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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 289 records · Page 16

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NASA NTRS1989

Ellipsometric study of Al2O3/Ag/Si and SiO2/Ag/quartz ashed in an oxygen plasma

The growth of silver oxide (proposed as a potentially useful protective coating for space environment) on a silver mirror coated with an Al2O3 or a SiO2 protective layer was investigated using the monolayer-sensitive variable angle of incidence spectroscopic ellipsometry technique. The samples were exposed to a pure oxygen plasma in a plasma asher, and the silver oxide growth was monitored as a function of the exposure time. It was found that atomic oxygen in the asher penetrated through the SiO2 or Al2O3 coatings to convert the silver underneath to silver oxide, and that the quantity of the silver oxide formed was proportional to the ashing time. The band gap of silver oxide was determined to be 1.3 eV. A schematic diagram of the variable angle of incidence spectroscopic ellipsometer is included.

De, Bhola N.↗

DOE OSTI2021

How oxygen passivates polycrystalline nickel surfaces

The passivation of polycrystalline nickel surfaces against hydrogen uptake by oxygen is investigated experimentally with low energy ion scattering (LEIS), direct recoil spectroscopy (DRS), and thermal desorption spectroscopy (TDS). These techniques are highly sensitive to surface hydrogen, allowing the change in hydrogen adsorption in response to varying amounts of oxygen exposure to be measured. The chemical composition of a nickel surface during a mixed oxygen and hydrogen exposure was characterized with LEIS and DRS, while the uptake and activation energies of hydrogen on a nickel surface with preadsorbed oxygen were quantified with TDS. By and large, these measurements of how the oxygen and hydrogen surface coverage varied in response to oxygen exposure were found to be consistent with predictions of a simple site-blocking model. This finding suggests that, despite the complexities that arise due to polycrystallinity, the oxygen-induced passivation of a polycrystalline nickel surface against hydrogen uptake can be approximated by a simple site-blocking model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1999

Internal Heterogeneous Processes in Aluminum Combustion

This paper discusses the aluminum particle combustion mechanism which has been expanded by inclusion of gas dissolution processes and ensuing internal phase transformations. This mechanism is proposed based on recent normal and microgravity experiments with particles formed and ignited in a pulsed micro-arc. Recent experimental findings on the three stages observed in Al particle combustion in air and shows the burning particle radiation, trajectory (streak), smoke cloud shapes, and quenched particle interiors are summarized. During stage I, the radiation trace is smooth and the particle flame is spherically symmetric. The temperature measured using a three-color pyrometer is close to 3000 K. Because it exceeds the aluminum boiling point (2730 K), this temperature most likely characterizes the vapor phase flame zone rather than the aluminum surface. The dissolved oxygen content within particles quenched during stage I was below the detection sensitivity (about 1 atomic %) for Wavelength Dispersive Spectroscopy (WDS). After an increase in the radiation intensity (and simultaneous decrease in the measured color temperature from about 3000 to 2800 K) indicative of the transition to stage II combustion, the internal compositions of the quenched particles change. Both oxygen-rich (approx. 10 atomic %) and oxygen-lean (< 1 %) regions are identified within the particles using back-scattered electron imaging and WDS. During stage II, oscillations are observed in particle radiation and the flame and smoke cloud are distorted from their original spherically-symmetric shape. In stage III, particle radiation continues to exhibit oscillations, but its radiation intensity drops and remains at a nearly constant level. The measured temperature decreases to about 2300 K. Also, larger changes in particle velocities are observed, and oxide caps are found on quenched particle surfaces. While these results showed the correlation between the aluminum particle combustion behavior and the evolution of its internal composition, the change from the spherically symmetric to asymmetric flame shape occurring upon the transition from stage I to stage II combustion could not be understood based only on the fact that dissolved oxygen is detected in the particles. The connection between the two phenomena appeared even less significant because in earlier aluminum combustion studies carried in O2/Ar mixtures, flame asymmetry was not observed as opposed to experiments in air or O2/CO mixtures. It has been proposed that the presence of other gases, i.e., hydrogen, or nitrogen causes the change in the combustion regime.

