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At least 793 records · Page 44

All sources NASA NTRS DOE OSTI

DOE OSTI2025

Water flipping and the oxygen evolution reaction on Fe 2 O 3 nanolayers

Hematite photoanodes are promising for the oxygen evolution reaction, however, their high overpotential (0.5-0.6 V) for water oxidation and limited photocurrent make them economically unviable at present. The work needed to orient dipoles at an electrode surface may be an overlooked contribution to the overpotential, especially regarding dipoles of water, the electron source in the oxygen evolution reaction (OER). Here, we employ second harmonic amplitude and phase measurements to quantify the number of net-aligned Stern layer water molecules and the work associated with water flipping, on hematite, an earth abundant OER semiconductor associated with a high overpotential. At zero applied bias, the pH-dependent potentials for Stern layer water molecule flipping exhibit Nernstian behavior. At positive applied potentials and pH 13, approximately one to two monolayers of water molecules points the oxygen atoms towards the electrode, favorable for the OER. The work associated with water flipping matches the cohesive energy of liquid water (44 kJ mol -1 ) and the OER current density is highest. This current is negligible at pH 5, where the work approaches 100 kJ mol -1 . Our findings suggest a causal relationship between the need for Stern layer water flipping and the OER overpotential, which may lead to developing strategies for decreasing the latter.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Introduction of Chalcogenide Glasses to Additive Manufacturing: Nanoparticle Ink Formulation, Inkjet Printing, and Phase Change Devices Fabrication

Abstract Chalcogenide glasses are one of the most versatile materials that have been widely researched because of their flexible optical, chemical, electronic, and phase change properties. Their application is usually in the form of thin films, which work as active layers in sensors and memory devices. In this work, we investigate the formulation of nanoparticle ink of Ge–Se chalcogenide glasses and its potential applications. The process steps reported in this work describe nanoparticle ink formulation from chalcogenide glasses, its application via inkjet printing and dip-coating methods and sintering to manufacture phase change devices. We report data regarding nanoparticle production by ball milling and ultrasonication along with the essential characteristics of the formed inks, like contact angle and viscosity. The printed chalcogenide glass films were characterized by Raman spectroscopy, X-ray diffraction, energy dispersive spectroscopy and atomic force microscopy. The printed films exhibited similar compositional, structural, electronic and optical properties as the thermally evaporated thin films. The crystallization processes of the printed films are discussed compared to those obtained by vacuum thermal deposition. We demonstrate the formation of printed thin films using nanoparticle inks, low-temperature sintering and proof for the first time, their application in electronic and photonic temperature sensors utilizing their phase change property. This work adds chalcogenide glasses to the list of inkjet printable materials, thus offering an easy way to form arbitrary device structures for optical and electronic applications.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2020

Determinants for proton location and electron coupled proton transfer in hydrogen bonded pentafluorophenol-anion clusters

This work aims to reveal the determinant factors for proton locations and electron coupled proton transfer (ECPT) in biologically relevant hydrogen bonded systems. Pentafluorophenol-anion clusters [C6F5O-•H+•A-]- are chosen to model active sites of biological functions, with the anion A- being systematically varied to ensure the proton affinities (PAs) of the anions well cover the referenced PA of C6F5O- from being appreciably smaller, similar, and to significantly larger. Negative ion photoelectron spectroscopy of these clusters provides spectroscopic evidence showing that proton location in the anionic state is largely following the PA prediction, while ECPT is observed only for the clusters with the anion possessing the electron binding energy (EBE) significantly larger than that of the referenced C6F5O-. Theoretical calculations suggest these clusters are stabilized by forming single strong hydrogen bond between donor and acceptor, and the associated charge and MO analyses fully support the experimental observations. The current holistic cluster model study indicates that PA is the right determinant that can be used to predict the proton location and describe hydrogen bonding structures, while both PA and EBE of anionic groups play important roles in facilitating ECPT process. This work was supported by U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Science, Geosciences, and Biosciences (X.-B.W.), and performed using EMSL, a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by Battelle Memorial Institute for the DOE. Part of this work was supported by the National Natural Science Foundation of China (No-11604046 for JZ; No. 11727810 for ZRS), as well as “Chenguang Program” by Shanghai Education Development Foundation, Shanghai Municipal Education Commission (No. 16CG38) and Natural Science Foundation of Shanghai (No. 16ZR1448100) (JZ).

