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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Uptake of aqueous heavy metal ions (Co2+, Cu2+ and Zn2+) by calcium-aluminium-silicate-hydrate gels

Highlights: • C-A-S-H gels containing metal ions (Co{sup 2+}, Cu{sup 2+} or Zn{sup 2+}) were precipitated by a sol-gel technique. • Uptake mechanism and immobilization capacity of divalent metal ions by C-A-S-H are elucidated. • Up to ~55–60 mol% of Zn can be incorporated in defective tobermorite-type C-A-S-H. • Metal uptake by C-A-S-H is controlled mainly by isomorphous substitution for Ca ions. • Crystal-chemical features of C-A-S-H gels and implications for practical application are discussed. Calcium-aluminium-silicate-hydrate (C-A-S-H) gels containing heavy metal ions (Me: Co{sup 2+}, Cu{sup 2+} or Zn{sup 2+}) were precipitated at different Me/Si molar ratios to study the uptake mechanism and immobilization capacity. Aqueous solution chemistry and solid-phase characterization using XRD, FTIR, ESEM-EDX, TEM-HAADF and TG-DSC methods reveal threshold values for ion substitution of ~55–60 mol% for Zn, ~30–40 mol% for Co and ~25–30 mol% for Cu in defective tobermorite-type C-A-S-H with (Ca + Me)/(Si + Al) molar ratios from 0.86 to 1.04. At higher aqueous Me concentrations, Me (chloride) hydroxides start to co-precipitate. The uptake mechanism of Me ions by C-A-S-H is based on (i) isomorphous substitution of Me for Ca in the CaO layer, (ii) ion exchange in the interlayer, (iii) tetrahedral substitution (Zn) within the dreierketten chains and (iv) surface adsorption onto the C-A-S-H gel structure. Systematics in crystal-chemistry of Me-bearing C-A-S-H and implications for application and performance in natural and man-made settings are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Performance enhancement of aqueous ionic liquids with lower critical solution temperature (LCST) behavior through ternary mixtures

Thermally responsive ionic liquids (ILs) exhibit liquid–liquid phase separation when mixed with water and heated above a lower critical solution temperature (LCST), resulting in a water-rich (WR) and an IL-rich (ILR) phase. These binary IL–water mixtures can be employed in a variety of thermodynamic processes such as forward osmosis (FO) desalination, for which two solution properties are desirable: low phase separation temperature and high osmotic strength (osmolality). However, these two properties are interlinked, with ILs that exhibit higher osmotic strengths typically requiring higher phase separation temperatures. This behavior tends to arise from the hydrophilicity of the IL cations, which enhances osmotic strength while also elevating the phase separation temperature. In this work, we highlight a pathway to overcome this tradeoff by developing ternary IL mixtures (two ILs with varying cation hydrophilicity mixed with water), which lowers the phase separation temperature while maintaining and even enhancing the osmotic strength of the solution. We characterize the mixing behavior (osmolality, phase separation temperature, WR phase purity, and WR to ILR phase mass ratio) of four ILs as a function of their concentration in solution. We find that an enhancement of up to 81.6% in the osmolality with a concomitant reduction of up to 15.4% in the phase separation temperature can be achieved using this approach. The ternary mixture is also shown to improve the phase separation kinetics by nearly 95% compared to the binary mixture. Overall, this work highlights a new pathway to improve the performance of LCST ILs for water and energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Coupling Environmental Whole Mixture Toxicity Screening with Unbiased RNA-Seq Reveals Site-Specific Biological Responses in Zebrafish

Passive sampling device (PSD) extracts paired with developmental toxicity assays in Danio Rerio (zebrafish) are excellent sensors for whole mixture toxicity associated with the bioavailable non-polar organics at environmental sites. We expand this concept by incorporating RNA-Seq in 48-h post fertilization zebrafish statically exposed to PSD extracts from two Portland Harbor Superfund Site locations: river mile 6.5W (RM 6.5W) and river mile 7W (RM 7W). RM 6.5W contained higher concentrations of polycyclic aromatic hydrocarbons (PAHs), but the diagnostic ratios of both extracts indicated similar PAH sourcing and composition. Developmental screens determined RM 6.5W to be more toxic with the most sensitive endpoint being a “wavy” notochord malformation. Differential gene expression from exposure to both extracts was largely parallel, although more pronounced for RM 6.5W. When compared to the gene expression associated with individual chemical exposures, PSD extracts produced some gene signatures parallel to PAHs but were more closely matched by oxygenated-PAHs. Additionally, differential expression, reminiscent of the wavy notochord phenotype, was not accounted for by either class of chemical, indicating the potential of other contaminants driving mixture toxicity. These techniques offer a compelling method for non-targeted hazard characterization of whole mixtures in an in vivo vertebrate system without requiring complete chemical characterization.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1972

Chemical features of the Luna 16 regolith sample.

