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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Monodomain Liquid‐Crystal Elastomer Lattices for Broad Strain‐Rate Mechanical Damping

Designing structures that effectively dissipate energy across a broad range of mechanical loading rates, including those from compression, shock, and vibration, poses a significant engineering challenge. In this study, liquid‐crystal elastomers (LCEs), which possess anisotropic properties due to the alignment of their polymer backbone, are explored. As a result, LCEs exhibit a soft elastic response under mechanical loading, making them ideal for energy dissipation. Advances in additive manufacturing (AM) enable simple fabrication of foamlike dissipative structures with complex lattice geometries. Herein, direct ink write 3D printing, an extrusion AM method, is used to fabricate aligned, monodomain LCE lattice structures for broad strain‐rate mechanical damping. In this work, it is shown that these structures can dissipate strain energy in quasi‐static environments, comparable to traditional elastomeric lattices, and provide improved damping under high strain‐rate drop testing due to LCE soft elasticity. Additionally, under dynamic mechanical vibration, monodomain LCE lattices enhance damping at structural natural frequencies and provide high‐frequency attenuation. Finally, in these findings, a promising method is presented for fabricating mechanical damping devices that effectively dissipate energy across a broad range of loading rates.

3D printings↗
DOE OSTI2025

Impact of the Atomic Structure at the BiVO 4 /TiO 2 Interface on the Electronic Properties and Performance of BiVO 4 /TiO 2 Photoanodes

In photoelectrochemical cells, semiconductor electrodes are usually interfaced with protection layers to extend their stability. Ideally, the protection layer should not decrease photocurrent generation. Hence, the conduction band minimum (CBM) and valence band maximum (VBM) of the protection layer should appropriately align with those of the underlying semiconductor electrode to facilitate the desired interfacial charge transfer with minimal interfacial recombination. However, predicting interfacial band alignment can be challenging, as it may vary depending on the detailed interfacial atomic structure. Investigating the effect of the atomic structure at the semiconductor/protection layer junction on the band alignment is also challenging as it requires samples with varied interfaces without altering the semiconductor and protection layers. Here, we considered TiO 2 , the most widely used material as a protection layer, interfaced with a BiVO 4 photoanode, and we fabricated two n-type BiVO 4 (010)/TiO 2 photoanodes where a thin (∼4 nm) amorphous TiO 2 layer was deposited by atomic layer deposition (ALD). While the individual BiVO 4 (010) and TiO 2 layers were identical in these two samples, we modified the interfacial atomic structure at the BiVO 4 /TiO 2 junction by changing which precursor, Ti or O, was introduced first upon deposition of TiO 2 . By experimentally and computationally investigating the differences in these two samples, we show that the band alignments between BiVO 4 and TiO 2 at the interface may not be straightforwardly predicted by the CBM and VBM of bulk BiVO 4 and TiO 2 and that interfacial atomic arrangements can have a marked impact on the electronic properties and photoelectrochemical performance of the BiVO 4 (010)/TiO 2 photoanode.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Vortex Matter in Confined Superconductors and Mesoscopic Hybrid Heterostructures. Final report

This program studied the fundamental features that underlie the behavior of hybrid ferromagnet/superconductor heterostructures both in the regime of magnetic coupling and proximity effect. In ferromagnet/superconductor hybrid structures, the source of superconducting correlations and ferromagnetism are spatially separated. Therefore, the interplay between ferromagnetism and superconductivity results in physical effects that are not easily observed in bulk superconductors and allows to tune the local superconducting and vortex properties, realizing, thus, a new class of materials. In the case of proximity effect the ferromagnet and the superconductor are in contact and leakage of superconducting pairs is allowed into the ferromagnetic layer. Typically, the decay length for the superconducting pair correlations in the ferromagnet is of the order of one nanometer due to the typically large ferromagnetic exchange field. However, a suitable magnetic structure in the ferromagnetic material can be used to align the spins of the superconducting pairs allowing much longer penetration of superconductivity in the magnetic material. These superconducting pairs with aligned spins can carry spin and provide the basis for superconducting spintronics devices. In the case of magnetic coupling the effect of a spatial inhomogeneous stray field produced by the ferromagnet substantially modifies the nucleation of the order parameter in the superconducting layer and can lead to a significant change in the local superconducting properties. Therefore, magnetically coupled planar ferromagnet-superconductor hybrid structures offer new avenues for manipulation of the superconductivity at the nanoscale and convenient means to control vortex dynamics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

