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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Kinetic equilibrium reconstruction and the impact on stability analysis of KSTAR plasmas

High fidelity kinetic plasma equilibrium reconstructions are an essential requirement for accurate stability and disruption prediction analyses to support continuous operation of high beta tokamak plasmas. The present kinetic equilibrium reconstructions of plasmas in the KSTAR device include plasma density and temperature profiles from Thomson scattering and ion temperature from charge exchange spectroscopy diagnostics, and allowance for fast particle pressure. In addition, up to 25 channels of motional Stark effect diagnostic data are used to constrain the magnetic field pitch angle profile in the plasma to produce a reliable computation of the safety factor, q, profile. In this work, H-mode plasmas exhibit clear pedestal characteristics in the reconstructed pressure profile compared to internal transport barrier or L-mode plasmas. The plasma configuration and vertical position of inner strike points are validated by CCD and infrared camera images. Ideal and resistive magnetohydrodynamic (MHD) stability analyses using the DCON and resistive DCON codes utilize these kinetic equilibrium reconstructions to compare to experimental plasma stability. Equilibria with sufficiently low convergence error can provide reliable computation of ideal and resistive MHD stability analysis.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Monitoring the corrosion resistance of cold-spray coatings with membrane-based sensors

In this presentation, the MBES shows the ability to detect the change in exposed environment even with cold-spray coatings. Corrosion rates from the cold-spray coating were comparable to a 316 stainless steel sample. Defects in the coating did not impact sensor performance in terms of corrosion rate or water content detection. Energy dispersive X-ray spectroscopy was used to document ion migration into the membrane.

Rendon, Arnaldo↗
DOE OSTI2022

Characterizing Radiation-Induced Chromium Redox Chemistry

The redox behavior of Cr(III) and Cr(VI) in nuclear environments were studied by analyzing aqueous irradiated chromium ions using UV-Visible spectroscopy. The formation of different chromium oxidation states can occur through gamma radiolysis of chromium solutions. Characterization of radiation-induced chromium is not well understood, and yet important as chromium can make its way into the primary coolant of reactors because of the corrosion of stainless steel reactor components. Furthermore, Cr(VI) is toxic and not suitable for environmental release, therefore Cr speciation is important. Fricke dosimetry was performed to collect doses rates, specific extinction coefficients were obtained from various analytical methods for the two oxidation states of chromium. Chromium samples--conditioned at various pH's and concentration to understand the effects--were then irradiated using a Coblat-60 gamma irradiator. Three optical spectroscopy analytical methods were used , including direct oxidation state measurements and complexation by either EDTA or DPC. Complexation by EDTA was found to not be a reliable method. Radiolytic oxidation of Cr(III) to Cr(VI), and reduction of Cr(VI) to Cr(III) were clearly seen, except for Cr(III) samples were a pH less than or equal to 2, where no change occurred.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Exploration of Sn 70 Li 30 alloy as possible material for flowing liquid metal plasma facing components

As an advanced alternative to solid materials, Liquid Metals (LM) may offer more resilient and feasible Plasma Facing Components (PFCs). Particularly, regarding the unavoidable material erosion/degradation produced by particle/heat fluxes in future fusion devices where much longer duty cycles are expected. Furthermore, configurations that propose a flowing LM surface can add the advantage of a continuously fresh and clean layer facing the plasma. Although lithium is the most widely tested option, tin-lithium (SnLi) alloys have been proposed to attempt to combine the positive characteristics of both pure elements and ameliorate the specific issues of lithium. In this work, the potential use of Sn70Li30 alloy in such flowing concepts has been explored by addressing several preliminary and mandatory aspects for its utilization. Key issues such as wettability and compatibility of the alloy with relevant substrates have been studied in a multidisciplinary approach. The data obtained from deposited liquid tin-lithium droplets indicates approximate wetting temperatures of 360 °C, 390 °C and 405 °C for the fresh alloy on 316 stainless steel, molybdenum, and tungsten, respectively. However, the alloy contamination appeared to strongly affect the wetting characteristics of materials, increasing their wetting temperature by ~130 °C in the worst observed cases. Interestingly, in some instances, the instability of the liquid alloy surface was observed in the form of sudden gaseous ejection. The deposited droplets were posteriorly characterized in terms of absolute composition and depth profile by Inductively Coupled PlasmaOptical Emission Spectroscopy (ICP-OES) and Secondary Ion Mass Spectrometry (SIMS-ToF). Additionally, the nature and composition of the boundaries between the substrates and alloy microparticles was investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and 3D Laser microscopy. The overall results of this post-mortem characterization revealed that first signs of corrosion induced by both alloy elements (lithium-chromium association and iron-tin intermetallic mixing) were present on 316 stainless steel after short exposures (≤3 h) at temperatures lower than 550 °C. Conversely, molybdenum and tungsten showed good compatibility with the alloy in equivalent conditions. The global implications of these results are finally addressed, focusing on the future perspectives and the more viable scenarios for the eventual utilization of these alloys in flowing liquid metal configurations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Charge Movement and Structural Changes in the Gas-Phase Unfolding of Multimeric Protein Complexes Captured by Native Top-Down Mass Spectrometry

