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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SU-E-T-800: Verification of Acurose XB Dose Calculation Algorithm at Air Cavity-Tissue Interface Using Film Measurement for Small Fields of 6-MV Flattening Filter-Free Beams

Purpose: To verify the dose accuracy of Acuros XB (AXB) dose calculation algorithm at air-tissue interface using inhomogeneous phantom for 6-MV flattening filter-free (FFF) beams. Methods: An inhomogeneous phantom included air cavity was manufactured for verifying dose accuracy at the air-tissue interface. The phantom was composed with 1 and 3 cm thickness of air cavity. To evaluate the central axis doses (CAD) and dose profiles of the interface, the dose calculations were performed for 3 × 3 and 4 × 4 cm{sup 2} fields of 6 MV FFF beams with AAA and AXB in Eclipse treatment plainning system. Measurements in this region were performed with Gafchromic film. The root mean square errors (RMSE) were analyzed with calculated and measured dose profile. Dose profiles were divided into inner-dose profile (>80%) and penumbra (20% to 80%) region for evaluating RMSE. To quantify the distribution difference, gamma evaluation was used and determined the agreement with 3%/3mm criteria. Results: The percentage differences (%Diffs) between measured and calculated CAD in the interface, AXB shows more agreement than AAA. The %Diffs were increased with increasing the thickness of air cavity size and it is similar for both algorithms. In RMSEs of inner-profile, AXB was more accurate than AAA. The difference was up to 6 times due to overestimation by AAA. RMSEs of penumbra appeared to high difference for increasing the measurement depth. Gamma agreement also presented that the passing rates decreased in penumbra. Conclusion: This study demonstrated that the dose calculation with AXB shows more accurate than with AAA for the air-tissue interface. The 2D dose distributions with AXB for both inner-profile and penumbra showed better agreement than with AAA relative to variation of the measurement depths and air cavity sizes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Capturing 3D atomic defects and phonon localization at the 2D heterostructure interface

The three-dimensional (3D) local atomic structures and crystal defects at the interfaces of heterostructures control their electronic, magnetic, optical, catalytic, and topological quantum properties but have thus far eluded any direct experimental determination. Here, we use atomic electron tomography to determine the 3D local atomic positions at the interface of a MoS 2 -WSe 2 heterojunction with picometer precision and correlate 3D atomic defects with localized vibrational properties at the epitaxial interface. We observe point defects, bond distortion, and atomic-scale ripples and measure the full 3D strain tensor at the heterointerface. By using the experimental 3D atomic coordinates as direct input to first-principles calculations, we reveal new phonon modes localized at the interface, which are corroborated by spatially resolved electron energy-loss spectroscopy. We expect that this work will pave the way for correlating structure-property relationships of a wide range of heterostructure interfaces at the single-atom level.

42 ENGINEERING↗
DOE OSTI2022

Dynamics of active liquid interfaces

Controlling interfaces of phase-separating fluid mixtures is key to the creation of diverse functional soft materials. Traditionally, this is accomplished with surface-modifying chemical agents. Using experiment and theory, we studied how mechanical activity shapes soft interfaces that separate an active and a passive fluid. Chaotic flows in the active fluid give rise to giant interfacial fluctuations and noninertial propagating active waves. At high activities, stresses disrupt interface continuity and drive droplet generation, producing an emulsion-like active state composed of finite-sized droplets. When in contact with a solid boundary, active interfaces exhibit nonequilibrium wetting transitions, in which the fluid climbs the wall against gravity. These results demonstrate the promise of mechanically driven interfaces for creating a new class of soft active matter.

Science & Technology - Other Topics↗
DOE OSTI2019

Ab Initio Study of the Interface of the Solid-State Electrolyte Li 9 N 2 Cl 3 with a Li-Metal Electrode

