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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

High-Pressure Studies of Cesium Uranyl Chloride

Here, the pressure behavior of crystalline Cs 2 UO 2 Cl 4 has been explored using a diamond anvil cell. The uranyl fluorescence intensity decreases dramatically with increasing pressure. Using the O–U–O symmetric stretching frequency, an apparent linear decrease in bond length with increasing pressure was observed. A linear decrease in fluorescence intensity with increasing pressure was attributed to a large growth in the nonradiative relaxation, likely attributed to increased relaxation through phonon modes. Quantum theory of atoms in molecules calculations and ab initio wave function methods (CASSCF) support the U≡O bond in UO 2 2+ being highly sensitive to the bond distance, but negligibly affected by the U–Cl bond length.

anions↗
DOE OSTI2019

Dynamics of Water Molecules and Ions in Concentrated Lithium Chloride Solutions Probed with Ultrafast 2D IR Spectroscopy

Water and ion dynamics in concentrated LiCl solutions were studied using ultrafast 2D IR spectroscopy with the methyl thiocyanate (MeSCN) CN stretch as the vibrational probe. The IR absorption spectrum of MeSCN has two peaks, one peak for water associated with the nitrogen lone pair of MeSCN (W) and the other peak corresponding to Li + associated with the lone pair (L). To extract the spectral diffusion (structural dynamics) of W and L species, we developed a method that isolates the peak of interest by subtracting the 2D Gaussian proxies of multiple interfering peaks. Center line slope data (normalized frequency–frequency correlation function) for 2D bands from the W and L are fit with triexponential functions. The fastest component (1.1–1.6 ps) is assigned to local hydrogen bond length fluctuations. The intermediate timescale (~4.0 ps) corresponds to the hydrogen bond network rearrangement. The slowest component decays in ~40 ps and corresponds to ion pair and ion cluster dynamics. The very similar W and L spectral diffusion indicates that the motions of the water and ions are strongly coupled. Orientational relaxations of the W and L species were extracted using a new method to eliminate the effects of overlapping peaks. The results show that MeSCN bound to water undergoes orientational relaxation significantly faster than MeSCN bound to Li + . The orientational and spectral diffusion results are compared. In conclusion, a Stark coupling model is used to extract the root mean square average electric field caused by the ion clouds along the CN moiety as a function of concentration.

14 SOLAR ENERGY↗
DOE OSTI2013

Low temperature atomic layer deposition of highly photoactive hematite using iron(iii) chloride and water

Nanostructured hematite (α-Fe2O3) has been widely studied for use in a variety of thin film applications including solar energy conversion, water oxidation, catalysis, lithium-ion batteries, and gas sensing. Among established deposition methods, atomic layer deposition (ALD) is a leading technique for controlled synthesis of a wide range of nanostructured materials. In this work, ALD of Fe2O3 is demonstrated using FeCl3 and H2O precursors at growth temperatures between 200 and 350 °C. Self-limiting growth of Fe2O3 is demonstrated with a growth rate of ~0.6 Å per cycle. As-deposited, films are nanocrystalline with low chlorine impurities and a mixture of α- and γ-Fe2O3. Post-deposition annealing in O2 leads to phase-pure α-Fe2O3 with increased out-of-plane grain size. Photoelectrochemical measurements under simulated solar illumination reveal high photoactivity toward water oxidation in both as-deposited and post-annealed films. Planar films deposited at low temperature (235 °C) exhibit remarkably high photocurrent densities ~0.71 mA cm-2 at 1.53 V vs. the reversible hydrogen electrode (RHE) without further processing. Films annealed in air at 500 °C show current densities of up to 0.84 mA cm-2 (1.53 V vs. RHE).

36 MATERIALS SCIENCE↗