Debye-Scherrer Rings Research Articles

Extended Caking Method for Strain Analysis of Polycrystalline Diffraction Debye–Scherrer Rings

Extended Caking Method for Strain Analysis of Polycrystalline Diffraction Debye–Scherrer Rings

Exploring annealing-triggered phase transformation, photoluminescence quenching, and synergistic effects of Co-doped TiO2 nanoparticles

This study investigates the influence of defects on the electronic, optical, and magnetic properties of tetragonal titanium dioxide (TiO2) and its cobalt-doped variant, Ti0.95Co0.05O2. The research findings of diffraction studies confirms the formation of phases such as anatase, rutile, and their combination within TiO2 nano-structures following annealing. The Debye-Scherrer's rings observed in the selected area electron diffraction patterns and transmission electron microscopy images showed an aggregate of randomly oriented nano-structures. Additionally, elemental analysis confirms the presence of Ti and O as primary constituents. The detailed analysis using microscopy and spectroscopy study identified a high-spin D2h state in Co2+, indicative of lattice defects across the TiO2 nano-structures. A blue shifting in the photoluminescence band gap emission peaks suggested the presence of oxygen vacancy defects in the doped nano-structures. Notably, the increased surface defects and reduced catalyst size promote rapid migration of electron-hole pairs to reaction sites i.e.; on the surface, thereby reducing recombination rates. Ultimately, the study concludes that anatase TiO2, due to its exceptional catalytic performance, is more favourable for applications in photo-catalysis and spintronics than its rutile or mixed-phase counterparts.

Multimethod cross-sectional characterization approaching the limits of diamond monophase multilayers

Chemical vapour deposited diamond draws significant scientific interest due to its wide range of mechanical and functional properties, which can be easily tuned by the applied deposition conditions. Here, hot filament chemical vapour deposition was used to synthesize four monophase multilayer diamond thin films with individual layer thickness down to ∼ 300 nm. Extensive structural characterization by scanning electron microscopy and Raman spectroscopy on the cross-section confirmed the different diamond morphologies originating from the different applied process parameters of the individual sublayers, where Raman spectroscopy could give a clear distinction between nano- and microcrystalline diamond down to a layer thickness of ∼ 1 μm. Cross-sectional X-ray nanodiffraction identified exclusively the diamond crystal structure throughout the cross-section of the multilayered diamond thin films. Cross-sectional phase and FWHM analysis allowed to discriminate between the diamond morphologies down to ∼ 500 nm, thus identifying the limitations of monophase diamond multilayers. While the microcrystalline diamond sublayers all exhibit pronounced structural gradients expressed in (i) increasing intensity of the 111 Debye-Scherrer ring, (ii) ⟨110⟩ fibre texture, and periodic variations of (iii) grain size and (iv) residual stress, the nanocrystalline diamond sublayers showed no pronounced cross-sectional variations. In summary, the experimental results provide insights into the cross-sectional evolution of microstructure and residual stress and the limitations of monophase multilayered diamond thin films.

High-pressure phase transformations and lattice distortions in industrial AISI 1070 steel: Insights from Debye-Scherrer ring integration

In this study, the behavior of the industrially prominent AISI 1070 pearlitic steel under pressures up to 35 GPa was meticulously explored. Leveraging the 1D integration patterns from the Debye-Scherrer rings, we introduced a groundbreaking method to quantify dislocation densities, providing a novel lens to understand lattice distortions in such widely-used steels. At 5 GPa, the decomposition of cementite became evident, corroborated by changes in lattice parameters and dislocation densities. As the pressure neared to 10 GPa, the emergence of Hägg carbide was observed. The hallmark discovery was the phase transition from BCC to HCP around 20 GPa. This transformation bore witness to further distortions in the HCP structure with mounting pressures. Finally, molecular dynamic simulations revealed a mostly BCC to HCP transformation via an intermediary FCC phase at crystalline defects, elucidating observed orientations and phase transformation pathways.

