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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Multi-angle Precession Electron Diffraction (MAPED): A Versatile Approach to 4D-STEM Precession

Precession of a converged beam during acquisition of a 4D-STEM dataset improves strain, orientation, and phase mapping accuracy by averaging over continuous angles of illumination. Precession experiments usually rely on integrated systems, where automatic alignments lead to fast, high-quality results. The dependence of these experiments on specific hardware and software is evident even when switching to nonintegrated detectors on a precession tool, as experimental set-up becomes challenging and time-consuming. Here, we introduce multi-angle precession electron diffraction (MAPED): a method to perform electron diffraction by collecting sequential 4D-STEM scans at different incident beam tilts. The multiple diffraction datasets are averaged together postacquisition, resulting in a single dataset that minimizes the impact of the curvature and orientation of the Ewald sphere relative to the crystal under study. Our results demonstrate that even four additional tilts improved measurement of material properties, namely strain and orientation, as compared to single-tilt 4D-STEM experiments. We show the versatility and flexibility of our MAPED approach with data collected on a number of microscopes with different hardware configurations and a variety of detectors.

4D-STEM↗
DOE OSTI2024

Prediction of photodynamics of 200 nm excited cyclobutanone with linear response electronic structure and ab initio multiple spawning

Simulations of photochemical reaction dynamics have been a challenge to the theoretical chemistry community for some time. In an effort to determine the predictive character of current approaches, we predict the results of an upcoming ultrafast diffraction experiment on the photodynamics of cyclobutanone after excitation to the lowest lying Rydberg state (S 2 ). A picosecond of nonadiabatic dynamics is described with ab initio multiple spawning. Herein we use both time dependent density functional theory (TDDFT) and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) theory for the underlying electronic structure theory. We find that the lifetime of the S 2 state is more than a picosecond (with both TDDFT and EOM-CCSD). The predicted ultrafast electron diffraction spectrum exhibits numerous structural features, but weak time dependence over the course of the simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Spatially resolved texture and microstructure evolution of additively manufactured and gas gun deformed 304L stainless steel investigated by neutron diffraction and electron backscatter diffraction

In this study, we report the characterization of a 304L stainless steel cylindrical projectile produced by additive manufacturing. The projectile was compressively deformed using a Taylor Anvil Gas Gun, leading to a huge strain gradient along the axis of the deformed cylinder. Spatially resolved neutron diffraction measurements on the HIgh Pressure Preferred Orientation time-of-flight diffractometer (HIPPO) and Spectrometer for Materials Research at Temperature and Stress diffractometer (SMARTS) beamlines at the Los Alamos Neutron Science CEnter (LANSCE) with Rietveld and single-peak analysis were used to quantitatively evaluate the volume fractions of the α, γ, and ε phases as well as residual strain and texture. The texture of the γ phase is consistent with uniaxial compression, while the α texture can be explained by the Kurdjumov–Sachs relationship from the γ texture after deformation. This indicates that the material first deformed in the γ phase and subsequently transformed at larger strains. The ε phase was only found in volumes close to the undeformed material with a texture connected to the γ texture by the Shoji–Nishiyama orientation relationship. This allows us to conclude that the ε phase occurs as an intermediate phase at lower strain, and is superseded by the α phase when strain increases further. Furthe, we found a proportionality between the root-mean-squared microstrain of the γ phase, dominated by the dislocation density, with the α volume fraction, consistent with strain-induced martensite α formation. In conclusion, knowledge of the sample volume with the ε phase from the neutron diffraction analysis allowed us to identify the ε phase by electron back scatter diffraction analysis, complementing the neutron diffraction analysis with characterization on the grain level.

304L stainless steel↗
DOE OSTI2014

Perspective: Structural dynamics in condensed matter mapped by femtosecond x-ray diffraction

Ultrashort soft and hard x-ray pulses are sensitive probes of structural dynamics on the picometer length and femtosecond time scales of electronic and atomic motions. Recent progress in generating such pulses has initiated new directions of condensed matter research, exploiting a variety of x-ray absorption, scattering, and diffraction methods to probe photoinduced structural dynamics. Atomic motion, changes of local structure and long-range order, as well as correlated electron motion and charge transfer have been resolved in space and time, providing a most direct access to the physical mechanisms and interactions driving reversible and irreversible changes of structure. This perspective combines an overview of recent advances in femtosecond x-ray diffraction with a discussion on ongoing and future developments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Thermal conductivity control by oxygen defect concentration modification in reducible oxides: The case of Pr{sub 0.1}Ce{sub 0.9}O{sub 2−δ} thin films

