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80 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Synthesis and thermodynamics of uranium-incorporated α-Fe2O3 nanoparticles Andy Lam , Forrest Hyler , Olwen Stagg , Katherine Morris , Samuel Shaw , Jesús M. Velázquez , Alexandra Navrotsky Journal Of Nuclear Materials 556 DOI: 10.1016/j.jnucmat.2021.153172 Diamond Proposal Number(s): [17243] Show Abstract ▼ Abstract: Hematite nanoparticles were synthesized with U(VI) in circumneutral water through a coprecipitation and hydrothermal treatment process. XRD, TEM, and EXAFS analyses reveal that uranium may aggregate along grain boundaries and occupy Fe sites within hematite. The described synthesis method produces crystalline, single-phase iron oxide nanoparticles absent of surface-bound uranyl complexes. EXAFS data were comparable to spectra from existing studies whose syntheses were more representative of naturally occurring, extended aging processes. This work provides and validates an accelerated method of synthesizing uranium-immobilized iron oxide nanoparticles for further mechanistic studies. High temperature oxide melt solution calorimetry measurements were performed to calculate the thermodynamic stability of uranium-incorporated iron oxide nanoparticles. Increasing uranium content within hematite resulted in more positive formation enthalpies. Standard formation enthalpies of UxFe2–2xO3 were as high as 76.88 ± 2.83 kJ/mol relative to their binary oxides, or -764.04 ± 3.74 kJ/mol relative to their constituent elements, at x = 0.037. Data on the thermodynamic stability of uranium retention pathways may assist in predicting waste uranyl remobilization, as well as in developing more effective methods to retain uranium captured from aqueous environments.	Dec 2021
I12-JEEP: Joint Engineering, Environmental and Processing	In situ synchrotron investigation of degenerate graphite nodule evolution in ductile cast iron T. Wigger , T. Andriollo , C. Xu , S. J. Clark , Z. Gong , R. C. Atwood , J. H. Hattel , N. S. Tiedje , P. D. Lee , M. A. Azeem Acta Materialia 84 DOI: 10.1016/j.actamat.2021.117367 Diamond Proposal Number(s): [22627] Show Abstract ▼ Abstract: Ductile cast irons (DCIs) are of increasing importance in the renewable energy and transportation sectors. The distribution and morphology of the graphite nodules, in particular the formation of degenerate features during solidification, dictate the mechanical performance of DCIs. In situ high-speed synchrotron X-ray tomography was used to capture the evolution of graphite nodules during solidification of DCI, including degenerate features and the effect of the carbon concentration field. The degeneration of nodules is observed to increase with re-melting cycles, which is attributed to Mg-loss. The dendritic primary austenite and carbon concentration gradients in the surrounding liquid phase were found to control nodule morphology by locally restricting and promoting growth. A coupled diffusion-mechanical model was developed, confirming the experimentally informed hypothesis that protrusions form through liquation cracking of the austenite shell and subsequent localised growth. These results provide valuable insights into the solidification kinetics of cast irons, supporting the design of advanced alloys.	Oct 2021
I12-JEEP: Joint Engineering, Environmental and Processing	Synchrotron characterisation of ultra-fine grain TiB2/Al-Cu composite fabricated by laser powder bed fusion Sheng Li , Biao Cai , Ranxi Duan , Lei Tang , Zihan Song , Dominic White , Oxana Magdysyuk , Moataz M. Attallah Acta Metallurgica Sinica (english Letters) 23 DOI: 10.1007/s40195-021-01317-y Diamond Proposal Number(s): [22506] Open Access Show Abstract ▼ Abstract: Isotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.	Sep 2021
B16-Test Beamline	Strain mapping of silicon carbon suspended membranes Gerard Colston , Oliver Newell , Stephen D. Rhead , Vishal A. Shah , Maksym Myronov Materials & Design 55 DOI: 10.1016/j.matdes.2021.110135 Diamond Proposal Number(s): [11773, 10303] Open Access Show Abstract ▼ Abstract: The alloy silicon carbon (Si1-yCy) has various strain engineering applications. It is often implemented as a dopant diffusion barrier and has been identified as a potential buffer layer for cubic silicon carbide (3C-SiC) heteroepitaxy. While suspended membranes formed from thin films of semiconductor (Ge and 3C-SiC) and dielectric (Si3N4) materials have been well studied, pseudomorphic, defect-free epilayers under high levels of tensile strain have received little attention. Often, tensile strain is a desired quality of semiconductors and enhancing this property can lead to various benefits of subsequent device applications. The strain state and crystalline tilt of suspended Si1-yCy epilayers have been investigated through micro-X-ray diffraction techniques. The in-plane tensile strain of the alloy was found to increase from 0.67% to 0.82%. This strain increase could reduce the C content required to achieve suitable levels of strain in such alloys and further strain enhancement could be externally induced. The source of this strain increase was found to stem from slight tilts at the edges of the membranes, however, the bulk of the suspended films remained flat. The novel process utilised to fabricate suspended Si1-yCy thin-films is applicable to many other materials that are typically not resistant to anisotropic Si wet etchants.	Sep 2021
