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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Tethered satellite system

The Tethered Satellite System (TSS) will operate from the Space Shuttle as an earth-orbiting facility that will permit tethered deployment of numerous types of payloads to altitudes both above and below that of the Shuttle. The TSS has evolved from initial studies, beginning in the sixties, to a cooperative development program that is currently being carried out by NASA and the National Space Plan of Italy's CNR. This cooperative agreement between NASA and CNR includes system development and science instrumentation for the first mission, and planning for two additional missions. This paper will (1) discuss predevelopment activities, (2) review the development approach and management relationships between NASA and CNR, (3) describe the current hardware/software configuration and functional interfaces, (4) discuss the mission profile and flight operations planning, and (5) overview science experiment status/plans for the first TSS mission.

Laue, Jay H.↗
DOE OSTI2026

Photoresponsive Rotaxanes Switch Lipid Bilayer Neuromorphic Behavior with Light

A rotaxane consisting of a macrocycle ring with two azobenzene units mechanically interlocked onto a bolaamphiphilic axle was incorporated into droplet interface bilayers (DIBs). The azobenzene groups on the ring underwent quasi-reversible, photoisomerization-induced cycling between 1-E and 1-Z configurations when irradiated with 370 and 467 nm light, respectively, enabling programmable access to different history-dependent electrical behaviors from the same membrane. In the 1-E configuration, bilayers exhibited type-IIactive memristance that coincided with increasingly elevated ionic conduction, associated with progressively enhanced bilayer permeability during voltage cycling. In the 1-Z configuration, bilayers displayed type-I, passive memcapacitive behavior, reflecting tighter lipid packing and reduced ionic permeability. Photoswitching also yielded a nonvolatile, photoresponsive memcapacitor that could be modulated repetitively with negligible loss, likely via reversible changes in membrane thickness. Concurrent ohmic leakage currents across the membrane were less than 0.3%. These results agree with previous studies with increasing membrane permeability using photoswitchable rotaxanes and provide new insights into the coupling between volatile and nonvolatile memcapacitance during photoisomerization. More broadly, they demonstrate a new strategy for the manipulation of neuromorphic behaviors in soft materials using light, with implications for brain-inspired computation and sensing.

droplet interface bilayers↗
DOE OSTI2025

Nanometer Resolution Structure‐Emission Correlation of Individual Quantum Emitters via Enhanced Cathodoluminescence in Twisted Hexagonal Boron Nitride

Understanding the atomic structure of quantum emitters, often originating from point defects or impuritie, is essential for designing and optimizing materials for quantum technologies such as quantum computing, communication, and sensing. Despite the availability of atomic-resolution scanning transmission electron microscopy and nanoscale cathodoluminescence microscopy, experimentally determining the atomic structure of individual emitters is challenging due to the conflicting needs for thick samples to generate strong cathodoluminescence signals and thin samples for structural analysis. To overcome this challenge, significantly enhanced cathodoluminescence at twisted interfaces is leveraged to achieve sub-nanometer localization precision for the first time in mapping individual quantum emitters in carbon-implanted hexagonal boron nitride. This unprecedent spatial sensitivity, together with correlative electron energy loss spectroscopy quantitative scanning transmission electron microscopy imaging, and first principles density functional theory calculations, enables the identification of the atomic structure of the 440 nm blue emitter in hexagonal boron nitride as a substituted vertical carbon dimer. Building on the atomic structure insights, nanoscale spatially precise creation of blue emitters is demonstrated by electron beam irradiation of carbon-coated hexagonal boron nitride. This advancement in correlating atomic structures with optical properties lays the foundation for a deeper understanding and precise engineering of quantum emitters, significantly advancing the development of cutting-edge quantum information technologies.

