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At least 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Probing the fatigue enhancement in a thermally aged cast duplex stainless steel by in situ neutron diffraction

After long-term thermal aging at 400 °C for 3000 h and 10,000 h, a cast duplex stainless steel exhibits promoted fatigue performance, including enhanced three-stage cyclic hardening and prolonged fatigue life. Utilizing in situ neutron diffraction, the phase-specific stresses are resolved, and their evolutions over entire fatigue cycling reveal the underlying mechanisms of the fatigue enhancement. It is found that the ferrite phase bears a much higher stress than the austenite matrix under both as-received and aged conditions. The enhanced cyclic hardening in Stage I is attributed to the strengthening of both phases due to thermal aging, while the enhancement in Stage III results from the martensitic transformation induced strengthening. The fatigue life is prolonged thanks to the cyclic hardening and the delay of martensitic transformation in the austenite phase after thermal aging.

Yu, Dunji↗
DOE OSTI2025

Processing-dependent chemical ordering in Cu 3 Au characterized via non-destructive Bragg coherent diffraction imaging

Of current importance for alloy design is controlling chemical ordering through processing routes to optimize an alloy's mechanical properties for a desired application. However, characterization of chemical ordering remains an ongoing challenge, particularly when nondestructive characterization is needed. Here, in this study, Bragg coherent diffraction imaging is used to reconstruct morphology and lattice displacement in model Cu 3 Au nanocrystals that have undergone different heat treatments to produce variation in chemical ordering. The magnitudes and distributions of the scattering amplitudes (proportional to electron density) and lattice strains within these crystals are then analyzed to correlate them to the expected amount of chemical ordering present. Nanocrystals with increased amounts of ordering are found to generally have less extreme strains present and reduced strain distribution widths. In addition, statistical correlations are found between the spatial arrangement of scattering amplitude and lattice strains.

Warren, Nathaniel [Pennsylvania State Univ., Unive↗
DOE OSTI2021

Pressurized in situ X-ray diffraction insights into super/subcritical carbonation reaction pathways of steelmaking slags and constituent silicate minerals

This study explores mineral carbonation of industrial stainless steelmaking slags and relevant synthetic constituent minerals via in situ pressurized X-ray diffraction, to clarify carbonation reaction pathways and efficiency for carbon storage and waste valorization. The primary mineral phases of Argon Oxygen Decarburization (AOD) and Continuous Casting (CC) slags, namely, åkermanite, bredigite, cuspidine, merwinite, and β- and γ-C 2 S, were reacted in a custom-built beryllium-capped XRD reactor filled with either water-saturated (wet) subcritical CO 2 (g), or wet supercritical CO 2(SC) , in a series of carbonation experiments. Formation of calcite and aragonite was observed for most Ca-bearing minerals, transient precipitation of metastable vaterite was observed, while carbonation of AOD and CC slags in CO 2(SC) resulted in hydrated crystalline calcium carbonates and indirect evidence of amorphous carbonate. Overall, results obtained suggest that low-pressure subcritical carbonation routes are attractive for standalone slag carbonation processes, while high-pressure supercritical carbonation routes are amiable to symbiotic integration with CO 2(SC) -generating green technologies.

42 ENGINEERING↗
DOE OSTI2017

Comparison of dislocation characterization by electron channeling contrast imaging and cross-correlation electron backscattered diffraction

In this paper, the relative capabilities and limitations of electron channeling contrast imaging (ECCI) and cross-correlation electron backscattered diffraction (CC-EBSD) have been assessed by studying the dislocation distributions resulting from nanoindentation in body centered cubic Ta. Qualitative comparison reveals very similar dislocation distributions between the CC-EBSD mapped GNDs and the ECC imaged dislocations. Approximate dislocation densities determined from ECC images compare well to those determined by CC-EBSD. Nevertheless, close examination reveals subtle differences in the details of the distributions mapped by these two approaches. Finally, the details of the dislocation Burgers vectors and line directions determined by ECCI have been compared to those determined using CC-EBSD and reveal good agreement.