DeepComplex: A Web Server of Predicting Protein Complex Structures by Deep Learning Inter-chain Contact Prediction and Distance-Based Modelling

Proteins interact to form complexes. Predicting the quaternary structure of protein complexes is useful for protein function analysis, protein engineering, and drug design. However, few user-friendly tools leveraging the latest deep learning technology for inter-chain contact prediction and the distance-based modelling to predict protein quaternary structures are available. To address this gap, we develop DeepComplex, a web server for predicting structures of dimeric protein complexes. It uses deep learning to predict inter-chain contacts in a homodimer or heterodimer. The predicted contacts are then used to construct a quaternary structure of the dimer by the distance-based modelling, which can be interactively viewed and analysed. The web server is freely accessible and requires no registration. It can be easily used by providing a job name and an email address along with the tertiary structure for one chain of a homodimer or two chains of a heterodimer. The output webpage provides the multiple sequence alignment, predicted inter-chain residue-residue contact map, and predicted quaternary structure of the dimer.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Targeted Adjusting Molecular Arrangement in Organic Solar Cells via a Universal Solid Additive

The incorporation of solid additive has been considered as an effective strategy for developing organic photovoltaics with multi-components, which is independent of dynamics, playing unique roles in morphology adjustment. However, their complex working mechanisms involving specific chemical structures are selective to material systems, hence limiting their university and flexibility in application. Herein, an inert small-molecular compound naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT) is introduced into the bulk-heterojunction blend as the solid additive, which can function with various material systems and solvents, depending on its simple π-conjugated structure and S⋯N interaction for adjusting molecular alignment. It is interesting to note that the introduced NT can not only improve device performance, but also simplify complicated pre- or post-processing methods, reduce impact from batch-to-batch differences, construct sufficient energy transfer channel as well as improve device stability. The resulting devices based on PTzBI-dF:Y6-BO system show an impressive power conversion efficiency of 17.4% with obviously enhanced T 80 lifetime of >1200 h. These findings provide useful guidelines for exploring potential universal solid additives benefitting toward commercial application.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impacts of annealing treatment on the microstructure of U-Mo monolithic fuel plates

The objective of this paper is to analyze the effect of different heat treatments on the fuel microstructure and texture in laboratory scale monolithic U-Mo fuel plates. Such analyses are relevant as they could possibly inform future fabrication methods for the optimization of microstructure and of material properties to ultimately improve fuel performance during irradiation. For this reason, detail characterization including Energy x-ray dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD) techniques were applied on U-Mo plates fabricated with different heat treatments to understand the influence of fabrication on fuel microstructure. Here, U-Mo fresh fuel specimens with or without annealing treatments (homogenization and stress release annealing) after rolling were analyzed in this work. In this study for the first time EBSD was systematically used to analyze the heat treatments influence on texture present in fresh fuel monolithic U-Mo fuel plates. Such changes were connected to other known microstructural and chemical changes. In this work minimization of molybdenum concentration variation and gamma phase decomposition of the U-Mo fuel core after homogenization was observed. Also, an increase in the interaction layer of the U-Mo fuel core with the Zr interlayer diffusion barrier was observed with the UZr 2 growing up to 1 µm in thickness. Such microstructural changes were aligned to the changes in texture and grain structure. Indeed, common texture observed in body-centered cubic (BCC) metal after cold rolling (e.g., α, ξ, γ fibers) were minimized by the annealing/homogenization process. Moreover, grain structure was influenced by the fabrication route with elongated grains formed in the rolled sample and equiaxed grains found after annealing. Such features are relevant since the formation of microstructural features formed during fuel fabrication can impact fuel performance in reactor.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Gaussian integral method for void fraction

Here, a novel method, the Gaussian Integral Method (GIM), is presented for calculating void fractions in Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) simulations. GIM is versatile and applicable to various grid types, including structured and unstructured polyhedral meshes, without requiring special boundary treatments. An optimization technique is introduced to make GIM independent of grid resolution and type. The method is validated against experimental data from a fluidized bed, demonstrating that GIM produces realistic simulations closely resembling experimental observations. Additionally, unstructured polyhedral grids using GIM outperform structured grids of equivalent resolution, yielding results more aligned with experimental data. The gradient of the void fraction is computed in the CFD solver and utilized in the DEM solver for precise estimation at particle locations. Overall, GIM provides an effective solution for void fraction calculations in particulate media simulations with complex geometries, enhancing the accuracy and applicability of CFD-DEM simulations for industrial processes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Laponite-Incorporated UiO-66-NH2-Polyethylene Oxide Composite Membranes for Protection against Chemical Warfare Agent Simulants

