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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Validation and Recalibration of the Solubility Models in Support of the Heater Test in Salt Formations

The US Department of Energy Office of Nuclear Energy is conducting a brine availability heater test to characterize the thermal, mechanical, hydrological and chemical response of salt at elevated temperatures. In the heater test, brines will be collected and analyzed for chemical compositions. In order to support the geochemical modeling of chemical evolutions of the brines during the heater test, we are recalibrating and validating the solubility models for the mineral constituents in salt formations up to 100°C, based on the solubility data in multiple component systems as well as simple systems from literature. In this work, we systematically compare the model-predicted values based on the various solubility models related to the constituents of salt formations, with the experimental data. As halite is the dominant constituent in salt formations, we first test the halite solubility model in the Na-Mg-Cl dominated brines. We find the existing halite solubility model systematically over-predict the solubility of halite. We recalibrate the halite model, which can reproduce halite solubilities in Na-Mg-Cl dominated brines well. As gypsum/anhydrite in salt formations controls the sulfate concentrations in associated brines, we test the gypsum solubility model in NaCl solutions up to 5.87 mol•kg –1 from 25 ° C to 50 ° C. The testing shows that the current gypsum solubility model reproduces the experimental data well when NaCl concentrations are less than 1 mol•kg –1 . However, at NaCl concentrations higher than 1, the model systematically overpredicts the solubility of gypsum. In the Na + —Cl – —SO 4 2– —CO 3 2– system, the validation tests up to 100 ° C demonstrate that the model excellently reproduces the experimental data for the solution compositions equilibrated with one single phase such as halite (NaCl) or thenardite (Na 2 SO 4 ), with deviations equal to, or less than, 1.5 %. The model is much less ideal in reproducing the compositions in equilibrium with the assemblages of halite + thenardite, and of halite + thermonatrite (Na 2 CO 3 •H 2 O), with deviations up to 31 %. The high deviations from the experimental data for the multiple assemblages in this system at elevated temperatures may be attributed to the facts that the database has the Pitzer interaction parameters for Cl – —CO 3 2– and SO 4 2– —CO 3 2– only at 25 ° C. Finally, in the Na + —Ca 2+ —SO 4 2– —HCO 3 – system, the validation tests also demonstrate that the model reproduces the equilibrium compositions for one single phase such as gypsum better than the assemblages of more than one phase.

36 MATERIALS SCIENCE↗
DOE OSTI2023

ENDF-6 Formats Manual - Data Formats and Procedures for the Evaluated Nuclear Data Files ENDF/B-VI, ENDF/B-VII and ENDF/B-VIII

This revision of “ENDF-6 Formats Manual” pertains to version 6 of the ENDF formats. The seventh and eighth versions of the ENDF/B library, namely ENDF/B-VII and ENDF/B VIII, use the ENDF-6 format. The manual is based on the previous version of the document, revised in June 2005, In some cases the older version from October 1991 was consulted in order to resolve some ambiguities and errors that were introduced when the reference document was translated from WordPerfect in Word format.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Resolved Molecular Gas and Star Formation Properties of the Strongly Lensed z = 2.26 Galaxy SDSS J0901+1814

