X-ray colour imaging

Cernik, Robert J.; Khor, Kern Hauw; Hansson, Conny

doi:10.1098/rsif.2007.1249

Cited by 35 publications

(25 citation statements)

References 14 publications

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“…Whilst the former is limited to the study of paramagnetic species and is therefore almost exclusively limited to probing the impregnation stage, TEDDI provides detailed information regarding elemental and crystalline phase distributions. [18,19] However, this technique currently suffers from a comparatively poor time resolution (on the order of hours) and instrument peakwidth resolution. In this regard, a diffraction measurement technique that is capable of improving on the inherent weaknesses of TEDDI would represent a significant advancement.…”

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confidence: 99%

Dynamic X‐Ray Diffraction Computed Tomography Reveals Real‐Time Insight into Catalyst Active Phase Evolution

et al. 2011

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Dedicated to the Fritz Haber Institute, Berlin, on the occasion of its 100th anniversary Metals and metal oxides anchored to porous support materials are widely used as heterogeneous catalysts in a number of important industrial chemical processes. These catalysts owe their activity to the formation of unique metal/metal oxide support interactions, typically resulting in highly dispersed actives stabilized in a particular electronic or coordination state. [1][2][3] They are employed in fixed-bed reactors as extruded or pelletized millimeter-sized "catalyst bodies" minimizing pressure drops along the length of the reactor. Since the efficiency of the whole catalytic system depends on the behavior and efficiency of the catalyst body per se, its design has very great importance. Crucial to this design is an understanding of the factors which influence the distribution and nature of the active phase during preparation. The type of desired distribution is very much dependant on catalytic process and required products; for example, an egg-shell distribution (as opposed to uniform, egg-white, or egg-yolk), where the active phase is located at the edges of the catalyst body, can be favored if the product forms readily. [4,5] Herein, we study catalyst bodies of nickel supported on gAl 2 O 3 . These catalysts are widely employed for hydrogenation. [1][2][3]6] They are often prepared using highly soluble nickel nitrate or chloride precursor salts, which allow for the preparation of catalysts with high metal loadings in a single impregnation step. Two problems are commonly encountered with the preparation of these catalysts: the formation of unwanted metal aluminate (spinel) phases and poor metal dispersion within the catalyst body. The dispersion of the metal ions within the alumina can be controlled by the addition of complexing agents to the impregnation solution, thereby changing the molecular structure of the precursor (through ligand exchange) as well as the interactions of the precursor with the support. Additionally, the presence of chelating ligands in the precursor increases both the metal oxide reducibility and dispersion. [7][8][9][10] In recent times, absorption, spectroscopic, and scattering techniques have been developed to obtain spatial information on the distribution of chemical species in catalyst bodies, which allows the phenomena taking place during their preparation to be monitored. [7] These techniques include Raman, IR, and UV/Vis microspectroscopy; magnetic resonance imaging (MRI); tomographic energy dispersive diffraction imaging (TEDDI); and micro-computed tomography (mCT). [11][12][13][14][15][16][17] Importantly, both MRI and TEDDI are able to probe in a non-invasive manner in two dimensions, thus providing time-resolved information on both the impregnation and calcination/activation processes. Whilst the former is limited to the study of paramagnetic species and is therefore almost exclusively limited to probing the impregnation stage, TEDDI provides detailed information regarding elemental and ...

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confidence: 99%

Dynamic X‐Ray Diffraction Computed Tomography Reveals Real‐Time Insight into Catalyst Active Phase Evolution

et al. 2011

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“…The Direct Fan-Beam topology (DFB) (see e. g. [3], 4) has a triangular replication unit in the XY plane shown in Figure 4. The full x-ray beam, indicated by the shaded area, results on stacking many identical triangular units side-to-side with one another.…”