36 MATERIALS SCIENCE↗
DOE OSTI2022

In-situ synchrotron X-ray diffraction investigation on deformation behavior of Nb/NiTi composite during pre-straining process

The mechanisms responsible for deformation behavior in Nb/NiTi composite during pre-straining were investigated systematically using in-situ synchrotron X-ray diffraction, transmission electron microscopy and tensile test. It is shown that upon loading, the composite experiences elastic elongation and slight plastic deformation of B19', B2 and β-Nb phases, together with the forward stress-induced martensitic (SIM) transformation from B2 to B19'. Upon unloading, the deformation mechanisms of the composite mainly involve elastic recovery of B19', B2 and β-Nb phases, compression deformation of β-Nb phase and incomplete B19'→B2 reverse SIM transformation. In the tensile loading-unloading procedure, besides the inherent elastic deformation and SIM transformation, the (001) compound twins in B19' martensite can also be conducive to the elastic deformation occurring in B19'-phase of the composite. Therefore, this composite can exhibit a large recoverable strain after unloading owing to the elastic deformation, and the partially reversible and consecutive SIM transformation together with the (001) compound twins.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structure elucidation of 3-[1-(6-methoxy-2-naphtyl)ethyl]-6-(2,4-dichlorophenyl)-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine, C 23 H 18 Cl 2 N 4 OS from synchrotron X-ray powder diffraction

The 3-[1-(6-methoxy-2-naphtyl)ethyl]-6-(2,4-dichlorophenyl)-7 H -1,2,4-triazolo[3,4- b ]-1,3,4-thiadiazine, C 23 H 18 Cl 2 N 4 OS compound was synthesized, as a member of the family of novel potential anticancer agents. The structure of the title compound was characterized by IR, 1 H-NMR, mass spectroscopy, and elemental analysis, previously. In this study, the crystal structure of this compound has been determined from synchrotron X-ray powder diffraction data. The crystal structure was solved by simulated annealing and the final structure was achieved by Rietveld refinement method using soft restrains on all interatomic bond lengths and angles. This compound crystallizes in space group P 21, Z = 2, with the unit-cell parameters a = 15.55645(11) Å, b = 8.61693(6) Å, c = 8.56702(6) Å, β = 104.3270(4)°, and V = 1112.68(1) Å 3 . In the crystal structure, strong C-H∙∙∙ π and weak intermolecular hydrogen-bonding interactions link the molecules into a three-dimensional network. The molecules are in a head-to-head arrangement in the unit cell.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Evolution in the structure of akaganeite and hematite during hydrothermal growth: an in situ synchrotron X-ray diffraction analysis

Synchrotron X-ray diffraction was used to monitor the hydrothermal precipitation of akaganeite ( β -FeOOH) and its transformation to hematite (Fe 2 O 3 ) in situ . Akaganeite was the first phase to form and hematite was the final phase in our experiments with temperatures between 150 and 200 °C. Akaganeite was the only phase that formed at 100 °C. Rietveld analyses revealed that the akaganeite unit-cell volume contracted until the onset of dissolution, and subsequently expanded. This reversal at the onset of dissolution was associated with a substantial and rapid increase in occupancy of the Cl site, perhaps by OH - or Fe 3+ . Rietveld analyses supported the incipient formation of an OH-rich, Fe-deficient hematite phase in experiments between 150 and 200 °C. The inferred H concentrations of the first crystals were consistent with “hydrohematite.” With continued crystal growth, the Fe occupancies increased. Contraction in both a- and c -axes signaled the loss of hydroxyl groups and formation of a nearly stoichiometric hematite.