We demonstrate the impact on thermal conductivity of varying the concentration of oxygen vacancies and reduced cations in Pr{sub 0.1}Ce{sub 0.9}O{sub 2−δ} thin films prepared by pulsed laser deposition. The oxygen vacancy concentration is controlled by varying the oxygen partial pressure between 1 × 10{sup −4} and 1 atm at 650 °C. Corresponding changes in the oxygen non-stoichiometry (δ) are monitored by detecting the lattice parameters of the films with high-resolution X-ray diffraction, while the thermal properties are characterized by time-domain thermoreflectance measurements. The films are shown to exhibit a variation in oxygen vacancy content, and in the Pr{sup 3+}/Pr{sup 4+} ratio, corresponding to changes in δ from 0.0027 to 0.0364, leading to a reduction in the thermal conductivity from k = 6.62 ± 0.61 to 3.82 ± 0.51 W/m-K, respectively. These values agree well with those predicted by the Callaway and von Baeyer model for thermal conductivity in the presence of point imperfections. These results demonstrate the capability of controlling thermal conductivity via control of anion and cation defect concentrations in a given reducible oxide.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1988

Evaluation and application of a new interferometry technique for compressible flow research

A new method for obtaining large scale interferograms of flow fields in real time was investigated. The method was based on the point diffraction interferometry technique. The method was modified to accommodate the higher laser power required in recording transonic and supersonic flow fields. Basic tests were conducted in unsteady flows and flows about circulation control airfoils at transonic speeds. It was found that vibration was not a significant factor in the application of the system. In the case of the circulation control airfoils, the real-time viewing allowed the identification of the Coanda jet interaction with the external flow and the shedding of large scale vortices. The method proved to be very sensitive to the optical quality of the wind tunnel windows. The results obtained were compared with earlier interferograms obtained using interferometry. These results were in qualitative agreement.

Bachalo, William D.↗
NASA NTRS2015

Double-Diffusive Convection During Growth of Halides and Selenides

Heavy metal halides and selenides have unique properties which make them excellent materials for chemical, biological and radiological sensors. Recently it has been shown that selenohalides are even better materials than halides or selenides for gamma-ray detection. These materials also meet the strong needs of a wide band imaging technology to cover ultra-violet (UV), midwave infrared wavelength (MWIR) to very long wavelength infrared (VLWIR) region for hyperspectral imager components such as etalon filters and acousto-optic tunable filters (AO). In fact AOTF based imagers based on these materials have some superiority than imagers based on liquid crystals, FTIR, Fabry-Perot, grating, etalon, electro-optic modulation, piezoelectric and several other concepts. For example, broadband spectral and imagers have problems of processing large amount of information during real-time observation. Acousto-Optic Tunable Filter (AOTF) imagers are being developed to fill the need of reducing processing time of data, low cost operation and key to achieving the goal of covering long-wave infrared (LWIR). At the present time spectral imaging systems are based on the use of diffraction gratings are typically used in a pushbroom or whiskbroom mode. They are mostly used in systems and acquire large amounts of hyperspectral data that is processed off-line later. In contrast, acousto-optic tunable filter spectral imagers require very little image processing, providing new strategies for object recognition and tracking. They are ideally suited for tactical situations requiring immediate real-time image processing. But the performance of these imagers depends on the quality and homogeneity of acousto-optic materials. In addition for many systems requirements are so demanding that crystals up to sizes of 10 cm length are desired. We have studied several selenides and halide crystals for laser and AO imagers for MWIR and LWIR wavelength regions. We have grown and fabricated crystals of several materials such as mercurous chloride, mercurous bromide, mercurous iodide, lead chloride lead bromide, lead iodide, thallium arsenic selenide, gallium selenide, zince sulfide zinc selenide and several crystals into devices. We have used both Bridgman and physical vapor transport (PVT) crystal growth methods. In the past have examined PVT growth numerically for conditions where the boundary of the enclosure is subjected to a nonlinear thermal profile. Since past few months we have been working on binary and ternary materials such as selenoiodides, doped zinc sulfides and mercurous chloro bromide and mercurous bromoiodides. In the doped and ternary materials thermal and solutal convection play extremely important role during the growth. Very commonly striations and banding is observed. Our experiments have indicated that even in highly purified source materials, homogeneity in 1-g environment is very difficult. Some of our previous numerical studies have indicated that gravity level less than 10-4 (-g) helps in controlling the thermosolutal convection. We will discuss the ground based growth results of HgClxBr(1-x) and ZnSe growth results for the mm thick to large cm size crystals. These results will be compared with our microgravity experiments performed with this class of materials. For both HgCl-HgBr and ZnS-ZnSe the lattice parameters of the mixtures obey Vagard's law in the studied composition range. The study demonstrates that properties are very anisotropic with crystal orientation, and performance achievement requires extremely careful fabrication to utilize highest figure of merit. In addition, some parameters such as crystal growth fabrication, processing time, resolution, field of view and efficiency will be described based on novel solid solution materials. It was predicted that very similar to the pure compounds solid solutions also have very large anisotropy, and very precise oriented and homogeneous bulk and thin film crystals is required to achieve maximum performance of laser or imagers. Some of the parameters controlling the homogeneity such as thermos-solutal convection driven forces can be controlled in microgravity environments to utilize the benefits of these unique materials.

