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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 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Porous transport electrodes for oxygen evolution reaction in proton exchange membrane water electrolysis -cells: Materials, designs, and diagnoses

H 2 production using proton exchange membrane (PEM) water electrolysis (PEMWE) cells has received considerable attention because of the high efficiencies of these cells and no harmful emissions from the related process. In PEMWE cells, porous transport electrodes (PTEs) composed of a catalyst layer (CL) comprising O 2 evolution reaction (OER) catalysts, porous transport layer (PTL), and PEM play key roles in the stack performance and lifetime. Herein, Ir-based and non-precious-metal OER catalysts that are highly active and stable at low pH values and high anodic potentials are reviewed to understand their OER mechanisms. Various strategies are proposed for engineering CLs and PTLs to improve the interfacial properties and mass transfers of reactants and products to and from the active sites. Additionally, diagnoses of PTEs is significantly crucial for interpreting electrochemical processes and addressing their current challenges. Therefore, half-cell analyses, including diffusion electrode (DE), floating electrode (FE), and modified rotating disk electrode (MRDE) techniques, are explored, and membrane electrode assembly (MEA)-based analyses, such as the polarization technique, electrochemical impedance spectroscopy, and magnetic field analysis, are established. In conclusion, this study aims to provide an overview of recent technologies used for the engineering and diagnostic tools of PEMWE cells and insights into the advanced components and systems to be developed in this field.

Diagnosis of PEMWE Cells↗
DOE OSTI2023

Modeling diffusion and types I-V sorption of water vapor in heterogeneous systems

Here, a sorption and diffusion model is developed using a mobile-immobile decomposition of the vapor concentration. Henry’s mode represents the mobile species which diffuses through the solid, while Langmuir and pooling modes represent possible immobilization processes that cause nonlinearities in sorption capacity. The model can simulate the five classical sorption types and can incorporate additional dynamics compared to models based on thermodynamic equilibrium. Additionally, the framework allows for discontinuities in material properties encountered in multi-material systems. The resulting non-linear coupled equations are solved by employing a finite element method to discretize in space, and a backward Euler method to discretize in time. The discretized system of equations is solved via a Newton-type iteration scheme at each time-step. Four different materials are parameterized for the model, which are then used in examples to demonstrate the model’s ability to capture complex sorption processes in multi-material systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Can Mn–S redox cycling drive sedimentary dolomite formation? A hypothesis

The formation of dolomite in modern peritidal environments is linked to the degradation of buried microbial mats, with complexation of Ca and Mg by extracellular polymeric substances (EPSs) and alkalinity generation through organic carbon respiration facilitating the nucleation of dolomite precursors. In the past two decades, microbial sulfate reduction, methanogenesis, and methanotrophy have all been considered as potential drivers of the nucleation process, but it remains unclear why dolomite formation could not also occur in suboxic sediments where abundant alkalinity is produced by processes linked to Mn(IV) and/or Fe(III) reduction coupled with the diffusion and reoxidation of reduced sulfur species. Here we report the interstitial occurrence of spheroidal aggregates of nanometer-scale Ca-rich dolomite rhombohedra within suboxic sediments associated with remnant microbial mats that developed in the peritidal zone of the Archipelago Los Roques, Venezuela. Multiple analytical tools, including EPMA, ICP-MS, synchrotron-based XRF and XRD, and spatially resolved XANES microanalyses, show that the dolomite-cemented interval exhibits depleted bulk iron concentrations, but is interstitially enriched in Mn and elemental sulfur (S⁰). Manganese occurs in several oxidation states, indicating that the dolomite-cemented interval was the locus of complex biological redox transformations characterized by coupled Mn and S cycling. The tight correspondence between sedimentary Mn and MgCO₃ concentrations further hints at a direct role for Mn during dolomitization. While additional studies are required to confirm its relevance in natural settings, we propose a model by which coupled Mn–S redox cycling may promote alkalinity generation and thus dolomite formation in manner similar to, or even more efficiently, than bacterial sulfate reduction alone.

58 GEOSCIENCES↗
DOE OSTI2019

Fe-based ceramic nanocomposite membranes fabricated via e-spinning and vacuum filtration for Cd 2+ ions removal

Here, vacuum filtered and polymer mixed e-spinning membranes (ESPMs) made from or doped with Fe-based nanomaterials were successfully fabricated to remove Cd 2+ ions from a neutral aqueous solution. The used Fe-based nanomaterials including FeOOH precursor Nanowires (NWs), α-Fe 2 O 3 NWs and Fe 3 O 4 nanoparticles (NPs) were synthesized by elevating the hydrothermal reaction temperature from 250 °C to 500 °C or doing post-heating treatment. The adsorption results showed that vacuum filtered membranes (VFMs) overall performed a better Cd 2+ ions removal behavior than e-spinning ones. Among them, VFM made from Fe 3 O 4 NPs has the highest adsorption capacity (qt) with the adsorption amount of Cd 2+ ions reaching about 29.3 mg/g within only 2 min due to the high specific surface area of NPs. Models of pseudo-first-order, pseudo-second-order and intraparticle diffusion were used to study the kinetics of Cd 2+ ions removal process, and a high correlation coefficient (R 2 ) of 0.99 was obtained when pseudo-second-order model was used. It was measured that the equilibrium rate constant of VFM made from Fe 3 O 4 NPs has reached about 0.28 g mg –1 min –1 , much smaller than those of other membranes, which suggested a high Cd 2+ ions removal efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

