Search NASA⌕ Search

SEARCH · Search NASA

Results for “diffraction in time”

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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Effects of sulfurization time and H{sub 2}S concentration on electrical properties of Cu{sub 2}ZnSnS{sub 4} films prepared by sol–gel method

Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) films were prepared by sol–gel method following sulfurization. • The sulfurization time and H{sub 2}S concentration have the effects on the electrical properties. • The tin loss is increased with the increasing of the sulfurization time. • The secondary phases like ZnS make the electrical properties worse. • The CZTS films sulfurized at 5% H{sub 2}S for 90 min had the best electrical properties. - Abstract: Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films have been successfully deposited by a sol–gel method and sulfurization process. The properties of the films were investigated by varying sulfurization time and H{sub 2}S concentration. X-ray diffraction and Raman spectra analyses revealed the formation of CZTS films with a tetragonal type kesterite structure. With increasing the sulfurization time and H{sub 2}S concentration, the intensity of the kesterite (1 1 2) peak became sharper. The stoichiometric ratios of the CZTS films were different from the precursors, which was due to Sn loss during the sulfurization process. The electrical resistivity and mobility of the films increased while the carrier concentration decreased with increasing the sulfurization time. The CZTS thin films sulfurized at 5% H{sub 2}S concentration for 90 min had the best opto-electrical properties with E{sub g} of 1.41 eV, resistivity of 3.64 Ω cm, carrier concentration of 1.11 × 10{sup 18} cm{sup −3} and mobility of 1.54 cm{sup 2}/(V s) at room temperature for PV application.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Studies on atomic layer deposition of IRMOF-8 thin films

Deposition of IRMOF-8 thin films by atomic layer deposition was studied at 260–320 °C. Zinc acetate and 2,6-naphthalenedicarboxylic acid were used as the precursors. The as-deposited amorphous films were crystallized in 70% relative humidity at room temperature resulting in an unknown phase with a large unit cell. An autoclave with dimethylformamide as the solvent was used to recrystallize the films into IRMOF-8 as confirmed by grazing incidence x-ray diffraction. The films were further characterized by high temperature x-ray diffraction (HTXRD), field emission scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), time-of-flight elastic recoil detection analysis (TOF-ERDA), nanoindentation, and energy-dispersive x-ray spectroscopy. HTXRD measurements revealed similar behavior to bulk IRMOF-8. According to TOF-ERDA and FTIR, composition of the films was similar to IRMOF-8. Through-porosity was confirmed by loading the films with palladium using Pd(thd){sub 2} (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) as the precursor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1981

High temperature cyclic oxidation furnace testing at NASA Lewis Research Center

A standardized method of testing the cyclic oxidation resistance of various alloys in static air up to 1200 C has been developed and routinely used at the NASA Lewis Research Center. Test samples are automatically raised and lowered into a resistance wound furnace for a series of fixed-interval heating and cooling cycles. Spall catchers collect the accumulated spall from each sample. The samples are weighed intermittently to generate specific weight change with time data. At various test times the samples and the accumulated spall are analyzed by X-ray diffraction. A computer program is used to print out the specific weight change versus time data and the X-ray data in tabular form and to plot the specific weight change versus time data in a publishable format. The data are also organized and indexed. So far several hundred Fe-, Ni-, and Co-base alloys have been tested using this basic procedure and will form the basis of a series of cyclic oxidation handbooks to be published by NASA. Such specific weight change/time data have been used to estimate the oxidative metal consumption by several computer modeling techniques both to rank alloys and to estimate life.

Barrett, C. A.↗
DOE OSTI2019

Ultrafast photonic micro-systems to manipulate hard X-rays at 300 picoseconds

Time-resolved and ultrafast hard X-ray imaging, scattering and spectroscopy are powerful tools for elucidating the temporal and spatial evolution of complexity in materials. However, their temporal resolution has been limited by the storage-ring timing patterns and X-ray pulse width at synchrotron sources. Here we demonstrate that dynamic X-ray optics based on micro-electro-mechanical-system resonators can manipulate hard X-ray pulses on time scales down to 300 ps, comparable to the X-ray pulse width from typical synchrotron sources. This is achieved by timing the resonators with the storage ring to diffract X-ray pulses through the narrow Bragg peak of the single-crystalline material. Angular velocities exceeding 10 7 degrees s -1 are reached while maintaining the maximum linear velocity well below the sonic speed and material breakdown limit. As the time scale of the devices shortens, the devices promise to spatially disperse the temporal width of X-rays, thus generating a temporal resolution below the pulse-width limit.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Strong-field induced fragmentation and isomerization of toluene probed by ultrafast femtosecond electron diffraction and mass spectrometry