Singh, N. B.↗
DOE OSTI2016

Growth of highly strained CeO 2 ultrathin films

Large biaxial strain is a promising route to tune the functionalities of oxide thin films. However, large strain is often not fully realized due to the formation of misfit dislocations at the film/substrate interface. In this work, we examine the growth of strained ceria (CeO 2 ) thin films on (001)-oriented single crystal yttria-stabilized zirconia (YSZ) via pulsed-laser deposition. By varying the film thickness systematically between 1 and 430 nm, we demonstrate that ultrathin ceria films are coherently strained to the YSZ substrate for thicknesses up to 2.7 nm, despite the large lattice mismatch (~5%). The coherency is confirmed by both X-ray diffraction and high-resolution transmission electron microscopy. This thickness is several times greater than the predicted equilibrium critical thickness. Partial strain relaxation is achieved by forming semirelaxed surface islands rather than by directly nucleating dislocations. In situ reflective high-energy electron diffraction during growth confirms the transition from 2-D (layer-by-layer) to 3-D (island) at a film thickness of ~1 nm, which is further supported by atomic force microscopy. We propose that dislocations likely nucleate near the surface islands and glide to the film/substrate interface, as evidenced by the presence of 60° dislocations. Finally, an improved understanding of growing oxide thin films with a large misfit lays the foundation to systematically explore the impact of strain and dislocations on properties such as ionic transport and redox chemistry.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

An ultrasensitive Medipix2 detector allowed the collection of rotation electron-diffraction data from single three-dimensional protein nanocrystals for the first time. The data could be analysed using the standard X-ray crystallography programs MOSFLM and SCALA. When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e{sup −} Å{sup −2}), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

A pulse-front-tilt–compensated streaked optical spectrometer with high throughput and picosecond time resolution

A high-throughput, broadband optical spectrometer coupled to the Rochester optical streak system equipped with a Photonis P820 streak tube was designed to record time-resolved spectra with 1-ps time resolution. Spectral resolution of 0.8 nm is achieved over a wavelength coverage range of 480 to 580 nm, using a 300-groove/mm diffraction grating in conjunction with a pair of 225-mm-focal-length doublets operating at an f/2.9 aperture. Overall pulse-front tilt across the beam diameter generated by the diffraction grating is reduced by preferentially delaying discrete segments of the collimated input beam using a 34-element reflective echelon optic. The introduced delay temporally aligns the beam segments and the net pulse-front tilt is limited to the accumulation across an individual sub-element. The resulting spectrometer design balances resolving power and pulse-front tilt while maintaining high throughput.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Unusual Breathing Behavior of Optically Excited Barium Titanate Nanocrystals

Coherent X-ray diffraction patterns were recorded by using an X-ray free-electron laser to illuminate barium titanate nanocrystals as a function of time delay after laser excitation. Rather than seeing any significant thermal expansion effects, the diffraction peaks were found to move perpendicular to the momentum transfer direction. This suggests a laser driven rotation of the crystal lattice, which is delayed by the aggregated state of the crystals. Internal deformations associated with crystal contacts were also observed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Accurate rotational constant and bond lengths of hexafluorobenzene by femtosecond rotational Raman coherence spectroscopy and ab initio calculations

