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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Unraveling structural evolution of LiNi 0.5 Mn 1.5 O 4 by in situ neutron diffraction

Here, we report that the electrochemical properties of the spinel LiNi 0.5 Mn 1.5 O 4 cathode material are influenced by the synthesis processes, which determines the impurity phase and the distribution of Ni and Mn in the spinel structure. Taking advantage of neutron's high sensitivity to Ni and Mn, in situ neutron diffraction has been employed to quantify the phase formation/structural evolution process under continuous heating/cooling and isothermal annealing conditions. The results show that the subtle Ni and Mn ordering process occurs slowly at 700 °C and the degree of ordering can be controlled by the annealing time. At temperatures above 750 °C, the LiNi 0.5 Mn 1.5 O 4 spinel phase starts to decompose into the rock-salt impurity phase accompanied by the release of O 2 . The rock-salt phase reverts back to the spinel phase upon cooling along with the oxygen uptake. In conclusion, the dynamic process of structural evolution of LiNi 0.5 Mn 1.5 O 4 that was unraveled by in situ neutron diffraction is valuable for guiding the synthesis of cathode materials with desirable properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Flux Growth of Cerium Nickel Gallides Studied by In Situ Neutron Diffraction

In this work, reactions of cerium and nickel in excess molten gallium were monitored by neutron diffraction during heating and cooling. The formation of binary intermediates CeGa 2 and Ni 2 Ga 3 was observed during heating. During cooling of the molten mixture from 900 °C, precipitation of BaAl 4 -type CeNi 0.74 Ga 3.26 occurred at 850 °C. Upon cooling to 650 °C, this compound reacted in the flux to form Ce 2 NiGa 10 and then Ce 2 NiGa 12 , the latter of which persisted to room temperature. Making use of this information, subsequent reactions were quenched at 750 °C to isolate crystals of CeNi 0.74 Ga 3.26 for further study. Similar reactions replacing Ce with La and quenching above 750 °C yielded LaNi 0.35 Ga 3.65 crystals. Magnetic susceptibility studies on CeNi 0.74 Ga 3.26 indicate that the cerium is trivalent; the Ce 3+ moments undergo a strongly anisotropic ferromagnetic ordering with moment perpendicular to the c axis below 7 K. Heat capacity data show little evidence of heavy fermion behavior. Resistivity measurements show that both LaNi0.35Ga3.65 and CeNi 0.74 Ga 3.26 exhibit metallic behavior. Density of states calculations support this and indicate that Ni/Ga mixing in the compound stabilizes the structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

A furnace with rotating load frame for in situ high temperature deformation and creep experiments in a neutron diffraction beam line

A resistive furnace combined with a load frame was built that allows for in situ neutron diffraction studies of high temperature deformation, in particular, creep. A maximum force of 2700 N can be applied at temperatures up to 1000 deg. C. A load control mode permits studies of, e.g., creep or phase transformations under applied uni-axial stress. In position control, a range of high temperature deformation experiments can be achieved. The examined specimen can be rotated up to 80 deg. around the vertical compression axis allowing texture measurements in the neutron time-of-flight diffractometer HIPPO (High Pressure - Preferred Orientation). We present results from the successful commissioning, deforming a Zr-2.5 wt.% Nb cylinder at 975 deg. C. The device is now available for the user program of the HIPPO diffractometer at the LANSCE (Los Alamos Neutron Science Center) user facility.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Solving the P–O/P–OH riddle: direct synthesis and neutron diffraction characterization of dianionic dithiophosphonates

Here, we report the first definitive neutron diffraction study aimed at resolving the P–OH/P$=$O structural ambiguity in metal dithiophosphonates. The small NH 4 counterion forces a rare syn-configuration via an extended hydrogen-bonding network. Neutron analysis definitively confirmed the fully deprotonated P$=$O moiety, thus confirming the formation of a dianionic dithiophosphonate, a versatile synthon in homoleptic and heteroleptic coordination environments.

Pillay, Michael N. [National Dong Hwa Univ. (Taiwa↗
DOE OSTI2018

Synchrotron X-Ray and Neutron Diffraction, Total Scattering, and Small-Angle Scattering Techniques for Rechargeable Battery Research

Synchrotron X-ray and neutron scientific facilities are the most advanced resources with a large variety of state of the art instrumentations and powerful tools for materials research. X-rays and neutrons interact with matter in different ways and offer complementary views of materials at various levels. In this article, we will focus on the techniques and applications of synchrotron X-ray and neutron diffraction, total scattering and small-angle scattering for rechargeable battery research. They all belong to the elastic scattering category and provide structure information at different length scales. Here, the diffraction method is generally used to determine the phase and precise atomistic information of crystalline materials, while the total scattering coupled with pair-distribution function analysis can probe local atomic structure of materials no matter they are well crystallized or in amorphous/liquid phases. The small-angle scattering techniques provide us with material size and shape information at nanometer scales. Advantages of synchrotron high-energy X-rays will also be presented, which is particularly suited for the pair-distribution-function studies. We will pay much attention to the technical perspectives and some experimental specifications for the best uses of these methods for battery materials research.

