2D X-ray Diffraction Patterns Research Articles

Synchrotron Micro-X-ray Diffraction in Transmission Geometry: A New Approach to Study Polychrome Stratigraphies in Cultural Heritage

In cultural heritage, paint stratigraphies are complex systems typically consisting of various paint layers with fine crystalline phases mixed with coarse pigment and filler grains. This complexity poses significant challenges for X-ray diffraction (XRD) analysis. In this work, we employed synchrotron radiation micro-X-ray diffraction in transmission geometry (SR-µTXRD) with linear mapping to develop a novel approach for studying the crystalline phases (pigments and fillers) in mock-up paint stratigraphies. A targeted approach was followed for qualitative, quantitative, and microstructural analysis, combining signals from micrometric crystallites and coarse single crystals as well as from randomly oriented and iso-oriented crystalline phases. This allows for identifying, localizing, and quantifying these phases even in low fractions and distinguishes the same phases across different layers with varying grain sizes or spatial orientations. Critical analysis of 2D XRD patterns, coupled with full-profile fitting performed by the Rietveld method, provides insights into material preparation (e.g., grinding), painting technique (e.g., color palette, use of fillers, brushing), and crystallo-chemical modifications over time. This analytical approach, integrating spatially resolved investigation with high-quality phase characterization, enhances the potential of specific XRD methodologies for a 2D investigation of multi-phase materials in cultural heritage, even without dedicated micro-mapping techniques.

Exploring 2D X-ray diffraction phase fraction analysis with convolutional neural networks: Insights from kinematic-diffraction simulations

Deep-learning models are effective for analyzing the complex information in 2D X-ray diffraction (XRD) patterns. Accurately collecting parameters of the material sample is crucial during model training, significantly impacting model performance. In this study, we employ a kinematic-diffraction simulator to generate simulated 2D XRD patterns for Ti–6Al–4V alloy, allowing precise control of sample parameters. These simulated patterns are used to train convolutional neural networks, predicting β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upbeta$$\\end{document}-phase volume fractions. The training data set consists exclusively of 2D XRD patterns with pure α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upalpha$$\\end{document}- or pure β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upbeta$$\\end{document}-phase, while the testing set incorporates patterns with intermediate phase volume fraction. In particular, we investigate how the architectures of the model influence prediction reliability and computational performance. Experimental results reveal that, with appropriate training, the convolutional neural network accurately detects intermediate phase volume fractions even trained with only pure-phase patterns, achieving a mean square error accuracy of 9.4×10-4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.4 \ imes 10^{-4}$$\\end{document}.Graphical abstract

In-Situ Investigation of the Oxidation Behaviour of Chemical Vapour Deposited Zr(C,N) Hard Coatings Using Synchrotron X-ray Diffraction

The oxidation behaviour of chemical vapour deposited ZrN, ZrC and ZrCN coatings was investigated using in-situ synchrotron X-ray diffraction (XRD). To obtain a precise analysis of the temperature–dependent phase evolution during oxidation, coating powders were annealed in air between 100 °C and 1000 °C. Simultaneously, 2D XRD patterns were recorded in ~2 °C increments, which were subsequently evaluated using parametric Rietveld refinement. The results were correlated with differential scanning calorimetry and thermogravimetric analysis measurements, to further illuminate the oxidation mechanism of each coating system. ZrCN exhibited the highest oxidation onset temperature, followed by ZrC and ZrN. Furthermore, ZrCN was completely oxidised at a temperature of ~720 °C, which was ~50–70 °C higher than for ZrN and ZrC. The in-situ experiments revealed a similar oxidation sequence for all three samples: first, tetragonal and/or cubic (c/t)–ZrO2 is formed, which subsequently transforms into the more stable monoclinic (m)–ZrO2 phase. ZrCN and ZrC showed a higher c/t–ZrO2 fraction than the ZrN sample at 1000 °C. Furthermore, ex-situ Raman and XRD investigations of the oxidised samples revealed the ongoing c/t–ZrO2 → m–ZrO2 phase transformation during cooling.

Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams

Summary Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.

