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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Grain size and structure distortion characterization of α-MgAgSb thermoelectric material by powder diffraction

Nanostructuring, structure distortion and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg 0.97 Sb 0.99 , with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. In this work, we report the average grain size of 24-28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron X-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg 0.97 Sb 0.99 .

36 MATERIALS SCIENCE↗
DOE OSTI2015

Magnetic structure of the quasi-one-dimensional L a 3 Os O 7 as determined by neutron powder diffraction

Insulating 5d 3 La 3 OsO 7 and the isostructural hole-doped analog La 2.8 Ca 0.2 OsO 7 that feature pseudo-one-dimensional zigzag chains of corner-sharing OsO 6 octahedra were synthesized and their magnetic and electrical transport properties characterized. Both of these compounds are insulating antiferromagnets. Moreover, for long range magnetic order between the antiferromagnetic chains we determined with a propagation vector k = 1/2,1/2,1 and T N = 45 and 33 K the parent and doped materials. An Os 5+ moment of 1.7(1)μ B for La 3 OsO 7 and 1.2(2)μ B for La 2.8 Ca 0.2 OsO 7 is refined. The long range magnetic structure is compared to the isostructural compounds La 3 RuO 7 and La 3 MoO 7 , both of which adopt different magnetic structures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Materials synthesis, neutron powder diffraction, and first-principles calculations of (Mo x Sc 1–x ) 2 AlC i–MAX phase used as parent material for MXene derivation

Research on low-dimensional materials has increased drastically in the last decade, with the discovery of two-dimensional transition metal carbides and nitrides (MXenes) produced by atom-selective chemical etching of laminated parent M n+1 AX n (MAX) phases. In this study, we apply density functional theory and subsequent materials synthesis and analysis to explore the phase stability and Mo/Sc intermixing on the M site in the chemically ordered quaternary i-MAX phase (Mo x Sc 1-x ) 2 AlC. Transmission electron microscopy confirms the theoretical predictions of preferential in-plane ordering of Mo and Sc, with the highest crystal quality obtained for the ideal Mo:Sc ratio of 2:1 (predicted as the most stable), as well as a retained i-MAX structure even for an increased relative Sc content, with Sc partially occupying Mo sites. The results are supported by refined neutron diffraction data, which show space group C2/c (no. 15), and a C occupancy of 1. Subsequent chemical etching produces MXene for x=0.66, while for x=0.33 and 0.5 no MXene is observed. These results demonstrate that a precise control of the i-MAX composition is crucial for derivation of MXene, with a MXene quality optimized for a Mo:Sc ratio of 2:1 with minimal intermixing between Mo and Sc.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Study of Kinetics of Solid Phase Transition in Tetracosane С{sub 24}Н{sub 50} by High-Resolution Synchrotron X-Ray Powder Diffraction

Using the small-angle synchrotron X-ray diffraction method at the research facility “BELOK” of the Kurchatov synchrotron radiation source at the NRC Kurchatov Institute, it was shown that the first-order solid phase transition in tetracosane C{sub 24}H{sub 50} passes according to a heterogeneous mechanism in a narrow temperature range ΔT ~ 1 K in accordance with the theory of diffuse phase transitions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1974

X-ray powder diffraction study of poly/carbon monofluoride/, CF/1.12/

Data from X-ray diffraction studies of the poly(carbon monofluoride) with empirical formula CF(1.09-1.15) are reported, and possible intercalation arrangements for the substance are discussed. The data do not conform to true hexagonal symmetry, indicating that the carbon atoms are not coplanar. Each bond angle of carbon is 118.8 deg, and the carbon-carbon distance is 1.47 A. The interlayer distance is 5.76 A. A total absence of (hkl) reflections in the X-ray pattern shows that the separate CF layers are not regularly arranged with respect to one another.