Zhang, Jian↗

DOE OSTI2022

Concentration-dependent ion correlations impact the electrochemical behavior of calcium battery electrolytes.

Ion interactions strongly determine the solvation environments of multivalent electrolytes even at concentrations below that required for practical battery-based energy storage. This statement is particularly true of electrolytes utilizing ethereal solvents due to their low dielectric constants. These solvents are among the most commonly used for multivalent batteries based on reactive metals (Mg, Ca) due to their reductive stability. Recent developments in multivalent electrolyte design have produced a variety of new salts for Mg2+ and Ca2+ that test the limits of weak coordination strength and oxidative stability. Such electrolytes have great potential for enabling full-cell cycling of batteries based on these working ions. However, the ion interactions in these electrolytes exhibit significant and non-intuitive concentration relationships. In this work, we investigate a promising exemplar, calcium tetrakis(hexafluoroisopropoxy)borate (Ca(BHFIP)(2)), in the ethereal solvents 1,2-dimethoxyethane (DME) and tetrahydrofuran (THF) across a concentration range of several orders of magnitude. Surprisingly, we find that effective salt dissociation is lower at relatively dilute concentrations (e.g. 0.01 M) than at higher concentrations (e.g. 0.2 M). Combined experimental and computational dielectric and X-ray spectroscopic analyses of the changes occurring in the Ca2+ solvation environment across these concentration regimes reveals a progressive transition from well-defined solvent-separated ion pairs to de-correlated free ions. This transition in ion correlation results in improvements in both conductivity and calcium cycling stability with increased salt concentration. Comparison with previous findings involving more strongly associating salts highlights the generality of this phenomenon, leading to important insight into controlling ion interactions in ether-based multivalent battery electrolytes.

Hahn, Nathan T.↗

DOE OSTI2022

Revealing nanomechanical deformation at the interface and degradation in all-thin-film inorganic electrochromic devices

Recently, progress in electrochromic (EC) devices has been made in optimizing electrode and device configurations and performance. However, the ion insertion/de-insertion induced charge transfer (CT) nanomechanical effect has remained unexplored, i.e., repetitive electrode size changes at the nanoscale and stress/strain generated during electrochemical cycling, which is the focus of this work due to its intimate correlation with the elastic and plastic deformation at the interface. Considering the intervalence electrons, excellent electrochemical kinetics, and dramatic color changes, tungsten oxide (WO 3 ) and nickel oxide (NiO) films are configured as the EC cathode and anode materials, respectively, within a full device. Upon extended cycles (>10 000), the void generation and delamination that occurred at the interface account for performance decay. Encouraged by the findings, nanoindentation mechanical tests and electrical kelvin probe force microscopy were employed to investigate the CT induced effects at the interface. There is a dramatic increase of up to 45% in the elastic Young's modulus in colored/charged WO 3 at ~40 mC cm -2 . Here, the correlation between CT and synergistic mechanical effect is interpreted by the Lippman equation. Interestingly, despite the charged state (colored; lithiated) with a relatively flat morphology bringing an ~3.4 times higher electrostatic surface potential, the electrical work function unexpectedly decreases, arising from the dominant effect of the dipole layer potential over the chemical potential. The interatomic cohesive energy and equilibrium distance increase bury the seeds for mechanical deformation in the long run. This work provides fundamental insights into electro-chemo mechanics and interdisciplinary concerted interfacial effects at the nano/atomic level. The dependence of surface potential, stress, work function, and cohesive energy on electrochemical kinetics has been interpreted.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Electrochemistry-induced deposition for controlled formation of metal–organic framework films on insulator and conductor substrates

