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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

The Tagish Lake Meteorite as a Possible Sample from a T or D Type Asteroid

Since the Tagish Lake meteorite fell in January 2000, the one of the kind meteorite has become the hottest issue among meteoriticists as well as astrobiologists. Meanwhile, concerning the physical origin of the meteorite in our solar system, only Hiroi et al. reported that it likely came from a D asteroid based on comparison of their visible-near-infrared (Vis-NIR) reflectance spectra. However, because asteroid classification is usually performed based on a limited range of wavelength, the asteroid classes and surface compositions may not necessarily have one-to-one correspondence. Also, Hiroi et al. precluded the T-type asteroids simply because their average albedo is much higher than the visible reflectance of Tagish Lake although their spectral matches with Tagish Lake were good, and the 3-mm band spectra compiled in were not enough to compare the degree of hydration or kinds of hydrous minerals between primitive asteroids and Tagish Lake. In this paper, we employ more spectral datasets up to the 3-mm range to address the possible connection between two particular asteroids, 773 Irmintraud and 308 Polyxo, and the Tagish Lake meteorite.

Hiroi, T.↗
DOE OSTI2014

Vibrational spectra of CO adsorbed on oxide thin films: A tool to probe the surface defects and phase changes of oxide thin films

Thin films of iron oxide were grown on Pt(111) single crystals using cycles of physical vapor deposition of iron followed by oxidative annealing in an ultrahigh vacuum apparatus. Two procedures were utilized for film growth of ∼15–30 ML thick films, where both procedures involved sequential deposition+oxidation cycles. In procedure 1, the iron oxide film was fully grown via sequential deposition+oxidation cycles, and then the fully grown film was exposed to a CO flux equivalent to 8 × 10{sup −7} millibars, and a vibrational spectrum of adsorbed CO was obtained using infrared reflection-absorption spectroscopy. The vibrational spectra of adsorbed CO from multiple preparations using procedure 1 show changes in the film termination structure and/or chemical nature of the surface defects—some of which are correlated with another phase that forms (“phase B”), even before enough of phase B has formed to be easily detected using low energy electron diffraction (LEED). During procedure 2, CO vibrational spectra were obtained between deposition+oxidation cycles, and these spectra show that the film termination structure and/or chemical nature of the surface defects changed as a function of sequential deposition+oxidation cycles. The authors conclude that measurement of vibrational spectra of adsorbed CO on oxide thin films provides a sensitive tool to probe chemical changes of defects on the surface and can thus complement LEED techniques by probing changes not visible by LEED. Increased use of vibrational spectra of adsorbed CO on thin films would enable better comparisons between films grown with different procedures and by different groups.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Improvement of reliability and power consumption for SnSb{sub 4} phase change film composited with Ga{sub 3}Sb{sub 7} by superlattice-like method

Superlattice-like (SLL) SnSb{sub 4}/Ga{sub 3}Sb{sub 7} (SS/GS) thin films were investigated through in-situ film resistance measurement. The optical band gap was derived from the transmittance spectra by using a UV-visible-NIR (ultraviolet-visible-near infrared) spectrophotometer. Transmission electron microscopy was used to observe the micro-structure before and after annealing. Phase change memory cells based on the SLL [SS(3 nm)/GS(4.5 nm)]{sub 7} thin films were fabricated to test and verify the operation consumption and switching endurance. The scanning thermal microscopy was used to probe the nanoscale thermal property.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2017

In-Flight Performance of the Ozone Monitoring Instrument

The Dutch-Finnish Ozone Monitoring Instrument (OMI) is an imaging spectrograph flying on NASA's EOS Aura satellite since 15 July 2004. OMI is primarily used to map trace-gas concentrations in the Earth's atmosphere, obtaining mid-resolution (0.4-0.6 nm) ultraviolet-visible (UV- VIS; 264-504 nm) spectra at multiple (30-60) simultaneous fields of view. Assessed via various approaches that include monitoring of radiances from selected ocean, land ice and cloud areas, as well as measurements of line profiles in the solar spectra, the instrument shows low optical degradation and high wavelength stability over the mission lifetime. In the regions relatively free from the slowly unraveling "row anomaly" (RA) the OMI irradiances have degraded by 3- 8 %, while radiances have changed by 1-2 %. The long-term wavelength calibration of the instrument remains stable to 0.005-0.020 nm.

ultraviolet↗
DOE OSTI2015

Optical modeling and electrical properties of cadmium oxide nanofilms: Developing a meta–heuristic calculation process model

