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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
DOE OSTI2015

Characterization of Cr-rich Cr-Sb multilayer films: Syntheses of a new metastable phase using modulated elemental reactants

The new metastable compound Cr{sub 1+x}Sb with x up to 0.6 has been prepared via a thin film approach using modulated elemental reactants and investigated by in-situ X-ray reflectivity, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis as well as transmission electron microscopy and atomic force microscopy. The new Cr-rich antimonide crystallizes in a structure related to the Ni{sub 2}In-type structure, where the crystallographic position (1/3, 2/3, 3/4) is partially occupied by excess Cr. The elemental layers of the pristine material interdiffused significantly before Cr{sub 1+x}Sb crystallized. A change in the activation energy was observed for the diffusion process when crystal growth starts. First-principles electronic structure calculations provide insight into the structural stability, magnetic properties and resistivity of Cr{sub 1+x}Sb. - Graphical abstract: 1 amorphous multilayered film 2 interdiffused amorphous film 3 metastable crystalline phase 4 thermodynamic stable phase (and by-product). - Highlights: • Interdiffusion of amorphous Cr and Sb occurs before crystallization. • Crystallization of a new metastable phase Cr{sub 1.6}Sb in Ni{sub 2}In-type structure. • The new Cr-rich phase shows half-metallic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Deformation textures of aluminum in a multilayered Ti/Al/Nb composite severely deformed by accumulative roll bonding

The accumulative roll bonding process was carried out to produce multilayered Ti/Al/Nb composites up to four cycles. Scanning electron microscopy, transmission electron microscopy electron backscattered diffraction and nanoindentation were employed to investigate the microstructural and texture evolution. A homogenous distribution of Ti/Nb necking layers in Al matrix was achieved after four ARB cycles. Grain refinement was observed to increase with increasing number of ARB cycles. The fraction of high-angle grain boundaries as also increased. Strong recrystallization texture appeared for high number of ARB cycles due to the adiabatic heat that occurs during ARB processing. The shear band at the Ti/Al interface reduced the intensity of the cold rolling fiber textures of Al. There was no evidence of shear component from the orientation distribution function results.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of GLAD technique on optical properties of ZnS multilayer antireflection coatings

Highlights: • ZnS multi-layer antireflection coatings have been prepared by GLAD technique. • XRD analysis depicts that all the multi-layer samples are crystallized in cubic structure. • FESEM images confirmed the multi-layer and inclined formation of specimens. • Transmission increment and refractive index decrement obtained for the multi-layer samples. • Incredible impression of GLAD technique on multi-layer coatings is realized. - Abstract: In this work, we prepared Zinc sulfide (ZnS) multi-layer antireflection coatings applying glancing angle deposition (GLAD) technique by physical vapor deposition method. By comparing the structural and optical properties of the samples prepared at normal and inclined single layer coatings, salient effect of multi-layer coatings composed of normal and inclined layers are observed. Relative improvement in crystallinity of the GLAD produced films with respect to inclined single layer resulted from X-ray diffraction (XRD) studies. Despite high increment in average transmission, explicit reduction in refractive index of the multilayer specimens are obtained by Ultraviolet–visible spectroscopy (UV–VIS) analysis. Both the abovementioned changes are in the direction of improving the anti-reflectivity features.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Adsorption of polyelectrolyte multilayers imparts high monovalent/divalent cation selectivity to aliphatic polyamide cation-exchange membranes