2D material↗
DOE OSTI2019

Thermal Conductivity of Thermal Interface Materials Evaluated By a Transient Plane Source Method

The thermal conductivity of thermal interface materials (TIMs) has been investigated using a transient plane source (TPS) method. In thermoelectric generators designed for vehicle waste heat recovery, high thermal conductivity materials are needed for the cold-side interface between a polyamide flexible circuit and an aluminum plate heat exchanger. The conventional heat flow method described by ASTM D5470 is often used to determine thermal contact resistance of an interface with a thin layer of interface material. The apparent thermal conductivity values provided by materials manufacturers are used to calculate heat transfer through the interface. Yet, estimated parameters based on the thermal conductivity of a TIM often do not agree with the actual heat transfer through the interface. Thermal conductivity of a series of 10 commercial TIMs were evaluated by applying a small quantity to an embedded TPS sensor. The 2-mm radius sensor was able to operate under standard bulk material measurement mode and produced consistent thermal conductivity measurements of the interface materials. The TPS method is demonstrated to be effective in ranking the available interface materials by thermal conductivity and to ensure that the material with consistent performance can be selected for the thermoelectric generator applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

TH-AB-BRA-03: Backscatter Dose Factors Re-Evaluated for Inhomogeneities in the Presence of a 1.5 T Magnetic Field Using the GPUMCD Monte Carlo Algorithm

Purpose: To quantify the backscatter dose factors near the interfaces for clinically relevant high atomic number materials using GPUMCD for the Elekta MRI Linac. Methods: Backscatter dose factors (BSDF) were calculated as the ratio of the dose with and without the presence of the heterogeneity. The BSDF’s were calculated either in the absence or presence of an orthogonal 1.5 T magnetic field. Doses were scored in small voxels of side 1 mm in a water phantom with dimensions of 20×20×20 cm using GPUMCD (Elekta). The minimum uncertainty in dose calculations was kept to 0.5%. A slab of thickness 2 cm, representing the inhomogeneity, was placed inside the phantom with variable position from the surface of the phantom. The slab was filled with either bone, aluminum, titanium, stainless steel, or dental amalgam. The phantom was irradiated using particles sampled from a histogram which represented the true MRI Linac spectrum. Results: With the application of the 1.5 T magnetic field (B-On), all of the BSDF’s were reduced by at least 8% compared to the no magnetic field (B-Off) cases. For the B-Off case, the BSDF decreases exponentially with the upstream distance away from the interface. With B-On, the BSDF decreases exponentially for titanium, SS, and amalgam. However, it remains constant for Aluminum. In the case of bone, the BSDF increases up to a distance of 4 mm away from the interface in the presence of the magnetic field. Conclusion: The BSDF does not depend upon the thickness of the homogeneous material above the inhomogeneity for either the B-Off or B-On cases. For all the materials investigated, the BSDF is lower at the interface for the B-On case. The exponential fall-off of the BSDF away from the interface is not valid for all the materials when the magnetic field is turned ON. Funding support for this research was provided by Elekta.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

A cluster deposition method was used to produce films of loosely aggregated nanoclusters (NCs) of Fe core-Fe{sub 3}O{sub 4} shell or fully oxidized Fe{sub 3}O{sub 4}. Films of these NC on Si(100) or MgO(100)/Fe{sub 3}O{sub 4}(100) were irradiated to 10{sup 16} Si{sup 2+}/cm{sup 2} near room temperature using an ion accelerator. Ion irradiation creates structural change in the NC film with corresponding chemical and magnetic changes which depend on the initial oxidation state of the cluster. Films were characterized using magnetometry (hysteresis, first order reversal curves), microscopy (transmission electron, helium ion), and x-ray diffraction. In all cases, the particle sizes increased due to ion irradiation, and when a core of Fe is present, irradiation reduces the oxide shells to lower valent Fe species. These results show that ion irradiated behavior of the NC films depends strongly on the initial nanostructure and chemistry, but in general saturation magnetization decreases slightly.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Variation of the Passive Film on Compositionally Concentrated Dual-Phase Al 0.3 Cr 0.5 Fe 2 Mn 0.25 Mo 0.15 Ni 1.5 Ti 0.3 and Implications for Corrosion

