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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Can Mineral Growth by Oriented Attachment Lead to Incorporation of Uranium(VI) into the Structure of Goethite?

Oriented aggregation (OA), whereby crystals grow by successive attachment of precursor nanoparticles that are crystallographically co-aligned with the growing crystal, is a fundamental process by which many low solubility phases and minerals reach maturity in aqueous solution. Here, we investigated whether U(VI) can be incorporated into the structure of goethite that grows by OA. Wet chemical analysis and acid treatments showed that the additions of U(VI) early in the OA process hindered crystallization and increased the recalcitrant fraction of sorbed U(VI) relative to later addition of U(VI). Over time, however, the recalcitrant fraction of U(VI) decreased and converged to similar values for both early and late additions of U(VI). Electron microscopy indicated a portion of the acid resistant sorbed U(VI) was likely associated with grain boundaries between aggregating particles, not nanopores; and that these features were annealed out with increasing reaction time. Further, time elapsed imaging of U atom diffusion, that was stimulated by the electron beam, indicated that most sorbed U(VI) was not incorporated into the structure of goethite. This was confirmed and more rigorously quantified by ab initio molecular dynamics informed extended X-ray absorption fine structure spectra which indicated that only up to 5% of the recalcitrant U(VI) might be incorporated with an upper solubility limit of only U/Fe ~ 0.02 atom % in goethite where U(VI) was added early in the process. We conclude that most of the recalcitrant U(VI) is simply strongly adsorbed to the surface and that it is the uranyl oxygens that both inhibit crystallization of goethite as well as incorporation of U into the structure of goethite.

Soltis, Jennifer A.↗
DOE OSTI2019

Oriented porous LLZO 3D structures obtained by freeze casting for battery applications

All solid-state lithium batteries are, potentially, higher energy density and safer alternatives to conventional lithium-ion batteries (LIBs). These are particularly attractive characteristics for large-scale applications such as electric vehicles and grid energy storage systems. However, the thin film deposition techniques used to make current devices are not readily scalable, and result in low areal capacities, which translate to low practical energy densities. To overcome these deficiencies, it is necessary to design thicker electrodes similar to what are used in LIBs (30–100 μm), in which the active material is composited with an ionic conductor and an electronically conducting additive, to overcome transport limitations. In this paper, we propose a method for making such an electrode, starting with a porous scaffold, i.e. Li 7 La 3 Zr 2 O 12 (LLZO), made by freeze casting, which is then infiltrated with the active material LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC-622) and other components. The freeze casting technique results in the formation of oriented channels with low tortuosity, which run roughly parallel to the direction of the current. The scaffolds were characterized with synchrotron X-ray micro-tomography for structural analysis, as well as synchrotron X-ray fluorescence to map the elemental distribution in the infiltrated composite. A hybrid half-cell was constructed and cycled as proof of principle, and it showed good stability. In addition, a bilayer structure consisting of a porous layer combined with a dense LLZO film was successfully made as a prototype of an all solid-state battery. Finally, a mathematical model was established to propose optimized scaffold structures for battery performance.

25 ENERGY STORAGE↗
DOE OSTI2021

An exact inversion method for extracting orientation ordering by small-angle scattering

Here, we outline a nonparametric inversion strategy for determining the orientation distribution function (ODF) of sheared interacting rods using small-angle scattering techniques. With the presence of direct inter-rod interaction and fluid mechanical forces, the scattering spectra are no longer characterized by the azimuthal symmetry in the coordinates defined by the principal directions of simple shear conditions, which severely compounds the reconstruction of ODFs based on currently available methods developed for dilute systems. Using a real spherical harmonic expansion scheme, the real-space ODFs are uniquely determined from the anisotropic scattering spectra and their numerical accuracy is verified computationally. Our method can be generalized to extract ODFs of uniaxially anisotropic objects under different flow conditions in a properly transformed reference frame with suitable basis vectors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Twin suppression effect of dihydroxy-benzene isomers during the secondary growth of b -oriented zeolite MFI nanosheet films

In this study, the presence of MFI twin crystals on b-axis oriented zeolite MFI nanosheet films was suppressed by adding dihydroxy-benzene isomers in the synthesis mixture. The resulting nanosheet films exhibit good intergrowth and a small grain thickness of 30–45 nm within a relatively short synthesis time (hours). The possible twin suppression mechanisms for the three isomers are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Vertically oriented metamaterial broadband linear polariser

Control and manipulation of polarization is an important topic for imaging and light matter interactions. In the infrared regime, the large wavelengths make wire grid polarizers a viable option, as it is possible to create periodic arrays of metallic wires at that scale. The recent advent of metamaterials has spurred an increase in non-traditional polarizer motifs centred around more complicated repeat units, which potentially provide more functionality. In this paper we explore the use of two-dimensional (2D) arrays of single and back-to-back vertically oriented cross dipoles arranged in a cubic in-plane silicon matrix. Here, we show that both single and back-to-back versions have higher rejection ratios and larger bandwidths than either wire grid polarizers or 2D arrays of linear dipoles.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhancing the distribution grid resilience using cyber-physical oriented islanding strategy

