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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Electrolyte Role in SEI Evolution at Si in the Pre-lithiation Stage vs the Post-lithiation Stage

The formation and evolution of the dynamic solid electrolyte interphase (SEI) at the Si anode/electrolyte interface are yet to be completely understood to solve irreversible capacity loss and increase battery cycle life. Herein, the evolution of SEI and its dynamic properties at the Si anode/electrolyte interface are investigated in two electrolyte systems, a 1.2 M LiPF6 in EC: EMC 3:7 (wt%) electrolyte (referred to as Gen2) and a 1.2 M LiTFSI in EC: EMC 3:7 (wt%) electrolyte (referred to as LiTFSI). Two lithiation stages are studied: the pre-lithiation (pre-Li) SEI stage and the post-lithiation (post-Li) stage. Findings reveal at the pre-Li, SEI formation starts at an early potential and contributes to the greater mass gain in the Si/Gen2, and it is dominated by the formation of a non-uniform F- and P-rich layer in Si/Gen2, in contrast to a homogeneous F- and C-containing layer at the Si/LiTFSI interphase. The initially formed SEI in LiTFSI further benefits the charge transfer kinetics. At the post-Li stage, a more substantial SEI evolution is observed at Si/LiTFSI. This paper offers a foundational understanding of the SEI dynamic evolution with electrolyte dependence. Findings from this report offer important insights into solving the complex SEI stability issues on Si.

25 ENERGY STORAGE↗
DOE OSTI2020

Artificial Intelligence for Dynamic Phase Transitions in Materials [PowerPoint]

The presentation covers the following areas: emergent phenomena and non-equilibrium transitions in granular materials; materials science applications, including defects, interfaces and emergent phenomena; modeling with molecular dynamics simulations; principal component analysis (PCA); previous works; PCA applied to nonequilibrium transitions; PCA for varied quenched disorder; PCA incorporating particle velocity; and ending with a summary and impacts.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Phase Transitions and Scaling in Systems Far from Equilibrium

Scaling ideas and renormalization group approaches proved crucial for a deep understanding and classification of critical phenomena in thermal equilibrium. Over the past decades, these powerful conceptual and mathematical tools were extended to continuous phase transitions separating distinct nonequilibrium stationary states in driven classical and quantum systems. In concordance with detailed numerical simulations and laboratory experiments, several prominent dynamical universality classes have emerged that govern large-scale, long-time scaling properties both near and far from thermal equilibrium. These pertain to genuine specific critical points as well as entire parameter space regions for steady states that display generic scale invariance. The exploration of nonstationary relaxation properties and associated physical aging scaling constitutes a complementary potent means to characterize cooperative dynamics in complex out-of-equilibrium systems. Here, this review describes dynamic scaling features through paradigmatic examples that include near-equilibrium critical dynamics, driven lattice gases and growing interfaces, correlation-dominated reaction-diffusion systems, and basic epidemic models.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Optimization of Thermal Conductance at Interfaces Using Machine Learning Algorithms

We report optimization of thermal transport across the interface of two different materials is critical to micro-/nanoscale electronic, photonic, and phononic devices. Although several examples of compositional intermixing at the interfaces having a positive effect on interfacial thermal conductance (ITC) have been reported, an optimum arrangement has not yet been determined because of the large number of potential atomic configurations and the significant computational cost of evaluation. On the other hand, computation-driven materials design efforts are rising in popularity and importance. Yet, the scalability and transferability of machine learning models remain as challenges in creating a complete pipeline for the simulation and analysis of large molecular systems. In this work we present a scalable Bayesian optimization framework, which leverages dynamic spawning of jobs through the Message Passing Interface (MPI) to run multiple parallel molecular dynamics simulations within a parent MPI job to optimize heat transfer at the silicon and aluminum (Si/Al) interface. We found a maximum of 50% increase in the ITC when introducing a two-layer intermixed region that consists of a higher percentage of Si. Because of the random nature of the intermixing, the magnitude of increase in the ITC varies. We observed that both homogeneity/heterogeneity of the intermixing and the intrinsic stochastic nature of molecular dynamics simulations account for the variance in ITC.

