Search NASA⌕ Search

SEARCH · Search NASA

Results for “diffraction”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Quantifying the inter- and intra-granular stresses and their effects on deformation behaviors for the polycrystalline hexagonal beryllium by neutron diffraction

Highlights: • The inter- and intra-granular stresses are quantified for the polycrystalline hexagonal metal beryllium. • Composite behavior of the internal stresses is revealed in the polycrystalline beryllium. • Those internal stresses show the obvious grain-orientation dependence. • Those stresses can be significantly tuned by the temperature and strain rate effects. • The dislocation slip and twinning are quantified together with the inter- and intra-granular stored energies. - Abstract: The internal stresses developing at different length scales play the important role in materials performance. This importance has been well recognized for the cubic metals, however, not for the hexagonal close-packed (hcp) ones. The present work investigates the intergranular and intragranular stresses in the polycrystalline hexagonal beryllium by neutron diffraction. The correlation between those internal stresses and the deformation mechanism is revealed, and the strain rate and temperature effects on those stresses are presented. A composite behavior of intergranular and intragranular stresses is observed, which can be significantly tuned by the temperature and strain rate effects. The intergranular stress and stored energy are large for the soft-oriented grains (SOGs), while the intragranular stress and stored energy are large for the hard-oriented ones (HOGs). Both of those stresses are significantly high for the dynamic strain rate while they are relatively low for the elevated temperature. The large internal stresses in the dynamically compressed specimen should be attributed to the large number of twins and high density of dislocations. Different HOGs-SOGs configurations are proposed on the light of those observations, which might facilitate the properties controlling and extend the application scope for the hcp metal beryllium.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Grain-resolved temperature-dependent anisotropy in hexagonal Ti-7Al revealed by synchrotron X-ray diffraction

Hexagonal metals have anisotropic coefficients of thermal expansion causing grain-level internal stresses during heating. High energy x-ray diffraction microscopy, a non-destructive, in situ, micromechanical and microstructural characterization technique, has been used to determine the anisotropic coefficients of thermal expansion (CTEs) for Ti-7Al. Two samples of polycrystalline α-phase Ti-7Al were continuously heated from room temperature to 850 °C while far-field HEDM scans were collected. The results showed a change in the ratio of the CTEs in the ‘a’ and ‘c’ directions which explains discrepancies found in the literature. The CTE additionally appears to be affected by the dissolution of α 2 precipitates. Analysis of the grain-resolved micromechanical data also shows reconfiguration of the grain scale stresses likely due to anisotropic expansion driving crystallographic slip.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Creep properties of advanced austenitic steel 709 determined through short experiments under in-situ neutron diffraction followed by TEM characterization

Here in this study, the creep mechanisms at play in Alloy 709 (Fe-20Cr-25Ni) are investigated by performing short-term creep-type tests under in-situ neutron diffraction experiments. Short tests are performed in the temperature range of 500 to 900 °C under constant load with a load ranging from 50 to 150 MPa. The creep exponent and activation energy are determined using the Bird-Mukherjee-Dorn relation and compared to that obtained from conventional longer creep tests from the literature. Scanning transmission electron microscopy (S/TEM) of the post-creep microstructure indicates that interaction of dislocations with precipitates are a dominant mechanism at play. Furthermore, local elemental mapping indicated chemical segregation at grain boundaries and formation of complex precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). Furthermore, the origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Coherent diffraction study of calcite crystallization during the hydration of tricalcium silicate

The aim of this work is using Bragg coherent X-ray diffraction imaging (BCDI) to study the calcite crystallization during carbonation of hydrated tricalcium silicate (C 3 S). Portland cement is a very complex synthesized product whose 50–70% mass is composed of C 3 S, which is the most important phase to produce calcium silicate hydrates and calcium hydroxide. Hence, its hydration contributes greatly to the hydration of cement and later to the carbonation of cement products when it reacts with CO 2 , often from the air, to form calcium carbonates. BCDI has emerged in the last decade as a promising high-resolution lens-less imaging approach for characterization of various samples. It has made significant progress with the development of X-ray sources and phase-retrieval algorithms. BCDI allows for imaging the whole three-dimensional structure of micro- and sub-micro- crystalline materials and can show the strain distribution at the nanometer spatial resolution. Finally, results show that calcite crystallization follows a through-solution reaction and the growth model of the calcite crystal can be explained by using “phase domain” theory. In conclusion, during carbonation, calcite crystals grow by increasing the number of phase domains within them while the domain size remains at about 200–300 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Helium-implantation-induced lattice strains and defects in tungsten probed by X-ray micro-diffraction

