Angle-dispersive Diffraction Research Articles

Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions

ABSTRACT Understanding crystal/melt xenon (Xe) partitioning at depth is key to properly trace planetary processes using Xe isotopes. Partition coefficients measured on experimental samples recovered at room pressure (P) and temperature (T) span 6 orders of magnitude, potentially due to Xe exsolution from crystals upon quenching. We chose two in situ synchrotron X-ray methods to investigate Xe crystal/melt partitioning under high P and T up to 3 GPa and 1050°C using (1) resistive-heated diamond anvil cell with angle-dispersive diffraction and X-ray fluorescence, and (2) a new protocol using large volume press with energy-dispersive diffraction set-up. Results from both methods are consistent, and Xe is found to be compatible at depth, suggesting the continental crust could be a Xe-rich reservoir. This new protocol advances research to probe geological systems at the higher P–T conditions accessible with large volume press while maintaining homogeneous T throughout the sample.

The neutron diffraction experiments under high pressure and high temperature on FENGHUANG diffractometer at CMRR

FENGHUANG diffractometer at CMRR, a high-intensity multi-section neutron powder diffractometer, has been constructed to in situ studies of materials under high pressure high temperature conditions. With development of anvils, high pressure high temperature cell assemblies, high pressure device and alignment system, we have been realized the angle-dispersive neutron diffraction data collect at the range of achievable pressures and temperatures of 0–30 GPa and 300–1500 K, with the sample size of millimeter scale. This paper describes the technical characteristics of diffractometer and related techniques for high pressure neutron diffraction experiments, and gives some scientific examples that have been recently performed on FENGHUANG. The experience gained experiments on FENGHUANG could help promote the development of high pressure techniques on neutron scattering facilities.

High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

While the layered 122 iron arsenide superconductors are highly anisotropic, unconventional, and exhibit several forms of electronic orders that coexist or compete with superconductivity in different regions of their phase diagrams, we find in the absence of iron in the structure that the superconducting characteristics of the end member BaPd2As2 are surprisingly conventional. Here we report on complementary measurements of specific heat, magnetic susceptibility, resistivity measurements, Andreev spectroscopy, and synchrotron high pressure x-ray diffraction measurements supplemented with theoretical calculations for BaPd2As2. Its superconducting properties are completely isotropic as demonstrated by the critical fields, which do not depend on the direction of the applied field. Under the application of high pressure, Tc is linearly suppressed, which is the typical behavior of classical phonon-mediated superconductors with some additional effect of a pressure-induced decrease in the electronic density of states and the electron-phonon coupling parameters. Structural changes in the layered BaPd2As2 have been studied by means of angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 24.2 GPa we observed pressure induced lattice distortions manifesting as the discontinuity and, hence discontinuity in the Birch-Murnaghan equation of state. The bulk modulus is B0=40(6) GPa below 12 GPa and B0=142(3) GPa below 27.2 GPa.

Synthesis and recovery of bulk Fe4O5 from magnetite, Fe3O4. A member of a self-similar series of structures for the lower mantle and transition zone

AbstractA multi-anvil press was combined with monochromatic synchrotron X-ray radiation to investigate the synthesis, at high-pressure high-temperature conditions, of a recoverable bulk sample of Fe4O5, from an initial magnetite, Fe3O4, sample. Angle-dispersive diffraction patterns show that magnetite firstly breaks down, into an assemblage of hematite (Fe2O3) + Fe4O5. By increasing temperature at constant load, hematite disappears progressively by either reduction or by melting, or a combination of both. In the final product only Fe4O5 remains and, in the absence of hematite, can be kept stable and be recovered at ambient conditions. Refinement of the diffraction patterns at standard conditions demonstrate that Fe4O5 has the Sr2Tl2O5-type-structure with space group Cmcm and a = 2.8964(2) Å, b = 9.8225(6) Åand c = 12.5808(7) Å. This structure-type and related members of a homologous series, offer the possibility that the general sequence of AB(2+n)X(4+n) chemistries could, under certain conditions, be extended to accommodate prevalent oxygen fugacity or, indeed, other ordered stoichiometries through extension of the c axis by the addition of FeO6 octahedral blocks. This structural series, as in other systems, offers possibilities of hosting charge-transfer, Jahn-Teller and other electronic phenomena − as well as supporting metric distortions. Each of these possibilities is highlighted through illustration and extension to related structure-types, most notably from those of the spinels, post-spinels and post-perovskites.