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

Frequency Control and Disturbance Containment Using Grid-Forming Embedded Storage Networks

The paper presents a distributed approach for operating a network of inverter-based energy storage resources embedded in a bulk power system. Departing from their traditional role of steady-state reserves, the storage assets in the network are utilized as frequency-responsive resources shaping system dynamics. The power electronics converter systems interfacing the storage resources are equipped with local controllers designed to respond under transient disturbances. To this end, a safety-constrained distributed control strategy is explored. The paper compares the performance of converter-interfaced grid-forming and grid-following storage networks for fast frequency control and disturbance containment/localization. Sensitivity studies are performed to study the impact of storage size, steady-state dispatch, and controller design on dynamic performance. The findings are presented through case studies with results from the IEEE test systems.

Chatterjee, Kaustav (ORCID:0000000153273860)↗
DOE OSTI2021

On the Development of Order and Interfaces during the Growth of Ultrathin La 2 CuO 4 Films by Molecular Beam Epitaxy

While the atomic structure of interfaces in complex oxide heterostructures created by epitaxial growth has been investigated extensively, few studies have been conducted on how interfaces form and restructure at the initial stage of film growth. The dynamic aspects of the growth behavior can strongly influence the final interfacial atomic structure, which may lead to the emergence of interface-specific properties, such as the rise of interfacial superconductivity between certain Ruddlesden-Popper oxide materials. In this report, the structural development of La2CuO 4 thin films grown by molecular beam epitaxy on a LaSrAlO 4 substrate is investigated by X-ray diffraction measurements with rapid scans over a volume of reciprocal space. This method provides far more detailed information on interface formation than traditional fixed-point measurements. The results show that the atomic structure of the interface becomes fully established after just a single unit cell of growth. Interestingly, restructuring continues to occur within the topmost half to one unit cell of the film during the deposition process. However, diffraction intensity oscillations from both reflection high-energy electron and X-ray measurements stabilize only after the growth of two unit cells, indicating that the growth front morphology continues to evolve until the start of the third unit cell. This multimodal investigation provides insights into the atomic processes taking place during layered oxide interface formation, including the dynamical rearrangement of LaO and CuO 2 layers. Such information is not only relevant to the engineering and optimization of functional layer structures but can also be critical for ultrathin films.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Structure and Dynamics of Aqueous Electrolytes at Quartz (001) and (101) Surfaces

Here, understanding and describing reactivity at mineral-water interfaces such as ion adsorption, the kinetics of dissolution, or surface charge development depends on our ability to improve the accuracy of electrical double layer (EDL) models. While molecular dynamics (MD) simulations are routinely used to investigate the structure and energetics of adsorbed ions comprising the EDL, less attention is paid to their self-diffusion dynamics, which can uniquely inform on coupling to interfacial reactions. Here we use MD to investigate both the organization and diffusion dynamics of water and electrolyte ions (NaCl, KCl, CaCl 2 ) at hydroxylated quartz (001) and (101) surfaces, a comparison which allowed us to assess surface structural effects of corrugation and silanol density. We found that inner- versus outer-sphere complex formation depends on cation size and charge but not necessarily hydration energies. Participation of surface silanols in the hydration spheres of Na + and K + generally indicated their preference for inner-sphere complexation, but this depends strongly on the orientation of the surface considered through its influence over the organization and dynamics of adsorbed water layers. In particular, surface orientation substantially affects the diffusive behavior of the near-surface water. Na + was found to decrease the mobility of water in the first layer, consistent with an increasing frequency of hydrolysis implied by faster quartz dissolution rates observed in experiments via the well known salt effect. Our results are also in good agreement with the observed dissolution rate of quartz vs. surface adsorption strength measure by Dove and Nix. This study sets the stage for a forthcoming paper examining how the dynamics at quartz/electrolyte interfaces are influenced by externally applied electric fields.

