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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Extracting grain-orientation-dependent data from in situ time-of-flight neutron diffraction. I. Inverse pole figures

The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction to in situ monitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples include 316LN stainless steel in situ loaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling and in situ annealed up to 653 K.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

High-pressure cell for neutron diffraction with in situ pressure control at cryogenic temperatures

Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly neutron studies due to the volume of sample required. We present a novel, compact pressure cell with a large sample volume in which load is generated by a bellow. Using a supply of helium gas up to a pressure of 350 bar, a load of up to 78 kN is generated with leak-free operation. In addition, special fiber ports added to the cryogenic center stick allow for in situ pressure determination using the ruby pressure standard. Mechanical stability was assessed using finite element analysis and the dimensions of the cell have been optimized for use with standard cryogenic equipment. Load testing and on-line experiments using NaCl and BiNiO{sub 3} have been done at the WISH instrument of the ISIS pulsed neutron source to verify performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

In-situ observation of inhomogeneous degradation in large format Li-ion cells by neutron diffraction

This work presents a non-destructive in-situ method for probing degradation mechanisms in large format, operating, commercial lithium-ion batteries by neutron diffraction. A fresh battery (15 Ah capacity) was shown to have a uniform (homogeneous) local state of charge (SOC) at 4.0 V (9 Ah SOC) and 4.2 V (15 Ah SOC), with 1.33 C and 2.67 C charging rates, respectively. This battery was then aggressively cycled until it retained only a 9 Ah capacity, 60% of its original value. Inhomogeneous deterioration in the battery was observed: near the edges, both the graphite anode and the spinel-based cathode showed a significant loss of capacity, while near the central area, both electrodes functioned properly. An SOC mapping measurement of the degraded battery in the fully charged state (4.2 V) indicated that the loss of local capacity of the anode and cathode is coupled.

25 ENERGY STORAGE↗
DOE OSTI2013

Investigation of an unusual low-temperature phase transformation in RbBH{sub 4} by neutron diffraction

To investigate the previously reported low-temperature phase transition in rubidium borohydride (RbBH{sub 4}) near 48.5 K, we carried out neutron powder diffraction and vibrational spectroscopy measurements both above and below this temperature on an isotopically-enriched sample of Rb{sup 11}BD{sub 4}. Our diffraction data reflected an average cubic Fm3{sup ¯}m structure with BD{sub 4}{sup −} anion orientational disorder at all temperatures, with no hint of extra Bragg peaks due to long-range orientational order below the transition temperature as reported by others. These structural results and careful analysis of torsional vibrations in RbBD{sub 4} corroborate the results of prior neutron vibrational spectroscopy measurements suggesting that the low-temperature RbBH{sub 4} structure indeed possesses some orientational ordering of the BH{sub 4}{sup −} anions, but of a shorter-ranged nature insensitive to powder diffraction methods. - The neutron powder diffraction pattern of RbBD{sub 4} below the phase transition temperature (shown here in black) is indistinguishable from that collected above the phase transition temperature. The inset depicts the cubic structure that fits the data at both temperatures. - Highlights: • We investigated the nature of the RbBD{sub 4} phase transition using NVS and NPD. • A change in shape of the RbBD{sub 4} torsion mode was observed across the transition. • The RbBD{sub 4} diffraction pattern across this phase transition was unchanged. • The phase transition in RbBD{sub 4} appears to produce only short-range ordering of BD{sub 4}{sup −}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Chemical disorder determines the deviation of the Slater–Pauling rule for Fe 2 MnSi-based Heusler alloys: evidences from neutron diffraction and density functional theory

Fe 2 MnSi fails to follow the Slater–Pauling rule. This phenomenon is thought to originate from either: (i) an antiferromagnetic arrangement of Mn ions at low temperature and/or (ii) chemical disorder. An important insight on this issue could be achieved by considering Fe 2 MnSi 1-x Ga x compounds, thoroughly studied here by means of magnetization, neutron diffraction and density functional calculations (DFT). Our results indicate that chemical disorder (and not the antiferromagnetic arrangement) is responsible for the deviation of the Slater–Pauling rule on Fe 2 MnSi-based Heusler alloys. Furthermore, evidences suggest that Ga substitution into Si site favors the Fe/Mn disorder, further enhancing the observed deviation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Polymorphism in Photoluminescent KNdW2O8: Synthesis, Neutron Diffraction, and Raman Study

Polymorphs of KNdW2O8 ( -KNdW2O8 and -KNdW2O8) phosphors were synthesized by an efficient solution combustion technique for the first time. The crystal structure of the polymorphs analyzed from Rietveld refinement of neutron diffraction data confirms that -KNdW2O8 crystallizes in the tetragonal system (space group I4 ), and -KNdW2O8 crystallizes in the monoclinic system (space group C2/m). The local structure of both polymorphs was elucidated using combined neutron pair distribution function (PDF) and Raman scattering techniques. Photoluminescence measurements of the polymorphs showed broadened emission line width and increased intensity for -KNdW2O8 in the visible region compared to -KNdW2O8. This phenomenon is attributed to the increased distortion in the coordination environment of the luminescing Nd3+ ion. Combined PDF, Rietveld, and Raman measurements reveal distortions of the WO6 octahedra and NdO8 polyhedra in -KNdW2O8. This crystal structure photoluminescence study suggests that this class of tungstates can be exploited for visible light emitting devices by tuning the crystal symmetry.

