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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Ionic Associations and Hydration in the Electrical Double Layer of Water-in-Salt Electrolytes

Water-in-Salt-Electrolytes (WiSEs) are an exciting class of concentrated electrolytes finding applications in energy storage devices because of their expanded electrochemical stability window, good conductivity and cation transference number, and fire-extinguishing properties. These distinct properties are thought to originate from the presence of an anion-dominated ionic network and interpenetrating water channels for cation transport, which indicates that associations in WiSEs are crucial to understanding their properties. Currently, associations have mainly been investigated in the bulk, while little attention has been given to the electrolyte structure near electrified interfaces. Here, we develop a theory for the electrical double layer (EDL) of WiSEs, where we consistently account for the thermoreversible associations of species into Cayley tree aggregates. The theory predicts an asymmetric structure of the EDL. At negative voltages, hydrated Li + dominates, and cluster aggregation is initially slightly enhanced before disintegration at larger voltages. At positive voltages, when compared to the bulk, clusters are strictly diminished. Performing atomistic molecular dynamics (MD) simulations of the EDL of WiSE provides EDL data for validation and bulk data for parametrization of our theory. Validating the predictions of our theory against MD showed good qualitative agreement. Furthermore, we performed electrochemical impedance measurements to determine the differential capacitance of the studied LiTFSI WiSE and also found reasonable agreement with our theory. Overall, the developed approach can be used to investigate ionic aggregation and solvation effects in the EDL, which, among other properties, can be used to understand the precursors for solid-electrolyte interphase formation.

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

SPISEA: A Python-based Simple Stellar Population Synthesis Code for Star Clusters

We present Stellar Population Interface for Stellar Evolution and Atmospheres (SPISEA), an open-source Python package that simulates simple stellar populations. The strength of SPISEA is its modular interface which offers the user control of 13 input properties including (but not limited to) the initial mass function, stellar multiplicity, extinction law, and the metallicity-dependent stellar evolution and atmosphere model grids used. The user also has control over the initial–final mass relation in order to produce compact stellar remnants (black holes, neutron stars, and white dwarfs). We demonstrate several outputs produced by the code, including color–magnitude diagrams, HR-diagrams, luminosity functions, and mass functions. SPISEA is object-oriented and extensible, and we welcome contributions from the community. The code and documentation are available on GitHub (https://github.com/astropy/SPISEA) and ReadtheDocs (https://spisea.readthedocs.io/en/latest/), respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Reflection and refraction of directrons at the interface

Reflection and refraction are ubiquitous phenomena with extensive applications, yet minimizing energy loss and information distortion during these processes remains a significant challenge. This study examines the behavior of structurally stable solitons, known as directrons, in nematic liquid crystals interacting with an interface where the director field orientation changes, despite identical physical properties, external potentials, and boundary anchoring in the two regions. During reflection and refraction, the directrons maintain nearly constant structure and velocity, ensuring energy conservation and information integrity. Microscopic analyses of the director field and macroscopic evaluations of effective potential are employed to elucidate the dependence of reflection and refraction probabilities on the directron’s incident angle and the orientation difference across the interface. The findings provide valuable insights into the dynamics of solitary waves in structured liquid crystal systems, offering significant implications for the development of tunable photonic devices, reconfigurable optical systems, and nanoscale material engineering.

Science & Technology - Other Topics↗
DOE OSTI2023

Tuning of the magnetotransport properties of a spin-polarized 2D electron system using visible light

We report on the effects of visible light on the low temperature electronic properties of the spin-polarized two dimensional electron system (2DES) formed at the interfaces between LaAlO 3 , EuTiO 3 and (001) SrTiO 3 . A strong, persistent modulation of both longitudinal and transverse conductivity was obtained using light emitting diodes (LEDs) with emissions at different wavelengths in the visible spectrum range. In particular, Hall effect data show that visible light induces a non-volatile electron filling of bands with mainly 3 dxz,yz character, and at the same time an enhancement of the anomalous Hall effect associated to the magnetic properties of the system. Accordingly, a suppression of the weak-anti localization corrections to the magneto-conductance is found, which correlates with an enhancement of the spin-polarization and of the ferromagnetic character of 2DES. The results establish the LED-induced photo-doping as a viable route for the control of the ground state properties of artificial spin-polarized oxide 2DES.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Sizing of discontinuous natural fibers: Effect of sizing approach and sizing concentration on composite properties