A strategy is developed to enhance the barrier protection of polyethylene oxide (PEO)-metal–organic framework (MOF) composite films against chemical warfare agent simulants. To achieve enhanced protection, an impermeable high-aspect-ratio filler in the form of Laponite RD (LRD) clay platelets was incorporated into a composite PEO film containing MOF UiO-66-NH 2 . The inclusion of the platelets aids in mitigating permeation of inert hydrocarbons (octane) and toxic chemicals (2-chloroethyl ethyl sulfide, 2-CEES) of dimensions/chemistry similar to prominent vesicant threats while still maintaining high water vapor transport rates (WVTR). By utilizing small-angle neutron scattering, small-angle X-ray scattering, and wide-angle X-ray scattering, the LRD platelet alignment of the films was determined, and the structure of the films was correlated with performance as a barrier material. Performance of the membranes against toxic chemical threats was assessed using permeation testing of octane and 2-CEES, a common simulant for the vesicant mustard gas, and breathability of the membranes was assessed using WVTR measurements. To assess their robustness, chemical exposure (in situ diffuse reflectance infrared Fourier transform spectroscopy) and mechanical (tensile strength) measurements were also performed. It was demonstrated that the barrier performance of the film upon inclusion of the LRD platelets exceeds that of other MOF-polymer composites found in the literature and that this approach establishes a new path for improving permselective materials for chemical protection applications.

36 MATERIALS SCIENCE↗
DOE OSTI2026

High-throughput computation of electric polarization in solids via Berry flux diagonalization

Electric polarization in the absence of an externally applied electric field is a key property of polar materials, but the standard interpolation-based ab initio approach to compute polarization differences within the modern theory of polarization presents challenges for automated high-throughput calculations. Berry flux diagonalization [J. Bonini et al., Phys. Rev. B 102, 045141 (2020)] has been proposed as an efficient and reliable alternative, though it has yet to be widely deployed. Here, we assess Berry flux diagonalization using ab initio calculations of a large set of materials, introducing and validating heuristics that ensure branch alignment with a minimal number of intermediate interpolated structures. Our automated implementation of Berry flux diagonalization succeeds in cases where prior interpolation-based workflows fail due to band-gap closures or branch ambiguities. Benchmarking with ab initio calculations of 176 candidate ferroelectrics, we demonstrate the efficacy of the approach on a broad range of insulating materials and obtain accurate effective polarization values with fewer interpolated structures than prior automated interpolation-based workflows. Our real-space heuristics that can predict gauge stability a priori from ionic displacements enable a general automated framework for reliable polarization calculations and efficient high-throughput screening of chemically and structurally diverse polar insulators. These results establish Berry flux diagonalization as a robust and efficient method to compute the effective polarization of solids and to accelerate the data-driven discovery of functional polar materials.

Poteshman, Abigail N. [University of Chicago, IL (↗
DOE OSTI2025

Fusion and fission of particle-like chiral nematic vortex knots

Vortex knots have been seen decaying in many physical systems. Here we describe topologically protected vortex knots, which remain stable and undergo fusion and fission and conserve a topological invariant. The host medium, a chiral nematic liquid crystal, exhibits intrinsic chirality of molecular alignment, whereas cores of the vortex lines are structurally achiral regions in which a molecular twist cannot be defined. We can reversibly switch between fusion and fission of these vortex knots by applying electric pulses. This reveals the physical embodiments of concepts in knot theory, such as connected sums of knots and band surgeries. Our findings demonstrate the interplay of chirality effects at hierarchical levels from constituent molecules to the host medium and the energetically stable chiral vortex knots. This emergent physical behaviour may enable applications in electro-optics and photonics in which such fusion and fission processes of vortex knots can be used for controlling light.

Applied mathematics↗
DOE OSTI2024

Sheath constraints on turbulent magnetised plasmas

Abstract A solid target in contact with a plasma charges (negatively) to reflect the more mobile species (electrons) and thus keep the bulk plasma quasineutral. To shield the bulk plasma from the charged target, there is an oppositely (positively) charged sheath with a sharp electrostatic potential variation on the Debye length scale λ D . In magnetised plasmas where the magnetic field is inclined at an oblique angle α with the target, some of the sheath potential variation occurs also on the ion sound gyroradius length scale ρ S cos ⁡ α , caused by finite ion gyro-orbit distortion and losses. We consider a collisionless and steady-state magnetised plasma sheath whose thickness l ms ∼ max ( λ D , ρ S cos ⁡ α ) is smaller than the characteristic length scale L of spatial fluctuations in the bulk plasma, such that the limit l ms / L → 0 is appropriate. Spatial structures are assumed to be magnetic field-aligned. In the case of small magnetic field angle α ∼ δ ≡ ρ S / L ≪ 1 , electric fields tangential to the target transport ions towards the target via E × B drifts at a rate comparable to the one from parallel streaming. A generalised form of the kinetic Bohm–Chodura criterion at the sheath entrance is derived by requiring that the sheath electric field have a monotonic spatial decay far from the target. The criterion depends on tangential gradients of potential and ion distribution function, with additional nontrivial conditions.

