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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Congo Basin Water Balance and Terrestrial Fluxes Inferred From Satellite Observations of the Isotopic Composition of Water Vapor

Large spatio-temporal gradients in the Congo basin vegetation and rainfall are observed. However, its water-balance (evapotranspiration minus precipitation, or ET - P) is typically measured at basin-scales, limited primarily by river-discharge data, spatial resolution of terrestrial water storage measurements, and poorly constrained ET. We use observations of the isotopic composition of water vapor to quantify the spatio-temporal variability of net surface water fluxes across the Congo Basin between 2003 and 2018. These data are calibrated at basin scale using satellite gravity and total Congo river discharge measurements and then used to estimate time-varying ET - P over four quadrants representing the Congo Basin, providing first estimates of this kind for the region. We find that the multi-year record, seasonality, and interannual variability of ET - P from both the isotopes and the gravity/river discharge based estimates are consistent. Additionally, we use precipitation and gravity-based estimates with our water vapor isotope-based ET - P to calculate time and space averaged ET and net river discharge within the Congo Basin. These quadrant-scale moisture flux estimates indicate (a) substantial recycling of moisture in the Congo Basin (temporally and spatially averaged ET/P > 70%), consistent with models and visible light-based ET estimates, and (b) net river outflow is largest in the Western Congo where there are more rivers and higher flow rates. Our results confirm the importance of ET in modulating the Congo water cycle relative to other water sources.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Ozone depletion in the Arctic and Antarctic stratosphere induced by wildfire smoke

Abstract. A record-breaking stratospheric ozone loss was observed over the Arctic and Antarctica in 2020. Strong ozone depletion occurred over Antarctica in 2021 as well. The ozone holes developed in smoke-polluted air. In this article, the impact of Siberian and Australian wildfire smoke (dominated by organic aerosol) on the extraordinarily strong ozone reduction is discussed. The study is based on aerosol lidar observations in the North Pole region (October 2019–May 2020) and over Punta Arenas in southern Chile at 53.2∘ S (January 2020–November 2021) as well as on respective NDACC (Network for the Detection of Atmospheric Composition Change) ozone profile observations in the Arctic (Ny-Ålesund) and Antarctica (Neumayer and South Pole stations) in 2020 and 2021. We present a conceptual approach on how the smoke may have influenced the formation of polar stratospheric clouds (PSCs), which are of key importance in the ozone-depleting processes. The main results are as follows: (a) the direct impact of wildfire smoke below the PSC height range (at 10–12 km) on ozone reduction seems to be similar to well-known volcanic sulfate aerosol effects. At heights of 10–12 km, smoke particle surface area (SA) concentrations of 5–7 µm2 cm−3 (Antarctica, spring 2021) and 6–10 µm2 cm−3 (Arctic, spring 2020) were correlated with an ozone reduction in terms of ozone partial pressure of 0.4–1.2 mPa (about 30 % further ozone reduction over Antarctica) and of 2–3.5 mPa (Arctic, 20 %–30 % reduction with respect to the long-term springtime mean). (b) Within the PSC height range, we found indications that smoke was able to slightly increase the PSC particle number and surface area concentration. In particular, a smoke-related additional ozone loss of 1–2 mPa (10 %–20 % contribution to the total ozone loss over Antarctica) was observed in the 14–23 km PSC height range in September–October 2020 and 2021. Smoke particle number concentrations ranged from 10 to 100 cm−3 and were about a factor of 10 (in 2020) and 5 (in 2021) above the stratospheric aerosol background level. Satellite observations indicated an additional mean column ozone loss (deviation from the long-term mean) of 26–30 Dobson units (9 %–10 %, September 2020, 2021) and 52–57 Dobson units (17 %–20 %, October 2020, 2021) in the smoke-polluted latitudinal Antarctic belt from 70–80∘ S.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Reversible Crosslinked Polymer Binder for Recyclable Lithium Sulfur Batteries with High Performance

Owing to the negative impact of the extensive utilization of batteries on the environment, sustainability of the cells needs to be included in the systemic research of batteries. In this work, a dissolvable ionic crosslinked polymer (DICP) is exploited as a binder for lithium–sulfur batteries by crosslinking the polyacrylic acid and polyethyleneimine through carboxy-amino ionic interaction. This interaction is pH-controlled, and therefore, the crosslinked binder network can be readily dissociated under basic conditions, providing a facile strategy enabling valuable components recycled through a convenient washing method. The sulfur cathode prepared using the recycled carbon–sulfur composite can deliver comparable capacity as that of fresh electrode. In addition, evidence from cell performance and characterizations, such as in situ X-ray absorption spectroscopy, in situ UV–visible spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation, confirms that DICP is a more effective binder than its commercial counterpart on suppressing polysulfide dissolution in the electrolyte. Exploiting reversible crosslinked polymer binder for recyclable Li–S batteries with ameliorated electrochemical performance, this study illuminates sustainable development for large-scale energy storage systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Selective Antisite Defect Formation in WS 2 Monolayers via Reactive Growth on Dilute W-Au Alloy Substrates