Dreizin, E. L.↗

NASA NTRS1985

Surface Tensions and Their Variations with Temperature and Impurities

The surface tensions in this work were determined using the sessile drop technique. This method is based on a comparison of the profile of a liquid drop with the profile calculated by solving the Young-Laplace equation. The comparison can be made in several ways; the traditional Bashforth-Adams procedure was used in conjunction with recently calculated drop shape tables which virtually eliminate interpolation errors. Although previous study has found little difference in measurements with pure and oxygen doped silicon, there is other evidence suggesting that oxygen in dilute concentrations severely depresses the surface tension of silicon. The surface tension of liquid silicon in purified argon atmospheres was measured. A temperature coefficient near -0.28 mJ/square meters K was found. The experiments show a high sensitivity of the surface tension to what is believed are low concentrations of oxygen. Thus one cannot rule out some effect of low levels of oxygen in the results. However, the highest surface tension values obtained in conditions which minimized the residual oxygen pressure are in good agreement with a previous measurement in pure hydrogen. Therefore, depression of the surface tension by oxygen is insignificant in these measurements.

Hardy, S. C.↗

NASA NTRS1991

Stacking Oxygen-Separation Cells

Simplified configuration and procedure developed for assembly of stacks of solid-electrolyte cells separating oxygen from air electrochemically. Reduces number of components and thus reduces probability of such failures as gas leaks, breakdown of sensitive parts, and electrical open or short circuits. Previous, more complicated version of cell described in "Improved Zirconia Oxygen-Separation Cell" (NPO-16161).

Schroeder, James E.↗

NASA NTRS1986

Far-ultraviolet fluorescence of carbon monoxide in the red giant Arcturus. II - Analysis of high-dispersion IUE spectra

Faint, diffuse emissions near 1380 A in deeply exposed IUE spectrograms of the red giant Arcturus very likely are associated with bands of the A-X fourth-positive system of carbon monoxide, fluoresced by multiplet UV2 of neutral oxygen near 1305 A. Numerical simulations indicate that the strength of the CO bands is exceedingly sensitive, in the best available one-dimensional model of the chromosphere of Arcturus, to a delicate balance between the rapid inward attenuation of the oxygen radiation field and the rapid outward decline of the molecular absorptivity. The fortuitous character of the overlap region in the single-component model argues that one should also consider the possibility that the pumping occurs in a highly inhomogeneous chromosphere, of the type proposed in previous studies of Arcturus based on observations of the infrared absorption bands of CO.

Ayres, T. R.↗

NASA NTRS2019

Atmospheric Correction of Satellite Ocean-Color Imagery During the PACE Era

The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission will carry into space the Ocean Color Instrument (OCI), a spectrometer measuring at 5 nm spectral resolution in the ultraviolet (UV) to near infrared (NIR) with additional spectral bands in the shortwave infrared (SWIR), and two multi-angle polarimeters that will overlap the OCI spectral range and spatial coverage, i. e., the Spectrometer for Planetary Exploration (SPEXone) and the Hyper-Angular Rainbow Polarimeter (HARP2). These instruments, especially when used in synergy, have great potential for improving estimates of water reflectance in the post Earth Observing System (EOS) era. Extending the top-of-atmosphere (TOA) observations to the UV, where aerosol absorption is effective, adding spectral bands in the SWIR, where even the most turbid waters are black and sensitivity to the aerosol coarse mode is higher than at shorter wavelengths, and measuring in the oxygen A-band to estimate aerosol altitude will enable greater accuracy in atmospheric correction for ocean color science. The multi-angular and polarized measurements, sensitive to aerosol properties (e.g., size distribution, index of refraction), can further help to identify or constrain the aerosol model, or to retrieve directly water reflectance. Algorithms that exploit the new capabilities are presented, and their ability to improve accuracy is discussed. They embrace a modern, adapted heritage two-step algorithm and alternative schemes (deterministic, statistical) that aim at inverting the TOA signal in a single step. These schemes, by the nature of their construction, their robustness, their generalization properties, and their ability to associate uncertainties, are expected to become the new standard in the future. A strategy for atmospheric correction is presented that ensures continuity and consistency with past and present ocean-color missions while enabling full exploitation of the new dimensions and possibilities. Despite the major improvements anticipated with the PACE instruments, gaps/issues remain to be filled/tackled. They include dealing properly with whitecaps, taking into account Earth-curvature effects, correcting for adjacency effects, accounting for the coupling between scattering and absorption, modeling accurately water reflectance, and acquiring a sufficiently representative dataset of water reflectance in the UV to SWIR. Dedicated efforts, experimental and theoretical, are in order to gather the necessary information and rectify inadequacies. Ideas and solutions are put forward to address the unresolved issues. Thanks to its design and characteristics, the PACE mission will mark the beginning of a new era of unprecedented accuracy in ocean-color radiometry from space.

