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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 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Visualization of the surface distribution of photocatalytic activity at the anatase/rutile TiO2 interface using X-ray photoelectron emission microscopy

We applied X-ray photoelectron emission microscopy (XPEEM) to visualize the surface distribution of photocatalytic activity at the anatase/rutile (A/R) interface of titanium dioxide. Acetic acid was adsorbed on the surface, and its decomposition and desorption reactions under ultraviolet light irradiation were monitored by observing C 1s spectra, enabling direct observation of the spatial distribution of photocatalytic activity. Complementary crystal structure information was obtained using spatially resolved low-energy electron diffraction, low-energy electron microscopy, X-ray absorption spectroscopy, and micro-focused Raman spectroscopy. Comparison with these structural data allowed for the evaluation of the photocatalytic activity as a function of the distance from the A/R interface. The activity is enhanced in the vicinity of the interface and gradually decreases toward both the anatase and rutile regions. These results demonstrate that XPEEM is an effective technique for spatially resolved mapping of photocatalytic activity, which has\\r\\npreviously been inaccessible using conventional characterization techniques.

25 ENERGY STORAGE↗
DOE OSTI2023

High-Order Mesh Morphing for Boundary and Interface Fitting to Implicit Geometries

Here, we propose a method that morphs high-order meshes such that their boundaries and interfaces coincide/align with implicitly defined geometries. Our focus is particularly on the case when the target surface is prescribed as the zero isocontour of a smooth discrete function. Common examples of this scenario include using level set functions to represent material interfaces in multimaterial configurations, and evolving geometries in shape and topology optimization. The proposed method formulates the mesh optimization problem as a variational minimization of the sum of a chosen mesh-quality metric using the Target-Matrix Optimization Paradigm (TMOP) and a penalty term that weakly forces the selected faces of the mesh to align with the target surface. The distinct features of the method are use of a source mesh to represent the level set function with sufficient accuracy, and adaptive strategies for setting the penalization weight and selecting the faces of the mesh to be fit to the target isocontour of the level set field. We demonstrate that the proposed method is robust for generating boundary- and interface-fitted meshes for curvilinear domains using different element types in 2D and 3D.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Constrained optimization framework for interface-aware sub-scale dynamics discrete closure model for multimaterial cells in Lagrangian cell-centered hydrodynamics

In this paper, we present the new discrete optimization-based interface-aware sub-scale dynamics (IA-SSD) closure model for multimaterial cells for Lagrangian cell-centered hydrodynamics. For the multimaterial cell, the kinematic and thermodynamic properties (e.g., velocity, density, pressure and internal energy) will typically vary between the materials. The discrete closure model is responsible for an accurate update of the thermodynamic states of the individual material components in the multimaterial cell, and for determining the nodal forces that move the vertices of the cell. The IA-SSD closure model consists of two stages — a bulk stage followed by a sub-scale stage. During the bulk stage, the total change in the volume of the cell, total force applied to the cell, and total work done on the cell are distributed between the materials to update their volume, velocity and total energy. This distribution is performed using volume fractions of the materials. During the second stage, sub-scale interactions of the materials inside the multimaterial cell are taken into account. At this stage, information about the topology of the materials inside the multimaterial cell is used, allowing the orientations of internal interfaces to be included in the model. Each material interacts in a pair-wise fashion with the materials with which it has a common boundary. The interactions are based on the solution of the acoustic Riemann problem between each pair of materials and are limited using physically justified constraints: positivity of volume, positivity of internal energy, and controlled rate of pressure relaxation. To determine the values of the limiter coefficients, a constrained-optimization framework is employed using a quadratic objective function with linear constraints. It is a first-of-its kind application of constrained optimization to develop discrete closure models in a more rigorous fashion. The pair-wise interaction between materials is essentially one dimensional in the direction that is normal to interface. Finally, for this reason, we demonstrate in this paper the performance of our new model on one dimensional numerical examples.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Dynamic stability of a crude oil/brine interface: Effect of anion type