Defects are ubiquitous in 2D materials and can affect the structure and properties of the materials and also introduce new functionalities. Methods to adjust the structure and density of defects during bottom-up synthesis are required to control the growth of 2D materials with tailored optical and electronic properties. In this study, the authors present an Au-assisted chemical vapor deposition approach to selectively form S W and S2 W antisite defects, whereby one or two sulfur atoms substitute for a tungsten atom in WS 2 monolayers. Guided by first-principles calculations, they describe a new method that can maintain tungsten-poor growth conditions relative to sulfur via the low solubility of W atoms in a gold/W alloy, thereby significantly reducing the formation energy of the antisite defects during the growth of WS 2 . The atomic structure and composition of the antisite defects are unambiguously identified by Z-contrast scanning transmission electron microscopy and electron energy-loss spectroscopy, and their total concentration is statistically determined, with levels up to ≈5.0%. Furthermore, scanning tunneling microscopy/spectroscopy measurements and first-principles calculations also verified these antisite defects and revealed the localized defect states in the bandgap of WS 2 monolayers. This bottom-up synthesis method to form antisite defects should apply in the synthesis of other 2D materials.

2D materials↗
DOE OSTI2021

Conducting thermal energy to the membrane/water interface for the enhanced desalination of hypersaline brines using membrane distillation

Membrane distillation (MD) is a membrane-based thermal desalination process capable of treating hypersaline brines. Standard MD systems rely on preheating the feed to drive the desalination process. However, relying on the feed to carry thermal energy is limited by a decline of the thermal driving force as the water moves across the membrane, and temperature polarization. In contrast, supplying heat directly into the feed channel, either through the membrane or other channel surfaces, has the potential of minimizing temperature polarization, increasing single-pass water recoveries, and decreasing the number of heat exchangers in the system. When solar thermal energy can be utilized, particularly if the solar heat is optimally delivered to enhance water evaporation and process performance, MD processes can potentially be improved in terms of energy efficiency, environmental sustainability, or operating costs. Here we describe an MD process using layered composite membranes that include a high-thermal-conductivity layer for supplying heat directly to the membrane-water interface and the flow channel. Here, the MD system showed stable performance with water flux up to 9 L/m 2 /hr, and salt rejection >99.9% over hours of desalinating hypersaline feed (100 g/L NaCl). In addition to bench-scale system, we developed a computational fluid dynamics model that successfully described the transport phenomena in the system.

42 ENGINEERING↗
DOE OSTI2025

Tunable high Néel temperature and large anomalous Hall response in antiferromagnetic Weyl semimetal Mn 3 Sn 1− x Ga x thin films

Antiferromagnetic Weyl semimetals based on Mn 3 X(X = Ge, Sn, Ga) kagome compounds exhibit the same ferromagnetic-like responses, including anomalous Hall, Nernst, and magneto-optical effects, as recently discussed for altermagnets. Driven by the Berry curvature due to Weyl fermions, these materials show a disproportionately large magnitude of electromagnetic effects even in the absence of large magnetization. For applications it is crucial to realize these responses in a wide range of temperatures both below and above 300 K. While stoichiometric Mn 3 X materials do not offer optimal performance, we show that Mn 3 Sn 1−x Ga x sputtered films with a variable composition offers a tunable Néel temperature, T N ≈ 425 ± 6–500 ± 15 K, which is crucial for device applications, together with a large tunable anomalous Hall effect. Our thin film growth method enables continuous and precise control over the film composition between x = 0 and x = 1. Through a detailed magnetization and Hall transport, we establish the magnetic phase diagram for the hexagonal Mn 3 Sn 1−x Ga x . Our results reveal an enhanced T N and antichiral magnetic phase in Ga-doped Mn 3 Sn and an enhanced anomalous Hall magnitude in Sn-doped Mn 3 Ga compared to their stoichiometric undoped forms. Our work demonstrates a route to optimize the technologically relevant antiferromagnets for various applications.