Robert J Frouin↗

NASA NTRS2019

Atmospheric Correction of Satellite Ocean-Color Imagery During the PACE Era

ocean color↗

NASA NTRS2010

Comparative Spectra of Oxygen-Rich Versus Carbon-Rich Circumstellar Shells: VY Canis Majoris and IRC(plus)10216 at 215-285 GHz

A sensitive (1sigma rms at 1 MHz resolution approx.3 mK) 1 mm spectral line survey (214.5-285.5 GHz) of VY Canis Majoris (VY CMa) and IRC +10216 has been conducted to compare the chemistries of oxygen- and carbon-rich circumstellar envelopes. This study was carried out using the Submillimeter Telescope of the Arizona Radio Observatory with a new Atacama Large Millimeter Array type receiver. This survey is the first to chemically characterize an O-rich circumstellar shell at millimeter wavelengths. In VY CMa, 128 emission features were detected arising from 18 different molecules; and in IRC +10216, 720 lines were observed, assigned to 32 different species. The 1 mm spectrum of VY CMa is dominated by SO, and SiS; in IRC +10216, C4H and SiC2 are the most recurrent species. Ten molecules were common to both sources: CO, SiS, SiO, CS, CN, HCN, HNC, NaCl, PN, and HCO(+). Sulfur plays an important role in VY CMa, but saturated/ unsaturated carbon dominates the molecular content of IRC +102.16, producing CH2NH, for example. Although the molecular complexity of IRC +10216 is greater, VY CMa supports a unique "inorganic" chemistry leading to the oxides PO, AlO, and AlOH. Only diatomic and triatomic compounds were observed in VY CMa, while species with four or more atoms are common in IRC +10216, reflecting carbon's ability to form multiple strong bonds, unlike oxygen. In VY CMa, a new water maser (v2 = 2) has been found, as well as vibrationally excited NaCl. Toward IRC +10216, vibrationally excited CCH was detected for the first time.

Tenebaum, E. D.↗

DOE OSTI2023

Significance of pH and iron-sulfur chemistry for molybdenum sequestration under sulfidic conditions

Molybdenum (Mo), a redox-sensitive trace metal, plays an important role in recording ancient oxygenation and deoxygenation events as a paleoredox proxy. The mobility and reactivity of Mo in aqueous conditions are closely tied to the chemistry of reduced sulfur and iron species. However, our current knowledge on the formation, structure, stability, and condensation pathways of FeMoS clusters in aqueous settings remains limited, which has driven the current study. In this study, we conducted systematic experiments investigating the interactions between dissolved Mo (initially introduced as molybdate, MoO 4 2– , or tetrathiomolybdate, MoS 4 2– ), ferrous iron (Fe 2+ ), and sulfide (ΣH 2 S aq ) in variously defined abiotic sulfidic systems to determine the external conditions (i.e., pH, and reactant concentrations and ratios) necessary for the formation of solid-phase Fe-Mo sulfides. Solution samples of each system were monitored using ultraviolet-visible spectroscopy (UV–vis) to track the degree of thiolation of dissolved Mo species. Precipitates were analyzed using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to determine their elemental compositions and valences, and structure (i.e., crystalline or amorphous), respectively. All FeMoS precipitates were amorphous and contained 76–90% Mo(IV) and 10–24% Mo(V) with a trend toward lower Mo(IV):Mo(V) ratios with increasing pH. The degree of Mo thiolation, which was strongly dependent on solution pH and Fe 2+ concentrations, greatly affected the amount of Mo sequestered (i.e., an increased degree of Mo thiolation in solution led to an increased amount of Mo in the final FeMoS precipitate). Furthermore, these findings suggest that changes in pH and Fe 2+ concentrations may be responsible for the sulfide-independent variations in Mo behavior observed in euxinic basins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Neutron Total Scattering Analysis of Materials for the Nuclear Fuel Cycle

Here, this paper reviews recent experimental efforts at the University of Tennessee and Oak Ridge National Laboratory to comprehensively characterize the structural details of materials relevant for the nuclear fuel cycle by employing advanced neutron scattering techniques. For the study of nuclear ceramics, neutron scattering offers distinct advantages over traditional laboratory or synchrotron X-ray diffraction, including enhanced sensitivity to elements with a low atomic mass, such as oxygen, nitrogen, and carbon. The key to these efforts is the recent advancement in the neutron scattering infrastructure at the high-flux diffractometers at the Spallation Neutron Source. The high neutron flux at these instruments enables neutron total scattering, a nondestructive bulk technique that simultaneously captures both short-range structural effects through pair distribution function analysis and long-range order through diffraction pattern analysis. This approach is particularly important for a comprehensive description of defective, disordered, or amorphous nuclear materials. The case studies presented here include analyses of the local defect structure in hyperstoichiometric uranium oxides and short-range order of ion-irradiated ceramics. This advanced analytical methodology will improve our understanding of the behavior of materials in extreme environments and contribute to the development of more resilient nuclear materials.