Peterson, Kristina M.↗
DOE OSTI2024

ENERGY DISPERSIVE DIFFRACTION TOMOGRAPHY OF SHARK VERTEBRAL CENTRA

Shark vertebrae and their centra (vertebral bodies) are high-performance structures able to survive millions of cycles of high amplitude strain despite lacking a repair mechanism for accumulating damage. Shark centra consist of mineralized cartilage, a biocomposite of bioapatite (bAp), and collagen, and the nanocrystalline bAp's contribution to functionality remains largely uninvestigated. Using the multiple detector energy-dispersive diffraction (EDD) system at 6-BM-B, the Advanced Photon Source, and 3D tomographic sampling, the 3D functionality of entire centra were probed. Immersion in ethanol vs phosphate-buffered saline produces only small changes in bAp d-spacing within a great hammerhead centrum. EDD mapping under in situ loading was performed an entire blue shark centrum, and 3D maps of bAp strain showed the two structural zones of the centrum, the corpus calcareum and intermedialia, contained opposite-signed strains approaching 0.5%, and application of similar to 8% nominal strain did not alter these strain magnitudes and their spatial distribution.

Park, Jun-Sang↗
DOE OSTI2021

Modulating Electron Beam–Sample Interactions in Imaging and Diffraction Modes by Dose Fractionation with Low Dose Rates

Abstract Technological opportunities are explored to enhance detection schemes in transmission electron microscopy (TEM) that build on the detection of single-electron scattering events across the typical spectrum of interdisciplinary applications. They range from imaging with high spatiotemporal resolution to diffraction experiments at the window to quantum mechanics, where the wave-particle dualism of single electrons is evident. At the ultimate detection limit, where isolated electrons are delivered to interact with solids, we find that the beam current dominates damage processes instead of the deposited electron charge, which can be exploited to modify electron beam-induced sample alterations. The results are explained by assuming that all electron scattering are inelastic and include phonon excitation that can hardly be distinguished from elastic electron scattering. Consequently, a coherence length and a related coherence time exist that reflect the interaction of the electron with the sample and change linearly with energy loss. Phonon excitations are of small energy (<100 meV), but they occur frequently and scale with beam current in the irradiated area, which is why we can detect their contribution to beam-induced sample alterations and damage.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Far-Field High-Energy Diffraction Microscopy: A Non-Destructive Tool for Characterizing the Microstructure and Micromechanical State of Polycrystalline Materials

A suite of non-destructive, three-dimensional X-ray microscopy techniques have recently been developed and used to characterize the microstructures of polycrystalline materials. These techniques utilize high-energy synchrotron radiation and include near-field and far-field diffraction microscopy (NF- and FF-HEDM, respectively) and absorption tomography. Several compatible sample environments have also been developed, enabling a wide range of 3D studies of material evolution. In this article, the FF-HEDM technique is described in detail, including its implementation at the 1-ID beamline of the Advanced Photon Source. Examples of how the information obtained from FF-HEDM can be used to deepen our understanding of structure-property-processing relationships in selected materials are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Modified Oxygen Defect Chemistry at Transition Metal Oxide Heterostructures Probed by Hard X-ray Photoelectron Spectroscopy and X-ray Diffraction

