Tomographic Energy Dispersive Diffraction Imaging Research Articles

The development of rapid tomographic energy-dispersive diffraction imaging TEDDI

The development of rapid tomographic energy-dispersive diffraction imaging TEDDI

A synchrotron tomographic energy-dispersive diffraction imaging study of the aerospace alloy Ti 6246

A titanium alloy sample (#6246) containing a linear friction weld has been imaged nondestructively using tomographic energy-dispersive diffraction imaging (TEDDI). The diffraction patterns measured at each point of the TEDDI image permitted identification of the material and phases present (±5%). The image also showed the preferred orientation and size–strain distribution present within the sample without the need for any further sample preparation. The preferred orientation was observed in clusters with average dimensions very similar to the experimental spatial resolution (400 µm). The length scales and preferred orientation distributions were consistent with orientation imaging microscopy measurements made by Szczepanski, Jha, Larsen & Jones [Metall. Mater. Trans. A(2008),39, 2841–2851] where the microstructure development was linked to the grain growth of the parent material. The use of a high-energy X-ray distribution (30–80 keV) in the incident beam reduced systematic errors due to the source profile, sample and air absorption. The TEDDI data from each voxel were reduced to an angle-dispersive form and Rietveld refined to a mean χ2of 1.4. The mean lattice parameter error (δd/d) ranged from ∼10−4for the highly crystalline regions to ∼10−3for regions of very strong preferred orientation and internal strain. The March–Dollase preferred orientation errors refined to an average value of ±2%. A 100% correlation between observed fluorescence and diffraction peak broadening was observed, providing further evidence for vicinal strain broadening.

Profiling Physicochemical Changes within Catalyst Bodies during Preparation: New Insights from Invasive and Noninvasive Microspectroscopic Studies

Cylindrical or spherical catalyst bodies with sizes ranging from tens of micrometers to a few millimeters have a wide variety of industrial applications. They are crucial in the oil refining industry and in the manufacture of bulk and fine chemicals. Their stability, activity, and selectivity are largely dependent on their preparation; thus, achieving the optimum catalyst requires a perfect understanding of the physicochemical processes occurring in a catalyst body during its synthesis. The ultimate goal of the catalyst researcher is to visualize these physicochemical processes as the catalyst is being prepared and without interfering with the system. In order to understand this chemistry and improve catalyst design, researchers need better, less invasive tools to observe this chemistry as it occurs, from the first stages in contact with a precursor all the way through its synthesis. In this Account, we provide an overview of the recent advances in the development of space- and time-resolved spectroscopic methods, from invasive techniques to noninvasive ones, to image the physicochemical processes taking place during the preparation of catalyst bodies. Although several preparation methods are available to produce catalyst bodies, the most common method used in industry is the incipient wetness impregnation. It is the most common method used in industry because it is simple and cost-effective. This method consists of three main steps each of which has an important role in the design of a catalytic material: pore volume impregnation, drying, and thermal treatment. During the impregnation step, the interface between the support surface and the precursor of the active phase at the solid-liquid interface is where the critical synthetic chemistry occurs. Gas-solid and solid-solid interfaces are critical during the drying and thermal treatment steps. Because of the length scale of these catalyst bodies, the interfacial chemistry that occurs during preparation is space-dependent. Different processes occurring in the core or in the outer rim of the catalytic solid are enhanced by several factors, such as the impregnation solution pH, the metal ion concentration, the presence of organic additives, and the temperature gradients inside the body. Invasive methods for studying the molecular nature of the metal-ion species during the preparation of catalyst bodies include Raman, UV-vis-NIR, and IR microspectroscopies. Noninvasive techniques include magnetic resonance imaging (MRI). Synchrotron-based techniques such as tomographic energy dispersive diffraction imaging (TEDDI) and X-ray microtomography for noninvasive characterization are also evaluated.

Tomographic Energy Dispersive Diffraction Imaging To Study the Genesis of Ni Nanoparticles in 3D within γ-Al2O3 Catalyst Bodies