The increasing penetration of distributed generations enables an innovative operation paradigm that allows islanded operation to enhance the resilience of the distribution grid. In this study, a cyber-physical oriented islanding strategy is proposed by coordinating centralised and distributed control to achieve seamless islanding transition and operational flexibility in emergency conditions. A cyber-physical control structure is developed to mitigate various disturbances (e.g. emergencies or fluctuations) according to different operation conditions. Specifically, the distributed fault isolation and seamless islanding transition are coordinated to mitigate the outage caused by unplanned islanding, while a secondary control is proposed to support primary control by reducing the power fluctuations during islanded operation. With a rapid response speed, the local cyber-physical devices are coordinated to accomplish islanding separation by selecting a feasible islanded area even under an unplanned islanding situation. A field test was conducted on a practical distribution network in China, and the results demonstrated the effectiveness and feasibility of the proposed islanding strategy.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Risk-Oriented PMU Placement Approach in Electric Power Systems

The objective of traditional PMU placement approaches is to use the minimal number of PMUs to cover system complete observability. Very few consider the probability and the consequence severity of observability loss. For example, following line trip, grid topology changes, which may results in observability loss and overloaded lines. As long as the overloaded lines are still observable, then we can take action in time to correct the system; and the consequence of the observability loss is not severe, although some parts of the system is not observable. Otherwise, if the overloaded lines become unobservable, then we lose the situation awareness of the system and the consequence of the observability loss is severe. To address the above points in PMU placement, this paper proposes a risk-oriented PMU placement approach. The proposed approach uses two indices, namely the probability of observability loss and its corresponding consequence of severity to design the optimal PMU placement strategy. We show that our proposed approach is able to capture the critical events while the traditional approaches fail to do so. Extensive simulation results carried out on the IEEE 39-bus and 118-bus systems demonstrate its effectiveness.

observability, risk of observability loss, PMUs pl↗
DOE OSTI2017

Epitaxial growth of high quality SrFeO 3 films on (001) oriented (LaAlO 3 ) 0.3 (Sr 2 TaAlO 6 ) 0.7

Growth of strontium ferrite SrFeO 3 films with stoichiometry of (1:1:3) is challenging as the unstable Fe 4+ oxidation state favors the formation of O vacancies. Here, we report layer by layer growth of SrFeO 3 on (001) oriented (LaAlO 3 ) 0.3 (Sr 2 TaAlO 6 ) 0.7 using ozone assisted molecular beam epitaxy. Upon cooling from room temperature, the film’s resistivity decreased from 750 μΩ cm to 150 μΩ cm, as low as the best single crystals, with two identifiable transition points near 110 K and 60 K in resistivity measurements, being hysteretic between cooling and warming through the 60 K transition. During various annealing steps, the low temperature resistivity changes by orders of magnitude, accompanied by an increase in the c-axis lattice parameter. The hysteresis near 60 K persists for a wide range of annealing conditions. We have identified conditions under which changes due to annealing can be reversed. Here, we attribute changes in resistivity and out of plane lattice parameter to the reversible movement of oxygen ions in the lattice. SrFeO 3 may be a promising material for resistive memory applications based upon the control of oxygen vacancies.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Probing orientation information using 3-dimensional reciprocal space volume analysis

We present that the crystallographic texture of polycrystalline materials is the result of how these materials are processed and what external forces materials have experienced. Neutron and X-ray diffraction are standard methods to characterize global crystallographic textures. However, conventional neutron and X-ray texture analyses rely on pole figure inversion routines derived from intensity analysis of individual reflections or powder Rietveld analysis to reconstruct and model the orientation distribution from slices through reciprocal space. In this work, we describe an original approach to directly probe the crystallographic texture information of rolled aluminum from the intensity distribution in 3-dimensional reciprocal space volumes measured simultaneously. Using the TOPAZ time-of-flight Laue neutron diffractometer, reciprocal space analysis allowed determination of “pole spheres” with <1° angular resolution. Finally, these pole spheres are compared with reconstructed pole figures from classic texture analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Perfect control of photoelectron anisotropy for randomly oriented ensembles of molecules by XUV REMPI and polarization shaping

In this work, we report two schemes to generate perfect anisotropy in the photoelectron angular distribution of a randomly oriented ensemble of polyatomic molecules. In order to exert full control over the anisotropy of photoelectron emission, we exploit interferences between single-photon pathways and a manifold of resonantly enhanced two-photon pathways. These are shown to outperform nonsequential (ω, 2ω) bichromatic phase control for the example of CHFClBr molecules. We are able to optimize pulses that yield anisotropic photoelectron emission thanks to a very efficient calculation of photoelectron momentum distributions. Finally, this is accomplished by combining elements of quantum chemistry, variational scattering theory, and time-dependent perturbation theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Electronic reconstruction at the polar (111)-oriented oxide interface

Atomically flat (111) interfaces between insulating perovskite oxides provide a landscape for new electronic phenomena. For example, the graphene-like coordination between interfacial metallic ion layer pairs can lead to topologically protected states [Xiao et al., Nat. Commun. 2, 596 (2011) and A. Rüegg and G. A. Fiete, Phys. Rev. B 84, 201103 (2011)]. The metallic ion/metal oxide bilayers that comprise the unit cell of the perovskite (111) heterostructures require the interface to be polar, generating an intrinsic polar discontinuity [Chakhalian et al., Nat. Mater. 11, 92 (2012)]. Here, we investigate epitaxial heterostructures of (111)-oriented LaAlO 3 /SrTiO 3 (LAO/STO). We find that during heterostructure growth, the LAO overlayer eliminates the structural reconstruction of the STO (111) surface with an electronic reconstruction, which determines the properties of the resulting two-dimensional conducting gas. This is confirmed by transport measurements, direct determination of the structure and atomic charge from coherent Bragg rod analysis, and theoretical calculations of electronic and structural characteristics. Interfacial behaviors of the kind discussed here may lead to new growth control parameters useful for electronic devices.

36 MATERIALS SCIENCE↗