I12-JEEP: Joint Engineering, Environmental and Processing
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Leon
Brown
,
Rema
Abdulaziz
,
Rhodri
Jervis
,
Vidal
Bharath
,
Thomas J.
Mason
,
Robert C.
Atwood
,
Christina
Reinhard
,
Leigh
Connor
,
Douglas
Inman
,
Daniel J. L.
Brett
,
Paul R.
Shearing
Diamond Proposal Number(s):
[9690]
Abstract: A novel electrochemical cell has been designed and built to allow for in situ energy-dispersive X-ray diffraction measurements to be made during reduction of UO2 to U metal in LiCl–KCl at 500°C. The electrochemical cell contains a recessed well at the bottom of the cell into which the working electrode sits, reducing the beam path for the X-rays through the molten-salt and maximizing the signal-to-noise ratio from the sample. Lithium metal was electrodeposited onto the UO2 working electrode by exposing the working electrode to more negative potentials than the Li deposition potential of the LiCl–KCl eutectic electrolyte. The Li metal acts as a reducing agent for the chemical reduction of UO2 to U, which appears to proceed to completion. All phases were fitted using Le Bail refinement. The cell is expected to be widely applicable to many studies involving molten-salt systems.
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Mar 2017
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[5781]
Abstract: Dual phase alloys containing Cr-Laves phases have been considered as potential candidates for high temperature service. In this paper, the effect of Si additions on site occupancies in Cr–Cr2Ta alloys has been studied. Calculations using density functional theory predict that Si substitutes for the Cr atoms rather than Ta within the structure and that Si and Cr are relatively free to occupy 2a and 6h sites interchangeably. However, slight non-uniformity in the 6h Si–Cr minimum charge density and bond length leads to Si favouring 2a occupation within C14 (Cr2−xSix)Ta. These predictions were supported by studies using high-resolution synchrotron X-ray powder diffraction. The effect of quaternary additions on the microstructures and elevated temperature oxidation characteristics of Cr–Ta–Si–X alloys, where X = Ag, Ti, Hf, Mo, Al and Re have also been investigated. The microstructure of the alloys comprised primarily of a eutectic mixture of a Cr-rich solid solution and Cr2Ta-based Laves phase along with primary dendrites of C14 Cr2Ta. Upon isothermal exposure of the alloys for 100 h at 1000 °C, the Re-containing alloy was found to possess the best oxidation resistance, followed by the Hf-containing alloy. The alloys exhibited a significantly superior oxidation resistance at 800 °C owing to the formation of an adherent chromia layer. The oxidation behaviour of the alloys could be described using a combination of linear and parabolic growth laws.
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May 2014
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I11-High Resolution Powder Diffraction
I15-Extreme Conditions
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Diamond Proposal Number(s):
[8614, 8692]
Abstract: The production of amorphous pyroxene nanoparticles (~20 nm) with controlled Fe-Mg content is described. Homogenous
particle compositions closely matching required target stoichiometries are obtained by drying a precursor
gel under high vacuum conditions. The silicate nature of the particles is characterised using TEM,
synchrotron radiation and FTIR. No oxide phase separation occurs, even at high Fe concentration. Structural domains
exist within the nanoparticles that are typically ten times smaller than the physical particle size consistent
with either a core-shell, or, random network with multiple embedded domains, particle structure. Thermal annealing
below the crystallisation temperature allows the ordered domain size to be further reduced by a factor
of ~2.
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Sep 2016
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[23985]
Abstract: A study on the hydration behavior of fluconazole demonstrates that both sample age and polymorphic form impact the drug’s kinetic stability to hydration. For two of the polymorphs, aged samples were found to hydrate more readily than fresh samples. The aging effect was attributed to the formation of monohydrate (MH) crystals over time. The MH, despite being initially undetectable, had a seeding effect, thus impacting the hydration kinetics.