Analysis of stress gradients in physical vapour deposition multilayers by X-ray diffraction at fixed depth intervals

The objective of this article is to develop and apply a model for the design and evaluation of X-ray diffraction experiments to measure phase-specific residual stress profiles in multilayer systems. Using synchrotron radiation and angle-dispersive diffraction, the stress measurements are performed on the basis of the sin2ψ method. Instead of the traditional Ω or χ mode, the experiments are carried out by a simultaneous variation of the goniometer angles χ, Ω and φGto ensure that the penetration and information depth and the measuring direction φ remain unchanged when the polar angle ψ is varied. The applicability of this measuring and evaluation strategy is demonstrated by the example of a multilayer system consisting of Ti and TiAlN layers, alternately deposited on a steel substrate by means of physical vapour deposition.

Imaging the continuous hydrothermal flow synthesis of nanoparticulate CeO2 at different supercritical water temperatures using in situ angle-dispersive diffraction

In situ high-energy synchrotron X-ray diffraction, a non-destructive synchrotron-based technique was employed to probe inside the steel tubing of a continuous hydrothermal flow synthesis (CHFS) mixer to spatially map, for the first time, the superheated water crystallisation of nanocrystalline ceria (CeO2) at three different (superheated-water) temperatures representing three unique chemical environments within the reactor. Rapid hydrothermal co-precipitation at the three selected temperatures led to similarly sized ceria nanoparticles ranging from 3 to 7nm. 2D maps of CeO2 formation were constructed from the intensity and corresponding full width at half maximum (FWHM) values of the two most intense ceria reflections (111) and (002) for all three water inlet temperatures (350, 400 and 450°C at 24MPa) and subsequent changes in the particle size distribution were analysed. The accompanying high-resolution transmission electron microscopy (HRTEM) and tomographic particle size maps have confirmed that the mean ceria particle size slightly increases with temperature. This X-ray tomographic imaging study amounted to a formidable technical and engineering challenge, nevertheless one that has been met; this represents a significant achievement in imaging science, given the dynamic nature and hostile environment of a working CHFS reactor.

Keynote Lecture: Residual Stress Gradient Analysis by Multiple Diffraction Line Methods

The paper deals with methods for X-ray stress analysis (XSA), which allow for the evaluation of near surface in-plane residual stress gradients σ||(τ) and σ||(z) in the LAPLACE- and the real space, respectively. Since the ‘robustness’ of residual stress gradient analysis strongly depends on both, the quality of the measured strain data and the number of experimental data points, the discussion aims at those approaches which are based on processing various diffraction lines or even complete diffraction patterns. It is shown that these techniques, which were originally developed for angle-dispersive (AD) diffraction, can be adapted and enhanced for energy-dispersive (ED) diffraction employing high-energy synchrotron radiation. With the example of a shot-peened ferritic steel it is demonstrated, that sin²ψ-data measured in the Ψ-mode of XSA employing the ED diffraction technique can be analyzed on different levels of approximation.

Residual stress characterization in 12%-Cr steel friction stir welds by neutron diffraction

In the present paper we report the results of a study into friction stir welds made in 12.7 mm-thick 12%-Cr steel plates. Residual stress measurements were performed using angle-dispersive neutron diffraction. Complete characterization of the three-dimensional residual stress state in friction stir weld samples was obtained by analysing diffracted peaks; peak broadening for identifying the regions of severe plastic deformation and the associated residual strain (eigenstrain) acting as the source of residual stress and peak shifting for evaluating residual elastic strains in the welded component. Three different methods were used to address the key issue of determining the d0 variation across the weld. The comb (or matchstick) method was compared with two other approaches: the balance method, and the zero traction method. It was found that a combination of the comb and the zero traction methods allows reliable residual strain/stress distributions.

