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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Complexation of Pluronic L62 (EO 6 )–(PO 34 )–(EO 6 )/aerosol-OT (sodium bis(2-ethylhexyl)sulfosuccinate) in aqueous solutions investigated by small angle neutron scattering

Herein, we investigate the phase behaviours of Pluronic L62 in aqueous solution in the presence of aerosol-OT (AOT) molecules by small angle neutron scattering (SANS). The presence of AOT significantly changes the micellization phenomenon of L62 micelles in aqueous solution, including their critical micelle temperature (CMT), global size, and asphericity. The origin of these observations is attributed to the complexation between the neutral L62 surfactants and the ionic AOT molecules, which additionally provides charge to the mixed micelles: we analyse the data and extract meaningful information using the Ornstein–Zernike integral formalism. As a result, we observe that the co-micellization of L62 and AOT is very stable across a wide temperature range.

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

Coexistence of Soft Modes and Dynamic Ti Disorder in Cubic BaTiO 3 Studied by Inelastic Neutron Scattering

The phonon dispersion relations in cubic BaTiO 3 have been measured along the [100], [110], and [111] directions at T = 453 K using inelastic neutron scattering. The isotropic transverse acoustic (TA) branches indicate that the interatomic force constant between Ba and O atoms in BaTiO 3 is large compared with that between Pb and O atoms in PbTiO 3 . The transverse optical (TO) branches along the [100] and [111] directions soften toward the Brillouin zone center. The TO branch along the [110] direction with [001] polarization is relatively low and flat, indicating the weak interatomic force constant between Ti and O atoms along the Ti–O chain. The intensity of inelastic diffuse scattering along the [100] and [110] directions increases with decreasing temperature down to 453 K. In conclusion, the present results suggest that the soft modes coexist with the dynamic Ti disorder in the Ti–O chain near the phase transition in the cubic phase.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Characterization of Porosity and Pore Accessibility of Vitrinite-Rich Bituminous and Subbituminous Coals by Small-Angle Neutron Scattering, Mercury Intrusion Porosimetry, and Low-Pressure N 2 Adsorption

Three bituminous and one subbituminous vitrinite-rich coals were characterized using small-angle neutron scattering with contrast matching, mercury intrusion porosimetry, and low-pressure N 2 adsorption techniques to quantify their porosity and pore accessibility in an effort to assess their solvent extractabilities, as a first approximation, for manufacturing useful end-products. The techniques revealed consistent results while complimenting one another. The total porosity was found to follow the coal rank with the lowest rank having the highest porosity within the studied coals. The amount of inaccessible pores was found to increase with rank for the bituminous coals studied here. Finally, the increase in the ease of accessibility and total porosity with decreasing rank suggested easier penetration of chemical reagents for solvent extraction, for example.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Self-Diffusivity Measurement of Eutectic F 7 LiNaK with and without Additives Using Quasi-Elastic Neutron Scattering

The atomic scale relaxation dynamics of eutectic F 7 LiNaK (46.5 LiF–11.5 NaF–42 KF mol %, Li-7 enriched) were measured using quasi-elastic neutron scattering (QENS) over a temperature range of 500–750 °C. Here, the effect of adding 0.988 mol % cerium, 0.499 mol % cesium, and 1.21 mol % zirconium individually to the dynamics of F 7 LiNaK was also investigated. The relaxation process in both pure and doped F 7 LiNaK molten salts was fit with a stretched exponential function and the temperature dependence follows an Arrhenius behavior over a wavevector transfer range of 0.4 Å –1 < Q < 0.9 Å –1 . The measured activation energy for self-diffusion is E a = 0.77 ± 0.02 eV/atom for pure molten F 7 LiNaK. The QENS response with additives added to F 7 LiNaK was also fit with a stretched exponential and the associated Arrhenius behavior was characterized with activation energies of E a = 0.88 ± 0.01 eV/atom for zirconium (1.21 mol %), E a = 1.02 ± 0.02 eV/atom for cerium (0.988 mol %), and E a = 0.71 ± 0.03 eV/atom for cesium (0.499 mol %). The measured diffusivities are compared to those simulated with a neural network force field model by Lee et al. [Lee, S.-C. Comparative Studies of the Structural and Transport Properties of Molten Salt FLiNaK Using the Machine-Learned Neural Network and Reparametrized Classical Forcefields. J. Phys. Chem. B 2021, 125(37), 10562–10570].