Tungsten is the main candidate material for plasma-facing armour components in future fusion reactors. Bombardment with energetic fusion neutrons causes collision cascade damage and defect formation. Interaction of defects with helium, produced by transmutation and injected from the plasma, modifies defect retention and behaviour. Here we investigate the residual lattice strains caused by different doses of helium-ion-implantation into tungsten and tungsten-rhenium alloys. Energy and depth-resolved synchrotron X-ray micro-diffraction uniquely permits the measurement of lattice strain with sub-micron 3D spatial resolution and ~10 -4 strain sensitivity. Increase of helium dose from 300 appm to 3000 appm increases volumetric strain by only ~2.4 times, indicating that defect retention per injected helium is ~3 times higher at low helium doses. This suggests defect retention is not a simple function of implanted helium dose, but strongly depends on material composition and presence of impurities. Conversely, analysis of W-1 wt% Re alloy samples and of different crystal orientations shows that both the presence of rhenium, and crystal orientation, have a comparatively small effect on defect retention. These insights are key for the design of armour components in future reactors where it will be essential to account for irradiation-induced dimensional change when predicting component lifetime and performance.

36 MATERIALS SCIENCE↗
DOE OSTI2012

X-ray powder diffraction, vibration and thermal studies of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb: Influence of mixed cationic and anionic substitutions

Graphical abstract: The structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb belong to the tetragonal {beta}-K{sub 2}SnCl{sub 6} structure type. Highlights: Black-Right-Pointing-Pointer The two new compound crystallises in P4/mnc tetragonal space group. Black-Right-Pointing-Pointer The structure is considered as isolated octahedred TeCl{sub 4}Br{sup 2-}. Black-Right-Pointing-Pointer The octahedra connected by ionic and hydrogen bonding through the Cs/Rb or N atoms. Black-Right-Pointing-Pointer A DTA/TGA experiment reveals one endothermic peak at 780 K for these compounds. Black-Right-Pointing-Pointer One endothermic peak is detected at around 213 K by DSC experiment. -- Abstract: The crystal structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb have been determined using X-ray powder diffraction techniques. The two compounds crystallize in the tetragonal space group P4/mnc, with the unit cell parameters: a = 7.452(1) Angstrom-Sign , c = 10.544(3) Angstrom-Sign , Z = 2 and a = 7.315(2) Angstrom-Sign , c = 10.354(4) Angstrom-Sign , Z = 2 in the presence of Cs and Rb, respectively. These two compounds have an antifluorite-type arrangement of NH{sub 4}{sup +}/Rb{sup +}/Cs{sup +} and octahedral TeCl{sub 4}Br{sub 2}{sup 2-} anions. The stability of these structure is by ionic and hydrogen bonding contacts: A Midline-Horizontal-Ellipsis Cl, A Midline-Horizontal-Ellipsis Br and N-H Midline-Horizontal-Ellipsis Cl, N-H Midline-Horizontal-Ellipsis Br. The different vibrational modes of these powders were analysed by FTIR and Raman spectroscopic studies. A DTA/TGA experiment reveals one endothermic peak at 780 K implicating the decomposition of the sample. At low temperature, one endothermic peak in thermal behavior is detected at around 213 K by DSC experiment. This transition was confirmed by dielectric measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Neutron diffraction and magnetic study of the low-temperature transitions in SrMo{sub 1−x}Fe{sub x}O{sub 3−δ}