25 ENERGY STORAGE↗
DOE OSTI2011

Magnetic structure of CuCrO2: a single crystal neutron diffraction study

This paper presents results of a recent study of multiferroic \CCO\ by means of single crystal neutron diffraction. This system has two close magnetic phase transitions at $T\nsub{N1}=24.2$~K and $T\nsub{N2}=23.6$~K. The low temperature magnetic structure below $T\nsub{N2}$ is unambiguously determined to be a fully 3-dimensional proper screw. Between $T\nsub{N1}$ and $T\nsub{N2}$ antiferromagnetic order is found that is essentially 2-dimensional. In this narrow temperature range, magnetic near neighbor correlations are still long range in the ($H,K$) plane, whereas nearest neighbors along the $L$-direction are uncorrelated. Thus, the multiferroic state is realized only in the low-temperature 3-dimensional state and not in the 2-dimensional state.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Crystal structure of α- and β-Na{sub 2}U{sub 2}O{sub 7}: From Rietveld refinement using powder neutron diffraction data

The crystal structures of α- and β-Na{sub 2}U{sub 2}O{sub 7} have been determined from neutron powder diffraction. At 293 K, the compound α-Na{sub 2}U{sub 2}O{sub 7} has a monoclinic unit cell, space group P2{sub 1}/a, with a=12.7617(14) Å, b=7.8384(10) Å, c=6.8962(9) Å, β=111.285(9)°, and Z=4. At 773 K, β-Na{sub 2}U{sub 2}O{sub 7} is also monoclinic, space group C2/m, with a=12.933(1) Å, b=7.887(1) Å, c=6.9086(8) Å, β=110.816(10)°, and Z=4. The structures can be described by layers U{sub 2}O{sub 7}{sup 2−} built from corner linked deformed UO{sub 6} octahedra with pentagonal UO{sub 7} bipyramids in between linked with common edges to each other and to the octahedra. The Na atoms occupy the interlayer space. The Na{sub 2}U{sub 2}O{sub 7} layers are similar as in K{sub 2}U{sub 2}O{sub 7}, but with a different stacking sequence of the layers. The layers in β-Na{sub 2}U{sub 2}O{sub 7} are more symmetric. The relationship with the compounds A{sub 2}U{sub 2}O{sub 7} (A=K, Rb, and Cs) is discussed. - Graphical abstract: The U{sub 2}O{sub 7} layer of α-Na{sub 2}U{sub 2}O{sub 7} (left) at 293 K and of β-Na{sub 2}U{sub 2}O{sub 7} (right) at 773 K determined by neutron diffraction. Some Na atoms between the layers are visible. - Highlights: • Na{sub 2}U{sub 2}O{sub 7} has been prepared by means of a solid state reaction. • The structure has been determined using neutron diffraction. • At 293 K, the compound adopts a monoclinic structure with space group P2{sub 1}/a. • The structure at 773 K is closely related, and is described in the space group C2/m.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Preparation and neutron diffraction study of Dion-Jacobson type oxynitrides LiLaTa{sub 2}O{sub 7−3x}N{sub 2x} (x = 0.09, 0.29)

Highlights: ► Dion-Jacobson oxynitrides LiLaTa{sub 2}O{sub 7−3x}N{sub 2x}□{sub x} (x < 0.3) by ammonolysis of LiLaTa{sub 2}O{sub 7}. ► Enhanced thermal stability and band gap narrowing by the oxynitride modification. ► Locations of N and □ within LiLaTa{sub 2}O{sub 7−3x}N{sub 2x} by neutron diffraction and {sup 7}Li MAS NMR. -- Abstract: Ammonolytic heating of Dion-Jacobson type layered perovskite LiLaTa{sub 2}O{sub 7} produced oxynitride derivatives LiLaTa{sub 2}O{sub 7−3x}N{sub 2x}□{sub x}via the substitution, 3O{sup 2−} → 2N{sup 3−} + □. The nitridation level increased with raising the temperature and/or increasing the time of reaction, reaching the limit at x ≈ 0.3 by the ammonolysis at 650 °C for 48 h. Upon the nitridation, tetragonal pristine lattice underwent a axis expansion together with c axis contraction. Neutron Rietveld refinement of LiLaTa{sub 2}O{sub 7} and LiLaTa{sub 2}O{sub 7−3x}N{sub 2x} (x = 0.09, 0.29) revealed that the Li-centered tetrahedra are gradually compressed along the 2-fold rotation axis, with the increase of x. Solid state {sup 7}Li nuclear magnetic resonance spectroscopy suggested that the anion vacancy resides mostly on the interlayer surface of perovskite block. As measured from the diffuse-reflectance spectroscopy, the nitridation induced marked reduction in the band gap magnitude, from 4.11 eV (x = 0) to 3.35 eV (x = 0.09) to 2.76 eV (x = 0.29).

