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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Determination of the charge radii of several light nuclei from precision, high-energy electron elastic scattering

Analysis of high-energy electron scattering has been used to determine the charge radii of nuclei for several decades. Recent analysis of the Lamb shift in muonic hydrogen found an r.m.s. radius significantly different than the electron scattering result. To understand this puzzle we have analyzed the "LEDEX" data for the (e, e'p) reaction. This experiment includes measurements on several light nuclei, hydrogen, deuterium, lithium, boron, and carbon. To test our ability to measure absolute cross sections, as well as our ability to extract the charge radius, we tested our technique against the extremely well-measured carbon case and found excellent agreement using the Fourier-Bessel parametrization. We then extended the procedure to boron and lithium, which show nice agreement with the latest theoretical calculations. For hydrogen, we see clearly the limits of this technique and therefore, the charge radius is determined from the traditional extrapolation to q 2 = 0. We will show that there is a model dependence in extracting the charge radius of hydrogen and its unambiguous determination is very difficult with available electron-scattering measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Time-resolved electron spectroscopy for chemical analysis of photodissociation: Photoelectron spectra of Fe(CO) 5 , Fe(CO) 4 , and Fe(CO) 3

The prototypical photoinduced dissociation of Fe(CO) 5 in the gas phase is used to test time-resolved x-ray photoelectron spectroscopy for studying photochemical reactions. Upon one-photon excitation at 266 nm, Fe(CO) 5 successively dissociates to Fe(CO) 4 and Fe(CO) 3 along a pathway where both fragments retain the singlet multiplicity of Fe(CO) 5 . The x-ray free-electron laser FLASH is used to probe the reaction intermediates Fe(CO) 4 and Fe(CO) 3 with time-resolved valence and core-level photoelectron spectroscopy, and experimental results are interpreted with ab initio quantum chemical calculations. Changes in the valence photoelectron spectra are shown to reflect changes in the valence-orbital interactions upon Fe–CO dissociation, thereby validating fundamental theoretical concepts in Fe–CO bonding. Chemical shifts of CO 3σ inner-valence and Fe 3p core-level binding energies are shown to correlate with changes in the coordination number of the Fe center. We interpret this with coordination-dependent charge localization and core-hole screening based on calculated changes in electron densities upon core-hole creation in the final ionic states. This extends the established capabilities of steady-state electron spectroscopy for chemical analysis to time-resolved investigations. Lastly, it could also serve as a benchmark for how charge and spin density changes in molecular dissociation and excited-state dynamics are expressed in valence and core-level photoelectron spectroscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Direct air capture of CO 2 – topological analysis of the experimental electron density (QTAIM) of the highly insoluble carbonate salt of a 2,6-pyridine-bis(iminoguanidine), (PyBIGH 2 )(CO 3 )(H 2 O) 4

Chemical bonding and all intermolecular interactions in the highly insoluble carbonate salt of a 2,6-pyridine-bis(iminoguanidine), (PyBIGH 2 )(CO 3 )(H 2 O) 4 , recently employed in the direct air capture of CO 2 via crystallization, have been analyzed within the framework of the quantum theory of atoms in molecules (QTAIM) based on the experimental electron density derived from X-ray diffraction data obtained at 20 K. Accurate hydrogen positions were included based on an analogous neutron diffraction study at 100 K. Topological features of the covalent bonds demonstrate the presence of multiple bonds of various orders within the PyBIGH 2 2+ cation. Strong hydrogen bonds define ribbons comprising carbonate anions and water molecules. These ribbons are linked to stacks of essentially planar dications via hydrogen bonds from the guanidinium moieties and an additional one to the pyridine nitrogen. The linking hydrogen bonds are approximately perpendicular to the anion–water ribbons. The observation of these putative interactions provided motivation to characterize them by topological analysis of the total electron density. Thus, all hydrogen bonds have been characterized by the properties of their (3,−1) bond critical points. Weaker interactions between the PyBIGH 2 2+ cations have similarly been characterized. Integrated atomic charges are also reported. A small amount of cocrystallized hydroxide ion (∼2%) was also detected in both the X-ray and neutron data, and included in the multipole model for the electron-density refinement. The small amount of additional H + required for charge balance was not detected in either the X-ray or the neutron data. The results are discussed in the context of the unusually low aqueous solubility of (PyBIGH 2 )(CO 3 )(H 2 O) 4 and its ability to sequester atmospheric CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Evolution of Tantalum Content During Vacuum Induction Melting and Electroslag Remelting of a Novel Martensitic Steel