Transition metal oxide hetero-structures are interesting due to the distinctly different properties that can arise from their interfaces, such as superconductivity, high catalytic activity and magnetism. Oxygen point defects can play an important role at these interfaces in inducing potentially novel properties. The design of oxide hetero-structures in which the oxygen defects are manipulated to attain specific functionalities requires the ability to resolve the state and concentration of local oxygen defects across buried interfaces. In this work, we utilized a novel combination of hard x-ray photoelectron spectroscopy (HAXPES) and high resolution xray diffraction (HRXRD) to probe the local oxygen defect distribution across the buried interfaces of oxide heterolayers. This approach provides a non-destructive way to qualitatively probe locally the oxygen defects in transition metal oxide hetero-structures. We studied two trilayer structures as model systems - the La 0.8 Sr 0.2 CoO 3-δ /(La 0.5 Sr 0.5 ) 2 CoO 4 /La 0.8 Sr 0.2 CoO 3-δ (LSC 113 /LSC 214 ) and the La 0.8 Sr 0.2 CoO 3-δ /La 2 NiO 4+δ /La 0.8 Sr 0.2 CoO 3-δ (LSC 113 /LNO 214 ) on SrTiO 3 (001) single crystal substrates. We found that the oxygen defect chemistry of these transition metal oxides was strongly impacted by the presence of interfaces and the properties of the adjacent phases. Under reducing conditions, the LSC 113 in the LSC 113 /LNO 214 tri-layer had less oxygen vacancies than the LSC 113 in the LSC 113 /LSC 214 tri-layer and the LSC 113 single phase film. On the other hand, LSC 214 and LNO 214 were more reduced in the two tri-layer structures when in contact with the LSC 113 layer compared to their single phase counterparts. Furthermore, the results point out a potential way to modify the local oxygen defect states at oxide hetero-interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Metastable Li 1+δ Mn 2 O 4 (0 ≤ δ ≤ 1) Spinel Phases Revealed by in Operando Neutron Diffraction and First-Principles Calculations

Here, we examine the reaction mechanisms driven by the lithiation of Li 1+δ Mn 2 O 4 (0 ≤ δ ≤ 1) spinels via in operando neutron powder diffraction (NPD). New reaction mechanisms are proposed involving solid-solution regions within both cubic and tetragonal spinel phases in addition to a continuous phase transition between them. In operando NPD is an ideal tool to follow the light elements such as lithium and oxygen in cathode materials which are often the key to fully understand their structural evolutions. Here, we report a novel methodology to prepare an extremely thick electrode with ~378 mg·cm –2 loading density suitable for the in operando NPD studies. Enabled by such thick electrode, we find that the metal oxygen M–O (M = Li and Mn) bond lengths in both end members LiMn 2 O 4 and Li 2 Mn 2 O 4 experience pronounced changes larger than dictated by the change in lattice parameters because of the locally formed Jahn–Teller distorted Mn 3+ . First-principles density functional theory calculations confirm these metastable intermediates and further propose atomistic reaction pathways for the phase transition by coupling a global structure search algorithm. In conclusion, these findings redefine the conventional understandings on two-phase reactions of this spinel material.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structure and Thermal Stability of (H 2 O) 4 Tetrahedron and (H 2 O) 6 Hexagon Adsorbed on NaY Zeolite Studied by Synchrotron-Based Time-Resolved X-ray Diffraction

Water adsorption and desorption features play an important role in determining the adsorptive and catalytic properties of zeolites. In this study, the extraframework structure (water and cations) in NaY faujasite zeolite was studied by synchrotron-based in situ time-resolved X-ray diffraction (TR-XRD) in combination with the Rietveld refinement method. It was observed that Na cations locating at different sites migrated between each other during the dehydration process. Water molecules at three separate sites showed interesting geometries: (H 2 O) 4 tetrahedron W1, (H 2 O) 6 ice-like hexagonal W2, and disordered triangle W3. Interactions between each form of water and Na cations were deeply investigated. Here, the stability of the waters followed the sequence of W1 > W3 > W2. This work provides insights into both framework structure and cation positions of model zeolite under actual working conditions, which helps fully understand the properties of zeolites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Hydrogen Purification in Palladium-Based Membranes: An Operando X-ray Diffraction Study

Palladium (Pd)-based membranes are highly selective to H 2 , compact, and operationally flexible, and they could facilitate efficient and on-demand production of H 2 as a clean energy carrier. For the first time, we designed an operando X-ray diffraction (XRD) experiment to study a dense Pd membrane during H 2 permeation at typical operating conditions (e.g., 280–440 °C and 1–3 bar pressure difference). By correlating the lattice structure of a metallic membrane with its gas-separation performance in real time, the operando XRD experiment could serve as a diagnostic tool for research on high-temperature gas-separation membranes. As a proof-of-concept study, we simultaneously collected H 2 -flux and transmission-XRD measurements, from which we calculated key hydrogen-transport properties, including permeability, solubility, and diffusivity. We also showed that the Pd lattice remained in the α phase throughout the operating conditions investigated. Furthermore these results are in reasonable agreement with the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structural Correlation to Piezoelectric and Ferroelectric Mechanisms in Rhombohedral Pb(Zr,Ti)O 3 Ceramics by in-Situ Synchrotron Diffraction