The chemical composition of the aqueous phase plays an essential role in water-based enhanced-oil recovery processes. The aqueous phase ionic profile affects the snap-off response of a crude oil-brine system by linking it to the brine-crude oil interfacial rheology. In this work, we focus on the effect of the anion on the snap-off response. To this end, a sample of crude oil from the Minnelusa Sandstone formation in Wyoming was selected, and several aqueous solutions were prepared with salts containing sodium cation and different anions (chlorides, sulfates, and phosphates) at two ionic strength values, 0.6 M and 6 mM, as cases of high- and low-salinity water. Interfacial tension, interfacial viscoelasticity and interface stability were analyzed as functions of aging time using pendant drop, dilatational rheology, and liquid bridge techniques, respectively. Here the results show that solutions with higher ionic strength led to the formation of more rigid interfaces, i.e. higher elastic modulus, and faster formation kinetics. In the low-salinity regime, solutions with polyvalent anions produce more viscoelastic interfaces at faster rates than solutions with monovalent anions. Finally, an excellent correlation (R 2 greater than 0.97) between the relative stability of the interfacial film, predicted in liquid bridge tests, and the ratio of interfacial tension and interfacial elastic modulus was found.

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

Density estimation techniques for multiscale coupling of kinetic models of the plasma material interface

In this work we analyze two classes of Density-Estimation techniques which can be used to consistently couple different kinetic models of the plasma-material interface, intended as the region of plasma immediately interacting with the first surface layers of a material wall. In particular, we handle the general problem of interfacing a continuum multi-species Vlasov-Poisson-BGK plasma model to discrete surface erosion models. The continuum model solves for the energy-angle distributions of the particles striking the surface, which are then driving the surface response. A modification to the classical Binary-Collision Approximation (BCA) method is here utilized as a prototype discrete model of the surface, to provide boundary conditions and impurity distributions representative of the material behavior during plasma irradiation. The numerical tests revealed the superior convergence properties of Gaussian Mixture Models over Kernel Density Estimation methods, with Gaussian Mixtures and Epanechnikov-KDEs both being up to two orders of magnitude faster than Gaussian-KDEs. The methodology here presented allows a self-consistent treatment of the plasma-material interface in magnetic fusion devices, including both the near-surface plasma (plasma sheath and presheath) in magnetized conditions, and surface effects such as sputtering, back-scattering, and ion implantation. The same coupling techniques can also be utilized for other discrete material models such as Molecular Dynamics.

42 ENGINEERING↗
DOE OSTI2023

A conservative, interface-resolved, compressible framework for the modeling and simulation of liquid/gas phase change

This paper presents a method for simulating evaporation in a compressible, interface-resolved framework appropriate for modeling problems of engineering interest. In order to achieve robustness and broad applicability, the method has been designed to discretely enforce consistent mass and thermal energy transport at the phase interface, to globally conserve mass, momentum, and energy, and to be capable of modeling compressible and incompressible systems. Verification is performed via the Sod-shock test, one-dimensional heat conduction, evaporation from a planar interface, and evaporation of three-dimensional droplets. Convergence with increasing mesh resolution is demonstrated in all tested configurations, and conservation is maintained near machine precision for a translating droplet. Conservation and accurate phase change rates are preserved at the low numerical resolutions commonly encountered in engineering calculations. Following verification, the method is validated by comparison to an empirical correlation for evaporating droplets in high temperature crossflow, and the presentation concludes with the simulation of an iso-octane spray at conditions representative of gasoline direct injection. In conclusion, successful verification, validation, and demonstrated practical utility suggest the method to be an accurate, efficient, and robust approach for the study of phase change in engineering systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Evolution of the structure and chemical composition of the interface between multi-component silicate glasses and yttria-stabilized zirconia after 40,000 h exposure in air at 800 °C

The chemical and structural stability of two commercial multicomponent silicate glasses (SCN and G6) in contact with yttria-stabilized zirconia (YSZ) was investigated after exposure times of up to 40,000 h in air at 800 °C. With exposure time, interfacial layers develop at the SCN-YSZ and G6-YSZ interfaces, which were characterized in detail using both quantitative chemical analysis and atomic-resolution imaging. At the SCN-YSZ interface, a Ca-Ba-Si-O reaction phase was found to grow by diffusion control. In G6-YSZ, Raman spectroscopy and electron microscopy revealed a disorganized interfacial reaction later between G6 and YSZ, and the occurrence of cubic to tetragonal to monoclinic phase transformations in YSZ. Finally, this microstructural evolution is discussed in terms of devitrification resistance of glass and diffusion processes at interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Multi-material additive manufacturing of aluminum 6061-T6 alloy with stainless steel 304: Suppression of intermetallic compounds and interface growth mechanism

