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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Thermomechanical buckling of multilayered composite panels with cutouts

A study is made of the thermomechanical buckling of flat unstiffened composite panels with central circular cutouts. The panels are subjected to combined temperature changes and applied edge loading (or edge displacements). The analysis is based on a first-order shear deformation plate theory. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the plate. Both the stability boundary and the sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the buckling response to variations in the different lamination and material parameters of the panel. Numerical results are presented showing the effects of the variations in the hole diameter, laminate stacking sequence, fiber orientation, and aspect ratio of the panel on the thermomechanical buckling response and its sensitivity coefficients.

THERMOMECHANICAL BUCKLING↗
NASA NTRS2016

Design and Operation of a Calorimeter for Advanced Multilayer Insulation Testing

A calorimeter has been constructed to accurately measure insulation performance with a nominal 90K outer boundary and a 20K inner boundary. Unique features of this design include use of mechanical cryocoolers instead of cryogens and measurement of the heat load with a calibrated heat conduction rod. The calorimeter is operational and has completed its first test series. The initial test series was designed to look for differences in performance between a single layer of aluminum foil and a sheet of double aluminized Mylar (DAM). Although it has been speculated that the aluminum foil would perform better, since the aluminum coating on the Mylar might not be thick enough to stop the transmission of long wave length infrared radiation, our testing showed a higher heat load for the aluminum foil than the DAM. The aluminum foil showed a heat load of 132 mW at an 87 K outer temperature and 152 mW at a 107K outer temperature, whereas the DAM showed a heat load of 66 mW at an 88 K outer temperature and 81 mW at 108 K.

Multilayer insulation↗
NASA NTRS2016

Design and Operation of a Calorimeter for Advanced Multilayer Insulation Testing

A calorimeter has been constructed to accurately measure insulation performance with a nominal 90K cold outer boundary and a 20K inner boundary. Unique features of this design include use of mechanical cryocoolers instead cryogens and measurement of the heat load with a calibrated rod to serve as a conduction path. The calorimeter is operational and has completed its first test series. The initial test series was designed to look for differences in performance between a single layer of aluminum foil and a sheet of double aluminized mylar (DAM). Although it has been speculated that the aluminum foil would perform better, since the mylar coating might not thick enough to stop the transmission of long wave length infrared radiation, our testing showed a higher heat load for the aluminum foil than the DAM. The aluminum foil showed a heat load of 132 mW at an 87 K outer temperature and 152 mW at a 107K outer temperature. Whereas the DAM showed a heat load of 66 mW at an 88 K outer temperature and 81 mW at 108 K.

Cryogenics↗
NASA NTRS2017

Heat Loads Due to Small Penetrations in Multilayer Insulation Blankets

Abstract: This paper covers cryogenic, tensile testing and research completed on a number of epoxies used in cryogenic applications. Epoxies are used in many different applications; however, this research focused on the use of epoxy used to bond MLI standoffs to cryogenic storage tanks and the loads imparted to the tank through the MLI. To conduct testing, samples were made from bare stainless steel, aluminum and primed aluminum. Testing involved slowly cooling test samples with liquid nitrogen then applying gradually increasing tensile loads to the epoxy. The testing evaluated the strength and durability of epoxies at cryogenic temperatures and serves as a base for future testing. The results of the tests showed that some epoxies withstood the harsh conditions while others failed. The two epoxies yielding the best results were Masterbond EP29LPSP and Scotch Weld 2216. For all metal surfaces tested, both epoxies had zero failures for up to 11.81 kg of mass.

multilayer insulation↗
DOE OSTI2019

Processing of Dilute Mg–Zn–Mn–Ca Alloy/Nb Multilayers by Accumulative Roll Bonding