36 MATERIALS SCIENCE↗
DOE OSTI2018

Next-generation diamond cell and applications to single-crystal neutron diffraction

In this paper, a diamond cell optimized for single-crystal neutron diffraction is described. It is adapted for work at several of the single-crystal diffractometers of the Spallation Neutron Source and the High Flux Isotope Reactor at the Oak Ridge National Laboratory (ORNL). A simple spring design improves portability across the facilities and affords load maintenance from offline pressurization and during temperature cycling. Compared to earlier prototypes, pressure stability of polycrystalline diamond (Versimax®) has been increased through double-conical designs and ease of use has been improved through changes to seat and piston setups. These anvils allow ~30%-40% taller samples than possible with comparable single-crystal anvils. Hydrostaticity and the important absence of shear pressure gradients have been established with the use of glycerin as a pressure medium. Large single-crystal synthetic diamonds have also been used for the first time with such a clamp-diamond anvil cell for pressures close to 20 GPa. The cell is made from a copper beryllium alloy and sized to fit into ORNL’s magnets for future ultra-low temperature and high-field studies. Finally, we show examples from the Spallation Neutron Source’s SNAP and CORELLI beamlines and the High Flux Isotope Reactor’s HB-3A and IMAGINE beamlines.

36 MATERIALS SCIENCE↗
DOE OSTI2017

In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

In situ neutron diffraction measurements were completed for this study during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material’s initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed the Taylor equation, indicating that the AM material’s increased yield strength was primarily due to greater dislocation density. Finally, a ~50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.

36 MATERIALS SCIENCE↗
DOE OSTI2016

In-situ TOF neutron diffraction studies of cyclic softening in superelasticity of a NiFeGaCo shape memory alloy

Real-time in-situ neutron diffraction was conducted during uniaxial cycling compression of a Ni 49.3 Fe 18 Ga 27 Co 5.7 shape memory alloy to explore the mechanism on its superelasticity at room temperature, which was manifested by the almost recoverable large strains and the apparent cyclic softening. Based on the Rietveld refinements, the real-time evolution of volume fraction of martensite was in-situ monitored, indicating the incremental amount of residual martensite with increasing load cycles. Real-time changes in intensities and lattice strains of { hkl } reflections for individual phase were obtained through fitting individual peaks, which reveal the quantitative information on phase transformation kinetics as a function of grain orientation and stress/strain partitioning. Moreover, a large compressive residual stress was evidenced in the parent phase, which should be balanced by the residual martensite after the second unloading cycle. As a result, the large compressive residual stress found in the parent austenite phase may account for the cyclic effect on critical stress required for triggering the martensitic transformation in the subsequent loading.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Crystal structure of Bi{sub 1-x}Tb{sub x}FeO{sub 3} from high-resolution neutron diffraction

Samples of Bi{sub 1-x}Tb{sub x}FeO{sub 3}, with x=0.05, 0.10, 0.15, 0.20 and 0.25, have been synthesised by solid state reaction. The crystal structures of the perovskite phases, characterised via Rietveld analysis of high resolution powder neutron diffraction data, reveal a structural transition from the R3c symmetry of the parent phase BiFeO{sub 3} to orthorhombic Pnma symmetry, which is complete for x=0.20. The x=0.10 and 0.15 samples are bi-phasic. The transition from a rhombohedral to orthorhombic unit cell is suggested to be driven by the dilution of the stereochemistry of the Bi{sup 3+} lone pair at the A-site. The G-type antiferromagnetic spin structure, the size of the ordered magnetic moment ({approx}3.8 {mu}{sub B}) and the T{sub N} ({approx}375 deg. C) are relatively insensitive to increasing Tb concentrations at the A-site. - Graphical abstract: High resolution neutron powder diffraction has been used to study the evolution of the RT crystal structure of Bi{sub 1-x}Tb{sub x}FeO{sub 3} (0.05{<=}x{<=}0.25) with terbium content. A transition from polar R3c to centrosymmetric Pnma symmetry is observed. The antiferromagnetic ordering temperature and size of the ordered magnetic moment are relatively insensitive to the change of crystal structure. Highlights: > Structural transition from polar R3c symmetry to non-polar Pnma symmetry occurs. > Behaviour is rationalised via dilution of the stereochemical nature of the Bi lone pair. > Magnetic properties are largely unaffected.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Neutron Diffraction Residual Strain Tensor Measurements Within The Phase IA Weld Mock-up Plate P-5