We present ~1'' resolution (~2 kpc in the source plane) observations of the CO (1–0), CO (3–2), Hα, and [N II ] lines in the strongly lensed z = 2.26 star-forming galaxy SDSS J0901+1814. We use these observations to constrain the lensing potential of a foreground group of galaxies, and our source-plane reconstructions indicate that SDSS J0901+1814 is a nearly face-on (i ≈ 30°) massive disk with r 1/2 ≳ 4 kpc for its molecular gas. Using our new magnification factors (μ tot ≈ 30), we find that SDSS J0901+1814 has a star formation rate (SFR) of ${268}_{-61}^{+63}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$, ${M}_{\mathrm{gas}}=({1.6}_{-0.2}^{+0.3})\times {10}^{11}({\alpha }_{\mathrm{CO}}/4.6)\,{M}_{\odot }$, and ${M}_{\star }=({9.5}_{-2.8}^{+3.8})\times {10}^{10}\,{M}_{\odot }$, which places it on the star-forming galaxy "main sequence." We use our matched high angular resolution gas and SFR tracers (CO and Hα, respectively) to perform a spatially resolved (pixel-by-pixel) analysis of SDSS J0901+1814 in terms of the Schmidt–Kennicutt relation. After correcting for the large fraction of obscured star formation (${\mathrm{SFR}}_{{\rm{H}}\alpha }/{\mathrm{SFR}}_{\mathrm{TIR}}={0.054}_{-0.014}^{+0.015}$), we find that SDSS J0901+1814 is offset from "normal" star-forming galaxies to higher star formation efficiencies independent of assumptions for the CO-to-H 2 conversion factor. Our mean best-fit index for the Schmidt–Kennicutt relation for SDSS J0901+1814, evaluated with different CO lines and smoothing levels, is $\bar{n}=1.54\pm 0.13;$ however, the index may be affected by gravitational lensing, and we find $\bar{n}=1.24\pm 0.02$ when analyzing the source-plane reconstructions. While the Schmidt–Kennicutt index largely appears unaffected by which of the two CO transitions we use to trace the molecular gas, the source-plane reconstructions and dynamical modeling suggest that the CO (1–0) emission is more spatially extended than the CO (3–2) emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Star Formation at z = 2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation Down to 30 pc Scales

We present measurements of the surface density of star formation, the star-forming clump luminosity function, and the clump size distribution function, for the lensed galaxy SGAS J111020.0+645950.8 at a redshift of z = 2.481. The physical size scales that we probe, radii r = 30–50 pc, are considerably smaller scales than have yet been studied at these redshifts. The star formation surface density we find within these small clumps is consistent with surface densities measured previously for other lensed galaxies at similar redshift. Twenty-two percent of the rest-frame ultraviolet light in this lensed galaxy arises from small clumps, with r<100 pc. Within the range of overlap, the clump luminosity function measured for this lensed galaxy is remarkably similar to those of z∼0 galaxies. In this galaxy, star-forming regions smaller than 100 pc—physical scales not usually resolved at these redshifts by current telescopes—are important locations of star formation in the distant universe. If this galaxy is representative, this may contradict the theoretical picture in which the critical size scale for star formation in the distant universe is of the order of 1 kpc. Instead, our results suggest that current telescopes have not yet resolved the critical size scales of star-forming activity in galaxies over most of cosmic time.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: Explicit modeling of SOA formation from alkane and alkene oxidation

Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C 12 -branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NO x conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. Furthermore, this work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Oxygen Vacancies Enriched Bi Based Catalysts for Enhancing Electrocatalytic CO2 Reduction to Formate

The practical application of CO2 conversion through electrochemical reduction is still hindered by the lack of high performance and cost-effective catalysts. It is thus imperative to explore feasible strategies for scalable fabrication of catalysts for CO2 reduction to targeting products with high efficiency. Herein, for the first time, a hybrid of BiOx encapsulated in carbon thin layer is developed as high active electrocatalyst for CO2 conversion, which is synthesized by pyrolysis using Bi MOF as precursor and sacrificial template. The carbon layer overcoating BiOx catalyst exhibits superior performance for CO2 reduction to formate, achieving a maximum Faradaic efficiency of 89.3 % and a maximum current density of 37.8 mA cm-2. It is found that the as-prepared BiOx catalyst is enriched with oxygen vacancies stabilized by the encapsulating carbon layer. Both the carbon layer and oxygen vacancies improve the charge transfer of the catalyst, in favor of the high formate current density. The defects of oxygen vacancies play a vital role in CO2 adsorption and activation and thereby further enhancing the electrocatalytic ability for formate production.

oxygen vacancy, bismuth, carbon coating, CO2 elect↗
DOE OSTI2017

Effective Pressure Law for the Intrinsic Formation Factor in Low Permeability Sandstones: EPL law for the formation factor