The gas-phase rotational motion of hexafluorobenzene has been measured in real time using femtosecond (fs) time-resolved rotational Raman coherence spectroscopy (RR-RCS) at T = 100 and 295 K. This four-wave mixing method allows to probe the rotation of non-polar gas-phase molecules with fs time resolution over times up to ∼5 ns. The ground state rotational constant of hexafluorobenzene is determined as B{sub 0} = 1029.740(28) MHz (2σ uncertainty) from RR-RCS transients measured in a pulsed seeded supersonic jet, where essentially only the v = 0 state is populated. Using this B{sub 0} value, RR-RCS measurements in a room temperature gas cell give the rotational constants B{sub v} of the five lowest-lying thermally populated vibrationally excited states ν{sub 7/8}, ν{sub 9}, ν{sub 11/12}, ν{sub 13}, and ν{sub 14/15}. Their B{sub v} constants differ from B{sub 0} by between −1.02 MHz and +2.23 MHz. Combining the B{sub 0} with the results of all-electron coupled-cluster CCSD(T) calculations of Demaison et al. [Mol. Phys. 111, 1539 (2013)] and of our own allow to determine the C-C and C-F semi-experimental equilibrium bond lengths r{sub e}(C-C) = 1.3866(3) Å and r{sub e}(C-F) = 1.3244(4) Å. These agree with the CCSD(T)/wCVQZ r{sub e} bond lengths calculated by Demaison et al. within ±0.0005 Å. We also calculate the semi-experimental thermally averaged bond lengths r{sub g}(C-C)=1.3907(3) Å and r{sub g}(C-F)=1.3250(4) Å. These are at least ten times more accurate than two sets of experimental gas-phase electron diffraction r{sub g} bond lengths measured in the 1960s.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Role of intensive milling in the processing of barium ferrite/magnetite/iron hybrid magnetic nano-composites via partial reduction of barium ferrite

In this research a mixture of barium ferrite and graphite was milled for different periods of time and then heat treated at different temperatures. The effects of milling time and heat treatment temperature on the phase composition, thermal behavior, morphology and magnetic properties of the samples have been investigated using X-ray diffraction, differential thermal analysis, high resolution transmission electron microscopy and vibrating sample magnetometer techniques, respectively. X-ray diffraction results revealed that BaFe{sub 12}O{sub 19}/Fe{sub 3}O{sub 4} nanocomposites form after a 20 h milling due to the partial reduction of BaFe{sub 12}O{sub 19}. High resolution transmission electron microscope images of a 40 h milled sample showed agglomerated structure consisting of nanoparticles with a mean particle size of 30 nm. Thermal analysis of the samples via differential thermal analysis indicated that for un-milled samples, heat treatment up to 900 °C did not result in α-Fe formation, while for a 20 h milled sample heat treatment at 700 °C resulted in reduction process progress to the formation of α-Fe. Wustite was disappeared in an X-ray diffraction pattern of a heat treated sample at 850 °C, by increasing the milling time from 20 to 40 h. By increasing the milling time, the structure of heat treated samples becomes magnetically softer due to an increase in saturation magnetization and a decrease in coercivity. Saturation magnetization and coercivity of a sample milled for 20 h and heat treated at 850 °C were 126.3 emu/g and 149.5 Oe which by increasing the milling time to 40 h, alter to 169.1 emu/g and 24.3 Oe, respectively. High coercivity values of milled and heat treated samples were attributed to the nano-scale formed iron particles. - Graphical abstract: Display Omitted - Highlights: • Barium ferrite and graphite were treated mechano-thermally. • Increasing milling time increases reduction progress after heat treatment. • Composites including iron nano-crystals forms by milling and heat treatment. • Shorter milling time results in higher H{sub C} of the milled and heat treated samples.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

From chiral anomaly to two-fluid hydrodynamics for electronic vortices

Highlights: • Chiral transformations with account for chiral anomaly were applied to the CDW model. • Two-fluid hydrodynamics was constructed of the order parameter and the normal liquid. • Topologically nontrivial dynamics appears under applied fields or charge injection. • Spontaneous spacetime vorticity under the driving current was modeled numerically. • Periodic sequence of amplitude nodes with 2π phase increments was demonstrated. - Abstract: Many recent experiments addressed manifestations of electronic crystals, particularly the charge density waves, in nano-junctions, under electric field effect, at high magnetic fields, together with real space visualizations by STM and micro X-ray diffraction. This activity returns the interest to stationary or transient states with static and dynamic topologically nontrivial configurations: electronic vortices as dislocations, instantons as phase slip centers, and ensembles of microscopic solitons. Describing and modeling these states and processes calls for an efficient phenomenological theory which should take into account the degenerate order parameter, various kinds of normal carriers and the electric field. Here we notice that the commonly employed time-depend Ginzburg–Landau approach suffers with violation of the charge conservation law resulting in unphysical generation of particles which is particularly strong for nucleating or moving electronic vortices. We present a consistent theory which exploits the chiral transformations taking into account the principle contribution of the fermionic chiral anomaly to the effective action. The resulting equations clarify partitions of charges, currents and rigidity among subsystems of the condensate and normal carriers. On this basis we perform the numerical modeling of a spontaneously generated coherent sequence of phase slips – the spacetime vortices – serving for the conversion among the injected normal current and the collective one.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Neutron diffraction: a primer