Micromechanical properties of micro- and nanocrystalline CVD diamond thin films with gradient microstructures and stresses

Chemical vapor deposition produced diamonds attract considerable scientific and industrial interest due to their exceptional mechanical and functional properties. Here, hot filament (HF) chemical vapor deposition was used to synthesize two diamond thin films with different cross-sectional microstructure and residual stresses. Structural characterization by scanning electron microscopy, Raman spectroscopy, and cross-sectional synchrotron x-ray nanodiffraction revealed different diamond morphologies. While the microcrystalline diamond film exhibits pronounced microstructural gradients expressed by gradually increasing (i) intensities of the 111 Debye-Scherrer rings, (ii) ⟨110⟩ fiber texture sharpness, (iii) grain size, and (iv) slightly oscillating residual stress at the level of −0.5 GPa, the nanocrystalline diamond film showed no pronounced cross-sectional variation of microstructure above the nucleation zone of ∼0.5 μm and a steady stress level of 0.25 GPa. In situ micromechanical cantilever bending tests revealed highly different mechanical properties of the two films. In detail, Young's modulus of 830 ± 53 and 459 ± 53 GPa, fracture stress of 12.4 ± 0.8 and 7.8 ± 1.0 GPa, and fracture toughness values of 6.9 ± 0.4 and 3.6 ± 0.3 MPa⋅m½ were evaluated for the micro- and nanocrystalline diamond films, respectively. In summary, this study provides valuable insights into the microstructure-residual stress correlation in micro- and nanocrystalline diamond films, especially illuminating their influence on micromechanical properties.

A Unified Representation for Fundamental Equations of Various X-Ray Stress Measurement Methods

The X-ray stress measurements by the sin2ψ method, the cos α method and the XRD2 method are basically composed of the fundamental equations based on diffraction vectors and the calculation for determining X-ray stress. The fundamental equations are expressed differently, which are due to the fact that the measurement systems associated with the incident X-ray control device and the diffracted X-ray detector are different. Although the dependent variable that is the measured quantity is the same diffraction angle theta in the fundamental equations, the main independent variable is different like the tilt angle ψ in the sin2 ψ method and the central angle α, γ of the Debye-Scherrer ring in the cos α method, the XRD2 method, respectively. Therefore, the stress determination method has been devised based on each the fundamental equation. By clarifying the differences between each X-ray stress measurement method and making a relationship, a unified representation for the fundamental equations is formalized. Therefore, a comparison of each X-ray stress measurement method is expressed in the same Euler space, and a conversion method for each X-ray stress measurement method is presented.

On the Oscillating Course of dhkl−sin2ψ Plots for Plastically Deformed, Cold-Rolled Ferritic and Duplex Stainless Steel Sheets

This work deals with non-linear dhkl−sin2ψ distributions, often observed in X-ray residual stress analysis of plastically deformed metals. Two different alloys were examined: duplex stainless steel EN 1.4362 with an austenite:ferrite volume ratio of 50:50 and ferritic stainless steel EN 1.4016. By means of an in situ experiment with high-energy synchrotron X-ray diffraction, the phase-specific lattice strain response under increasing tensile deformation was analysed continuously with a sampling rate of 0.5 Hz. From Debye–Scherrer rings of nine different lattice planes {hkl}, the dhkl−sin2ψ distributions were evaluated and the phase-specific stresses were calculated. For almost all lattice planes investigated, oscillating courses in the dhkl−sin2ψ distributions were observed, already occurring below the macro yield point and increasing in amplitude within the elasto-plastic region. By comparing the loaded and the unloaded state after deformation, the contribution of crystallographic texture and plastically induced intergranular strains to these oscillations could be separated. For the given material states, only a minor influence of crystallographic texture was observed. However, a strong dependence of the non-linearities on the respective lattice plane was found. In such cases, a stress evaluation according to the sin2ψ method leads to errors, which increase significantly if only a limited ψ range is considered.

Clustering-Based Detection of Debye–Scherrer Rings

Abstract Calibration of the X-ray powder diffraction (XRPD) experimental setup is a crucial step before data reduction and analysis, and requires correctly extracting individual Debye–Scherrer rings from the 2D XRPD image. This problem is approached using a clustering-based machine learning framework, thus interpreting each ring as a cluster. This allows automatic identification of Debye–Scherrer rings without human intervention and irrespective of detector type and orientation. Various existing clustering techniques are applied to XRPD images generated from both orthogonal and nonorthogonal detectors, and the results are visually presented for images with varying inter-ring distances, diffuse scatter, and ring graininess. The accuracy of predicted clusters is quantitatively evaluated using an annotated gold standard and multiple cluster analysis criteria. These results demonstrate the superiority of density-based clustering for the detection of Debye–Scherrer rings. Moreover, the given algorithms impose no prior restrictions on detector parameters such as sample-to-detector distance, alignment of the center of diffraction pattern, or detector type and tilt, as opposed to existing automatic detection approaches.

