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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

LARC(tm) RP46 Polyimide Low Cost High Temperature Technology

The LARC(tm) RP46 polyimide was developed in 1991 at NASA Langley Research Center as an ultra-high-performance composite matrix resin for use in aircraft engine components, as well as a more environmentally friendly alternative to commercially available high temperature matrix resins. The LARC(tm) RP46 polyimide is prepared with non-toxic 3,4'-oxyldianiline(ODA). This chemistry has led to several improved performance characteristics over similar high temperature polyimides. These improvements include: (1) 700 F use temperature; (2) Significantly less moisture absorption; (3) Better chemical corrosion resistance; (4) Greater microcracking resistance; (5) Higher structural durability. The 700 F use temperature LARC(tm) RP46 is 150 F higher than that of commonly used PMR-type high temperature resins. In addition, it features significantly less moisture absorption and is therefore less susceptible to moisture induced damage. It also has better corrosion resistance to chemicals, greater microcracking resistance, and higher durability with regard to structural integrity.

Pater, Ruth H.↗
NASA NTRS1985

Basalts of Mars: Constraints on Volatile Evolution

The mineralogy of relatively unweathered rocks on Mars place important constraints on models of planetary oxidation state, volcanism and associated outgassing, accretion and associated volatile inventory, and geochemical changes over time. Reflectance spectra (300 to 2500 nm) provide direct mineralogic information about the surface materials. Spectra measured using Earth-based telescopes were analyzed by a multiple high-order derivative spectroscopy technique. Nine areas, measured during the 1978 opposition, were analyzed by the technique. Each contained suites of well-defined absorption bands. These bands can be interpreted in terms of constituent mineralogy by the technique of Adams. Among the features extracted from the spectra were bands attributed to iron oxides. Other bands can be attributed to silicates within chemically unweathered rocks/fines. Absorption features suggest the presence of Mg-olivine and plagioclase feldspar.

Huguenin, R. L.↗
DOE OSTI2020

Charge-transfer satellites and chemical bonding in photoemission and x-ray absorption of SrTi O 3 and rutile Ti O 2 : Experiment and first-principles theory with general application to spectroscopic analysis

First-principles, real-time-cumulant, and Bethe-Salpeter-equation calculations fully capture the detailed satellite structure that occurs in response to the sudden creation of the core hole in both photoemission and x-ray absorption spectra of the transition-metal compounds SrTi O 3 and rutile Ti O 2 . Analysis of the excited-state, real-space charge-density fluctuations betrays the physical nature of these many electron excitations that are shown to reflect the materials’ solid-state electronic structure and chemical bonding. This first-principles development of the cumulant-based core hole spectral function is generally applicable to other systems and should become a standard tool for all similar spectroscopic analysis going beyond the quasiparticle physics of the photoelectric effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Rationally Engineered Vertically Aligned β ‐Ga 2− x W x O 3 Nanocomposites for Self‐Biased Solar‐Blind Ultraviolet Photodetectors with Ultrafast Response

Abstract With the astonishing advancement of present technology and increasing energy consumption, there is an ever‐increasing demand for energy‐efficient multifunctional sensors or transducers based on low‐cost, eco‐friendly material systems. In this context, self‐assembled vertically aligned β ‐Ga 2− x W x O 3 nanocomposite (GWO‐VAN) architecture‐assisted self‐biased solar‐blind UV photodetection on a silicon platform, which is the heart of traditional electronics is presented. Utilizing precisely controlled growth parameters, the formation of W‐enriched vertical β ‐Ga 2− x W x O 3 nanocolumns embedded into the W‐deficient β ‐Ga 2− x W x O 3 matrix is reached. Detailed structural and morphological analyses evidently confirm the presence of β ‐Ga 2− x W x O 3 nanocomposite with a high structural and chemical quality. Furthermore, absorption and photoluminescence spectroscopy explains photo‐absorption dynamics and the recombination through possible donor–acceptor energy states. The proposed GWO‐VAN framework facilitates evenly dispersed nanoregions with asymmetric donor energy state distribution and thus forms build‐in potential at the vertical β ‐Ga 2− x W x O 3 interfaces. As a result, the overall heterostructure evinces photovoltaic nature under the UV irradiation. A responsivity of ≈30 A/W is observed with an ultrafast response time (≈350 µs) under transient triggering conditions. Corresponding detectivity and external quantum efficiency are 7.9 × 10 12 Jones and 1.4 × 10 4 %, respectively. It is believed that, while this is the first report exploiting GWO‐VAN architecture to manifest self‐biased solar‐blind UV photodetection, the implication of the approach is enormous in designing electronics for extreme environment functionality and has immense potential to demonstrate drastic improvement in low‐cost UV photodetector technology.

