I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[18468]
Open Access
Abstract: There are several mechanisms contributing towards detrimental damage in wind turbine gearbox bearings, with sudden overload events believed to reduce their expected operational life. The generation of subsurface plasticity, followed by rolling contact fatigue, may lead to the initiation of either surface or subsurface cracking. This study presents a novel technique capable of measuring subsurface strain evolution in a rotating roller bearing, using energy dispersive X-ray diffraction. A pre-overloaded bearing was tested dynamically and consequently failed prematurely, supporting the hypothesis that overloads accelerate bearing failure. Throughout the test, an increase in compressive radial strain was observed, indicative of material softening, generally associated with the unstable stage of rolling contact fatigue, which occurs prior to definitive bearing failure.
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Dec 2019
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[14465]
Abstract: Tb for Ca substituted hydroxyapatite ceramic samples with composition Ca10−xTbx(PO4)6(OH1−x/2−δ)2, where x = 0.1, 0.5, were synthesized by solid-state reaction at 1300 °C in air, and their crystal structure, vibrational spectra, luminescence, and magnetic properties were studied. Implanting Tb3+ into the calcium apatite crystal lattice results in formation of an effective TbO+ ion which displays a short terbium–oxygen bond of 2.15 Å and a stretching vibration at 534 cm−1. The Tb3+ electronic structure has been revealed by analyzing the luminescence spectra and dc/ac magnetization data. Accordingly, the ground state represents a pseudo doublet with MJ = ±6 and the first exited level is by 112 cm−1 higher in energy. The ion exhibits field induced magnetic bistability with the magnetization reversing over the first exited state. Three paths of magnetization relaxation with field-temperature controlled switching between the paths have been identified.
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Mar 2019
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: Controlling the final grain size in a uniform and controlled manner in powder metallurgy nickel-based superalloys is important since many mechanical properties are closely related to it. However, it has been widely documented that powder metallurgy superalloys are prone to suffer from growth of abnormally large grains (ALGs) during supersolvus heat treatment, which is harmful to in-service mechanical performance. The underlying mechanisms behind the formation of ALGs are not yet fully understood. In this research, ALGs were intentionally created using spherical indentation applied to a polycrystalline nickel-based superalloy at room temperature, establishing a deformation gradient underneath the indentation impression, which was quantitatively determined using finite element modelling, electron backscatter diffraction (EBSD) and synchrotron diffraction. Subsequent supersolvus heat treatment leads to the formation of ALGs in a narrow strain range, which also coincides with the contour of residual plastic strain in a range of about 2% to 10%. The formation mechanisms can be attributed to: (1) nucleation sites available for recrystallization are limited, (2) gradient distribution of stored energy across grain boundary. The proposed mechanisms were validated by the phase-field simulation. This research provides a deeper insight in understanding the formation of ALGs in polycrystalline nickel-based superalloy components during heat treatment, when subsurface plastic deformation caused by (mis)handling before super-solvus heat treatment occurs.
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Feb 2019
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I12-JEEP: Joint Engineering, Environmental and Processing
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Hamish
Yeung
,
Adam F.
Sapnik
,
Felicity
Massingberd-mundy
,
Michael W.
Gaultois
,
Yue
Wu
,
Duncan X.
Fraser
,
Sebastian
Henke
,
Roman
Pallach
,
Niclas
Heidenreich
,
Oxana
Magdysyuk
,
Nghia T.
Vo
,
Andrew L.
Goodwin
Diamond Proposal Number(s):
[16354, 16450]
Abstract: There is an increasingly large amount of interest in metal‐organic frameworks (MOFs) for a variety of applications, from gas sensing and separations to electronics and catalysis. Their exciting properties arise from their modular architectures, which self‐assemble from different combinations of metal‐based and organic building units. However, the exact mechanisms by which they crystallize remain poorly understood, thus limiting any realisation of real “structure by design”. We report important new insight into MOF formation, gained using in situ X‐ray diffraction, pH and turbidity measurements to uncover for the first time the evolution of metastable intermediate species in the canonical zeolitic imidazolate framework system, ZIF‐8. We reveal that the intermediate species exist in a dynamic pre‐equilibrium prior to network assembly and, depending on the reactant concentrations and the progress of reaction, the pre‐equilibrium can be made to favour under‐ or over‐coordinated Zn‐imidazolate species, thus accelerating or inhibiting crystallization, respectively. We thereby find that concentration can be effectively used as a synthetic handle to directly control particle size, with great implications for industrial scale‐up and gas sorption applications. These finding enables us to rationalise the apparent contradictions between previous studies of ZIF‐8 and, importantly, opens up new opportunities for the control of crystallization in network solids more generally, from the design of local structure to assembly of particles with precise dimensions.