kinetic Bohm–Chodura condition↗
DOE OSTI2020

Chaperone-tip adhesin complex is vital for synergistic activation of CFA/I fimbriae biogenesis

Colonization factor CFA/I defines the major adhesive fimbriae of enterotoxigenic Escherichia coli and mediates bacterial attachment to host intestinal epithelial cells. The CFA/I fimbria consists of a tip-localized minor adhesive subunit, CfaE, and thousands of copies of the major subunit CfaB polymerized into an ordered helical rod. Biosynthesis of CFA/I fimbriae requires the assistance of the periplasmic chaperone CfaA and outer membrane usher CfaC. Although the CfaE subunit is proposed to initiate the assembly of CFA/I fimbriae, how it performs this function remains elusive. Here, we report the establishment of an in vitro assay for CFA/I fimbria assembly and show that stabilized CfaA-CfaB and CfaA-CfaE binary complexes together with CfaC are sufficient to drive fimbria formation. The presence of both CfaA-CfaE and CfaC accelerates fimbria formation, while the absence of either component leads to linearized CfaB polymers in vitro. We further report the crystal structure of the stabilized CfaA-CfaE complex, revealing features unique for biogenesis of Class 5 fimbriae.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Oxides related to cadmium telluride solar cells

Polycrystalline cadmium telluride (CdTe) is a leading material in photovoltaic technology due to its high absorption coefficient and near-optimum bandgap of 1.44 eV. It is known that CdTe film processing can promote surface oxidation depending on the growth environment and upon exposure to different oxidation conditions. For example, CdTeO3 forms when the CdTe film is treated in heated dry air, while in humid air, CdTe2O5 is detected. These oxides feature tellurium in the oxidation state +4 compared to the +2 state in CdTe. Other possible relevant oxides are CdO, TeO2, and TeO3. Using hybrid density functional calculations, we studied the electronic structure of these oxide materials and their band alignment to CdTe, which are essential parameters in the characterization of the interfaces at grain boundaries. The goal is to understand their stability and possible effects on passivating grain boundaries. The results are compared to the available experimental data.

14 SOLAR ENERGY↗
DOE OSTI2021

Structural tuning of nonlinear terahertz metamaterials using broadside coupled split ring resonators

We present an experimental and numerical study of a terahertz metamaterial with a nonlinear response that is controllable via the relative structural arrangement of two stacked split ring resonator arrays. The first array is fabricated on an n-doped GaAs substrate, and the second array is fabricated vertically above the first using a polyimide spacer layer. Due to GaAs carrier dynamics, the on-resonance terahertz transmission at 0.4 THz varies in a nonlinear manner with incident terahertz power. The second resonator layer dampens this nonlinear response. In samples where the two layers are aligned, the resonance disappears, and the total nonlinear modulation of the on-resonance transmission decreases. The nonlinear modulation is restored in samples where an alignment offset is imposed between the two resonator arrays. Structurally tunable metamaterials and metasurfaces can therefore act as a design template for tunable nonlinear THz devices by controlling the coupling of confined electric fields to nonlinear phenomena in a complex material substrate or inclusion.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Magnetic structure and resistivity minimum in GdCuAs 2

The electrical resistivity of GdCuAs 2 single crystals exhibits an anomalous Kondo-like resistivity minimum above the antiferromagnetic ordering temperature T N 1 approximate to 10.6 K, which is unusual for a highly localized 4f-moment (Gd 3+ ) system. Using x-ray resonant magnetic scattering, we determined the magnetic structure of GdCuAs 2 , where Gd moments are antiferromagnetically aligned along the crystallographic a axis and in the (+ + --) arrangement in the c direction and ferromagnetically arranged in the b direction. The antiferromagnetic order appears first at q = (δ, 0, 0.5) below 10 K, with an incommensurate modulation along the a axis and locks into a commensurate position at q = (1/3, 0, 0.5) below T N 2 approximate to 6 K. Our high-resolution x-ray diffraction measurements show a two-peak structure at Q = (2, 0, 6) above the resistivity minimum, suggesting a lower-symmetry crystal structure than the reported tetragonal structure, and the Q = (2, 0, 6) peak becomes a sharp one-peak structure below the resistivity minimum, implying a magnetoelastic coupling above T N . In conclusion, our findings suggest a complex interplay between the crystal structure and antiferromagnetic structure through a magnetoelastic coupling, associated with the anomalous resistivity minimum above T N 1 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Vapor-to-glass preparation of biaxially aligned organic semiconductors

