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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Reflectivity, Emissivity, and Brightness from Multilayered Soil with Linearly Varying Permittivity at P- and L- bands

Passive sensing of root zone soil moisture is theoretically investigated using P and L band frequencies. The soil is considered to be a stratified medium. The reflectivity from the soil surface is found by considering the soil to be composed of a finely layered structure with layer widths that are small compared to a wavelength. A well-known transmission line algorithm is then used to compute the reflectivity at the surface. Emissivity is obtained as (1 – reflectivity). It assumed that the soil is at a constant temperature of 300o K when determining the brightness temperature. A soil moisture profile consisting of two homogeneous layers separated by a layer of linearly varying soil moisture is investigated. The study is made at an incident angle of 40O for horizontal polarization at 0.8 and 1.4 GHz. Two variations of the basic profile are considered: a transition from a layer of lesser moisture to a layer of greater moisture and the opposite. In both cases the P band signal shows greater penetration than the L band case. There is greater penetration in the transition to drier soils. In both cases the L band signals show sensitivity to only the upper surface of the soil as expected.

Ming Li↗
DOE OSTI2023

Structural Stability of Graphene-Supported Pt Layers: Diffusion Monte Carlo and Density Functional Theory Calculations

In this study, we used a combination of diffusion Monte Carlo and density functional theory calculations to investigate the stability and interlayer binding of various layered structures of Pt atoms adsorbed on graphene. Our findings show that vertically buckled Pt monolayer and bilayer with (111)-packing order are more energetically favorable than the corresponding buckled (100) or flat (100)-packing structures. This can be attributed to the significant lattice mismatch (>10%) between pristine graphene and a free-standing (100)-packing Pt layer. Additionally, our calculations reveal that among the (100)-packing Pt layers, an incommensurate structure with a Pt/C atomic ratio less than 1/2 may be more stable than the commensurate structures registered at the bridge sites, which aligns with recent experimental findings of incommensurate (100)-packing Pt layers on graphene. The interlayer binding between the Pt layer and graphene is found to be primarily driven by van der Waals interaction, except for the AA-stacked buckled-(100) Pt bilayer where the bottom Pt atoms show chemisorption to the graphene surface. In conclusion, this research offers a comprehensive examination of the stability and interlayer binding of metallic Pt layers, providing valuable insights for potential applications as a next-generation catalyst.

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

Magnetoelastically actuated MEMS device and methods for its manufacture

A magnetoelastically actuated device includes a microscale cantilever arm supported at a standoff distance from a substrate. The cantilever arm is formed as a laminar magnetic actuator configured to bend when it is subjected to a magnetic field. The cantilever arm includes a film of magnetostrictive material. Also provided is a method for fabricating the magnetoelastically actuated device. The method includes defining an actuator mold in a layer of photoresist on a structural layer of the cantilever arm and electrodepositing a layer of a magnetostrictive alloy containing cobalt and iron onto the structural layer within the actuator mold.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Attenuation of Spin Precession in Manganite/Normal Metal Heterostructures

Abstract—Temperature dependence of attenuation of magnetic spin precession in two-layer structures with a Pt top layer based on a La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) epitaxial manganite film is studied by measuring the width of a ferromagnetic resonance (FMR) line. Ferromagnetic resonance in thin ferromagnetic manganite films is used for the creation of a spin current at the interface between the metallic and ferromagnetic layers. A significant increase in a width of a line in FMR spectrum in two-layer structures due to generation of a spin current, heterogeneity of a ferromagnetic layer, two-magnon scattering, and eddy current is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1991

Whiskerless Schottky diode

A Schottky diode for millimeter and submillimeter wave applications is comprised of a multi-layered structure including active layers of gallium arsenide on a semi-insulating gallium arsenide substrate with first and second insulating layers of silicon dioxide on the active layers of gallium arsenide. An ohmic contact pad lays on the silicon dioxide layers. An anode is formed in a window which is in and through the silicon dioxide layers. An elongated contact finger extends from the pad to the anode and a trench, preferably a transverse channel or trench of predetermined width, is formed in the active layers of the diode structure under the contact finger. The channel extends through the active layers to or substantially to the interface of the semi-insulating gallium arsenide substrate and the adjacent gallium arsenide layer which constitutes a buffer layer. Such a structure minimizes the effect of the major source of shunt capacitance by interrupting the current path between the conductive layers beneath the anode contact pad and the ohmic contact. Other embodiments of the diode may substitute various insulating or semi-insulating materials for the silicon dioxide, various semi-conductors for the active layers of gallium arsenide, and other materials for the substrate, which may be insulating or semi-insulating.

