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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Short-Transverse Tensile Fracture Behavior of Thick AA2219 Plate - Effects of Theta (Al2Cu) Particle Size and Distribution

An investigation was conducted to obtain a better understanding on the microstructural characteristics of 5-inch-thick AA2219-T87 plate material and the mechanism that led to the unexpected low ductility in the short-transverse (ST) orientation. Materials characterization techniques were utilized to observe the microstructure of fractured tensile specimens and remnant plate material. The mechanism and cause of low ST ductility in the thick plate material is presented and discussed in this report.

Short-Transverse Orientation↗
NASA NTRSDate not supplied

Exploring the Climatic Impact of Bi-Modal Dust Particle Size Distributions During the MY34/2018 Global Dust Storm with the NASA Ames Mars Global Climate Model.

We have implemented a bi-modal dust lifting scheme in the NASA Ames Mars Global Climate Model (GCM) and investigated the climatic impact on the MY34/2018 Global Dust Storm (GDS). We found that the climate is measurably responsive to the inclusion of a second, smaller dust mode. Dust tends to be lifted through a deeper column in the atmosphere, which is reflected in the climate as changes to atmospheric temperature, tide amplitudes, and surface temperatures. Adding a modest fraction of a smaller dust mode improves simulations during the GDS compared to Curiosity semi-diurnal tide observations as well as Mars Climate Sounder (MCS) T15 brightness temperatures

R A Urata↗
DOE OSTI2025

Morphological Characterization of Uranyl Fluoride Particles via Atomic Force Microscopy

Uranium hexafluoride (UF 6 ) undergoes a rapid hydrolysis reaction when exposed to atmospheric water. In addition to producing hazardous HF gas, the hydrolysis reaction produces uranyl fluoride (UO 2 F 2 ), a radioactive solid phase particulate material. Because of the technological utility of UF 6 in the nuclear fuel cycle, understanding the transport properties of UO 2 F 2 aerosol produced via UF 6 hydrolysis is important for accident scenarios. Moreover, the fundamental chemical and physical properties of the UF 6 hydrolysis reaction are not completely understood. Recently, several experiments on the aerosol phase properties of UO 2 F 2 produced in this way have shown that under most relevant conditions, the particle size distribution (PSD) of UO 2 F 2 can be extremely small, approximately 3 to 5 nm, which is well below the threshold that can be routinely observed via scanning electron microscopy (SEM). Although readily observable in the aerosol phase, observation of nanometer-sized particles in the condensed phase (i.e. deposited on surfaces) remains a challenge. Here, in this study, we have used atomic force microscopy (AFM) to study the PSD and morphological characteristics of UO 2 F 2 deposited at low and high concentrations under different humidity conditions, a primary variable in the hydrolysis reaction. Here, we find strong agreement between PSD measured in the aerosol phase via scanning mobility particle sizing and PSD measured via AFM, with particle sizes peaked below 4 nm for low-humidity conditions. At higher humidity, the distribution is centered around 5 to 10 nm but extends up to 20 nm. These results are in stark contrast to previous measurements using SEM that show PSD on the order of 300- to 1000-nm particle sizes; moreover, these are the first direct measurements of individual particles of UO 2 F 2 having been produced via UF 6 hydrolysis deposited on surfaces. These measurements, therefore, open a new avenue for collecting and detecting UO 2 F 2 in the condensed phase and further refine the PSD, which is critical for environmental transport determinations.

Uranium hexafluoride↗
NASA NTRS2008

Lunar Dust Characterization Activity at GRC

The fidelity of lunar simulants as compared to actual regolith is evaluated using Figures of Merit (FOM) which are based on four criteria: Particle Size, Particle Shape, Composition, and Density of the bulk material. In practice, equipment testing will require other information about both the physical properties (mainly of the dust fraction) and composition as a function of particle size. At Glenn Research Center (GRC) we are involved in evaluating a number of simulant properties of consequence to testing of lunar equipment in a relevant environment, in order to meet Technology Readiness Level (TRL) 6 criteria. Bulk regolith has been characterized for many decades, but surprisingly little work has been done on the dust fraction (particles less than 20 micrometers in diameter). GRC is currently addressing the information shortfall by characterizing the following physical properties: Particle Size Distribution, Adhesion, Abrasivity, Surface Energy, Magnetic Susceptibility, Tribocharging and Surface Chemistry/Reactivity. Since some of these properties are also dependent on the size of the particles we have undertaken the construction of a six stage axial cyclone particle separator to fractionate dust into discrete particle size distributions for subsequent evaluation of these properties. An introduction to this work and progress to date will be presented.

Street, Kenneth W.↗