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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Resin infusion of layered metal/composite hybrid and resulting metal/composite hybrid laminate

A method of fabricating a metal/composite hybrid laminate is provided. One or more layered arrangements are stacked on a solid base to form a layered structure. Each layered arrangement is defined by a fibrous material and a perforated metal sheet. A resin in its liquid state is introduced along a portion of the layered structure while a differential pressure is applied across the laminate structure until the resin permeates the fibrous material of each layered arrangement and fills perforations in each perforated metal sheet. The resin is cured thereby yielding a metal/composite hybrid laminate.

Cano, Roberto J.↗
DOE OSTI2020

Synthesis, Crystal and Electronic Structure of Layered AM Sb Compounds ( A = Rb, Cs; M = Zn, Cd): Synthesis, Crystal and Electronic Structure of Layered AM Sb Compounds ( A = Rb, Cs; M = Zn, Cd)

Synthesis, crystal structure, thermal stability, and electronic band structure of four new metal antimonides AMSb (A = Rb, Cs; M = Zn, Cd) are reported. CsZnSb and RbZnSb crystallize in the hexagonal ZrBeSi structure type, in a P6 3 /mmc space group (no. 194, Z = 2) and unit cell dimensions of a = 4.5588(2)/4.5466(4) Å and c = 11.9246(6)/11.0999(10) Å. CsCdSb and RbCdSb crystallize in the tetragonal PbFCl structure type in a P4/nmm space group (no. 129; Z = 2) and unit cell parameters of a = 4.8884(5)/4.8227(3) Å and c = 8.8897(9)/8.5492(7) Å. All four compounds are air- and water-sensitive and are shown through DSC measurements to decompose between 975 K and 1060 K. Analysis of the calculated electronic band structure shows that the Zn-containing antimonides are topologically trivial narrow bandgap semiconductors, whereas Cd-containing compounds exhibit a band inversion along Γ-Z direction.

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

Transport properties and crystal structure of layered LaSb 2

LaSb 2 has a layered crystal structure along the c-axis with ~2% difference between the in-plane orthorombic a and b axes. Here, we report on the thermal conductivity, electrical resistivity, and Seebeck coefficient from 10 to 300 K as well as the magnetoresistance at 10 K. Using the van der Pauw technique on single crystal samples, the in-plane electrical resistivity tensor has been measured and it is found to be isotropic. An anisotropic crystal structure may have isotropic properties, but in the present case, the isotropic nature stems from crystal imperfection. Single crystal X-ray diffraction provides evidence of a mixing of the in-plane a- and b-directions leading to observed diffraction intensity where systematic absences are expected. Whether the underlying structural mechanism is twinning or stacking faults is unknown, but it could be the origin of the previously observed charge density wave states, and it may also explain the high unsaturating linear magnetoresistance reported here. At ambient conditions, LaSb 2 is found to be stable in air, with no sign of bulk degradation after 5 years of storage; however, some change is observed in the amorphous background scattering.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Modeling Water Uptake and Pt Utilization in High Surface Area Carbon

Local transport losses limit high-current density performance of fuel-cells, especially at low Pt-loadings. Optimizing catalyst-layer structure and material properties to mitigate these losses is critical for wide-scale fuel-cell commercialization. Carbon supports form the primary porous structure of catalyst layers in which Pt particles are deposited and ionomer films are distributed. Unlike non-porous carbon supports, high surface area carbon support is unique in its relative humidity dependent Pt utilization and performance due to presence of Pt particles in the micropores interior of carbon particles. We model water uptake and Pt utilization in catalyst layers with high-surface-area carbon support. Interactions between functional groups on the carbon pore walls and water play a vital role in controlling water uptake from water vapor by catalyst layers. Ionomer is shown to influence proton access in micropores, even though it may not deposit into the micropores.