Oak Ridge National Laboratory (ORNL) has worked with NRC and EPRI to apply neutron and X-ray diffraction methods to characterize the residual stresses in a number of dissimilar metal weld mockups and samples. The design of the Phase IA specimens aimed to enable stress measurements by several methods and computational modeling of the weld residual stresses. The partial groove in the 304L stainless steel plate was filled with weld beads of Alloy 82. A summary of the weld conditions for each plate is provided in Table 1. The plates were constrained along the long edges during and after welding by bolts with spring-loaded washers attached to the 1-inch thick Al backing plate. The purpose was to avoid stress relief due to bending of the welded stainless steel plate. The neutron diffraction method was one of the methods selected by EPRI for non-destructive through thickness strain and stress measurement. Four different plates (P-3 to P-6) were studied by neutron diffraction strain mapping, representing four different welding conditions. Through thickness neutron diffraction strain mappings at NRSF2 for the four plates and associated strain-free d-zero specimens involved measurement along seven lines across the weld and at six to seven depths. The mountings of each plate for neutron diffraction measurements were such that the diffraction vector was parallel to each of the three primary orthogonal directions of the plate: two in-plane directions, longitudinal and transverse, and the direction normal to the plate (shown in left figure within Table 1). From the three orthogonal strains for each location, the residual stresses along the three plate directions were calculated. The principal axes of the strain and stress tensors, however, need not necessarily align with the plate coordinate system. To explore this, plate P-5 was selected for examination of the possibility that the principal axes of strain are not along the sample coordinate system axes. If adequate data could be collected the goal would be to determine the strain tensor's orientation and magnitude of strain along each principle axis direction.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Neutron diffraction study of La[subscript 4]LiAuO[subscript 8]: Understanding Au[superscript 3+] in an oxide environment

Owing to gold's oxophobicity, its oxide chemistry is rather limited, and elevated oxygen pressures are usually required to prepare ternary and quaternary oxide compounds with gold ions. The Au{sup 3+} oxide, La{sub 4}LiAuO{sub 8}, is remarkable both because it can be prepared at ambient pressure in air, and because of its unusual stability toward thermal decomposition and reduction. The structure of La{sub 4}LiAuO{sub 8} was established by Pietzuch et al. using single crystal X-ray diffraction [1]. The compound adopts an ordered modification of the Nd{sub 2}CuO{sub 4} structure, containing two-dimensional sheets in which AuO{sub 4} square planes are separated from one another by LiO{sub 4} square planes. In light of the meager X-ray scattering factors of Li and O, relative to La and Au, we report here a neutron powder diffraction study of La{sub 4}LiAuO{sub 8}, definitively confirming the structure. To our knowledge, this is the first reported neutron diffraction study of any stoichiometric oxide compound of gold. X-N maps, which make use of nuclear positions obtained from Rietveld refinement of time-of-flight neutron diffraction data and electron densities obtained from synchrotron X-ray powder diffraction data, point to the highly covalent nature of the Au-O bonding in La{sub 4}LiAuO{sub 8}. This is in good agreement with charge densities and Bader charges obtained from full density functional relaxation of the structure.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Multidimensional Rietveld refinement of high-pressure neutron diffraction data of PbNCN

High-pressure neutron powder diffraction data from PbNCN were collected on the high-pressure diffraction beamline SNAP located at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory (Tennessee, USA). The diffraction data were analyzed using the novel method of multidimensional (two dimensions for now, potentially more in the future) Rietveld refinement and, for comparison, employing the conventional Rietveld method. To achieve two-dimensional analysis, a detailed description of the SNAP instrument characteristics was created, serving as an instrument parameter file, and then yielding both cell and spatial parameters as refined under pressure for the first time for solid-state cyanamides/carbodiimides. The bulk modulus B 0 = 25.1 (15) GPa and its derivative B ′ 0 = 11.1 (8) were extracted for PbNCN following the Vinet equation of state. Surprisingly, an internal transition was observed beyond 2.0 (2) GPa, resulting from switching the bond multiplicities (and bending direction) of the NCN 2− complex anion. The results were corroborated using electronic structure calculation from first principles, highlighting both local structural and chemical bonding details.

Meinerzhagen, Yannick↗