Mahajan, V. K.↗
NASA NTRS2003

Diaplectic Glass Content in Experimentally Shock-loaded Quartz Determined by X-Ray Powder Diffraction

Quartz is the most common mineral of terrestrial crustal rocks and thus a widespread indicator for impact cratering and associated shock metamorphism. Planar deformation features (PDFs) are among the most prominent and diagnostic shock features in quartz and they represent thin lamellae of glass that formed via solid-state transformations. This socalled 'diaplectic' glass becomes pervasive at higher pressures and results in optically isotropic and X-ray-amorphous phases that resemble texturally the original quartz grains (without evidence of melt flow). In the past, it has been shown that the amount of this amorphous material in experimentally shock-loaded quartz correlates with peak shock pressure. Both reports derive the glass content from density measurements of individual crystals employing the equation X(%) = (rho(sub x) - rho(sub 0))/(rho(sub x) - rho(sub gl)), where x and 0 stands for X-ray and average (optical) density, respectively. The density of glass, rho(sub gl), was adopted as 2.2 g/cu cm. Though the same procedures had been applied, the resulting glass content differs significantly among the above studies. In the present study, we are using a new approach based solely on the integral intensity of a single, carefully selected reflection in the XRD pattern, and we will compare our data to those reported in the literature.

Skala, R.↗
NASA NTRS2004

In situ x-ray and neutron powder diffraction study of LaNi5-xSnx-H systems

This paper will present results of in situ XRD measurements of LaNi4.75Sn0.25 .during the initial absorption-desorption cycle, These measurements were performed under a similar condition to that for LaNi4.75Al0.25 previously reported [1]. The data were analyzed by the Rietveld method. Lattice parameter change and strain formation accompanying hydride phase formation and decomposition will be discussed. In addition, results of in situ neutron diffraction of LaNi4.78Sn0.22, focusing on hydrogen occupation in the hydride phase, will be presented.

metal hydrides↗
DOE OSTI2018

X-ray filter for x-ray powder diffraction

Technologies are described for apparatus, methods and systems effective for filtering. The filters may comprise a first plate. The first plate may include an x-ray absorbing material and walls defining first slits. The first slits may include arc shaped openings through the first plate. The walls of the first plate may be configured to absorb at least some of first x-rays when the first x-rays are incident on the x-ray absorbing material, and to output second x-rays. The filters may comprise a second plate spaced from the first plate. The second plate may include the x-ray absorbing material and walls defining second slits. The second slits may include arc shaped openings through the second plate. The walls of the second plate may be configured to absorb at least some of second x-rays and to output third x-rays.

36 MATERIALS SCIENCE↗
DOE OSTI2019

X-ray filter for x-ray powder diffraction

Technologies are described for apparatus, methods and systems effective for filtering. The filters may comprise a first plate. The first plate may include an x-ray absorbing material and walls defining first slits. The first slits may include arc shaped openings through the first plate. The walls of the first plate may be configured to absorb at least some of first x-rays when the first x-rays are incident on the x-ray absorbing material, and to output second x-rays. The filters may comprise a second plate spaced from the first plate. The second plate may include the x-ray absorbing material and walls defining second slits. The second slits may include arc shaped openings through the second plate. The walls of the second plate may be configured to absorb at least some of second x-rays and to output third x-rays.

Sinsheimer, John Jay↗
DOE OSTI2019

Lithium heterogeneities in cylinder-type Li-ion batteries – fatigue induced by cycling

Integrity and uniformity are crucial factors for stable, safe, robust and well-predicted operation of Li-ion batteries. The uniformity of lithium distribution in the graphite anode in fully charged state was studied by a combination of spatially-resolved time-of-flight neutron diffraction, powder diffraction using synchrotron radiation and electrochemical measurements. Studies were carried out on a series of NCA|C Li-ion cells of 18650-type with various cycle numbers. Furthermore, experimentally obtained lithium distribution under in operando and ex situ conditions have been found in fair agreement and revealed a non-uniform character of lithiation in the graphite anode in charged state, where the degree of heterogeneity increases with the number of cycles.

18650↗