The Luna 16 regolith sample differs from Apollo 11, 12 and 14 regolith and basalt samples by having smaller negative Eu and Sr anomalies and nearly chondritic Eu/Sm and Eu/Sr ratios although the overall REE, Ba, Sr and U concentrations are 25 to 45 times chondrites. Major element data, in particular FeO vs Al2O3, show that the Luna 16 regolith sample is composed of materials that follow a quantitatively different Fe/Al variation than do Apollo 11, 12, 14 and 15 samples. The small Eu and Sr anomalies and the displaced Fe/Al variation are two chemical features unique to the Luna 16 regolith sample. The Luna 16 regolith sample can contain little if any of the rock types abundant at Apollo sites, thus indicating that the unique chemical features are typical of local or nearby materials and indicate a separate petrogenetic province for major component rock types of the Luna 16 regolith.

Hubbard, N. J.↗
NASA NTRS1972

U-Th-Pb analyses of soil from the Sea of Fertility.

Analyses have been made of lead, uranium, and thorium in two soil samples from the Luna 16 mission. Lead was found to be distinctly radiogenic, but significantly less radiogenic than other lunar soils. The Th/U ratio was found to be 3.8, and the uranium concentration was the lowest so far found for lunar soils.

Tera, F.↗
NASA NTRS1978

The blue-to-green reflectance ratio and lake water quality

Correlations between the relative values of the blue and green reflectances of a lake and water quality indices, such as depth of photic zone, Secchi disk transparency, attenuation coefficient, and chlorophyll concentration, have been observed during an intensive satellite, aircraft, and surface vessel study of Lake Ontario and Conesus Lake. Determinations of blue and green reflectances from Skylab S190A color imagery are in excellent agreement with values obtained from small-scale color imagery from aircraft. Further, the accuracy of the satellite data appears within that required for extrapolation to the water quality indices. The study has also determined that changes in chlorophyll, lignin, and humic acid concentration can be discriminated by the behavior of the blue-to-green reflectance ratio and the reflectances of the green and red bands.

Piech, K. R.↗
NASA NTRS1986

Low-temperature deposition of low resistivity ZnSe films by reactive sputtering

The use of reactive dc magnetron cosputtering of Zn and the dopant In in an H2Se/Ar gaseous mixture is described. It is observed that initial deposition using pure Zn targets produced yellowish transparent ZnSe films on glass with a film resistivity of 10 to the 8th ohms cm and deposition using a Zn target doped with a fixed 1 percent of In produced ZnSe films with resistivities of about 10,000 ohms cm. The improvement of film conductivity by optimizing the In content in the ZnSe films is discussed; the ZnSe resistivity dependence on In flux is studied. Optical absorption/transmission measurements reveal a photon energy band gap of 2.65 eV at room temperature and X-ray diffraction show highly oriented polycrystalline films on glass with the c axis parallel to the plane of the film. Compositional analysis was performed and the Zn/Se ratio is measure as 48.8/49.0 with an In concentration of 1.16 percent. ZnSe films deposited on glass and conducting SnO2-coated glass substrates with a resistance of 20 ohms cm and a substrate temperature of 120 C have been fabricated.

Stirn, R. J.↗
NASA NTRS1990

Salt-finger convection under reduced gravity

Salt-finger convection in a double-diffusive system is a motion driven by the release of gravitational potential due to differential diffusion rates. Because of the fact that the destabilizing effect of the concentration gradient is amplified by the Lewis number (the ratio of thermal diffusivity to solute diffusivity) salt-finger convection can be generated at very much reduced gravity levels. This effect may be of importance in the directional solidification of binary alloys carried out in space. The transport of solute and heat by salt-finger convection at microgravity conditions is considered; instability arising from surface tension gradients, the Marangoni instability, is discussed, and the possible consequences of combined salt-finger and Marangoni instability are considered.

Chen, C. F.↗
NASA NTRS1994

Polyimides Containing Silver Trifluoroacetylacetonate

Mechanically strong, flexible, thermally stable, electrically conductive films and coatings suitable for use in electronics industry made by incorporating silver trifluoroacetylacetonate into linear aromatic condensation polyimides. In experimental films, most successful combinations of flexibility and conductivity obtained by use of 1:1, 1:1.74, and 1:2 mole ratios of silver trifluoroacetylacetonate per polyimide repeat unit. Other concentrations of silver trifluoroacetylacetonate used with different heat-treatment schedules to obtain conductive silver-impregnated films.