The need for materials with superior thermal and mechanical properties while mitigating cost increases interest in new complex alloy compositions which brings challenges to manufacturing processes. In this investigation, vacuum induction melting (VIM) and electroslag remelting (ESR) of a novel tantalum (Ta)-containing martensitic steel was performed using standard industry practices at a laboratory scale. A 25 pct loss of Ta was measured from the VIM electrode to the ESR ingot using X-ray fluorescence. Several tools were used for broad characterization of the ingots, including LECO for chemistry analysis, scanning electron microscopy, and electron probe microanalysis for observation of the precipitate and inclusion phases post-VIM and post-ESR as well as computational modeling of the ESR process for the calculation of macrosegregation and inclusion travel. It was found that a significant amount of Ta{sub 2}O{sub 5} inclusions formed during VIM and were transferred to the slag during ESR. While ESR was particularly successful at decreasing the number density of inclusions by 95 pct, additional efforts are needed with regard to vacuum leak rate and purity of stock material when melting novel advanced steels.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Isomorphism and solid solutions among Ag- and Au-selenides

Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag{sub 2−x}Au{sub x}Se with a step of x=0.25 (0≤x≤2) to 1050 °C and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag{sub 2}Se – Ag{sub 1.94}Au{sub 0.06}Se, fischesserite Ag{sub 3}AuSe{sub 2} - Ag{sub 3.2}Au{sub 0.8}Se{sub 2} and gold selenide AuSe - Au{sub 0.94}Ag{sub 0.06}Se. Solid solutions and AgAuSe phases were added to the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe. - Highlights: • Au-Ag selenides were synthesized. • Limited Ag-Au isomorphism in the selenides is affected by structural features. • Some new phases were introduced to the phase diagram Ag-Au-Se.

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

Fabrication and physicochemical characterization of graphene oxide derived from thermally expanded graphite

Graphene oxide was obtained from expanded graphite according to the modified Hummers method. The reaction time was significantly reduced (from 24 to 8 h) by applying the expanded graphite in the oxidation process. The interlayer distance in obtained samples was equal to 0.70–0.74 nm. Structural features of the material were studied by the powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, XPS spectroscopy, and NMR spectroscopy.

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

Leveraging Electron Transfer Dissociation for Site Selective Radical Generation: Applications for Peptide Epimer Analysis

Traditional electron-transfer dissociation (ETD) experiments operate through a complex combination of hydrogen abundant and hydrogen deficient fragmentation pathways, yielding c and z ions, side-chain losses, and disulfide bond scission. Herein, a novel dissociation pathway is reported, yielding homolytic cleavage of carbon–iodine bonds via electronic excitation. This observation is very similar to photodissociation experiments where homolytic cleavage of carbon–iodine bonds has been utilized previously, but ETD activation can be performed without addition of a laser to the mass spectrometer. Both loss of iodine and loss of hydrogen iodide are observed, with the abundance of the latter product being greatly enhanced for some peptides after additional collisional activation. These observations suggest a novel ETD fragmentation pathway involving temporary storage of the electron in a charge-reduced arginine side chain. Subsequent collisional activation of the peptide radical produced by loss of HI yields spectra dominated by radical-directed dissociation, which can be usefully employed for identification of peptide isomers, including epimers. .

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

Mechanical Behavior of Commercially Pure Titanium Weldments at Lower Temperatures

Commercially pure titanium is used for low-temperature applications due to good toughness attributed to single-phase microstructure (α). Electron beam welding (EBW) and gas tungsten arc welding (GTAW) processes have been used for welding two grades of commercially pure titanium (Grade 2 and Grade 4). Martensitic microstructure is found to be finer in the case of EBW joint as compared to GTAW joint due to faster rate of cooling in the former process. Weldments have been characterized to study the mechanical behavior at ambient (298 K) and cryogenic temperatures (20 and 77 K). Strength of weldments increases with the decrease in temperature, which is found to be more prominent in case of Grade 4 titanium as compared to Grade 2. Weld efficiency of Grade 4 is found to be higher at all the temperatures (ambient, 77 and 20 K). However, ultimate tensile strength/yield strength ratio is higher for Grade 2 as compared to Grade 4. % Elongation is found to increase/retained at cryogenic temperatures for Grade 2, and it is found to decrease for Grade 4. Electron backscattered diffraction analysis and transmission electron microscopy of deformed samples confirmed the presence of extensive twinning in Grade 2 and the presence of finer martensitic structure in Grade 4. Fractography analysis of tested specimens revealed the presence of cleavage facets in Grade 4 and dimples in specimens of Grade 2. Higher strength in Grade 4 is attributed to higher oxygen restricting the twin-assisted slip, which is otherwise prominent in Grade 2 titanium.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Analysis of multi-electron, multi-step homogeneous catalysis by rotating disc electrode voltammetry: theory, application, and obstacles