08 HYDROGEN↗
DOE OSTI2023

Layered catalyst structures and methods of making the same

A layered catalyst structure for purifying an exhaust gas stream includes a catalyst support and a palladium catalyst layer including an atomic dispersion of palladium ions electrostatically adsorbed onto an exterior surface of the catalyst support. The catalyst support includes an alumina substrate, a first ceria layer disposed on and extending substantially continuously over the alumina substrate, and a second colloidal ceria layer formed directly on the first ceria layer over the alumina substrate. The palladium catalyst layer is formed on the exterior surface of the catalyst support by applying a palladium-containing precursor solution to the exterior surface of the catalyst support and then heating the catalyst support and the palladium-containing precursor solution. The palladium-containing precursor solution includes a positively charged palladium complex in an aqueous medium and has a pH greater than a point of zero charge of the second colloidal ceria layer.

Gu, Yuntao↗
DOE OSTI2023

Correlating Tomographic Chemical Inhomogeneity and Low Energy Electronic Structure in Layered Quantum Materials

Photoemission spectroscopy (PES) is a suite of experimental tools to learn about the electronic and chemical structure of materials and surfaces. Normally implemented in a surface-sensitive manner, the research performed under this grant focused on pushing PES into less explored regimes, to reveal bulk electronic structure, to reveal tomographic (layer-resolved) chemistry and electronic structure of layered materials and heterostructures, and to reveal interface phenomena at the junction of two different materials. Standing wave (SW) spectroscopies have also been applied to PdCoO2, a material of interest due to its high conductivity and electron-hydrodynamic tendencies. This material can be modeled as an alternating layered structure consisting of metallic Pd layers and insulating CoO2 layers. Using SW XPS, the total electronic structure has been decomposed into contributions from the two layers, and computations highlighted the different many-body interactions in the two layers (Comm. Phys. 4, 143 (2021)). We have also used hard-x-ray angle-resolved photoemission spectroscopy (ARPES), to investigate LaB6, a technologically important material with widespread application as a cathode material for electron microscopes. We measured the bulk electronic structure of this material and found that the one-step model of photoemission better captured the electronic structure and correlations. This model treats the three steps of the photoemission process—excitation, transport of the photoelectron to the crystal surface, and escape into the vacuum—as a single quantum mechanically coherent process (Phys. Rev. Mater. 5, 055002 (2021)). We also applied x-ray photoelectron spectroscopy, implemented in a near total reflection grazing incidence geometry to elucidate technologically relevant interfaces, such as those between a substrate and photoresist (J. Phys. D: Appl. Phys. 54 464002 (2021)).

36 MATERIALS SCIENCE↗
NASA NTRS1985

Electrical coupling effects on the temporal evolution of F layer plasma structure

A time dependent model of F region structure decay by 'classical' cross field diffusion and electrical coupling along magnetic field lines to the E region is examined. The temporal behavior of the ion concentration fluctuations is determined by the electric field in the coupled system as well as by the initial perturbation spectra and the E region recombination rate. The formation of image structure in the E region ion concentration affects the lifetime of F layer structure in a scale size dependent way. Once an image is formed, the image amplitude and the driving F region structure amplitude decay at the same rate. At large scale sizes of at least lambda(2pi/k), this rate is proportional to k2 and the ratio of the temperatures in each region. At small scale sizes it depends on the E region recombination rate and the temperatures of the two regions but is only very weakly dependent on k. The background E region concentration determines the wave number beyond which the structure amplitude decay rate is almost independent of its scale size.

Heelis, R. A.↗
NASA NTRS1993

Experiments on near-wall structure of three-dimensional boundary layers

Investigations of three-dimensional turbulent boundary layers have shown basic differences between two- and three-dimensional flows. These differences can significantly impact the modeling of three-dimensional flows since many flow models are based on results from two-dimensional boundary layers. In many cases the shear stress vector direction has been shown to lag relative to the direction of the mean velocity gradient as the cross flow grows downstream. Coincidence of these vectors is necessary for a scalar eddy viscosity modeling assumption. A second effect is a reduction in magnitude of the shear stress and/or the shear stress to turbulence energy ratio, a(sub 1). This reduction has been observed in several experiments. Recent numerical simulations also indicate wall-layer structural differences between two- and three-dimensional boundary layers. The differences in structure between two- and three-dimensional boundary layers was also addressed in the experiment of Littell & Eaton. The experiment used two-point correlations to investigate the vortical structures in a three dimensional boundary layer on a spinning disk. It was found that each sign of longitudinal vortex is equally likely to exist, but one sign of vorticity is associated with a structure which is better at producing ejections. The goal of the current investigation is to study the structure of the inner layers. Among other questions, the differences between the effects deduced from the three-dimensional flow simulations and the effects seen in experiments can be examined. The research concentrates on the structure of the wall-layer through flow visualization and direct turbulence measurements down to y(+) = 5.