Fabricating integrated aluminum-steel structures is difficult because of metallurgical incompatibilities that promote intermetallic compound (IMC) formation at their interfaces. This work introduces a practical route for additively manufacturing 6061-T6 aluminum alloy (AA6061-T6) directly onto 304 stainless steel (SS304) using a high shear strain rate-assisted interfacial bonding mechanism. Through the friction extrusion deposition-based additive manufacturing method, both single- and multi-layer deposits of AA6061-T6 were successfully fabricated on SS304, yielding a robust hybrid multi-material structure. Comprehensive analyses of deposition quality, interface porosity, and bonding performance showed that the interface achieved a tensile strength exceeding 154 MPa under quasi-static loading. Microstructural observations revealed that the deposited aluminum layers experienced severe plastic deformation, resulting in pronounced grain refinement. Importantly, the interfacial zone was found to be free of brittle IMCs, instead containing a thin amorphous layer that evolved through a non-linear reaction-zone growth law. This solid-state additive strategy establishes a promising pathway for lightweight structural systems, nuclear energy component cladding, and multifunctional engineering components, redefining how dissimilar metals can be integrated for advanced applications.

Aluminum alloy↗
DOE OSTI2019

Recognition of a Key Anchor Residue by a Conserved Hydrophobic Pocket Ensures Subunit Interface Integrity in DNA Clamps

Sliding clamp proteins encircle duplex DNA and are involved in processive DNA replication and the DNA damage response. Clamp proteins are ring-shaped oligomers (dimers or trimers) and are loaded onto DNA by an ATP-dependent clamp loader complex that ruptures the interface between two adjacent subunits. Here we measured the solution dynamics of the human clamp protein, proliferating cell nuclear antigen, by monitoring the change in the fluorescence of a site-specifically labeled. To unravel the origins of clamp subunit interface stability, we carried out comprehensive comparative analysis of the interfaces of seven sliding clamps. Here, we used computational modeling (molecular dynamic simulations and MM/GBSA binding energy decomposition analyses) to identify conserved networks of hydrophobic residues critical for clamp stability and ring-opening dynamics. The hydrophobic network is shared among clamp proteins and exhibits a “key in a keyhole” pattern where a bulky aromatic residue from one clamp subunit is anchored into a hydrophobic pocket of the opposing subunit. Bioinformatics and dynamic network analyses showed that this oligomeric latch is conserved across DNA sliding clamps from all domains of life and dictates the dynamics of clamp opening and closing.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Interface reactions and mechanical properties of FeCrAl-coated Zircaloy-4

FeCrAl has been proposed as a coating layer to enhance accident tolerance of Zircaloy-4 fuel cladding. In this study, we systematically examined the diffusion kinetics and interface compound formation of the spray-coated FeCrAl and Zircaloy-4 substrate. After vacuum annealing at 923 K, 963 K, and 998 K for various time periods, a mixed Zr 2 Fe phase and Zr 3 Fe formed at the interface. The formation energies of these two phases were found to be 65 kJ/mol and 58 kJ/mol for Zr 2 Fe and Zr 3 Fe, respectively. Bending tests of cantilevers prepared by a focused ion beam technique showed good interface bonding between the coating layer and the substrate. Nanoindentation and micropillar compression tests in the cross-section of polished samples show different mechanical responses of each phase. The substrate exhibited the lowest hardness and most ductile deformation under compression, while interfacial Zr 2 Fe and Zr 3 Fe possessed the highest hardness and brittle deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydrogen trapping energetics at BCC iron-helium interfaces

Density functional theory (DFT) calculations have been performed to assess the trapping and segregation strength of hydrogen (H) to helium (He) interfaces in BCC (Fe) as a function of He density and surface orientation. The He density ranges from 0 to 2 He/V which corresponds to equilibrium bubbles that are expected to form in the structural components in a fusion reactor environment. The DFT calculations consist of a slab of BCC metal and an initial lattice of FCC He. Here, the report on the binding energy of H to these interfaces as well as the migration barriers into and away from the surface, which together provide information on the de-trapping energy for H at He bubbles. It was found that the binding energy of H to He-Fe interfaces decreases with increasing He density. Migration barriers are also modified due to the He density, which are sensitive to the surface orientation as well as the diffusion pathway. These results provide valuable first-principles energetics that are necessary for higher-order, mesoscale models, and provide insight into the extent to which He bubbles may trap tritium in fusion structural materials.

