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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 OSTI2015

Site Dependency of the High Conductivity of Ga 2 In 6 Sn 2 O 16 : The Role of the 7-Coordinate Site

The 6-coordinated cation site is the fundamental building block of the most effective transparent conducting oxides. Ga2In6Sn2O16, however, maintains 4-, 6-, 7-, and 8-coordinated cation sites and still exhibits desirable transparency and high conductivity. To investigate the potential impact of these alternative sites, we partially replace the Sn in Ga2In6Sn2O16 with Ti, Zr, or Hf and use a combined approach of DFT-based calculations, X-ray diffraction, and neutron diffraction to establish that the substitution occurs preferentially on the 7-coordinate site. In contrast to Sn, the empty d orbitals of Ti, Zr, and Hf promote spd covalency with the surrounding oxygen which decreases the conductivity. Pairing the substitutional site preference with the magnitude of this decrease demonstrates that the 7-coordinate site is the major contributor to the conductivity. The optical band gaps, in contrast, are shown to be site independent and composition dependent. Continued replacement of Sn after all 7-coordinate Sn has been substituted results in the formation of a 7-coordinate In antisite or replacement of 6-coordinate Sn, depending on the identity of the d0 substitute.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Precipitation-site competition in duplex stainless steels: Cu clusters vs spinodal decomposition interfaces as nucleation sites during thermal aging

Competing microstructural evolution mechanisms can exist simultaneously when duplex stainless steels are operating for several decades in a high temperature service environment. Such competition between different microstructural evolution pathways can be difficult to ascertain using simple model alloy systems necessitating detailed structural and compositional analysis of phase transformation mechanisms in complex alloys Thus, in this study duplex stainless steels with complex but well understood chemistries were used to investigate the relative importance of different heterogeneous nucleation sites – specifically spinodal decomposition and Cu clustering – on precipitation of Ni-Si-Mn particles during long term thermal aging. Precipitation of Ni-Si-Mn particles in duplex stainless steels and ferritic steels during thermal aging and irradiation is known to have profound effect on mechanical properties. Using duplex stainless steels with custom modified compositions along with atom probe tomography characterization and first-passage kinetic Monte Carlo (FPKMC) simulations it is revealed that while the interface between Cr and Fe formed during spinodal decomposition can be a pathway for diffusion of Ni, Si, Mn, and Cu, it is not a site that encourages precipitation of Ni-Si-Mn rich particles. Instead, the presence of a higher concentration of Cu in these steels leads to formation of small Cu clusters with high energy interfaces that act as nucleation sites for Ni-Si-Mn particles because of its strong interaction particularly with Ni increasing the chemical driving force for precipitation. These results will help inform predictive models for the use of duplex stainless steels and other precipitation-hardened alloys for extended operation at high temperatures.

Duplex stainless steel, Thermal aging, Precipitati↗
DOE OSTI2019

The synergistic effect between Ni sites and Ni-Fe alloy sites on hydrodeoxygenation of lignin-derived phenols

The catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds is a critical step in the upgrading of bio-oil. Here, bimetallic Ni-Fe nanoparticles supported on mesoporous carbon spheres (MCSs) were fabricated and applied in HDO of phenol. In comparison with monometallic Ni and Fe catalysts, the bimetallic Ni-Fe catalyst exhibited better performance for phenol HDO due to the formation of Ni-Fe alloy phase identified by X-ray powder diffraction (XRD) and Mössbauer spectroscopy techniques. Among several explored ratios, the catalysts with Ni/Fe ratio of 3/1 presented the highest cyclohexane yield. The reaction occurred in two consecutive steps: the hydrogenation of phenol to cyclohexanol and the further hydrogenolysis of cyclohexanol to cyclohexane. Kinetic studies showed that the hydrogenolysis of cyclohexanol controlled the overall reaction rate of phenol HDO due to the lower reaction rate of this step. Indeed, the turnover frequency (TOF) values of cyclohexanol normalized by surface metallic Ni sites exhibited a linear correlation with Ni-Fe alloy sites. The alloying of iron in the bimetallic Ni-Fe catalysts significantly enhanced the adsorption strength of cyclohexanol, which is the reason of the high activity of the Ni-Fe alloy particles. Thus, Fe-containing sites adsorb the hydroxyl species while Ni sites perform the H2 activation, their synergistic effect plays a key role in phenol HDO process.