Flack, Karen A.↗
NASA NTRS1992

The present state and the future direction of eddy viscosity models

Information is given in viewgraph form on the present state and future direction of eddy viscosity models. Topics covered include the eddy viscosity dilemma, two-equation models, equations of motion, free shear flows, incompressible free shear flows, model-predicted boundary layer structure, defect layer analysis, the effects of pressure gradients, viscous sublayer structure, wall functions and viscous damping, viscous damping for kappa-omega, the effects of compressibility, perturbation analysis of the wall layer, an alternative compressibility term, unsteady boundary layers, incompressible separation, backstep results, and compressible separation.

Wilcox, David C.↗
NASA NTRS1999

Discovery of a Three-Layered Atmospheric Structure in Accretion Disks around Stellar-Mass Black Holes

We have carried out systematic modeling of the X-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40, using our newly developed spectral fitting methods. Our results reveal, for the first time, a three-layered structure of the atmosphere in the inner region of the accretion disks. Above the conanonly known, cold and optically thick disk of a blackbody temperature 0.2-0.5 keV, there is a layer of warm gas with a temperature of 1.0-1.5 keV and an optical depth of around 10. Compton scattering of the underlying disk blackbody photons produces the soft X-ray component we comonly observe. Under certain conditions, there is also a much hotter, optically thin corona above the warm layer, characterized by a temperature of 100 keV or higher and an optical depth of unity or less. The corona produces the hard X-ray component typically seen in these sources. We emphasize that the existence of the warm layer seem to be independent of the presence of the hot corona and, therefore, it is not due to irradiation of the disk by hard X-rays from the corona. Our results suggest a striking structural similarity between the accretion disks and the solar atmosphere, which may provide a new stimulus to study the common underlying physical processes operating in these vastly different systems. We also report the first unambiguous detection of an emission line around 6.4 keV in GRO J1655-40, which may allow further constraining of the accretion disk structure. We acknowledge NASA GSFC and MFC for partial financial support. (copyright) 1999: American Astronomical Society. All rights reverved.

Zhang, S. N.↗
NASA NTRS2005

Pervasive Layering in the Lunar Highland Crust: Evidence from Apollos 15, 16,and 17

This paper presents results of a photogeologic reconnaissance of 70 mm photographs taken on the lunar surface during the Apollo 15, 16, and 17 missions, whose primary objective was to investigate the lunar highland crust. Photographs at all three sites, notably the Apennine Front, show pervasive layered structure. These layers are easily distinguished from lighting artifacts, and are considered genuine crustal structures. Their number, thickness, and extent implies that they are lava flows, not ejecta blankets or intrusive features. They appear to be the upper part of the earliest lunar crust, possibly forming a layer tens of kilometers thick. Remote sensing studies (X-ray fluorescence and reflectance spectroscopy), indicate that the highland crust is dominantly a feldspathic basalt. It is concluded that the highland layers represent a global crust formed by eruptions of high-alumina basalt in the first few hundred million years of the Moon's history.

Lowman, Paul D., Jr.↗
NASA NTRS1987

Conserved variable analysis of the convective boundary layer thermodynamic structure over the tropical oceans

An analysis of FGGE dropwindsonde data using conserved thermodynamic variables shows mixing line structures for the convective boundary layer over the equatorial Pacific. Deeper boundary layers show a double structure. Reversals of the gradients of mixing ratio and equivalent potential temperature above the boundary-layer top are present in all the averages and suggest that the origin of the air sinking into the boundary layer needs further study.