The extent to which noncovalent protein complexes retain native structure in the gas phase is highly dependent on experimental conditions. Energetic collisions with background gas can cause structural changes ranging from unfolding to subunit dissociation. Additionally, recent studies have highlighted the role of charge in such structural changes, but the mechanism is not completely understood. In this study, native top down (native TD) mass spectrometry was used to probe gas-phase structural changes of alcohol dehydrogenase (ADH, 4mer) under varying degrees of in-source activation. Changes in covalent backbone fragments produced by electron capture dissociation (ECD) or 193 nm ultraviolet photodissociation (UVPD) were correlated to structural changes of the ADH 4mer. ECD fragments indicated unfolding started at the N-terminus, and the charge states of UVPD fragments enabled monitoring of charge migration to the unfolded regions. Interestingly, UVPD fragments also indicated that the charge at the “unfolding” N-terminus of ADH decreased at high in-source activation energies after the initial increase. We proposed a possible “refolding-after-unfolding” mechanism, as further supported by monitoring hydrogen elimination from radical a-ions produced by UVPD at the N-terminus of ADH. However, “refolding-after-unfolding” with increasing in-source activation was not observed for charge-reduced ADH, which likely adopted compact structures that are resistant to both charge migration and unfolding. Combined, these results support a charge-directed unfolding mechanism for protein complexes. Overall, an experimental framework was outlined for utilizing native TD to generate structure-informative mass spectral signatures for protein complexes that complement other structure characterization techniques, such as ion mobility spectrometry and computational modeling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

X-ray induced electron and ion fragmentation dynamics in IBr

Characterization of the inner-shell decay processes in molecules containing heavy elements is key to understanding x-ray damage of molecules and materials and for medical applications with Auger-electron-emitting radionuclides. The 1s hole states of heavy atoms can be produced by absorption of tunable x rays and the resulting vacancy decays characterized by recording emitted photons, electrons, and ions. The 1s hole states in heavy elements have large x-ray fluorescence yields that transfer the hole to intermediate electron shells that then decay by sequential Auger-electron transitions that increase the ion’s charge state until the final state is reached. In molecules, the charge is spread across the atomic sites, resulting in dissociation to energetic atomic ions. We have used x-ray/ion coincidence spectroscopy to measure charge states and energies of Iq+ and Brq′+ atomic ions following 1s ionization at the I and Br K-edges of IBr. We present the charge states and kinetic energies of the two correlated fragment ions associated with core-excited states produced during the various steps of the cascades. Here, to understand the dynamics leading to the ion data, we develop a computational model that combines Monte-Carlo/Molecular-Dynamics (MC/MD) simulations with a classical over-the-barrier model to track inner-shell cascades and redistribution of electrons in valence orbitals and nuclear motion of fragments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Aligning the Thomson scattering and charge exchange recombination diagnostics using neutral beam emission at DIII-D

This work addresses discrepancies in the alignment of the H-mode pedestal profiles of the electron and ion properties in the DIII-D tokamak as measured by Thomson Scattering (TS) and Charge Exchange Recombination Spectroscopy (CER) diagnostics. While the alignment of these profiles is key for accurate studies of tokamak physics and plasma confinement, misalignments can occur due to inaccuracies, such as in magnetic equilibrium reconstructions required to map measurements in different poloidal and toroidal locations. Both FIDASIM, an established simulation package, and a simplified collisional radiative model are used to simulate neutral beam state densities and neutral beam emission. Simulated neutral beam emissions are calculated based on shifted TS profiles and compared to beam emission measurements from the Main Ion CER system to determine the best shift for aligning TS with CER. This analysis is performed on various DIII-D discharges.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Si-based materials for lithium-ion batteries VIII. 90% surface-modified Si/C-lithiated polyacrylic acid electrode

X-ray photoelectron spectroscopy was used to analyze a 90% Si/C-lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al K α radiation at 1486.6 eV (0.834 01 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey spectrum was collected to ascertain the amount of beam-induced damage, which appears to be minimal. Finally, the spectra indicate the principal core level photoelectron and Auger electron signals with only minor lithium signal and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well contributions related to the binder material.