The passive film on a dual-phase Al 0.3 Cr 0.5 Fe 2 Mn 0.25 Mo 0.15 Ni 1.5 Ti 0.3 FCC + Heusler (L2 1 ) compositionally concentrated alloy formed during extended exposure to an applied potential in the passive range in dilute chloride solution was characterized. Each phase, with its own distinct composition of passivating elements, formed unique passive films separated by a heterophase interface. High-resolution, surface sensitive characterization enabled chemical analysis of the passive film formed over individual phases. The film formed over the L2 1 phase had a higher concentration of Al, Ni, and Ti, while the film formed over FCC phase was of similar thickness but contained comparatively higher Cr, Fe, and Mo concentrations, consistent with the differences in bulk microstructure composition. The passive film was continuous across phase boundaries and the distribution of passivating elements (Al, Cr, and Ti) indicated both phases were independently passivated. Spatially resolved analysis of the surface chemistry of the dual-phase CCA revealed that the cation with the highest composition in passive film formed on the FCC phase was Cr (52.4 at. pct) and for the L2 1 phase was Ti (53.1 at. pct) despite the bulk concentration of each element being below 20 at. pct in their respective phases. Al, Cr, and Ti were enriched in both phases within the passive film relative to their respective bulk compositions. In parallel studies, single-phase alloys with compositions representative of the FCC and L2 1 phases were synthesized to evaluate the corrosion behavior of each phase in isolation. The corrosion behavior of the dual-phase alloy showed passivity evidenced by a pitting potential of 0.615 V SCE in 0.01 M NaCl. The pitting potential and other electrochemical parameters suggested a combination of behaviors of both single-phase samples, suggesting that the global corrosion behavior may be represented by a composite theory applied to phases, their area fractions, and interphase length. However, the interphase in the dual-phase CCA was a local corrosion initiation site and may limit localized corrosion protectiveness. The alloy design implications for optimization of second phase structure and morphology are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Sizing of discontinuous natural fibers: Effect of sizing approach and sizing concentration on composite properties

Natural fiber reinforced composites (NFRCs) are gaining attention in automotive applications as an alternative to glass fiber composites due to their lightweight and renewable sourcing. However, the inherent hydrophilicity of natural fibers leads to poor compatibility with hydrophobic polymers which adversely affects the mechanical properties of the composites and can limit their application to non-structural parts. Sizing is a common approach used for synthetic fibers to improve the interface between fiber and matrix. However, there is limited study on the sizing of natural fibers, and hence the focus of this work. Here, in this study, two different approaches to sizing discontinuous coir fibers were investigated, namely; (1) ex-situ sizing and (2) in-situ sizing. A commercial polypropylene (PP) based sizing agent was used and the effects of varying sizing solution concentrations (1.5, 2.5, and 3.5 wt%) on the properties of the composites was studied. Results showed that composites prepared via the in-situ sizing process had better fiber–matrix adhesion and improved tensile properties compared to ex-situ sized composites. On studying the effect of different sizing concentrations on composite properties, we found that the tensile strength of the composites increased (by ∼ 42 %) up to 2.5 wt% sizing concentration (in solution) and then decreased. However, the impact strength decreased significantly on increasing the sizing content beyond 1.5 wt% (by ∼ 40 %). Additionally, the study was further extended to investigate the effect of sizing on different NFRCs (coir, banana, and cottonized hemp fiber) where effectiveness of sizing was found to be influenced by the fiber surface morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Microstructural characterization and mechanical properties of high power ultrasonic spot welded aluminum alloy AA6111–TiAl6V4 dissimilar joints

Aluminum alloy AA6111 and TiAl6V4 dissimilar alloys were successfully welded by high power ultrasonic spot welding. No visible intermetallic reaction layer was detected in as-welded AA6111/TiAl6V4 welds, even when transmission electron microscopy was used. The effects of welding time and natural aging on peak load and fracture energy were investigated. The peak load and fracture energy of welds increased with an increase in welding time and then reached a plateau. The lap shear strength (peak load) can reach the same level as that of similar Al–Al joints. After natural aging, the fracture mode of welds transferred from ductile fracture of the softened aluminum to interfacial failure due to the strength recovery of AA6111. - Highlights: • Dissimilar Al/Ti welds were produced by high power ultrasonic spot welding. • No visible intermetallic reaction layer was detected on weld interface. • The lap shear strength can reach the same level as that of similar Al–Al joints. • The fracture mode becomes interfacial failure after natural aging.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Current-Assisted Diffusion Bonding of Extruded Ti-22Al-25Nb Alloy by Spark Plasma Sintering: Interfacial Microstructure and Mechanical Properties