Rotating disc electrode (RDE) voltammetry has been widely adopted for the study of heterogenized molecular electrocatalysts for multi-step fuel-forming reactions but this tool has never been comprehensively applied to their homogeneous analogues. Here, the utility and limitations of RDE techniques for mechanistic and kinetic analysis of homogeneous molecular catalysts that mediate multi-electron, multi-substrate redox transformations are explored. Using the ECEC' reaction mechanism as a case study, two theoretical models are derived based on the Nernst diffusion layer model and the Hale transformation. Current–potential curves generated by these computational strategies are compared under a variety of limiting conditions to identify conditions under which the more minimalist Nernst Diffusion Layer approach can be applied. Based on this theoretical treatment, strategies for extracting kinetic information from the plateau current and the foot of the catalytic wave are derived. RDEV is applied to a cobaloxime hydrogen evolution reaction (HER) catalyst under non-aqueous conditions in order to experimentally validate this theoretical framework and explore the feasibility of RDE as a tool for studying homogeneous catalysts. Importantly, analysis of the foot-of-the-wave via this theoretical framework provides rate constants for elementary reaction steps that agree with those extracted from stationary voltammetric methods, supporting the application of RDE to study homogeneous fuel-forming catalysts. Lastly, obstacles encountered during the kinetic analysis of cobaloxime, along with the voltammetric signatures used to diagnose this reactivity, are discussed with the goal of guiding groups working to improve RDE set-ups and help researchers avoid misinterpretation of RDE data.

08 HYDROGEN↗
DOE OSTI2016

Structural and morphological characterization of Mg{sub 0.8}Al{sub 0.2}(OH){sub 2}Cl{sub 0.2} hydrotalcite produced by mechanochemistry method

Chlorine intercalated Mg–Al layered double hydroxides (Mg–Al–Cl–LDH) with a chemical formula Mg{sub 0.8}Al{sub 0.2}(OH){sub 2}Cl{sub 0.2} were successfully produced by the one-step mechanochemistry method and subsequent water washing followed by drying in oven for 1 h at 80 °C. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FT–IR), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), elemental mapping analysis, transmission electron microscopy (TEM), X-ray fluorescence (XRF), and the differential thermogravimetric analysis (DTGA). Results revealed that the structural characteristics of Mg–Al–Cl–LDH were affected strongly by milling time. At the beginning of milling (up to 1 h), Hydrotalcite (HT) and Brucite were the dominant phases, while the progressive mechanical activation was completed as milling time increased, which resulted in the formation of nanostructured Mg–Al–Cl–LDH. Based on XRD and FTIR data, Mg{sub 0.8}Al{sub 0.2}(OH){sub 2}Cl{sub 0.2} with high purity was obtained at 5 h milling. The interlayer spacing of LDH is also strongly influenced by milling time so that it escalated from 7.737±0.001 to 8.005±0.002 (1–15 h) and then decreased to 7.937±0.001 for 20 h milled sample. Electron microscopic observation displayed that the final product had hexagonal platelet structure with lateral dimension of 20–100 nm. Therefore, the synthesis of Mg{sub 0.8}Al{sub 0.2}(OH){sub 2}Cl{sub 0.2} via mechanochemistry owing to simplicity and versatility can be a promising candidate for use in catalyst carriers, drug delivery, and gene delivery. - Graphical Abstract: TEM image of milled sample (Mg–Al–Cl–LDH). - Highlights: • Chlorine intercalated LDH was synthesized by a facile solid-state process. • Structural features of products were influenced strongly by the milling time. • XRD and FTIR spectra suggested predominant Mg–Al–Cl–LDH after 5 h milling. • Products showed hexagonal platelet structure with lateral dimension of 20–100 nm.

