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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The structure of molten calcium ferrite under various redox conditions

Laser-heated melts based on the 43CaO–57Fe 2 O 3-x eutectic, close to the calcium ferrite (CF) composition, were measured with high-energy X-ray diffraction using aerodynamic levitation over a range of redox states controlled by CO/CO 2 gas atmospheres. The iron–oxygen coordination number was found to rise from 4.4 ± 0.3 at 15% Fe 3+ to 5.3 ± 0.3 at 87% Fe 3+ . Empirical potential structure refinement modelling was used to obtain the ferric and ferrous partial pair distribution functions. It was found that the Fe 2+ iron–oxygen coordination number is consistently approximately 10% higher in CF than in pure iron oxide, while Fe 3+ is essentially identical in all but the most oxygen-rich environments (where it is higher in CF compared with FeO x ). The model also shows calcium octahedra to be the dominant species across all redox environments, although the population of CaO 7 increases with the availability of oxygen at the expense of CaO 4 and CaO 5 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Compatibility of molten plutonium with wrought and additively manufactured metal crucibles

Understanding plutonium’s interaction with metals is crucial for optimizing pyrochemical operations, nuclear fuel containment, and various actinide processing techniques. Traditionally, tantalum crucibles are employed for plutonium processing due to their high durability, excellent temperature stability, and low solubility in plutonium. However, tantalum faces challenges such as plutonium wetting and diffusion, making surface coatings particularly important for crucibles in pyrochemical applications to enhance corrosion resistance against plutonium. Tantalum is also expensive and difficult to machine, prompting the need for advanced manufacturing techniques to address these challenges. Here, in this work, we investigate the interaction of Pu with tantalum and titanium crucibles fabricated using both traditional machining methods and laser powder bed fusion (LPBF) additive manufacturing (AM). LPBF-AM is an advanced technique that allows for the creation of complex geometries from traditionally difficult-to-machine metals by using a high-powered laser to build parts. Previous studies of conventional manufactured tantalum have utilized oxidation and carburization of the surface to mitigate plutonium wetting; however, no studies of surface modified LPBF-AM material have been undertaken. These studies are crucial, given the typical differences in the grain structure between conventional and LPBF-AM materials. All crucibles underwent differential scanning calorimetry to confirm the melting of plutonium. Subsequently, the crucibles were sectioned and mounted in epoxy for microstructural analysis using optical microscopy and scanning electron microscopy. This investigation, comparing the performance of wrought vs AM metal crucibles, provides a basis for future tooling applications in actinide processing techniques and can address the challenges associated with traditional machining, particularly in pyrochemical applications.

Actinides↗
DOE OSTI2023

Ultrafast x-ray detection of low-spin iron in molten silicate under deep planetary interior conditions

The spin state of Fe can alter the key physical properties of silicate melts, affecting the early differentiation and the dynamic stability of the melts in the deep rocky planets. The low-spin state of Fe can increase the affinity of Fe for the melt over the solid phases and the electrical conductivity of melt at high pressures. However, the spin state of Fe has never been measured in dense silicate melts due to experimental challenges. We report detection of dominantly low-spin Fe in dynamically compressed olivine melt at 150 to 256 gigapascals and 3000 to 6000 kelvin using laser-driven shock wave compression combined with femtosecond x-ray diffraction and x-ray emission spectroscopy using an x-ray free electron laser. The observation of dominantly low-spin Fe supports gravitationally stable melt in the deep mantle and generation of a dynamo from the silicate melt portion of rocky planets.

58 GEOSCIENCES↗
DOE OSTI2020

Redox Potential Measurements of Cr(II)/Cr Ni(II)/Ni and Mg(II)/Mg in Molten MgCl 2 –KCl–NaCl Mixture

The redox potential of Ni(II)/Ni, Cr(II)/Cr, and Mg(II)/Mg in MgCl 2 –KCl–NaCl (Magnak chloride) were studied utilizing chronopotentiometry (CP) method in a three-electrode electrochemical cell. Four different CrCl 2 concentrations from 873 K to 1073 K, three NiCl 2 concentrations from 773 K to 1073 K, and two MgCl 2 concentrations from 823 K to 1073 K have been measured. The activity coefficients were calculated referring to a supercooled potential accordingly. The empirical equation of formal potential will be of great significance for the fundamental thermodynamic prediction in high-temperature Magnak chloride systems where corrosion product impurities are present.

14 SOLAR ENERGY↗
DOE OSTI2023

Characterizing Corrosion Mechanisms Of Structural Alloys In Actinide-based Molten Chloride Salt

This is a dataset consisting of 33 GB of .png image files, each featuring a two-dimensional distribution of different element species captured an individual slice of the specimen, and .ang files that capture microstructural information captured from each respective slice using a technique called electron backscatter diffraction. The .ang files can be processed to visualize alloy grains captured in a respective slice.

Copeland, Trishelle M.↗