain/interphase stress changes.Perspectives on future developments of synchrotron X-ray and neutron diffraction and on research directions on the deformation mechanisms of novel metals are discussed.

Direct visualization of laser-driven dynamic fragmentation in tin by in situ x-ray diffraction

We present a novel method for investigating laser-driven dynamic fragmentation in tin using in situ X-ray diffraction.Our experimental results demonstrate the feasibility of the method for simultaneously identifying the phase and temperature of fragments through analysis of the diffraction pattern.Surprisingly,we observe a deviation from the widely accepted isentropic release assumption,with the temperature of the fragments being found to be more than 100 K higher than expected,owing to the release of plastic work during dynamic fragmentation.Our findings are further verified through extensive large-scale molecular dynamics simulations,in which strain energies are found to be transferred into thermal energies during the nucleation and growth of voids,leading to an increase in temperature.Our findings thus provide crucial insights into the impact-driven dynamic fragmentation phenomenon and reveal the significant influence of plastic work on material response during shock release.

Intensity correlation properties of x-ray beams split with Laue diffraction

Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we investigate the intensity correlation between the split x-ray beams by Laue diffraction of stress-free crystal. The analysis based on the dynamical theory of x-ray diffraction indicates that the spatial resolution of diffraction image and transmission image are reduced due to the position shift of the exit beam. In the experimental setup, a stress-free crystal with a thickness of hundredmicrometers-level is used for beam splitting. The crystal is in a non-dispersive configuration equipped with a double-crystal monochromator to ensure that the dimension of the diffraction beam and transmission beam are consistent. A correlation coefficient of 0.92 is achieved experimentally and the high signal-to-noise ratio of the x-ray ghost imaging is anticipated.Results of this paper demonstrate that the developed beam splitter of Laue crystal has the potential in the efficient data acquisition of x-ray ghost imaging.

Dispersion Relations in Diffraction in Time

In agreement with Titchmarsh’s theorem, we prove that dispersion relations are just the Fourier-transform of the identity, g(x′)=±Sgn(x′)g(x′), which defines the property of being a truncated functions at the origin. On the other hand, we prove that the wave-function of a generalized diffraction in time problem is just the Fourier-transform of a truncated function. Consequently, the existence of dispersion relations for the diffraction in time wave-function follows. We derive these explicit dispersion relations.

Surface diffraction beamline at the SSRF

BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5×10^(12) photons/s at 10 keV and a beam size of 160µm×80µm at the sample site.It is dedicated to studying surfaces(solid-vacuum,solid-gas)and interfaces(solid-solid,solid-liquid,and liquid-liquid)in nanoscience,condensed matter,and soft matter systems using various surface scattering techniques over an energy range of 4.8-28 keV with transmission and reflection modes.Moreover,BL02U2 has a high energy resolution,high angular resolution,and low beam divergence,which can provide excellent properties for X-ray diffraction experiments,such as grazing incident X-ray diffraction,X-ray reflectivity,crystal truncation rods,and liquid X-ray scattering.Diversity of in situ environments can also be provided for the samples studied.This paper describes the setup of the new beamline and its applications in various fields.

Analytical Method for the Wave Diffraction of Asymmetrically Arranged Breakwaters

The layout forms of several breakwater structures can be generalized as asymmetrical arrangements in actual engineering.However,the problem of wave diffraction around asymmetrically arranged breakwaters has not been adequately investigated.In this study,we propose an analytical method of wave diffraction for regular waves passing through asymmetrically arranged breakwaters,and we use the Nyström method to obtain the analytical solution numerically.We compared the results of this method with those of previous analytical solutions and with numerical results to demonstrate the validity of our approach.We also provided diffraction coefficient diagrams of breakwaters with different layout forms.Moreover,we described the analytical expression for the problem of diffraction through long-wave incident breakwaters and presented an analysis of the relationship between the diffraction coefficients and the widths of breakwater gates.The analytical method presented in this study contributes to the limited literature on the theory of wave diffraction through asymmetrically arranged breakwaters.