FLiNaK↗
DOE OSTI2024

Structural Properties of [N1888][TFSI] Ionic Liquid: A Small Angle Neutron Scattering and Polarizable Molecular Dynamics Study

In this study, we investigate the quaternary ammonium-based ionic liquid (QAIL), methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, [N 1888 ][TFSI], utilizing small angle neutron scattering (SANS) measurements and polarizable molecular dynamics (MD) simulations to characterize the shortand long-range liquid structure. Scattering structure factors show signatures of three length scales in reciprocal space indicative of alternating polarity (k ~ 0.44 Å –1 ), charge (k ~ 0.75 Å –1 ), and neighboring or adjacent (k ~ 1.46 Å –1 ) domains. Excellent agreement between simulation and experimental scattering structure factors validates various simulation analyses that provide detailed atomistic characterization of the different length scale correlations. The first solvation shell structure is illustrated by obtaining radial, angular, dihedral, and combined distribution functions, where two dominant spatial motifs, N + ···N – and N + ···O – , compete for optimal packing around the polar head of the [N 1888 ] + cation. Intermediate and long-range structures are governed by the balance between local electroneutrality and octyl chain networking, respectively. By computing the charge-correlation structure factor, S ZZ , and the spatial extent of the octyl chain network using graph theory, the bulk-phase structure of [N 1888 ][TFSI] is characterized in terms of electrostatic screening and apolar domain formation length scales.

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

Thermal neutron scattering cross sections for amorphous carbon

Carbon materials are commonly found in both nuclear reactors and experimental systems. Various carbon structures occur in nuclear applications ranging from crystalline and nuclear graphite to the amorphous carbon seen in next-generation advanced reactor designs. Amorphous carbon is based on a randomized graphite-like structure and offers the unique ability to disperse impurities throughout the bulk composition. A graphite-like amorphous carbon system was modeled using the classical molecular dynamics (MD) code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). An improved version of the temperature-dependent Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential was used to model the carbon-carbon atomic interactions for the temperature at 300 K along with densities 1.60, 1.70, 1.85, and 2.23 g/cm{sup 3}. From the normalized velocity autocorrelation function (VACF), the phonon density of state (DOS) was then calculated as the Fourier transform of the normalized VACF. This DOS was then used as the primary input for the evaluation of the thermal scattering law (TSL, i.e. S(α,β)) and associated neutron thermal scattering cross sections. The TSL was analyzed using the Full Law Analysis Scattering System Hub (FLASSH). The amorphous structure results in shifts of the phonon DOS to lower energy modes than typically displayed for ideal crystalline graphite. This impact on the DOS is directly reflected in the TSL. Furthermore, the typical optical peak at 0.25 eV for the ideal graphite disappears for amorphous carbon, in good agreement with the expected structure. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Revealing the Influence of Salts on the Hydration Structure of Ionic SDS Micelles by Contrast-Variation Small-Angle Neutron Scattering

The influence of lithium chloride (LiCl) on the hydration structure of anionic micelles of sodium dodecyl sulfate (SDS) in water was studied using the contrast-variation small-angle neutron scattering (SANS) technique. In the past, extensive computational studies have shown that the distribution of invasive water plays a critical role in the self-organization of SDS molecules and the stability of the assemblies. However, in past scattering studies the degree of the hydration level was not examined explicitly. Here, a series of contrast-variation SANS data was analyzed to extract the intramicellar radial distributions of invasive water and SDS molecules from the evolving spectral lineshapes caused by the varying isotopic ratios of water. By addressing the intramicellar inhomogeneous distributions of water and SDS molecules, a detailed description of how the counterion association influences the micellization behavior of SDS molecules is provided. The extension of our method can be used to provide an in-depth insight into the micellization phenomenon, which is commonly found in many soft matter systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Quantification of Deformation-Induced Concentration Fluctuations in Polymeric Liquids by Small-Angle Neutron Scattering

This study demonstrates how the large concentration fluctuations of polymeric liquids under deformation and flow can be quantitatively studied by applying the spherical harmonic expansion technique to small-angle neutron scattering. Using a series of binary polymer blends, it is shown that the emergence of the so-called butterfly patterns is caused by the change of sign in the leading anisotropic component of the small-angle spectrum, when the scattering is dominated by intermolecular correlation associated with flow-induced demixing. The increasing spatial fluctuations of concentration are evidenced by the enhancement of the isotropic component of the scattering spectrum in the zero-angle limit and peak shift of the leading anisotropic coefficients toward low Q. Additionally, the spherical harmonic expansion framework permits real-space analysis of anisotropic scattering length density correlation in a convenient form. The methodology described in this work provides a concrete venue for quantitative studies of phase behavior of fluids under deformation and flow via small-angle scattering techniques, where mainly qualitative approaches were previously employed.