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

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

A remarkable feature of QCD is that the mass scale $k$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4 ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $q\bar{q}$ invariant mass. The same result, including spin terms, is obtained using light-front holography$-$the duality between the front form and AdS 5 , the space of isometries of the conformal group$-$if one modifies the action of AdS 5 by the dilaton e $κ^2z^2$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κκ underlying confinement and hadron masses can be connected to the parameter Λ $\overline{MS}$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2 ) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front-form vacuum has important consequences for the cosmological constant. In conclusion, I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with sum rules for nuclear parton distribution functions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra and other Advances in Light-Front QCD

Here, light-front holography, together with superconformal algebra, have provided new insights into the physics of color confinement and the spectroscopy and dynamics of hadrons. As shown by de Alfaro, Fubini and Furlan, a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the procedure of de Alfaro et al. to the frame-independent light-front Hamiltonian, it leads uniquely to a confining qq¯ potential κ 4 ζ 2 , where ζ 2 is the light-front radial variable related in momentum space to the qq¯ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS 5 , the space of isometries of the conformal group—if one modifies the action of AdS 5 by the dilaton e κ 2 z 2 in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions lead to a a unified Regge spectroscopy of meson, baryon, and tetraquarks, including supersymmetric relations between their masses and their wavefunctions. One also predicts hadronic light-front wavefunctions and observables such as structure functions, transverse momentum distributions, and the distribution amplitudes. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ MS¯ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2 ) defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. I also discuss a number of applications of light-front phenomenology.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Quantitative interpretation of molecular dynamics simulations for X-ray photoelectron spectroscopy of aqueous solutions

Over the past decade, energy-dependent ambient pressure X-ray photoelectron spectroscopy (XPS) has emerged as a powerful analytical probe of the ion spatial distributions at the vapor (vacuum)-aqueous electrolyte interface. These experiments are often paired with complementary molecular dynamics (MD) simulations in an attempt to provide a complete description of the liquid interface. There is, however, no systematic protocol that permits a straightforward comparison of the two sets of results. XPS is an integrated technique that averages signals from multiple layers in a solution even at the lowest photoelectron kinetic energies routinely employed, whereas MD simulations provide a microscopic layer-by-layer description of the solution composition near the interface. Here, we use the National Institute of Standards and Technology database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to quantitatively interpret atom-density profiles from MD simulations for XPS signal intensities using sodium and potassium iodide solutions as examples. We show that electron inelastic mean free paths calculated from a semi-empirical formula depend strongly on solution composition, varying by up to 30% between pure water and concentrated NaI. The XPS signal thus arises from different information depths in different solutions for a fixed photoelectron kinetic energy. XPS signal intensities are calculated using SESSA as a function of photoelectron kinetic energy (probe depth) and compared with a widely employed ad hoc method. SESSA simulations illustrate the importance of accounting for elastic-scattering events at low photoelectron kinetic energies (<300 eV) where the ad hoc method systematically underestimates the preferential enhancement of anions over cations. Finally, some technical aspects of applying SESSA to liquid interfaces are discussed.

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

New Insights into Color Confinement, Hadron Dynamics, Spectroscopy, and Jet Hadronization from Light-Front Holography and Superconformal Algebra

A fundamental problem in hadron physics is to obtain a relativistic color-confining, first approximation to QCD which can predict both hadron spectroscopy and the frame-independent light-front (LF) wavefunctions underlying hadron dynamics. The QCD Lagrangian with zero quark mass has no explicit mass scale; the classical theory is conformally invariant. Thus, a fundamental problem is to understand how the mass gap and ratios of masses – such as mρ/mp – can arise in chiral QCD. De Alfaro, Fubini, and Furlan have made an important observation that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator and rescales the time variable. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4 ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the $q\bar{q}$ invariant mass squared. The same result, including spin terms, is obtained using light-front holography – the duality between light-front dynamics and AdS 5 , the space of isometries of the conformal group if one modifies the action of AdS 5 by the dilaton e $κ^2$ z$^2$ in the fifth dimension z . When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κ underlying confinement and hadron masses can be connected to the parameter Λ $\overline{MS}$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling α s (Q 2 ) defined at all momenta. Lastly, the matching of the high and low momentum transfer regimes also determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

First-principles study of grain-boundary wetting in Fe-Σ5(013)[100] tilt boundary