Artifact identification in X-ray diffraction data using machine learning methods.

In situ synchrotron high-energy X-ray powder diffraction (XRD) is highly utilized by researchers to analyze the crystallographic structures of materials in functional devices (e.g. battery materials) or in complex sample environments (e.g. diamond anvil cells or syntheses reactors). An atomic structure of a material can be identified by its diffraction pattern along with a detailed analysis of the Rietveld refinement which yields rich information on the structure and the material, such as crystallite size, microstrain and defects. For in situ experiments, a series of XRD images is usually collected on the same sample under different conditions (e.g. adiabatic conditions) yielding different states of matter, or is simply collected continuously as a function of time to track the change of a sample during a chemical or physical process. In situ experiments are usually performed with area detectors and collect images composed of diffraction patterns. For an ideal powder, the diffraction pattern should be a series of concentric Debye-Scherrer rings with evenly distributed intensities in each ring. For a realistic sample, one may observe different characteristics other than the typical ring pattern, such as textures or preferred orientations and single-crystal diffraction spots. Textures or preferred orientations usually have several parts of a ring that are more intense than the rest, whereas single-crystal diffraction spots are localized intense spots owing to diffraction of large crystals, typically >10 µm. In this work, an investigation of machine learning methods is presented for fast and reliable identification and separation of the single-crystal diffraction spots in XRD images. The exclusion of artifacts during an XRD image integration process allows a precise analysis of the powder diffraction rings of interest. When it is trained with small subsets of highly diverse datasets, the gradient boosting method can consistently produce high-accuracy results. The method dramatically decreases the amount of time spent identifying and separating single-crystal diffraction spots in comparison with the conventional method.

Investigation of Surface Residual Stress for Medium Carbon Steel Quenched by YAG Laser with Extended Cycloidal Motion

This study investigated the surface residual stress for AISI 1045 steel quenched by a YAG laser. A coaxial laser spindle was installed on a CNC machine for the experiment. The laser motion was arranged to follow the path of an extended cycloid which widened the quenching area on the steel surface. Both the temperature distribution and the residual stresses were measured by thermocouples and a portable X-ray diffractometer, respectively. When the temperature distribution was cooled down near the value of the room temperature, the residual stresses were then measured after the laser quenching process. The diffractometer used a single exposure of X-ray with a two-dimensional detector to calculate the Debye–Scherrer ring (D-S ring) for the determination of the normal and shear stresses. Different laser powers were exploited for the measurement of residual stresses, including 500, 600, 700, and 900 watts. In addition to the experiment, an analytic model for the investigation of residual stresses was built by the finite element analysis for which MSC Marc was used. The assumption for the FEA was that the laser spot had a circular shape of uniform energy distribution and the thermal–elastic–plastic model was applied to the simulation for the laser quenching process. The analytic and experimental results for the surface residual stresses had excellent consistency with a maximum difference of 10.5% from the normal stresses. The numerical results for the residual stresses also revealed that the normal stresses were compressive for the laser-quenching treatment and the shear stress could be neglected compared to the normal stress.

Quantifying Dynamic Signal Spread in Real-Time High-Energy X-ray Diffraction

Measured intensity in high-energy monochromatic X-ray diffraction (HEXD) experiments provides information regarding the microstructure of the crystalline material under study. The location of intensity on an areal detector is determined by the lattice spacing and orientation of crystals so that changes in the heterogeneity of these quantities are reflected in the spreading of diffraction peaks over time. High temporal resolution of such dynamics can now be experimentally observed using technologies such as the mixed-mode pixel array detector (MM-PAD) which facilitates in situ dynamic HEXD experiments to study plasticity and its underlying mechanisms. In this paper, we define and demonstrate a feature computed directly from such diffraction time series data quantifying signal spread in a manner that is correlated with plastic deformation of the sample. A distinguishing characteristic of the analysis is the capability to describe the evolution from the distinct diffraction peaks of an undeformed alloy sample through to the non-uniform Debye–Scherrer rings developed upon significant plastic deformation. We build on our previous work modeling data using an overcomplete dictionary by treating temporal measurements jointly to improve signal spread recovery. We demonstrate our approach in simulations and on experimental HEXD measurements captured using the MM-PAD. Our method for characterizing the temporal evolution of signal spread is shown to provide an informative means of data analysis that adds to the capabilities of existing methods. Our work draws on ideas from convolutional sparse coding and requires solving a coupled convex optimization problem based on the alternating direction method of multipliers.