A number of technological applications of metal–organic frameworks (MOFs) require the formation of their thin films on insulator and/or conductor substrates at selected areas with desired thicknesses. However, fabrication of such MOF films often requires multi-step processes and/or sophisticated instruments. Herein, we discuss electrochemistry-induced MOF deposition, which permits the direct formation of a thin MOF film with controlled thickness at a desired area on various substrates. So far, we have reported the applicability of this deposition method for the formation of zeolitic imidazolate framework-8 (ZIF-8) films. In this method, a ZIF-8 film is formed on an insulator or a conductor substrate upon applying a cathodic potential to a working electrode that is placed above the substrate. Importantly, the film is formed just below the cathodic working electrode, indicating that the position and lateral dimensions (on the mm- to μm-scale) of the film can be controlled by those of the working electrode. In addition, film thickness is controllable in the range of tens to hundreds of nanometers by adjusting potential application conditions at the cathodic working electrode. These results show that the electrochemistry-induced deposition method will provide a simple means for the fabrication of a patterned MOF film on various substrates without additional lithographic processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

WLCG Authorisation from X.509 to Tokens

The WLCG Authorisation Working Group was formed in July 2017 with the objective to understand and meet the needs of a future-looking Authentication and Authorisation Infrastructure (AAI) for WLCG experiments. Much has changed since the early 2000s when X.509 certificates presented the most suitable choice for authorisation within the grid; progress in token based authorisation and identity federation has provided an interesting alternative with notable advantages in usability and compatibility with external (commercial) partners. The need for interoperability in this new model is paramount as infrastructures and research communities become increasingly interdependent. Over the past two years, the working group has made significant steps towards identifying a system to meet the technical needs highlighted by the community during staged requirements gathering activities. Enhancement work has been possible thanks to externally funded projects, allowing existing AAI solutions to be adapted to our needs. A cornerstone of the infrastructure is the reliance on a common token schema in line with evolving standards and best practices, allowing for maximum compatibility and easy cooperation with peer infrastructures and services. We present the work of the group and an analysis of the anticipated changes in authorisation model by moving from X.509 to token based authorisation. A concrete example of token integration in Rucio is presented.

Bockelman, Brian↗

DOE OSTI2026

Automated ICRF heating surrogate modeling via machine learning

This work introduces automated machine learning workflows that address critical bottlenecks in surrogate model development for Ion Cyclotron Range of Frequencies (ICRF) heating applications. The automated framework includes data analysis tools that transform raw datasets into actionable insights in seconds, replacing weeks of manual exploratory effort and ensuring consistent, reproducible dataset characterization. By integrating advanced hyperparameter optimization (HPO) methods including Bayesian optimization via BoTorch and Tree-structured Parzen Estimators (TPE), the framework significantly reduces model development time from weeks to hours, decreasing computational cost and required expertise, while enabling high-accuracy surrogate models. Compared to traditional hyperparameter scanning (HPS) techniques such as methodical, randomized, and grid searches, HPO methods achieve superior convergence and predictive performance, even when compared to already well-tuned reference models. On NSTX High Harmonic Fast Wave (HHFW) heating datasets, both Random Forest Regressor (RFR) and neural network surrogates demonstrate improved accuracy, achieving R 2 values beyond 0.97 and 0.98, respectively. The results show that while HPO gains are modest for robust architectures like RFR, they become essential for more sensitive models such as neural networks, highlighting the trade-offs across optimization strategies. Through automated workflows that eliminate manual hyperparameter tuning and require minimal ML expertise, this work enables widespread adoption of high-fidelity surrogate models across the fusion community for real-time plasma control, uncertainty quantification, rapid experimental scenario development, and integrated system optimization.