Swain, Diptikanta↗
DOE OSTI2018

Time and frequency dependent mechanical properties of LaCoO 3 -based perovskites: Neutron diffraction and domain mobility

The study of domain wall movement and texture formation in ferroelastic LaCoO 3 perovskite under constant applied compressive stress has been performed using in situ neutron diffraction. Additionally, it was established that under constant applied compressive stress the domain walls show mobility that may lead both to the shrinkage (creep strain) and to the expansion (negative creep strain) of LaCoO 3 perovskite. The domain wall movement and texture formation can be explained by the availability, mobility, and interaction of twins, stacking faults, antiphase boundaries, dislocations, and point defects, such as oxygen vacancies and their complexes as well as impurity atoms. Lastly, the equation of motion was used to describe the possible mechanisms of domain wall movement under applied stress, and it was determined that the available solutions of this equation allow both for the shrinkage (creep strain) and for the expansion (negative creep strain) of LaCoO 3 perovskite to occur.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Crystallization of a fungal lytic polysaccharide monooxygenase expressed from glycoengineered Pichia pastoris for X-ray and neutron diffraction

Lytic polysaccharide monooxygenases (LPMOs) are carbohydrate-disrupting enzymes secreted by bacteria and fungi that break glycosidic bonds via an oxidative mechanism. Fungal LPMOs typically act on cellulose and can enhance the efficiency of cellulose-hydrolyzing enzymes that release soluble sugars for bioethanol production or other industrial uses. The enzyme PMO-2 from Neurospora crassa ( Nc PMO-2) was heterologously expressed in Pichia pastoris to facilitate crystallographic studies of the fungal LPMO mechanism. Diffraction resolution and crystal morphology were improved by expressing Nc PMO-2 from a glycoengineered strain of P. pastoris and by the use of crystal seeding methods, respectively. These improvements resulted in high-resolution (1.20 Å) X-ray diffraction data collection at 100 K and the production of a large Nc PMO-2 crystal suitable for room-temperature neutron diffraction data collection to 2.12 Å resolution.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments

We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm{sup 3}. Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Because the six-axis press has no guide blocks, there is sufficient space around the sample to use the aperture for diffraction and place an incident slit, radial collimators, and a neutron imaging camera close to the sample. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Magnetic phase diagram of the quantum spin chain compound SrCo 2 V 2 O 8 : a single-crystal neutron diffraction study

We explore magnetic order in the quantum spin chain compound SrCo 2 V 2 O 8 up to 14.9 T and down to 50 mK, using single-crystal neutron diffraction. Upon cooling in zero-field, commensurate antiferromagnetic (C-AFM) order with modulation vector ${{\boldsymbol{k}}}_{{\rm{C}}}$ = (0, 0, 1) develops below T N ≃ 5.0 K. Applying an external magnetic field (H∥c axis) destabilizes this C-AFM order, leading to an order-disorder transition between T N and ~1.5 K. Below 1.5 K, a commensurate to incommensurate (IC-AFM) transition occurs at 3.9 T, above which the magnetic reflections can be indexed by ${{\boldsymbol{k}}}_{{\rm{IC}}}$ = (0, 0, 1 ± δl). The incommensurability δl scales monotonically with H until the IC-AFM order disappears around 7.0 T. Magnetic reflections modulated by ${{\boldsymbol{k}}}_{{\rm{C}}}$ emerge again at higher fields. While the characters of the C-AFM, IC-AFM and the emergent AFM order in SrCo 2 V 2 O 8 appear to fit the descriptions of the Néel, longitudinal spin density wave and transverse AFM order observed in the related compound BaCo 2 V 2 O 8 , our results also reveal several unique signatures that are not present in the latter, highlighting the inadequacy of mean-field theory in addressing the complex magnetic order in systems of this class.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Correlating work hardening with co-activation of stacking fault strengthening and transformation in a high entropy alloy using in-situ neutron diffraction