Direct observation of shock-induced phase transformation in polycrystalline iron via in situ x-ray diffraction

Phase transition of polycrystalline iron compressed along the Hugoniot is studied by combining laser-driven shock with in situ x-ray diffraction technique.It is suggested that polycrystalline iron changes from an initial body-centered cubic structure to a hexagonal close-packed structure with increasing pressure(i.e.,a phase transition fromαtoε).The relationship between density and pressure for polycrystalline iron obtained from the present experiments is found to be in good agreement with the gas-gun Hugoniot data.Our results show that experiments with samples at lower temperatures under static loading,such as in a diamond anvil cell,lead to higher densities measured than those found under dynamic loading.This means that extrapolating results of static experiments may not predict the dynamic responses of materials accurately.In addition,neither the face-centered cubic structure seen in previous molecular-dynamics simulations or twophase coexistence are found within our experimental pressure range.

The Crystal Structure Study of CaSrFe0.75Co0.75Mn0.5O6−δ by Neutron Diffraction

The crystal structure of CaSrFe0.75Co0.75Mn0.5O6−δ is investigated through neutron diffraction techniques in this study. The material is synthesized using a solid-state synthesis method at a temperature of 1200˚C. Neutron diffraction data is subjected to Rietveld refinement, and a comparative analysis with X-ray diffraction (XRD) data is performed to unravel the structural details of the material. The findings reveal that the synthesized material exhibits a cubic crystal structure with a Pm-3m phase. The neutron diffraction results offer valuable insights into the arrangement of atoms within the lattice, contributing to a comprehensive understanding of the material’s structural properties. This research enhances our knowledge of CaSrFe0.75Co0.75Mn0.5O6−δ, with potential implications for its applications in various technological and scientific domains.

准东阜康凹陷XRD录井多层感知器法储层物性评价探索

快速准确评价储层物性是试油选层及压裂定段的关键。为研究准东阜康凹陷二叠系上乌尔禾组优质储层分布层段,探索了多层感知器法在准东阜康凹陷XRD录井储层物性评价中的应用。通过收集大量的XRD录井数据,优选5种特征矿物构建多层感知器法神经网络模型,验证发现所建立的模型能够较好地拟合储层物性参数与矿物含量之间的关系。经过训练的模型在测试数据集上取得了较高的预测准确率,为快速、准确评价储层物性提供了新途径。在KT 5及F 47井应用取得了较好的评价效果,具有一定的推广应用价值。

Tailoring electron vortex beams with customizable intensity patterns by electron diffraction holography

An electron vortex beam(EVB) carrying orbital angular momentum(OAM) plays a key role in a series of fundamental scientific researches, such as chiral energy-loss spectroscopy and magnetic dichroism spectroscopy. So far, almost all the experimentally created EVBs manifest isotropic doughnut intensity patterns. Here, based on the correlation between local divergence angle of electron beam and phase gradient along azimuthal direction, we show that free electrons can be tailored to EVBs with customizable intensity patterns independent of the carried OAM. As proof-of-concept, by using computer generated hologram and designing phase masks to shape the incident free electrons in the transmission electron microscope, three structured EVBs carrying identical OAM are tailored to exhibit completely different intensity patterns. Furthermore, through the modal decomposition, we quantitatively investigate their OAM spectral distributions and reveal that structured EVBs present a superposition of a series of different eigenstates induced by the locally varied geometries. These results not only generalize the concept of EVB, but also demonstrate an extra highly controllable degree of freedom for electron beam manipulation in addition to OAM.

Numerical Study on the Effect of Gap Diffraction on the Hydrodynamic Performance of A Floating Breakwater

Two-dimensional(2D)flume experiments are useful in investigating the performances of floating breakwaters(FBs),including hydrodynamic performances,motion responses,and mooring forces.Designing a reasonable gap between the flume wall and the FBs is a critical step in 2D flume tests.However,research on the effect of the gap on the accuracy of 2D FB experimental results is scarce.To address this issue,a numerical wave tank is developed using CFD to estimate the wave-FB interaction of a moored dual-cylindrical FB,and the results are compared to experimental data from a previously published work.There is good agreement between them,indicating that the numerical model is sufficiently accurate.The numerical model is then applied to explore the effect of gap diffraction on the performance of FBs in2D experiments.It was discovered that the nondimensional gap length L_(Gap)/W_(Pool)should be smaller than 7.5%to ensure that the relative error of the transmission coefficient is smaller than 3%.The influence of the gap is also related to the entering wave properties,such as the wave height and period.