In Situ Synchrotron X-Ray Step-Scan Diffraction Experiments Using an Energy-Dispersive Setup

This review describes a development of an angle-dispersive step-scan diffraction technique, in which a series of energy-dispersive diffraction data are collected at various 2θ angles. The technique was developed by the GeoSoilEnviroCARS, the University of Chicago in the United States, while experiments were conducted at the SPring-8, Japan. Resultant 2-dimensional diffraction data enable us to recognize very small peaks, such as superlattice reflections. This technique is significantly useful to determine crystal symmetry from powder diffraction when X-ray access to sample is limited.

Characterizing PHASE TRANSFORMATIONS of different LTT alloys and their effect on RESIDUAL STRESSES and COLD CRACKING

Novel martensitic filler materials with specially adjusted martensite start temperatures (Ms) can counteract the cooling specific shrinkage due to expansion effects of the weld metal associated with phase transformations. That can be exploited to create compressive residual stresses in the weld and adjacent areas, i.e. beneficial for increasing fatigue strength. The Ms-temperature is shifted via the chemical composition, mainly by the alloying elements nickel and chromium, resulting as well in different retained austenite contents. Investigations were made using different Low Transformation Temperature (LTT) alloys with varying nickel content. The resulting phase transformation temperatures were — for the first time — detected using high energy synchrotron diffraction and Single Sensor Differential Thermal Analysis (SS-DTA). Compared to angle dispersive diffraction, energy dispersive diffraction offers the possibility to measure residual stresses of the martensite and austenite phase parallel fast in one experiment up to depths of 100 μm. The residual stresses show significant distributions dependent on the Ms-temperature. The effect on the cold cracking behaviour of these alloys was investigated using the Tekken test. Results show that cold cracking can be avoided when appropriate contents of retained austenite are existent.

HIP Production of Diamond-SiC Composites and Their Application to High-Pressure Anvils

Using a hot isostatic pressing (HIP) technique, we synthesized diamond-SiC composites from diamond and Si powders. At an HIP condition of 1450°C and 100 MPa, a pressure much lower than that of the diamond stability field, diamond powders react with molten Si to form well-sintered diamond-SiC composites. Cubes of the composites were thereby fabricated, and an application to the second stage anvils in the Kawai-type multi-anvil high-pressure apparatus was attempted. Since the diamond-SiC composites are transparent to X rays, the present system is applicable not only to conventional energy dispersive X-ray diffraction studies but also to angle dispersive diffraction and radiographic studies that need a larger window for X-ray images. In this article, our recent advances were reviewed.

Energy-dispersive diffraction stress analysis under laboratory and synchrotron conditions: a comparative study

For a feasibility study of energy-dispersive residual stress analysis under laboratory conditions, an X-ray diffractometer that has been operated so far in the angle dispersive diffraction mode was equipped with a commercial tungsten tube and an energy-dispersive solid-state germanium detector. Starting from systematic investigations to find the optimum configuration regarding geometrical resolution, measuring time and stability of the applied detector system, different materials were characterized with respect to the near-surface residual stress state. The results achieved with the modified laboratory equipment within reasonable measuring times are in good agreement with synchrotron measurements performed on the same samples. With the example of a shot-peened Al2O3ceramic with a highly non-uniform near-surface residual stress distribution it is furthermore shown that the different size and shape of the diffracting gauge volume used for the laboratory and synchrotron measurements might have a significant influence on the experimentally obtained Laplace-space residual stress depth profiles σ||(τ).

Synchrotron diffraction study of high-pressure C60 polymerization

C60 polymerization under high pressure and high temperature was studied in situ by angle-dispersive synchrotron diffraction employing a two-dimensional (2D) image plate detector. Preliminary results of this study show that heating fullerene C60 up to 450 °C at 7 GPa leads essentially to the well-known rhombohedral 2D-polymerized phase. In addition, in situ diffraction measurements show that the texture exhibited by the transformed sample results from the anisotropic polymerization occurring on the sample, which in turn is induced by the uniaxial stress component of the applied pressure. The polymerized lattice planes in the transformed sample are then aligned to the compression (uniaxial) axis. Diffraction analysis of the recovered sample has permitted us to identify the presence of a minor phase, the tetragonal 2D polymer.