Stoakley, Diane M.↗
NASA NTRS2002

Combustion Synthesis of Fullerenes and Fullerenic Nanostructures In Microgravity

The objectives of the proposed research were to determine the effects of gravity on fullerenes formation in flames and, based on the observed effects, to develop fundamental understanding of fullerenes formation and to identify engineering principles for fullerenes production. The research method consisted of the operation of laminar diffusion flames under normal- and reduced-gravity conditions, and the collection from the flames and subsequent analysis of condensables including any fullerenes present, using coupled high performance liquid chromatography/mass spectrometry and high resolution transmission electron microscopy. The focus included fullerene molecules C60 and C70 and fullerenic nanostructures including tubes, spherules and other shapes. The normal-gravity experiments were performed at MIT and complementary reduced-gravity experiments were to have been contributed by NASA. The independent variables of interest are gravity, fuel type, fuel/oxygen ratio, pressure, gas velocity at burner, diluent type and concentration. Given the large number of variables and the absence of data on either fullerene formation in diffusion flames or gravitational effects on fullerene formation in diffusion or premixed flames, the first part of the work was exploratory while the later part involved detailed study of the most interesting mechanisms. Samples of condensable material from laminar low pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography to determine the yields of fullerenes, and by high-resolution transmission electron microscopy (HRTEM) to characterize the fullerenic material, i.e., curved-layer nanostructures, on and within the soot particles. The highest concentration of fullerenes was always detected just above the visible stoichiometric surface of a flame. The percentage of fullerenes in the condensable material increases with decreasing pressure. The overall highest amount of fullerenes was found for a surprisingly high dilution fuel with argon. The maximum flame temperature seems to be of minor importance in fullerene formation. The HRTEM analysis of the soot showed an increase of the curvature of the carbon layers, and hence increased fullerenic character. After this maximum, the curvature decreases. In addition to the soot, the samples included fullerenic nanostructures, such as tubes and spheroids including highly-ordered multilayered or onion-like structures. The soot itself shows highly ordered regions that appear to have been cells of ongoing fullerenic nanostructure formation.

Howard, Jack B.↗
NASA NTRS1957

Blow-Out Velocities of Solutions of Hydrocarbons and Boron Hydride - Hydrocarbon Reaction Products in a 1 7/8-Inch-Diameter Combustor

Blow-out velocities were determined for JP-4 solutions containing: (1) 10 % ethylene - decaborane reaction product, (2) 10% and 20% acetylene - diborane reaction product, and (3) 5.5%, 15.7%, and 30.7% methylacetylene - diborane reaction product. These were compared with blow-out velocities for JP-4, propylene oxide, and neohexane and previously reported data for JP-4 solutions of pentaborane. For those reaction products investigated, the blow-out velocities at a fixed equivalence ratio were higher for those materials containing higher boron concentrations; that is, blow-out velocity increased in the following order: (1) methylacetylene - diborane, (2) acetylene - diborane, and (3) ethylene - decaborane reaction products.

Morris, James F.↗
NASA NTRS2006

New Propellants and Cryofuels

The proposed research will investigate the stability and cryogenic properties of solid propellants that are critical to NASA s goal of realizing practical propellant designs for future spacecraft. We will determine the stability and thermal properties of a solid hydrogen-liquid helium stabilizer in a laboratory environment in order to design a practical propellant. In particular, we will explore methods of embedding atomic species and metallic nano-particulates in hydrogen matrices suspended in liquid helium. We will also measure the characteristic lifetimes and diffusion of atomic species in these candidate cryofuels. The most promising large-scale advance in rocket propulsion is the use of atomic propellants; most notably atomic hydrogen stabilized in cryogenic environments, and metallized-gelled liquid hydrogen (MGH) or densified gelled hydrogen (DGH). The new propellants offer very significant improvements over classic liquid oxygen/hydrogen fuels because of two factors: (1) the high energy-release, and (ii) the density increase per unit energy release. These two changes can lead to significant reduced mission costs and increased payload to orbit weight ratios. An achievable 5 to 10 percent improvement in specific impulse for the atomic propellants or MGH fuels can result in a doubling or tripling of system payloads. The high-energy atomic propellants must be stored in a stabilizing medium such as solid hydrogen to inhibit or delay their recombination into molecules. The goal of the proposed research is to determine the stability and thermal properties of the solid hydrogen-liquid helium stabilizer. Magnetic resonance techniques will be used to measure the thermal lifetimes and the diffusive motions of atomic species stored in solid hydrogen grains. The properties of metallic nano-particulates embedded in hydrogen matrices will also be studied and analyzed. Dynamic polarization techniques will be developed to enhance signal/noise ratios in order to be able to detect low concentrations of the introduced species. The required lifetimes for atomic hydrogen and other species can only be realized at low temperatures to avoid recombination of atoms before use as a fuel.