Tomographic energy dispersive diffraction imaging (TEDDI) is a recently developed synchrotron-based characterization technique used to obtain spatially resolved X-ray diffraction and fluorescence information in a noninvasive manner. With the use of a synchrotron beam, three-dimensional (3D) information can be conveniently obtained on the elemental composition and related crystalline phases of the interior of a material. In this work, we show for the first time its application to characterize the structure of a heterogeneous catalyst body in situ during thermal treatment. Ni/gamma-Al(2)O(3) hydrogenation catalyst bodies have been chosen as the system of study. As a first example, the heat treatment in N(2) of a [Ni(en)(3)](NO(3))(2)/gamma-Al(2)O(3) catalyst body has been studied. In this case, the crystalline [Ni(en)(3)](NO(3))(2) precursor was detected in an egg-shell distribution, and its decomposition to form metallic Ni crystallites of around 5 nm was imaged. In the second example, the heat treatment in N(2) of a [Ni(en)(H(2)O)(4)]Cl(2)/gamma-Al(2)O(3) catalyst body was followed. The initial [Ni(en)(H(2)O)(4)]Cl(2) precursor was uniformly distributed within the catalyst body as an amorphous material and was decomposed to form metallic Ni crystallites of around 30 nm with a uniform distribution. TEDDI also revealed that the decomposition of [Ni(en)(H(2)O)(4)]Cl(2) takes place via two intermediate crystalline structures. The first one, which appears at around 180 degrees C, is related to the restructuring of the Ni precursor on the alumina surface; the second one, assigned to the formation of a limited amount of Ni(3)C, is observed at 290 degrees C.

Performance limitations of the pixelated ERD detector with respect to imaging using the rapid Tomographic Energy Dispersive Diffraction Imaging system

A prototype X-ray imaging system, using the principle of Tomographic Energy Dispersive Diffraction Imaging (TEDDI) has been developed at the University of Manchester's School of Materials. The non-destructive 3D imaging system makes use of a state of the art collimator array and a pixellated Si energy resolving detector. The new rapid TEDDI system is limited to thin, low density materials due to the low stopping power of Si at higher X-ray energies. In this paper the results of substituting Si for CdZnTe as the active detection element and limitations to the key parameters of energy resolution and count rate, for the detectors is presented. The findings have led to the design of a new ASIC which is discussed.

Reconstructive colour X-ray diffraction imaging – a novel TEDDI imaging method

Tomographic Energy-Dispersive Diffraction Imaging (TEDDI) enables a unique non-destructive mapping of the interior of bulk objects, exploiting the full range of X-ray signals (diffraction, fluorescence, scattering, background) recorded. By analogy to optical imaging, a wide variety of features (structure, composition, orientation, strain) dispersed in X-ray wavelengths can be extracted and colour-coded to aid interpretation. The ultimate aim of this approach is to realise real-time high-definition colour X-ray diffraction imaging, on the timescales of seconds, so that one will be able to 'look inside' optically opaque apparatus and unravel the space/time-evolution of the materials chemistry taking place. This will impact strongly on many fields of science but there are currently two barriers to this goal: speed of data acquisition (a 2D scan currently takes minutes to hours) and loss of image definition through spatial distortion of the X-ray sampling volume. Here we present a data-collection scenario and reconstruction routine which overcomes the latter barrier and which has been successfully applied to a phantom test object and to real materials systems such as a carbonating cement block. These procedures are immediately transferable to the promising technology of multi-energy-dispersive-detector-arrays which are planned to deliver the other breakthrough, that of one-two orders of magnitude improvement in data acquisition rates, that will be needed to realise real-time high-definition colour X-ray diffraction imaging.

Intruder alert [Military technology applications in healthcare sector

It is believed that signal-processing techniques used in military radar systems could help cut deaths from stroke by improving early diagnosis and the same approach could provide a more effective way of monitoring patients as they recover. This research has involved processing transcranial Doppler ultrasound (TCD) radio-frequency signals, to develop new techniques for the detection of cerebral emboli and to improve the axial resolution obtainable from TCD systems. Using a technique derived from military radar systems, it has been able to increase the bandwidth of the transmitted pulse and improve the axial resolution of Doppler ultrasound. The latest clinical trials in the United States of a breast cancer treatment that takes advantage of heat therapy derived from radar research suggest it can significantly increase the effectiveness of chemotherapy. Scientists at the University of Manchester are working on an X-ray technique that as well as detecting hidden explosives and drugs could help treat cancers more effectively. Known as tomographic energy dispersive diffraction imaging, or TEDDI, it harnesses all the wavelengths present in an X-ray beam to create probing 3D pictures.

Hydrothermal/autoclave synthesis of AlPO-5: a prototype space/time study of crystallisation gradients

TEDDI (tomographic energy dispersive diffraction imaging) has been used for in situ time-resolved studies of hydrothermal synthesis of Ge doped AlPO-5. The data for three different levels of Ge doping into AlPO-5 system are presented. Two pathways are observed, the simplest being a direct formation of ALPO-5 accompanied by simultaneous GeO2 dissolution in the bulk gel, plus a variation in which ALPO-5 acts as an intermediate in the formation of ALPO-18, a related framework structure. The TEDDI approach is able to show that these synthesis pathways and kinetics vary significantly with depth inside the synthesis vessel and possible explanations for this are discussed.