Physical vapor deposition (PVD) provides a route to prepare highly stable and anisotropic organic glasses that are utilized in multi-layer structures such as organic light-emitting devices. While previous work has demonstrated that anisotropic glasses with uniaxial symmetry can be prepared by PVD, here, we prepare biaxially aligned glasses in which molecular orientation has a preferred in-plane direction. With the collective effect of the surface equilibration mechanism and template growth on an aligned substrate, macroscopic biaxial alignment is achieved in depositions as much as 180 K below the clearing point TLC−iso (and 50 K below the glass transition temperature Tg) with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The preparation of biaxially aligned organic semiconductors adds a new dimension of structural control for vapor-deposited glasses and may enable polarized emission and in-plane control of charge mobility.

Chemistry↗
DOE OSTI2021

Elementary Composite Binary and Grain Alignment Locked in Dust Growth

Abstract Planets are known to grow out of a star-encircling disk of the gas and dust inherited from an interstellar cloud; their formation is thought to begin with coagulation of submicron dust grains into aggregates, the first foundational stage of planet formation. However, with nanoscale and submicron solids unobservable directly in the interstellar medium (ISM) and protoplanetary disks, how dust grains grow is unclear, as are the morphology and structure of interstellar grains and the whereabouts and form of “missing iron.” Here we show an elementary composite binary in 3D sub-10 nm detail—and the alignments of its two subunits and nanoinclusions and a population of elongated composite grains locked in a primitive cosmic dust particle—noninvasively uncovered with phase-contrast X-ray nanotomography. The binary comprises a pair of oblate, quasi-spheroidal grains whose alignment and shape meet the astrophysical constraints on polarizing interstellar grains. Each member of the pair contains a high-density core of octahedral nanocrystals whose twin relationship is consistent with the magnetite’s diagnostic property at low temperatures, with a mantle exhibiting nanoscale heterogeneities, rounded edges, and pitted surfaces. This elongated binary evidently formed from an axially aligned collision of the two similar composite grains whose core–mantle structure and density gradients are consistent with interstellar processes and astronomical evidence for differential depletion. Our findings suggest that the ISM is threaded with dust grains containing preferentially oriented iron-rich magnetic nanocrystals that hold answers to astronomical problems from dust evolution, grain alignment, and the structure of magnetic fields to planetesimal growth.

Hu, Z. W. (ORCID:0000000278648830)↗
DOE OSTI2024

Filamentary Dust Polarization and the Morphology of Neutral Hydrogen Structures

Filamentary structures in neutral hydrogen (H$\tiny{I}$) emission are well aligned with the interstellar magnetic field, so H$\tiny{I}$ emission morphology can be used to construct templates that strongly correlate with measurements of polarized thermal dust emission. We explore how the quantification of filament morphology affects this correlation. We introduce a new implementation of the Rolling Hough Transform (RHT) using spherical harmonic convolutions, which enables efficient quantification of filamentary structure on the sphere. We use this Spherical RHT algorithm along with a Hessian-based method to construct H$\tiny{I}$-based polarization templates. We discuss improvements to each algorithm relative to similar implementations in the literature and compare their outputs. By exploring the parameter space of filament morphologies with the Spherical RHT, we find that the most informative H$\tiny{I}$ structures for modeling the magnetic field structure are the thinnest resolved filaments. For this reason, we find a ~10% enhancement in the B-mode correlation with polarized dust emission with higher-resolution H$\tiny{I}$ observations. We demonstrate that certain interstellar morphologies can produce parity-violating signatures, i.e., nonzero TB and EB, even under the assumption that filaments are locally aligned with the magnetic field. Finally, we demonstrate that B modes from interstellar dust filaments are mostly affected by the topology of the filaments with respect to one another and their relative polarized intensities, whereas E modes are mostly sensitive to the shapes of individual filaments.

79 ASTRONOMY AND ASTROPHYSICS↗