A snapshot of high-entropy alloy processing techniques and their effects on resulting mechanical properties

High-entropy alloys (HEAs) exhibit exceptional strength, corrosion resistance, and thermal stability, making them promising candidates for nuclear, aerospace, and other extreme applications. While most prior work has focused on compositional design, manufacturing techniques themselves can alter microstructure and mechanical properties as dramatically as alloy chemistry. This review compiles and compares the effects of processing routes—including arc melting, induction melting, mechanical alloying with spark plasma sintering, and additive manufacturing—on the structure and properties of HEAs. Quantitative comparisons highlight, for example, that SPS-processed alloys can achieve ∼20–45 % higher yield and tensile strength than arc-melted counterparts, while Bridgman solidification produces nearly single-crystal structures with elongation to failure exceeding 80 %. Additive manufacturing routes such as selective laser melting offer fine microstructures but also introduce anisotropy and porosity, leading to yield strengths spanning 100–600 MPa for the same composition. By synthesizing such results, this review provides actionable insight into how processing routes interact with HEA core effects (high entropy, lattice distortion, sluggish diffusion, and cocktail effect) to determine performance, thereby offering a practical guide for optimizing manufacturing strategies.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Investigations on the multiple-sector hard-copper X-band accelerating structures

The development of advanced, high gradient accelerating structures is one of the leading activity of the particle accelerator community. In the technological research of new construction methods for these devices, high-power testing is a critical step for the verification of their viability. Recent experiments showed that accelerating cavities made out of hard copper, fabricated without high-temperature processes, can achieve better performance as compared with soft copper ones. Recently, we have built cavities using Tungsten Inert Gas welding and the high-power experiments confirmed that this joining process is a robust and low-cost alternative to brazing or diffusion bonding. This is a good solution for high-gradient operation, with a gradient of about 150 MV/m in X-band, at a breakdown rate of 10 -3 /pulse/meter using a shaped RF pulse with a 150 ns flat part. We continue the design, construction and high power tests of three-cells standing-wave X-band accelerating cavities fabricated with a split-open geometry, made of hard copper and vacuum-sealed by welding. Our aim is the fabrication of accelerating structures made out of hard copper alloys by using innovative cost-effective technologies. Moreover, our method of multiple-sector structures opens the way to new technological approaches and design methods, for example providing the possibility of placing dampers of the parasitic higher-order modes. Such structures with dampers allow for acceleration of multi-bunch beams, both in standing and in travelling-wave accelerating modality. Here, this paper describes the design of two cavities made of multiple sectors that were fabricated at the Italian Institute for Nuclear Physics in Frascati, Italy (INFN-LNF), assembled by means of clamping and then joined with the Tungsten Inert Gas welding in order to preserve the hardness of the metal. These are three-cell standing-wave X-band accelerating cavities, to be operated in the π-mode. We report the low-power RF tests of the first one, made of two halves, and the RF design of the second one, made of four quadrants. Both structures were built for high-gradient tests at SLAC National Accelerator Laboratory.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Heat conduction in an irregular magnetic field. Part 2. Heat transport as a measure of the effective non-integrable volume

Given the large anisotropy of transport processes in magnetized plasmas, the magnetic field structure can strongly impact heat diffusion: magnetic surfaces and cantori form barriers to transport while chaotic layers and island structures can degrade confinement. When a small but non-zero amount of perpendicular diffusion is included, the structure of the magnetic field becomes less important, allowing pressure gradients to be supported across chaotic regions and island chains. We introduce a metric for the effective volume over which the local parallel diffusion dominates based on the solution to the anisotropic heat diffusion equation. To validate this metric, we consider model fields with a single island chain and a strongly chaotic layer for which analytic predictions of the relative parallel and perpendicular transport can be made. We also analyse critically chaotic fields produced from different sets of perturbations, highlighting the impact of the mode number spectrum on the heat transport. Our results indicate that this metric coincides with the effective volume of non-integrability in the limit $\kappa _{\perp } \rightarrow 0$ , where $\kappa_{\perp}$ is the perpendicular diffusion coefficient. We propose that this metric be used to assess the impact of non-integrability on the heat transport in stellarator equilibria.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Gd 12 Co 5.3 Bi and Gd 12 Co 5 Bi, Crystalline Doppelgänger with Low Thermal Conductivities