Nafion membranes coated with polyelectrolyte multilayers (PEMs) exhibit outstanding monovalent/divalent cation electrodialysis selectivity in a single-membrane cell. Nevertheless, the high cost of Nafion and the extensive pretreatments required for polyelectrolyte adsorption on this surface may preclude the use of these membranes in many applications. Here this work reports that native aliphatic polyamide Fujifilm type 1 cation-exchange membranes modified with protonated poly(allylamine) (PAH)/poly (4-styrenesulfonate) (PSS) films also show extremely high K + /Mg 2+ cation selectivities in ED with a single-membrane cell. Even with 0.1 M salt in the source phase, the K + /Mg 2+ selectivity is >1000. The very low transfer of divalent cations implies that the PEM forms a complete, continuous coating on the smooth Fujifilm surface. Moreover, for a membrane coated on both sides, the PEM on the anode side is responsible for most of the selectivity. However, the current efficiency is only ~0.6 for PAH/PSS-modified Fujifilm or Nafion membranes. Adsorption of highly water-swollen (PDADMAC/PSS) n films on Nafion membranes leads to high K + /Mg 2+ and Li + /Co 2+ selectivities in ED, and the monovalent cation current efficiency reaches 0.8.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Ecologically inspired metrics for transitioning to a sustainable and resilient circular economy with application to multilayer plastic films

Current Circular Economy (CE) frameworks applied to product chains exhibit notable shortcomings. These include neglecting the resilience and robustness of design, requiring detailed economic and environmental data for impact assessment, and relying on qualitative rather than quantitative metrics capturing certain CE design aspects. In the current contribution, we addressed these shortcomings by developing an Ecologically inspired (Eco-inspired) Framework using the mathematical foundations of Ecological Network Analysis (ENA). While ENA metrics have previously found application in designing circular economies, particularly in Industrial Symbiosis (IS) networks, our adaptation tailors these metrics for use in product-level CE, recognizing the inherent distinctions between product-level CE and IS. Our Eco-inspired Framework comprises three key categories to provide holistic and granular-level metrics for designing product-level CE. The first set of metrics assesses circularity and resource efficiency. The second set gauges network intensity and robustness as complementary indicators ensuring a CE is both sustainable and resilient. The third group of metrics evaluates enhancement potential of CE strategies through introducing quantitative metrics for measuring the degree of closed-loop strategies and average circularity level of a CE design. The three comprehensive set of indicators within the Eco-inspired Framework uniquely captures various facets of circular design, whether originating from technological innovations and recovery improvement at the end of life (EoL), shifts in human consumption patterns, alterations in product design, or changes in business models. The framework’s application is tested in designing a CE for multilayer Polyethylene-Polyamide (PE-PA) films. Using the Eco-inspired Framework, we identified the best strategy for designing a resilient and sustainable CE for PE-PA films. A diverse set of EoL strategies along with a reduction in product consumption can improve circularity and resilience by 650% and 255%, respectively, and mitigate greenhouse gas emissions by 90%. The framework minimizes trade-offs between sustainability and circularity goals and offers insights on how to enhance each strategy for achieving a resilient and sustainable CE for products.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Peridynamic Model for Microballistic Perforation of Multilayer Graphene

The peridynamic theory of solid mechanics is applied to the continuum modeling of the impact of small, high-velocity silica spheres on multilayer graphene targets. The model treats the laminate as a brittle elastic membrane. The material model includes separate failure criteria for the initial rupture of the membrane and for propagating cracks. Material variability is incorporated by assigning random variations in elastic properties within Voronoi cells. Here, the computational model is shown to reproduce the primary aspects of the response observed in experiments, including the growth of a family of radial cracks from the point of impact.

42 ENGINEERING↗
DOE OSTI2017

Manganoporphyrin-Polyphenol Multilayer Capsules as Radical and Reactive Oxygen Species (ROS) Scavengers

