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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials

Low-symmetry 2D materials—such as ReS 2 and ReSe 2 monolayers, black phosphorus monolayers, group-IV monochalcogenide monolayers, borophene, among others—have more complex atomistic structures than the honeycomb lattices of graphene, hexagonal boron nitride, and transition metal dichalcogenides. The reduced symmetries of these emerging materials give rise to inhomogeneous electron, optical, valley, and spin responses, as well as entirely new properties such as ferroelasticity, ferroelectricity, magnetism, spin-wave phenomena, large nonlinear optical properties, photogalvanic effects, and superconductivity. Novel electronic topological properties, nonlinear elastic properties, and structural phase transformations can also take place due to low symmetry. Lastly, the “Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials” Special Topic was assembled to highlight recent experimental and theoretical research on these emerging materials.

2D materials↗
DOE OSTI2024

Iron dopant energy levels in β-Ga 2 O 3

The energetic positions of the two Fe dopant levels in the bandgap of β-Ga 2 O 3 are determined to be at 3.05(±0.05) and 3.85(±0.05) eV below the conduction band minimum from transmission measurements employing a sub-picosecond tunable ultraviolet laser radiation source. A further measurement of the quantum efficiency of photoelectron emission from the Fe:Ga 2 O 3 (010) photocathode is consistent with the obtained absorption data and a dominant optical phonon assisted Franck–Condon emission mechanism, while also providing an estimate of 100 ps for the conduction band electron lifetime.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1997

Scientific Applications of Optical Instruments to Materials Research

Microgravity is a unique environment for materials and biotechnology processing. Microgravity minimizes or eliminates some of the effects that occur in one g. This can lead to the production of new materials or crystal structures. It is important to understand the processes that create these new materials. Thus, experiments are designed so that optical data collection can take place during the formation of the material. This presentation will discuss scientific application of optical instruments at MSFC. These instruments include a near-field scanning optical microscope, a miniaturized holographic system, and a phase-shifting interferometer.

Witherow, William K.↗
DOE OSTI2020

Substrate-Dependent Band Structures in Trilayer Graphene / h - BN Heterostructures

The tight-binding model has been spectacularly successful in elucidating the electronic and optical properties of a vast number of materials. Within the tight-binding model, the hopping parameters that determine much of the band structure are often taken as constants. Here, using ABA-stacked trilayer graphene as the model system, we show that, contrary to conventional wisdom, the hopping parameters and therefore band structures are not constants, but are systematically variable depending on their relative alignment angle between h-BN. Moreover, the addition or removal of the h-BN substrate results in an inversion of the K and K' valley in trilayer graphene’s lowest Landau level. Our work illustrates the oft-ignored and rather surprising impact of the substrates on band structures of 2D materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Emerging Functionality in Transition-Metal Compounds Driven by Spatial Confinement and Broken Symmetry

This research project investigates the emerging functionality in transition-metal-compounds (TMCs) driven by spatial confinement and broken symmetry. It combines advanced growth capabilities with cutting-edge characterization and first principles theory to probe and control the properties of TMC interfaces, including the utilization and development of state-of-the-art atomically resolved electron microscopy and spectroscopy to determine the structure, composition, and bonding at TMC interfaces. The proposed research will focus on four challenging areas: 1) manipulate interfaces to design new material phases such as magnetic metals with unique polar structure (net dipole) to achieve multiple functionality; 2) explore electronic mismatch or screening at interfaces of insulating/poor metal TMCs to produce novel electronic and magnetic properties; 3) elucidate and exploit the role of defects, both point and extended, on the functionality of interfaces; 4) develop advanced electron microscopy/spectroscopy techniques to explore temperature dependent phase transitions and couple these structural tools with new nonlinear optical probes of the electronic structure. The research team aims to close the materials-by-design loop of make, measure, model, and modify. The program promises to enhance our ability to engineer the desired physical properties at interfaces, superlattices (periodic arrays of films of different compounds), and heterostructures of TMCs.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Computational investigations of Dienes defect- and vacancy-induced changes in the electronic and vibrational properties of carbon fiber structural units