25 ENERGY STORAGE↗
DOE OSTI2022

The mechanism behind the high radiation tolerance of Fe-Cr alloys

With the great demand for high radiation tolerant materials for advanced nuclear energy technologies, Fe-Cr alloys are at the forefront with long standing validated performance. Yet, the real mechanism behind their high radiation resistance is in question and understanding the effect of varying Cr percentage is a grand challenge limiting further improvements. Here we applied depth resolved atomic scale probe of defects to uncover the real mechanism on how Cr improves radiation resistance and explain the controversial impact of increasing Cr percentage. By combining depth-resolved positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy we investigated the effect of Cr alloying on the formation and evolution of atomic size clusters induced by ion irradiation in Fe. We also used atom probe tomography to investigate the possible presence of Cr clusters or a’ phase with high Cr composition. The study reveals that the well-known resistance to radiation in Fe-Cr alloys arises from the stabilization of vacancy clusters around Cr atoms which act as sinks for radiation-induced defects. Thus, Cr atoms do not provide a direct sink for interstitials; rather defect complexes for that consist of Cr atoms and vacancies in turn act as sinks for irradiation-induced vacancies and interstitials. Most importantly, we find that lower amounts of Cr create smaller, uniformly distributed defect clusters that act as efficient sinks for radiation damage, but larger quantities of Cr form a defect structure that is less homogenous in size and spatial distribution, resulting in less efficient damage recombination. No evidence of phase a’ was found before or after irradiation, which indicates that it does not contribute to the observed radiation tolerance.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of nitrogen on tungsten surfaces investigated with low energy ion scattering

The effect of nitrogen on the surfaces of polycrystalline ITER-grade tungsten and a tungsten single crystal were studied with low energy ion scattering (LEIS) and direct recoil spectroscopy (DRS). LEIS and DRS measurements on both tungsten surfaces were performed in an ultra-high vacuum system as various quantities of N 2 were introduced into the chamber through a variable leak valve. The obtained ion energy spectra reveal that nitrogen was readily adsorbed onto the surface, in turn limiting the amount of hydrogen that could be adsorbed onto the surface. These results not only provide insight into how the presence of nitrogen on tungsten surfaces may play a role in hydrogen adsorption and retention, but also serve to benchmark models being developed to describe the H-N-W system.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Molecular structures of residual solvent in polyacrylonitrile based electrolytes: Implications for conductivity and stability

Lithium-ion batteries increasingly play significant roles in modern technologies; however, increased energy density also raises concerns about electrolyte safety. Traditional electrolytes that use volatile organic solvents face risks of thermal runaways and fires from electrode shorting. In response, polymer-based solid electrolytes have been developed for replacement. Polyacrylonitrile (PAN) is a promising fire-resistant component for electrolyte fabrication, but its limited solubility necessitates using low-volatility solvents, which are notoriously difficult to remove in subsequent drying processes. Here, we use femtosecond two-dimensional infrared spectroscopy to provide an in-depth understanding of how residual solvent from processing affects the molecular structures and dynamics within a polymer electrolyte. To this end, linear and nonlinear infrared spectroscopies are employed to interrogate the molecular interactions in PAN-based electrolytes containing various contents of N,N-dimethylformamide (DMF). We show that the amount of DMF within the PAN electrolyte affects the Li+ structure. Further, the coordination can proceed through the carbonyl group and/or the amide nitrogen to form antiparallel structures with the nitrile groups of PAN through dipole–dipole interactions. The free motion of DMF is drastically inhibited upon interaction with Li+ and PAN, which decreases the ionic conductivity and potentially affects the stability (resistance toward removal and chemical decomposition). These findings have implications for the design and processing of solid polymer electrolytes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Monofluorinated acetal electrolyte for high-performance lithium metal batteries