Spark plasma sintering (SPS) technology was used to current-assisted bond extruded Ti-22Al-25Nb alloy. The effects of bonding temperature (920-980 °C) and bonding time (10-30 min) on the microstructure evolution and shear strength of this alloy were investigated systematically. The temperature distribution in the specimen during the current-assisted bonding process was also analyzed by numerical simulation. It is noted that the highest temperature was obtained at the bonding interface. As the bonding temperature and bonding time increased, the voids in the interface shrank increasingly until they vanished. A complete metallurgical bonding interface could be produced at 960 °C/20 min/10 MPa, exhibiting the highest shear strength of 269.3 MPa. In addition, the shear strength of the bonded specimen depended on its interfacial microstructure. With increased bonding temperature, the fracture mode transformed from the intergranular fracture at the bonding interface to the cleavage fracture in the substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The evolution of orientation relationships during the transformation of a twin-free T-particle to tenfold T-twins in an Al alloy during homogenisation

Highlights: • The ORs of T-phase change continuously during its transformation to tenfold twins. • The changes in ORs are achieved by lattice rotations of T-phase about [010]{sub T} axis. • The OR change of T-phase exhibits a relationship with its cross-section shape. • The OR change of T-phase reduce the interface misfit increased by newly-formed twins. • Rotation of T-particle requires coordinate deformation at the near-interface region. - Abstract: The crystallographic and morphological analysis of T-phase formation in Al alloys was investigated using high-resolution electron microscopy (HRTEM) and selected-area electron diffraction pattern (SAEDP). The results show that the orientation relationships (ORs) of the T-phase change continuously from its original ORs during the transformation of a twin-free T-particle to the tenfold T-twins. These OR changes were achieved by lattice rotations of T-twin domains (T-TDs) about the [010]{sub T}//[010]{sub Al} axis by an angle ranging from 0° to 9°, and this exhibits a relationship with the shape of the cross-sections of the T-phase (T-CSs). The changes in ORs of the T-phase can reduce the increase in interface misfit between the newly-formed T-TDs and the Al matrix. The matrix could only accommodate the rotation of a T-particle at the near-interface region at relatively high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Outgassing of implanted He via short circuit transport along phase and grain boundaries in vapor co-deposited Cu-W nanocomposites

We investigate the response of physical vapor co-deposited copper (Cu)-tungsten (W) nanocomposites to helium (He) implantation. Nuclear reaction analysis (NRA) reveals that a substantial fraction of He implanted into these materials escapes during implantation. Analysis of nanocomposite microstructure shows that the He loss is likely due to its transport out of the material by diffusion along phase and grain boundaries. Lastly, our findings suggest that solid-state interfaces such as phase and grain boundaries are short circuit diffusion pathways for transport of He.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Infusion of hydrogen into nanostructured bainitic steel

Highlights: • Results show that austenite is more effective in trapping hydrogen than α/γ interfaces. • The H desorption behaviour was accurately reproduced with local equilibrium model. • The trapping capacity of retained austenite originates from the austenite lattice sites. - Abstract: The trapping of hydrogen in nanostructured bainitic steel has been investigated using thermal desorption analysis, in order to determine the potency of the ferrite-retained austenite (α/γ) interfaces and retained austenite as trapping sites. Thermal desorption data showed that the volume of retained austenite is more effective in trapping hydrogen than the interfaces. There is a close correlation between the quantity of hydrogen and the retained austenite content rather than the density of interfaces. A local equilibrium model was able to reproduce the hydrogen desorption behaviour of saturated and unsaturated samples considering both retained austenite and α/γ interfaces as the trapping sites. A trap binding energy ranging from 47 to 52 kJ/mol was estimated for retained austenite, suggesting that the observed trapping capacity originates from the austenite lattice sites.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Investigation of radiation damage tolerance in interface-containing metallic nano structures

