I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[36212]
Abstract: Fe-rich intermetallic compounds (IMCs) are a persistent challenge in the recirculation of secondary aluminium alloys. Despite significant research effort, largely via post-solidification studies, the mechanisms governing IMC phase selection in higher-Fe (
wt.%), recycled Al alloys and how they can be controlled to facilitate more benign IMC species and/or morphologies remain poorly understood. This creates barriers to compositional and process design for more Fe-tolerant alloys. In this paper, we present a systematic real-time investigation of IMC formation, phase selection and morphological evolution in recycled 3xx series Al alloys with elevated Fe concentrations (up to 2.5 wt%), using in situ synchrotron X-ray radiography. Coupled with thermodynamic simulations, we develop a method to reliably estimate the formation temperatures of primary
-AlFeSi and
-AlFeSi IMCs, and show direct insights into their formation sequence and kinetics. Contrary to widely held assumptions based on low Fe-containing (
0.6 wt%) primary alloys, we show that in recycled alloys containing higher Fe concentrations, increased cooling rate significantly promotes the formation of the more anisotropic
-AlFeSi (over the more compact
-AlFeSi), which however can be fully suppressed at slow cooling. We propose how a solute-suppression mechanism kinetically controls the
/
IMC phase evolution. Further, we reveal and quantify a faceted-to-non-faceted morphological transition of
-AlFeSi from a faceted polyhedral to non-faceted near-equiaxed dendritic morphology. This transition is governed by an interplay between solidification velocity and liquid undercooling at the local IMC/liquid interfaces. This study provides insights into how solidification conditions may be leveraged to improve microstructural control in high Fe-containing recycled alloys.
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Oct 2025
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I13-2-Diamond Manchester Imaging
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Dominic L. R.
Melvin
,
Marco
Siniscalchi
,
Dominic
Spencer-Jolly
,
Bingkun
Hu
,
Ziyang
Ning
,
Shengming
Zhang
,
Junfu
Bu
,
Shashidhara
Marathe
,
Anne
Bonnin
,
Johannes
Ihli
,
Gregory J.
Rees
,
Patrick S.
Grant
,
Charles W.
Monroe
,
T. James
Marrow
,
Guanchen
Li
,
Peter G.
Bruce
Diamond Proposal Number(s):
[30683]
Open Access
Abstract: Avoiding lithium dendrites at the lithium/ceramic electrolyte interface and, as a result, avoiding cell short circuit when plating at practical current densities remains a significant challenge for all-solid-state batteries. Typically, values are limited to around 1 mA cm−2, even, for example, for garnets with a relative density of >99%. It is not obvious that simply densifying ceramic electrolytes will deliver high plating currents. Here we show that plating currents of 9 mA cm−2 can be achieved without dendrite formation, by densifying argyrodite, Li6PS5Cl, to 99%. Changes in the microstructure of Li6PS5Cl on densification from 83 to 99% were determined by focused ion beam-scanning electron microscopy tomography and used to calculate their effect on the critical current density (CCD). Modelling shows that not all changes in microstructure with densification act to increase CCD. Whereas smaller pores and shorter cracks increase CCD, lower pore population and narrower cracks act to decrease CCD. Calculations show that the former changes dominate over the latter, predicating an overall increase in CCD, as observed experimentally.
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Sep 2025
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I15-1-X-ray Pair Distribution Function (XPDF)
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[35064, 39285, 40912]
Open Access
Abstract: Li-rich disordered rocksalts are promising next-generation cathode materials for Li-ion batteries. Recent reports have shown it is also possible to obtain Na-rich disordered rocksalts, however, it is currently poorly understood how the knowledge of the structural and redox chemistry translates from the Li-rich to the Na-rich analogs. Here, the properties of Li2MnO2F and Na2MnO2F are compared, which have different ion sizes (Li+ = 0.76 vs Na+ = 1.02 Å) but the same disordered rocksalt structure and stoichiometry. It is found that Na2MnO2F exhibits lower voltage Mn- and O-redox couples, opening access to a wider compositional range within the same voltage limits. Furthermore, the intercalation mechanism switches from predominantly single-phase solid solution behavior in Li2MnO2F to a two-phase transition in Na2MnO2F, accompanied by a greater decrease in the average Mn─O/F bond length. Li2MnO2F retains its long-range disordered rocksalt structure throughout the first cycle. In contrast, Na2MnO2F becomes completely amorphous during charge and develops a local structure characteristic of a post-spinel. This amorphization is partially reversible on discharge. The results show how the ion intercalation behavior of disordered rocksalts differs dramatically when changing from Li- to Na-ions and offers routes to control the electrochemical properties of these high-energy-density cathodes.