Han, Qiao↗
DOE OSTI2016

2016 Inspection and Annual Site Status Report for the Site A/Plot M, Illinois, Decommissioned Reactor Site July 2016

The Site A/Plot M, Illinois, Decommissioned Reactor Site was inspected on May 17, 2016. The site, located within Cook County forest preserve that is open to the public, was found to be in good condition with one exception. Erosion on top of the grass-covered mound at Plot M continues to be a concern as presented in previous inspections. Ruts form in the soil on top of Plot M as a result of bike traffic using the open field as a pass thru between established bike trails within the forest preserve. Argonne National Laboratory (ANL) who is contracted directly from U.S. Department of Energy (DOE) has filled in the ruts with top soil and reseeding remains an ongoing process. Reseeded areas from 2015 are progressing nicely. No cause for a follow-up inspection was identified. In 2015, ANL plugged and abandoned 8 of 25 monitoring wells (BH41, BH51, BH52, BH54, DH9, DH10, DH13, and DH17). The 17 groundwater monitoring wells remaining at the site were inspected to confirm that they were locked and in good condition. Preliminary environmental monitoring results for 2015 are provided in a draft report titled Surveillance of Site A and Plot M, Report for 2015, prepared by ANL. The report also contains results of an independent analysis conducted by the Illinois Emergency Management Agency on some of the samples collected by ANL in 2015. The draft report states that the results of the surveillance program continue to indicate that the impact of radioactivity at Site A/Plot M is very low and does not endanger the health of those living in the area or visiting the site. The ANL monitoring report will be made available to the public on the DOE Office of Legacy Management public website when it is issued as final. A new county forest preserve campsite opened in 2015 at Bull Frog Lake, which is east of Plot M. Hiking trails connect Bull Frog Lake with Site A/Plot M. The site might receive more traffic from forest preserve visitors now that this new campsite is opened.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Long‐Term Large‐Scale Atmospheric Forcing Data From Three‐Dimensional Constrained Variational Analysis for the ARM SGP Site

Here, this study presents a long‐term three‐dimensional large‐scale forcing data set (VARANAL3D) derived from the three‐dimensional constrained variational analysis (3DCVA) method at the Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site from 2004 to 2018. Building on the same input data sets as the conventional continuous forcing data set (VARANAL), VARANAL3D maintains overall consistency in domain‐averaged fields while introducing spatial variability, offering critical insights into the influence of mesoscale synoptic systems on cloud‐related processes. Evaluations are conducted across four cloud and precipitation regimes: Clear‐sky, Shallow‐clouds, Afternoon‐precipitation, and Nocturnal‐precipitation, presenting high consistency of the domain‐mean forcing data sets while emphasizing the role of subdomain forcing variability particularly in precipitating regimes. Single column model (SCM) simulations demonstrate that subdomain VARANAL3D forcing improves cloud and precipitation representation, with the ensemble outperforming domain‐mean forcing in three cloudy and precipitating regimes. Overall, these results highlight VARANAL3D's value for investigating the impacts of spatial variability of large‐scale forcing on atmospheric processes. The VARANAL3D data set provides new opportunities for evaluating model physics, advancing the development of scale‐aware parameterizations and deepening our understanding of cloud and precipitation dynamics.

Environmental sciences↗
DOE OSTI2015

Human γ-glutamyl transpeptidase 1: Structures of the free enzyme, inhibitor-bound tetrahedral transition states, and glutamate-bound enzyme reveal novel movement within the active site during catalysis [Human gamma-glutamyl transpeptidase: Inhibitor binding and movement within the active site]

γ-Glutamyl transpeptidase 1 (GGT1) is a cell surface, N-terminal nucleophile hydrolase that cleaves glutathione and other γ-glutamyl compounds. GGT1 expression is essential in cysteine homeostasis, and its induction has been implicated in the pathology of asthma, reperfusion injury, and cancer. In this study, we report four new crystal structures of human GGT1 (hGGT1) that show conformational changes within the active site as the enzyme progresses from the free enzyme to inhibitor-bound tetrahedral transition states and finally to the glutamate-bound structure prior to the release of this final product of the reaction. The structure of the apoenzyme shows flexibility within the active site. The serine-borate-bound hGGT1 crystal structure demonstrates that serine-borate occupies the active site of the enzyme, resulting in an enzyme-inhibitor complex that replicates the enzyme's tetrahedral intermediate/transition state. The structure of GGsTop-bound hGGT1 reveals its interactions with the enzyme and why neutral phosphonate diesters are more potent inhibitors than monoanionic phosphonates. These structures are the first structures for any eukaryotic GGT that include a molecule in the active site covalently bound to the catalytic Thr-381. The glutamate-bound structure shows the conformation of the enzyme prior to release of the final product and reveals novel information regarding the displacement of the main chain atoms that form the oxyanion hole and movement of the lid loop region when the active site is occupied. Lastly,tThese data provide new insights into the mechanism of hGGT1-catalyzed reactions and will be invaluable in the development of new classes of hGGT1 inhibitors for therapeutic use.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Migration of noble gas tracers at the site of an underground nuclear explosion at the Nevada National Security Site

