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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

High temperature mechanical properties of fluorite crystal structured materials (CeO 2 , ThO 2 , and UO 2 ) and advanced accident tolerant fuels (U 3 Si 2 , UN, and UB 2 )

The mechanical interaction between the fuel and cladding that occurs during operation of a nuclear reactor is important to understand as it can lead to cladding failures and release of radioactive material into the coolant. Additionally, in order to develop better models of the pellet-clad mechanical interactions, the mechanical properties of the fuel at relevant operating temperatures, like the elastic moduli, are needed for current and advanced accident tolerant fuels (ATFs). In this work, elevated temperature nanoindentation and resonant ultrasound spectroscopy were used to measure the moduli and hardness of several fluorite materials (CeO 2 , ThO 2 , UO 2 ) and several ATF candidates (ATF) (U 3 Si 2 , UN, UB 2 ). In addition, a comparison of the two techniques was performed in this study to independently validate the mechanical properties.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Dependence of simulated radiation damage on crystal structure and atomic misfit in metals

This study investigates the evolution of radiation damage in three metals in the low temperature and high radiant flux regime using molecular statics and a Frenkel pair accumulation method to simulate up to 2.0 displacements per atom. The metals considered include Fe, equiatomic CrCoNi, and a fictitious metal with similar bulk properties to the CrCoNi composed of a single atom type referred to as an A-atom. CrCoNi is found to sustain higher concentrations of dislocations than either the Fe or A-atom systems and more stacking faults than the A-atom system. The results suggest that the difference between the concentrations of vacancies and interstitials is substantially smaller for CrCoNi than the A-atom system, perhaps reflecting that the sink capture radius is smaller in CrCoNi due to the roughened potential energy landscape. A model that partitions the major contributions from defects to the stored energy is described, and serves to highlight a general need for higher fidelity approaches to point defect identification.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Consequences of long-term water exposure for bulk crystal structure and surface composition/chemistry of nickel-rich layered oxide materials for Li-ion batteries

Water exposure of layered nickel-rich transition metal oxide electrodes, widely used in high-energy lithium-ion batteries, has detrimental effects on the electrochemical performance, which complicates electrode handling and prevents implementation of environmentally benign aqueous processing procedures. Elucidating the degradation mechanisms in play may help rationally mitigate/circumvent key challenges. Here, the bulk structural consequences of long-term (>2.5 years) deuterated water (D2O) exposure of intercalation materials with compositions Li x Ni 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) and Li x Ni 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) are studied by neutron powder diffraction (NPD). Detailed inspection of the NPD data reveals gradual formation of a secondary crystalline phase in all exposed samples, not previously reported for this system. This unknown phase forms faster in liquid- compared to vapor-exposed compounds. Structural modelling of the NPD data shows a stable level of Li/Ni anti-site defects and does not indicate any significant changes in lattice parameters or hydrogen-lithium (D + /Li + ) exchange in the structure. Consequently, the secondary phase formation must take place via transformation rather than modification of the parent material. X-ray photoelectron spectroscopy data indicate formation of LiHCO 3 /Li 2 CO 3 at the surface and a Li-deficient oxide in the sub-surface region of the pristine compounds, and the presence of adsorbed water and transition metal hydroxides at the exposed sample surfaces.

25 ENERGY STORAGE↗
DOE OSTI2021

Crystal structure, magnetic properties and bonding analysis of M 3 Pt 23 Ge 11 (M=Ca, Sr, Ba and Eu)

The properties of Pt-based materials can be intriguing due to the importance of spin-orbit coupling for Pt. Herein, we report four new phases with formulas M 3 Pt 23 Ge 11 (M ​= ​Ca, Sr, Ba and Eu), which adopt the same structure type as Ce3Pt23Si11. Magnetic susceptibility measurements indicate that none of the phases is superconducting above 1.8 ​K, while for Eu 3 Pt 23 Ge 11 ferromagnetic ordering is observed at ~ 3 ​K. The low Curie temperature for that material compared to that of Eu 3 Pt 23 Si 11 may be due to its larger Eu–Eu distance. One potential factor that destabilizes the structure of other rare-earth based M 3 Pt 23 Ge 11 is demonstrated through COHP calculations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of oxidant gas for atomic layer deposition on crystal structure and fatigue of ferroelectric Hf x Zr 1-x O 2 thin films

TiN/Hf x Zr 1-x O 2 (HZO)/TiN capacitors were prepared using two types of HZO films fabricated by atomic layer deposition using H 2 O or O 2 plasma as an oxidant gas, and post-deposition annealing at 400 °C was performed before the TiN top-electrode fabrication. The ferroelectric orthorhombic phase was dominantly formed for the O 2 plasma-based capacitor due to the strongly oxidizing source of O 2 plasma, resulted in higher remanent polarization (2P r = 20 µC/cm 2 ) than that (13 µC/cm 2 ) of the H 2 O-based capacitor. The fatigue properties for the O 2 plasma-based capacitor were improved by 14 % after 106 cycles compared to the H 2 O-based capacitor. This could be attributed to an oxygen-rich interface reaction layer (IRL) including TiO x between the HZO film and TiN bottom-electrode for the O 2 plasma-based capacitor. In conclusion, based on these results, superior 2P r and fatigue properties can be obtained using O 2 plasma-based HZO films.

36 MATERIALS SCIENCE↗