The Application of Energy Dispersive Diffraction for Nondestructive Analysis of Large Material Depths and for Residual Stress Determination

AbstractAn important advantage of energy dispersive X‐ray diffraction is the opportunity to obtain diffraction patterns without the use of a goniometer. Thus, a combination of small power X‐ray tubes, appropriate X‐ray optics and high energy resolution detectors enables the construction of small and transportable measurement devices. Specimens of different size, shape and geometry can be investigated.Compared with conventional X‐ray diffraction, the energy dispersive method has widened the range of applications in two interesting fields. The simultaneous determination of chemical composition and crystalline structure opens possibilities for single crystal and polycrystalline material characterization.A second effect which can be utilized successfully is based on the wide range of wavelengths, which may be integrated to create one diffraction pattern. So in contrast to the angle dispersive diffraction, a rather large range of penetration depth is available and nondestructive measurements into the depth of the specimen become possible.In this paper, the application of X‐ray high energy dispersive diffraction is demonstrated. Examples from the fields of composites, steel and micro system technologies are presented. Residual stress analyses were preformed and the results were compared with conventional X‐ray stress analyses. New ways to evaluate high energy diffraction patterns will become necessary and some are offered here.

Portable multi-anvil device forin situangle-dispersive synchrotron diffraction measurements at high pressure and temperature

A recently developed portable multi-anvil device for in situ angle-dispersive synchrotron diffraction studies at pressures up to 25 GPa and temperatures up to 2000 K is described. The system consists of a 450 ton V7 Paris-Edinburgh press combined with a Stony Brook ;T-cup' multi-anvil stage. Technical developments of the various modifications that were made to the initial device in order to adapt the latter to angular-dispersive X-ray diffraction experiments are fully described, followed by a presentation of some results obtained for various systems, which demonstrate the power of this technique and its potential for crystallographic studies. Such a compact large-volume set-up has a total mass of only 100 kg and can be readily used on most synchrotron radiation facilities. In particular, several advantages of this new set-up compared with conventional multi-anvil cells are discussed. Possibilities of extension of the (P,T) accessible domain and adaptation of this device to other in situ measurements are given.

Non-cubic crystal symmetry of CaSiO 3 perovskite up to 18 GPa and 1600 K

In situ synchrotron X-ray diffraction experiments have been conducted on CaSiO 3 perovskite (CaPv) in a double-stage multianvil apparatus up to 18 GPa and 1600 K using a newly developed step-scan diffraction technique, which utilizes an energy-dispersive setup with a solid-state detector and collimator assemblies to collect angle-dispersive diffraction data over a wide range of photon energies. Superlattice reflections were resolved throughout the pressure ( P) and temperature ( T) range of the experiments, confirming that the crystal symmetry of CaPv is neither cubic nor tetragonal. A combination of analyses of the complete two-dimensional intensity datasets (photon energy from 20 to 160 keV and 2 θ angle from 3.0° to 9.0°) and Rietveld refinements at selected wavelengths revealed that the most likely space group of CaPv in the experimental P– T range, and therefore in the Earth's transition zone, is either Pbnm or Cmcm. The difference between these two space groups was too small to resolve with our technique.

The large-volume high-pressure facility at GSECARS: A “Swiss-army-knife” approach to synchrotron-based experimental studies