We investigate the fragmentation and isomerization of toluene molecules induced by strong-field ionization with a femtosecond near-infrared laser pulse. Momentum-resolved coincidence time-of-flight ion mass spectrometry is used to determine the relative yield of different ionic products and fragmentation channels as a function of laser intensity. Ultrafast electron diffraction is used to capture the structure of the ions formed on a picosecond time scale by comparing the diffraction signal with theoretical predictions. Through the combination of the two measurements and theory, we are able to determine the main fragmentation channels and to distinguish between ions with identical mass but different structures. In addition, our diffraction measurements show that the independent atom model, which is widely used to analyze electron diffraction patterns, is not a good approximation for diffraction from ions. Here, we show that the diffraction data is in very good agreement with ab initio scattering calculations.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Crystal Structure of Liguzinediol, 2,5-Dimethylol-3,6-dimethylpyrazine

The 2,5-dimethylol-3,6-dimethylpyrazine, C{sub 8}H{sub 12}N{sub 2}O{sub 2}, liguzinediol, has been recently discovered as a potential agent for the treatment of heart failure with low safety risk. The crystal structure of liguzinediol, which has been determined by single-crystal X-ray diffraction analysis, is reported for the first time. The liguzinediol crystal may be obtained from 50% ethanol or ethyl acetate. The compound crystallizes in the monoclinic system with the sp. gr. P2{sub 1}/n and the unit cell parameters a = 4.0560(8) Å, b = 12.280(3) Å, c = 8.5370(17) Å, β = 96.93(3)°, Z = 2. The molecule forms S{sub 2}-symmetric conformation in the crystal. The hydroxyl H atom forms short intermolecular contacts with the neighbouring pyrazine N atom, which forms the weak hydrogen bonds in the crystal.

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

Simultaneous observation of nuclear and electronic dynamics by ultrafast electron diffraction

Simultaneous observation of nuclear and electronic motion is crucial for a complete understanding of molecular dynamics in excited electronic states. It is challenging for a single experiment to independently follow both electronic and nuclear dynamics at the same time. In this paper we show that ultrafast electron diffraction can be used to simultaneously record both electronic and nuclear dynamics in isolated pyridine molecules, naturally disentangling the two components. Electronic state changes (S 1 →S 0 internal conversion) were reflected by a strong transient signal in small-angle inelastic scattering, and nuclear structural changes (ring puckering) were monitored by large-angle elastic diffraction. Supported by ab initio nonadiabatic molecular dynamics and diffraction simulations, our experiment provides a clear view of the interplay between electronic and nuclear dynamics of the photoexcited pyridine molecule.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Experimental observation of open structures in elemental magnesium at terapascal pressures

Investigating how solid matter behaves at enormous pressures, such as those found in the deep interiors of giant planets, is a great experimental challenge. Over the past decade, computational predictions have revealed that compression to terapascal pressures may bring about counter-intuitive changes in the structure and bonding of solids as quantum mechanical forces grow in influence. Although this behavior has been observed at modest pressures in the highly compressible light alkali metals, it has not been established whether it is commonplace among high-pressure solids more broadly. We used shaped laser pulses at the National Ignition Facility to compress elemental Mg up to 1.3 TPa, which is approximately four times the pressure at the Earth’s core. By directly probing the crystal structure using nanosecond-duration X-ray diffraction, we found that Mg changes its crystal structure several times with non-close-packed phases emerging at the highest pressures. Our results demonstrate that phase transformations of extremely condensed matter, previously only accessible through theoretical calculations, can now be experimentally explored.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Phase fluctuations and the absence of topological defects in a photo-excited charge-ordered nickelate

The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La1.75Sr0.25NiO4 to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1986

Photoelectrochemical fabrication of spectroscopic diffraction gratings

Photoelectrochemical etching was demonstrated as a means of fabricating a variety of periodic structures in semiconductors. The semiconductor is used as an electrode in an electrochemical cell, and is in contact with a liquid electrolyte. When the crystal is held at a positive voltage and illuminated, etching occurs in only the illuminated regions to a depth proportional to the illumination intensity and exposure time. In Phase 1, it was determined that diffraction gratings could be produced in gallium arsenide crystals by this method, using either a scanned focused laser beam or by uniform illumination of a ruling mask defined in metal or photoresist on the crystal surface. The latter approach was determined to produce V-grooves if the mask is oriented along certain crystallographic directions. These V-grooves were produced with an exceedingly smooth crystal morphology due to the highly controllable nature of the process and the mild electrolytes involved. The results form the basis for photoelectrochemical fabrication of deep, low pitch Eschelle gratings for use in high orders in NASA spectrographic instrumentation such as the Space Telescope Imaging Spectrograph.