Highlights: ► SrMo{sub 1−x}Fe{sub x}O{sub 3−δ} (x = 0, 0.1, 0.2 and 0.3) were obtained as polycrystalline powders. ► Cooling, two structural transitions are identified, tetragonal and orthorhombic. ► DSC curves exhibit an endothermic peak close to 240 K. ► Magnetic behavior of the samples changes, inducing a ferromagnetic character. ► The tilt angles are appreciably high at low temperatures. -- Abstract: SrMo{sub 1−x}Fe{sub x}O{sub 3−δ} (x = 0, 0.1, 0.2 and 0.3) perovskites have recently been described as performing anode materials in solid-oxide fuel cells. In this work, we describe the structural phase transitions they undergo below room-temperature (RT), studied “in-situ” from neutron powder diffraction data and DSC measurements. At RT all the studied compositions are cubic, space group Pm-3m, with unit-cell parameters that decrease with Fe doping. Upon cooling the samples, two structural phase transitions are identified: one to a tetragonal structure with I4/mcm space group (around T{sub 1} = 240 K), and the second one to an orthorhombic Imma phase below T{sub 2} = 100 K. The magnetic properties have also been evaluated; the Fe substitution drives an evolution from a Pauli-paramagnetic state (x = 0) to a weak ferromagnetic state combined with antiferromagnetic interactions; the susceptibility and the saturation magnetization increases monotonically with increasing the Fe-doping content.

36 MATERIALS SCIENCE↗
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 OSTI2014

Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2014

In situ high-pressure synchrotron X-ray diffraction study of the structural stability in NdVO{sub 4} and LaVO{sub 4}

Highlights: • NdVO{sub 4} and LaVO{sub 4} were studied under high pressure using synchrotron powder XRD. • Both compounds exhibit first-order phase transitions. • In NdVO{sub 4} the transition involves a symmetry breaking and in LaVO{sub 4} is isomorphic. • The crystal structures of the high-pressure phases are assigned. • Axial and bulk compressibilities are determined. - Abstract: Room-temperature angle-dispersive X-ray diffraction measurements on zircon-type NdVO{sub 4} and monazite-type LaVO{sub 4} were performed in a diamond-anvil cell up to 12 GPa. In NdVO{sub 4}, we found evidence for a non-reversible pressure-induced structural phase transition from zircon to a monazite-type structure at 6.5 GPa. Monazite-type LaVO{sub 4} also exhibits a phase transition but at 8.6 GPa. In this case the transition is reversible and isomorphic. In both compounds the pressure induced transitions involve a large volume collapse. Finally, the equations of state and axial compressibilities for the low-pressure phases are also determined.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and optical effects induced by gamma irradiation on NdPO{sub 4}: X-ray diffraction, spectroscopic and luminescence study

Highlights: • Inorganic NdPO{sub 4} crystal was grown first time using potassium polyphosphate (K{sub 6}P{sub 4}O{sub 13}) flux. • NdPO{sub 4} crystal is insoluble in water, non-hygroscopic and high radiation resistance favoring for actinides host. • Actinide immobilization can be made at 1273 K. • High yield of 1061 nm photon emission. - Abstract: Rare earth orthophosphate (NdPO{sub 4}) monazite single crystals were grown using high temperature flux growth method employing K{sub 6}P{sub 4}O{sub 13} (K{sub 6}) as molten solvent. Their structural parameters were studied using single crystal X-ray diffraction (XRD) method. The grown crystals were examined by SEM and EDX techniques for their homogeniousity and inclusion in the crystals. The influence of gamma irradiation in structural and optical absorption properties were studied by the powder XRD, FTIR and reflectance spectroscopy. The effect of gamma irradiation on luminescence properties was recorded. No significant structural change is observed up to 150 kGy gamma dose. The gamma ray induced charge trap in the crystal was saturated to 40 kGy dose. The luminescence intensity decreases with an increase in the irradiation. The emission of luminescence intensity stabilizes above 40 kGy gamma dose.

36 MATERIALS SCIENCE↗
DOE OSTI2017

In situ neutron diffraction analyses of temperature and stresses during friction stir processing of Mg-3Al-1Zn magnesium alloy

In this paper, the evolution of temperature and thermal stresses were examined during friction stir processing of a magnesium alloy using in situ neutron diffraction. Measured total lattice strains were de-convoluted into the thermal and stress components. Finally, it shows the maximum temperature of 464 °C and compressive stress distributions up to -52 MPa underneath the tool via the thermo-mechanical deformation in terms of the Zener-Hollomon parameter of 4.51 × 10 10 s -1 .