Transformation induced plasticity (TRIP) leads to enhancements in ductility in low stacking fault energy (SFE) alloys, however to achieve an unconventional increase in strength simultaneously, there must be barriers to dislocation motion. While stacking faults (SFs) contribute to strengthening by impeding dislocation motion, the contribution of SF strengthening to work hardening during deformation is not well understood; as compared to dislocation slip, twinning induced plasticity (TWIP) and TRIP. Thus, we used in-situ neutron diffraction to correlate SF strengthening to work hardening behavior in a low SFE Fe 40 Mn 20 Cr 15 Co 20 Si 5 (at%) high entropy alloy, SFE ~ 6.31 mJ m –2 . Cooperative activation of multiple mechanisms was indicated by increases in SF strengthening and γ-f.c.c. → ε-h.c.p. transformation leading to a simultaneous increase in strength and ductility. The present study demonstrates the application of in-situ, neutron or X-ray, diffraction techniques to correlating SF strengthening to work hardening.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Chapter Twelve - Proton transfer and drug binding details revealed in neutron diffraction studies of wild-type and drug resistant HIV-1 protease

HIV-1 protease is an essential therapeutic target for the design and development of antiviral inhibitors to treat AIDS. We used room temperature neutron crystallography to accurately determine hydrogen atom positions in several protease complexes with clinical drugs, amprenavir and darunavir. Hydrogen bonding interactions were carefully mapped to provide an unprecedented picture of drug binding to the protease target. We demonstrate that hydrogen atom positions within the enzyme catalytic site can be altered by introducing drug resistant mutations and by protonating surface residues that trigger proton transfer reactions between the catalytic Asp residues and the hydroxyl group of darunavir. When protein perdeuteration is not feasible, we validate the use of initial H/D exchange with unfolded protein and partial deuteration in pure D2O with hydrogenous glycerol to maximize deuterium incorporation into the protein, with no detrimental effects on the growth of quality crystals suitable for neutron diffraction experiments.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Perdeuteration, crystallization, data collection and comparison of five neutron diffraction data sets of complexes of human galectin-3C

Galectin-3 is an important protein in molecular signalling events involving carbohydrate recognition, and an understanding of the hydrogen-bonding patterns in the carbohydrate-binding site of its C-terminal domain (galectin-3C) is important for the development of new potent inhibitors. The authors are studying these patterns using neutron crystallography. Here, the production of perdeuterated human galectin-3C and successive improvement in crystal size by the development of a crystal-growth protocol involving feeding of the crystallization drops are described. The larger crystals resulted in improved data quality and reduced data-collection times. Furthermore, protocols for complete removal of the lactose that is necessary for the production of large crystals of apo galectin-3C suitable for neutron diffraction are described. Five data sets have been collected at three different neutron sources from galectin-3C crystals of various volumes. It was possible to merge two of these to generate an almost complete neutron data set for the galectin-3C–lactose complex. As a result, these data sets provide insights into the crystal volumes and data-collection times necessary for the same system at sources with different technologies and data-collection strategies, and these insights are applicable to other systems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

A neutron diffraction study and mode analysis of compounds of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) and an investigation of their magnetic properties

We report here a detailed study of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x}, by neutron powder diffraction- and magnetic-measurements. All the compounds are robust antiferromagnetics with ordering temperatures well above room temperature. Magnetic moments are shown to align parallel to the c-axis. FC-ZFC measurements indicate a small canting of the magnetic moments, resulting in a ferromagnetic component with a maximum for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. We show that the system exhibits a composition-driven transition from a phase, for low fluorination levels (x≤0.5), with Pnma symmetry and the usual system of octahedral tiltings, to a phase with space group Imma for higher fluorine contents, where a correlated distortion of the oxygen octahedra plays a significant role. The consistency of the structural models, with respect to the expected continuity of the amplitudes of the different distortion modes and the invariance of their internal form, was monitored through the symmetry mode decomposition of the structures. - Graphical abstract: The crystal and magnetic structure of La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. Display Omitted - Highlights: • The compounds La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) were studied by neutron diffraction. • A mode analysis shows lower symmetry for Sr rich compounds than previously reported. • SrFeO{sub 2}F crystallizes in the orthorhombic space group Imma. • Magnetic moments resulting from canting depend on metric distortion. • The magnetic structure was determined for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Operando single crystal neutron diffraction reveals insight into the field response mechanisms in the hydrogen-bonded KH 2 PO 4 ferroelectric

The mechanism that facilitates polarization reorientation in KH 2 PO 4 (KDP) was investigated using operando single-crystal neutron diffraction. Diffraction data were measured from a KDP single crystal during the application of alternating electric fields and were then binned into 40 increments to enable field-dependent single-crystal structure refinements. The field-dependent structures are compared with an as-grown crystal to determine how the lattice and atomic sites evolve in response to the applied electric fields. These analyses provide evidence that the reorientation of the macroscopic polarization is facilitated through a cooperative change in hydrogen bonding, which results in the reversal of the spontaneous dipole. In addition, a decrease in secondary extinction near the coercive field indicates that the inversion of the macroscopic polarization is achieved through the nucleation and subsequent growth of new domains.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Neutron Diffraction Residual Stress Characterization of Large-Scale Components by WA-DED