Sanchez-Villar, Alvaro [Princeton Plasma Physics L↗

DOE OSTI2020

High-Pressure Apparatus for Monitoring Solid–Liquid Phase Transitions

This work presents a new technique for observing the solid–liquid phase transformations in complex diesel fuel blends and diesel surrogates under high-pressure conditions intended to simulate those occurring in vehicle fuel injectors. A high-pressure apparatus based on a visual identification of freezing and thawing has been designed and built to monitor phase behavior and determine the crystallization temperature of complex fuels to predict wax precipitation. The proposed methodology was validated using pure substances—n-hexadecane (C16H34), cyclohexane (C6H12), and a binary cyclohexane/n-hexadecane mixture—all of which have been well-characterized previously. The crystallization temperatures of these compounds were measured from atmospheric pressure to 400 MPa for temperatures varying from 290 to 363 K and compared to those reported in the literature. The standard error of the estimated temperatures, based on a given pressure, between the experimental data obtained in this work was compared to data in the literature from Domanska et al. This methodology is being extended to investigate the properties of more complex fuel mixtures.

High-Pressure, phase change, diesel, solidificatio↗

DOE OSTI2020

Ab Initio Methods for L-edge X-ray Absorption Spectroscopy

The theoretical prediction of X-ray absorption spectra (XAS) has become common- place in electronic structure theory. The ability to better model and understand L-edge spectra is of great interest in the study of transition metal complexes and a wide variety of solid state materials. However, until recently few rst-principles works have mod- eled L-edge XAS due to the presence of strong spin-orbit coupling in the 2p orbitals which splits the observed peaks into multiple groups of features. Therefore, a proper description of spin-orbit coupling is vital for the successful prediction of L-edge spectra. A number of new approaches that incorporate spin-orbit coupling have recently made advances in the computation of L-edge spectra. In this review, we describe recent work in computational L-edge XAS and how these methods may continue to improve in the future. Comparison of the advantages and disadvantages of the various approaches are considered, with special attention to not only the computational cost of the level of theory, but also the various approaches that can be used to compute the absorption spectra with a large number of high energy excited states.

Kasper, Joseph M.↗

DOE OSTI2020

Nuclear-Electronic Orbital Ehrenfest Dynamics

The recently developed real-time nuclear-electronic orbital (RT-NEO) approach provides an elegant framework for treating electrons and selected nuclei, typically pro- tons, quantum mechanically in nonequilibrium dynamical processes. However, the RT-NEO approach neglects the motion of the other nuclei, preventing a complete de- scription of the coupled nuclear-electronic dynamics and spectroscopy. In this work, we describe the dynamical interaction between the other nuclei and the electron-proton subsystem with the mixed quantum-classical Ehrenfest dynamics method. The NEO- Ehrenfest approach propagates the electrons and quantum protons in a time-dependent variational framework, while the remaining nuclei move classically on the correspond- ing average electron-proton vibronic surface. This approach includes the non-Born- Oppenheimer eects between the electrons and quantum protons with RT-NEO and between the classical nuclei and the electron-proton subsystem with Ehrenfest dynam- ics. Spectral features for vibrational modes involving both quantum and classical nuclei are resolved from the time-dependent dipole moments. Moreover, nuclear quantum ef- fects are included directly in nonadiabatic dynamics simulations. The excited state intramolecular proton transfer in the o-hydroxybenzaldehyde molecule is shown to be faster and to exhibit a larger kinetic isotope eect with NEO-Ehrenfest compared to classical Ehrenfest dynamics. This work shows that the NEO-Ehrenfest method is a powerful tool to study dynamical processes with coupled electronic and nuclear degrees of freedom.