Carbon fiber (CF) is a promising lightweight alternative to steel and is of significant interest for energy applications. As CF continues to find new uses and is exposed to new external conditions, a noninvasive method of monitoring its structural integrity is critical. Raman spectroscopy is a commonly used method for this monitoring; however, it is highly inferential, and the interpretation of the data is not always straightforward. In this work, we perform density functional theory (DFT) calculations to investigate changes in the vibrational properties of CF structural units (i.e., graphene and graphite) caused by monovacancy and Dienes defects as a foundation for modeling more complex defects that move our model toward that of realistic CF. Using large computational supercells, we can understand how these defects change the electronic structure and vibrational properties of graphene and graphite for interdefect distances near those of the lower experimental limit. The monovacancy opens an electronic bandgap at the K point. Although no such electronic gap is opened by the Dienes defect, both defects introduce flat defect bands near the Fermi energy. The Dienes defect creates long-range deviations of the phonons, leading to substantial broadening of the highest frequency optical modes in the band structure compared to that of the pristine material. In contrast, the phonon changes caused by the monovacancy are short range, and only minor changes in the band structure or phonon density of states were observed. These findings can assist in the interpretation of experimental results by providing atomic-scale insight into key electronic and vibrational features.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Large Deployable Reflector (LDR) system concept and technology definition study. Volume 1: Executive summary, analyses and trades, and system concepts

A study was conducted to define reasonable and representative large deployable reflector (LDR) system concepts for the purpose of defining a technology development program aimed at providing the requisite technological capability necessary to start LDR development by the end of 1991. This volume includes the executive summary for the total study, a report of thirteen system analysis and trades tasks (optical configuration, aperture size, reflector material, segmented mirror, optical subsystem, thermal, pointing and control, transportation to orbit, structures, contamination control, orbital parameters, orbital environment, and spacecraft functions), and descriptions of three selected LDR system concepts. Supporting information is contained in appendices.

Agnew, Donald L.↗
NASA NTRS1993

Establishment of computerized numerical databases on thermophysical and other properties of molten as well as solid materials and data evaluation and validation for generating recommended reliable reference data

The Center for Information and Numerical Data Analysis and Synthesis, (CINDAS), measures and maintains databases on thermophysical, thermoradiative, mechanical, optical, electronic, ablation, and physical properties of materials. Emphasis is on aerospace structural materials especially composites and on infrared detector/sensor materials. Within CINDAS, the Department of Defense sponsors at Purdue several centers: the High Temperature Material Information Analysis Center (HTMIAC), the Ceramics Information Analysis Center (CIAC) and the Metals Information Analysis Center (MIAC). The responsibilities of CINDAS are extremely broad encompassing basic and applied research, measurement of the properties of thin wires and thin foils as well as bulk materials, acquisition and search of world-wide literature, critical evaluation of data, generation of estimated values to fill data voids, investigation of constitutive, structural, processing, environmental, and rapid heating and loading effects, and dissemination of data. Liquids, gases, molten materials and solids are all considered. The responsibility of maintaining widely used databases includes data evaluation, analysis, correlation, and synthesis. Material property data recorded on the literature are often conflicting, diverging, and subject to large uncertainties. It is admittedly difficult to accurately measure materials properties. Systematic and random errors both enter. Some errors result from lack of characterization of the material itself (impurity effects). In some cases assumed boundary conditions corresponding to a theoretical model are not obtained in the experiments. Stray heat flows and losses must be accounted for. Some experimental methods are inappropriate and in other cases appropriate methods are carried out with poor technique. Conflicts in data may be resolved by curve fitting of the data to theoretical or empirical models or correlation in terms of various affecting parameters. Reasons (e.g. phase transitions) must be found for unusual dependence or any anomaly. Such critical evaluation involves knowledge of theory, experience in measurement, familiarity with metallurgy (microstructural behavior) and not inconsiderable judgment. An examination of typical data compiled and analyzed by CINDAS shows that the thermal conductivity of a material reported in the literature may vary by a factor of two of more; the range of reported values increases as temperature increases reflecting the difficulty of high temperature measurements. Often only estimates of melt behavior are available, despite the importance of melt properties in modeling, welding, or other solidification processes. There may be only a few measurements available for properties such as kinematic viscosity, even for widely used materials such as stainless steel. In the face of such a paucity of existing data and in a national environment where too few new data are being generated it is nonetheless the responsibility of CINDAS to select and disseminate recommended values of a wide variety of thermophysical properties.