The Debye–Scherrer technique – rapid detection for applications

Abstract The Debye–Scherrer (DS) technique is a common technique for determining spacings in atomic layers by X-ray diffraction. The spacings of the atomic layers are proportional to the macroscopic stress in the radiated area. When a crystalline powder is irradiated with X-rays, the diffracted X-rays produce a ring that photographic films detect. Afterward, the film is developed to reveal the rings. Earlier, this procedure took lots of time. With upcoming multiple wavelength anomalous dispersion-detectors, a very sensitive area detector, DS rings can be detected and analyzed in minutes. This allows for the rapid determination of residual stresses prior to inspection in a production environment. Additional information from the intensity distribution within the ring can be obtained. A description of the new technique is given.

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Technology development for in-situ measurement of residual stress in arc welded joints of MDN 250 by portable Cosα X-ray diffraction method

Residual stresses are inherent stresses that exist in engineering components even though no external load is applied. They are caused by the non-uniform volumetric shift of the metallic component during manufacturing processes. Welding is a key manufacturing technique that has a substantial impact on the economy since it is required for the production of a diverse variety of products used in the engineering sector. The residual stress primarily affects the stability, durability and performance of the welded joints. Hence its determination is of utmost importance. X-ray diffraction (XRD) is the most commonly used method for residual stress analysis. There are mainly two approaches for measuring residual stress using XRD; one is the sin2ψ method and the other is the cosα method. The residual stress measurements using the cosα method are handy, quick and convenient compared to the sin2ψ method. This method is well suited for welded joints, as it provides flexibility for testing immediately after the welding operation. Apart from residual stress measurements, the cosα method also gives valuable insights in the form of Debye-Scherrer (DS) rings and full width at half maximum. The present study focuses on the development of a novel technique that not only enables residual stress measurement but also provides a quantitative estimation of hardness and qualitative estimation of grain size without performing metallurgical or mechanical characterization. The material used for the present study is an arc-welded joint of MDN 250 grade maraging steel. The residual stress results show a compressive profile throughout the weldment, with a maximum value of compressive residual stress of 428 MPa at the fusion zone.

Ultrafast lattice dynamics and electron-phonon coupling in platinum extracted with a global fitting approach for time-resolved polycrystalline diffraction data.

Quantitative knowledge of electron–phonon coupling is important for many applications as well as for the fundamental understanding of nonequilibrium relaxation processes. Time-resolved diffraction provides direct access to this knowledge through its sensitivity to laser-induced lattice dynamics. Here, we present an approach for analyzing time-resolved polycrystalline diffraction data. A two-step routine is used to minimize the number of time-dependent fit parameters. The lattice dynamics are extracted by finding the best fit to the full transient diffraction pattern rather than by analyzing transient changes of individual Debye–Scherrer rings. We apply this approach to platinum, an important component of novel photocatalytic and spintronic applications, for which a large variation of literature values exists for the electron–phonon coupling parameter . Based on the extracted evolution of the atomic mean squared displacement and using a two-temperature model, we obtain (statistical error). We find that at least up to an absorbed energy density of 124 J/cm3, is not fluence-dependent. Our results for the lattice dynamics of platinum provide insights into electron–phonon coupling and phonon thermalization and constitute a basis for quantitative descriptions of platinum-based heterostructures in nonequilibrium conditions.

X-ray diffraction data from shock-compressed copper: Some consequences of metallurgical texture

We report the measurements of in situ Debye–Scherrer x-ray diffraction from copper foils shock compressed at the Orion laser facility to pressure in the range of 10–40 GPa. Our objective was to record distortion (variation of scattering angle at peak intensity, 2θ, with azimuthal position, φ, around the diffraction ring) of the Debye–Scherrer rings. We intended to measure the anisotropy of elastic strain and infer the effective strength of copper at a high strain rate. However, our measured diffraction data from all crystallographic reflection planes considered together are not consistent with a simple model that assumes homogeneous elastic strain. Consideration of both the β-fiber metallurgical texture of the rolled copper foil that we used as the sample material and the measured diffraction linewidths provides an empirical understanding of the data. We extend our understanding by using a Taylor-type, single-crystal plasticity model in which the total strain of each grain is assumed to be identical to that of the whole sample. This model reproduces many features of our experimental data and points to the importance of accounting for the plastic anisotropy of single-crystal grains, which can, in turn, lead to inter-grain elastic strain inhomogeneity and complex distortions of the diffraction rings.