Ab initio molecular dynamics study of an electrochemical interface between a solid-state-electrolyte Li 9 N 2 Cl 3 and a Li-metal is performed to analyze interphase formation due to electrochemical instability. An external electric field is applied to emulate the interface under charging conditions. At open circuit, we observed electrochemical stability at both sides of the interface, without electrolyte decomposition, or new phase formation, in good agreement with reported experiments. However, a structural re-accommodation takes place at both sides of the interface. Some oxidation of the surface Li-atoms takes place when Cl and N anions capture Li from the metal to complete octahedral structures, a Bader charge and electron density analyses explain the difference between Cl and N behavior. At the interface with the Li 9 N 2 Cl 3 (002) facet, the larger negative charge on low-coordinated N atoms is able to retain more Li atoms than the Cl atoms do. At charging conditions applying an external electric field (0.5 V/Å), no major changes are observed in atomic diffusion or structural changes at the interphase; however, the main difference is the change of the Li-metal crystal structure. Due to migration of Li from the metal anode to the electrolyte, vacancies are created on the anode, causing a structural re-arrangement at the anode surface.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnetism of Complex Oxide Interfaces

This chapter reviews theoretical studies focused on interfaces or heterostructures of complex oxides such as perovskite transition-metal oxides (TMO). It describes examples of such theoretical studies of TMO interfaces employing a variety of methods. The chapter explains theoretical work at the interfaces of a ferroelectric and a magnetic manganite and provides rules to judge the type of coupling between the spins at opposite sides of the interfaces. It shows how the electric field of the ferroelectric component affects the electronic density of the other component, typically a metallic manganite, thus altering its transport properties and sometimes even inducing a phase transition. The chapter explores the puzzling exchange bias effect is addressed for the interfaces involving a ferromagnet on one side and a G-type antiferromagnetic state on the other. If the interfacial carrier density is modulated away from the region, the ferromagnetism and transport will become worse.

Okamoto, Satoshi↗
DOE OSTI2018

Titanium-Carbide Formation at Defective Curved Graphene-Titanium Interfaces

ABSTRACT Physical and chemical properties of graphene-metal interfaces have been largely examined with the objective of producing nanostructured carbon-based electronic devices. Although electronic properties are key to such devices, appropriate structural, thermal and mechanical properties are important for device performance as well. One of the most studied is the graphene-titanium (G-Ti) interface. Titanium is a low density, high strength versatile metal that can form alloys with desirable properties for applications ranging from aerospace to medicine. Small clusters and thin films of titanium deposited on graphene have also been examined. However, while some experiments show that thin films of titanium on graphene can be removed without damaging graphene hexagonal structure, others reported the formation of titanium-carbide (TiC) at G-Ti interfaces. In a previous work [ACS Appl. Mater. Interfaces, 2017, 9 (38), pp 33288-33297], we have shown that pristine G-Ti interfaces are resilient to large thermal fluctuations even when G-Ti structures lie on curved or kinked substrates. Here, using classical molecular dynamics with the third-generation Charge Optimized Many Body (COMB3) potential, we show that di-interstitial defective G-Ti structures on a copper substrate with a relatively large curvature kink, present signs of TiC formation. This result might help explain the different experimental results mentioned above.

catalysis (heterogeneous), defects, membrane, carb↗
DOE OSTI2015

Role of hydration forces in the properties of electrolyte solutions in the bulk and at interfaces

We present a theoretical approach for modeling electrolyte solutions at interfaces that reaches into the mesoscale while retaining molecular detail. The total Hamiltonian of the system includes interactions arising from density and charge density (ion correlation) fluctuations, direct Coulomb interactions between ions, and at interfaces the image interactions, ion-solid and ion-water dispersion interactions. The model was validated against its ability to reproduce ion activity in 1:1 and 2:1 electrolyte solutions in the 0-2 M concentration range, its ability to capture the ion-specific effect in 1:1 electrolytes at the air-water interface, and solvent structure in a confined environment between hydrophobic surfaces, revealing the central role of ion hydration interactions in specific ion thermodynamic properties in the bulk solutions and at interfaces. The model is readily extensible to treat electrolyte interactions and forces across charged solid-water interfaces.

Sushko, Maria L.↗
DOE OSTI2016

MuSim, a Graphical User Interface for Multiple Simulation Programs

MuSim is a new user-friendly program designed to interface to many different particle simulation codes, regardless of their data formats or geometry descriptions. It presents the user with a compelling graphical user interface that includes a flexible 3-D view of the simulated world plus powerful editing and drag-and-drop capabilities. All aspects of the design can be parametrized so that parameter scans and optimizations are easy. It is simple to create plots and display events in the 3-D viewer (with a slider to vary the transparency of solids), allowing for an effortless comparison of different simulation codes. Simulation codes: G4beamline, MAD-X, and MCNP; more coming. Many accelerator design tools and beam optics codes were written long ago, with primitive user interfaces by today's standards. MuSim is specifically designed to make it easy to interface to such codes, providing a common user experience for all, and permitting the construction and exploration of models with very little overhead. For today's technology-driven students, graphical interfaces meet their expectations far better than text-based tools, and education in accelerator physics is one of our primary goals.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Electronic Structure of Buried Interfaces - Oral Presentation [Slides]