Local modulation of oxidative stress is crucial for a variety of biochemical events including cellular differentiation, apoptosis, and defense against pathogens. Currently employed natural and synthetic antioxidants exhibit a lack of biocompatibility, bioavailability, and chemical stability, resulting in limited capability to scavenge reactive oxygen species (ROS). To mediate these drawbacks, we have developed a synergistic manganoporphyrin-polyphenol polymeric nanothin coating and hollow microcapsules with efficient antioxidant activity and controllable ROS modulation. These materials are produced by multilayer assembly of a natural polyphenolic antioxidant, tannic acid (TA), with a synthesized copolymer of polyvinylpyrrolidone containing a manganoporphyrin modality (MnP-PVPON) which mimics the enzymatic antioxidant superoxide dismutase. The redox activity of the copolymer is demonstrated to dramatically increase the antioxidant response of MnP-PVPON/TA capsules versus unmodified PVPON/TA capsules through reduction of a radical cationic dye and to significantly suppress the proliferation of superoxide via cytochrome C competition. Inclusion of MnP-PVPON as an outer layer enhances radical-scavenging activity as compared to localization of the layer in the middle or inner part of the capsule shell. In addition, we demonstrate that TA is crucial for the synergistic radical-scavenging activity of the MnP-PVPON/TA system which exhibits a combined superoxide dismutase-like ability and catalase-like activity in response to the free radical superoxide challenge. The MnP-PVPON/TA capsules exhibit a negligible, 8% loss of shell thickness upon free radical treatment, while PVPON/TA capsules lose 39% of their shell thickness due to the noncatalytic free-radical-scavenging of TA, as demonstrated by small angle neutron scattering (SANS). Finally, we have found the manganoporphyrin-polyphenol capsules to be nontoxic to splenocytes from NOD mice after 48 h incubation. In conclusion, our study illustrates the strong potential of combining catalytic activity of manganoporphyrins with natural polyphenolic antioxidants to design efficient free-radical-scavenging materials that may eventually be used in antioxidant therapies and as free radical dissipating protective carriers of biomolecules for biomedical or industrial applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Variable Laser Ignition Pathways in Al/Pt Reactive Multilayers across 10 Decades of Pulse Duration

Pulsed laser irradiation is used to investigate the local initiation of rapid, self-propagating formation reactions in Al/Pt multilayers. The single pulse direct laser ignition of these 1.6 μm thick freestanding foils was characterized over 10 decades of pulse duration (10 ms to 150 fs). Finite element, reactive heat transport modeling of the near-threshold conditions has identified three distinct ignition pathways. For milli- to microsecond pulses, ignition occurs following sufficient absorption of laser energy to enable diffusion of Al and Pt between layers such that the heat released from the corresponding exothermic reaction overcomes conductive losses outside the laser-irradiated zone. When pulse duration is decreased into the nanosecond regime, heat is concentrated near the surface such that the Al locally melts, and a portion of the top-most bilayers react initially. The favorable kinetics and additional heat enable ignition. Further reducing pulse duration to hundreds of femtoseconds leads to a third ignition pathway. In this work, while much of the energy from these pulses is lost to ablation, the remaining heat beneath the crater can be sufficiently concentrated to drive a transverse self-propagating reaction, wherein the heat released from mixing at each interface occurs under kinetic conditions capable of igniting the subsequent layer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Strain-Modulated Exciton Localization and Enhanced Emission in Multilayer GaSe

Strain engineering is one of the most effective routes for tuning the electrical and optical properties of two-dimensional layered materials. Besides reproducing the results of other groups on the tunability and photoluminescence (PL) enhancement of free and bound excitons under mechanical deformation or thermal effects, we systematically studied the mechanical strain (wrinkle) and local thermal strain (laser heating) effects on the PL lifetime and polarization in GaSe multilayers and their interplay, revealing their coupled impact on excitonic dynamics. Here, the PL intensity of localized excitons in the wrinkle region of GaSe increases superlinearly with the excitation laser power. The polarization effect has been observed for the bound exciton in GaSe under mechanical strain, but not in GaSe under thermal strain. Fluorescence lifetime imaging (FLIM) measurements reveal strain-tunable lifetimes for both free and bound excitons, and the lifetime of the bound exciton is longer than the free exciton in the mechanical strain region, correlating with the enhanced emission of the bound exciton. These results highlight previously uncharacterized optoelectronic tunability in GaSe and broaden the design space for strain (or thermally)-controlled 2D layered devices.