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May 2025
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I13-2-Diamond Manchester Imaging
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Ziyang
Ning
,
Guanchen
Li
,
Dominic L. R.
Melvin
,
Yang
Chen
,
Junfu
Bu
,
Dominic
Spencer-Jolly
,
Junliang
Liu
,
Bingkun
Hu
,
Xiangwen
Gao
,
Johann
Perera
,
Chen
Gong
,
Shengda D.
Pu
,
Shengming
Zhang
,
Boyang
Liu
,
Gareth O.
Hartley
,
Andrew J.
Bodey
,
Richard I.
Todd
,
Patrick S.
Grant
,
David E. J.
Armstrong
,
T. James
Marrow
,
Charles W.
Monroe
,
Peter G.
Bruce
Diamond Proposal Number(s):
[23980]
Abstract: All-solid-state batteries with a Li anode and ceramic electrolyte have the potential to deliver a step change in performance compared with today’s Li-ion batteries1,2. However, Li dendrites (filaments) form on charging at practical rates and penetrate the ceramic electrolyte, leading to short circuit and cell failure3,4. Previous models of dendrite penetration have generally focused on a single process for dendrite initiation and propagation, with Li driving the crack at its tip5,6,7,8,9. Here we show that initiation and propagation are separate processes. Initiation arises from Li deposition into subsurface pores, by means of microcracks that connect the pores to the surface. Once filled, further charging builds pressure in the pores owing to the slow extrusion of Li (viscoplastic flow) back to the surface, leading to cracking. By contrast, dendrite propagation occurs by wedge opening, with Li driving the dry crack from the rear, not the tip. Whereas initiation is determined by the local (microscopic) fracture strength at the grain boundaries, the pore size, pore population density and current density, propagation depends on the (macroscopic) fracture toughness of the ceramic, the length of the Li dendrite (filament) that partially occupies the dry crack, current density, stack pressure and the charge capacity accessed during each cycle. Lower stack pressures suppress propagation, markedly extending the number of cycles before short circuit in cells in which dendrites have initiated.
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Jun 2023
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I12-JEEP: Joint Engineering, Environmental and Processing
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Dominic
Spencer-Jolly
,
Varnika
Agarwal
,
Christopher
Doerrer
,
Bingkun
Hu
,
Shengming
Zhang
,
Dominic L. R.
Melvin
,
Hui
Gao
,
Xiangwen
Gao
,
Paul
Adamson
,
Oxana
Magdysyuk
,
Patrick S.
Grant
,
Robert A.
House
,
Peter G.
Bruce
Diamond Proposal Number(s):
[26082]
Open Access
Abstract: Ag-carbon composite interlayers have been reported to enable Li-free (anodeless) cycling of solid-state batteries. Here, we report structural changes in the Ag-graphite interlayer, showing that on charge, Li intercalates electrochemically into graphite, subsequently reacting chemically with Ag to form Li-Ag alloys. Discharge is not the reverse of charge but rather passes through Li-deficient Li-Ag phases. At higher charging rates, Li intercalation into graphite outpaces the chemical reactions with Ag, delaying the formation of the Li-Ag phases and resulting in more Li metal deposition at the current collector. At and above 2.5 mA·cm−2, Li dendrites are not suppressed. Ag nanoparticles do not suppress dendrites more effectively than does an interlayer of graphite alone. Instead, Ag in the carbon interlayer results in more homogeneous Li and Li-Ag formation on the current collector during charge.
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Feb 2023
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B16-Test Beamline
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Diamond Proposal Number(s):
[9140]
Abstract: Despite the well-known importance of controlling shrinkage-induced liquid flow in alloy castings to avoid the formation of catastrophic hot tears during the final stages of solidification, there has been little direct experimental measurement of liquid metal flow and hot tear formation under practical conditions. We use synchrotron X-rays to obtain radiographic video sequences of the solidification of monotectic Al-Pb alloys in which Pb droplets form as a fine-scale emulsion. We track and measure the velocity of thousands of Pb droplets as they move through interdendritic regions due to the effect of liquid to solid shrinkage during the final stages of solidification, up to the point of hot tear formation. Based on the droplet velocities, we present an analysis to estimate the interdendritic liquid velocity as solid fraction increases, and thus the shrinkage pressure drop driving the flow. The analysis is applied for video sequences obtained for both equiaxed and columnar microstructures, each under a range of cooling rates. Our measurements of the critical shrinkage-induced pressure for hot tear formation agree well with prior model-based and theoretical suggestions. The limitations and prospects for droplet tracking measurements of liquid metal flows are discussed.