I12-JEEP: Joint Engineering, Environmental and Processing	Unraveling compacted graphite evolution during solidification of cast iron using in-situ synchrotron X-ray tomography Chaoling Xu , Tim Wigger , Mohammed Azeem , Tito Andriollo , Søren Fæster , Samuel Clark , Zhixuan Gong , Robert Atwood , Jean-Claude Grivel , Jesper H. Hattel , Peter D. Lee , Niels S. Tiedje Carbon 141 DOI: 10.1016/j.carbon.2021.08.069 Diamond Proposal Number(s): [22627] Open Access Show Abstract ▼ Abstract: In spite of many years of research, the physical phenomena leading to the evolution of compacted graphite (CG) during solidification is still not fully understood. In particular, it is unknown how highly branched CG aggregates form and evolve in the semi-solid, and how local microstructural variations at micrometer length scale affect this growth process. We present here the first time-resolved synchrotron tomography combined with a bespoke high-temperature environmental cell that allows direct observation of the evolution of CG and relates this dynamic process to the local surrounding microstructures in a cast iron sample during repeated melting and solidification. Distinct processes are identified for the formation of CG involving the nucleation, growth, development of branches and interconnection of graphite particles, ultimately evolving into highly branched graphite aggregates with large sizes and low sphericities. CG is found to nucleate with a spheroidal or a plate-like shape, developing branches induced by high carbon concentration, e.g. thin melt channels. Additionally, CG grows much faster than spheroidal graphite during subsequent cooling in solid state. The direct visualization of the dynamic solidification process provides unprecedented new insights into formation mechanisms of CG and correlating factors such as local microstructural variations, and guides the development of CG iron solidification models.	Sep 2021
I13-2-Diamond Manchester Imaging	Mechanisms of gas and shrinkage porosity formation in solidifying shear bands Shishira Bhagavath , Zhixuan Gong , Tim Wigger , Saurabh Shah , Bita Ghaffari , Mei Li , Shashidhara Marathe , Shyamprasad Karagadde , Peter D. Lee Journal Of Materials Processing Technology 26 DOI: 10.1016/j.jmatprotec.2021.117338 Diamond Proposal Number(s): [22053] Show Abstract ▼ Abstract: In specialised solidification processing techniques such as High Pressure Die Casting, Twin-Roll Casting and others, an additional external deformation load is applied to achieve the required shape, leading to the formation of microstructural features such as shear bands. The mechanism for forming these features is believed to be dependent on dynamically evolving strain fields, which are dependent on the local solid fraction, applied strain rates and casting geometry. To investigate this, a semisolid ( 50 % solid fraction) Al-10 wt.% Cu alloy is isothermally injected into a bespoke die using a custom-designed thermo-mechanical rig. The semisolid deformation, formation of Cu-rich dilatant bands and subsequent pore nucleation and growth are captured using fast synchrotron X-ray radiography. The local normal and shear strains acting on the mush are quantified using Digital image correlation to identify the dilatant shear bands and the dominant local strain component. Correlating the radiographs with strain maps reveals that gas pores within the dilated interstices grow, while those in compressed regions are squeezed out. A linear correlation between accumulated volumetric strain and porosity volume fraction demonstrates that higher dilations give rise to a local increase in both gas and shrinkage porosity.	Aug 2021
I15-Extreme Conditions	The correlation between X-ray scattering structure factor and shear bands density of a metallic glass and a composite C. Zhang , T.-L. Lee , J. C. Khong , J.c. Qiao , D. Daisenberger , Y. Yao , J. Mi Materials Letters 304 DOI: 10.1016/j.matlet.2021.130727 Diamond Proposal Number(s): [9902, 8858] Show Abstract ▼ Abstract: The tensile fractured surfaces of ZrTi-based bulk metallic glass and composite samples were studied using synchrotron X-ray total scattering. The scanned areas contain different shear bands densities. The shear bands create localized atomic strains, which in turn cause more ordered atomic structures. Such structural changes were reflected in the scattering structure factor, i.e. the higher the density of the shear bands, the higher the scattering structure factor. Similar phenomenon was also found in the metallic glass composite.	Aug 2021