Magnetic properties and materials↗
DOE OSTI2026

Low-voltage syngas synthesis via BPM electrolysis of CO 2 capture and aldehyde solution

A bipolar membrane electrolyzer coupling bicarbonate electrolysis with formaldehyde oxidation directly produces syngas (H 2 : CO = 1) at 1.7 V and 200 mA cm −2 with 200% combined Faradaic efficiency. We demonstrate an electrochemical syngas production platform that couples bicarbonate electrolysis with formaldehyde oxidation in a bipolar membrane electrode assembly. This strategy doubles syngas (CO + H 2 ) throughput compared to conventional CO 2 electrolysis by generating CO at the cathode and H 2 at the anode. The system achieves a full-cell voltage of 1.7 V while operating at an industrially relevant current density of 200 mA cm −2 . The system maintained a combined Faradaic efficiency of 200% over 8 hours. The process produces syngas with a 1 : 1 H 2 : CO ratio, aligning with downstream requirements for Fischer–Tropsch synthesis. We further investigated how Cu anode active sites and electrolyte composition affect formaldehyde oxidation activity. Our integrated electrolytic system reduces levelized energy by 45–61% relative to conventional electrochemical syngas production platforms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

OzDES Reverberation Mapping Program: Stacking analysis with Hβ, Mg ii , and C iv

ABSTRACT Reverberation mapping is the leading technique used to measure direct black hole masses outside of the local Universe. Additionally, reverberation measurements calibrate secondary mass-scaling relations used to estimate single-epoch virial black hole masses. The Australian Dark Energy Survey (OzDES) conducted one of the first multi-object reverberation mapping surveys, monitoring 735 AGN up to z ∼ 4, over 6 years. The limited temporal coverage of the OzDES data has hindered recovery of individual measurements for some classes of sources, particularly those with shorter reverberation lags or lags that fall within campaign season gaps. To alleviate this limitation, we perform a stacking analysis of the cross-correlation functions of sources with similar intrinsic properties to recover average composite reverberation lags. This analysis leads to the recovery of average lags in each redshift-luminosity bin across our sample. We present the average lags recovered for the Hβ, Mg ii, and C iv samples, as well as multiline measurements for redshift bins where two lines are accessible. The stacking analysis is consistent with the Radius–Luminosity relations for each line. Our results for the Hβ sample demonstrate that stacking has the potential to improve upon constraints on the R–L relation, which have been derived only from individual source measurements until now.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Methane Adsorption on Heteroatom-Modified Maquettes of Porous Carbon Surfaces

Experimental and theoretical studies disagree on the energetics of methane adsorption on carbon materials. However, this information is critical for the rational design and optimization of the structure and composition of adsorbents for natural gas storage. The delicate nature of dispersion interactions, polarization of both the adsorbent and the adsorbate, interplay between H-bonding and tetrel bonding, and induced dipole/Coulomb interactions inherent to methane physisorption require computational treatment at the highest possible level of theory. In this study, we employed the smallest reasonable computational model, a maquette of porous carbon surfaces with a central site for substitution and methane binding. The most accurate predictions of methane adsorption energetics were achieved by electron-correlated molecular orbital theory CCSD(T) and hybrid density functional theory MN15 calculations employing a saturated, all-electron basis set. Here, the characteristic geometry of methane adsorption on a carbon surface (“lander approach”) arises due to bonding interactions of the adsorbent π-system with the proximal H–C bonds of methane, in addition to tetrel bonding between the antibonding orbital of the distal C–H bond and the central atom of the maquette (C, B, or N). The polarization of the electron density, structural deformations, and the comprehensive energetic analysis clearly indicate a ∼3 kJ mol –1 preference for methane binding on the N-substituted maquette. The B-substituted maquette showed a comparable or lower binding energy than the unsubstituted, pure C model, depending on the level of theory employed. The calculated thermodynamic results indicate a strategy for incorporating electron-enriched substitutions (e.g., N) into carbon materials as a way to increase methane storage capacity over electron-deficient (e.g., B) modifications. The thermochemical analysis was revised for establishing a conceptual agreement between the experimental isosteric heat of adsorption and the binding enthalpies from statistical thermodynamics principles.