Cadmium oxide thin films were deposited onto glass substrates by sol–gel dip-coating method and annealed in air. The normal incidence transmittance of the films was measured by a spectrophotometer. D.C electrical parameters such as carrier concentration and mobility were analyzed by Hall Effect measurements. A combination of Forouhi–Bloomer and standard Drude model was used to simulate the optical constants and thicknesses of the films from transmittance data. The transmittance spectra of the films in the visible domain of wavelengths were successfully fitted by using the result of a hybrid particle swarm optimization method and genetic algorithm. The simulated transmittance is in good accordance with the measured spectrum in the whole measurement wavelength range. The electrical parameters obtained from the optical simulation are well consistent with those measured electrically by Hall Effect measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2021

Composition of Organics on Asteroid (101955) Bennu

Context: The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission detected an infrared absorption at 3.4μm on near-Earth asteroid(101955) Bennu. This absorption is indicative of carbon species, including organics, on the sur-face. Aims: We aim to describe the composition of the organic matter on Bennu by investigating the spectral features in detail. Methods: We use a curated set of spectra acquired by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS) that have features near 3.4μm (3.2 to 3.6μm) attributed to organics. We assess the shapes and strengths of these absorptions in the context of laboratory spectra of extraterrestrial organics and analogs. Results: We find spectral evidence of aromatic and aliphatic CH bonds. The absorptions are broadly consistent in shape and depth with those associated with insoluble organic matter in meteorites. Given the thermal and space weathering environments on Bennu, it is likely that the organics have not been exposed for long enough to substantially decrease the H/C and destroy all aliphatic molecules.

minor planets↗
NASA NTRS2018

Satellite Sensor Requirements for Monitoring Essential Biodiversity Variables of Coastal Ecosystems

The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite-based sensors can repeatedly record the visible and near-infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae). These measures can be incorporated into Essential Biodiversity Variables (EBVs), including the distribution, abundance, and traits of groups of species populations, and used to evaluate habitat fragmentation. However, current and planned satellites are not designed to observe the EBVs that change rapidly with extreme tides, salinity, temperatures, storms, pollution, or physical habitat destruction over scales relevant to human activity. Making these observations requires a new generation of satellite sensors able to sample with these combined characteristics: (1) spatial resolution on the order of 30 to 100-m pixels or smaller; (2) spectral resolution on the order of 5 nm in the visible and 10 nm in the short-wave infrared spectrum (or at least two or more bands at 1,030, 1,240, 1,630, 2,125, and/or 2,260 nm) for atmospheric correction and aquatic and vegetation assessments; (3) radiometric quality with signal to noise ratios (SNR) above 800 (relative to signal levels typical of the open ocean), 14-bit digitization, absolute radiometric calibration less than 2%, relative calibration of 0.2%, polarization sensitivity less than 1%, high radiometric stability and linearity, and operations designed to minimize sunglint; and (4) temporal resolution of hours to days. We refer to these combined specifications as H4 imaging. Enabling H4 imaging is vital for the conservation and management of global biodiversity and ecosystem services, including food provisioning and water security. An agile satellite in a 3-d repeat low-Earth orbit could sample 30-km swath images of several hundred coastal habitats daily. Nine H4 satellites would provide weekly coverage of global coastal zones. Such satellite constellations are now feasible and are used in various applications.

aquatic↗
DOE OSTI2016

Photocatalytic behaviour of CdS/ZnS nanocomposite for dye degradation in presence of visible light

In the present work ZnS-CdS composite was prepared by hydrothermal method. The prepared samples were characterized by X-ray diffraction (XRD) to confirm formation of nano particles, Scanning electron microscopy (SEM) images exhibit nanoscale dimensions of as synthesized individual phases. UV/VIS spectra were recorded for evaluation of photophysical properties. The composite was explored as photocatalysts to study dye degradation using methylene blue in aqueous slurry under irradiation of 663 nm wavelength and congo red under irradiation of 493 nm wavelength. Under the same conditions the photocatalytic activity of the individual phases ZnS and CdS were also examined. The ZnS-CdS composite is found in enhancing the rate of photo degradation of toxic dyes as compare to ZnS and CdS individually in presence of visible light. This ZnS based metal sulphide/oxide semiconductor nanocomposites are high potential material for Photo-degradation of toxic dyes, and act as good photocatalyst in visible light.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS2018

Characteristics of In Situ Fine Fraction Aerosol Spectra from 300-700 nm Observed Around the Korean Peninsula During KORUS-OC

