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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Quantification of grain rotation in bulk nanostructured copper via in situ heating white beam synchrotron X-ray diffraction

Grain rotation during microstructural relaxation under heating is conventionally studied extensively through transmission electron microscopy and simulations. However, there is a shortage in examining grain rotations at larger length and volume scales in bulk materials. It is critical to understand the thermal stability of bulk nanostructured metals, since those enhanced mechanical properties have been well recognized. Here, this study aimed to employ a white beam microdiffraction X-ray technique under in situ heating from 300 K to 1073 K at 12 K/min on a nanostructured copper processed by high-pressure torsion, yielding an initial grain size of ∼260 nm before the heating. Evaluation across a wide range of temperatures reveals transition temperatures associated with microstructural relaxation processes. By tracking separate Laue diffraction peaks stemming from individual grains, changes in their orientations can be estimated and quantified. This approach becomes particularly effective when the number of grains within the probed volume is reasonably small. At temperatures above 940 K, about 7.5 % of Cu grains are rotating at speeds of ∼2 × 10 –3 °/s. The radial direction of the disk specimen is found to be the preferred direction of grain rotation, with the rotation axis along the shear direction. Further analysis found no correlation between peak intensity and peak size, related to grain sizes and deviatoric strain, respectively, with rotation conditions or speed. These findings demonstrate that the diffraction technique utilizing white beam X-rays is a complementary and novel characterization tool for understanding microstructural evolution, especially in grain rotations, of bulk crystalline materials.

Grain orientation↗
DOE OSTI2023

White Beam Normalization

Raw data used to normalize detector performance on the ARCS instrument For the run cycle starting in June 2023. This is a V cylinder and the T0 chopper is set to 150 Hz and phased for 300 meV. All Fermi Choppers are out of the Beam.

MATERIALS SCIENCE↗
NASA NTRS1997

Characterization of Cadmium-Zinc Telluride Crystals Grown by 'Contactless' PVT Using Synchrotron White Beam Topography

Crystals of Cd(1-x)Zn(x)Te grown by Physical Vapor Transport (PVT) using self-seeding 'contactless' techniques were characterized using synchrotron radiation (reflection, transmission, and Laue back-reflection X-ray topography). Crystals of low (x = 0.04) and high (up to x approx. = 0.4) ZnTe content were investigated. Twins and defects such as dislocations, precipitates, and slip bands were identified. Extensive inhomogeneous strains present in some samples were found to be generated by interaction (sticking) with the pedestal and by composition gradients in the crystals. Large (up to about 5 mm) oval strain fields were observed around some Te precipitates. Low angle grain boundaries were found only in higher ZnTe content (x greater than or equal to 0.2) samples.

Palosz, W.↗
DOE OSTI2024

Synchrotron-based Characterization Techniques for Radiation Detection Materials and Devices: An Overview

High-performance room-temperature radiation detectors (high energy resolution for spectrometers, high spatial resolution for imaging devices, and low defect-density for high flux applications) are needed for photon energies (>20 keV) that are not well suited for silicon detectors. Applications for such radiation detectors include nonproliferation, synchrotron, medical, astrophysics, and homeland security. Material- and device- characterization to understand and solve the limiting factors of radiation detection materials and devices is a core element of a radiation detector development R&D program. This presentation will give an overview on the two main synchrotron-based characterization techniques that have been employed by the authors in the last ~20 years: (1) White Beam X-ray Diffraction Topography and (2) Micron-scale detector mapping. A perfect (one domain) crystal (radiation detection material) is a requirement to achieve a highperformance radiation detector. White Beam X-ray Diffraction Topography (WBXDT) allows the rapid screening of the crystallinity of the detector material. With WBXDT we can quickly screen CZT and other crystals to make sure they have only one domain, and to see the presence of extended defects and strain fields.