03 NATURAL GAS↗
DOE OSTI2022

Resonance ionization of zirconium

Abstract Measuring the isotopic composition of trace Zr in presolar stardust grains allows us to study the environment of slow neutron-capture nucleosynthesis in asymptotic giant branch stars. Here, we present a newly characterized Zr resonance ionization scheme that can be saturated with state-of-the-art titanium-sapphire lasers and yields a useful yield of (5.4 ± 0.4)%. Resonance ionization is achieved in two steps: after first being excited with a photon at 319.215 nm, neutral Zr atoms are then ionized with a photon at 388.988 nm, where both wavelengths are reported as in vacuum.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Genomic materials design: CALculation of PHAse Dynamics

The CALPHAD system of fundamental phase-level databases, now known as the Materials Genome, has enabled a mature technology of computational materials design and qualification that has already met the acceleration goals of the national Materials Genome Initiative. Here, as first commercialized by QuesTek Innovations, the methodology combines efficient genomic-level parametric design of new material composition and process specifications with multidisciplinary simulation-based forecasting of manufacturing variation, integrating efficient uncertainty management. Recent projects demonstrated under the multi-institutional CHiMaD Design Center notably include novel alloys designed specifically for additive manufacturing. With the proven success of the CALPHAD-based Materials Genome technology, current university research emphasizes new methodologies for affordable accelerated expansion of more accurate CALPHAD databases. Rapid adoption of these new capabilities by US apex corporations has compressed the materials design and development cycle to under 2 years, enabling a new “materials concurrency” integrated into a new level of concurrent engineering supporting an unprecedented level of manufacturing innovation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Depth-discrete metagenomics reveals the roles of microbes in biogeochemical cycling in the tropical freshwater Lake Tanganyika

Lake Tanganyika (LT) is the largest tropical freshwater lake, and the largest body of anoxic freshwater on Earth’s surface. LT’s mixed oxygenated surface waters float atop a permanently anoxic layer and host rich animal biodiversity. However, little is known about microorganisms inhabiting LT’s 1470 meter deep water column and their contributions to nutrient cycling, which affect ecosystem-level function and productivity. Here, we applied genome-resolved metagenomics and environmental analyses to link specific taxa to key biogeochemical processes across a vertical depth gradient in LT. We reconstructed 523 unique metagenome-assembled genomes (MAGs) from 34 bacterial and archaeal phyla, including many rarely observed in freshwater lakes. We identified sharp contrasts in community composition and metabolic potential with an abundance of typical freshwater taxa in oxygenated mixed upper layers, and Archaea and uncultured Candidate Phyla in deep anoxic waters. Genomic capacity for nitrogen and sulfur cycling was abundant in MAGs recovered from anoxic waters, highlighting microbial contributions to the productive surface layers via recycling of upwelled nutrients, and greenhouse gases such as nitrous oxide. Overall, our study provides a blueprint for incorporation of aquatic microbial genomics in the representation of tropical freshwater lakes, especially in the context of ongoing climate change, which is predicted to bring increased stratification and anoxia to freshwater lakes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Visualization of the HIV-1 Env glycan shield across scales

The dense array of N-linked glycans on the HIV-1 envelope glycoprotein (Env), known as the “glycan shield,” is a key determinant of immunogenicity, yet intrinsic heterogeneity confounds typical structure–function analysis. Here, we present an integrated approach of single-particle electron cryomicroscopy (cryo-EM), computational modeling, and site-specific mass spectrometry (MS) to probe glycan shield structure and behavior at multiple levels. We found that dynamics lead to an extensive network of interglycan interactions that drive the formation of higher-order structure within the glycan shield. This structure defines diffuse boundaries between buried and exposed protein surface and creates a mapping of potentially immunogenic sites on Env. Analysis of Env expressed in different cell lines revealed how cryo-EM can detect subtle changes in glycan occupancy, composition, and dynamics that impact glycan shield structure and epitope accessibility. Importantly, this identified unforeseen changes in the glycan shield of Env obtained from expression in the same cell line used for vaccine production. Finally, by capturing the enzymatic deglycosylation of Env in a time-resolved manner, we found that highly connected glycan clusters are resistant to digestion and help stabilize the prefusion trimer, suggesting the glycan shield may function beyond immune evasion.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

Upgrades to the TRIUMF Fast Ion Counter, TRIFIC

TRIFIC, the TRIUMF Fast Ion Counter, is a downstream ionization chamber which provides beam composition monitoring and recoil tagging for in-beam reaction experiments. TRIFIC has been commissioned and deployed for use with radioactive isotope beams at the TRIUMF-ISAC facility. Recently, the detector has been upgraded to include an improved gas window that can accommodate higher beam rates and position-sensitive electrode grids for better position reconstruction.