Polar transformation of 2D X-ray diffraction patterns and the experimental validation of the hDIC technique

Deformation analysis in engineering materials and components is a subject of ongoing enquiry due to its importance for obtaining reliable prediction of strength and durability of structures and assemblies. Whilst optical methods deliver information about surface displacements, X-ray scattering methods have the capability to provide efficient assessment of crystal lattice distortion in the bulk of the component. The height digital image correlation (hDIC) technique is an alternative to conventional digital image correlation that uses the out-of-plane surface height variations for the identification of triaxial deformations. In this study, the hDIC technique was used for the determination of displacements in an aluminium specimen after 3-point bending process that creates a complex deformation state that includes both axial displacements and rotations. The surface of the specimen was prepared for the analysis by electric discharge machining (EDM) technique that has minimal effect on material properties and produces random height profile well-suited for the aim of this study. Surface height variations were measured using deep focus microscopy and used instead of pixel intensity for correlation in the DIC process. The distribution of total of elastic and plastic strains were also calculated by the evolutionary eigenstrain model using 2D X-ray diffraction patterns processed according to the polar transformation method. The agreement between hDIC and polar X-Ray diffraction analyses allowed reliable cross-validation between these two techniques.

In-situ investigation of the oxidation behavior of metastable CVD-Ti1-xAlxN using a novel combination of synchrotron radiation XRD and DSC

Ti1-xAlxN hard coatings deposited by chemical vapor deposition (CVD) have attracted much attention recently due to their extraordinary nanolamellar microstructure and outstanding performance observed in metal cutting operations. Several published reports suggest further that CVD-Ti1-xAlxN exhibits an increased thermal stability and high temperature oxidation resistance when compared to state-of-the-art physical vapor deposited Ti1-xAlxN. However, the exact mechanisms underlying the oxidation of this coating system are not thoroughly understood yet. Thus within this work, the thermal stability and oxidation resistance of a powdered nanolamellar CVD-Ti1-xAlxN coating have been investigated at the synchrotron radiation facility applying a novel in-situ experimental approach. The sample was annealed in air between 100 and 1400 °C and 2D X-ray diffraction patterns were recorded simultaneously with the differential scanning calorimetric signal. The obtained diffraction data was successively analyzed using sequential Rietveld refinement, yielding the temperature-dependent phase composition. By combining this method with the differential scanning calorimetric data, it was possible to precisely track the onset and progress of chemical reactions. The results show that the different phases present in the sample oxidize individually, with the oxidation stability strongly depending on the Al-content. Further it was found that when Ti1-xAlxN spinodally decomposes in air, the formed TiN oxidizes directly after its formation while AlN retains its chemical stability. The present work provides not only a detailed insight into the thermal stability and oxidation resistance of CVD-Ti1-xAlxN but also proves the outstanding ability of the used method for analyzing metastable coatings systems.

Deducing density and strength of nanocrystalline Ta and diamond under extreme conditions from X-ray diffraction.

In situ X-ray diffraction with advanced X-ray sources offers unique opportunities for investigating materials properties under extreme conditions such as shock-wave loading. Here, Singh's theory for deducing high-pressure density and strength from two-dimensional (2D) diffraction patterns is rigorously examined with large-scale molecular dynamics simulations of isothermal compression and shock-wave compression. Two representative solids are explored: nanocrystalline Ta and diamond. Analysis of simulated 2D X-ray diffraction patterns is compared against direct molecular dynamics simulation results. Singh's method is highly accurate for density measurement (within 1%) and reasonable for strength measurement (within 10%), and can be used for such measurements on nanocrystalline and polycrystalline solids under extreme conditions (e.g. in the megabar regime).

Structure–Property Relationships in Hydrogen-Bonded Liquid Crystals

The structural impact of hydrogen-donating moieties on the liquid crystalline behavior of hydrogen-bonded assemblies (HBAs) is comprehensively investigated. Therefore, a series of phenol derivatives such as phenol, catechol (CA), resorcinol (RE), hydroquinone (HQ), pyrogallol, hydroxyhydroquinone, and phloroglucinol (PHG) were combined with alkoxyazopyridines (Ap-N) yielding 49 new HBAs, which were studied with respect to their mesomorphic properties. The present study revealed significant differences in the liquid crystalline behavior of the structurally diverse assemblies, ranging from the absence of a mesophase to smectic or nematic phases. In contrast to previous studies a comprehensive crystallographic analysis provides insight into the structure–property relationships of the assemblies and proves a correlation between the supramolecular architecture and the macroscopic properties (=liquid crystallinity). More specifically, comparison of the single crystal data with the 2D X-ray diffraction patterns ...