Natural fiber reinforced composites (NFRCs) are gaining attention in automotive applications as an alternative to glass fiber composites due to their lightweight and renewable sourcing. However, the inherent hydrophilicity of natural fibers leads to poor compatibility with hydrophobic polymers which adversely affects the mechanical properties of the composites and can limit their application to non-structural parts. Sizing is a common approach used for synthetic fibers to improve the interface between fiber and matrix. However, there is limited study on the sizing of natural fibers, and hence the focus of this work. Here, in this study, two different approaches to sizing discontinuous coir fibers were investigated, namely; (1) ex-situ sizing and (2) in-situ sizing. A commercial polypropylene (PP) based sizing agent was used and the effects of varying sizing solution concentrations (1.5, 2.5, and 3.5 wt%) on the properties of the composites was studied. Results showed that composites prepared via the in-situ sizing process had better fiber–matrix adhesion and improved tensile properties compared to ex-situ sized composites. On studying the effect of different sizing concentrations on composite properties, we found that the tensile strength of the composites increased (by ∼ 42 %) up to 2.5 wt% sizing concentration (in solution) and then decreased. However, the impact strength decreased significantly on increasing the sizing content beyond 1.5 wt% (by ∼ 40 %). Additionally, the study was further extended to investigate the effect of sizing on different NFRCs (coir, banana, and cottonized hemp fiber) where effectiveness of sizing was found to be influenced by the fiber surface morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Near-field infrared imaging of polar domain walls in Ni 3 TeO 6

Domain walls are leading platforms for the development of ultra-low power switching and memory devices due to their potential to be moved, created, and erased in real time and to mitigate heat flux. Interface vs wavelength size effects unfortunately preclude the measurement of phonons by traditional spectroscopic techniques, so it has been challenging to unravel the primary excitations of the lattice and the symmetries that they represent across these functional interfaces. In this work, we employ synchrotron-based near-field infrared nanospectroscopy to image polar domain walls in multiferroic Ni 3 TeO 6 . This is a unique platform because, in addition to hosting polar and chiral domains that are interlocked with one another, Ni 3 TeO 6 displays both charged and neutral interfaces depending upon the direction allowing the development of structure–property relations. From a local structure and a strain point of view, we find charged walls that are twice as wide as neutral walls as well as strong frequency shifts of vibrational modes across the charged walls. The near-field amplitude drops across the walls as well. We discuss these trends in terms of polarization and chirality as well as phonon lifetimes at functional interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A computational pipeline to generate a synthetic dataset of metal ion sorption to oxides for AI/ML exploration

The charged mineral/electrolyte interfaces are ubiquitous in the surface and subsurface–including the surroundings of the geological disposal sites for radioactive waste. Therefore, understanding how ions interact with charged surfaces is critically important for predicting radionuclide mobility in the case of waste leakage. At present, the Surface Complexation Models (SCMs) are the most successful thermodynamic frameworks to describe ion retention by mineral surfaces. SCMs are interfacial speciation models that account for the effect of the electric field generated by charged surfaces on sorption equilibria. These models have been successfully used to analyze and interpret a broad range of experimental observations including potentiometric and electrokinetic titrations or spectroscopy. Unfortunately, many of the current procedures to solve and fit SCM to experimental data are not optimal, which leads to a non-transferable or non-unique description of interfacial electrostatics and consequently of the strength and extent of ion retention by mineral surfaces. Recent developments in Artificial Intelligence (AI) offer a new avenue to replace SCM solvers and fitting algorithms with trained AI surrogates. Unfortunately, there is a lack of a standardized dataset covering a wide range of SCM parameter values available for AI exploration and training–a gap filled by this study. Here, we described the computational pipeline to generate synthetic SCM data and discussed approaches to transform this dataset into AI-learnable input. First, we used this pipeline to generate a synthetic dataset of electrostatic properties for a broad range of the prototypical oxide/electrolyte interfaces. The next step is to extend this dataset to include complex radionuclide sorption and complexation, and finally, to provide trained AI architectures able to infer SCMs parameter values rapidly from experimental data. Here, we illustrated the AI-surrogate development using the ensemble learning algorithms, such as Random Forest and Gradient Boosting. These surrogate models allow a rapid prediction of the SCM model parameters, do not rely on an initial guess, and guarantee convergence in all cases.

