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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

SEM/EBSD Characterization of Baffle-Former Bolts Designated for High Energy X-ray Microscopy Studies at the Advanced Photon Source

This report documents the microstructural and surface characterization of two high-fluence baffle-former bolts (BFBs) harvested from a commercial pressurized water reactor (PWR) after nearly four decades of service. These bolts experienced extreme conditions including high neutron fluence, elevated temperatures, corrosive primary water, and sustained mechanical loads, all of which contribute to degradation mechanisms such as irradiation-assisted stress corrosion cracking (IASCC). Using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), the study assessed bulk and near-surface microstructures, grain boundary characteristics, and in-service oxide layers. The results revealed significant differences between bolts exposed to 41 dpa and 29 dpa, including differences in recrystallization extent, deformation structures, and oxidation morphology. These findings establish critical baseline data for integration with advanced synchrotron-based high-energy X-ray microscopy (HEXM) and computational crystal plasticity models. Ultimately, the work supports improved mechanistic understanding and predictive capability regarding the long-term performance of reactor core internal components.

Lach, Tim [Oak Ridge National Laboratory (ORNL), O↗
DOE OSTI2018

High-Energy-Resolution Resonant Inelastic (Hard) X-ray Scattering (RIXS) at the Advanced Photon Source

Resonant Inelastic X-ray Scattering (RIXS) is a powerful technique for studying electronic excitations in a wide variety of complex materials and environments with momentum-, energy- and potentially polarization resolution. Since its inception, the development of RIXS instrumentation and scientific subjects of study have benefited from a closely intertwined evolution; improvements in energy resolution and throughput, spurred by specific scientific cases, have in turn made new subjects of study feasible. Early RIXS work in the late 1990s was aimed at the study of charge transfer excitations in transition metal oxides (TMO), including the high-Tc superconducting Cuprates, the Nickelates and Manganites, in which the lowest lying excitations across the optical gap at a few eV from the elastic line could be accessed. As the understanding of strongly correlated electron systems progressed, scientific inquiries were directed towards the orbital degrees of freedom: in many Mott insulators the crystal field splits the degeneracy of the active d-orbitals, and the transitions between levels, the dd excitations, generate spectral features at energy losses of <2 eV. These features could reliably be observed with the state-of-the-art resolution at the time of 100-200 meV. In 2008, a ground-breaking paper appeared, that established RIXS as a probe of magnetic excitations. Magnetism and magnetic ordering are central questions in the study of correlated electron systems, however associated spectral features (“magnons”) lie at a fraction of an eV or even in the sub-10meV regime. A significant advance in energy resolution was necessary to study pressing scientific subjects, including magnetic excitations, in the newly discovered Iridate systems. Also, in 2011 a comprehensive review of the RIXS technique was published, which coined the terms “direct RIXS" and “indirect RIXS" and suggested that, for transition metal compounds, RIXS is most productive when employed at L-absorption edges. Thus, research assignments were divided between the soft- x-ray and hard x-ray communities according to L-edge energies: compounds with 3-d elements to the soft, compounds with 5-d elements to the hard x-ray side and other elements somewhere in-between.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Materials Research with X-ray Micro-beams at the Advanced Photon Source

X-ray scattering has had a rich and prominent place in the history of materials research. For samples that are large single crystals, X-ray diffraction provides very detailed, high-quality information about the atomic structure of almost every kind. However, most engineering materials are not a large single crystal, but mixtures of materials or a poly-crystalline material. Still, X-ray diffraction using X-ray beams significantly larger than the structures being investigated has produced much excellent information. Examples of this are powder diffraction, texture analysis, strain analysis, etc. While these types of analyses have been very useful in providing a microscopic understanding, they do not provide the microscopic information that we really want. What we really want to have is this useful X-ray diffraction information for every volume element in our sample; not just the diffraction information about small volume elements, but all of the volume elements, exactly where they are in our sample, and how each one diffracts. Furthermore this detailed spatial and structural information is what is needed for a full understanding of the source of the properties that we find in engineering materials.

36 MATERIALS SCIENCE↗