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Mar 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: In-situ synchrotron X-ray powder diffraction (SXRD) was performed on a Li-Si pouch cell on the high-energy beamline (I12) at Diamond Light Source. The high photon energies provided by the synchrotron allowed the beam to pass directly through the Li-Si pouch cell while still providing high resolution SXRD data. Furthermore, the large flux of the synchrotron beam allows high temporal resolution SXRD data to be collected. Fast acquisition time and high resolution SXRD patterns allows for accurate identification of the onset of Li15Si4 formation.
Obrovac and Christensen [1] showed that the fully lithiated phase for silicon at room temperature is Li15Si4. They also showed that the Li15Si4 phase is formed below 50 mV (vs. Li), which typically occurs at the end of silicon lithiation. Li and Dahn [2] used in-situ XRD to show that the Li15Si4 phase does not occur until high capacity (> 3500 mAh/g) and low voltage (< 50 mV).
The results discussed above clearly show that formation of the Li15Si4 phase can be capacity dependent. One could also theorize that the formation of Li15Si4 is voltage dependent. To further elucidate the effect of voltage on the formation of the Li15Si4 phase in-situ SXRD was performed on Li-Si cells at voltages below 50 mV.
In-situ SXRD data is shown in Figure 1 as a function of intensity (left ordinate) and as a waterfall plot vs. time (right ordinate).
Figure 1 clearly shows that the silicon peak recedes as a function of time (and capacity), while the Li15Si4peak grows.
To better quantify the formation of the Li15Si4 phase Figure 2 shows the evolution of the volume fraction of Li15Si4 as a function of time (lower plot abscissa) and capacity (upper plot ordinate).
Figure 2 shows that the Li15Si4 phase can be observed almost immediately. As capacity increases the volume fraction of Li15Si4 continues to increase. These results show that the Li15Si4phase can be formed very early if the voltage at the silicon electrode is below 50 mV.
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Jun 2014
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I12-JEEP: Joint Engineering, Environmental and Processing
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L D
Brown
,
Rema
Abdulaziz
,
Rhodri
Jervis
,
Vidal
Bharath
,
R C
Attwood
,
Christina
Reinhard
,
Leigh
Connor
,
S J R
Simons
,
D.
Inman
,
D J L
Brett
,
Paul
Shearing
Diamond Proposal Number(s):
[9690]
Open Access
Abstract: The electrochemical reduction of uranium dioxide to metallic uranium has been investigated in lithium chloridepotassium chloride eutectic molten salt. Laboratory based electrochemical studies have been coupled with in situ energy dispersive X-ray diffraction, for the first time, to deduce the reduction pathway. No intermediate phases were identified using the X-ray diffraction before, during or after electroreduction to form α-uranium. This suggests that the electrochemical reduction occurs via a single, 4-electron-step, process. The rate of formation of α-uranium is seen to decrease during electrolysis and could be a result of a build-up of oxygen anions in the molten salt. Slow transport of O2− ions away from the UO2 working electrode could impede the electrochemical reduction.
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Sep 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Michael
Drakopoulos
,
Thomas
Connolley
,
Christina
Reinhard
,
Robert
Atwood
,
Oxana
Magdysyuk
,
Nghia
Vo
,
Mike
Hart
,
Leigh
Connor
,
Bob
Humphreys
,
George
Howell
,
Steve
Davies
,
Tim
Hill
,
Guy
Wilkin
,
Ulrik
Pedersen
,
Andrew
Foster
,
Nicoletta
De Maio
,
Mark
Basham
,
Fajin
Yuan
,
Kaz
Wanelik
Open Access
Abstract: I12 is the Joint Engineering, Environmental and Processing (JEEP) beamline,
constructed during Phase II of the Diamond Light Source. I12 is located on
a short (5 m) straight section of the Diamond storage ring and uses a 4.2 T
superconducting wiggler to provide polychromatic and monochromatic X-rays
in the energy range 50150 keV. The beam energy enables good penetration
through large or dense samples, combined with a large beam size (1 mrad
horizontally x 0.3 mrad vertically). The beam characteristics permit the study of
materials and processes inside environmental chambers without unacceptable
attenuation of the beam and without the need to use sample sizes which are
atypically small for the process under study. X-ray techniques available to users
are radiography, tomography, energy-dispersive diffraction, monochromatic
and white-beam two-dimensional diffraction/scattering and small-angle X-ray
scattering. Since commencing operations in November 2009, I12 has established
a broad user community in materials science and processing, chemical
processing, biomedical engineering, civil engineering, environmental science,
palaeontology and physics.