Li, Chunhui↗
DOE OSTI2019

Effect of Anisotropy on Microstructures and Mechanical Properties of Rolled Ti/Al/Mg/Al/Ti Laminates

TA2/5052Al/AZ31/5052Al/TA2 five-ply laminates were fabricated by hot rolling, and the effect of anisotropy on their microstructures and mechanical properties was studied. After rolling, the Mg/Al and Al/Ti interfaces were both closely connected, but the interfacial shapes were totally different. For the Mg layer microstructures in the middle area, regardless of the direction, dynamic recrystallized (DRXed) grains appeared around the deformation bands. However, twins and a shear zone appeared in the RD sample; the twins decreased in the sample along the 45° angle, and no twins appeared in the TD sample. The Ti layer showed equiaxed grains in different directions, which were attributed to the ability of Ti alloy to anti-deform. The tensile testing results showed that the fracture of the Ti/Al/Mg/Al/Ti laminates can be divided into four stages. The laminate had an ultimate tensile strength of 434 MPa and excellent elongation along the rolling direction (RD), which were attributed to its DRXed grains and twins. In conclusion, the laminates had significant anisotropy due to the presence of Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Inertial dynamics of an interface with interfacial mass flux: Stability and flow fields’ structure, inertial stabilization mechanism, degeneracy of Landau’s solution, effect of energy fluctuations, and chemistry-induced instabilities

This work focuses on the long-standing problem of inertial dynamics of an interface with interfacial mass flux and reports new mechanisms for the interface stabilization and destabilization. The interface is a phase boundary separating fluids of different densities and having interfacial mass flux. To analyze the interface dynamics from a far field, we develop and apply the general matrix method to rigorously solve the boundary value problem involving the governing equations in the fluid bulk and the boundary conditions at the interface and at the outside boundaries of the domain. We find the fundamental solutions for the linearized system of equations and analyze the interplay of interface stability with flow fields’ structure by directly linking rigorous mathematical attributes to physical observables. We find that the interface is stable when the dynamics conserves the fluxes of mass, momentum, and energy; the stabilization is due to an inertial mechanism causing small oscillations of the interface velocity. In the classic Landau’s dynamics, the postulate of perfect constancy of the interface velocity leads to the development of Landau–Darrieus instability. This destabilization is also linked to the imbalance of the perturbed energy at the interface. The classic Landau’s solution is found to have degeneracy; lifting of the degeneracy may lead to singularity and self-similar dynamics. Our results compare well with traditional theories of combustion and propose new experiments to study the dynamics of the interface and the flow fields in combustible systems. We further conduct reactive molecular dynamics simulations to elucidate the complexity of chemical processes, to study the destabilizing effect of energy fluctuations on the interface stability, and to illustrate the chemistry-induced instabilities. In summary, we identify the extreme sensitivity of the interface dynamics to the interfacial boundary conditions, including the formal properties of fundamental solutions and the qualitative and quantitative properties of the flow fields. This provides new opportunities for studies, diagnostics, and control of multiphase flows in a broad range of processes in nature and technology.

42 ENGINEERING↗
DOE OSTI2019

The Hot Bending and Diffusion Bonding of TiAl-Based Alloy for Corrugated-Core Sandwich Structure

The multi-layer structure of TiAl-based alloys can meet the demand of having lightweight and high-strength properties at elevated temperature. In this paper, the corrugated-core sandwich structure of a TiAl-based alloy was fabricated by the hot bending/diffusion bonding process. In order to fabricate this structure, the high-temperature tensile property, hot bending behavior, and vacuum diffusion bonding of a Ti-47.5Al-Cr-V alloy were investigated. The flow behavior was evaluated by uniaxial tensile experiment, and the results showed that the alloy exhibited good plasticity at the given conditions, and the maximum elongation reached 200% at 1000 °C at strain rate of 3 × 10{sup −4} s{sup −1}. The bending experiments were also performed at temperatures of 950, 1000, and 1050 °C with fillet radii of R = 0, 0.5, and 1 mm, respectively. No micro-/macro-defects developed. The vacuum diffusion bonding of this alloy was also carried out, and the shear bonding strength of bonding joints was measured at room temperature. The maximum shear strength was 398 MPa, and the joint was obtained at 1000 °C/30 MPa/3 h. Combining the bonding interface with the shear strength of different joints, the appropriate bonding pressure and bonding time for diffusion bonding of the TiAl alloy at 1000 °C were 20 MPa and 2 h, respectively. Then, the forming process of the corrugated-core sheet was conducted at 1000 °C with a fillet radius of 1 mm. Finally, the corrugated-core sandwich structure was manufactured under vacuum atmosphere, and the mechanical properties and the interface microstructure were investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effect of an electric field on the structural and optical properties of fluorinated freely suspended smectic films