X-ray colour imaging

A prototype X-ray colour imaging system has been assembled using the principle of tomographic energy-dispersive diffraction imaging (TEDDI). The new system has been tested using samples of nylon-6, aluminium powder and deer antler bone. Non-destructive three-dimensional images of the test objects have been reconstructed on a 300 microm scale with an associated diffraction pattern at each voxel. In addition, the lattice parameters of the polycrystalline material present in the sampled voxels have been determined using full pattern refinement methods. The use of multiple diffracted parallel colour X-ray beams has allowed simultaneous spatially resolved data collection across a plane of the sample. This has simplified the sample scan motion and has improved data collection times by a factor scaling with the number of detector pixels. The TEDDI method is currently limited to thin samples (approx. 1-2mm) with light atoms owing to the very low detection efficiency of the silicon detector at X-ray energies above 25 keV. We describe how these difficulties can be removed by using semiconductor detectors made from heavier atomic material.

Tomographic Energy Dispersive Diffraction Imaging as a Tool To Profile in Three Dimensions the Distribution and Composition of Metal Oxide Species in Catalyst Bodies

Catalyst extrudate in 3D: Through the use of tomographic energy dispersive diffraction imaging it is possible to obtain detailed three-dimensional insight into the metal oxide distribution inside a catalyst extrudate during its preparation. The picture shows such a 3D map of an extrudate along with examples of the detector signal for two different locations in the catalyst. (Graph Presented). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

Cover Picture: Tomographic Energy Dispersive Diffraction Imaging as a Tool To Profile in Three Dimensions the Distribution and Composition of Metal Oxide Species in Catalyst Bodies (Angew. Chem. Int. Ed. 46/2007)

Cover Picture: Tomographic Energy Dispersive Diffraction Imaging as a Tool To Profile in Three Dimensions the Distribution and Composition of Metal Oxide Species in Catalyst Bodies (Angew. Chem. Int. Ed. 46/2007)

Tomographic Energy Dispersive Diffraction Imaging as a Tool To Profile in Three Dimensions the Distribution and Composition of Metal Oxide Species in Catalyst Bodies

3D-Karten von Katalysatoren: Die tomographische Bildgebung durch energiedispersive Beugung liefert Informationen über die dreidimensionale Metalloxidverteilung im Inneren eines Katalysatorextrudats während dessen Präparation. Das Bild zeigt eine solche 3D-Karte sowie die Detektorsignale an zwei Stellen im Katalysator.

Direct correlation between ferrite microstructure and electrical resistivity

Variations in the composition and microstructure of Mn-Zn soft ferrites have been directly correlated with spatial variations in electrical resistivity, which were both observed to occur on a length scale of approximately 500 μm. Tomographic energy dispersive diffraction imaging (TEDDI) was used to determine the nonsystematic change in the lattice parameter across the sample volume (8.48±0.05 Å) at a spatial resolution of 50 μm. We have used a microprobe contact technique to measure the local electrical resistivity (∼35 Ω cm) and density functional theory to model the band structure. The band structure calculations directly utilized the experimentally measured lattice parameters from the TEDDI measurements and were in good agreement with the measured resistivity. The mean band gap shrinkage was found to be 0.02 eV. This value for Eg was found to account well for the observed 10−20 Ω cm resistivity variations.

The manufacture of a very high precision x-ray collimator array for rapid tomographic energy dispersive diffraction imaging (TEDDI)

A very high resolution x-ray collimator array has been constructed for use with tomographic energy dispersive diffraction imaging (TEDDI). The collimator consists of a 16 × 16 array of 50 µm diameter holes in a series of 0.1 mm tungsten plates aligned to a tolerance of ±2 µm. The minimum angular divergence of the transmitted x-ray beams through each transmission pathway in the collimator array has been designed to be 0.02°, which is equivalent to an energy dispersed resolution of 250 eV with an aspect ratio of 6000:1. The collimator array has been matched to the development of an energy sensitive x-ray detector array (Seller et al 1998 Proc. SPIE 3445 584–92) for TEDDI studies of materials. The very high tolerance of the aperture size and placement was achieved by utilizing high intensity femtosecond pulse duration laser machining from a diode pumped solid state laser (DPSS). Using a novel arrangement the laser acted as the principal alignment and cutting tool. The collimator transmission function has been tested using a uniform synchrotron radiation flood field. The transmission and spatial uniformity were found to be consistent with the design parameters for TEDDI applications and also as a diffracted beam collimator for monochromatic powder diffraction studies.