Zhao, Luning↗

DOE OSTI2020

Outer membrane vesicles catabolize lignin-derived aromatic compounds in Pseudomonas putida KT2440

Lignin is an abundant and recalcitrant component of plant cell walls. While lignin degradation in nature is typically attributed to fungi, growing evidence suggests that bacteria also catabolize this complex biopolymer. However, the spatiotemporal mechanisms for lignin catabolism remain unclear. Improved understanding of this biological process would aid in our collective knowledge of both carbon cycling and microbial strategies to valorize lignin to value-added compounds. Here, we examine lignin modifications and the exoproteome of three aromatic–catabolic bacteria: Pseudomonas putida KT2440, Rhodoccocus jostii RHA1, and Amycolatopsis sp. ATCC 39116. P. putida cultivation in lignin-rich media is characterized by an abundant exoproteome that is dynamically and selectively packaged into outer membrane vesicles (OMVs). Interestingly, many enzymes known to exhibit activity toward lignin-derived aromatic compounds are enriched in OMVs from early to late stationary phase, corresponding to the shift from bioavailable carbon to oligomeric lignin as a carbon source. In vivo and in vitro experiments demonstrate that enzymes contained in the OMVs are active and catabolize aromatic compounds. Taken together, this work supports OMV-mediated catabolism of lignin-derived aromatic compounds as an extracellular strategy for nutrient acquisition by soil bacteria and suggests that OMVs could pote

biological funneling↗

DOE OSTI2023

Addressing Human and Organizational Factors in Nuclear Industry Modernization: A Sociotechnically Based Strategic Framework

The modernization of nuclear power plants will require an advanced concept of operations, involving an integrated set of tightly coupled systems in which all stakeholders act in a coordinated manner. For this modernization effort to be enabled, we developed a human and organizational factors approach based on a broad sociotechnical framework. Starting from core human factors principles, we conducted a literature review of the methods and approaches relevant to the modernization problem. These included not only core disciplines such as cognitive systems engineering, systems theoretic accident modeling and processes, human systems integration, resilience engineering, and macroergonomics but also related topics of safety culture and organizational change. From this literature, we developed a conceptual framework centered around the work system with its four interacting components: people, technology, process, and governance. In an effective work system, these four components are jointly optimized according to three systems criteria: efficiency, effectiveness, and safety. System failure may result from excessive emphasis on any one criterion. The actual work of attaining joint optimization in a given work system can be accomplished by utilizing three high-level functions: knowledge elicitation, knowledge representation, and cross-functional integration. Finally, we illustrated the utility of this approach by applying it to practical problems and case studies.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

The Legendre Polynomial Axial Expansion Method

This work presents a new formulation of the axial expansion transport method explicitly using Legendre polynomials for arbitrarily high-order expansions. This new formulation also features an alternative method of axial leakage calculation to allow for nonextruded flat source region meshes. This alternative axial leakage is introduced alongside a balance equation requirement to ensure that neutron balance is preserved in the coarse mesh for a given axial leakage formulation, which allows for effective coarse mesh finite difference acceleration. A matrix exponential table method is derived to allow for fast computations of arbitrarily high-order matrix exponentials for this work and precludes the need for further research into matrix exponential calculations for this method. Numerical results are presented that demonstrate the stability of the axial expansion method in systems with voidlike regions, showcase the speedup from matrix exponential tables, and investigate the axial convergence of the method in terms of both expansion order and mesh size.

Herring, Nicholas↗

DOE OSTI2025

Multiphysics Running-In Simulations for Pebble-Bed Reactors with Griffin

Griffin, a Multiphysics Object-Oriented Simulation Environment (MOOSE)–based application targeting transient modeling of advanced reactors, has been used recently to model pebble-bed reactors (PBRs). The modeling effort has focused thus far on equilibrium core calculations. A new capability to simulate the running-in phase of PBR operation has been added to Griffin. This work demonstrates the new capability with a coupled multiphysics running-in simulation. Griffin computes power densities in the core at each time step of the running-in simulation and passes these to Pronghorn, which models fluid flow and heat transfer to calculate pebble surface temperatures. These surface temperatures are used along with the power densities in a heat conduction model to compute average fuel and moderator temperatures, which are passed back to Griffin and accounted for with temperature-dependent cross sections. This work also describes a novel methodology for determining appropriate pebble feed rates and control rod positioning during the running-in simulation. Furthermore, the RZ-geometry model used in this work requires minimal computational resources and can be used for optimization and uncertainty studies in future works.