Palasezski, Bryan↗
NASA NTRS2011

Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

Koss, Michael↗
NASA NTRS2014

Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide-humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

humic acid↗
DOE OSTI2026

Validating corrosion models: Influence of physical properties

In chloride containing environments, two metals in physical contact can undergo galvanic corrosion limiting the lifetime of components. Being able to accurately predict galvanic corrosion damage distributions over time has not been widely presented in literature. Therefore, Finite Element Method (FEM) corrosion models were experimentally validated for two galvanic couples as a function of governing equations, environment, anode material, anode:cathode ratio, and time. Carbon steel/stainless steel (CS/SS) and zinc/stainless steel (Zn/SS) galvanic couples were exposed to NaCl solutions at room temperatures for up to 14 days. For the galvanic couples and environments, the Laplace equation with variable conductivity and reactions was sufficient to model the experimental corrosion damage. Increasing the chloride concentration for the CS/SS galvanic couple, regardless of the anode:cathode ratio, decreased the observed and modeled corrosion damage. Decreasing the anode:cathode ratio (i.e., increasing the cathode length), increased the experimentally observed and modeled corrosion damage. For small anode:cathode ratios, the governing equations deviate over long time periods with the Nernst-Plank equation being conservative. For the Zn/SS galvanic couple, the cathode length controls the dominant cathodic reduction reaction. For small cathode lengths, the hydrogen evolution reaction is dominant. For larger cathode lengths, the oxygen reduction reaction is dominant. The results are discussed with regard to the influence of solution chemistry, ohmic drop, and governing reactions. Overall, validated FEM models were presented, and the resultant models, physics, and mechanisms can be applied to other corrosion scenarios with confidence.

Carbon steel↗
NASA NTRS1999

Relative reactivity of ribosyl 2'-OH vs. 3'-OH in concentrated aqueous solutions of phosphoimidazolide activated nucleotides

Phosphoimidazolide activated ribomononucleotides (*pN, see structure) are useful substrates for the non-enzymatic synthesis of oligonucleotides. In the presence of metal ions, aqueous solutions of *pN yield primarily the two internucleotide-linked (pN2' pN and pN3' pN) and the pyrophosphate-linked (N5' ppN) dimers. Small amounts of cyclic dimers and higher oligomers are also produced. In this study the relative reactivity of 2'-OH vs. 3'-OH was determined from the ratio of the yields of pN2' pN vs. pN3' pN. Experiments were performed at 23 degrees C in the range 7.2 < or = pH < or = 8.4 with substrates that differ in nucleobase (guanosine (G), cytidine (C), uridine (U), and adenosine (A)) and leaving group (imidazole (Im), 2-methylimidazole (2-MeIm) and 2,4-dimethylimidazole (2,4-diMeIm)). Two metal ions (Mg2+ or Mn2+) were employed as catalysts. The conditions used here, i.e. a substrate concentration in the range 0.1 M to 1.0 M and metal ion concentration in the range 0.05 M to 0.2 M, favor base-stacking interactions. The ratio pN2' pN: pN3' pN = 2'-5': 3'-5' was found independent of nucleobase and typically varied between 2 to 3 indicating that the 2'-OH is about 2 to 3 times more reactive than the 3'-OH. *pN with Im, compared to 2-MeIm and 2,4-diMeIm leaving group, produce lower yields of internucleotide linked dimers, and a higher pN2' pN: pN3' pN ratio. Trends in the data, observed with all three leaving groups, suggest an increase in pN2' pN: pN3' pN ratio with decreasing substrate concentration (up to 5.47 with 0.051 M ImpG). The observations are in accord with earlier studies reporting a relative reactivity 2'-5': 3'-5' = 6 to 9 obtained with Im as the leaving group, in dilute nucleotide solutions and under conditions that disfavor stacking. It is speculated that the concentration induced change in the relative reactivity is the result of self-association via base-stacking that enhances selectively the proximity of the 3'-OH of one molecule to the reactive P-N bond of an other molecule. The implication of these conclusions for oligomerization/ligation reactions is discussed.

NASA Discipline Exobiology↗
NASA NTRS1976

Mossbauer effect in the ion-implanted iron-carbon alloys

The concentration dependence of Mossbauer effect in four carbon ion-implanted iron absorbers, which contain carbon as the solute atoms, has been investigated over the range of concentration 0.05 through 1 atomic percent. The specimens were prepared by implanting carbon atoms on each reference iron foil with four different bombarding energies of 250 keV, 160 keV, 140 keV and 80 keV, respectively. Thus, the specimen contains a uniform dosage of carbon atoms which penetrated up to 3,000 A depth of the reference iron. In the measurement of Mossbauer spectra, the backscattering conversion electron counting geometry was used. Typical results of Mossbauer parameters of iron-carbon alloys show that the isomer shift, quadrupole shift, the effective hyperfine splitting of Fe-57, and the intensity ratio exhibit a large variation with the increase of carbon concentration in the environment of iron atoms.

Han, K. S.↗