In situ aerosol extinction and absorption spectra covering the 300-700 nm range at ≤ 1 nm spectral resolution were measured aboard the R/V Onnuri during the Korea U.S. – Ocean Color (KORUS-OC) cruise around the Korean Peninsula from May 21 through June 3, 2016. Total absorption spectra were obtained from aerosols collected on glass fiber filters and subsequently placed in the center of an integrating sphere (Labsphere DRA-CA-30) attached to a dual beam spectrophotometer (Cary 100 Bio UV-Visible Spectrophotometer, 0.2 nm spectral resolution). Absorption spectra from methanol and deionized water extracts of aerosols collected on Teflon filters were measured in a liquid waveguide capillary cell (World Precision Instruments LWCC- 3100, ~0.4 nm spectral resolution). Extinction spectra were measured with a custom built instrument (SpEx, ~0.8 nm spectral resolution). The measurements were obtained at a height of ~10 m above the sea surface with an inlet that limited the measured aerosols to diameters ≤ 1.3 µm. All four sets of spectra exhibit curvature in log-log space with 2nd order polynomials providing a better fit to the measured spectra than power law fits. The deionized water extracts were also analyzed with an ion chromatograph (Dionex ICS-3000 Ion Chromatography System) and with an aerosol mass spectrometer (Aerodyne Research, Inc. HR-ToF High Resolution Aerosol Mass Spectrometer) to examine chemical composition. These data indicate the optical spectra are sensitive to differing chemical properties of the measured ambient aerosols and suggest differing sources and/or atmospheric processes influence the observed optical signatures. The measured suite of spectra are combined to examine the spectral characteristics of single scattering albedo, as well as to examine the contribution of soluble absorbing chromophores to the total absorption spectra. Additional measurements made during the affiliated Korea U.S. - Air Quality (KORUS-AQ) campaign will be used to provide further insight on the observed spectral characteristics.

Jordan, Carolyn E↗
DOE OSTI2018

Color Ultrafast Photography Study of a High-Current Discharge Initiated by Exploding a Short Wire in the Atmosphere

In this paper, we describe the ultrafast slit-scanning photography of light phenomena arising at the stage of the electrical breakdown in the atmosphere and in a channel initiated by a wire explosion. The characteristics and features of the photographic registration of the SFR-1 camera using color and spectrozonal negative aerial films sensitive in the visible and near infrared regions of the optical spectrum are presented. Using photograms in color, we were able to visualize small-scale inhomogeneities, a current-carrying channel and its “shell,” emissions of matter, and shock waves in the plasma. This technique made it possible to record a secondary shock wave in the plasma on the discharge axis during the explosion of short (length ≈15 mm) copper and nichrome wires with a diameter of 100–150 μm at a stored energy of ~100 J. At the moment of cumulation in the plasma, a “hot spot” with a minimum size of ~0.5 mm was formed on the discharge axis. It may be the source of narrow-beam coherent radiation with X-ray photon energies of 10–30 keV. The cumulation mechanism is discussed based on the regularities of the z-pinch phenomenon in a discharge initiated by a wire explosion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2006

Dust That's Worth Keeping

Images taken of interstellar space often display a colorful canvas of portions of the electromagnetic spectrum. Dispersed throughout the images are interstellar clouds of dust and gas--remnants ejected from stars and supernovae over billions and billions of years. For more than 40 years, astronomers have observed that interstellar dust exhibits a consistent effect at a spectral wavelength of 2,175 angstroms, the equivalent of 5.7 electronvolts in energy on the electromagnetic spectrum. At this wavelength, light from stars is absorbed by dust in the interstellar medium, blocking the stars light from reaching Earth. The 2,175-angstrom feature, which looks like a bump on spectra, is the strongest ultraviolet-visible light spectral signature of interstellar dust and is visible along nearly every observational line of sight. Scientists have sought to solve the mystery of what causes the 2,175-angstrom feature by reproducing the effect in the laboratory. They speculated a number of possibilities, including fullerenes (buckyballs), nanodiamonds, and even interstellar organisms. However, none of these materials fits the data for the unique spectral feature. Limitations in the energy and spatial resolution achievable with electron microscopes and ion microprobes--the two main instruments used to study samples of dust--have also prevented scientists from finding the answer. A collaborative effort led by Livermore physicist John Bradley and funded by the National Aeronautics and Space Administration (NASA) has used a new-generation transmission electron microscope (TEM) and nanoscale ion microprobe to unlock the mystery. The Livermore group includes physicists Zu Rong Dai, Ian Hutcheon, Peter Weber, and Sasa Bajt and postdoctoral researchers Hope Ishii, Giles Graham, and Julie Smith. They collaborated with the University of California at Davis (UCD), Lawrence Berkeley National Laboratory, Washington University's Laboratory for Space Sciences in St. Louis, and NASA's Ames Research Center for their discovery. The team analyzed micrometer-size interplanetary dust particles (IDPs), each about one-tenth the diameter of a human hair. Within the particles, they found carriers of the 2,175-angstrom feature: organic carbon mixed with amorphous silicates (glass with embedded metals and sulfides, GEMS), two of the most common materials in interstellar space. Ishii says, 'Organic carbon and amorphous silicates are abundant in interstellar dust clouds, and abundant carriers are needed to account for the frequent astronomical observation of the 2,175-angstrom feature. It makes sense that this ubiquitous feature would come from common materials in interstellar space'. The group's results increase scientific understanding of the starting materials for the formation of the Sun, solar system, and life on Earth.