Ho, C. Y.↗
NASA NTRS2003

An Examination of Issues Related to a Europa Subsurface Component for the JIMO Mission

The Galileo Europa data set served to revolutionize our view of Europa. In particular the strong evidence of a large, cold, salty Ocean beneath 5-30 km of ice has profoundly altered the significance of Europa in our thinking, especially of context of habitability in the solar system. While much remains to be learned from spacecraft observations of several sorts, there are significant questions answerable only by in-situ techniques; these relate to the formation of Europa, the nature of its ocean, and the prospects for life in its ocean, sediments, and ice. We feel that wide-ranging discussion of an in-situ subsurface mission to Europa, as part of JIMO, should proceed. The science objective of the mission is to characterize the icy shell of Europa to resolve its provenance, estimate the composition of brine of the Europa ocean, and search for evidence of Earth-like life. Probably anyone would agree that an in-situ mission to Europa would be of great value, but he or she would also immediately take the position that such a mission is utterly impractical. We take the position here of defining the least complex mission that can nonetheless justify its cost and to argue that such a mission is realistic enough that it should be seriously considered. Our mission thinking has been: 1) Soft landing. A soft lander is required on a site sufficiently flat to offer a stable platform; no further site selectivity is required. 2) Subsurface exploration. The Europa subsurface must be examined. Surficial processes on Europa arguably have exposed the upper 200 m of shell to chemical effects from the Jovian radiation belts as well as cometary infall, etc; to examine native ice we must descend below that point to, for discussion, 300 m. At that depth we argue that the ice is characteristic of ice at depth and possibly is effectively sea ice. 3) Science data. A few simple measurements at various depths and at 300 m constitute a scientifically successful mission. Measurements would include analysis of meltwater for a few inorganic ions and amino acids and an optical examination of the borehole wall. 4) Communication. Transmission of data to an orbiter is essential, but we will constrain the landed mission to a daily communication over a few days. 5) Subsurface access. Drilling to 300 m is a significant challenge; it can be addressed by several means: Thermal Probe (Cryobot) which permits water to refreeze above the vehicle. This is our tentative choice with plutonium as the fuel to generate thermal energy for drilling and electrical power for operations. Open Hole Drill, a thermal system in which the meltwater is removed for greater thermal efficiency. Meltwater removal on Europa is both a complexity and a risk, but analysis is improved. Mechanical Drilling in which cutting or grinding generates ice chips which are removed. This is too complex at Europa temperatures. The measurement objectives for the mission will be: Obj. 1: Determine the concentration of simple inorganic salts in the Europa Ice Shell and, by extrapolation, of the ocean. These data will also validate spaceborne sensors. Obj. 2: Determine the nature and abundance of amino acids in the ice such that cometary infall material in the upper ice can be compared to material at depth. Obj. 3: Optically examine the ice to resolve inclusion structure, particulate content, and stratification. Access to 300 m depth is a significant if not audacious plan; we are aware that this has not been done on any planetary body. Our approach is the use of a plutonium heat source; to overcome Europa's surface temperature and to melt ice a significant amount of plutonium is needed, and significant shielding and other protective steps will be required. The quantity of plutonium is a key concern. The mission will require subsurface collection and processing of samples for in situ analysis, calling for a miniature, high pressure micro-sampling system designed to meet needs of instruments that require low presses for operation. The inlet system itself collects a micro-sample in the external high pressure environment, then transfers it into a protected low pressure environment for analysis.

Carsey, F. D.↗
NASA NTRS2004

Thermally Stable Heterocyclic Imines as New Potential Nonlinear Optical Materials

In the course of a search for new thermostable acentric nonlinear optical crystalline materials, several heterocyclic imine derivatives were designed, with the general structure D-pi-A(D'). Introduction of a donor amino group (D') into the acceptor moiety was expected to bring H-bonds into their crystal structures, and so to elevate their melting points and assist in an acentric molecular packing. Six heterocycle-containing compounds of this type were prepared, single crystals were grown for five of them, and these crystals were characterized by X-ray analysis. A significant melting temperature elevation was found for all of the synthesized compounds. Three of the compounds were also found to crystallize in acentric space groups. One of the acentric compounds is built as a three-dimensional H-bonded molecular network. In the other two compounds, with very similar molecular structure, the molecules form one-dimensional H-bonded head-to-head associates (chains). These chains are parallel in two different crystallographic directions and form very unusual interpenetrating chain patterns in an acentric crystal. Two of the compounds crystallized with centrosymmetric molecular packing.

Nesterov, Volodymyr V.↗
NASA NTRS2006

Molecular Substrate Alteration by Solar Wind Radiation Documented on Flown Genesis Mission Array Materials

The Genesis spacecraft sampling arrays were exposed to various regimes of solar wind during flight that included: 313.01 days of high-speed wind from coronal holes, 335.19 days of low-speed inter-stream wind, 191.79 days of coronal mass ejections, and 852.83 days of bulk solar wind at Lagrange 1 orbit. Ellipsometry measurements taken at NASA s Johnson Space Center show that all nine flown array materials from the four Genesis regimes have been altered by solar wind exposure during flight. These measurements show significant changes in the optical constant for all nine ultra-pure materials that flew on Genesis when compared with their non-flight material standard. This change in the optical constant (n and k) of the material suggests that the molecular structure of the all nine ultra-pure materials have been altered by solar radiation. In addition, 50 samples of float-zone and czochralski silicon bulk array ellipsometry results were modeled with an effective medium approximation layer (EMA substrate layer) revealing a solar radiation molecular damage zone depth below the SiO2 native oxide layer ranging from 392 to 613 . This bulk solar wind radiation penetration depth is comparable to the depth of solar wind implantation depth of Mg measured by SIMS and SARISA.