Here, we report an ab-initio study of grain-boundary wetting (GBW) in three systems (Fe/Zn, Fe/Pb & Fe/Bi) on a Σ5(013)[100] tilt grain boundary. An energy-based approach is pursued and adapted to the study of liquid-metal/solid-metal interfaces. We provide a sound calculation of the wettability parameter S (i.e., defined as the minimum energy difference between the unbroken initial state and final state with liquid-metal/solid-metal interfaces). Solid/liquid interfaces are modelled by ab-initio molecular dynamics, also allowing a study of structural effects in the liquid phase near the solid interface. We show how surface energies for solid-metal/liquid-metal interfaces need a special treatment for the liquid-metal chemical potential due to the change in crystallinity near the interface. The computation of the wettability criterion for the three systems correctly predicts the GBW trend known experimentally for these systems. The computations are compared with small-scale TEM experiments on GBW of two systems (Fe/Pb and Fe/Bi) and it is shown to provide reasonable results. This approach offers new perspectives in predicting GBW trends across various systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Reconfigurable and Dynamic Distribution Systems Enabled Using Self-Sustainable Minimal-Microgrids with Region Based Stability Guarantees

In this paper, a reconfigurable and dynamic distribution system is designed using self-sustainable minimal-microgrids (min-MGs). Particularly, multiple dynamic microgrids are implemented by aggregating local min-MGs in a controllable way to facilitate service restoration at critical grid infrastructures, especially during severe power outages (e.g., those induced by natural disasters). These dynamic microgrids are implemented surrounding inverter interfaced distributed energy resources (DERs) to pick up local critical loads. Stable transient process during neighboring microgrid disconnection and resynchronization is realized by involving additional control terms in the secondary control level. Meanwhile, in order to ensure a stable operation with dynamic topology change, a computationally efficient region-based stability assessment approach is developed to ensure stability guarantees of each inverter dominated min-MG with potential changes of external grids modeled as disturbances. In contrast to conventional point-by-point stability evaluation approaches, the proposed region-based stability analysis can intuitively exhibit the feasible region comprised of stable operating points and identify sufficient stability margin to tolerate disturbances of dynamic system topology variations. Theoretical analysis is verified using simulation in MATLAB/Simulink.

distribution systems↗
DOE OSTI2021

Transformative high entropy alloy conquers the strength-ductility paradigm by massive interface strengthening

Recent metastable alloy designs have demonstrated simultaneous attainment of high ultimate tensile strength (UTS) and ductility in high entropy alloys but with low yield strength. In this work, we present new strategy for improving the work hardenability and yield strength (YS) together in Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 high entropy alloy (Cu-HEA). Drastic increase in the YS (1.5 GPa) is attributed to the formation of γ/ε, ε/ε (twin type) and ε/ε (plate type) interfaces in the microstructure due to extreme grain refinement whereas high UTS-ductility synergy (2.2 GPa, 15%) is attained by dynamic Hall-Petch hardening across these interfaces (i.e. massive interface strengthening) and transformation induced plasticity in γ phase. Thus, this harmonious combination of YS and UTS-ductility synergy in Cu-HEA outperform all structural materials till date. Therefore, deformation-induced massive interface strengthening is a new, yet cost-effective pathway for synergizing the benefits of advanced steels and high entropy alloys together in a material by conventional processing route.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Multifactor Experiment and Model Integration to Determine the Regional Vulnerability of Permafrost Carbon to Climate Change. Final report

The major research goal of this project was to understand and quantify the fate of carbon stored in permafrost ecosystems using a combination of field and laboratory experiments to measure and model isotope ratios and carbon fluxes in a tundra ecosystem exposed to experimental warming. Field measurements centered on a two-factor experimental warming to increase air and soil temperatures alone, and in combination, at a tundra field site in Alaska. A second manipulation of water table was embedded within the warming treatment such that both major environmental factors (temperature, moisture) controlling ecosystem carbon dynamics were experimentally altered. The experiment was interfaced with modeling activities using both data assimilation and forward modeling approaches. Models were used to make forecasts of ecosystem carbon dynamics beyond the time frame and environmental space of the experiment itself. These results were linked with ongoing synthesis and model intercomparison activities through the Permafrost Carbon Network, which led to additional synthesis publications as a result of collaboration and data sharing from this project. As key outcomes, this project has produced new papers published in the peer-reviewed literature, archived datasets used for model-data intercomparisons, trained graduate students and postdoctoral researchers, and has raised awareness about the vulnerability of permafrost carbon to a wider audience.

54 ENVIRONMENTAL SCIENCES↗