Synchrotron radiation study of the surface impurities at Naica gypsum crystals

The Cave of Swords was discovered in 1910 at Naica mine, Chihuahua, Mexico. Its crystals now are 0.1-0.3m long and their surface is opaque and ocher. For over 100 years these crystals continue to amaze and give us clues about their formation [1]. This work refers to the use of synchrotron radiation for phase identification on gypsum single crystals surfaces (GSCS). The experiments were performed at beamlines (BL) 11-3 and 2-3 of the Stanford Synchrotron Radiation Lightsource (SSRL). Synchrotron X-Ray micro-Fluorescence (μ-SXRF) and micro-X-ray absorption (μ-XANES) at BL 2-3, as well as Grazing Incidence X-ray Diffraction (GI-XRD) and Transmission X-ray Microscope (TXM) at BL 11-3, were employed for elemental and phase identification. For µ-SXRF spectroscopy at the Pb LIII absorption edge some region of interests were selected on each sample. In some samples Fe K-edge μ-XANES spectra were obtained. Spectra from BL 2-3 were analyzed by standard procedures of in-house software tools and using SMAK [2]. Ni, Cu, Co, V, K, Ti, Fe, Mn, Pb, Zn, Ca and S elements were identified. Hematite phase was identified by μ-XANES. All GI-XRD and TXM 2D X-ray diffraction patterns (2D-XRD) were calibrated using standard procedures developed at BL 11-3. 2D-XRD data were analyzed by ANAELU [3], Wfdiff [2] and FindIt codes. Figure shows above a TXM image, mapping where 2D-XRD patterns were recorded. Impurities in the sample increase from left to right, as was observed by direct inspection. Below, 2D-XRD patterns show at left the single crystal spots and at right the mosaic tracks of gypsum crystals. It was concluded that the crystal structure is affected by impurities. Hematite, chalcopyrite, sphalerite, cuprite, galena, and alabandite phases were determined by GI-XRD at GSCS. Acknowledgment: Stanford Synchrotron Radiation Lightsource, Harvard Museum of Natural History and CONACYT CB-183706.

In situ coupling of atomic force microscopy and sub-micrometer focused X-ray techniques

ABSTRACTA scanning force microscope for in situ nanofocused X-ray studies (SFINX) has been developed which can be installed on diffractometers at synchrotron beamlines allowing for the combination with various techniques such as coherent X-ray diffraction and fluorescence. The capabilities of this device are demonstrated on Cu nanowires and on Au islands grown on sapphire (0001). The sample topography, crystallinity, and elemental distribution of the same area are investigated by recording simultaneously an AFM image, a scanning X-ray diffraction map, and a fluorescence map. Additionally, the mechanical response of Au islands is studied by in situ indentation tests employing the AFM-tip and recording 2D X-ray diffraction patterns during mechanical loading.

Orientational Fluctuations Near the Smectic A to Smectic C Phase Transition in Two “de Vries”‐Type Liquid Crystals

On the basis of thorough analysis of 2D X-ray diffraction patterns from smectic monodomains, we examine the influence of orientational fluctuations on the weakly first-order smectic A (SmA) to smectic C (SmC) transitions in two nonchiral organosiloxane "de Vries"-type liquid crystals. We find that these materials exhibit very large molecular tilt fluctuations with magnitudes of up to 35°--thus larger than the average tilt itself. This is essential to understand the underlying molecular mechanism behind the practical absence of smectic layer contraction in these materials: in the SmA phase, the nematic order parameter is very low (molecular fluctuations correspondingly high), and the expected layer shrinkage at the SmA to SmC transition is almost fully compensated by the increase in orientational order, as the fluctuations diminish with decreasing temperature. In addition to the general tilt fluctuations, we observe intrinsic soft-mode fluctuations. They have a λ-shaped temperature dependence that peaks at the SmA-SmC transition with a maximum amplitude of about 2°.