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Aug 2022
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B16-Test Beamline
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Diamond Proposal Number(s):
[7440, 7818, 8191, 9140]
Open Access
Abstract: In the last two decades, X-ray imaging techniques have been used increasingly to study metal solidification in real-time as, thanks to advances in X-ray sources (synchrotron and laboratory-based) and detector technology, images can now be obtained with spatio-temporal resolutions sufficient to record key phenomena and extract quantitative information, primarily relating to crystal growth. This paper presents an overview of the research conducted at the University of Oxford over the last 6 years as a partner in the UK’s Future Liquid Metal Engineering (LiME) Manufacturing Hub. The focus is on in situ X-ray radiography to investigate the solidification of Al alloys, including the formation of primary α
-Al crystals, and the formation and growth of secondary intermetallic phases. Technologically, the thrust is to understand how to control as-cast phases, structures and element distributions, particularly elements associated with recycling, as a means to facilitate greater recirculation of aluminium alloys. We first present studies on refinement of primary α
-Al, including extrinsic grain refinement using inoculation and intrinsic refinement based on dendrite fragmentation. Second, we describe studies on intermetallic phase formation and growth, because intermetallic fraction, morphology and distribution are frequently a limiting factor of alloy mechanical properties and recyclability. Then we present some of the latest progress in studying liquid flow during solidification and associated hot tear formation. Finally, future research directions are described.
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Feb 2022
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[22976]
Open Access
Abstract: Bragg edge tomography was carried out on novel, ultra-thick, directional ice templated graphite electrodes for Li-ion battery cells to visualise the distribution of graphite and stable lithiation phases, namely LiC12 and LiC6. The four-dimensional Bragg edge, wavelength-resolved neutron tomography technique allowed the investigation of the crystallographic lithiation states and comparison with the electrode state of charge. The tomographic imaging technique provided insight into the crystallographic changes during de-/lithiation over the electrode thickness by mapping the attenuation curves and Bragg edge parameters with a spatial resolution of approximately 300 µm. This feasibility study was performed on the IMAT beamline at the ISIS pulsed neutron spallation source, UK, and was the first time the 4D Bragg edge tomography method was applied to Li-ion battery electrodes. The utility of the technique was further enhanced by correlation with corresponding X-ray tomography data obtained at the Diamond Light Source, UK.
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Dec 2020
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[9974]
Open Access
Abstract: The spray forming of thick, dissimilar steel clad tubes with the objective of achieving a high integrity metallurgical bond across the cladding-substrate interface able to withstand residual stresses and subsequent thermo-mechanical processing was investigated by large scale experiments, modelling and extensive microstructural characterization including microscopy, X-ray tomography, neutron scattering and mechanical testing. The simulated residual stress distributions across the cladding-substrate interface, accounting for any as-sprayed porosity and the distribution of martensitic and retained austenite phases, were compared with neutron diffraction measurements and differences used to infer the load transfer behaviour and thus the mechanical integrity of the interface. The mechanical properties of the interfaces were then also measured directly by shear testing. The link between substrate pre-heating, the spray forming temperature, and the resulting preform temperature, porosity, phase fractions, residual stress, strength and integrity of the interface were established and quantified explicitly.
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Aug 2018
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B16-Test Beamline
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Diamond Proposal Number(s):
[9140, 8635]
Abstract: A method was developed based on synchrotron X-ray radiography to estimate tip temperatures of 203 Fe-rich intermetallic compound (IMC) particles during directional solidification of Al-Cu-Fe alloys. Tip temperatures showed two distinct IMC populations corresponding to Al6(Fe,Cu) and Al7Cu2Fe, validated by post-solidification microscopy. The IMC tip undercooling of each growing IMC was estimated by comparison with its equilibrium formation temperature. The effect of Fe concentration, cooling rate and grain refiner additions on the IMC tip undercooling was studied. With a large number of IMC particles measured, we show the relationship between solidification parameters, secondary IMC selection and tip undercooling.
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May 2018
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