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

Stimulated Emission and Optical Properties of Solid Solutions of Cu(In,Ga)Se{sub 2} Direct Band Gap Semiconductors

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se{sub 2} thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of ~20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se{sub 2} thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of ~20 kW/cm{sup 2}. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se{sub 2} thin films.

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

Texture Evolution in an Al-Cu-Mg Alloy During Hot Rolling

The texture evolution in the intermediate (the 1/4 thickness) layer of hot-rolled Al-Cu-Mg alloy sheets was investigated by the x-ray diffraction technique, electron backscattered diffraction analysis and transmission electron microscopy observation. The results showed that a texture transition from the shear texture {001}<110> to the β-fiber textures occurred as the rolling temperature increased to 420 °C. The shear strain caused by friction resulted in this strong shear texture formation at the low rolling temperature. As the rolling temperature increased, the plane strain substituting the shear strain dominated in the intermediate layer, giving rise to a significant increase in the β-fiber textures. Increasing the rolling temperature was found to preferentially activate the non-octahedral {112}<110> slip system, thereby benefiting the development of strong Brass. At the low rolling reduction of 74%, the textures with low intensity tended to converge on the α-fiber, containing Goss, Brass, P and L components. As the rolling reduction increased to 90%, the textures were strengthened and gradually flew toward the β-fiber, containing Brass, Copper and S components. The S and Copper bands were found to be the preferential sites for the development of recrystallizing Cube grains during hot rolling.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Grain subdivision and structural modifications by high-energy heavy ions in UO 2 with different initial grain size

Irradiation with 84 MeV Xe ions at peak fluence above 7 × 10 17 ions/cm 2 has been carried out on two UO 2 samples with different initial grain sizes at 300 °C and 500 °C. Characterization of both grain structure and bubble morphology has been performed using transmission electron microscopy, image analysis and precession electron diffraction. The bubble size in the large-grained sample was smaller than that in the standard-grain sample, confirming fission gas precipitation resistance in the former. The ion irradiation in the high electronic energy deposition range has caused formation of a large density of dislocations which resulted in grain polygonization for the sample with standard grain size, which was observed in multiple lamellas extracted next to each other at peak dose. The sample with large grains showed inconsistent behavior. In one case, dislocation pile-up occurred, but no sub-grain formation was observed. An adjacent location showed sub-grain formation, even if to less extent compared to the standard grain-size sample. Furthermore, these findings suggest a limited polygonization resistance in large-grained UO 2 compared to standard-grain UO 2 . Recrystallization of both sample surfaces was present, leaving unclear if this is a surface effect or a consequence of the highest energy deposition rate in this area.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Synthesis of GaN:ZnO solid solution by solution combustion method and characterization for photocatalytic application

GaN-ZnO solid solution has emerged as a successful and reproducible photocatalyst for overall water splitting by one-step photoexcitation, with a bandgap in visible region. When the solid solution is formed, some of the Zn and O ions are replaced by Ga and N ions respectively and there is a narrowing of bandgap which is hypothesized as due to Zn3d-N2p repulsion. The traditional method of synthesis of GaN-ZnO solid solution is by nitridation of the starting oxides under constant ammonia flow. Here we report a solution combustion technique for the synthesis of the solid solution at a temperature about 500 ° C in a muffle furnace with metal nitrates as precursors and urea as the fuel. The as prepared samples showed change in color with the increased concentration of ZnO in the solution. The structural, microstructural, morphological and optical properties of the samples were realized by Powder X ray diffraction, Scanning electron microscopy, Energy dispersive X ray analysis, Transmission electron microscopy and Photoluminescence. Finally the hydrogen production efficiency of the GaN-ZnO nanopowders by water splitting was found, using methanol as a scavenger. The apparent quantum yield (AQY) of 0.048% is obtained for GaN-ZnO solid solution.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Orbital dependent complications for close vs well-separated electrons in diradicals