Interstellar matter↗
DOE OSTI2014

Synthesis of novel MoS{sub 2}/g-C{sub 3}N{sub 4} heterojunction photocatalysts with enhanced hydrogen evolution activity

Novel MoS{sub 2}/g-C{sub 3}N{sub 4} heterojunction photocatalysts were synthesized via a simple impregnation and heating methods. The products were characterized by X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectra. The photocatalytic activities of MoS{sub 2}/g-C{sub 3}N{sub 4} samples were evaluated based on the hydrogen evolution experiments under visible light irradiation (λ > 400 nm). The UV–vis diffuse reflectance spectra revealed that the MoS{sub 2}/g-C{sub 3}N{sub 4} photocatalysts had strong absorption in the visible light region. The photocatalytic results indicated that the highest H{sub 2} evolution rate of 23.10 μmol·h{sup −1} was achieved on the 0.5 wt.% MoS{sub 2}–g-C{sub 3}N{sub 4} sample, which was enhanced by 11.3 times compared to pure g-C{sub 3}N{sub 4}. This study may provide an approach to the development of novel heterojunction photocatalysts for hydrogen production under visible light irradiation. - Highlights: • MoS{sub 2}/g-C{sub 3}N{sub 4} photocatalyst is obtained by simple impregnation and heating methods. • and determined by XRD, TEM, UV-vis diffuse reflectance spectra. • the photocatalysts had strong absorption in the visible light region. • the highest H2 evolution rate was achieved on the 0.5wt% samples.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Realization of all-optical plasmonic MIM split square ring resonator switch

In this work, a configuration of nano plasmonic switch is proposed and investigated. The structure is comprised of the combination of split square ring and straight waveguides. Simulations are done based on Finite-Difference-Time Domain method. The structure is based on metal-insulator-metal configuration. Split square ring and straight waveguides are consisted of air, which are situated in a silver background. The proposed switch can confine light to sub-wavelength dimensions (on the order of nano meter); therefore it can be used in highly integrated optical circuits. The split square ring structure can operate both directly or reversely based on the split position. The transmitted powers in different cases of split square switch are acceptable and higher than 0.6. Therefore, the proposed switch is an appropriate candidate for highly integrated optical communication systems.

42 ENGINEERING↗
DOE OSTI2015

Hydrothermal synthesis and tunable luminescence of CaSiO{sub 3}:RE{sup 3+}(RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) nanocrystals

Highlights: • Near-spherical CaSiO{sub 3} nanocrystals were synthesized via a hydrothermal method. • The effect of calcination temperature on crystalline phase formation was discussed. • Optical properties of trivalent ions doped CaSiO{sub 3} nanocrystals were investigated. • Tunable luminescence of CaSiO{sub 3}:Tb{sup 3+}, Eu{sup 3+} can be achieved by a simple method. - Abstract: CaSiO{sub 3}:RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) nanocrystals were prepared by facile hydrothermal method with further calcinations. The crystal structure and the effects of annealing temperature on phase transition have been characterized by X-ray diffraction (XRD). The photoluminescence (PL) and PL excitation (PLE) spectra were used to characterize the optical properties of all samples. The effect of Eu{sup 3+} and Sm{sup 3+} doping concentrations on the luminescent intensity were also investigated in details, respectively. Moreover, the luminescence colors of the Tb{sup 3+} and Eu{sup 3+} co-doped CaSiO{sub 3} samples can be tuned by simply adjusting the relative doping concentrations of the rare earth ions under a single wavelength excitation, which might find potential applications in the fields of light display systems and optoelectronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Effect of (Nd, Ni) co-doped on the multiferroic and photocatalytic properties of BiFeO{sub 3}