Enantiotropic Nematics From Cross‐Like 1,2,4,5‐Tetrakis(4′‐alkyl‐4‐ethynylbiphenyl)benzenes and Their Biaxiality Studies

The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations.

Structural Changes in Both the Troponin Complex and the Thick Filament May Underlie Myofilament Length Dependent Activation

The main cellular mechanism that underlies the so-called “Frank-Starling Law of the Heart” is an increase in the responsiveness of cardiac myofilaments to activating Ca2+ at longer sarcomere lengths (SL). The structural basis of this “Length Dependent Activation” (LDA) is not known. 2D X-ray diffraction patterns were obtained using the BioCAT beamline 18ID at the Advanced Photon Source from electrically stimulated (0.2 Hz) intact, twitching papillary muscle isolated from rat hearts during a 10 ms time window in diastole just prior to electrical stimulation. Diffraction patterns were compared from muscles that were stretched to Lmax (SL= ∼2.3 μm) to those taken following a quick release to slack length (SL=∼1.9 μm). We previously reported that myosin heads moved radially inwards at longer SL suggesting that an increased radial extent of crossbridges at longer length cannot explain increased calcium sensitivity so other explanations must be sought. It is known that changes in isoform composition of the troponin complex can markedly affect calcium sensitivity but the role of troponin in the length sensing mechanism underlying LDA is not clear. Here we analyzed the meridional patterns which showed that the 3rd order troponin repeat distance, the 3rd - order troponin reflection intensity and the 2nd order myosin (“forbidden”) meridional reflection all increased significantly (P < 0.01) at Lmax as compared to slack length. Thus, stretching intact heart muscle in diastole induces changes in the structure of both the thick filaments and the thin filaments. It appears, then, that the length sensing mechanism underlying LDA must involve connections of some kind that transmit strain between the thick and thin filament that alter the structure of the troponin complex and, presumably, myofilament contractile properties. Supported by NIH HL075494 and RR08630.

Radial Motion of Myosin Heads in Isolated Intact Rat Myocardium in Diastole

The main cellular mechanism that underlies the so-called “Frank -Starling Law of the Heart” is an increase in the responsiveness of cardiac myofilaments to activating Ca2+ ions at longer sarcomere lengths (SL). The fundamental mechanism responsible for this increase in responsiveness has been elusive, despite considerable experimental scrutiny. Here we tested the hypothesis that the increase in calcium sensitivity upon increasing SL is correlated with a radially outward movement of the myosin heads during diastole. 2D x-ray diffraction patterns were obtained from electrically stimulated intact, twitching papillary muscle isolated from rat hearts during a 10 ms time window in diastole just prior to electrical stimulation. A range of sarcomere lengths was compared either at Lmax (SL= ∼2.3 µm) or following a quick release to slack length (SL=∼1.9µm). The relative position of myosin heads was first assessed by the I11/I10 equatorial intensity ratio. To our surprise, I 11/I10 was negatively correlated with SL, i.e. I11/I10 was less at Lmax vs. slack length. A more direct measure of the radial position of the myosin heads can be estimated from the position of the first maxima on the unsampled myosin layer lines, which are prominent in diastole. The intensity maxima, when examined pair-wise, moved outwards to a maximum of 5-6% for a 0.4µm change in SL indicating that the heads must be moving radially outward at slack length. Our data suggest that myofilament length dependent activation does not derive from a radial extension of the myosin heads at the long SL and must, therefore, involve some other mechanism. Supported by NIH HL75494 and RR08630.

Force-Generating Cross-Bridges during Ramp-Shaped Releases: Evidence for a New Structural State