Because of the neutron’s special properties, neutron diffraction may be considered one of the most powerful techniques for structure determination of crystalline and related matter. Neutrons can be released from nuclear fission, from spallation processes, and also from low-energy nuclear reactions, and they can then be used in powder, time-of-flight, texture, single crystal, and other techniques, all of which are perfectly suited to clarify crystal and magnetic structures. With high neutron flux and sufficient brilliance, neutron diffraction also excels for diffuse scattering, for in situ and operando studies as well as for high-pressure experiments of today’s materials. For these, the wave-like neutron’s infinite advantage (isotope specific, magnetic) is crucial to answering important scientific questions, for example, on the structure and dynamics of light atoms in energy conversion and storage materials, magnetic matter, or protein structures. In this primer, we summarize the current state of neutron diffraction (and how it came to be), but also look at recent advances and new ideas, e.g., the design of new instruments, and what follows from that.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Domain Texture of the Orthorhombic Phase of La 2-x Ba x CuO 4

Bragg Coherent Diffraction Imaging (BCDI) experiments have been carried out at the Advanced Photon Source using a new cryostat system developed to achieve high mechanical stability and low vibrations. Here, we measured the (012) LTO Bragg peak which is unique to the low-temperature orthorhombic (LTO) phase of micron-sized crystals of the High-temperature Superconductor La 2-x Ba x CuO 4 (LBCO) to study the formation of structural domains. Each time the sample was cooled into the orthorhombic phase, the diffraction pattern of domains was different. Finally, this confirms the interpretation of pinning of the lower-temperature Charge Density Wave domains observed in coherent resonant X-ray speckle correlation analysis experiments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Structural and optical studies of chemically deposited Sn{sub 2}S{sub 3} thin films

Highlights: ► Sn{sub 2}S{sub 3} films were deposited at 30 °C by chemical bath deposition. ► The deposition time of the chemical bath was adjusted to 20 h, 22 h, and 24 h. ► Effect of deposition time on structural and optical properties of Sn{sub 2}S{sub 3} thin films were investigated. ► The presence of characteristic bonds of Sn{sub 2}S{sub 3} was observed from Raman shift experiment. ► The direct band gap of thin films constant were calculated. -- Abstract: Sn{sub 2}S{sub 3} thin films were grown on commercial glass substrates by chemical bath deposition at room temperature. The structural and optical properties of Sn{sub 2}S{sub 3} thin films were studied as a function of deposition time. The thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and UV–vis spectroscopy. The XRD pattern showed that the Sn{sub 2}S{sub 3} thin films had an orthorhombic polycrystalline structure. The lattice constants of the thin films were a = 8.741 Å, b = 14.034 Å and c = 3.728 Å. The characteristic bonds of Sn{sub 2}S{sub 3} were observed at 66.3, 111.7, 224.7 and 308.9 cm{sup −1} using Raman shift experiment. The optical energy band gap of the thin films decreased from 2.12 eV to 2.03 eV with increasing deposition time from 20 to 24 h. The optical constants of the thin films were obtained using the experimentally recorded transmission data as a function of the wavelength.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Femtosecond diffraction studies of the sodium chloride phase diagram under laser shock compression

The phase diagram of sodium chloride (NaCl) under laser shock compression has been studied at Linac Coherent Light Source (LCLS) at the x-ray free-electron laser facility. Both solid–solid (B1 → B2) and solid–liquid (B2 → liquid) transitions have been observed along the Hugoniot over nanosecond time scales. By combining structural measurements through in situ x-ray diffraction, pressure determination through velocimetry, and a thermal equation-of-state, the shock-compressed data are used to constrain the phase diagram of NaCl. Transformation into the B2 phase is found to occur at 28(2) GPa, and B2–liquid coexistence is observed between 54(4) and 66(6) GPa, with near full melt at 66(6) GPa. Late-time pressure release from an initial shocked B2-state results in a B2 → B1 back transformation. Our results show agreement with previous static compression data, suggesting that the time scale for melting is very rapid and that equilibrium states in NaCl are being accessed over nanosecond time scales. Finally, a multiphase equation-of-state description of NaCl incorporated into a one-dimensional hydrocode is used to interpret pressure and temperature evolution over these rapid time scales.

36 MATERIALS SCIENCE↗