Rauh, R. David↗
DOE OSTI2013

Novel yellowish-green emitting luminescence in Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16}:Eu{sup 2+} phosphor

Graphical abstract: The phosphor has two separated emission centers with the dependent emission intensity on Eu{sup 2+} doping. There is a red-shift in the emission due to energy transfer with increasing the Eu{sup 2+}-doping. - Highlights: • Green-origin-emitting phosphors of Eu{sup 2+}-doped Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16} were firstly prepared by chemical sol–gel method. • The tunable luminescence color was realized by the changing Eu{sup 2+}-doping in Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16}. • Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16}:Eu{sup 2+} displays two typical luminescence centers with the emission depending on Eu{sup 2+} doping. • Eu{sup 2+}-doped Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16} phosphor has an excellent thermal stability on the temperature quenching. - Abstract: Color tunable green-origin-emitting phosphor of Eu{sup 2+}-doped phosphate-silicate Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16} was prepared by chemical sol–gel method. The X-ray powder diffraction, the photoluminescence excitation and emission spectra, time resolved spectra, and thermal stability were measured. The excitation spectra can well match with the emission light of near UV-LED chips (360–400 nm). The tunable luminescence was realized by changing Eu{sup 2+}-doping concentration. Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16}:Eu{sup 2+} displays two typical luminescence centers, which were suggested to originate from two Ca{sup 2+} sites in the host. With increasing Eu{sup 2+} doping concentrations, the green emission band shifts to long wavelength. Energy transfer between the two different Eu{sup 2+} ions is discussed by analyzing the photoluminescence excitation and emission spectra, concentration-dependent luminescence intensity, and lifetimes. The dependence of the luminescence intensity of Ca{sub 7}Si{sub 2}P{sub 2}O{sub 16}:Eu{sup 2+} on temperatures was measured. The activation energy (ΔE) for thermal quenching was reported.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Development of a versatile electrochemical cell for in situ grazing-incidence X-ray diffraction during non-aqueous electrochemical nitrogen reduction

In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N 2 reduction (Li-N 2 R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N 2 R, the formation of Li metal, LiOH and Li 2 O as well as a peak consistent with the α-phase of Li 3 N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Biocrystallization in Bacterial and Fungal Cells and Spores

A series of X-ray diffraction experiments were performed for the first time to study stress-induced biocrystallization (structural response to stress) in the bacteria E. coli, the spore-forming bacteria Bacillus cereus, and in cells and spores of the mycelial fungus Umbelopsis ramanniana. High-intensity areas with spacings of 90 and 44 Å are indicative of a periodically ordered arrangement (most likely nanocrystalline) of the bacterial nucleoid. For the starved bacteria Bacillus cereus, a peak at a spacing of 45 Å is also assigned to nanocrystalline complexes of DNA with the Dps protein. The spores of the fungus Umbelopsis ramanniana VKM F-582, as well as the spores of Bacillus cereus, form ordered arrays of DNA molecules with DNA-condensing acid-soluble proteins SASPs. Starved dehydrated mycelial cells of the fungus Umbelopsis ramanniana form ordered structures with spacings from 27 to 55 Å. A series of peaks reflect the formation of a number of ordered protein arrays, apparently with DNA, with continuously varying characteristic interplanar spacings.

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

Operando X-ray Diffraction Studies of the Mg-Ion Migration Mechanisms in Spinel Cathodes for Rechargeable Mg-Ion Batteries

A promising high-voltage spinel oxide cathode material MgCrMnO 4 with 18% Mg/Mn inversion was synthesized successfully. A new custom operando battery device was designed to study the cation migration mechanisms of the MgCrMnO 4 cathode using 0.1 M Mg(TPFA) 2 electrolyte dissolved in triglyme and activated carbon as the anode. For the first time in multivalent batteries, high-quality operando diffraction data enabled the accurate quantification of cation contents in the host structure. Besides the exceptional reversibility of 12% Mg 2+ insertion in Mg 1- x CrMnO 4 ( x ≤ 1), a partially reversible insertion of excess Mg 2+ during overdischarging was also observed. Moreover, the insertion/extraction reaction was experimentally shown to be accompanied by a series of cation redistributions in the spinel framework, which were further supported by density functional theory calculations. Furthermore, the inverted Mn is believed to be directly involved in the cation migrations, which would cause voltage hysteresis and irreversible structural evolution after overdischarging. Tuning the Mg/Mn inversion rate could provide a direct path to further optimize spinel oxide cathodes for Mg-ion batteries, and more generally, the operando techniques developed in this work should play a key role in understanding the complex mechanisms involved in multivalent ion insertion systems.

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

When x-rays alter the course of your experiments

The continuing increase in the brilliance of synchrotron radiation beamlines allows for many new and exciting experiments that were impossible before the present generation of synchrotron radiation sources came on line. However, the exposure to such intense beams also tests the limits of what samples can endure. Whilst the effects of radiation induced damage in a static experiment often can easily be recognized by changes in the diffraction or spectroscopy curves, the influence of radiation on chemical or physical processes, where one expects curves to change, is less often recognized and can be misinterpreted as a 'real' result instead of as a 'radiation influenced result'. This is especially a concern in time-resolved materials science experiments using techniques as powder diffraction, small angle scattering and x-ray absorption spectroscopy. In this work, the effects of radiation (5–50 keV) on some time-resolved processes in different types of materials and in different physical states are discussed. We show that such effects are not limited to soft matter and biology but rather can be found across the whole spectrum of materials research, over a large range of radiation doses and is not limited to very high brilliance beamlines.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