Bishop, William L.↗
DOE OSTI2019

Dual function composite oxygen transport membrane

A dual function composite oxygen transport membrane having a layered structure of mixed conducting oxygen transport materials on a first side of a porous substrate and a reforming catalyst layer on an opposing second side of the porous substrate. The layered structure of the mixed conducting oxygen transport materials contains an intermediate porous layer of mixed conducting oxygen transport materials formed on the porous substrate with a dense impervious layer of mixed conducting oxygen transport materials over the intermediate porous layer, and an optional surface exchange layer of mixed conducting oxygen transport materials over the dense impervious layer. The layered structure and the reforming catalyst layer are formed in separate steps.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Modularization of Ceramic Hollow Fiber Membrane Technology for Air Separation

This proposed project is aimed at studying high performance and economically competitive ceramic membrane technology for air separation and high-purity oxygen production using hollow fiber ceramic membrane stack and module technology. The design of the single permeate membrane is a hollow fiber substrate-supported thin tri-layer structure. Radially well-aligned micro-channels are embedded in the thick substrate and open at the inner surface of the substrate, enabling facile air/gas diffusion. The tri-layer structure of thin dense membrane layer (~ 10 µm) sandwiched by porous surface layer on either side is then built on the substrate using advanced fabrication process. The tri-layer structure design allows different materials to be used in different layers, where the materials of surface layers have high surface exchange coefficients while the material of dense layer has high bulk diffusivity. Such a synergetic combination leads to high permeation performance. The focus of the proposed project will be on membrane stack/module development using the developed single hollow fiber membranes, including: 1) fabrication and characterization of novel single hollow fiber membranes; 2) membrane stack design and assembly using fabricated single membranes; 3) stack modeling and analysis to guide membrane stack designs; 4) permeation performance testing and characterization of membrane stacks. The hollow fiber feature and simple sealing requirement enable very compact design of membrane stacks, which have excellent flexibility for further modularizations at different scales. The operations of such membrane stack and module may employ the exhaust heat from other components of Integrated Gasification Combined Cycle and oxy-combustion systems. Therefore, modularization of such an air separation membrane technology can be incorporated into the DOE’s REMS (radically engineered modular systems)-gasification skid and support the oxidant feed of an oxygen-blown REMS gasifier scaled to different ranges.

01 COAL, LIGNITE, AND PEAT↗
NASA NTRS2005

NiAl-Based Approach For Rocket Combustion Chambers

A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected form Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

Michael V Nathal↗
NASA NTRS2005

NiAl-based approach for rocket combustion chambers

A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected from Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

Nathal, Michael V.↗
NASA NTRS1997

The CSSL (combined sporadic structures and layers) payload: In situ observations of mesospheric sodium and related parameters

The objectives, design and results of the sensor systems for the combined sporadic structures and layers (CSSL) payload are analyzed. The CSSL main objectives were to: validate current models of mesospheric sodium chemistry; explore the relationship between turbulence and Na fluctuations; and to explore the relationship between high latitude electric fields and the formation of Na anomalies.

Machuga, David W.↗
NASA NTRS2000

Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of the inner accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

Zhang, S. N.↗
DOE OSTI2019

A novel optical polarization conversion structure designed by multi-layered thin film structures at the wavelength of 10.6 μm

Polarization conversion performance is one of the most important design contents of optical devices. At present, there are many ways to implement polarization conversion. However, they are mostly based on the form of split ring resonator or equivalent plasma, which are not conducive to the miniaturization of electromagnetic devices, particularly in the field of laser applications. In this paper, a novel optical polarization conversion structure has been designed by multi-layered PS/PTFE thin film structures at the wavelength of 10.6 μm based on the equivalent medium theory. Then it was verified that the proposed structure can effectively convert the linear polarized wave to circular polarized wave by the EM full-wave simulation. Compared with the current laser polarization manipulation devices, the proposed novel polarization converter has advantages of ultrathin thickness of structure, simple structure, good light transmission and no electromagnetic loss. Although the structural parameters in this paper are designed for EM wave the wavelength of 10.6 μm, the proposed design idea of the polarization conversion structure is also suitable for the electromagnetic wave at other wavelengths.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2006

ALPS: The Age-Layered Population Structure for Reducing the Problem of Premature Convergence

To reduce the problem of premature convergence we define a new attribute of an individual, its age, and propose the Age-Layered Population Structure (ALPS), in which age is used to restrict competition and breeding between members of the population. ALPS differs from a typical EA by segregating individuals into different age-layers by their age - a measure of how long the genetic material has been in the population - and by regularly replacing all individuals in the bottom layer with randomly generated ones. The introduction of new, randomly generated individuals at regular intervals results in an EA that is never completely converged and is always looking at new parts of the fitness landscape. By using age to restrict competition and breeding search is able to develop promising young individuals without them being dominated by older ones. We demonstrate the effectiveness of the ALPS algorithm on an antenna design problem in which evolution with ALPS produces antennas more than twice as good as does evolution with two other types of EAs. Further analysis shows that the ALPS model does allow the offspring of newly generated individuals to move the population out of mediocre local-optima to better parts of the fitness landscape.