Mechanical and two-dimensional (2D) x-ray diffraction studies suggest that during isometric steady-state contraction, strongly bound cross-bridges mostly occupy early states in the power stroke, whereas rigor or rigor-like cross-bridges could not be detected. However, it remained unclear whether cross-bridges accumulate, at least transiently, in rigor or rigor-like states in response to rapid-length releases. We addressed this question using time-resolved recording of 2D x-ray diffraction patterns of permeabilized fibers from rabbit psoas muscles during isometric contraction and when small, ramp-shaped length-releases were applied to these fibers. This maneuver allows a transient accumulation of cross-bridges in states near the end of their power stroke. By lowering the temperature to 5°C, force transients were slowed sufficiently to record diffraction patterns in several 2–4-ms time frames before and during such releases, using the RAPID detector (Refined ADC Per Input Detector) at beam line ID02 of the European Synchrotron Radiation Facility (Grenoble, France). The same sequence of frames was recorded in relaxation and rigor. Comparisons of 2D patterns recorded during isometric contraction, with patterns recorded at different [MgATP γS] and at 1°C, showed that changes in intensity profiles along the first and sixth actin layer lines (ALL1 and ALL6, respectively) allowed for discernment of the formation of rigor or rigor-like cross-bridges. During ramp-shaped releases of activated fibers, intensity profiles along ALL1 and ALL6 did not reveal evidence for the accumulation of rigor-like cross-bridges. Instead, changes in the ALL6-profile suggest that during ramp-shaped releases, cross-bridges transiently accumulate in a structural state that, to our knowledge, was not previously seen, but that could well be a strongly bound state with the light-chain binding domain in a conformation between a near prepower-stroke (isometric) orientation and the orientation in rigor.

Surface and volume effects in rapidly quenched Fe-Mo-Cu-B system

We have investigated special effect related to the crystalline phases at the surface layers of as-quenched FeMoCuB ribbons prepared by planar flow casting using several experimental methods. These effects contradict the usual pattern of surface crystallinity formation due to insufficient quenching rates or glass forming ability. Influence of substitution of Fe by Co and varying B in the basic system (Fe1-xCox)79-yMo8Cu1B12+y on these effects as well as influence of flux-melting prior to rapid quenching were analyzed. Disappearance of surface crystallinity with simultaneous addition of Co and B was observed. Similar effect was obtained also by using flux-melting of the master alloy prior to rapid quenching. Possible micromechanisms leading to this behavior were discussed. The evolution of surface structure was monitored in detail during in-situ linear heating in the temperature range 300K-1080K via 2D X-ray diffraction patterns using synchrotron radiation.

The Effect of Thin Filament Activation on the Attachment of Weak Binding Cross-Bridges: A Two-Dimensional X-Ray Diffraction Study on Single Muscle Fibers

To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATP γS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because it had been proposed from solution studies that reducing ionic strength below 50 mM also induces activation of the thin filament. For this project a novel preparation had to be established that allows recording of 2D x-ray diffraction patterns from single muscle fibers instead of natural fiber bundles. This was required to minimize substrate depletion or product accumulation within the fibers. When the calcium concentration was raised, the diffraction patterns recorded with MgATP γS revealed small changes in meridional reflections and layer line intensities that could be attributed in part to the effects of calcium binding to the thin filament (increase in I 380, decrease in first actin layer line intensity, increase in I 59) and in part to small structural changes of weakly attached cross-bridges (e.g., increase in I 143 and I 72). Calcium-induced small-scale structural rearrangements of cross-bridges weakly attached to actin in the presence of MgATP γS are consistent with our previous observation of reduced rate constants for attachment and detachment of cross-bridges with MgATP γS at high calcium. Yet, no evidence was found that weakly attached cross-bridges change their mode of attachment toward a stereospecific conformation when the actin filament is activated by adding calcium. Similarly, reducing ionic strength to less than 50 mM does not induce a transition from nonstereospecific to stereospecific attachment.

Molecular movements in contracting muscle: Towards “muscle - the movie”

The recent publication of the crystal structures of G-actin and of myosin subfragment-1, together with analysis of a time-resolved series of well sampled low-angle 2D X-ray diffraction patterns from bony fish muscle permits the study of the molecular movements in muscle that are associated with generation and regulation of contractile force. Here it is shown that even though low-angle (i.e. low resolution) X-ray diffraction patterns are being used, these patterns are sensitive, for example, to sub-domain movements of as little as 3 Å or 4° within the actin monomers of actin filaments. Actin filament diffraction patterns from whole muscle are being used to define actin domain and tropomyosin movements involved in regulation. Myosin and actin filament diffraction patterns are being used together to start to show how the complete “quasi-crystalline” unit cell in the bony fish muscle A-band can be modelled as a series of time-slices through a typical tetanic contraction of the muscle. In this way, the time sequence of images can be used to create “muscle - the movie”.