Section: Direct Fan-beam Topology (Dfb)mentioning

confidence: 99%

Experimental comparison of next-generation XD i topologies

et al. 2010

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SALOME (an acronym for Small Angle Lab Operation Measuring Equipment) is a versatile, energy-dispersive x-ray diffraction imaging (XDi) test-bed facility; commissioned, funded and supported by the Transportation Security Laboratory, Atlantic City, USA. In work presented here, SALOME has been used to investigate the photon collection efficiency of three beam topologies that have been proposed for Next-Generation XDi, namely: Direct Fan-beam (DFB); Parallel Beam (PB); and Inverse Fan-beam (IFB).The single channel replication unit for each of the three topologies was implemented on SALOME. The apertures defining each topology were varied in width, influencing both the detector scatter signal and the momentum resolution. A small powder graphite sample was used as reference object for these measurements, as it provided simultaneous data on counting rate as well as peak resolution for the selected Bragg peak. The photon collection efficiencies at constant momentum peak width for the DFB, PB and IFB topologies were found to follow the trend (from lowest to highest, respectively) conjectured elsewhere in the scientific literature.The basic structure of SALOME is illustrated in Figure 1. The x-ray source is a commercially-available rotating anode electron impact x-ray source operable up to 160 kV and 12 kW DC. The source is supported on a demountable table that is accurately aligned relative to the apertures defining the primary and scatter x-ray beams; thus enabling the radiation source to be exchanged without affecting system alignment. The two primary beam apertures P1 and P2 define a primary beam propagating in the XY plane. The object to be analyzed is mounted on a table whose position in the YZ plane can be moved under computer control. The secondary collimators and spectroscopic detector are mounted on a cantilever table whose angle relative to the primary beam plane can be varied from 0° to 10°. The secondary collimators S1 and S2 define a scatter beam that intersects the primary beam in the sensitive region of the device, where the scatter voxel is located. The fulcrum of the cantilever table is designed to intersect the object table at the scatter voxel so that a change in angle of scatter does not affect the location of the material under investigation. A variety of spectroscopic detectors, including cryostatically cooled germanium as well as room temperature semiconductors such as CdTe and CdZnTe can be mounted on the cantilever table for the purpose of recording energy-dispersive XRD profiles. SALOME was designed to enable spatially resolved, energy-dispersive XRD profiles to be acquired under controlled, variable conditions including: angle of scatter, θ; x-ray source accelerating potential; dimensions of apertures defining the primary and scatter beams; attenuation characteristics; and multiple scatter degradation. In order to minimize the time taken for data acquisition a measurement topology was sought that maximized the photon throughput. As will be seen below, the photon throughput can be increased by t...

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“…It is the low intensity of the scattered signatures that has been a significant factor limiting the use of coherently scattered photons for direct imaging applications. Constructing images from diffracted X-rays is based almost exclusively upon energy dispersive approaches [2,3,4] although detector resolution may ultimately impose a specificity limit, especially for screening applications. This paper reports, for the first time, the initial investigation of a powerful new material specific direct imaging technique, which is tuned to detect and identify highly distributed threat materials such as sheet explosives (whether plastic, amorphous or liquid), and drugs.…”

Section: Introductionmentioning

confidence: 99%

3D X-ray diffraction imaging for materials ID

Evans

Rogers

2010

2010 IEEE International Conference on Technologies for Homeland Security (HST)

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We present a 3D imaging technique, which combines the novel acquisition of diffracted X-ray signals and X-ray absorption data. The relatively high intensity of the diffraction signals afforded by our new approach has important implications for high specificity and high sensitivity security scanning applications.Our technique utilises a configuration of a tubular X-ray beam incident upon a ring absorption sensor and a diffraction sensor. The relative translation of the object under inspection enables the 3D scanning of extended objects. The sensing arrangement focuses on planes normal to the symmetry axis of the interrogating X-ray beam. Orders of magnitude increase in the intensity of the diffraction signal is possible in comparison with conventional angular dispersive methods. Our transmission mode approach effects a convergent and therefore inherently compact, diffracted ray geometry. We have undertaken initial testing and evaluation of this concept with various arrangements of objects fabricated from a range of different materials. The synthesis of the absorption and diffraction data is the basis for a new 3D imaging modality.

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X-ray colour imaging

Cited by 35 publications

References 14 publications

Dynamic X‐Ray Diffraction Computed Tomography Reveals Real‐Time Insight into Catalyst Active Phase Evolution

Dynamic X‐Ray Diffraction Computed Tomography Reveals Real‐Time Insight into Catalyst Active Phase Evolution

Experimental comparison of next-generation XD i topologies

3D X-ray diffraction imaging for materials ID

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