Highlights: • Sol–gel synthesis. • Saturation magnetization and ferroelectricity increases in Ni co-doped samples. • Conduction mechanism is different in Nd doped and (Nd, Ni) co-doped samples. • Samples show good photocatalytic activity in the presence of H{sub 2}O{sub 2}. - Abstract: Bi{sub 0.95}Nd{sub 0.05}Fe{sub 1−x}Ni{sub x}O{sub 3} (x = 0, 0.01, 0.03 and 0.05) samples are synthesized by solgel method. The phase and crystal structure of the samples are confirmed by X-ray diffraction studies, Rietveld refinement is performed to calculate the structural parameters. The reflectance spectra show bands in UV and visible region and the optical band gap is calculated using Kulbeka–Munk function. The magnetization and leakage current density are strongly influenced by doping. Different conduction mechanisms are observed in Nd doped and Ni co-doped samples. All the samples exhibit ferroelectric nature at various frequencies. Photocatalytic activities of the samples are determined by the degradation of methylene blue dye in the presence of visible light and H{sub 2}O{sub 2} which shows samples are good photo-Fenton like catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Application of a set of complementary techniques to understand how varying the proportion of two wastes affects humic acids produced by vermicomposting

Highlights: • A set of techniques was used to characterize humic acids content of vermicomposts. • The properties of the humic acids produced from different waste mixtures were similar. • This set of techniques allowed distinguishing the humic acids of each vermicomposts. • Increasing humic acid contents in initial mixtures would produce richer vermicomposts. - Abstract: A better understanding of how varying the proportion of different organic wastes affects humic acid (HA) formation during vermicomposting would be useful in producing vermicomposts enriched in HAs. With the aim of improving the knowledge about this issue, a variety of analytical techniques [UV–visible spectroscopic, Fourier transform infrared, fluorescence spectra, solid-state cross-polarization magic-angle spinning (CPMAS) {sup 13}C nuclear magnetic resonance (NMR) spectra, and thermal analysis] was used in the present study to characterize HAs isolated from two mixtures at two different ratios (2:1 and 1:1) of tomato-plant debris (TD) and paper-mill sludge (PS) before and after vermicomposting. The results suggest that vermicomposting increased the HA content in the TD/PS 2:1 and 1:1 mixtures (15.9% and 16.2%, respectively), but the vermicompost produced from the mixture with a higher amount of TD had a greater proportion (24%) of HAs. Both vermicomposting processes caused equal modifications in the humic precursors contained in the different mixtures of TD and PS, and consequently, the HAs in the vermicomposts produced from different waste mixtures exhibited analogous characteristics. Only the set of analytical techniques used in this research was able to detect differences between the HAs isolated from each type of vermicompost. In conclusion, varying the proportion of different wastes may have a stronger influence on the amount of HAs in vermicomposts than on the properties of HAs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Thermoelastic investigation of a quartz tuning fork used in infrared spectroscopy

The performances of quartz tuning forks (QTF) used in infrared spectroscopy for pollutant detection are investigated. The transduction between light and QTF vibration is elucidated, thanks to QTF encapsulation under vacuum. From the sensitivity enhancement which is obtained, we conclude that their interaction is photo-thermoelastic rather than photo-thermoacoustic. A mapping of the local sensitivity of the QTF is obtained by scanning its faces with the excitation probe beam. The comparison between the signal mapping and the theoretical strain mapping indicates that the most efficient areas of the QTF correspond to the areas where the strain or stress is the highest.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Photocurrent spectrum study of a quantum dot single-photon detector based on resonant tunneling effect with near-infrared response

We present the photocurrent spectrum study of a quantum dot (QD) single-photon detector using a reset technique which eliminates the QD's “memory effect.” By applying a proper reset frequency and keeping the detector in linear-response region, the detector's responses to different monochromatic light are resolved which reflects different detection efficiencies. We find the reset photocurrent tails up to 1.3 μm wavelength and near-infrared (∼1100 nm) single-photon sensitivity is demonstrated due to interband transition of electrons in QDs, indicating the device a promising candidate both in quantum information applications and highly sensitive imaging applications operating in relative high temperatures (>80 K).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