Chemical structure↗
DOE OSTI2022

Thermal Neutron Scattering Cross Sections for Graphitic Amorphous Carbon

Carbon materials are commonly found in both nuclear reactors and experimental systems. Various carbon structures occur in nuclear applications ranging from crystalline and nuclear graphite to the amorphous carbon seen in next-generation advanced reactor designs. Amorphous carbon is based on a randomized graphite-like structure and offers the unique ability to disperse impurities throughout the bulk composition. A graphite-like amorphous carbon system was modeled using the classical molecular dynamics (MD) code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). An improved version of the temperature-dependent Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential was used to model the carbon-carbon atomic interactions for the temperature at 300 K along with densities 1.60, 1.70, 1.85, and 2.23 g/cm 3 . From the normalized velocity autocorrelation function (VACF), the phonon density of state (DOS) was then calculated as the Fourier transform of the normalized VACF. This DOS was then used as the primary input for the evaluation of the thermal scattering law (TSL, i.e. S(α,β)) and associated neutron thermal scattering cross sections. The TSL was analyzed using the Full Law Analysis Scattering System Hub (FLASSH). The amorphous structure results in shifts of the phonon DOS to lower energy modes than typically displayed for ideal crystalline graphite. This impact on the DOS is directly reflected in the TSL. Furthermore, the typical features and the optical graphitic peak at 0.25 eV for the ideal graphite DOS disappear for graphite-like amorphous carbon, which shows good agreement with the expected structure.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Monoenergetic neutron scattering on 238 U at Triangle Universities Nuclear Laboratory

In this report, we summarize the progress made in FY23 for experiments fielded at Triangle Universities Nuclear Laboratory (TUNL) of Duke University on the neutron scattering measurements of 238 U. The preliminary results on the elastic and inelastic reaction channels will be presented in addition to details of experiment and data analysis.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Two methods to study inelastic neutron-scattering measurements based on ω n (q) versus S(q, ω) applied to the magnetic open honeycomb lattice Tb 2 Ir 3 Ga 9

This work describes two methods to fit the inelastic neutron-scattering spectrum S(q, ω) with wavevector q and frequency ω. The common and well-established method extracts the experimental spin-wave branches ω n (q) from the measured spectra S(q, ω) and then minimizes the difference between the observed and predicted frequencies. When n branches of frequencies are predicted but the measured frequencies overlap to produce only m < n branches, the weighted average of the predicted frequencies must be compared to the observed frequencies. A penalty is then exacted when the width of the predicted frequencies exceeds the width of the observed frequencies. The second method directly compares the measured and predicted intensities S(q, ω) over a grid {q i , ω j } in wavevector and frequency space. After subtracting background noise from the observed intensities, the theoretical intensities are scaled by a simple wavevector-dependent function that reflects the instrumental resolution. Furthermore, the advantages and disadvantages of each approach are demonstrated by studying the open honeycomb material Tb 2 Ir 3 Ga 9 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Resonant ultrasound spectroscopy probe for in-situ neutron scattering measurements

Resonant ultrasound spectroscopy (RUS) is an efficient, nondestructive technique to study the elastic properties of solids. A low-temperature (2-300 K) probe has been assembled and tested at the NOMAD beamline at the Spallation Neutron Source at Oak Ridge National Laboratory to assess the probe's neutronic properties, data acquisition system, and compatibility with existing sample environment. A case study on a bulk metallic glass, La 65 Cu 20 Al 10 Co 5, served to benchmark both hardware and software developments. The elastic constants of the metallic glass were determined as a function of temperature between 4 and 300 K and were used to guide neutron diffraction measurements at NOMAD. Tracking of a specific RUS peak center frequency and width enabled live monitoring of the sample temperature evolution that lagged thermometry by upwards of 40 K near room temperature. Assembly of a high-temperature (300-875 K) probe is underway and both probes are scheduled to be available to users by late-2021. Our aim is to provide users with live monitoring of an intrinsic variable at the neutron scattering beamlines, in addition to existing controls, to monitor the state of their samples and its elastic moduli and make informed decisions in real time.