Extending the Stability Field of Polymeric Carbon Dioxide Phase V beyond the Earth's Geotherm.

We present a study on the phase stability of dense carbon dioxide (CO_{2}) at extreme pressure-temperature conditions, up to 6200K within the pressure range 37±9 to 106±17 GPa. The investigations of high-pressure high-temperature insitu x-ray diffraction patterns recorded from laser-heated CO_{2}, as densified in diamond-anvil cells, consistently reproduced the exclusive formation of polymeric tetragonal CO_{2}-V at any condition achieved in repetitive laser-heating cycles. Using well-considered experimental arrangements, which prevent reactions with metal components of the pressure cells, annealing through laser heating was extended individually up to approximately 40min per cycle in order to keep track of upcoming instabilities and changes with time. The results clearly exclude any decomposition of CO_{2}-V into the elements as previously suggested. Alterations of the Bragg peak distribution on Debye-Scherrer rings indicate grain coarsening at temperatures >4000 K, giving a glimpse of the possible extension of the stability of the polymeric solid phase.

Experimental investigations of effect of tempering on residual stresses developed during the turning operation

The Cos α method has emerges as new technique for measurement of the residual stresses using whole Debye-Scherrer ring recorded on two dimensional imaging plates (IPs) with the help of X-ray residual stress measurement system μ-X360 Ver. 2. 3. 0. 1. Considering with more accountability of the tempering treatment process for decreasing or eliminating the residual stresses, the effect of tempering is monitored experimentally. The main objectives of this paper is to predict the residual stresses distribution, and surface roughness of the machined samples (with and without tempered) on CNC lathe at the same process parameters (speed, feed and depth of cut) using tungsten carbide tool. Surface residual stresses of five turned specimen with and without tempered have been measured. The residual stress graphs, FWHM (full width at half maximum) graphs and Debye –scherrer rings, and surface roughness of all samples have been obtained and critically studied. The residual stress and surface roughness were found minimum in sample tempered at 450°C. The min and max peak values were found as 149 k and 175 k for samples tempered at 450°C and untempered respectively. The average surface roughness (Ra = 2.06, Rq = 10.4 and Rz = 2.45) and(Ra = 3.65,Rq = 16.9 and Rz = 4.27) were seen in sample tempered at 450°C and untempered respectively. The results obtained from the present experiment, literature review and the theoretical study validate the present work and method in strong confirmation and bear a good agreement among them.

In Situ Observation of Crystal Grain Orientation During Scuffing Process of Steel Surface Using Synchrotron X-ray Diffraction

Scuffing is a catastrophic failure that causes significant surface damages such as plastic flow and welding with a marked increase in friction, wear, temperature and noise. In this study, variations in the crystal grain structure of a steel surface was analysed in situ during the scuffing process using a synchrotron X-ray diffraction system, combined with a visible camera and a near-infrared thermometer. The in situ observation system was synchronously operated to capture a contact area between a rotating sapphire ring and a stationary bearing steel pin. The Debye–Scherrer ring diffracted from the contact area was captured by a two-dimensional detector. The scuffing behaviour could be classified as either micro scuffing or macro scuffing. During the micro scuffing period, plastic flow occurred intermittently with a significant temperature rise of approximately 1000 °C. During the macro scuffing period, heat was continuously generated over the contact area. When plastic flow occurred, the captured Debye–Scherrer ring indicated the orientation of crystal grains as well as a phase transformation from martensite to austenite. This study constitutes the first in-situ observation of the behaviour of crystal grains in the dynamic recrystallisation process occurring during the scuffing process.

Direct observations of shock-induced melting in a porous solid using time-resolved x-ray diffraction

In this work we provide direct evidence of shock-induced melting and associated kinetics in a porous solid (aluminum powder) using time-resolved x-ray diffraction. Unambiguous evidence of melting in 50% porous aluminum (Al) powder samples, shocked to peak pressures between $\ensuremath{\sim}13\text{\ensuremath{-}}19\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, was provided by the broadening of the Debye-Scherrer ring corresponding to the (111) peak. Shocked Al powder did not melt completely in any of our experiments within the durations of measurement. Incomplete (partial) melting of the powder, even after several hundreds of nanoseconds of shock loading, provides insights into thermal transport with Al powder particles under high-pressure dynamic loading. Such insights are quite valuable for developing well-constrained melting models and thermodynamic equations of state for porous Al and other porous solids relevant to planetary and materials science.