, GaSe, Exciton localization↗
DOE OSTI2020

Thermodynamic Preference for Atom Adsorption on versus Intercalation into Multilayer Graphene

The thermodynamic preference of a foreign atom for adsorption on versus intercalation into a graphitic surface is of fundamental and widespread interest. From an exhaustive first-principles density functional theory investigation for 38 typical elements over the periodic table, we reveal a quasilinear correlation between the Shannon effective ionic radius and the chemical-potential difference for a single atom from adsorption to intercalation at multilayer graphene surfaces. A critical Shannon radius is found to be around 0.10 nm, below (above) which intercalation (adsorption) is more favorable for elements with ionic-like bonding after intercalation. Single atoms with van der Waals-biased bonding show some deviation from the linear relationship, while single atoms for the elements with covalent-like bonding do not favor intercalation relative to adsorption. An energy decomposition analysis indicates that the chemical-potential difference determining the thermodynamic preference of a foreign atom for adsorption versus intercalation results from the competition between the electronic and elastic strain effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Effects of fluid shear stress on polyelectrolyte multilayers by neutron scattering studies

The structure of layer-by-layer (LbL) deposited nanofilm coatings consists of alternating polyethylenimine (PEI) and polystyrenesulfonate (PSS) films deposited on a single crystal quartz substrate. LbL-deposited nanofilms were investigated by neutron reflectomery (NR) in contact with water in the static and fluid shear stress conditions. The fluid shear stress was applied through a laminar flow of the liquid parallel to the quartz/polymer interface in a custom-built solid–liquid interface cell. The scattering length density profiles obtained from NR results of these polyelectrolyte multilayers (PEM), measured under different shear conditions, showed proportional decrease of volume fraction of water hydrating the polymers. For the highest shear rate applied (ca. 6800 s –1 ) the water volume fraction decreased by approximately 7%. The decrease of the volume fraction of water was homogeneous through the thickness of the film. Since there were not any significant changes in the total polymer thickness, it resulted in negative osmotic pressures in the film. The PEM films were compared with the behavior of thin films of thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) deposited via spin-coating. The PEM and pNIPAM differ in their interactions with water molecules, and they showed opposite behaviors under the fluid shear stress. In both cases the polymer hydration was reversible upon the restoration of static conditions. Furthermore, a theoretical explanation is given to explain this difference in the effect of shear on hydration of polymeric thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Multilayer Noninteracting Dielectric Metasurfaces for Multiwavelength Metaoptics

Metasurfaces provide a versatile platform for manipulating the wavefront of light using planar nanostructured surfaces. Transmissive metasurfaces, with full 2π phase control, are a particularly attractive platform for replacing conventional optical elements due to their small footprint and broad functionality. However, the operational bandwidth of metasurfaces has been a critical limitation and is directly connected to either their resonant response or the diffractive dispersion of their lattice. While multiwavelength and continuous band operation have been demonstrated, the elements suffer from either low efficiency, reduced imaging quality, or limited element size. We propose a platform that provides for multiwavelength operation by employing tightly spaced multilayer dielectric metasurfaces. As a proof of concept, we demonstrate a multiwavelength metalens doublet (NA = 0.42) with focusing efficiencies of 38% and 52% at wavelengths of 1180 and 1680 nm, respectively. We further show how this approach can be extended to three-wavelength metalenses as well as a spectral splitter. This approach could find applications in fluorescent microscopy, digital imaging, and color routing.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Valley and Zeeman Splittings in Multilayer Epitaxial Graphene Revealed by Circular Polarization Resolved Magneto-infrared Spectroscopy