Two large scale 316L stainless steel cylindrical shells were fabricated by wire arc directed energy deposition (WA DED). Residual stresses were measured by neutron diffraction, and the microstructure and mechanical properties of the printed material were characterized. Longitudinal and transverse residual stresses were compressive at the inner diameter, near neutral at mid wall, and tensile at the outer diameter; radial (through thickness) residual stresses were relatively low in magnitude, and peak tensile residual stresses occurred at the outer diameter surface along the longitudinal direction. The printed 316L SS exhibited a heterogeneous microstructure with finely dispersed δ ferrite, and demonstrated high yield and tensile strengths with large elongation and ductile fracture at ambient temperature and at 250 °C. These results indicate that the outer diameter surface and near surface regions—where tensile residual stress is highest—are the most vulnerable to residual stress–sensitive failure modes, such as stress corrosion cracking and fatigue.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Understanding the U 3 Si 2 crystal structure evolution as a function of temperature by neutron diffraction and simulation

U 3 Si 2 is actively researched as an accident tolerant fuel. Detailed knowledge of the crystal structure evolution, including knowledge of the anisotropic tetragonal lattice parameters, as a function of temperature and chemical composition is of paramount importance for predictions ranging from thermo-mechanical stresses to phase transformations to crystal lattice sites of fission products. Knowledge of the stability range of U 3 Si 2 is of great importance to understand whether changes of the stoichiometry, either from burn-up or due to synthesis variations, will lead to undesirable phase decomposition. To investigate these topics, stoichiometric U3Si2.00 and hyper-stoichiometric U 3 Si 2.01 were synthesized and characterized at ambient conditions and up to 1150°C using time-of-flight neutron diffraction on the HIPPO instrument at the Los Alamos Neutron Science Center (LANSCE) at LANL.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

A neutron diffraction study of structural distortion and magnetic ordering in the cation-ordered perovskites Ba{sub 2}Nd{sub 1−x}Y{sub x}MoO{sub 6}

The cation ordered perovskites Ba{sub 2}Nd{sub 1−x}Y{sub x}MoO{sub 6} (0.04≤x≤0.35) have been synthesised by solid-state techniques under reducing conditions at temperatures up to 1350 °C. Rietveld analyses of X-ray and neutron powder diffraction data show that these compounds adopt a tetragonally distorted perovskite structure. The tetragonal distortion is driven by the bonding requirements of the Ba{sup 2+} cation that occupies the central interstice of the perovskite; this cation would be underbonded if these compounds retained the cubic symmetry exhibited by the prototypical structure. The size and charge difference between the lanthanides and Mo{sup 5+} lead to complete ordering of the cations to give a rock-salt ordering of Nd{sup 3+}/Y{sup 3+}O{sub 6} and MoO{sub 6} octahedra. The I4/m space group symmetry is retained on cooling the x=0.1, 0.2 and 0.35 samples to low temperature ca. 2 K. Ba{sub 2}Nd{sub 0.90}Y{sub 0.10}MoO{sub 6} undergoes a gradual distortion of the MoO{sub 6} units on cooling from room temperature to give two long trans bonds (2.001(2) Å) along the z-direction and four shorter apical bonds (1.9563(13) Å) in the xy-plane. This distortion of the MoO{sub 6} units stabilises the 4d{sup 1} electron in the d{sub xz} and d{sub yz} orbitals whilst the d{sub xy} orbital is increased in energy due to the contraction of the Mo–O bonds in the xy-plane. This bond extension along z is propagated through the structure and gives a negative thermal expansion of −13×10{sup −6} K{sup −1} along c. The overall volumetric thermal expansion is positive due to conventional expansion along the other two crystallographic axes. With increasing Y{sup 3+} content this distortion is reduced in x=0.2 and eliminated in x=0.35 which contains largely regular MoO{sub 6} octahedra. The x=0.1 and x=0.2 show small peaks in the neutron diffraction profile due to long range antiferromagnetic order arising from ordered moments of ca. 2 μ{sub B}. - Graphical Abstract: The distortion in the molybdenum crystal field is continuously adjusted by chemical composition of the perovskite. Highlights: ► Introducing Y{sup 3+} into Ba{sub 2}NdMoO{sub 6} stabilises tetragonal symmetry to 2 K. ► A distortion of the ligand field around the Mo{sup 5+} 4d{sup 1} cation confers electronic stabilisation. ► The size of the distortion is progressively reduced with increasing Y{sup 3+} content. ► Distortion gives negative thermal expansion along z and antiferromagnetic order at T≤15 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