In the electronics behind computer memory storage, the speed and size are dictated by the performance of permanent magnets inside devices called read heads. Complicated magnets made of stacked layers of thin films can be engineered to have properties that yield more energy storage and faster switching times compared to conventional iron or cobalt magnets. The reason is that magnetism is a result of subtle interactions amongst electrons; just how neurons come together on large scales to make cat brains and dog brains, ensembles of electrons interact and become ferromagnets and paramagnets. These interactions make magnets too difficult to study in their entirety, so I focus on the interfaces between layers, which are responsible for the coupling materials physicists hope to exploit to produce next-generation magnets. This project, I study a transition metal oxide material called LSCO, Lanthanum Cobaltite, which can be a paramagnet or a ferromagnet depending on how you tweak the electronic structure. It exhibits an exciting behavior: its sum is greater than the sum of its parts. When another similar material called a LSMO, Lanthanum Manganite, is grown on top of it, their interface has a different type of magnetism from the LSCO or the LSMO! I hope to explain this by demonstrating differently charged ions in the interface. The typical method for quantifying this is x-ray absorption, but all conventional techniques look at every layer simultaneously, averaging the interfaces and the LSCO layers that we want to characterize separately. Instead, I must use a new reflectivity technique, which tracks the intensity of reflected x-rays at different angles, at energies near the absorption peaks of certain elements, to track changes in the electronic structure of the material. The samples were grown by collaborators at the Takamura group at U.C. Davis and probed with this “resonant reflectivity” technique on Beamline 2-1 at the Stanford Synchrotron Radiation Lightsource. This project was funded by the Department of Energy and supported by the SLAC National Accelerator Laboratory. Preliminary results suggest that different ionic charges are indeed responsible for the different magnetic properties at the interface, which is promising because charge is easy to control. Once scientists understand how to tune the magnetic properties of materials like LSCO and LSMO, industries get closer to designing the magnets that will soon revolutionize consumer electronics.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Requirements Document for Development of a Livermore Tomography Tools Interface

In this document, we outline an exercise performed at LLNL to evaluate the user interface deficits of a LLNL-developed CT reconstruction software package, Livermore Tomography Tools (LTT). We observe that a difficult-to-use command line interface and the lack of support functions compound to generate a bottleneck in the CT reconstruction process when input parameters to key functions are not well known. Through the exercise of systems engineering best practices, we generate key performance parameters for a LTT interface refresh, and specify a combination of back-end (“test-mode” functions) and front-end (graphical user interface visualization and command scripting tools) solutions to LTT’s poor user interface that aim to mitigate issues and lower costs associated with CT reconstruction using LTT. Key functional and non-functional requirements and risk mitigation strategies for the solution are outlined and discussed.

42 ENGINEERING↗
DOE OSTI2019

Shear Behavior of Bedded Salt Interfaces under Direct Shear Loading

Bedded salt contains interfaces between the host salt and other in situ materials such as clay seams, or different impurities such as anhydrite or polyhalite in contact with the salt. These inhomogeneities are thought to have first-order effects on the closure of nearby drifts and potential roof collapses. Despite their importance, characterizations of the peak shear strength and residual shear strength of interfaces in salt are extremely rare in the published literature. This paper presents results from laboratory experiments designed to measure the mechanical behavior of a bedding interface or clay seam as it is sheared. The series of laboratory direct shear tests reported in this paper were performed on several samples of materials from the Permian Basin in New Mexico. These tests were conducted at numerous normal and shear loads up to the expected in situ pre-mining stress conditions. Tests were performed on samples with a halite/clay contact, a halite/anhydrite contact, a halite/polyhalite contact, and on plain salt samples without an interface for comparison. Intact shear strength values were determined for all of the test samples along with residual values for the majority of the tests. The results indicated only a minor variation in shear strength, at a given normal stress, across all samples. This result was surprising because sliding along clay seams is regularly observed in the underground, suggesting the clay seam interfaces should be weaker than plain salt. Post-test inspections of these samples noted that salt crystals were intrinsic to the structure of the seam, which probably increased the shear strength as compared to a typical clay seam.