36 MATERIALS SCIENCE↗
DOE OSTI2025

Residual stress distribution in an additively manufactured complex structure by neutron diffraction measurement

Residual stress in an aerodynamically shaped Ni-based superalloy airfoil fabricated by laser powder bed fusion was measured by neutron diffraction. The experiment was conducted by considering the complex shape, implementing computer aided experiment planning, and automatic alignment at each rapid measurement. The 3-dimensional (3D) residual stress distribution in the airfoil is presented in this work, which lacks symmetry due to the complex geometry of the airfoil. In conclusion, the results provide theoretical thermal processing models a complete residual stress dataset of simulation validation on 3D shape complex structure.

Residual stress↗
DOE OSTI2023

Probing lead acetate in solution using X-ray diffraction

Here, for the purpose of water purification involving toxic metal sensing and removal, high energy X-ray diffraction experiments have been performed on lead acetate Pb(Ac) 2 solutions, liquid and amorphous glutathione disulfide (GSSG), and their mixtures. The data have been interpreted using Empirical Potential Structure Refinement and pair distribution function analysis. At the highest concentration of 1 M Pb(Ac) 2 in water, the lead molecules are found to cluster and the second shell in the water structure becomes slightly more ordered as the water molecules become compressed. Liquid and amorphous GSSG are found to hydrogen bond primarily via OH-O interactions, while NH-O bonds are much more distorted. Aqueous solutions of Pb(Ac) 2 + GSSG show the closest Pb-O (carboxyl) and Pb-N (amine) bonds both at a distance of 2.5 ± 0.1 Å at a concentration of 1 M Pb(Ac) 2 in water. At 0.75 M Pb(Ac) 2 in water, strong Pb-S bonds are found at a distance of 2.8 ± 0.1 Å. The implications for lead removal using capacitive deionization are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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 OSTI2017

Study on the residual stress relaxation in girth-welded steel pipes under bending load using diffraction methods

This research is dedicated to the experimental investigation of the residual stress relaxation in girth-welded pipes due to quasi-static bending loads. Ferritic-pearlitic steel pipes are welded with two passes, resulting in a characteristic residual stress state with high tensile residual stresses at the weld root. Also, four-point bending is applied to generate axial load stress causing changes in the residual stress state. These are determined both on the outer and inner surfaces of the pipes, as well as in the pipe wall, using X-ray and neutron diffraction. Focusing on the effect of tensile load stress, it is revealed that not only the tensile residual stresses are reduced due to exceeding the yield stress, but also the compressive residual stresses for equilibrium reasons. Furthermore, residual stress relaxation occurs both parallel and perpendicular to the applied load stress.

36 MATERIALS SCIENCE↗
DOE OSTI2018

In situ neutron diffraction in quantifying deformation behaviors of nano-sized carbide strengthened UFG ferritic steel

Here, the microstructures and mechanical properties of a low-alloy medium-carbon steel with a duplex microstructure composed of nanoscale spheroidized carbides in ultrafine-grained (UFG) ferritic steel are examined. The average grain size of the studied steel is ~ 430 nm, and these grains coexist with numerous carbides. Neutron diffraction reveals that the intensity of (011) and (022) peaks for the UFG sample is significantly enhanced, suggesting that the (011)//RD texture is a result of the warm rolling process. The lattice parameter of UFG steel is smaller than that of a martensitic steel (M steel) counterpart, indicating a lower carbon concentration in the lattice. The estimated dislocation densities for M steel and UFG steel are 2.59 × 10 14 cm –2 and 1.76 × 10 12 cm –2 , respectively. The UFG steel reveals a nearly isotropic lattice strain response under initial tension from 0 to 450 MPa, where the lattice strains of the (110), (002), and (112) planes are identical. The increase of lattice strain of the (110) plane becomes smaller than that of the (002) and (112) planes as the stress exceeds 450 MPa, suggesting that the nanosized carbides contribute to the hardening ability by promoting the accumulation of geometrically necessary dislocations around the particles, and the (110) lattice becomes harder compared to the other two planes.

36 MATERIALS SCIENCE↗