The effective pressure law for the intrinsic formation factor of low permeability sandstones from the Ordos Basin (northwest of China) was studied experimentally by measuring the electrical resistivity of brine saturated rock samples while cycling the pore and confining pressures, p p and p c . We used a 100,000 ppm NaCl solution so that the results could be directly interpreted in terms of the intrinsic formation factor F. The Response Surface method was used to construct a quadratic function of pp and pc fitting the experimental data, from which the coefficient α of the effective pressure law, p eff = p c – αp p , was determined. We found that the coefficient α generally had low values, mainly from 0.2 to 0.4, thus contradicting the theoretical prediction that α should be equal to 1 for scale-invariant properties, such as F, in linear elastic materials having a homogeneous solid matrix. Since the two underlying assumptions, linear elasticity and homogeneity of the solid matrix, are likely violated in reservoir rocks, we tried to assess their effects on α using simple analytical models, based on idealized geometries of the pore and solid phases. Analysis of these models suggests that non-linear elasticity associated with the formation of solid–solid contacts in the compressed rocks (e.g., during closure of rough cracks or crack-like pores along the grain boundaries), may be more effective in producing the low α values observed than inhomogeneity of the solid matrix.

58 GEOSCIENCES↗
DOE OSTI2016

Can Mn–S redox cycling drive sedimentary dolomite formation? A hypothesis

The formation of dolomite in modern peritidal environments is linked to the degradation of buried microbial mats, with complexation of Ca and Mg by extracellular polymeric substances (EPSs) and alkalinity generation through organic carbon respiration facilitating the nucleation of dolomite precursors. In the past two decades, microbial sulfate reduction, methanogenesis, and methanotrophy have all been considered as potential drivers of the nucleation process, but it remains unclear why dolomite formation could not also occur in suboxic sediments where abundant alkalinity is produced by processes linked to Mn(IV) and/or Fe(III) reduction coupled with the diffusion and reoxidation of reduced sulfur species. Here we report the interstitial occurrence of spheroidal aggregates of nanometer-scale Ca-rich dolomite rhombohedra within suboxic sediments associated with remnant microbial mats that developed in the peritidal zone of the Archipelago Los Roques, Venezuela. Multiple analytical tools, including EPMA, ICP-MS, synchrotron-based XRF and XRD, and spatially resolved XANES microanalyses, show that the dolomite-cemented interval exhibits depleted bulk iron concentrations, but is interstitially enriched in Mn and elemental sulfur (S⁰). Manganese occurs in several oxidation states, indicating that the dolomite-cemented interval was the locus of complex biological redox transformations characterized by coupled Mn and S cycling. The tight correspondence between sedimentary Mn and MgCO₃ concentrations further hints at a direct role for Mn during dolomitization. While additional studies are required to confirm its relevance in natural settings, we propose a model by which coupled Mn–S redox cycling may promote alkalinity generation and thus dolomite formation in manner similar to, or even more efficiently, than bacterial sulfate reduction alone.

58 GEOSCIENCES↗
DOE OSTI2024

Mitigation and Diagnosis of Pin-Hole Formation in Polymer Electrolyte Membrane Fuel Cells

In this work, we implement a calendering technique to flatten stray fibers within the gas diffusion media, thereby mitigating pin-hole formation in the hot-pressed MEAs. We have investigated the influence of calendering on the long-term durability for several types of gas diffusion electrodes (GDEs) using a combined chemical and mechanical accelerated stress test (AST). The calendered MEAs demonstrate an average AST lifetime improvement of 77% relative to the as-fabricated MEAs.

AMR↗
DOE OSTI2015

Formation enthalpies of LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

High-temperature oxide melt solution calorimetry using 3Na{sub 2}O·MoO{sub 3} at 802 °C was performed for interlanthanide perovskites LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La{sub 2}O{sub 3}, Ho{sub 2}O{sub 3}, Er{sub 2}O{sub 3}, Tm{sub 2}O{sub 3} and Yb{sub 2}O{sub 3}). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be −8.3±3.4 kJ/mol for LaHoO{sub 3}, −9.9±3.0 kJ/mol for LaErO{sub 3}, −10.8±2.7 kJ/mol for LaTmO{sub 3} and −12.3±2.9 kJ/mol for LaYbO{sub 3}. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds. - Graphical abstract: A linear relationship between the enthalpy of formation and the tolerance factor for interlanthanide LaLn'O{sub 3} (Ln'=Ho, Er, Tm, and Yb) and other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites. - Highlights: • Interlanthanide perovskites were synthesized by solid state reactions. • Their enthalpies of formation were measured by oxide melt solution calorimetry. • ΔH{sub f,ox} shows a linear relationship with tolerance factor.

36 MATERIALS SCIENCE↗