In situ synchrotron diffraction studies on the formation kinetics of jarosites

This paper reports the results of time‐resolved synchrotron powder diffraction experiments where jarosites with different K/H₃O, K/Na and Na/H₃O ratios were synthesized in situ at temperatures of 353, 368 and 393 K in order to observe the effect on kinetics and species produced. The Na/H₃O sample formed monoclinic jarosite at all three temperatures, whereas the K/H₃O and K/Na samples formed as rhombohedral jarosites at 353 K, and as mixtures of rhombohedral and monoclinic jarosites at the higher temperatures. The relative amount of the monoclinic phase increased with increase in temperature. Unit‐cell parameter changes with reaction time could be explained by changes in iron stoichiometry (samples become more stoichiometric with time) together with changes in K/H₃O and Na/H₃O ratios. The reaction kinetics have been fitted using a two‐stage Avrami model, with two different Avrami exponents corresponding to initial two‐dimensional growth followed by one‐dimensional diffusion‐controlled growth. Activation energies for the initial growth stage were calculated to be in the range 90–126 kJ mol^?1.     

In situ X‐ray diffraction study on the growth kinetics of NiO nanoparticles

The growth kinetics of NiO nanoparticles have been studied by in situ X‐ray diffraction using two detection systems (conventional and imaging plate). NiO nanoparticles were formed by thermal decomposition after heating of an amorphous compound formed by the coprecipitation method. It was found that the detection method using an imaging plate is more efficient than the conventional detection mode for observing changes in the crystallite growth of nanocrystalline materials. Studies have been carried out to investigate the effects of the heating rates on the particles growth. The results suggest that the growth process of the particles is accelerated when the samples are treated at low heating rates. The evolution of particles size and the diffusion coefficient obtained from X‐ray powder diffraction patterns are discussed in terms of the thermal conditions for the two types of detection.     

Design and development of a controlled pressure/temperature set‐up for in situ studies of solid–gas processes and reactions in a synchrotron X‐ray powder diffraction station

A novel set‐up has been designed and used for synchrotron radiation X‐ray high‐resolution powder diffraction (SR‐HRPD) in transmission geometry (spinning capillary) for in situ solid–gas reactions and processes in an isobaric and isothermal environment. The pressure and temperature of the sample are controlled from 10^?3 to 1000 mbar and from 80 to 1000 K, respectively. To test the capacities of this novel experimental set‐up, structure deformation in the porous material zeolitic imidazole framework (ZIF‐8) by gas adsorption at cryogenic temperature has been studied under isothermal and isobaric conditions. Direct structure deformations by the adsorption of Ar and N₂ gases have been observed in situ, demonstrating that this set‐up is perfectly suitable for direct structural analysis under in operando conditions. The presented results prove the feasibility of this novel experimental station for the characterization in real time of solid–gas reactions and other solid–gas processes by SR‐HRPD.     

In situ synchrotron high‐energy X‐ray diffraction analysis on phase transformations in Ti–Al alloys processed by equal‐channel angular pressing

Mixtures of 47‐Al and 53‐Ti powders (atomic %) have been consolidated using back pressure equal‐channel angular pressing starting with both raw and ball‐milled powders. In situ synchrotron high‐energy X‐ray diffraction studies are presented with continuous Rietveld analysis obtained upon a heating ramp from 300 K to 1075 K performed after the consolidation process. Initial phase distributions contain all intermetallic compounds of this system except Al, with distribution maxima in the outer regions of the concentrations (α‐Ti, TiAl₃). Upon annealing, the phase evolution and lattice parameter changes owing to chemical segregation, which is in favour for the more equilibrated phases such as γ‐TiAl, α₂‐Ti₃Al and TiAl₂, were followed unprecedentedly in detail. An initial δ‐TiH₂ content with a phase transition at about 625 K upon heating created an intermediate β‐Ti phase which played an important role in the reaction chain and gradually transformed into the final products.     

Portable multi‐anvil device for in situ angle‐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.     

High‐throughput synchrotron X‐ray diffraction for combinatorial phase mapping

Discovery of new materials drives the deployment of new technologies. Complex technological requirements demand precisely tailored material functionalities, and materials scientists are driven to search for these new materials in compositionally complex and often non‐equilibrium spaces containing three, four or more elements. The phase behavior of these high‐order composition spaces is mostly unknown and unexplored. High‐throughput methods can offer strategies for efficiently searching complex and multi‐dimensional material genomes for these much needed new materials and can also suggest a processing pathway for synthesizing them. However, high‐throughput structural characterization is still relatively under‐developed for rapid material discovery. Here, a synchrotron X‐ray diffraction and fluorescence experiment for rapid measurement of both X‐ray powder patterns and compositions for an array of samples in a material library is presented. The experiment is capable of measuring more than 5000 samples per day, as demonstrated by the acquisition of high‐quality powder patterns in a bismuth–vanadium–iron oxide composition library. A detailed discussion of the scattering geometry and its ability to be tailored for different material systems is provided, with specific attention given to the characterization of fiber textured thin films. The described prototype facility is capable of meeting the structural characterization needs for the first generation of high‐throughput material genomic searches.     