Diffraction deep neural network-based classification for vector vortex beams

The vector vortex beam(VVB)has attracted significant attention due to its intrinsic diversity of information and has found great applications in both classical and quantum communications.However,a VVB is unavoidably affected by atmospheric turbulence(AT)when it propagates through the free-space optical communication environment,which results in detection errors at the receiver.In this paper,we propose a VVB classification scheme to detect VVBs with continuously changing polarization states under AT,where a diffractive deep neural network(DDNN)is designed and trained to classify the intensity distribution of the input distorted VVBs,and the horizontal direction of polarization of the input distorted beam is adopted as the feature for the classification through the DDNN.The numerical simulations and experimental results demonstrate that the proposed scheme has high accuracy in classification tasks.The energy distribution percentage remains above 95%from weak to medium AT,and the classification accuracy can remain above 95%for various strengths of turbulence.It has a faster convergence and better accuracy than that based on a convolutional neural network.

Deformation behavior of Mg-Y-Ni alloys containing different volume fraction of LPSO phase during tension and compression through in-situ synchrotron diffraction

The deformation behavior of the as-extruded Mg-Y-Ni alloys with different volume fraction of long period stacking ordered(LPSO)phase during tension and compression was investigated by in-situ synchrotron diffraction.The micro-yielding,macro-yielding,tension-compression asymmetry and strain hardening behavior of the alloys were explored by combining with deformation mechanisms.The micro-yielding is dominated by basal slip of dynamic recrystallized(DRXed)grains in tension,while it is dominated by extension twinning of non-dynamic recrystallized(non-DRXed)grains in compression.At macro-yielding,the non-DRXed grains are still elastic deformed in tension and the basal slip of DRXed grains in compression are activated.Meanwhile,the LPSO phase still retains elastic deformation,but can bear more load,so the higher the volume fraction of hard LPSO phase,the higher the tensile/compressive macro-yield strength of the alloys.Benefiting from the low volume fraction of the non-DRXed grains and the delay effect of LPSO andγphases on extension twinning,the as-extruded alloys exhibit excellent tension-compression symmetry.When the volume fraction of LPSO phase reaches∼50%,tension-compression asymmetry is reversed,which is due to the fact that the LPSO phase is stronger in compression than in tension.The tensile strain hardening behavior is dominated by dislocation slip,while the dominate mechanism for compressive strain hardening changes from twinning in theα-Mg grains to kinking of the LPSO phase with increasing volume fraction of LPSO phase.The activation of kinking leads to the constant compressive strain hardening rate of∼2500 MPa,which is significantly higher than the tensile strain hardening rate.

A Novel High Temperature Apparatus for in situ Synchrotron X-ray Diffraction Studies of Molten Salt

This study demonstrates the design and application of a novel high temperature rotatory apparatus for insitu synchrotron X-ray diffraction studies of molten salts,facilitating investigation into the interaction between various structural materials and molten salts.The apparatus enables accurate detection of every phase change during hightemperature experiments,including strong reaction processes like corrosion.Molten salts,such as chlorides or fluo⁃rides,together with the structure materials,are inserted into either quartz or boron nitride capillaries,where X-ray diffraction pattern can be continuously collected,as the samples are heated to high temperature.The replacement re⁃action,when molten ZnCl2 are etching Ti3AlC2,can be clearly observed through changes in diffraction peak intensity as well as expansion in c-axis lattice parameter of the hexagonal matrix,due to the larger atomic number and ionic ra⁃dius of Zn2+.Furthermore,we investigated the high-temperature corrosion process when GH3535 alloy is in FLiNaK molten salt,and can help to optimize its stability for potential applications in molten salt reactor.Additionally,this high temperature apparatus is fully compatible with the combined usage of X-ray diffraction and Raman technique,providing both bulk and surface structural information.This high temperature apparatus has been open to users and is extensively used at BL14B1 beamline of the Shanghai Synchrotron Radiation Facility.