Das, Debabrata↗
DOE OSTI2021

Chalcogenide perovskite BaZrS 3 thin-film electronic and optoelectronic devices by low temperature processing

Owing to its superior visible light absorption and high chemical stability, chalcogenide perovskite barium zirconium sulfide (BaZrS 3 ) has attracted significant attention in the past few years as a potential alternative to hybrid halide perovskites for optoelectronics. However, the high processing temperatures of BaZrS 3 thin films at above 1000 °C severely limits their potential for device applications. Herein, we report the synthesis of BaZrS 3 thin films at temperatures as low as 500 °C, by changing the chemical reaction pathway. The single phase BaZrS 3 thin film was confirmed by X-ray diffraction and Raman spectroscopy. Atomic force microscopy and scanning electron microscopy show that crystalline size and surface roughness were consistently reduced with decreasing annealing temperature. The lower temperatures further eliminate sulfur vacancies and carbon contaminations associated with high temperature processing. The ability to synthesize chalcogenide perovskite thin films at lower temperatures removes a major hurdle for their device fabrication. The photodetectors demonstrate fast response and an on/off ratio of 80. Finally, the fabricated field effect transistors show an ambipolar behavior with electron and hole mobilities of 16.8 cm 2 /Vs and 2.6 cm 2 /Vs, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Atmospheric processing and aerosol aging responsible for observed increase in absorptivity of long-range-transported smoke over the southeast Atlantic

Biomass burning aerosol (BBA) from agricultural fires in southern Africa contributes about one-third of the global carbonaceous aerosol load. These particles have strong radiative effects in the southeast Atlantic (SEA), which depend in part on the radiative contrast between the aerosol layer in the free troposphere (FT) and the underlying cloud layer. However, there is large disagreement in model estimates of aerosol-driven climate forcing due to uncertainties in the vertical distribution, optical properties, and life cycle of these particles. This study applies a novel method combining remote sensing observations with regional model outputs to investigate the aging of the BBA and its impact on the optical properties during transatlantic transport from emission sources in Africa to the SEA. Results show distinct variations in extinction Ångström exponent (EAE) and single-scattering albedo (SSA) as aerosols age. Near the source, fresh aerosols are characterized by low mean SSA (0.84) and high EAE (1.85), indicating smaller, highly absorbing particles. By isolating marine contributions from the total column during BBA transport across the SEA, our analysis reveals an initial decrease in BBA absorptivity, with mean FT SSA of 0.87 after 6–7 d, followed by increased absorptivity with mean FT SSA of 0.84 after 10 d, suggesting enhanced absorption due to chemical aging. These findings indicate that BBA becomes more absorbing during extended transport across the SEA, with implications for reducing model uncertainties. Our remote-sensing-based results agree well with previous in situ studies and offer new insights into aerosol–radiation interactions and the energy balance over the SEA.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1968

Nature of quasi-stellar objects

Quasar properties from cosmological nature, discussing red shift, luminosity, radiation intensity, absorption features, distribution, chemical composition, etc

Burbidge, G. R.↗
NASA NTRS1970

Photochromism of dihydroquinolines

Reversible photochromic reactions, in which absorption spectrum of chemical compound may be shifted by application of visible or ultraviolet light, and then returned to original state by heating, are observed for certain members of 1,2-dihydroquinoline family. Structural formulas for colorless and colored states are given.

Becker, R. S.↗
NASA NTRS1991

Superfiber For Strong, Light Fabrics

New ultrahigh-molecular-weight fiber offers major advantages as fabric for space suits, diving suits, sporting goods, sails, and ultralight aircraft. Polyolefin fiber has extremely high modulus of elasticity, low elongation, high specific strength, low specific gravity, resistance to chemicals, low moisture absorption, and high resistance to damage by flexure and abrasion. Consists of elongated, highly aligned, highly crystalline polyethylene molecules. Structure not only results in high strength-to-weight ratio but also gives high resistance to tearing and ripping. Fibers woven in many patterns. Offers combination of desirable properties not found in nylon, polyester, or aramid fabrics.