Here, the evidence of fundamental lattice strain and domain switching contribution to the piezoelectric and ferroelectric responses of ceramics has been well studied, while the contribution from crystal structure variation has been rarely reported in terms of the existence of intergranular stress/strain and crystallographic texture. In the present study, the detailed electric field induced structure evolution in rhombohedral PbZr 0.55 Ti 0.45 O 3 (PZT55) has been investigated by in-situ high-energy synchrotron diffraction. The phase of PZT55 is stable in the rhombohedral one against bipolar electrical loading. It is interesting to find that both spontaneous polarization and unit cell volume exhibit a butterfly shape in response to electric field. Direct evidence has revealed that the lattice strain and volume expansion show similar variation tendency to the piezoelectric response in the rhombohedral PZT55. The macro-polarization of PZT55 derives from the combination of domain switching and spontaneous polarization change.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dehydration of UO 2 Cl 2 ·3H 2 O and Nd(NO 3 ) 3 ·6H 2 O with a Soft Donor Ligand and Comparison of Their Interactions through X-ray Diffraction and Theoretical Investigation [plus Supplemental Information]

Herein we investigated whether the relatively Lewis basic imidazole-2-thiones could be used to substitute water ligands bound to f-element cations and generate f-element soft donor complexes. Reactions of 1,3-diethylimidazole-2-thione (C 2 C 2 ImT) with Nd(NO 3 ) 3 ·6H 2 O and UO 2 Cl 2 ·3H 2 O led to the isolation of the anhydrous thione complexes Nd(NO 3 ) 3 (C 2 C 2 ImT) 3 and UO 2 Cl 2 (C 2 C 2 ImT) 2 , characterized by single crystal X-ray diffraction. Differences in the strength of metal–thione interactions have been examined by means of the crystal structure analysis and density functional theory (DFT) calculations. The C 2 C 2 ImT ligands were found to be affected by both coordination and noncovalent interactions, making it impossible to deconvolute the effects of one from the other. Calculated partial atomic charges indicated greater ligand-to-metal charge transfer in the [UO 2 ] 2+ complex, indicative of a stronger interaction. The reactivity of C 2 C 2 ImT demonstrates its usefulness in the preparation of f-element soft donor complexes from readily available hydrates that could be useful intermediates for promoting the coordination and studying the effects of soft donor anions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

In Situ High-Temperature Synchrotron Diffraction Studies of (Fe,Cr,Al) 3 O 4 Spinels

The modeling of a loss-of-coolant-accident scenario involving nuclear fuels with FeCrAl cladding materials in consideration to replace a Zircaloy requires knowledge of the thermodynamics of oxidized structures. At temperatures higher than 1500 degrees C, oxidation of FeCrAl alloys forms (Fe,Cr,Al) 3 O 4 spinels. In situ high-energy X-ray diffraction in a conical nozzle levitator installed at beamline 6-ID-D of the APS was used to study the structural evolution of the oxides as a function of the temperature. Single-phase (spinel) and multiphase (spinel-corundum-FeAlO 3 ) regions are mapped as a function of the temperature for three different compositions of FeCrAl oxidation products. The thermal expansion coefficients and cation distribution in the spinel structure have been refined. The temperature at which complete melting of the fuel cladding is expected has been determined by the liquidus temperatures of the oxidized products to be between 1657 and 1834 degrees C in a 20% O 2 /Ar atmosphere using the cooling trace method. The liquidus temperature increases with increasing Al and Cr content in the spinel phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