58 GEOSCIENCES↗
DOE OSTI2020

Coupling CTH to Linear Acoustic Propagation across an Air-Earth Interface

The interface between the Earth and the atmosphere forms a strong contrast in material properties. As such, numerical issues can arise when simulating an elastic wavefield across such a boundary when using a numerical simulation scheme. This is exacerbated when two different simulation codes are coupled straddling that interface. In this report we document how we implement the coupling of CTH, a nonlinear shock physics code, to a linearized elastic/acoustic wave propagation algorithm, axiElasti, across the air-earth interface. We first qualitatively verify that this stable coupling between the two algorithms produces expected results with no visible effects of the coupling interface. We then verify the coupling interface quantitatively by checking consistency with results from previous work and with coupled acoustic-elastic seismo-acoustic source inversions in three earth materials.

58 GEOSCIENCES↗
DOE OSTI2023

Energy Services Interface: Requirements Document

This energy services interface (ESI) requirements document represents a process step in the path for creating an ESI specification, which will describe the technical characteristics of an ESI. This document outlines the concepts that need to be covered in the ESI specification, such as principal functions of the ESI, grid services communicated through the ESI, and the ESI lifecycle. It provides context for the Department of Energy’s (DOE’s) Grid Modernization Laboratory Consortium (GMLC) to engage industry participants in the development of the ESI specification. To do this, it describes the desired contents of the ESI specification and provides examples of the type of material that needs to be included in it. The purpose of the ESI specification is to define the requirements that are to be addressed in information and communications technology (ICT) interface standards for enabling the integration of a facility containing responsive distributed energy resources (DER facility) to an electric system consistent with the fundamental ESI principles. In this context, a DER facility may consist of a single DER with a communicating controller or may be as complex as a microgrid campus with several buildings and many DERs. The ESI specification is not a technical interface standard, but the requirements in the specification can be used to check that existing, augmented, or new interface standards meet the interoperability requirements of the ESI concept, which is explained further in this document. In this way, the ESI specification can be used to guide standards advancement work in multiple standards development organizations. To explain the scope of the ESI specification, this ESI requirements document provides examples of situations (or illustrative applications) for using an ESI to coordinate DER flexibility for grid operations. These examples originate from foundational work for describing common grid-DER service agreements that are anticipated to be supported using this interface.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Emergent Phenomena at Mott Interfaces – a Time- and Depth-Resolved Approach (Final Technical Report)

This is the final technical report for Award DE-SC0019297, Emergent Phenomena at Mott Interfaces – a Time- and Depth-Resolved Approach. This research program aimed to address the scientific questions related to the emergence and control of non-equilibrium electronic phases of matter in strongly correlated Mott oxides and their interfaces. We were focusing specifically on exploiting the interfaces in heterostructures and superlattices, containing Mott oxides CaMnO 3 and LaNiO 3 because in such systems, precise control of electronic and magnetic structure in the ground state can be achieved through dimensionality, heterostructuring, interface termination, and lattice strain. We utilized advanced x-ray spectroscopic and scattering techniques, to investigate these phenomena. Additionally, we used intense THz electric-field pulses generated by a femtosecond laser to directly modify the electronic structure and magnetic states of the ultrathin LaNiO 3 and CaMnO 3 layers in such heterostructures, with the objectives of disentangling, understanding, and harnessing control over the intricate competing interactions responsible for two-dimensional magnetism and metal-insulator transition at the interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Protein-Nanoparticle Interactions Govern the Interfacial Behavior of Polymeric Nanogels: Study of Protein Corona Formation at the Air/Water Interface

Biomedical applications of nanoparticles require a fundamental understanding of their interactions and behavior with biological interfaces. Protein corona formation can alter the morphology and properties of nanomaterials, and knowledge of the interfacial behavior of the complexes, using in situ analytical techniques, will impact the development of nanocarriers to maximize uptake and permeability at cellular interfaces. In this study we evaluate the interactions of acrylamide-based nanogels, with neutral, positive, and negative charges, with serum-abundant proteins albumin, fibrinogen, and immunoglobulin G. The formation of a protein corona complex between positively charged nanoparticles and albumin is characterized by dynamic light scattering, circular dichroism, and surface tensiometry; we use neutron reflectometry to resolve the complex structure at the air/water interface and demonstrate the effect of increased protein concentration on the interface. Surface tensiometry data suggest that the structure of the proteins can impact the interfacial properties of the complex formed. These results contribute to the understanding of the factors that influence the bio-nano interface, which will help to design nanomaterials with improved properties for applications in drug delivery.