Betts, Alan K.↗
NASA NTRS1994

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Koontz, Steven L.↗
NASA NTRS1992

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Koontz, Steven L.↗
DOE OSTI2022

Novel self-assembled two-dimensional layered oxide structure incorporated with Au nanoinclusions towards multifunctionalities

Two-dimensional (2D) layered oxides have recently attracted wide attention owing to the strong coupling among charges, spins, lattice, and strain, which allows great flexibility and opportunities in structure designs as well as multifunctionality exploration. In parallel, plasmonic hybrid nanostructures exhibit exotic localized surface plasmon resonance (LSPR) providing a broad range of applications in nanophotonic devices and sensors. A hybrid material platform combining the unique multifunctional 2D layered oxides and plasmonic nanostructures brings optical tuning into the new level. Here, a novel self-assembled Bi 2 MoO 6 (BMO) 2D layered oxide incorporated with plasmonic Au nanoinclusions has been demonstrated via one-step pulsed laser deposition (PLD) technique. Comprehensive microstructural characterizations, including scanning transmission electron microscopy (STEM), differential phase contrast imaging (DPC), and STEM tomography, have demonstrated the high epitaxial quality and particle-in-matrix morphology of the BMO-Au nanocomposite film. DPC-STEM imaging clarifies the magnetic domain structures of BMO matrix. Three different BMO structures including layered supercell (LSC) and superlattices have been revealed which is attributed to the variable strain states throughout the BMO-Au film. Owing to the combination of plasmonic Au and layered structure of BMO, the nanocomposite film exhibits a typical LSPR in visible wavelength region and strong anisotropy in terms of its optical and ferromagnetic properties. This study opens a new avenue for developing novel 2D layered complex oxides incorporated with plasmonic metal or semiconductor phases showing great potential for applications in multifunctional nanoelectronics devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Metal chalcogenides for pseudocapacitive applications

A synthetic metal dichalcogenide having a highly defected nanocrystalline layered structure, wherein layer spacing is larger than in perfect crystals of the same material, wherein the defected structure provides access to interlayer crystals of the same material, and wherein the defected structure facilitates a pseudocapacitive charge storage mechanism. The metal dichalcogenide is receptive to intercalation of ions such as Li ions, Na ions, Mg ions, and Ca ions, and does not undergo a phase transition upon intercalation of Li ions, Na ions, Mg ions, or Ca ions. The metal dichalcogenide can be used, for example, as a component of an electrode that also includes a carbon derivative, and a binder, which are intermixed to form the electrode. The resultant composite electrode is highly porous and highly electronically conductive, and is suitable for use in devices such as symmetric capacitors, asymmetric capacitors, rocking chair batteries, and other devices.

25 ENERGY STORAGE↗
DOE OSTI2022

Extreme Fast Charging: Effect of Positive Electrode Material on Crosstalk

Extreme fast charging (XFC) is a key requirement for the adoption of battery-based electric vehicles by the transportation sector. However, XFC has been shown to accelerate degradation, causing the capacity, life, and safety of batteries to deteriorate. We tested cells containing five positive electrode chemistries, LFP (olivine structure), LMO (spinel), LCO (layered), NMC811 (layered) and NCA (layered), using fast-charging protocols. After testing, the negative electrodes from cells containing positive electrodes crystallizing with a layered structure were found to have more lithium deposited on their surfaces. Further, those crystallizing with a layered structure also tended to have a larger increase in impedance than those crystallizing with a spinel or olivine structure. Characterization of the negative electrodes by X-ray photoelectron spectroscopy showed that using the concentrations of LiF and Li x PO y F z as metrics, the concentration of LiF in the SEI from the cell with different positive electrodes is LFP > LMO > LCO ~ NMC811 > NCA; and for Li x PO y F z , the order is LMO > LFP > NCA > NMC811 > LCO. Clearly, the positive-electrode material was influencing the amounts of these materials formed.

25 ENERGY STORAGE↗