Studies of XRD and FTIR on Synthesized Novel Hybrid Thin Film Made of Hydroxyapatite, Poly Vinyl Alcohol and Gelatin for Biomedical Application

With the modern advancement of treatment approaches in medical science, the application of biomaterials in tissue engineering provides a remarkable opportunity to overcome graft rejection as well as proper wound healing. In this study, novel hybrid films have been synthesized by incorporation of polyvinyl alcohol (PVA), gelatin, and gelatin with glycerin along with different concentrations of pre-prepared hydroxyapatite (HAP) by solution casting method at room temperature in a biosafety cabinet. Glutaraldehyde has been added as a crosslinker in this whole procedure. Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD) have been conducted to observe and compare the structural and chemical stability of the synthesized hybrid film properties. The FTIR results and X-Ray Diffraction analyses confirmed the chemical interactions between HAP, PVA, gelatin, and glycerin have occurred. The crystallinity of HAP also remains in all the prepared hybrid film samples that are observed in XRD. It is expected that these newly synthesized hybrid films could be a better opportunity for various sectors of tissue engineering such as skin, bone, tendon, and cartilage. These synthesized hybrid films can be suitable for wound healing covering. These studies could be a new scope for long-term drug delivery directly on wound sites in diabetic gangrene foot or burn patients as well as cartilage or joint replacement therapy.

碳化钨粉末中晶粒抑制剂固溶量XRD对标评价方法

在细颗粒氧化钨或钨粉中添加晶粒抑制剂制取含抑制剂的碳化钨粉末是制备超细硬质合金的一种方法。通常认为WC粉末中抑制剂或固溶于WC或独立存在,但由于添加量过少,难以通过检测手段判定其存在形式及固溶量。本文尝试采用对标评价的方式建立量化指标以判断粉末中晶粒抑制剂的固溶程度,评价了添加不同质量Cr及Cr、V混合晶粒抑制剂制备的细颗粒及超细颗粒WC粉末。测试结果表明,难以判定抑制剂固溶量是因为忽略了生产中出现的缺碳相及相应的固溶产物相。评价方法以W_(2)C、(W,Cr,V)_(2)C及WC为对标对象,判断固溶量;以衍射峰峰位及半高宽为对标指标,弱化其他干扰晶格常数变化因素的影响,如谱峰较少导致的晶型不确定、工艺参数或抑制剂添加导致的结晶程度变化。相同碳化工艺、抑制剂添加量1%的范围内,粉末的(W,Cr,V)_(2)C及WC的峰位均随Cr抑制剂添加量的增加而增大,(W,Cr,V)_(2)C峰面积也有逐渐增大的变化趋势。用试样粉末制备硬质合金并测量WC晶粒度,部分结果显示其趋势与量化指标相同。

FTIR和XRD在断层构造煤结构分析中的应用

为探究断层构造作用对煤化学结构特征和微晶结构特征的影响,采用傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)分析,对红庆梁矿和段王矿的原生煤及断层构造煤进行分析。结果表明,受断层构造作用影响,红庆梁、段王断层构造煤中苯环二取代、苯环四取代的含量明显大于原生煤,苯环三取代和苯环五取代的含量低于原生煤,断层构造煤中C—O—C伸缩振动、—CH_(2)反对称弯曲振动、—CH_(3)、—CH_(2)和芳环—OH含量均多于原生煤,断层构造煤中醚C—O振动、芳烃CC、—CH和OH—π含量低于原生煤。红庆梁、段王断层构造煤的芳碳率fa是原生煤的1.01和1.03倍,芳环缩合度DOC是原生煤的1.01倍和3.7倍,CH_(2)/CH_(3)值是原生煤样的0.933倍和0.94倍,芳香度I分别是原生煤样的1.01倍和1.34倍。说明断层构造作用促使官能团和脂肪链脱落,增加煤的缩聚程度,降低煤中脂肪侧链的长度,增大芳香结构含量。XRD测试结果表明,原生煤和断层构造煤具有相近的矿物组分,断层构造作用未对煤中矿物组分的类型产生明显的改变。在2θ=26°附近存在特征(002)带,表明存在少量的层状石墨结构,然而在2θ=45°附近并没有清楚地显示(100)带,说明煤中石墨结构的基面生长水平较低。红庆梁、段王断层构造煤的晶间间距d_(002)值与原生煤相比变化很小,微晶堆积高度L_(c)值分别是原生煤的0.9045倍和0.9027倍,芳香度f_(a)-XRD值分别是原生煤的1.1439倍和1.0669倍,晶体堆叠平均层数N_(ave)值分别是原生煤的0.90945倍和0.92356倍。断层构造作用减小煤的芳香层片堆砌度,增大煤的芳香度,减少了煤微晶结构单元的堆叠层数,说明断层构造促进煤中非芳香化合物向芳香化合物的转化。断层构造煤的芳香度、成熟度更高,断层构造煤的燃烧反应性弱于原生煤。