I11-High Resolution Powder Diffraction	Effects of vacuum on gas content, oxide inclusions and mechanical properties of Ni-based superalloy using electron-beam button and synchrotron diffraction Liang Zheng , Guoqing Zhang , Michael Gorley , Tung Lik Lee , Zhou Li , Chengbo Xiao , Chiu C. Tang Materials & Design 22 DOI: 10.1016/j.matdes.2021.109861 Diamond Proposal Number(s): [10597] Open Access Show Abstract ▼ Abstract: The effects of vacuum induction melting (VIM) vacuum (<1 Pa to 100Pa) on gas content, oxide inclusions and mechanical properties of Ni-based superalloy K4648 has been investigated by electron beam (EB) button experiment under high vacuum (10-3 Pa) and high resolution synchrotron X-ray powder diffraction (SXPD). The results indicated that VIM remelting vacuum drop has obvious effect on the existing form of trace oxygen. The total amount of oxygen did not increase significantly but a dramatic increase in the amount of oxide inclusions by 1-2 orders of magnitude was found. The inclusions are mainly oxides including Al2O3, Cr2O3, Ni(Al,Cr)2O4 and complex oxides or sulfides. Remelting under 100-110Pa has no significant effect on mechanical properties such as stress rupture life and tensile strength but decreased ductility obviously. In comparison to the normal vacuum counterpart, the tensile elongation and impact ductility of the alloy remelted under lower vacuum level decreased by 67% and 40%, respectively. This study reveals the relationship between the vacuum level and mechanical properties of superalloys and highlights the trace amount of oxide inclusions which should be considered as one of the key issues for the cleanliness of superalloys apart from the typical measurement of the gas content only.	Jun 2021
I12-JEEP: Joint Engineering, Environmental and Processing	The effects of internal stresses on the creep deformation investigated using in-situ synchrotron diffraction and crystal plasticity modelling Abdullah Al Mamun , Chris A. Simpson , Dylan Agius , Christina Reinhard , Christopher Truman , Mahmoud Mostafavi , David Knowles International Journal Of Solids And Structures DOI: 10.1016/j.ijsolstr.2021.111127 Diamond Proposal Number(s): [18836] Show Abstract ▼ Abstract: In this study we investigated the evolution of meso-scale internal stresses and those effects on local deformation behaviour during incremental plastic and creep deformation in type 316H stainless steel at 550°C, using in-situ X-ray synchrotron diffraction and crystal plasticity modelling. Owing to the fast data accusation rate of synchrotron diffraction technique, for the first time, the transient behaviour of different grain families was captured during initial fast stress relaxation period of the displacement-controlled creep dwells. Significantly it is found that the evolution of internal stresses during time independent plastic deformation is distinct from that during time dependent creep deformation. During plastic deformation, lattice strains in the {311} grain family exhibit linear behaviour whereas during creep deformation it exhibits non-linear behaviour, instead the {111} grain family exhibit linear behaviour. A novel unified constitutive law was devised within crystal plasticity framework based on the theoretical physics; the model successfully predicts the macroscopic deformation behaviour as well as the distinction between the evolution of meso-scale internal stresses during plastic and creep deformation, therefore, correctly accounting for the effect of internal stresses generated during plastic deformation on the subsequent creep deformation. The validated model has elucidated the grain-neighbouring effects on individual grain deformations.	Jun 2021
I15-Extreme Conditions	Solidification microstructure and residual stress correlations in direct energy deposited type 316L stainless steel Da Guo , Kun Yan , Mark D. Callaghan , Dominik Daisenberger , Mark Chatterton , Jiadong Chen , Andrew Wisbey , Wajira Mirihanage Materials & Design DOI: 10.1016/j.matdes.2021.109782 Diamond Proposal Number(s): [20605] Open Access Show Abstract ▼ Abstract: Localized fluctuation in residual stress distribution for direct energy deposited 316L stainless steel thin plate was revealed through high-energy synchrotron X-ray diffraction. The macroscopic residual stress levels are changed steadily across the article according to the characteristic cooling rates, as implied by the measured dendrite arm lengths. Localized fluctuations of residual stress in the length scale, between 500 to 600 µm, coincides well with the morphological variations of the solidification microstructure that formed during direct energy deposition. Computations indicate a greater propensity for related mesoscopic thermal gradient fluctuations along the solidification front of the moving melt pool. Novel perspectives on residual stress across multiple length-scales and its relevance to the formation of solidification microstructure in metal additive manufacturing is analysed by considering the experimental results.	May 2021

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