Recent advancements in the severe plastic deformation process called accumulative roll bonding (ARB) can help to address the long-standing need for manufacturing lightweight, high-strength Mg sheet materials. However, the fabrication of Mg alloy-based laminates via ARB remains a challenge due to the intrinsically poor formability of Mg. Herein, it is shown that Mg-based composite laminates with refined layers can be fabricated via several room-temperature ARB cycles with appropriate intermediate annealing and alloy selection. The final laminates made here consist of equal volume fractions of a dilute Mg–Zn–Mn–Ca alloy phase and a pure Nb phase with fine 150 μm layer thicknesses. Deformation texture evolution in both phases within the composite is analyzed via neutron diffraction measurements taken at different stages in the process. The analysis suggests that the annealing step recrystallizes the Mg-alloy phase. It is also shown that for both phases, the stabilized deformation textures within the composite correspond to the classic stable textures of the individual constituents. Polycrystal texture modeling implies that {10–12} <-1011> extension twinning developed in the Mg alloy during rolling.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Super Gas Barrier and Fire Resistance of Nanoplatelet/Nanofibril Multilayer Thin Films

Abstract Cellulose nanofibrils (CNF) are abundant in the fiber cell walls of many plants and are considered a nearly inexhaustible resource. With the goal of improving the flame resistance and gas barrier properties of cellulose‐based films, cationic CNF are assembled with anionic vermiculite (VMT) clay using the layer‐by‐layer deposition process. The highly aligned VMT nanoplatelets, together with cellulose nanofibrils, form a nanobrick wall structure that exhibits high optical transparency, flame resistance, super oxygen barrier, and high modulus. A 20 CNF/VMT bilayer (BL) nanocoating, with a thickness of only 136 nm, exhibits an oxygen transmission rate of 0.013 cc (m 2 day atm) –1 . With only 2 BL of CNF/VMT, the melting of flexible polyurethane foam exposed to a butane torch is prevented. These nanocoatings also exhibit a high elastic modulus (20 GPa) and hardness (1 GPa). This study demonstrates a unique, renewable, cellulose‐based nanocoating that could be used in a variety of packaging and protection applications.

Qin, Shuang↗
DOE OSTI2025

Evolution of the Electronic Gap of Directly Synthesized Versus Mechanically Transferred WS 2 Monolayer to Multilayer Films

The electronic properties of 2D materials play a critical role in determining their potential for device applications. Despite rapid developments in 2D semiconductors, studies of fundamental electronic parameters, including the electronic gap and ionization energy, are limited, with significant discrepancies in reported values. The study focuses on tungsten disulfide (WS₂) and investigates the electronic structure of films comprising an increasing number of layers deposited with two different methods: direct synthesis via metal–organic chemical vapor deposition (MOCVD) and additive mechanical transfer of exfoliated single layers. The films are characterized via Raman, UV–vis, and photoluminescence spectroscopies, as well as ultraviolet photoelectron and inverse photoemission spectroscopies (UPS/IPES). The electronic gap of WS₂ is found to decrease from 2.43 eV for the monolayer to 1.97 eV for the trilayer, indicating a bulk transition at the trilayer thickness. This reduction in the electronic gap is primarily due to the downward shift of the conduction band minimum relative to the valence band maximum. A comparative analysis with MOCVD-grown WS₂ reveals a slightly larger electronic gap for MOCVD-grown samples, attributed to differences in defect densities. The electronic levels evaluated through UPS/IPES highlight the significant influence of preparation methods on the electronic properties of WS₂.