Calaway, Michael J.↗
DOE OSTI2025

Segregation of Chromium and Titanium in Sapphire Optical Fiber Grown via the Laser-Heated Pedestal Growth Technique

Our research involves growth of single crystal (SC) optical fibers to be used for sensing applications in harsh environments. Silica optical fibers are an affordable and reliable option for a wide variety of applications including optical fiber sensors and fiber lasers. However, for applications in harsh environments, such as high temperatures, radioactivity, corrosivity, etc., silica fibers are not suitable due to their instability under such conditions. Fibers composed of SC materials such as sapphire and YAG are mechanically, chemically, and thermally more robust to harsh conditions, and thus are more appropriate for sensing applications in environments such as nuclear reactors, jet engines, and boiler. However, SC fibers grown via the laser-heated pedestal growth (LHPG) technique do not intrinsically have a functional cladding layer. A cladding layer is required to reduce the modal volume for distributed sensing applications, to reduce frustrated total internal reflection induced by surface contact of the fiber in certain applications, and to improve transmissivity. Our lab investigates introduction of dopant materials during LHPG to induce an effective core-cladding structure while maintain the crystallinity of the host material. This process results in optical fiber that is not only robust to harsh environments, but also has improved optical properties for distributed sensor applications.

distributed sensing↗
DOE OSTI2025

Segregation of Chromium and Titanium in Sapphire Optical Fiber Grown via the Laser-Heated Pedestal Growth Technique

Our research involves growth of single crystal (SC) optical fibers to be used for sensing applications in harsh environments. Silica optical fibers are an affordable and reliable option for a wide variety of applications including optical fiber sensors and fiber lasers. However, for applications in harsh environments, such as high temperatures, radioactivity, corrosivity, etc., silica fibers are not suitable due to their instability under such conditions. Fibers composed of SC materials such as sapphire and YAG are mechanically, chemically, and thermally more robust to harsh conditions, and thus are more appropriate for sensing applications in environments such as nuclear reactors, jet engines, and boiler. However, SC fibers grown via the laser-heated pedestal growth (LHPG) technique do not intrinsically have a functional cladding layer. A cladding layer is required to reduce the modal volume for distributed sensing applications, to reduce frustrated total internal reflection induced by surface contact of the fiber in certain applications, and to improve transmissivity. Our lab investigates introduction of dopant materials during LHPG to induce an effective core-cladding structure while maintain the crystallinity of the host material. This process results in optical fiber that is not only robust to harsh environments, but also has improved optical properties for distributed sensor applications.

distributed sensing↗
DOE OSTI2025

Structural Diversity and Tunable Emission in Hybrid Organic–Inorganic Copper(I) Bromides

Recently, hybrid organic−inorganic copper(I) metal halides have attracted global attention due to their intriguing optical properties and low-cost solution processability. In this work, we report three hybrid organic−inorganic copper(I) bromides, [TMPA] 2 [Cu 2 Br 4 ], [TMPA] 4 [Cu 6 Br 10 ], and [TMPA] 2 [Cu 4 Br 6 ], synthesized through a slow evaporation method using trimethylphenylammonium (TMPA + ) as the organic cation. By precise control of the CuBr and TMPABr precursors, different copper halide [Cu 2 Br 4 ] 2− , [Cu 6 Br 10 ] 4− , and [Cu 4 Br 6 ] 2− structural units can be obtained. [TMPA] 2 [Cu 2 Br 4 ], [TMPA] 4 [Cu 6 Br 10 ], and [TMPA] 2 [Cu 4 Br 6 ] demonstrate distinct blue, orange, and greenish-yellow light emission, respectively. The first two compounds have zero-dimensional (0D) crystal structures in centrosymmetric triclinic space group P-1 and monoclinic space group P2 1 /n. In contrast, [TMPA] 2 [Cu 4 Br 6 ] features a unique one-dimensional (1D) structure and crystallizes in the centrosymmetric monoclinic space group P2 1 /c. Consequently, the observed greenish-yellow emission of [TMPA] 2 [Cu 4 Br 6 ] is also unique, in contrast to the typical orange-red emission of 0D [Cu 4 Br 6 ]-based compounds. This work provides insights into the design of copper halide light emitters and emphasizes the influence of structural dimensionality on photoluminescence. The tunable optical properties suggest the potential of these materials for multicolor photopatterning, information encryption, and anticounterfeiting applications.