Neutron scattering↗

DOE OSTI2021

Four Isotope-Labeled Recombination Pathways of Ozone Formation

A theoretical approach is developed for the description of all possible recombination pathways in the ozone forming reaction, without neglecting any process a priori, and without decoupling the individual pathways one from another. These pathways become physically distinct when a rare isotope of oxygen is introduced, such as 18 O, which represents a sensitive probe of the ozone forming reaction. Each isotopologue of O 3 contains two types of physically distinct entrance channels and two types of physically distinct product wells, creating four recombination pathways. Calculations are done for singly and doubly substituted isotopologues of ozone, eight rate coefficients total. Two pathways for the formation of asymmetric ozone isotopomer exhibit rather different rate coefficients, indicating large isotope effect driven by ΔZPE-difference. Rate coefficient for the formation of symmetric isotopomer of ozone (third pathway) is found to be in between of those two, while the rate of insertion pathway is smaller by two orders of magnitude. These trends are in good agreement with experiments, for both singly and doubly substituted ozone. The total formation rates for asymmetric isotopomers are found to be somewhat larger than those for symmetric isotopomers, but not as much as in the experiment. Altogether, the distribution of lifetimes is found to be very similar for the metastable states in symmetric and asymmetric ozone isotopomers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1969

Transient color sensitivity of the Hill reaction during the disintegration of chloroplasts

Hill reaction color sensitivity in red and blue light during chloroplast disintegration, considering oxygen evolution capacity

Gaffron, H.↗

NASA NTRS1975

Characteristics and performance study of mass spectrometer residual gas analyzers

Types of instruments studied were magnetic sector, omegatron, quadrupole, and monopole. Experimental results obtained included absolute sensitivity to argon, relative sensitivity to ten gases (hydrogen, helium, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, krypton, and xenon), and cracking patterns for these gases.

Hultzman, W. W.↗

NASA NTRS1989

Measurements of oscillator strengths for EUV emissions of ionized oxygen, nitrogen and sulfur

Oscillator-strength determinations for EUV branching emissions of atomic oxygen, nitrogen and sulfur are reported. The transitions studied were excited using a beam-foil source and both branching ratios and radiative lifetimes were determined. Calculated transition-probability data for multiply-ionized neon and oxygen emissions were used to obtain an in situ relative sensitivity curve for the EUV detection system used. New oscillator strengths for NII, OII, SII, and SIII EUV branching emissions that terminate on metastable states of the respective ions are reported, together with new lifetime data for ionized sulfur emissions.

Ryan, L. J.↗

NASA NTRS1992

Asymptotic analysis with reduced chemistry for the burning of n-heptane droplets

The method of rate-ratio asymptotics is used with reduced chemistry to analyze the flame structure and extinction of an isolated n-heptane droplet burning under quasisteady, spherically symmetrical conditions. The outer transport zones are described by the classical Burke-Schumann solution. The inner reaction zone consists of a thin layer, on the rich side of the flame, where the fuel is consumed, and on the lean side, a broader but still asymptotically thin oxidation layer, where H2 and CO are consumed. Special attention is given to differences in predictions of extinction conditions, caused by different chemical-kinetic approximations in the reduced chemistry, including fuel-chemistry effects through molecules containing more than one carbon atom. From the analysis, extinction diameters for n-heptane droplets are estimated for different pressures and ambient oxygen concentrations. The results show that extinction diameters are extremely sensitive to the number of radicals consumed in breaking down each fuel molecule.

Card, J. M.↗

NASA NTRS2004

Water-Based Pressure Sensitive Paint

Preparation and performance of a water-based pressure sensitive paint (PSP) is described. A water emulsion of an oxygen permeable polymer and a platinum porphyrin type luminescent compound were dispersed in a water matrix to produce a PSP that performs well without the use of volatile, toxic solvents. The primary advantages of this PSP are reduced contamination of wind tunnels in which it is used, lower health risk to its users, and easier cleanup and disposal. This also represents a cost reduction by eliminating the need for elaborate ventilation and user protection during application. The water-based PSP described has all the characteristics associated with water-based paints (low toxicity, very low volatile organic chemicals, and easy water cleanup) but also has high performance as a global pressure sensor for PSP measurements in wind tunnels. The use of a water-based PSP virtually eliminates the toxic fumes associated with the application of PSPs to a model in wind tunnels.

Oglesby, Donald M.↗

NASA NTRS2002

High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated

The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for temperature control and signal conditioning, and packaging designed for high temperatures is necessary for the array to survive the engine environment.

Hunter, Gary W.↗