Traldi, Federico (ORCID:0000000161251012)↗
DOE OSTI2019

Interface Science Using Ambient Pressure Hard X-ray Photoelectron Spectroscopy

The development of novel in situ/operando spectroscopic tools has provided the opportunity for a molecular level understanding of solid/liquid interfaces. Ambient pressure photoelectron spectroscopy using hard X-rays is an excellent interface characterization tool, due to its ability to interrogate simultaneously the chemical composition and built-in electrical potentials, in situ. In this work, we briefly describe the “dip and pull” method, which is currently used as a way to investigate in situ solid/liquid interfaces. By simulating photoelectron intensities from a functionalized TiO2 surface buried by a nanometric-thin layer of water, we obtain the optimal photon energy range that provides the greatest sensitivity to the interface. We also study the evolution of the functionalized TiO2 surface chemical composition and correlated band-bending with a change in the electrolyte pH from 7 to 14. Our results provide general information about the optimal experimental conditions for characterizing the solid/liquid interface using the “dip and pull” method, and the unique possibilities offered by this technique.

Favaro, Marco (ORCID:0000000235028332)↗
DOE OSTI2022

Real-Sim Interface: Enabling Multi-resolution Simulation and X-in-the-Loop Development for Connected and Automated Vehicles

We report connected and automated vehicles (CAVs) can bring safety, mobility, and energy benefits to transportation systems. Ideally, CAV applications would be fully evaluated and validated prior to real-world implementation. However, many technical challenges in both software and hardware hinder the process. To comprehensively evaluate all aspects of CAV applications, an integrated evaluation environment is needed with various simulation tools from different domains. In the current literature, there lacks a well-developed interface to enable multi-resolution simulation of vehicle, traffic, virtual environment, and hardware-in-the-loop (HIL) simulation. In this work, a modular and flexible interface is developed to enable multi-resolution vehicle and traffic co-simulation for CAV applications. This interface is built upon Oak Ridge National Laboratory’s (ORNL’s) Real-Sim approach, can support various simulation tools and real-time X-in-the-loop (XIL) simulations, and is based on network communication protocols. The network communication delays are analyzed for simultaneous connection of up to 20 simulators. Then, two example applications are studied to demonstrate the potential usage of the Real-Sim interface: (1) a centralized merging scenario where the dynamics of two ego vehicles are emulated with detailed vehicle and powertrain dynamics models and (2) a signal-controller-in-the-loop (SCIL) evaluation where one intersection of the simulated traffic scenario is controlled by a physical signal controller. This Real-Sim interface is a tool that allows researchers to bring real, tangible hardware and software into simulated environments to comprehensively evaluate and support a wide variety of CAV applications.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

A General Method for Estimating Zonal Transmission Interface Limits from Nodal Network Data: Preprint

Capacity expansion models for the electric power system often employ zonal (rather than nodal) resolution, necessitating estimates of aggregate power transfer limits across the interfaces between model zones. Interface limits between planning areas are sometimes published, but they are not generalizable to arbitrary zone shapes. There is thus a need for a reproducible method for estimating interface transfer limits (ITLs) between user-defined zones directly from nodal transmission system data. Here, we present a simple method for estimating ITLs using a DC power flow approximation via the power transfer distribution factor (PTDF) matrix. Linear optimization is performed to identify the distribution of power flows that maximizes the total flow on interface-crossing lines, subject to individual line ratings, limits on bus injection/withdrawal, and the relationships among flows, injections, and withdrawals imposed by the PTDF matrix. We demonstrate the application of the method on a 134-zone ~65000-bus system, and we explore the influence of flow direction, contingency level, and zone size on the estimated ITLs. There is significant heterogeneity in the ratio of the ITL to the sum of interface-crossing line ratings, which highlights the importance of accounting for the physical constraints on power flows imposed by Kirchhoff's laws when estimating zonal ITLs.

17 WIND ENERGY↗