Within the framework of the generalized mean-field model that takes into account the anisotropic interactions between the nearest neighbors of molecules forming freely suspended smectic films (FSSFs) and the stabilizing effects of the smectic-A (SmA)–air interface, a numerical study was performed of the structural, thermodynamic, and optical properties of these systems in the process of their layer-by-layer thinning. The results of calculating the disjoining pressure P, the average thickness of the smectic layers L, and the reflectivity index R of a FSSF formed by 5-n-alkyl-2-(4-n-(perfluoroalkyl-methylene oxide)-pentyl) (H10F5MOPP) molecules showed that these values undergo precipitous changes in the process of layer-bylayer thinning of the film. Calculations of R(T) as a function of temperature T exceeding the phase transition temperature of SmA into an isotropic state in the bulk of the liquid crystal material are in good agreement with the experimentally obtained data for the reflectivity of the FSSF formed by H10F5MOPP molecules.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Role of Dynamic Polarization Interactions in the Electrical Double Layer at Calcite (104) Interfaces with Aqueous Solutions

Reactions at mineral interfaces with aqueous solutions control many geochemical and biogeochemical processes in the Earth’s critical zone. At the molecular level, insights into important properties such as the structure of the electrical double layer (EDL) at specific mineral interfaces continue to improve due to the increasing fidelity of laboratory instrumentation and computational approaches. However, molecular simulation approaches suffer from limited reach into relevant scales of time, length, and system complexity. To span this gap, a novel hybrid approach that couples first principle plane-wave density functional theory (DFT) with classical DFT (cDFT) is demonstrated and applied to calcite (104) interfaces with various electrolytes. In this approach, a region of interest described using DFT interacts with the surrounding medium described using cDFT to arrive at a self-consistent ground state. Benchmarking against experimental observations and entirely first principle DFT simulations demonstrates that this hybrid model efficiently encompasses the key short-range and collective interactions in the EDL. Simulations of calcite (104)/solution interfaces reveal the key static and dynamic polarization interactions that give rise to structuring of ions and water. Ion hydration interactions have the strongest effect on the depth of the first minimum in the density distribution of counterions at the surface, and the position and width of the first density peak is largely determined by the strength of ion-correlation forces. Finer details of ion distributions are controlled by mutual polarization of the calcite surface and interfacial electrolyte. Finally, this new ability to efficiently and rigorously predict EDL structure at mineral surfaces in contact with complex solutions paves the way to accurately modeling sorption, nucleation, dissolution, and growth in realistic systems.

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

Ensemble Kalman inversion of induced polarization data

SUMMARY This paper explores the applicability of ensemble Kalman inversion (EKI) with level-set parametrization for solving geophysical inverse problems. In particular, we focus on its extension to induced polarization (IP) data with uncertainty quantification. IP data may provide rich information on characteristics of geological materials due to its sensitivity to characteristics of the pore–grain interface. In many IP studies, different geological units are juxtaposed and the goal is to delineate these units and obtain estimates of unit properties with uncertainty bounds. Conventional inversion of IP data does not resolve well sharp interfaces and tends to reduce and smooth resistivity variations, while not readily providing uncertainty estimates. Recently, it has been shown for DC resistivity that EKI is an efficient solver for inverse problems which provides uncertainty quantification, and its combination with level set parametrization can delineate arbitrary interfaces well. In this contribution, we demonstrate the extension of EKI to IP data using a sequential approach, where the mean field obtained from DC resistivity inversion is used as input for a separate phase angle inversion. We illustrate our workflow using a series of synthetic and field examples. Variations with uncertainty bounds in both DC resistivity and phase angles are recovered by EKI, which provides useful information for hydrogeological site characterization. Although phase angles are less well-resolved than DC resistivity, partly due to their smaller range and higher percentage data errors, it complements DC resistivity for site characterization. Overall, EKI with level set parametrization provides a practical approach forward for efficient hydrogeophysical imaging under uncertainty.