Circular-polarization-resolved magneto-infrared studies of multilayer epitaxial graphene (MEG) are performed using tunable quantum cascade lasers in high magnetic fields up to 17.5 T. Landau level (LL) transitions in the monolayer and bilayer graphene inclusions of MEG are resolved, and considerable electron–hole asymmetry is observed in the extracted electronic band structure. For monolayer graphene, a four-fold splitting of the $n$ = 0 to $n$ = 1 LL transition is evidenced and attributed to the lifting of the valley and spin degeneracy of the zeroth LL and the broken electron–hole symmetry. The magnetic field dependence of the splitting further reveals its possible mechanisms. The best fit to experimental data yields effective $g$-factors, $g^*_{vs}$ = 6.7 and $g^*_{ZS}$ = 4.8, for the valley and Zeeman splittings, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Time-Resolved Observation of Hole Tunneling in van der Waals Multilayer Heterostructures

We reported a time-resolved study of quantum-mechanical tunneling of holes between two MoSe 2 monolayers that are separated by a monolayer WS 2 energy barrier. Four-layer heterostructures of MoSe 2 /WS 2 /MoSe 2 /graphene, as well as control samples, were fabricated by mechanical exfoliation and dry transfer techniques. To time-resolve the hole tunneling process, an ultrashort laser pulse was used to excite electrons and holes in both MoSe 2 layers. Here, by utilization of the graphene layer to eliminate carriers in the third MoSe 2 layer, the first MoSe 2 layer is selectively populated with the holes, which then tunnel to the third MoSe 2 layer. By monitoring decay of the hole population with an ultrashort probe pulse, we measure a hole tunneling time of about 20 ps, which is found to slightly increase with the injected carrier density. Besides the fundamental interests of real-time observation of the quantum-mechanical tunneling effect across a nanometer barrier, these results provide quantitative understanding on tunneling mechanisms of charge transfer in van der Waals heterostructures, which is useful for designing sophisticated van der Waals multilayer heterostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Potential-Controlled Deposition of Multilayer CO 2 Reduction Catalyst Films onto Silicon Photoelectrodes Demonstrates Thickness-Dependent Catalytic Rates

Covalently attaching molecular catalysts to semiconductor surfaces yields promising hybrid photoelectrode architectures for reducing CO 2 to higher-value carbon products. Polymeric molecular catalyst films have higher loading densities than their monolayer counterparts, promising greater rates of solar fuel production. Using photoassisted diazonium electrografting, multilayered films of a Re(apbpy)(CO) 3 Cl CO 2 -reduction catalyst were attached to low-doped p-type Si (pSi). Parallel characterization of the newly formed films with ellipsometry, XPS, and ICP-MS revealed that catalyst loading increased with increasingly negative applied grafting potentials (Vgraft), providing us an experimental test bed to study the effects of film thickness on photocatalytic performance. Controlled-potential electrolysis experiments showed enhanced CO evolution rates on all photoelectrodes with increasingly negative applied potentials (V app ), with thicker films exhibiting the greatest rates of enhancement. Competitive proton reduction reactions at the Si surface were not strongly linked to V app but dependent on film thickness, with thicker films showing increased CO-to-H 2 production ratios.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Selective-Area Remote Epitaxy of ZnO Microrods Using Multilayer–Monolayer-Patterned Graphene for Transferable and Flexible Device Fabrications

Here, selective-area remote epitaxy (SA-REpi) is demonstrated for fabricating mechanically releasable position-controlled ZnO microrod (MR) arrays from donor wafers in an arrayed form. Intaglio-patterned graphene, consisting of basal single-layer graphene (SLG) overlayered with multilayer graphene (MLG) patterned with perforated holes, is transferred onto a GaN/Al 2 O 3 wafer on which the hydrothermal synthesis is performed for growing ZnO MRs. The basal SLG area exposed through the MLG pattern yields ZnO MRs, whereas the MLG plateau inhibits the growth. The noncovalent remote epitaxial heterointerface enables the release of the MR overlayer in the arrayed form, and the original source wafer is refurbished for reproducibly repeating the SA-REpi. Density-functional theory calculations suggest that localized surface charge density is induced on the surface of SLG by the underlying GaN across ultrathin SLG, which possibly provides a driving force for precursor adatoms and the following remote epitaxy of ZnO. In contrast, the induction of the charge density redistribution does not clearly occur through MLG; so, that keeps the surface of MLG nearly charge-neutral. The diameter and spacing of ZnO MRs are controlled in a designed way by changing the pattern geometries. High-resolution scanning transmission electron microscopy reveals the remote heteroepitaxial relationship at an atomic level. The remote epitaxy is expected to provide an ideal platform to transfer the addressable spatial arrays of nano- or micro-architecture semiconductor components to arbitrary target surfaces directly after the growth without the assembly procedures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Multilayered Cu-Carbon Nanotube Composites for Advanced Conductors