Hornby, Gregory S.↗
DOE OSTI2020

The effect of chemically preintercalated alkali ions on the structure of layered titanates and their electrochemistry in aqueous energy storage systems

We introduce a novel chemical preintercalation synthesis technique based on a hydrogen peroxide induced sol–gel process to obtain alkali ion containing ternary layered titanates (MTO, where M = Li, Na, K). Synthesis parameters leading to the formation of single-phase materials with homogeneous elemental distribution are reported for each of the preintercalated ions. Our analyses indicate that the interlayer spacing in the structure of the layered titanates increases with the increase of the radius of the hydrated preintercalated ion. Scanning and transmission electron microscopy imaging revealed morphological diversity: the LTO phase crystallized as nanoplates assembled in “peony-like” spherical agglomerates while NTO and KTO particles exhibited a one-dimensional nanobelt or wire-like morphology, with the KTO nanobelts being shorter and more aggregated than the NTO nanobelts. Structural refinement corroborated by electron diffraction and high-resolution transmission electron microscopy revealed that the structure of the LTO phase is built by stacking Ti–O layers containing a single straight layer of connected TiO 6 octahedra. The layers in NTO and KTO structures form differently and consist of double Ti–O layers with two titanium rows and ragged arrangement of units built by TiO6 octahedra. The NTO electrodes exhibited the highest electrochemical performance in cells with aqueous 1 M Na 2 SO 4 electrolyte, followed by the KTO electrodes and then LTO electrodes, and this trend is maintained at various scan rates. The established relationships between the structure and electrochemical performance reveal that, in addition to interlayer distance and chemistry of the interlayer region, the structure of the layers can play an important role in charge storage properties of layered oxide electrodes. The double Ti–O layers in the structure of NTO and KTO phases provide a larger number of redox centers which could contribute to the superior electrochemical performance as compared to the LTO electrodes. Our findings indicate that layered materials containing double transition metal oxide layers are promising candidates for exfoliation and assembly with electronically conductive layers with the aim to create 2D heterostructures with high electrochemical performance.

25 ENERGY STORAGE↗
NASA NTRS2010

Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers

Structural skeleton of high Reynolds number flow gives insight into smooth and rough walls. (modeling implications not yet clear) Dynamic roughness as a model of "designer" roughness: a) Impose length scale(s) and dominant frequency. b) Irregular roughness well-represented by first "few" POD modes (Christensen, 2009). Experiments and simple model demonstrate: a) Harmonics associated with forcing (and w) important. b) Change to the mean profile (skin friction).

McKeon, Beverley J.↗
DOE OSTI2021

Tailorable multifunctionalities in ultrathin 2D Bi-based layered supercell structures

Two-dimensional (2D) materials with robust ferromagnetic behavior have attracted great interest because of their potential applications in next-generation nanoelectronic devices. Aside from graphene and transition metal dichalcogenides, Bi-based layered oxide materials are a group of prospective candidates due to their superior room-temperature multiferroic response. In this work, an ultrathin Bi 3 Fe 2 Mn 2 O 10+δ layered supercell (BFMO322 LS) structure was deposited on an LaAlO 3 (LAO) (001) substrate using pulsed laser deposition. Microstructural analysis suggests that a layered supercell (LS) structure consisting of two-layer-thick Bi–O slabs and two-layer-thick Mn/Fe–O octahedra slabs was formed on top of the pseudo-perovskite interlayer (IL). A robust saturation magnetization value of 129 and 96 emu cm -3 is achieved in a 12.3 nm thick film in the in-plane (IP) and out-of-plane (OP) directions, respectively. The ferromagnetism, dielectric permittivity, and optical bandgap of the ultrathin BFMO films can be effectively tuned by thickness and morphology variation. In addition, the anisotropy of all ultrathin BFMO films switches from OP dominating to IP dominating as the thickness increases. This study demonstrates the ultrathin BFMO film with tunable multifunctionalities as a promising candidate for novel integrated spintronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

The simulation on absorption properties of metamaterial/GaAs/electrode layer hybrid structure based Terahertz photoconductive detector

Terahertz (THz) photodetectors have attracted great attention from scientists worldwide for their application in security checking, biomedical treatment and astronomical observation of remote stars and distant galaxies. As a typical THz detector, extrinsic GaAs based photoconductive detector is facing critical technical bottlenecks in the epitaxial growth of sufficiently thick and high-quality GaAs absorption layer. In this work, a novel THz photoconductive detector based on metamaterial/GaAs/electrode layer hybrid structure was designed and simulated. By setting the periodic split ring resonator (SRR) structure as 88 μm pitch with 8 μm width, the absorption peaks exist at the wavelength of about 142 and 367 μm, which originate from the resonant cavity and the SRR dipole resonance effect, and the novel device shows a significant enhancement compared with the conventional GaAs photoconductive detector. Thus, the necessary thickness of GaAs absorption-layer is largely reduced, and the resonant absorption peak can be modulated by changing the thickness of absorption layer. This work provides a novel device structure which can solve the critical epitaxial growth bottleneck of GaAs photoconductive detector and used for the astronomical observation, security check, etc.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