A number of new techniques have been developed at the large-volume press (LVP) high-pressure facility at the GeoSoilEnviroCARS (GSECARS) sector of the advanced photon source (APS). This article describes the 10 MN (1000 T) and 2.5 MN (250 T) hydraulic presses in the insertion device (ID) and bending magnet (BM) beamlines, respectively, with several apparatus and various diffraction and imaging techniques developed since the inception of the facility. Several Kawai-type high-pressure modules, whose second-stage anvils range from 10 mm to 25.4 mm in edge lengths, are used in the hydraulic presses, with pressure ( P) and temperature ( T) capabilities up to 30 GPa and 3000 K. A DIA-type apparatus can be compressed in both presses for studies requiring large sample volumes. A deformation DIA (D-DIA) has been developed to allow controlled deformation studies on both crystalline and glass materials, using monochromatic diffraction and imaging, up to 20 GPa and 1800 K. A high-pressure tomography apparatus is available for conducting tomography studies at high P and T, with a typical spatial resolution of a few micrometers. Toroidal anvil modules provide large 2 θ angles for studies of non-crystalline materials, and a new large D-DIA module is under construction for double-stage megabar pressure generation as well as deformation on large samples with the capability of acoustic emission detection. The flexible design of the monochromator at the BM beamline makes it feasible to switch between monochromatic and white-beam mode during an experiment, ideal for monochromatic imaging studies (e.g., high- P tomography) with energy-dispersive diffraction for pressure measurements. A new angle-dispersive diffraction technique has been developed for high P– T crystallography studies, where a solid-state detector is step-scanned, thereby collecting a large number of angle-dispersive spectra over a wide range of photon energies recorded in the multi-channel analyzer. An ultrasonic interferometer is available and has been used in several high-pressure modules for acoustic velocity measurements. These unique features allow world-wide users to select the best experimental techniques for tackling a wide range of problems relevant to earth and planetary science, materials science, physics, and chemistry. Scientific highlights are provided and future improvements and prospects are discussed.

Melting curve of silicon to 15 GPa determined by two-dimensional angle-dispersive diffraction using a Kawai-type apparatus with X-ray transparent sintered diamond anvils

The melting curve of silicon has been determined up to 15 GPa using a miniaturized Kawai-type apparatus with second-stage cubic anvils made of X-ray transparent sintered diamond. Our results are in good agreement with the melting curve determined by electrical resistivity measurements [V.V. Brazhkin, A.G. Lyapin, S.V. Popova, R.N. Voloshin, Nonequilibrium phase transitions and amorphization in Si, Si/GaAs, Ge, and Ge/GaSb at the decompression of high-pressure phases, Phys. Rev. B 51 (1995) 7549] up to the phase I (diamond structure)—phase II ( β-tin structure)—liquid triple point. The triple point of phase XI (orthorhombic, Imma)—phase V (simple hexagonal)—liquid has been constrained to be at 14.4(4) GPa and 1010(5) K. These results demonstrate that the combination of X-ray transparent anvils and monochromatic diffraction with area detectors offers a reliable technique to detect melting at high pressures in the multianvil press.

Residual stress depth profiling in complex hard coating systems by X-ray diffraction

X-ray residual stress analysis on multilayered coating systems is a quite difficult and demanding procedure. To obtain information on both, the individual sublayers the coating consists of and the interfacial substrate region, it is necessary to apply different methods which are complementary with respect to the accessible information depth. Based on the concept of an ‘equivalent thickness’ for describing angle-dispersive diffraction in multilayer structures, a method is proposed that allows for the evaluation of steep intra — as well as interlayer stress gradients within the upper sublayers of multilayer coating systems. Furthermore, energy-dispersive diffraction is shown suitable to detect the residual stress distribution in the near interface substrate zone beneath the coatings. The applicability of the approaches introduced here is demonstrated by the example of cemented carbide WC/Co cutting tools being coated by chemical vapor deposition with sequences of Al 2O 3/TiCN sublayers.

Single-crystal synchrotron X-ray diffraction study of wüstite and magnesiowüstite at lower-mantle pressures

This study demonstrates the use of monochromatic synchrotron X-ray radiation of 40 keV for high-precision equation-of-state studies on sets of single crystals analysed individually in the same diamond-anvil pressure cell. Angle-dispersive zone-axis diffraction patterns were obtained from crystals of wustite-Fe0.93O and magnesiowüstite-(Mg0.73Fe0.27)O to 51 GPa in a hydrostatic helium pressure medium. The rhombohedral phase of Fe0.93O was observed above 23 GPa, and its isothermal bulk modulus (K0) was determined to be 134 (+/-4) GPa, assuming K'=4. The rhombohedral phase of Fe(0.93)O is more compressible than B1-structured Fe0.93O, with K0=146 (+/-2) GPa. Magnesiowüstite-(Mg0.73Fe0.27)O remains cubic over the experimental pressure range, and has a bulk modulus of 154 (+/-3) GPa with K'=4.0 (+/-0.1).