A new, rapid 3D tomographic energy dispersive diffraction imaging system for materials characterisation and object imaging (rapid TEDDI)

A new, rapid 3D tomographic energy dispersive diffraction imaging system for materials characterisation and object imaging (rapid TEDDI)

Use of Synchrotron Tomographic Techniques in the Assessment of Diffusion Parameters for Solute Transport in Groundwater Flow

This technical note describes the use of time-resolved synchrotron radiation tomographic energy dispersive diffraction imaging (TEDDI) and tomographic X-ray fluorescence (TXRF) for examining ion diffusion in porous media. The technique is capable of tracking the diffusion of several ion species simultaneously. This is illustrated by results which compare the movement of Cs+, Ba2+ and La3+ ions from solution into a typical sample of English chalk. The results exhibited somewhat anomalous (non-Fickian) behaviour and revealed heterogeneities (in 1D) on the scale of a few millimetres.

Porosity Imaging in Porous Media Using Synchrotron Tomographic Techniques

This paper describes novel uses of synchrotron radiation in examining porosity distributions within porous media. Tomographic energy dispersive diffraction imaging and Tomographic X-ray fluorescence have been combined within one measurement method and used to highlight the porosity distribution in a typical sample of English Chalk.

TOMOGRAPHIC ENERGY-DISPERSIVE TOMOGRAPHIC ENERGY-DISPERSIVE DYNAMIC SYSTEMS

Tomographic energy-dispersive diffraction imaging (TEOOI) is a technique, which exploits a well-defined energetic white X-ray beam from a synchrotron to gain diffraction information from volume elements within a bulk sample. Most tomographic methods rely on spectroscopic absorption or fluorescence signals to provide elementaUcompositional contrast; by comparison TEDDI provides structural contrast, through diffraction, irrespective of whether there is any elemental variation, At the heart of this technique is energy-dispersive diffraction (EDD), which is a mode of X-ray diffraction less-familiar to most researchers and is therefore briefly outlined prior to a basic description of the TEDDI technique; this technique is then illustrated by studies carried out on white beam instruments at the SRS (station 16.4) and ESRF (beamlines ID9 and 1030) synchrotron sources, with examples taken from materials/engineering science involving both static and dynamic systems.

Non-destructive tomographic energy-dispersive diffraction imaging of the interior of bulk concrete

A new tomographic technique, termed TEDDI (tomographic energy-dispersive diffraction imaging) has recently been invented by Hall et al. [C. Hall, P.Barnes, J.K. Cockcroft, S.L. Colston, D. Hausermann, S.D.M. Jacques, A.C. Jupe, M. Kunz, Synchrotron radiation energy-dispersive diffraction tomography, Nucl Instrum Methods Res, Sect B 140 (1998) 253–257; C. Hall, P. Barnes, J.K. Cockcroft, S.D.M. Jacques, A.C. Jupe, X. Turrillas, M. Hanfland, D. Hausermann, Rapid whole-rock mineral analysis and composition mapping by synchrotron X-ray diffraction, Anal Commun 33 (1996) 245–248] and applied to cementitious systems. TEDDI has notable unique features in that: • it exploits diffraction, rather than spectroscopic sensing, and therefore directly yields compositional/structural information about the sample; • the diffracting region can be made small or large depending on application, the ultimate spatial resolution being in the micron range; • with the use of energetic (20–125 keV) synchrotron beams, bulk objects such as concrete blocks can be penetrated so that the technique becomes non-destructive. We report on early tests of this technique as a means to non-destructively examine the interior of concrete prism specimens. Concrete, by definition, is a heterogeneous material because it contains coarse aggregates on a length scale of ∼1 cm. This is orders of magnitude larger than the effective penetration depth of conventional X-ray diffraction systems (typically <100 μm at 1.54 Å) which, therefore, cannot probe the interior of intact concrete specimens. It is possible to pulverize concrete, sift out the aggregates, and analyze the remaining fraction but the degree of representation of such powders is questioned since certain phases may be lost or enriched during this process; furthermore, the spatial distribution of the analyzed phases within the concrete will be lost and, with it, important information such as whether the phase in question forms in the cement paste matrix or at the aggregate interface. Even after these limitations, conventional diffraction/microscopy analysis is at best a “one shot” process in time. The TEDDI technique has the promise to avoid all these problems by enabling the examination of intact concrete specimens on the length scale of several centimeters.