Design and application of a high‐temperature microfurnace for an in situ X‐ray diffraction study of phase transformation

Thermal treatment of mineral ores such as ilmenite can initiate phase transformations that could affect their activation or deactivation, subsequently influencing their ability to dissolve in a leaching agent. Most laboratory‐based X‐ray diffraction (XRD) studies were carried out ex situ in which realistic diffraction patterns could not be obtained simultaneously with occurring reactions and were time‐consuming. The availability of synchrotron‐radiation‐based XRD not only allows in situ analysis, but significantly shortens the data recording time. The present study details the design of a robust high‐temperature microfurnace which allows thermal processing of mineral ore samples and the simultaneous collection of high‐resolution synchrotron XRD data. In addition, the application of the manufactured microfurnace for in situ study of phase transformations of ilmenite ore under reducing conditions is demonstrated.     

X‐ray powder diffraction at the XRD1 beamline at LNLS

Various upgrades have been completed at the XRD1 beamline at the Brazilian synchrotron light source (LNLS). The upgrades are comprehensive, with changes to both hardware and software, now allowing users of the beamline to conduct X‐ray powder diffraction experiments with faster data acquisition times and improved quality. The main beamline parameters and the results obtained for different standards are presented, showing the beamline ability of performing high‐quality experiments in transmission geometry. XRD1 operates in the 5.5–14 keV range and has a photon flux of 7.8 × 10⁹ photons s^?1 (with 100 mA) at 12 keV, which is one of the typical working energies. At 8 keV (the other typical working energy) the photon flux at the sample position is 3.4 × 10¹⁰ photons s^?1 and the energy resolution ΔE/E = 3 × 10^?4.     

Performance calculations of the X‐ray powder diffraction beamline at NSLS‐II

The X‐ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source II is a multi‐purpose high‐energy X‐ray diffraction beamline with high throughput and high resolution. The beamline uses a sagittally bent double‐Laue crystal monochromator to provide X‐rays over a large energy range (30–70 keV). In this paper the optical design and the calculated performance of the XPD beamline are presented. The damping wiggler source is simulated by the SRW code and a filter system is designed to optimize the photon flux as well as to reduce the heat load on the first optics. The final beamline performance under two operation modes is simulated using the SHADOW program. For the first time a multi‐lamellar model is introduced and implemented in the ray tracing of the bent Laue crystal monochromator. The optimization and the optical properties of the vertical focusing mirror are also discussed. Finally, the instrumental resolution function of the XPD beamline is described in an analytical method.     

A curved image‐plate detector system for high‐resolution synchrotron X‐ray diffraction

The developed curved image plate (CIP) is a one‐dimensional detector which simultaneously records high‐resolution X‐ray diffraction (XRD) patterns over a 38.7° 2θ range. In addition, an on‐site reader enables rapid extraction, transfer and storage of X‐ray intensity information in ≤30 s, and further qualifies this detector to study kinetic processes in materials science. The CIP detector can detect and store X‐ray intensity information linearly proportional to the incident photon flux over a dynamical range of about five orders of magnitude. The linearity and uniformity of the CIP detector response is not compromised in the unsaturated regions of the image plate, regardless of saturation in another region. The speed of XRD data acquisition together with excellent resolution afforded by the CIP detector is unique and opens up wide possibilities in materials research accessible through X‐ray diffraction. This article presents details of the basic features, operation and performance of the CIP detector along with some examples of applications, including high‐temperature XRD.     

Individual GaAs nanorods imaged by coherent X‐ray diffraction

Using scanning X‐ray diffraction microscopy with a spot size of 220 × 600 nm, it was possible to inspect individual GaAs nanorods grown seed‐free through circular openings in a SiN_x mask in a periodic array with 3 µm spacing on GaAs[111]B. The focused X‐ray beam allows the determination of the strain state of individual rods and, in combination with coherent diffraction imaging, it was also possible to characterize morphological details. Rods grown either in the centre or at the edge of the array show significant differences in shape, size and strain state.     

Rietveld analysis of high pressure powder diffraction data

Abstract

X-ray and neutron powder diffraction data obtained from samples contained within high pressure cells are generally of lower quality than data collected from samples at ambient conditions. The far smaller sample size as well as possible contamination of the pattern by the pressure cell means that Rietveld refinement techniques must be adapted to extract the maximum useful information from the data. These problems become paramount as larger structures at high pressure are attempted. Techniques such as “leBail extraction”, “soft restraints” and “rigid body refinement” will be discussed with application to analysis of high pressure neutron powder diffraction data.     

