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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Properties of TGS aqueous solution for crystal growth

A study has been made of the properties of triglycine sulfate (TGS) aqueous solution relevant to its use for single crystal growth. Measurements of the solubility, index of refraction, density, viscosity, diffusivity, and optical dispersion are presented and discussed. A knowledge of these properties is of importance for controlling and modeling the growth process and for obtaining high quality single crystals.

Kroes, R. L.↗
NASA NTRS1988

Sulfur isotope effects associated with oxidation of sulfide by O2 in aqueous solution

Normal sulfur isotope effects averaging epsilon = -5.2 +/- 1.4% (s.d.) were consistently observed for the oxidation of sulfide in aqueous solution. Reaction products were sulfate, thiosulfate and sulfite at pH 10.8-11 in distilled water; S0 was formed in two experiments with synthetic seawater at pH 8-9.5. Because the -5.2% normal isotope effect differs significantly from the previously measured +2% inverse effect associated with anaerobic oxidation of sulfide by photosynthetic bacteria, stable sulfur isotopic measurements are potentially useful for distinguishing aerobic vs. anaerobic sulfide oxidation in marine and freshwater sulfureta.

NASA Program Exobiology↗
NASA NTRS1981

Formation of the thioester, N,S-diacetylcysteine, from acetaldehyde and N,N'-diacetylcystine in aqueous solution with ultraviolet light

The thioester, N,S-diacetylcysteine, is formed during the illumination of phosphate buffered (pH 7.0) aqueous solutions of acetaldehyde and N,N'-diacetylcystine with ultraviolet light. The yield of N,S-diacetylcysteine relative to N-acetylcysteine and unidentified products progressively increases as ultraviolet light below 239 nm, 253 nm and 281 nm is cut off with optical filters. When ultraviolet light below 320 nm is removed with an optical filter, there is no detectable reaction. Illumination of 0.025 M N,N'-diacetylcystine with 0.5 M and 1.0 M acetaldehyde with filtered ultraviolet light gives, respectively, 20% and 80% yields of N,S-diacetylcysteine. In the reaction with 1.0 M acetaldehyde, N-acetylcysteine forms early in the reaction and later decreases with its conversion to N,S-diacetylcysteine. The prebiotic significance of these reactions is discussed.

Weber, A. L.↗
DOE OSTI2025

An experimental study of synthetic Hydroxybastnäsite-(La) solubility and speciation in carbonate bearing aqueous solutions at 175–250 °C

The transport and enrichment of rare earth element (REE) ore bodies are dependent on the stability of aqueous metal ligand complexes and the solubility of REE bearing minerals. REE ores are commonly associated with igneous systems having aqueous fluids with high carbonate concentrations and REE solubilities have been shown to be dependent on temperature and associate anion aqueous ligands present in solution. Furthermore, this work presents solubility experiments of hydroxybastnäsite-(La) at elevated temperatures in aqueous solutions of varying carbonate concentrations. At lower temperatures, hydroxybastnäsite-(La) solubility is controlled by neutral mono-carbonate LaCO 3 OH° but at higher temperatures and activities of carbonate species, charged di-carbonate La(CO 3 ) 2 - increases and predominates. This divergence, and the difference in solubility products of other hydroxybastnäsite-(REE) phases, provides a potential mechanism for REE fractionation in carbonate dominated aqueous solutions. To illustrate one such mechanism the solubility data of hydroxybastnäsite-(La) is compared with previously reported data of hydroxybastnäsite-(Nd) at elevated temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Metal–bicarbonate ion pairing in alkaline aqueous solutions from multilevel embedded correlated wavefunction theory and molecular dynamics

In this work, we examine ion-pairing mechanisms of bicarbonates in alkaline aqueous solutions with the divalent metal ions most abundantly present in seawater, namely, Ca 2+ and Mg 2+ . We employ a rare-event enhanced sampling approach within first-principles molecular dynamics to explore regions of phase space spanning solvent-shared to contact ion pairs. Second-order Møller–Plesset perturbation theory (MP2) corrections are subsequently applied in an embedding framework (EMB) to refine the electronic structure of stationary states and associated reaction barriers along the free-energy profiles while retaining the extended solvent effects at the density functional theory (DFT) level. Ca 2+ –HCO 3 − was previously hypothesized to exist in a solvent-shared ion pair (SSHIP) by DFT studies with an endergonic contact ion pair (CIP) formation; however, our EMB-MP2 refinement of the DFT ion-pairing pathways reveals that Ca 2+ and HCO 3 − form a virtually barrier-free CIP in alkaline solutions, with even more energetic ease than the widely studied Ca–CO 3 ion pair. We find qualitative agreement between DFT and EMB-MP2 for Mg 2+ —unlike Ca 2+ , Mg 2+ refuses to shed its strong hydration shell, thereby preferring a SSHIP state with a significant activation barrier to crossover to the CIP forms—a trait reminiscent of ion pairing in Mg–CO 3 and closely related to the kinetic limitations underlying the famous subject of the dolomite problem. Our study highlights the importance of improved electronic structure descriptions of liquids, modeled as a condensed phase of matter lacking in long-range crystalline order. It also strongly suggests that Ca 2+ –HCO 3 − CIPs are likely precursors involved in prenucleation of CaCO 3 mineral formation in seawater.

Sharma, Vidushi [Princeton Plasma Physics Laborato↗
NASA NTRS1991

Refractive properties of TGS aqueous solution for two-color interferometry

Using Cauchy's equation and previously available data, the refractive index versus wavelength relationship for triglycine sulphate aqueous solution has been determined. The variation of the index as a function of the temperature and of the concentration is then obtained using the Murphy-Alpert and the Lorentz-Lorenz relationships respectively. These refractive properties should be useful in relevant crystal growth experiments using two-color holographic and other interferometric diagnostic techniques.

Vikram, Chandra S.↗