Dawn, Frederic S.↗
NASA NTRS1993

UV spectroscopy of low-redshift active galaxies

Ultraviolet spectra of bright Seyfert 1 galaxies will be obtained with the Hubble Space Telescope. Observations will be used to pursue the following goals: (1) Broad and narrow components of the strong emission lines will be deconvolved. (2) Broad-line profiles will be extracted for comparison with kinematic models; line ratios will be determined. (3) Many weak UV and emission lines from optical spectra will be compared for reddening along line of sight and chemical composition. (4) Absorption lines from Galactic halo, intergalactic medium and Seyfert galaxy will be used to establish physical conditions/chemical composition of the gas. (5) Strong emission Fe II in the UV will be used to determine FE II/L-alpha ratios for comparison with photoionization models. Other tasks relating to GTO 1170 program will be performed. It appears that NLR clouds in NGC 5548 experience much higher level of ionizing flux than those Seyfert 2 galaxies. Future observations will determine if this result extends to other Seyfert 1 galaxies.

Wu, C.-C.↗
NASA NTRS2001

Development of an Early Warning Fire Detection System using Correlation Spectroscopy

Combustion byproducts are numerous. A few examples of the gaseous byproducts include carbon dioxide, carbon monoxide, hydrogen chloride, hydrogen cyanide and ammonia. For detecting these chemical species, classic absorption spectroscopy has been used for many decades, but the sensitivity of steady-state methods is often unsuitable for the detection of trace compounds at the low levels (parts per million to parts per billion) appropriate for scientific purposes. This is particularly so for monitoring equipment, which must be compact and cost-effective, and which is often subjected to shock, vibration, and other environmental effects that can severely degrade the performance of high-sensitivity spectrometers in an aircraft. Steady-state techniques also suffer from a lack of specificity; the deconvolution of the spectra of complex mixtures is a laborious and error prone process. These problems are exacerbated in remote fiber-optic monitoring where, for practical reasons, the fundamental absorbance region of the spectrum (often between 3 and 8 microns) is inaccessible, and the low-strength, closely spaced, near-infrared overtone absorbance bands must be used. We circumvented these challenges by employing correlation spectroscopy, a variation of modulation spectroscopy.

Goswami, K.↗
NASA NTRS2002

Multiwavelength Luminosity Functions of Galaxies

I have developed a technique for measuring multi-variate luminosity functions of galaxies. Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and absorption and re-emission of dust within evolving galaxy populations. By using principle component analysis to reduce the dimensionality of the problem, I optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, I derive the multiwavelength luminosity function for the galaxies in the released SDSS catalog, and show that the results are consistent with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by the SIRTF and GALEX missions.

Gardner, Jonathan↗
NASA NTRS2002

Multi-wavelength Luminosity Functions of Galaxies

Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and absorption and re-emission of dust within evolving galaxy populations. By using principal component analysis to reduce the dimensionality of the problem, we optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, we derive the multi-wavelength luminosity function for the galaxies in the released SDSS catalog, and compare the results with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by 2MASS, and the SIRTF and GALEX missions.

Gardner, J. P.↗
NASA NTRS1990

Development of a modulator to measure water vapor selectively in a gaseous mixture

Selective thermal modulation (STM) is a technique which produces a concentration-dependent pulse by selectively modulating a sample in a gas stream. Several types of modulation techniques, both chemical and physical, using adsorption, decomposition, and catalytic and mechanical methods have been developed for use with multiplex gas chromatography. Two of these applications involve selective modulation of the components present in the sample gas stream. The selective modulation of the concentration of specific sample molecules or classes of molecules provides additional analytical selectivity which can lead to selective detection. For some specific applications, the column may even be eliminated. Chemical modulation by absorption of a substance from the sample stream by a stationary phase will also produce a change in the signal intensity. Removal of a substance from the sample stream results in a signal containing a vacancy peak. In the work reported here, a selective thermal modulation technique has been developed as a method for determination of water vapor for possible use in Mars' atmosphere.