Griffin↗

DOE OSTI2024

Evaluation of Digital Nautical Chart data for confirmation and expansion of GeoNames data

Here, this work examines how Digital Nautical Chart (DNC) data may contribute to the evolution and refinement of GeoNames data for near-shore features. GeoNames features are point data with one or more possible place names. DNC Earth Cover Text (ECRText) objects are map labels positioned nearby their real word counterpart. ECRText feature map position strikes a compromise between association with real features and cartographic readability. This work explores whether ECRText features can confirm (or expand names for) existing locations or contribute new locations through data conflation. Due to name variations and spatial position, conflating these data are nontrivial. Previous work engaged in a brief examination using the trigram string matching algorithm under coarse proximity constraints, indicating that ECRText could provide additional value to GeoNames. This work builds on that study, by engaging in a deeper examination of spatial proximity and exploring conflation agreement across an ensemble of string matching approaches. The result finds strong ensemble agreement about ECRText features which already exist in GeoNames but mixed results about which features contribute new information, as well as exploring why some of these matching techniques fail. With an eye toward automation, computational efficiency was found not to be a constraint in sustaining updates.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗

DOE OSTI2024

Cooper minima in high-Z atoms: effects of correlation and relativity on np photoionization

Abstract Photoionization dipole transition matrix elements pass through a zero or attain a minimum that leaves imprints on photoionization parameters like the cross-section, angular distribution asymmetry parameter, phase shift, and photoionization time delay. This minimum is commonly known as the ‘Cooper minimum’ (CM). The CM, in general, is strongly affected by relativistic and correlation effects. Previous works investigated CM in the 6pand 5psubshell photoionization up toZ= 100 using the single-particle Dirac-Slater (DS) method. The present work extends the earlier work toZup to 120 using more accurate methods; Dirac–Hartree–Fock (DHF) which includes the relativistic effects and exchange correlations, and the relativistic random phase approximation (RRPA) which includes both initial and final state electron-electron correlations along with relativistic effects. In addition to the study of photoionization from the 6pand 5psubshells, the 4psubshell has also been investigated in the present work. To demonstrate the prominent effects in the high-Z atoms, Rn (Z= 86), Ra (Z= 88), No (Z= 102), Cn (Z = 112), Og (Z= 118), and Ubn (Z= 120) are investigated.

Optics↗

DOE OSTI2021

Incorporation of Ti in epitaxial Fe2TiO4 thin films

The titanomagnetites (Fe2-xTixO4, x = 1) are a family of reducible spinel-structure oxides of interest for their favorable magnetic, catalytic, and electrical transport properties. To understand the stability of the system during low temperature deposition, epitaxial thin films of Fe2TiO4 were deposited by molecular beam epitaxy on MgO(001) at 250 – 375°C. The homogeneous incorporation of Ti, Fe valence, and film morphology were all found to be strongly dependent on the oxidation conditions at the low substrate temperatures employed. More oxidizing conditions led to phase separation into epitaxial, faceted Fe3O4 and rutile TiO2. Less oxidizing conditions resulted in polycrystalline films that exhibited Ti segregation to the film surface, as well as mixed Fe valence (Fe3+, Fe2+, Fe0). A narrow window of intermediate oxygen partial pressure during deposition yielded nearly homogeneous Ti incorporation and a large fraction of Fe2+. However, these films were poorly crystallized, and no occupation of tetrahedral sites in the spinel lattice by Fe2+ was detected by x-ray magnetic circular dichroism at the Fe L-edge. After vacuum annealing, a small fraction of Fe2+ was found to occupy tetrahedral sites. Comparison of these results with previous work suggests that the restriction of the deposition conditions to low temperature by the MgO substrate limits the incorporation of Ti into the spinel lattice. This work suggests a path towards obtaining stoichiometric, well-crystallized Fe2TiO4 by MBE by utilizing high substrate temperature and low oxygen partial pressure during deposition on temperature-stable substrates.

Kaspar, Tiffany C.↗