Geochemistry & Geophysics↗
DOE OSTI2017

Characterization of the liquid Li-solid Mo (1 1 0) interface from classical molecular dynamics for plasma-facing applications

An understanding of the wetting properties and a characterization of theinterface between liquid lithium (Li) and solid molybdenum (Mo) are relevant to assessing the efficacy of Li as a plasma-facing component in fusion reactors. Here, a new second-nearest neighbor modified embedded-atom method (2NN MEAM) force eld is parameterized to describe the interactions between Li and Mo. The new force eld reproduces several benchmark properties obtained from first-principles quantum mechanics simulations, including binding curves for Li at three different adsorption sites and the corresponding forces on Li atoms adsorbed on the Mo (110) surface. This force field is then used to study the wetting of liquid Li on the (110) surface of Mo and to examine the Li-Mo interface using molecular dynamics simulations. From droplet simulations, we nd that liquid Li tends to completely wet the perfect Mo (110) surface, in contradiction with previous experimental measurements that found non-zero contact angles for liquid Li on a Mo substrate. However, these experiments were not carried out under ultra-high vacuum conditions or with a perfect (110) Mo surface, suggesting that the presence of impurities, such as oxygen, and surface structure play a crucial role in this wetting process. From thin- lm simulations, it is observed that the first layer of Li on the Mo (110) surface has many solid-like properties such as a low mobility and a larger degree of ordering when compared to layers further away from the surface, even at temperatures well above the bulk melting temperature of Li. Our findings are consistent with temperature-programmed desorption experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2010

Material Properties of Three Candidate Elastomers for Space Seals Applications

A next-generation docking system is being developed by the National Aeronautics and Space Administration (NASA) to support Constellation Space Exploration Missions to low Earth orbit (LEO), to the Moon, and to Mars. A number of investigations were carried out to quantify the properties of candidate elastomer materials for use in the main interface seal of the Low Impact Docking System (LIDS). This seal forms the gas pressure seal between two mating spacecraft. Three candidate silicone elastomer compounds were examined: Esterline ELA-SA-401, Parker Hannifin S0383-70, and Parker Hannifin S0899-50. All three materials were characterized as low-outgassing compounds, per ASTM E595, so as to minimize the contamination of optical and solar array systems. Important seal properties such as outgas levels, durometer, tensile strength, elongation to failure, glass transition temperature, permeability, compression set, Yeoh strain energy coefficients, coefficients of friction, coefficients of thermal expansion, thermal conductivity and diffusivity were measured and are reported herein.

Bastrzyk, Marta B.↗
DOE OSTI2018

Creation And Ordering Of Oxygen Vacancies At WO3-d And Perovskite Interfaces

Changes in structure and composition resulting from oxygen deficiency can strongly impact the physical and chemical properties of transition metal oxides. However, it is extremely difficult to accurately characterize the oxygen deficiency levels and pinpoint how these materials properties change in response. In this paper, the effects of substrate strain and oxidizing power on the creation and distribution of oxygen defects in WO3 thin films are investigated in detail. An 18O2 isotope labeled time-of-flight secondary ion mass spectrometry (ToF-SIMS) study reveals that WO3-films grown on STO display a significantly larger oxygen vacancy gradient along the growth direction. This result is corroborated by scanning transmission electron microscopy (STEM) images which reveal a large number of defects present close to the interface to accommodate interfacial strain, leading to ordering of oxygen vacancies and formation of semi-aligned Magnéli phases. The strain is gradually released and tetragonal phase with much better crystallinity is observed at the film/vacuum interface. The changes in structure resulting from oxygen defect creation are shown to have a direct impact on the electronic and optical properties of the films.

Zhang, Kelvin H.↗
DOE OSTI2017

Computationally guided discovery of thermoelectric materials

The potential for advances in thermoelectric materials, and thus solid-state refrigeration and power generation, is immense. Progress so far has been limited by both the breadth and diversity of the chemical space and the serial nature of experimental work. In this Review, we discuss how recent computational advances are revolutionizing our ability to predict electron and phonon transport and scattering, as well as materials dopability, and we examine efficient approaches to calculating critical transport properties across large chemical spaces. When coupled with experimental feedback, these high-throughput approaches can stimulate the discovery of new classes of thermoelectric materials. Within smaller materials subsets, computations can guide the optimal chemical and structural tailoring to enhance materials performance and provide insight into the underlying transport physics. Beyond perfect materials, computations can be used for the rational design of structural and chemical modifications (such as defects, interfaces, dopants and alloys) to provide additional control on transport properties to optimize performance. Through computational predictions for both materials searches and design, a new paradigm in thermoelectric materials discovery is emerging.

36 MATERIALS SCIENCE↗