Anions↗
DOE OSTI2025

A Miniaturized, High-Bandwidth Optical Fiber Fabry–Perot Cavity Vibration Sensor Demonstrated up to 800 °C

A typical structural health monitoring technique involves measuring the vibrational characteristics of components or systems to detect signs of degradation or damage. Many industrial applications require engineered systems to safely operate under extreme, high-temperature environments that pose challenges not only to materials but also to sensors that would be used for structural health monitoring. Here, in this study, miniaturized optical Fabry-Perot cavities (FPCs) were developed and tested as a means of measuring the resonant frequencies of metal components that are most relevant to extreme-environment applications. Two of the three candidate FPC designs tested up to 800 ° C provided accurate measurements (validated by theoretical models and laser Doppler vibrometry) of the fundamental vibrational mode of the specimen to which each was bonded, although both sensors failed during thermal cycling. An analysis of the reflected optical spectrum from the FPC and X-ray computed tomography revealed two opportunities to improve the sensor reliability. First, the Cu optical fiber coating that was used could either be replaced with a more oxidation-resistant material or protected with commercially available films. Second, the adhesives used to bond the fibers to metal capillaries and establish the FPC could be replaced with a more robust solution, although the Resbond 907TS adhesive appeared to outperform Resbond 907.

Birri, Anthony [Oak Ridge National Laboratory (ORN↗
NASA NTRS1998

Photonic and Opto-Electronic Applications of Polydiacetylene Films Photodeposited from Solution and Polydiacetylene Copolymer Networks

Polydiacetylenes (PDAS) are attractive materials for both electronic and photonic applications because of their highly conjugated electronic structures. They have been investigated for applications as both one-dimensional (linear chain) conductors and nonlinear optical (NLO) materials. One of the chief limitations to the use of PDAs has been the inability to readily process them into useful forms such as films and fibers. In our laboratory we have developed a novel process for obtaining amorphous films of a PDA derived from 2-methyl4-nitroaniline using photodeposition with Ultraviolet (UV) light from monomer solutions onto transparent substrates. Photodeposition from solution provides a simple technique for obtaining PDA films in any desired pattern with good optical quality. This technique has been used to produce PDA films that show potential for optical applications such as holographic memory storage and optical limiting, as well as third-order NLO applications such as all-optical refractive index modulation, phase modulation and switching. Additionally, copolymerization of diacetylenes with other monomers such as methacrylates provides a means to obtain materials with good processibility. Such copolymers can be spin cast to form films, or drawn by either melt or solution extrusion into fibers. These films or fibers can then be irradiated with UV to photopolymerize the diacetylene units to form a highly stable cross-linked PDA-copolymer network. If such films are electrically poled while being irradiated, they can achieve the asymmetry necessary for second-order NLO applications such as electro-optic switching. On Earth, formation of PDAs by the above mentioned techniques suffers from defects and inhomogeneities caused by convective flows that can arise during processing. By studying the formation of these materials in the reduced-convection, diffusion-controlled environment of space we hope to better understand the factors that affect their processing, and thereby, their nature and properties. Ultimately it may even be feasible to conduct space processing of PDAs for technological applications.

Paley, Mark S.↗
DOE OSTI2021

Ab-initio predictions of phase stability, electronic structure, and optical properties of (0001)-MAX surfaces in M 2 AC (M = Cr, Zr, Hf; A = Al, Ga)

In this work, we report MAX phases' surface properties, which are essential for thin-film technology due to their excellent resistance to high-temperature oxidation, corrosion, and wear. The surface stability, electronic, and optical properties of 0001-surfaces in M 2 AC (M = Zr, Hf, Cr; A = Al, Ga) are investigated and compared with their bulk counterparts. The interplay between chemical bonding and charge distribution is discussed from electronic structure, including the Fermi surfaces. Four possible (0001)-terminated surfaces are considered by breaking M - C and M-A bonds in which cleavage energy of M - C is higher than M-A. The Cr–Al bond in Cr 2 AlC is stronger than other M-A bonds. The charge density of valance A-p electrons redistributes in the surface area, distinct from that of the bulk. The A- and M(C)-terminated (0001)-surfaces are the most stable and energetically favorable terminations due to lower surface energies. The optical properties of the most stable (0001)-surfaces were also investigated to understand the dielectric and photoconductive behavior in the (0001)-terminated surfaces of M 2 AC.

36 MATERIALS SCIENCE↗