2D materials↗
DOE OSTI2024

Regulating the Third Metal to Design and Engineer Multilayered NiFeM (M: Co, Mn, and Cu) Nanofoam Anode Catalysts for Anion-Exchange Membrane Water Electrolyzers

In this study, alkaline anion-exchange membrane water electrolyzers (AEMWEs) for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant platinum group metal (PGM)-free catalysts. Herein, the third metal is incorporated into NiFe-based catalysts to regulate their electronic structures and morphologies, aiming to achieve sufficient oxygen evolution reaction (OER) activity and performance in AEMWEs. The ternary NiFeM (M: Cu, Co, or Mn) catalysts are featured with multiple layered structures and nanofoam network morphologies, consisting of highly OER-active amorphous Ni-rich oxide shells and electrically conductive metallic alloy cores. The physical and electronic perturbations to the NiFe induced by a third element lead to a fine-tuning of the redox ability of the metal sites at the reaction centers, which breaks the scaling relationship between OH* and O* intermediates at the reaction centers. Thus, the unique structural configuration and electronic regulation simultaneously benefit catalytic activity and performance improvements. These NiFeM nanofoam catalysts demonstrated promising anode performance in actual AEMWEs, comparable to the IrO 2 reference, especially at high current densities. Notably, using various electrolytes (e.g., KOH solution or pure water) for AEMWEs exhibited a different performance trend among studied NiFeM catalysts, likely due to dynamic changes of catalysts under various OER environments.

25 ENERGY STORAGE↗
DOE OSTI2020

First-Principles Quantum Transport Modeling of Spin-Transfer and Spin-Orbit Torques in Magnetic Multilayers

A unified approach for computing (i) spin-transfer torque in magnetic trilayers like spin valve and magnetic tunnel junction, where injected charge current flows perpendicularly to interfaces, and (ii) spin-orbit torque in magnetic bilayers of the type ferromagnet/spin-orbit-coupled material, where injected charge current flows parallel to the interface, was reviewed. The experimentally explored and technologically relevant spin-orbit-coupled materials include 5d heavy metals, topological insulators, Weyl semimetals, and transition metal dichalcogenides. This approach requires to construct the torque operator for a given Hamiltonian of the device and the steady-state nonequilibrium density matrix, where the latter is expressed in terms of the nonequilibrium Green’s functions and split into three contributions. Tracing these contributions with the torque operator automatically yields field-like and damping-like components of spin-transfer torque or spin-orbit torque vector, which is particularly advantageous for spin-orbit torque where the direction of these components depends on the unknown-in-advance orientation of the current-driven nonequilibrium spin density in the presence of spin-orbit coupling. Illustrative examples are provided by computing spin-transfer torque in a one-dimensional toy model of a magnetic tunnel junction and realistic Co/Cu/Co spin valve, both of which are described by first-principles Hamiltonians obtained from noncollinear density functional theory calculations, as well as by computing spin-orbit torque in a ferromagnetic layer described by a tight-binding Hamiltonian which includes spin-orbit proximity effect within ferromagnetic monolayers assumed to be generated by the adjacent monolayer transition metal dichalcogenide. In addition, it is shown here how spin-orbit proximity effect, quantified by computing (via first-principles retarded Green’s function) spectral functions and spin textures on monolayers of realistic ferromagnetic material like Co in contact with heavy metal or monolayer transition metal dichalcogenide, can be tailored to enhance the magnitude of spin-orbit torque. Furthermore, errors made in the calculation of spin-transfer torque are quantified when using Hamiltonian from collinear density functional theory, with rigidly rotated magnetic moments to create noncollinear magnetization configurations, instead of proper (but computationally more expensive) self-consistent Hamiltonian obtained from noncollinear density functional theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Combination of Mesenchymal Stromal Cells and Cardiac Stem Cells in a Multilayer Cell Construct Promotes Activation of Notch Signaling and Initiation of Endothelial Differentiation

We showed the possibility of generating combined tissue-engineered cell consisting of layers of rat cardiac stem cells and mesenchymal stromal cells from the adipose tissue. Cell—cell interaction within the cell sheet promoted proliferation of cardiac stem cells, expression of endothelial differentiation marker ETS1, and Notch signaling activation. The obtained results provide new insights into possible mechanisms of stimulation of endogenous regeneration processes after myocardial damage and demonstrate potential of cell-based cardiomyoplasty with the use of these combined cell sheets.

60 APPLIED LIFE SCIENCES↗