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May 2015
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: For high performance, safety-critical applications, such as aerospace components, in-depth understanding of the material\u2019s response to complex loading conditions is essential. Moreover, it is vital to know how the material behaviour may be modified as a consequence of fatigue loading and how its eventual failure occurs. Unlike bulk properties, such as stiffness, yield stress, etc. that depend on the average response of the grains in a polycrystal, material failure is determined by \u201cweakest link\u201d type mechanisms. These depend strongly on grain-level deformation behaviour and grain-to-grain interactions. Micro-beam Laue diffraction is a powerful tool to probe these phenomena. However, the classical setup is limited to the study of sample surface regions or thin sections, due to the limited penetration into the sample at photon energies of 5 \u2013 25 keV. A much more useful tool for the material scientist and engineer would allow the probing of grain-level orientation and stress in thicker sections of engineering components. To this end, we have developed the high energy transmission Laue (HETL) technique, an extension of the micro-beam Laue technique to significantly higher photon energies (50 \u2013 150 keV). For the imaging of lattice orientation and elastic strain in three dimensions, we propose two alternative approaches: Laue orientation tomography (LOT) and high energy differential aperture X-ray microscopy (HEDAXM). In this paper an overview of the recent progress in HETL, LOT and HEDAXM measurements will be given and some first results illustrating the potential of these techniques presented.
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Feb 2012
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Open Access
Abstract: A typical heat treatment for a low alloy steel will often involve a quenching heat treatment step, in which the steel is cooled from high temperatures to trigger austenite decomposition. The particular cooling rate during the quenching step can have a marked influence on the phase transformations taking place, and the resulting steel microstructure and mechanical properties. Although methods such as dilatometry have been available for many decades to characterise continuous-cooling transformation (CCT) behaviour in steels, the use of in situ synchrotron X-ray diffraction (SXRD) to elucidate CCT behaviour in a systematic way has not been reported.
In this work, we measure the CCT behaviours of two pressure vessel steels in situ using simultaneous dilatometry and SXRD. Both steels are subject to austenitisation followed by quenching at a range of cooling rates. On comparing results from SXRD and dilatometry, it is found that recorded starts of transformations appear to be in good agreement. However, calculations of phase fractions derived from dilatometry data significantly overestimate the fraction of ferrite that forms in comparison to SXRD when the formation involves the partitioning of carbon. This happens for two reasons: first, because the method to extract ferrite volume fractions from dilatometry data generally ignores the presence of any retained austenite at low temperatures, and second, because analyses of dilatometry data do not account for the expansion of the austenite during transformation due to enrichment in carbon. This enrichment leads to an increase in strain, and the standard analysis method falsely attributes this increase to ferrite formation, thereby overestimating it. The results highlight that caution must be exercised when interpreting the results of dilatometry, since levels of ferrite (especially diffusively-formed) and retained austenite are important quantities for the prediction of mechanical behaviour, and they are not readily quantified by the analysis of dilatometry data alone.
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May 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[13173]
Open Access
Abstract: The new long duration experiment facility on beamline I11 at Diamond Light Source has been used to study the kinetics of sigma phase formation in three Cr–Co–Ni alloys. Diffraction data acquired during in situ exposure at 800°C for 50 d showed progressive increases in the sigma fraction. This was accompanied by changes in the proportions of the other phases, which differed markedly between the alloys studied. These results demonstrate the capabilities of the long duration facility for the study of metallurgical phenomena over periods of months to years, a capability not previously available at a synchrotron source.
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Sep 2018
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