In situ rheological measurements at extreme pressure and temperature using synchrotron X‐ray diffraction and radiography

Dramatic technical progress seen over the past decade now allows the plastic properties of materials to be investigated under extreme pressure and temperature conditions. Coupling of high‐pressure apparatuses with synchrotron radiation significantly improves the quantification of differential stress and specimen textures from X‐ray diffraction data, as well as specimen strains and strain rates by radiography. This contribution briefly reviews the recent developments in the field and describes state‐of‐the‐art extreme‐pressure deformation devices and analytical techniques available today. The focus here is on apparatuses promoting deformation at pressures largely in excess of 3 GPa, namely the diamond anvil cell, the deformation‐DIA apparatus and the rotational Drickamer apparatus, as well as on the methods used to carry out controlled deformation experiments while quantifying X‐ray data in terms of materials rheological parameters. It is shown that these new techniques open the new field of in situ investigation of materials rheology at extreme conditions, which already finds multiple fundamental applications in the understanding of the dynamics of Earth‐like planet interior.     

High‐performance X‐ray detectors for the new powder diffraction beamline I11 at Diamond

The design and performance characterization of a new light‐weight and compact X‐ray scintillation detector is presented. The detectors are intended for use on the new I11 powder diffraction beamline at the third‐generation Diamond synchrotron facility where X‐ray beams of high photon brightness are generated by insertion devices. The performance characteristics of these detection units were measured first using a radioactive source (efficiency of detection and background count rate) and then synchrotron X‐rays (peak stability, light yield linearity and response consistency). Here, the results obtained from these tests are reported, and the suitability of the design for the Diamond powder beamline is demonstrated by presenting diffraction data obtained from a silicon powder standard using a prototype multicrystal analyser stage.     

X‐ray dynamical diffraction Fraunhofer holography

An X‐ray dynamical diffraction Fraunhofer holographic scheme is proposed. Theoretically it is shown that the reconstruction of the object image by visible light is possible. The spatial and temporal coherence requirements of the incident X‐ray beam are considered. As an example, the hologram recording as well as the reconstruction by visible light of an absolutely absorbing wire are discussed.     

Identification and spectra–structure determination of soil minerals: Raman study supported by IR spectroscopy and X‐ray powder diffraction

Raman and IR spectroscopy were used for the characterization of several minerals in morphologically similar vertisol sequences from Kiževak (Serbia). It helped us to establish the surface layer transition going from calcic vertisols (containing gypsum and calcite) to calcimagnesic vertisols (containing aragonite, magnesium‐calcite and dolomite) derived from peridotite and serpentinite. The observed band positions are found to be solely characteristic for each carbonate mineral and are used to discuss the main structural features of carbonates and sulfates present in the studied soil. It was found that the dolomite, calcite and aragonite concretions are present in the deepest layer of the soil, whereas the gypsum is found in the topsoil. The identification was confirmed of the carbonates having calcite and aragonite structure, and the representative from the sulfate group (gypsum) was confirmed by X‐ray powder diffraction. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication and testing of a newly designed slit system for depth‐resolved X‐ray diffraction measurements

A new system of slits called `spiderweb slits' have been developed for depth‐resolved powder or polycrystalline X‐ray diffraction measurements. The slits act on diffracted X‐rays to select a particular gauge volume of sample, while absorbing diffracted X‐rays from outside of this volume. Although the slit geometry is to some extent similar to that of previously developed conical slits or spiral slits, this new design has advantages over the previous ones in use for complex heterogeneous materials and in situ and operando diffraction measurements. For example, the slits can measure a majority of any diffraction cone for any polycrystalline material, over a continuous range of diffraction angles, and work for X‐ray energies of tens to hundreds of kiloelectronvolts. The design is generated and optimized using ray‐tracing simulations, and fabricated through laser micromachining. The first prototype was successfully tested at the X17A beamline at the National Synchrotron Light Source, and shows similar performance to simulations, demonstrating gauge volume selection for standard powders, for all diffraction peaks over angles of 2–10°. A similar, but improved, design will be implemented at the X‐ray Powder Diffraction beamline at the National Synchrotron Light Source II.     

Understanding the instrumental profile of synchrotron radiation X‐ray powder diffraction beamlines

A Monte Carlo algorithm has been developed to calculate the instrumental profile function of a powder diffraction synchrotron beamline. Realistic models of all optical elements are implemented in a ray‐tracing software. The proposed approach and the emerging paradigm have been investigated and verified for several existing X‐ray powder diffraction beamlines. The results, which can be extended to further facilities, show a new and general way of assessing the contribution of instrumental broadening to synchrotron radiation data, based on ab initio simulations.     

Utilizing broadband X‐rays in a Bragg coherent X‐ray diffraction imaging experiment

A method is presented to simplify Bragg coherent X‐ray diffraction imaging studies of complex heterogeneous crystalline materials with a two‐stage screening/imaging process that utilizes polychromatic and monochromatic coherent X‐rays and is compatible with in situ sample environments. Coherent white‐beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three‐dimensional reciprocal‐space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifying in situ chamber design. This approach was demonstrated with Au nanoparticles and will enable, for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.