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Nov 2018
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[10283]
Abstract: The internal structure and cross-sectional geometry of fiber-like poly(3-hexylthiophene)-based block copolymer micelles has been determined using small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) techniques alongside electron and atomic force microscopies. WAXS of concentrated micellar solutions demonstrated that the block copolymers form crystalline-core micelles in solvents selective for the corona-forming block. Furthermore, by generating macroscopic fibers from micellar solutions, it was possible to align the micelles and discern the type and orientation of the unit cell within the core. Using the unit cell information gained from the wide-angle measurements, in conjunction with the structural insights gained from the microscopy techniques, it was possible to form a complete picture of the cross-sectional geometry of the micelles, whereby the polymer chains lie perpendicular to the long axis of the micelle core and do not undergo chain folding. Finally, this information was used to propose a self-assembly mechanism and to construct and validate a model for the small-angle scattering data, revealing the inherent flexibility of the micelles.
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Apr 2018
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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: Characterization of semi and noncrystalline materials, monitoring structural phase transitions in situ, and obtaining structural information together with spatial distribution of the investigated material are only a few applications that hugely benefitted from the combination of high-energy X-rays and modern algorithms for data processing. This work examines the possibility of advancing these applications by shortening the data acquisition and improving the data quality by using the new high-energy PILATUS3 CdTe detector.
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Dec 2017
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[14465]
Abstract: Pure-phase cobalt-doped calcium hydroxyapatite ceramic samples with composition Ca10(PO4)6[(CoO2)x(OH)1–2x]2, where x = 0–0.2, were synthesized by high-temperature solid-state reaction, and their crystal structures, vibrational spectra, and magnetic properties were studied. Co atoms are found to enter into the apatite trigonal channel formally substituting H atoms and forming bent dioxocobaltate(II) anions. The anion exhibits single-molecule-magnet (SMM) behavior: slow relaxation of magnetization below 8 K under a nonzero magnetic field with an energy barrier of 63 cm–1. The barrier value does not depend on the concentration of Co ions, virtually coincides with the zero-field-splitting energy as determined from direct-current magnetization, and is very close to the value obtained earlier for cobalt-doped strontium hydroxyapatite. Moreover, the vibration frequencies of the dioxocobaltate(II) anion are found to be the same in calcium and strontium apatite matrixes. The very weak dependence of the SMM parameters on the matrix nature in combination with good chemical and thermal stabilities of the compounds provides wide opportunities to exploit the intrinsic properties of such a SMM-like anion.
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Nov 2017
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I12-JEEP: Joint Engineering, Environmental and Processing
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Donal P.
Finegan
,
Eric
Darcy
,
Matthew
Keyser
,
Bernhard
Tjaden
,
Thomas M. M.
Heenan
,
Rhodri
Jervis
,
Josh J.
Bailey
,
Nghia T.
Vo
,
Oxana V.
Magdysyuk
,
Michael
Drakopoulos
,
Marco Di
Michiel
,
Alexander
Rack
,
Gareth
Hinds
,
Dan J. L.
Brett
,
Paul
Shearing
Diamond Proposal Number(s):
[13884]
Open Access
Abstract: As the energy density of lithium-ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra-high-speed synchrotron X-ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs.
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Oct 2017
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Abstract: Meeting the challenges of Moore´s Law, predicting ambitious miniaturization rates of integrated circuits, requires to go beyond the traditional top down approaches, and to employ synthetic chemistry methods, to use bottom-up techniques. During the recent decades, it has been demonstrated that open shell coordination compounds may exhibit intra-molecular spontaneous magnetization, thus offering promising prospects for storage and processing of digital information. Against this background we regarded it rewarding to implement similar magnetic centers into a ceramic material, which would provide better long term mechanical and chemical durability. Here we present new robust inorganic compounds containing separate DyO+ ions in an apatite matrix, which behave like single-molecule magnets. The materials exhibit a blocking temperature of 11 K and an energy barrier for spin reversal of a thousand cm-1 which is among the highest values ever achieved.
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Sep 2017
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I12-JEEP: Joint Engineering, Environmental and Processing
I16-Materials and Magnetism
I22-Small angle scattering & Diffraction
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J.
Filik
,
A. W.
Ashton
,
P. C. Y.
Chang
,
P. A.
Chater
,
S. J.
Day
,
M.
Drakopoulos
,
M. W.
Gerring
,
M. L.
Hart
,
O. V.
Magdysyuk
,
S.
Michalik
,
A.
Smith
,
C. C.
Tang
,
N. J.
Terrill
,
M. T.
Wharmby
,
H.
Wilhelm
Diamond Proposal Number(s):
[12735, 10311]
Abstract: software package for the calibration and processing of powder X-ray diffraction and small-angle X-ray scattering data is presented. It provides a multitude of data processing and visualization tools as well as a command-line scripting interface for on-the-fly processing and the incorporation of complex data treatment tasks. Customizable processing chains permit the execution of many data processing steps to convert a single image or a batch of raw two-dimensional data into meaningful data and one-dimensional diffractograms. The processed data files contain the full data provenance of each process applied to the data. The calibration routines can run automatically even for high energies and also for large detector tilt angles. Some of the functionalities are highlighted by specific use cases.
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Jun 2017
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