We investigate two limits in open-shell diradical systems: O3, in which the interesting orbitals are in close proximity to one another, and (C21H13)2, where there is a significant spatial separation between the two orbitals. In accord with earlier calculations, we find that standard density-functional approximations do not predict the open-shell character for the former case but uniformly predict the open-shell character for the latter case. We trace the qualitatively incorrect behavior in O3 predicted by these standard density functional approximations to self-interaction error and use the Fermi–Löwdin-orbital-self-interaction-corrected formalism to determine accurate triplet, closed-shell singlet, and open-shell broken-spin-symmetry electronic configurations. Analysis of the resulting many-electron overlap matrices allows us to unambiguously show that the broken-spin-symmetry configurations do not participate in the representation of the Ms = 0 triplet states and allows us to reliably extract the singlet–triplet splitting in O3 by analyzing the energy as a function of Fermi-orbital-descriptor permutations. The results of these analyses predict the percentage of open-shell character in O3, which agrees well with conventional wavefunction-based methods. While these techniques are expected to be required in cases near the Coulson–Fischer point, we find that they will be less necessary in diradical systems with well-separated electrons, such as (C21H13)2. Results based on energies from self-interaction-corrected generalized gradient, local density, and Hartree–Fock approximations and experimental results are in generally good agreement for O3. These results help form the basis for deriving extended Heisenberg-like Hamiltonians that are needed for descriptions of molecular magnets when there are competing low-energy electronic configurations.

Chemistry↗
DOE OSTI2017

The electronics, trigger and data acquisition system for the liquid argon time projection chamber of the DarkSide-50 search for dark matter

The DarkSide-50 experiment at the Laboratori Nazionali del Gran Sasso is a search for dark matter using a dual phase time projection chamber with 50 kg of low radioactivity argon as target. Light signals from interactions in the argon are detected by a system of 38 photo-multiplier tubes (PMTs), 19 above and 19 below the TPC volume inside the argon cryostat. We describe the electronics which processes the signals from the photo-multipliers, the trigger system which identifies events of interest, and the data-acquisition system which records the data for further analysis. The electronics include resistive voltage dividers on the PMTs, custom pre-amplifiers mounted directly on the PMT voltage dividers in the liquid argon, and custom amplifier/discriminators (at room temperature). After amplification, the PMT signals are digitized in CAEN waveform digitizers, and CAEN logic modules are used to construct the trigger, the data acquisition system for the TPC is based on the Fermilab "artdaq" software. The system has been in operation since early 2014.

Agnes, P.↗
DOE OSTI2020

Search for Electron Neutrino Anomalies with the MicroBooNE Detector

The Micro Booster Neutrino Experiment (MicroBooNE) is a Liquid Argon Time Projection Chamber (LArTPC) located in the Booster Neutrino Beam at Fermi National Accelerator Laboratory. The experiment was devised to investigate a series of observed anomalies concerning short-baseline neutrino oscillation physics. The LArTPC technology enables the experiment to study neutrino-argon scattering with unprecedented detail.This thesis presents a cosmic-ray characterisation and rate measurement. The understanding of cosmic activity in the detector - MicroBooNE's dominant background - is then used to develop cosmic rejection tools. A flavour-agnostic neutrino selection is constructed, which forms the cornerstone of this and further analyses. Inclusive muon and electron charged-current neutrino interaction selections with unprecedented purity and efficiency are presented.The first fully-automated characterisation of electron neutrinos in a muon neutrino beam with the LArTPC detector technology is performed. The Booster Neutrino Beam has an energy peaking around 1GeV and an intrinsic electron content of approximately 0.5%. The analysis investigates electrons produced in charged-current electron neutrino interactions. The kinematics of the electrons are measured along with comparisons to simulation. Most of the systematic uncertainties are constrained using a data-driven sample of charged-current muon neutrino events. The measurement of electron neutrinos originating from the Booster Neutrino Beam is a crucial component towards understanding the nature of the observed excess of low-energy electromagnetic-like events at its predecessor, MiniBooNE.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Charged-Current Electron Neutrino Measurement with the MicroBooNE Detector

MicroBooNE is the first phase of Fermilab’s Short Baseline Neutrino (SBN) Liquid Argon Time Projection Chamber (LArTPC) programme.This proceeding outlays the first characterisation of electron neutrinos in a muon neutrino beam with the LArTPC detector technology. The Booster Neutrino Beam has an energy peaking around 1GeV and an electron content of approximately 0.5%. The analysis investigates electrons produced in charged-current electron neutrino interactions. The kinematics of the electrons are measured along with comparisons to simulation. Most of the systematic uncertainties are constrained using a data-driven sample of charged-current muon neutrino events. The measurement of electron neutrinos originating from the Booster Neutrino Beam is a crucial component to understand the nature of the observed excess of low energy electromagnetic-like events at MiniBooNE.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