42 ENGINEERING↗
DOE OSTI2019

Direct observation of MgO formation at cathode electrolyte interface of a spinel MgCo 2 O 4 cathode upon electrochemical Mg removal and insertion

Identifying a Mg 2+ insertion mechanism into Mg cathode is one crucial challenge of designing Mg batteries that own comparable specific energy to the lithium ion systems. Spinel Mg cathodes are attractive candidates mainly attributed to its high intercalation voltage and theoretical capacity, however, electrochemically removing Mg from its solid structure with identified capacity dedicated to actual reversible Mg intercalation introduce complications. Work presented here applies Scanning/Transmission Electron Microscopy with Energy Loss Spectroscopy and diffraction method to investigate the cathode electrolyte interface for a spinel MgCo 2 O 4 material electrochemically cycled in the presence of a non-aqueous, low water content Mg electrolyte. Findings at an atomic scale suggest a complete de-magnesiation is occurring for thin MgCo 2 O 4 particles upon electrochemical charging, but a vast majority of MgCo 2 O 4 shows formation of an amorphous MgO layer with a thickness of similar to ~10 nm at the cathode electrolyte interface. The amorphous MgO layer is directly jointed with the crystalline MgCo 2 O 4 at the outer edge of the cathode. Formation of MgO at the cathode electrolyte interface is believed to be the detrimental factor preventing further electrochemical cell cycling of MgCo 2 O 4 . A possible reaction pathway of intercalation-initiated surface conversion is proposed to explain reversible Mg insertion with MgCo 2 O 4 .

25 ENERGY STORAGE↗
DOE OSTI2018

Evaluation of microstructure stability at the interfaces of Al-6061 welds fabricated using ultrasonic additive manufacturing

Ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing process that uses fundamental principles of ultrasonic welding and sequential layering of tapes to fabricate complex three-dimensional (3-D) components. One of the factors limiting the use of this technology is the poor tensile strength along the z-axis. Recent work has demonstrated the improvement of the z-axis properties after post-processing treatments. The abnormally high stability of the grains at the interface during post-weld heat treatments is, however, not yet well understood. In this work we use multiscale characterization to understand the stability of the grains during post-weld heat treatments. Aluminum alloy (6061) builds, fabricated using ultrasonic additive manufacturing, were post-weld heat treated at 180, 330 and 580 °C. The grains close to the tape interfaces are stable during post-weld heat treatments at high temperatures (i.e., 580 °C). This is in contrast to rapid grain growth that takes place in the bulk. Transmission electron microscopy and atom-probe tomography display a significant enrichment of oxygen and magnesium near the stable interfaces. Based on the detailed characterization, two mechanisms are proposed and evaluated: nonequilibrium nano-dispersed oxides impeding the grain growth due to grain boundary pinning, or grain boundary segregation of magnesium and oxygen reducing the grain boundary energy.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Analysis of interfaces in Bornite (Cu5FeS4) fabricated Schottky diode using impedance spectroscopy method and its photosensitive behavior

Highlights: • Impedance spectroscopy study and current-voltage analysis of Bornite fabricated Schottky diode. • Analysis of interface regions of Schottky barrier diode under dc bias voltage. • Deduction of photosensing parameters for Al/Cu{sub 5}FeS{sub 4}/FTO Schottky diode. • Discussion of charge transport mechanism by employing space charge limited current (SCLC) theory. - Abstract: In this report, we have synthesized Bornite (Cu{sub 5}FeS{sub 4}) material by hydrothermal synthesis technique. The interface characteristics of Al/Cu{sub 5}FeS{sub 4}/FTO Schottky barrier diode (SBD) are investigated by using ac impedance spectroscopy (IS) analysis (under dark condition) and dc current-voltage (I–V) measurements (under dark and light both condition). IS is a powerful tool to identify the interface regions of SBDs. Ac impedance spectra of Al/Cu{sub 5}FeS{sub 4} SBD are recorded in the frequency range 40 Hz-20 MHz during dc bias scanning from -0.6 V to 0.6 V under dark condition. The diode parameter including ideality factor and barrier height is calculated from the conventional I–V measurement based on thermionic emission (TE) theory. Space charge limited current (SCLC) theory has been employed to further exemplify the improved performance of Cu{sub 5}FeS{sub 4} based SBD, which points out that the carrier mobility is enhanced ∼2-fold after irradiation of light.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Achieving stable all-solid-state lithium-metal batteries by tuning the cathode-electrolyte interface and ionic/electronic transport within the cathode