NASA Center ARC↗
NASA NTRS2006

InGaAsSb/AlGaAsSb Heterojunction Phototransistors for Infrared Applications

High quality infrared (IR) quantum detectors are important for several applications, such as atmospheric remote sensing, chemical detection and absorption spectroscopy. Although several IR detectors are commercially available, with different materials and structures, they provide limited performance regarding the signal-to-noise ratio and the corresponding minimum detectable signal. InGaAsSb/AlGaAsSb heterojunction based phototransistors show strong potential for developing IR sensors with improved performance. In this paper, the performance of a novel npn InGaAsSb/AlGaAsSb heterojunction phototransistor is presented. This performance study is based on experimental characterization of the device dark current, noise and spectral response. Detectivity of 1.7x10(exp 9) cmHz(exp 1/2)/W at 2 microns was obtained at 100 C temperature and 2 V bias voltage. This corresponds to a responsivity of 94.7 A/W and an internal gain of 156 with about 37.7% quantum efficiency. Reducing the temperature to -30 C allows to increase the bias to 3V and enhance the detectivity to 8.7x10(exp 10) cmHz(exp 1/2)/W at the same wavelength, which corresponds to a responsivity of 386.5 A/W and an internal gain of 288.2 with about 83.3% quantum efficiency. The device impulse response and linearity, including the corresponding dynamic range, also are presented. Impulse response analysis indicated a settling time of about 1.1 s at 2V and 100 C, while linearity measurements indicated a constant responsivity in the radiation intensity range of 1.6x10(exp -7) W/sq cm and 31.6 mW/sq cm.

Refaat, Tamer F.↗
NASA NTRS2016

How We Can Constrain Aerosol Type Globally

In addition to aerosol number concentration, aerosol size and composition are essential attributes needed to adequately represent aerosol-cloud interactions (ACI) in models. As the nature of ACI varies enormously with environmental conditions, global-scale constraints on particle properties are indicated. And although advanced satellite remote-sensing instruments can provide categorical aerosol-type classification globally, detailed particle microphysical properties are unobtainable from space with currently available or planned technologies. For the foreseeable future, only in situ measurements can constrain particle properties at the level-of-detail required for ACI, as well as to reduce uncertainties in regional-to-global-scale direct aerosol radiative forcing (DARF). The limitation of in situ measurements for this application is sampling. However, there is a simplifying factor: for a given aerosol source, in a given season, particle microphysical properties tend to be repeatable, even if the amount varies from day-to-day and year-to-year, because the physical nature of the particles is determined primarily by the regional environment. So, if the PDFs of particle properties from major aerosol sources can be adequately characterized, they can be used to add the missing microphysical detail the better sampled satellite aerosol-type maps. This calls for Systematic Aircraft Measurements to Characterize Aerosol Air Masses (SAM-CAAM). We are defining a relatively modest and readily deployable, operational aircraft payload capable of measuring key aerosol absorption, scattering, and chemical properties in situ, and a program for characterizing statistically these properties for the major aerosol air mass types, at a level-of-detail unobtainable from space. It is aimed at: (1) enhancing satellite aerosol-type retrieval products with better aerosol climatology assumptions, and (2) improving the translation between satellite-retrieved aerosol optical properties and species-specific aerosol mass and size that are tracked in aerosol transport and climate models used to assess aerosol forcing and its anthropogenic components. This presentation will summarize where we stand on the development of the SAM-CAAM concept.

DARF↗
DOE OSTI2022

Experimental Investigation of the Effect of Atomizing Electrospray Nozzles on the Cooling and Reduced Humidification of Air

Separating sensible and latent cooling have shown the potential to reduce energy consumption in A/C systems for building HVAC applications. Several technologies exist based on vapor-compression refrigeration, enthalpy wheels, chemical adsorption and absorption materials, and mechanical cooling. However, their thermodynamics limits and high energy consumption hinder their deployment in hot and humid climatic regions. This paper focuses on separating sensible and latent cooling by using a new thermodynamics process and in-kind (i.e., non-vapor compression-based) technology. Highly electrically charged water droplets were sprayed in the airflow. These droplets attracted water vapor molecules to their surfaces and promoted condensation. The phenomenon was the result of simultaneous dielectrophoresis and electro-diffusion interactions. Studies in the literature have shown that using multiple capillary electrodes reduced air moisture by up to 5% when using nanometer-size droplets in the spray. Unfortunately, these studies were limited to low airflow rates, and the objective of this paper was to investigate how to scale up this in-kind approach to airflows typical of buildings. In the present paper, droplets of micrometer size were utilized to control the humidity for a 5-cfm flow rate. While this airflow was still low for building applications, it was 100 times fold the airflows in the literature studies. The air was tested at 20°C and at 50 and 80% relative humidity. A two-fluid atomizing nozzle produced the droplets in the spray, and high DC electric potential, up to 25 kV, was used to charge the fine droplets electrically. The air atomizing nozzle with high voltage potential resembled an evaporative cooler process. However, a measurable reduction of the absolute humidity of up to 2% was observed compared to the case of the nozzle with no high voltage potential. The entire device had one small nozzle selected from off-the-shelf components and had less than a 9 cm2 footprint area.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