Torres, James↗
DOE OSTI2022

Thermal Neutron Scattering Research at ORNL – ENDF File Validation [Slides]

ENDF File Validation is a process developed to simulate VISION experiments. This method showed significant differences in inelastic spectra compared to experimental measurements. Differential data should be incorporated into thermal neutron scattering evaluation process to ensure accurate TSL files. The Polyethylene Discrepancy Issue has been found and corrected. The resulting ENDF manual change has been submitted and is currently under review.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Small-angle neutron scattering solution structures of NADPH-dependent sulfite reductase

Sulfite reductase (SiR), a dodecameric complex of flavoprotein reductase subunits (SiRFP) and hemoprotein oxidase subunits (SiRHP), reduces sulfur for biomass incorporation. Electron transfer within SiR requires intra- and inter-subunit interactions that are mediated by the relative position of each protein, governed by flexible domain movements. Using small-angle neutron scattering, we report the first solution structures of SiR heterodimers containing a single copy of each subunit. These structures show how the subunits bind and how both subunit binding and oxidation state impact SiRFP’s conformation. Neutron contrast matching experiments on selectively deuterated heterodimers allow us to define the contribution of each subunit to the solution scattering. SiRHP binding induces a change in the position of SiRFP’s flavodoxin-like domain relative to its ferredoxin-NADP + reductase domain while compacting SiRHP’s N-terminus. Reduction of SiRFP leads to a more open structure relative to its oxidized state, re-positioning SiRFP’s N-terminal flavodoxin-like domain towards the SiRHP binding position. These structures show, for the first time, how both SiRHP binding to, and reduction of, SiRFP positions SiRFP for electron transfer between the subunits.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Small-angle X-ray and neutron scattering

Small-angle scattering (SAS) is a technique that is able to probe the structural organization of matter and quantify its response to changes in external conditions. X-ray and neutron scattering profiles measured from bulk materials or materials deposited at surfaces arise from nanostructural inhomogeneities of electron or nuclear density. Furthermore, the analysis of SAS data from coherent scattering events provides information about the length scale distributions of material components. Samples for SAS studies may be prepared in situ or under near-native conditions and the measurements performed at various temperatures, pressures, flows, shears or stresses, and in a time-resolved fashion. In this Primer, we provide an overview of SAS, summarizing the types of instrument used, approaches for data collection and calibration, available data analysis methods, structural information that can be obtained using the method, and data depositories, standards and formats. Recent applications of SAS in structural biology and the soft-matter and hard-matter sciences are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Morphology of poly-3-hexyl-thiophene blends with styrene–isoprene–styrene block-copolymer elastomers from X-ray and neutron scattering

The nano- and micron scale morphology of poly(3-hexylthiophene) (P3HT) and polystyrene-block-polyisoprene-block-polystyrene (PS–PI–PS) elastomeric blends is investigated through the use of ultra-small and small angle X-ray and neutron scattering (USAXS, SAXS, SANS). It is demonstrated that loading P3HT into elastomer matrices is possible with little distortion of the elastomeric structure up to a loading of ~5 wt%. Increased loadings of conjugated polymer is found to significantly distort the matrix structure. Changes in processing conditions are also found to affect the blend morphology with especially strong dependence on processing temperature. Processing temperatures above the glass transition temperature (T g ) of polystyrene and the melting temperature (T m ) of the conjugated polymer additive (P3HT) creates significantly more organized mesophase domains. P3HT blends with PS–PI–PS can also be flow-aligned through processing, which results in an anisotropic structure that could be useful for the generation of anisotropic properties (e.g. conductivity). Moreover, the extent of flow alignment is significantly affected by the P3HT loading in the PS–PI–PS matrix. The work adds insight to the morphological understanding of a complex P3HT and PS–PI–PS polymer blend as conjugated polymer is added to the system. Here, we also provide studies isolating the effect of processing changes aiding in the understanding of the structural changes in this elastomeric conjugated polymer blend.

36 MATERIALS SCIENCE↗