Gaseous detectors↗
DOE OSTI2025

Summary of Savannah River Site FY24 Salt Waste Qualification Data

Savannah River Mission Completion (SRMC), the Liquid Waste Operations subcontractor at SRS, and Savannah River National Laboratory (SRNL) analyzed samples from Savannah River Site (SRS) Waste Tanks 21H, 41H, and 42H to support qualification of Salt Waste Processing Facility (SWPF) Waste Batches 10, 11, 12, and 13 for processing (the FY24 Salt Batch Qualification samples). These Tanks (i.e. 21H, 41H and 42H) are blend tanks for feed to SWPF. This report focuses on the characterization of the Salt Batch Qualification sub-samples (i.e., any adjustments after qualification or as a part of processing are documented elsewhere). None of the samples displayed any unusual or unexpected characteristics such as large amounts of solids, floating solids, or unusual color. Characterization of these samples confirmed similar chemical composition and characteristics to previous salt waste batches. The analytical results (both rapid, typically 4 weeks, and long-term, typically 8 weeks) for Salt Batches 10, 11, 12, and 13 are now summarized and discussed in this technical report. SRMC-Analytical Laboratory (SRMC-AL), for the first time, provided all the short-term analyses data used in the qualification evaluations of SWPF Salt Batches 10, 11, 12, and 13. These SRMC short-term results are presented along with the results for the long-term analyses provided by SRNL.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Interfacial Connections between Organic Perovskite/n + Silicon/Catalyst that Allow Integration of Solar Cell and Catalyst for Hydrogen Evolution from Water

Abstract The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin‐film semiconductors has triggered interest in their use for direct solar‐driven water splitting to produce hydrogen. However, application of these low‐cost, electronic‐structure‐tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic‐catalyst‐electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n + silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high‐temperature annealing of the catalyst/TiO 2 ‐protected‐n + silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA 1‐x Cs x )PbI 3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro‐OMeTAD‐hole‐transport‐layer (HTL)‐based HOIP/n + Si solar cell, and a high photocurrent density of −15.9 mA cm −2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n + Si/Pt photocathode in 1 m NaOH under simulated 1‐sun illumination. While this thin‐film design creates stable interfaces, the intrinsic photo‐ and electro‐degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices.

08 HYDROGEN↗
DOE OSTI2020

Laser glazing of cold sprayed coatings for the mitigation of stress corrosion cracking in light water reactor (LWR) applications

The effect of laser power, traverse speed, and cold spray coating thickness were examined with the goal of mitigating and repairing stress corrosion cracking (SCC) in light water reactor (LWR) environment. For this purpose, SCC-susceptible Alloy 600 substrate material was coated with SCC-resistant Alloy 690 via the cold spray technique. The cold spray coated substrate was then laser-glazed using various laser parameters. Single pass and multiple pass laser glazed regions were created to determine the effects. For this purpose, the area of the fusion zone, depth of the fusion zone, and elemental composition of the cross section were examined by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Additionally, it was shown that chromium dilution from the laser glazed region into the substrate is not a significant factor in laser glazed cold spray coated samples. Separate laser glazed samples were subjected to ASTM 633C to determine coating adhesion. Finally, by using interrupted SCC crack growth rate tests, it was shown that low traverse speeds and high laser powers produce deep fusion zones within the cold sprayed coating and substrate that can be used to seal pre-existing cracks, thus stopping SCC growth.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Compositional Phase Control in High-Entropy Alloy Electrocatalysts

High-entropy alloys (HEAs) provide uniquely tunable structural and electronic properties that enable robust electrocatalysis. While compositional manipulation of HEAs is well-known, systematically controlling the crystalline phase and morphology remains a challenge that could provide new avenues for controlling reactive sites and physical properties. Here, we show the preferential stabilization of mixed fcc/bcc to fcc phases by controlling the Au content in quinary AuPdFeCoNi HEA nanoparticles. This systematic structural and compositional control, when investigated with an ensemble of electronic, X-ray synchrotron, and surface techniques, allows us to identify the critical short- (few-Å) and medium- (6–10 Å) range structural motifs that deliver exceptional hydrogen evolution reaction (HER) catalysis. Specifically, these HEAs exhibit both outstanding durability (240 h) and high mass activity (50 A/mg PGM ) normalized to noble metal content, outperforming commercial Pt/C (3.18 A/mg PGM ). This structural control over HEA morphology, and its direct association with changes in specific metallic oxidation states and pair–pair atomic structural features, provides new means and strategies for finely designing robust and sustainable electrocatalysts with a majority nonprecious metal composition.

36 MATERIALS SCIENCE↗