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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Rate Dependent Multi-Mechanism Discharge of Ag 0.50 VOP 4 ·1.8H 2 O: Insights from In Situ Energy Dispersive X-ray Diffraction

Ag 0.50 VOPO 4 ·1.8H 2 O (silver vanadium phosphate, SVOP) demonstrates a counterintuitive higher initial loaded voltage under higher discharge current. Energy dispersive X-ray diffraction (EDXRD) from synchrotron radiation was used to create tomographic profiles of cathodes at various depths of discharge for two discharge rates. SVOP displays two reduction mechanisms, reduction of a vanadium center accompanied by lithiation of the structure, or reduction-displacement of a silver cation to form silver metal. In-situ EDXRD provides the opportunity to observe spatially resolved changes to the parent SVOP crystal and formation of Ag 0 during reduction. At a C/170 discharge rate V 5+ reduction is the preferred initial reaction resulting in higher initial loaded voltage. At a discharge rate of C/400 reduction of Ag + with formation of conductive Ag 0 occurs earlier during discharge. Discharge rate also affects the spatial location of reduction products. The faster discharge rate initiates reduction close to the current collector with non-uniform distribution of silver metal resulting in isolated cathode areas. The slower rate develops a more homogenous distribution of reduced SVOP and silver metal. This study illuminates the roles of electronic and ionic conductivity limitations within a cathode at the mesoscale and how they impact the course of reduction processes and loaded voltage.

25 ENERGY STORAGE↗
DOE OSTI2013

Advanced Oxide Dispersion Strengthened and Nanostructured Ferritic Alloys

Nanostructured ferritic alloy is a subcategory of oxide dispersion strengthened steels intended for advanced reactor applications. The complex ultrafine grained microstructure of an advanced nanostructured ferritic alloy, as determined by electron microscopy and atom probe tomography, is summarised. Three distinct populations of precipitates were observed: 20–50 nm Ti(N,O,C), 5–10 nm diameter Y2Ti2O7/Y2TiO5 and 1–4 nm diameter Ti,Y,O enriched nanoclusters. The first two populations were predominantly located along grain boundaries together with Cr, W and C segregation. A dense population of nanoclusters was observed both in the grain interior as well as on the grain boundaries. These nanoclusters are highly tolerant to high dose irradiation at elevated temperatures.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2012

Radioactive Cesium Isotope Ratios as a Tool for determining Dispersal and Re-dispersal Mechanisms Downwind from the Nevada Nuclear Security Site

Fractionation of the two longer lived radioactive cesium isotopes (135 and 137) produced by above ground nuclear tests have been measured and used to clarify the dispersal mechanisms of cesium deposited in the area between the Nevada Nuclear Security Site (NNSS) and Lake Mead in the southwestern United States. Fractionation of these isotopes is due to the 135 decay chain requiring several days to completely decay to Cs and the 137 decay chain less than one hour. Since the Cs precursors are gases, iodine and xenon, the 135Cs plume was deposited farther downwind than the 137Cs plume. Samples were obtained from the Las Vegas arm of Lake Mead, separated into segments, gamma counted to identify layers of activity and analyzed for 135Cs/137Cs ratios. The layers proved to have nearly identical highly fractionated isotope ratios. This information is consistent with a model where the cesium was initially deposited onto the land area draining into Lake Mead and the composite from all the above ground shots subsequently washed onto the Lake by high intensity rain and windstorms producing a layering of Cs activity where each layer is a portion of the composite.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