Camarda, Giuseppe S.↗
NASA NTRS1998

Experiment 1: Orbital Processing of High-Quality Zn-Alloyed CdTe Compound Semiconductors

Zinc-alloyed cadmium telluride (Zn:CdTe) crystals were grown in unit gravity and in microgravity for comparative analysis. Two crystals were grown on USML-1/STS-50 in 1992, and two additional crystals were grown on USML-2/STS-73 in 1995. The Crystal Growth Furnace (CGF) in the seeded Bridgman-Stockbarger crystal growth geometry was utilized on both missions. Crystals grown on USML-1/STS-50 were found to have solidified with partial wall contact due to the near-absence of the hydrostatic pressure in microgravity, a residual g-vector that was not axial, and the nonwetting sample/ampoule wetting conditions. Crystals grown on USML-2/STS-73 included: a sample/ampoule identical to the USML-1/STS-73 sample/ampoule, with the addition of a restraining spring to simulate hydrostatic pressure internally, and a tapered ampoule which accomplished 2.2 cm of crystal growth without wall contact. Infrared transmission of all ground and flight samples was found to be 63-66 percent, very close to the theoretical 66 percent, suggesting good stoichiometric control. Infrared microscopy confirmed that the primary precipitates were Te and their size (1-10 microns) and density suggested that the flight- and ground-base samples experienced similar thermal histories. Longitudinal macrosegregation, calculated using scaling analysis, was predicted to be low. Nearly diffusion controlled growth was achieved even in unit gravity and macrosegregation data could be fit with a diffusion controlled model. Radial segregation was monitored and was found to vary with fraction solidified, particularly through the shoulder region, where the sample cross section was varying significantly. It was also disturbed in the flight samples in regions where asymmetric wall contact was noted. In regions where a steady state was established, the radial segregation was invariant within our experimental measurement error. Flight samples were found to be much higher in structural perfection than samples processed in unit gravity under identical growth conditions. In regions where solidification had occurred without wall contact, the free surfaces evidenced virtually no twinning, although twins appeared in the flight samples in regions of wall contact and were pervasive in the ground samples. These results were confirmed using optical microscopy and synchrotron x-ray white beam topography. Full-width half-maximum rocking curve widths (FWHM), recorded in arc-seconds, were significantly reduced from 20 a-s (1 g) to 9 a-s (micro-g) for the best regions of the crystals. The 9 a-s (FWHM) rocking curve value in the unconfined flight samples equals the best value reported terrestrially for this material. The ground samples exhibited a fully developed (111)[110] dislocation mosaic structure, whereas dislocations within the flight samples were discrete and no mosaic structure was evident. The defect density was quantitatively reduced from 75,000 (1 g) to 800 (micro-g) +/-50 percent. Dislocation etch pit density results were confirmed using transmission synchrotron white beam and monochromated beam topography. The low defect density is thought to have resulted from the near absence of hydrostatic pressure, which allowed the molten boule to solidify with little or no wall contact. This minimized the transfer of hoop stresses during solidification and post-solidification processing.

Larson, D. J., Jr.↗
DOE OSTI2026

Status and new features of the topography beamline 1-BM after the Advanced Photon Source upgrade

The beamline 1-BM of the Advanced Photon Source (APS), a bending-magnet beamline with an effective X-ray beam size of ~100×4 mm2, has relatively comprehensive synchrotron topography and rocking curve imaging capabilities for characterization of crystals (particularly wide-bandgap semiconductors SiC, AlN, GaN, Ga2O3 etc). It is equipped with a white-beam topography stage for imaging large wafers up to 8 inches. It also has a double-crystal setup, of which the second stage can be used for monochromatic-beam topography. The first stage has different beam conditioners in the grazing-incidence geometry that can expand the vertical beam size from 4 to ~100 mm for double-crystal rocking curve imaging when it is combined with the second stage. Recently APS has been upgraded to a modern 4th-generation light source, and 1-BM has been recommissioned to its normal operation for general users with better performance. The upgraded APS leads to new features at 1-BM. The much smaller source size and higher X-ray coherence significantly improve the image resolution and contrast. The higher flux and brightness of the new source reduce exposure time, which mitigates the mechanical drifting and vibration issues. Here the main capabilities and status of 1-BM together with these new features are introduced.

X-ray topography↗