All-solid-state batteries with sulfide electrolytes and high-nickel layered oxide cathodes attract much interest due to their high specific energy. However, their cycling performance is primarily influenced by the interface between the sulfide electrolyte and the high-Ni layered oxide particles, which requires the use of composite cathodes with high ionic and electronic conductivities to achieve a kinetically stable interface inside the cathode. Here, we apply Ti 2 O 3 particles to the high-Ni cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), where Ti 2 O 3 not only acts as an electronic conductor to provide a fast diffusion path for electrons in the composite cathode, but also absorbs the lattice oxygen released from NCM811 cathode during cycling, stabilizing the Li 6 PS 5 Cl/NCM811 interface and suppressing electrolyte oxidation. The as-modified cathode exhibits an initial specific capacity of 192 mAh g -1 and retains 166 mAh g -1 after 140 cycles at 0.1C rate with a good capacity retention of 86.5%. Furthermore, the composite cathode displays high rate capability even at 1C rate. By contrast, the unmodified Li 6 PS 5 Cl/NCM811 cathode shows poor cycling performance with only 130 mAh g -1 remaining after 130 cycles. This work provides a new direction for the design of cathodes for all-solid-state batteries that can deliver high specific energy with long cycle life.

25 ENERGY STORAGE↗
DOE OSTI2022

Genome-scale modelling of the primary-specialized metabolism interface

Environmental challenges and development require plants to reallocate resources between primary and specialized metabolites to survive. Genome-scale metabolic models, which map carbon flux through metabolic pathways, are a valuable tool in the study of tradeoffs that arise at this interface. Due to annotation gaps, models that characterize all the enzymatic steps in individual specialized pathways and their linkages to each other and to central carbon metabolism are difficult to construct. Recent studies have successfully curated subsystems of specialized metabolism and characterized the interfaces where flux is diverted to the precursors of glucosinolates, terpenes, and anthocyanins. Although advances in metabolite profiling can help to constrain models at this interface, quantitative analysis remains challenging because of the different timescales on which specialized metabolites from constitutive and reactive pathways accumulate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Role of thermo-mechanical gyrations on the α/β interface stability in a Ti6Al4V AM alloy

Fluctuating energy distributions experienced during Additive Manufacturing yield an evolution of spatial and temporal transients within a part. In general, the in-situ monitoring of these transients is near to impossible during manufacturing. In order to then gain perspective into the impact on these localized thermo-mechanical transients on the interface stability, rapid thermo-mechanical reversals with known boundary conditions are imposed on an AM Ti6Al4V alloy which resulted in a phase transformation leading to an increased β phase stability. Our goal with this study is to comprehend the kinetics of this phase transformation with concepts of stored energy due to plastic strain accumulation and diffusion kinetics. Atom Probe Tomography is employed to study the partitioning of the solute elements across the interface. As expected, the thermo-mechanically cycled samples showed a reduced Vanadium concentration across the β phase. Finally, this concentration profile across the interface, alongside a full-width-half-max analysis, provided insight on the potential phase transformation kinetics involved in the α → β transformation subject to thermo- mechanical gyrations.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Microstructure and Composition of Passivating Interfaces in Silicon Heterojunction Solar Modules Weathered in Different Climates

Sanyo/Panasonic patented silicon heterojunction with intrinsic thin layer (HIT) solar cells in the 1990's, which demonstrated world record photovoltaic (PV) efficiency around 2014 and inspired the newer generations of silicon heterojunction technology (SHJ) as well as the current world record back-contact PV cell designs. The high-quality passivation strategy, utilizing ultra-thin layers of hydrogenated amorphous silicon (a-Si:H), leads to high voltages and long carrier lifetimes, but these qualities may degrade over time as the modules operate outdoors. Here, we investigate local microstructure and composition at the interface layers of cells from HIT modules weathered in a hot, humid climate (Florida, USA) and temperate climate (Colorado, USA) for 10 years. We employ a comprehensive set of high-resolution electron microscopy imaging and spectroscopy to directly resolve structure and composition in these cells down to the nanoscale. We show features such as alignment of the In2O3 transparent conducting oxide and a-Si:H layers on the textured c-Si facets, interfacial oxidation at the a-Si:H/c-Si and In2O3/a-Si:H interfaces, and twinned c-Si resulting from epitaxial growth into the a-Si:H layer. Our results raise potential degradation mechanisms in these outdoor-weathered modules, but the root cause of electrical loss remains uncertain due to the very small changes in aged samples. This study shows that many atomic scale features at the In2O3/a-Si:H/c-Si interfaces are surprisingly robust, and the electrical losses with aging may either be attributed to other pathways or be very sensitive to the subtle chemical and microstructural features observed here.

14 SOLAR ENERGY↗