The proposed work seeks to conduct a basic study by applying experimental and computational methods to obtain quantitative influence of helium sink strength and proximity on He bubble nucleation and growth in He-irradiated nano-scale metallic structures, and the ensuing deformation mechanisms and mechanical properties. We utilized a combination of nano-scale in-situ tension and compression experiments on low-energy He-irradiated samples combined with site-specific microstructural characterization and modeling efforts. We also investigated the mechanical deformation of nano-architected materials, i.e. nanolattices which are comprised of 3-dimensional interwoven networks of hollow tubes, with the wall thickness in the nanometer range. This systematic approach will provide us with critical information for identifying key factors that govern He bubble nucleation and growth upon irradiation as a function of both sink strength and sink proximity through an experimentally-confirmed physical understanding. As an outgrowth of these efforts, we performed irradiations with self-ions (Ni 2+ ) on Ni-Al-Zr metallic glass nanolattices to assess their resilience against radiation damage rather than He-ion implantation. We focused our attention on studying individual bcc/fcc interfaces within a single nano structure (nano-pillar or a hollow tube): a single Fe (bcc)-Cu (fcc) boundary per pillar oriented perpendicular to the pillar axes, as well as pure bcc and fcc nano structures. Additional interfaces of interest include bcc/bcc and metal/metallic glass all within a single nano-structure volume. The model material systems are: (1) pure single crystalline Fe and Cu, (2) a single Fe (bcc)-Cu (fcc) boundary per nano structure (3) a single metal–metallic glass, all oriented non-parallel to the loading direction so that their fracture strength can be tested. A nano-fabrication approach, which involves e-beam lithography and templated electroplating, as well as two-photon lithography, was utilized, which enabled precise control of the initial microstructure control. Experimentally determined stress-strain relationships were enhanced by in-situ SEM observations coupled with TEM microstructural characterization of the same samples before and after deformation (irradiated and as-fabricated) and atomistic (MD) modeling. A comprehensive suite of experiments was conducted to quantitatively assess the key parameters for He bubble nucleation and growth by independently varying the sink strength, sink proximity, and He implantation temperature and dose. The implantations were conducted at Sandia and Los Alamos National Labs (CINT). Nano structuress containing He-enriched interfaces and irradiation-damaged microstructure were tested under uniaxial tension to assess embrittlement, resulting boundary strength, and deformation mechanisms. Results of this work helped identify which types of interfaces are particularly resilient against radiation damage.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Band offsets of La{sub 2}O{sub 3} on (0001) GaN grown by reactive molecular-beam epitaxy

La{sub 2}O{sub 3} films were prepared on (0001)-oriented GaN substrates via reactive molecular-beam epitaxy. Film orientation and phase were assessed using reflection high-energy electron and X-ray diffraction. Films were observed to grow as predominantly hexagonal La{sub 2}O{sub 3} for thicknesses less than 10 nm while film thickness greater than 10 nm favored mixed cubic and hexagonal symmetries. Band offsets were characterized by X-ray photoelectron spectroscopy on hexagonally symmetric films and valence band offsets of 0.63 {+-} 0.04 eV at the La{sub 2}O{sub 3}/GaN interface were measured. A conduction band offset of approximately 1.5 eV could be inferred from the measured valence band offset.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The role of Mg interface layer in MgO magnetic tunnel junctions with CoFe and CoFeB electrodes

The tunneling spin polarization (TSP) is directly measured from reactively sputter deposited crystalline MgO tunnel barriers with various CoFe(B) compositions using superconducting tunneling spectroscopy. We find that the Mg interface layer thickness dependence of TSP values for CoFeB/Mg/MgO junctions is substantially different from those for CoFe/Mg/MgO especially in the pre-annealed samples due to the formation of boron oxide at the CoFeB/MgO interface. Annealing depletes boron at the interface thus requiring a finite Mg interface layer to prevent CoFeOx formation at the CoFeB/MgO interface so that the TSP values can be optimized by controlling Mg thickness.

36 MATERIALS SCIENCE↗
DOE OSTI2018

An unusual type of polymorphism in a liquid crystal

Polymorphism is a remarkable concept in chemistry, materials science, computer science, and biology. Whether it is the ability of a material to exist in two or more crystal structures, a single interface connecting to two different entities, or alternative phenotypes of an organism, polymorphism determines function and properties. In materials science, polymorphism can be found in an impressively wide range of materials, including crystalline materials, minerals, metals, alloys, and polymers. Here in this paper we report on polymorphism in a liquid crystal. A bent-core liquid crystal with a single chiral side chain forms two structurally and morphologically significantly different liquid crystal phases solely depending on the cooling rate from the isotropic liquid state. On slow cooling, the thermodynamically more stable oblique columnar phase forms, and on rapid cooling, a not heretofore reported helical microfilament phase. Since structure determines function and properties, the structural color for these phases also differs.

36 MATERIALS SCIENCE↗