Improving the efficiency of electrical components is critical in reducing energy consumption for various industrial and residential applications, ranging from rotating machinery to all electric devices and electric vehicle (EV) components to power grid systems. Substituting Cu wires with reduced resistance conductors that incorporate carbon nanotubes (CNTs) into Cu─ultraconductive Cu (UCC) composites─has recently been considered a promising strategy to improve energy efficiency, power density, and/or performance across various applications. Here, in this study, we created stable material formulations [CNT-containing polyvinylpyrrolidone (PVP) in dimethylformamide (DMF) solution] and utilized commercially viable fabrication approaches (electrospinning and magnetron sputtering) that produced high-performance multilayered tape-based UCC composite architectures. Increasing the CNT volume fraction by sequential layering of the structure with additional Cu-CNT layers showed a nearly stepwise improved performance in electrical and mechanical properties. This study also provides valuable insight into the effectiveness of nitrogen doping in modifying the conductivity of the CNT matrix. Fabricated prototypes demonstrated a >10% increase in current carrying capacity and >10% improvement in mechanical strength compared to those obtained on pure Cu. We believe that the properties demonstrated here, combined with the scalable manufacturing pathway of our approach, pave the way in designing future advanced conductors for diverse energy efficient and high-performance electrical systems and applications.

Carbon nanotubes↗
DOE OSTI2022

Multilayer Chitin–Chitosan–Cellulose Barrier Coatings on Poly(ethylene terephthalate)

Currently, effective barrier properties over a wide range of humidity are achieved by layering multiple plastics, resulting in structures that are nearly impossible to recycle through current systems. There is strong interest in developing barriers that are recyclable, biodegradable, or compostable. Chitin and cellulose nanomaterials are promising alternatives because of their high crystallinity, renewable sourcing, strong electrostatic interactions, and potential for biodegradation or composting. In this paper, we explore the potential to create multilayer materials with effective oxygen and water vapor barrier properties at elevated humidity by combining recyclable poly(ethylene terephthalate) (PET) films with single-layer and bilayer coatings of chitin nanowhiskers (ChNWs), chitosan (CS), and cellulose nanocrystals (CNCs). The addition of CS to the ChNW suspension improved the gas barrier properties of ChNW coatings, likely by filling voids, and short ChNWs (SChNW, 114 nm) performed better than long ChNWs (LChNW, 230 nm). At the optimal mass ratio of 1:1 SChNW/CS, the oxygen permeability (OP) of SChNW/CS-coated PET films was 5.1 cm 3 μm m –2 day –1 kPa –1 versus 15.9 cm 3 μm m –2 day –1 kPa –1 for neat PET. To take advantage of electrostatic attraction and hydrogen bonding, CNC was first coated on the PET, followed by coating with ChNW/CS, resulting in an OP as low as 3.6 cm 3 μm m –2 day –1 kPa –1 at 50% relative humidity (RH), and 6.4 cm 3 μm m –2 day –1 kPa –1 at 80% RH. Furthermore, after thermal treatment (120 °C, 2.5 h), the OP dropped to 2.2 cm 3 μm m –2 day –1 kPa –1 (50% RH) and 4.8 cm 3 μm m –2 day –1 kPa –1 (80% RH). The ChNW/CS and CNC coating can be efficiently removed with alkali treatment enabling possible recycling of the coated PET films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