High degree of fluorination for ether electrolytes has resulted in improved cycling stability of lithium metal batteries due to stable solid electrolyte interphase (SEI) formation and good oxidative stability. However, the sluggish ion transport and environmental concerns of high fluorination degree drive the need to develop less fluorinated structures. Here, we depart from the traditional ether backbone and introduce bis(2-fluoroethoxy)methane (F2DEM), featuring monofluorination of the acetal backbone. High coulombic efficiency and stable long-term cycling in Li||Cu half cells can be achieved with F2DEM even under fast Li metal plating conditions. The performance of F2DEM is further compared with diethoxymethane (DEM) and 2-[2-(2,2-difluoroethoxy)ethoxy]-1,1,1-trifluoroethane (F5DEE). A significantly lower overpotential is observed with F2DEM, which improves energy efficiency and enables its application in high-rate conditions. Comparative studies of F2DEM with DEM and F5DEE in anode-free lithium iron phosphate (LiFePO4) LFP pouch cells and high-loading LFP coin cells further show improved capacity retention of F2DEM electrolyte, demonstrating its practical applicability. More importantly, we also extensively investigate the underlying mechanism for the superior performance of F2DEM through various techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, cryogenic electron microscopy, focused ion beam, electrochemical impedance spectroscopy, and titration gas chromatography. Overall, F2DEM facilitates improved Li deposition morphology with reduced amount of dead Li. This enables F2DEM to show superior performance, especially under higher charging and slower discharging rate conditions.

25 ENERGY STORAGE↗
DOE OSTI2024

Chemical Environment and Structural Variations in High Entropy Oxide Thin Film Probed with Electron Microscopy

For this work, we employ analytical transmission electron microscopy (TEM) to correlate the structural and chemical environment variations within a stacked epitaxial thin film of the high entropy oxide (HEO) Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O (J14), with two layers grown at different substrate temperatures (500 and 200 °C) using pulsed laser deposition (PLD). Electron diffraction and atomically resolved STEM imaging reveal the difference in out-of-plane lattice parameters in the stacked thin film, which is further quantified on a larger scale using four-dimensional STEM (4D-STEM). In the layer deposited at a lower temperature, electron energy loss spectroscopy (EELS) mapping indicates drastic changes in the oxidation states and bonding environment for Co ions, and energy-dispersive X-ray spectroscopy (EDX) mapping detects more significant cation deficiency. Ab initio density functional theory (DFT) calculations validate that vacancies on the cation sublattice of J14 result in significant electronic and structural changes. The experimental and computational analyses indicate that low temperatures during film growth result in cation deficiency, an altered chemical environment, and reduced lattice parameters while maintaining a single phase. Our results demonstrate that the complex correlation of configurational entropy, kinetics, and thermodynamics can be utilized for accessing a range of metastable configurations in HEO materials without altering cation proportions, enabling further engineering of functional properties of HEO materials.

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

Atomic layer deposition of HfO 2 films using carbon-free tetrakis(tetrahydroborato)hafnium and water

Thin hafnium oxide films were prepared by atomic layer deposition using a carbon-free precursor, tetrakis(tetrahydroborato)hafnium [Hf(BH 4 )( 4 )], and H 2 O. Film growth was studied using an in situ quartz crystal microbalance and Fourier transform infrared spectroscopy measurements. Self-limiting growth was observed between 100 and 175 degrees C, but the thermal decomposition of the Hf precursor occurred at higher temperatures. The film properties were investigated using x-ray photoelectron spectroscopy, x-ray reflectivity, x-ray diffraction, ellipsometry, time-of-flight secondary ion mass spectrometry, and x-ray absorption spectroscopy. The as-deposited films were found to consist of an amorphous mixture of HfO 2 and B 2 O 3 , and had a lower density and lower refractive index compared to pure HfO 2 thin films. Finally, annealing the films to >750 degrees C yielded crystalline monoclinic HfO 2 with a density of 9g/cm 3 and a refractive index of 2.10.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Si-based materials for lithium-ion batteries VII. 70% surface-modified Si/C-carbon black/lithiated polyacrylic acid electrode

X-ray photoelectron spectroscopy (XPS) was used to analyze a 70% Si/C-carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al K α radiation at 1486.6 eV (0.834 01 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey spectrum was collected to ascertain the amount of beam-induced damage, which appears to be minimal. Finally, the spectra indicate the principal core level photoelectron and Auger electron signals with only minor copper, nitrogen, calcium, and lithium signals and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well contributions related to the binder material.

25 ENERGY STORAGE↗
DOE OSTI2020

Si-based materials for lithium-ion batteries XI. 70% surface-modified Si/C/perfluorooctene-carbon black/lithiated polyacrylic acid electrode

X-ray photoelectron spectroscopy was used to analyze a 70% Si/C/perfluorooctene-carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping (CAMP) Facility, Argonne National Laboratory. The spectra were obtained using incident monochromatic Al K α radiation at 1486.6 eV (0.83 401 nm). A survey spectrum together with O 1s, C 1s, and Si 2p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor sodium, copper, calcium, and lithium signals and show the expected silicon-carbon, carbon-fluorine, and silicon-fluorine species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure.

25 ENERGY STORAGE↗