As part of an underground gas migration study, two radioactive noble gases and two stable tracer gases were injected into a nuclear explosion test chimney and allowed to migrate naturally. Soil gas samples were collected from a series of boreholes and a range of depths from the shallow subsurface (3 meters) to deeper levels (~160 meters) over a period of eleven months. These samples have provided insights into the development and evolution of the subsurface plume and constrained the relative migration rates of the radioactive and stable gas species. Analysis of the samples concluded that the stable tracer SF6 was consistently enriched in the subsurface samples relative to the radiotracer 127Xe, but the ratios of SF6 and 37Ar remained similar throughout the samples.

Johnson, Christine M.↗
DOE OSTI2019

Hyperspectral vegetation identification at a legacy underground nuclear explosion test site

The detection, location, and identification of suspected underground nuclear explosions (UNEs) are global security priorities that rely on integrated analysis of multiple data modalities for uncertainty reduction in event analysis. Vegetation disturbances may provide complementary signatures that can confirm or build on the observables produced by prompt sensing techniques such as seismic or radionuclide monitoring networks. For instance, the emergence of non-native species in an area may be indicative of anthropogenic activity or changes in vegetation health may reflect changes in the site conditions resulting from an underground explosion. Previously, we collected high spatial resolution (10 cm) hyperspectral data from an unmanned aerial system at a legacy underground nuclear explosion test site and its surrounds. These data consist of visible and near-infrared wavebands over 4.3 km 2 of high desert terrain along with high spatial resolution (2.5 cm) RGB context imagery. In this work, we employ various spectral detection and classification algorithms to identify and map vegetation species in an area of interest containing the legacy test site. Here, we employed a frequentist framework for fusing multiple spectral detections across various reference spectra captured at different times and sampled from multiple locations. The spatial distribution of vegetation species is compared to the location of the underground nuclear explosion. We discover a difference in species abundance within a 130 m radius of the center of the test site.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Transition-metal doped edge sites in vertically aligned MoS2 catalysts for enhanced hydrogen evolution

Highly active and low-cost catalysts for electrochemical reactions such as the hydrogen evolution reaction (HER) are crucial for the development of efficient energy conversion and storage technologies. Theoretical simulations have been instrumental in revealing the correlations between the electronic structure of materials and their catalytic activity, and guide the prediction and development of improved catalysts. However, difficulties in accurately engineering the desired atomic sites lead to challenges in making direct comparisons between experimental and theoretical results. In MoS2, the Mo-edge has been demonstrated to be active for HER whereas the S-edge is inert. Using a computational descriptor-based approach, we predict that by incorporating transition metal atoms (Fe, Co, Ni, or Cu) the S-edge site should also become HER active. Vertically standing, edge-terminated MoS2 nanofilms provide a well-defined model system for verifying these predictions. The transition metal doped MoS2 nanofilms show an increase in exchange current densities by at least two-fold, in agreement with the theoretical calculations. This work opens up further opportunities for improving electrochemical catalysts by incorporating promoters into particular atomic sites, and for using well-defined systems in order to understand the origin of the promotion effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Unreviewed Disposal Question Evaluation: Disposal of the Nevada National Security Site Uranium Powder at the Area 5 Radioactive Waste Management Site, Nevada National Security Site

This Unreviewed Disposal Question Evaluation (UDQE) assesses whether the Nevada National Security Site (NNSS) Uranium Powder (Normal, depleted uranium [DU], low-enriched uranium [LEU]) is suitable for shallow land burial (SLB) at the Area 5 Radioactive Waste Management Site (RWMS) on the Nevada National Security Site.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Compilation of Site Names and Spatial Extents for Sites in the Hanford Site Disposition Database

Several analyses that will be completed as part of the Hanford Composite Analysis (CA) and Cumulative Impact Evaluation (CIE) require the extents of facilities, waste sites, and other locations on the Hanford Site. The purpose of this calculation is to provide spatial extents and consistent naming convention for those locations used as part of the analyses in a single dataset. This calculation documents the process used to develop the dataset.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