Attempts to prepare Gd 12 Co 5 Bi, a member of the rare-earth (RE) intermetallics RE 12 Co 5 Bi, which were identified by a machine-learning recommendation engine as potential candidates for thermoelectric materials, led instead to formation of the new compound Gd 12 Co 5.3 Bi with a very similar composition. Phase equilibria near the Gd-rich corner of the Gd–Co–Bi phase diagram were elucidated by both lab-based and variable-temperature synchrotron powder X-ray diffraction, suggesting that Gd 12 Co 5.3 Bi and Gd 12 Co 5 Bi are distinct phases. The higher symmetry structure of Gd12Co5.3Bi (cubic, space group $Im\bar{3}$, Z = 2, a = 9.713(6) Å), as determined from single-crystal X-ray diffraction, is closely related to that of Gd12Co5Bi (tetragonal, space group Immm). Single Co atoms and Co–Co dumbbells are disordered with occupancies of 0.78(2) and 0.22(2), respectively, in Gd 12 Co 5.3 Bi, but they are ordered in Gd 12 Co 5 Bi. Consistent with this disorder, the electrical resistivity shows less dependence on temperature for Gd 12 Co 5.3 Bi than for Gd 12 Co 5 Bi. The thermal conductivity is low and reaches 2.8 W m –1 K –1 at 600 °C for both compounds; however, the temperature dependence of the thermal conductivity differs, decreasing for Gd 12 Co 5.3 Bi and increasing for Gd 12 Co 5 Bi as the temperature increases. Here, the unusual trends in thermal properties persist in the heat capacity, which decreases below 2R, and in the thermal diffusivity, which increases at higher temperatures.

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

Insights into the Interconnection of the Electrodes and Electrolyte Species in Lithium–Sulfur Batteries Using Spatially Resolved Operando X-ray Absorption Spectroscopy and X-ray Fluorescence Mapping

The lithium–sulfur (Li–S) battery chemistry has attracted great interest in the last decade because of its outstanding theoretical gravimetric energy density compared to the state-of-the-art lithium-ion battery technology. However, practically achieved energy density is still far below the theoretical value, even in small laboratory-scale batteries. The problems seen in laboratory-scale batteries will inevitably increase during scale-up to large application-format cells, as the electrolyte to active material (AM) ratio will need to be reduced in these cells to achieve high gravimetric energy density on cell-level basis. Our paper shows the unique possibility of X-ray fluorescence (XRF) mapping to visualize the spatial distribution of the AM inside operating Li–S batteries in all cell components [working electrode (WE), separator, and counter electrode (CE)]. Through a combination of operando XRF mapping and X-ray absorption spectroscopy, we show that unless self-discharge is efficiently prevented, the AM can completely dissolve and distribute throughout the cell stack within a time frame of 2 h, causing poor capacity retention. Finally, using a polysulfide diffusion barrier between the WE and the CE, we successfully suppress these processes and thereby establish a tool for examining the sealed cathode electrode compartment, enabling sophisticated studies for future optimization of the WE processes.

25 ENERGY STORAGE↗
DOE OSTI2019

Evolution of Solid Electrolyte Interface on TiO 2 Electrodes in an Aqueous Li-Ion Battery Studied Using Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) was applied for in situ visualization of solid electrolyte interface (SEI) evolution on the TiO 2 anode in a concentrated aqueous electrolyte during cycling. In nonaqueous electrolytes, the SEI is an electronic insulative layer composed of organic and inorganic components covering the electrode surface. However, in concentrated aqueous electrolytes, the SEI is mostly composed of inorganic compounds formed by electrolyte decomposition, such as LiF and Li 2 CO 3 , which are randomly distributed over the TiO 2 surface. In addition, the Ti 3+ and Li residuals accumulated through multiple cycling lead to an increase in the overall electronic conductivity of the TiO 2 anode. Furthermore during the resting period after cycling, an inverse process is observed with partial dissolution of the formed SEI and the diffusion of Li residuals back into the electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2020

Fundamentals of Au(111) Surface Dynamics: Coarsening of Two-Dimensional Au Islands

Au(111) surfaces play a central role in many applications, yet studies of fundamental aspects of their dynamics are limited. Thus, using scanning tunneling microscopy (STM) at 300 K, we analyze the coarsening of first-layer 2D Au islands directly on the Au(111) substrate and also of second-layer 2D Au islands. Specifically, we monitor the decay of Au first-layer islands with areas of about 100–500 nm 2 in the vicinity of larger islands or extended step edges over a period of approximately 40 h, the relevant time scale for this process. Experimentally observed behavior is captured by analytical theory for terrace-diffusion-limited decay incorporating DFT results for the Au terrace diffusion barrier and the adatom formation energy.Lastly, experimental observations of second-layer island decay are also compared with appropriate analytical theory and stochastic simulations, thereby determining the effective Ehrlich–Schwoebel barrier for Au on Au(111).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Long-range exciton transport and slow annihilation in two-dimensional hybrid perovskites

Two-dimensional hybrid organic-inorganic perovskites with strongly bound excitons and tunable structures are desirable for optoelectronic applications. Exciton transport and annihilation are two key processes in determining device efficiencies; however, a thorough understanding of these processes is hindered by that annihilation rates are often convoluted with exciton diffusion constants. Here we employ transient absorption microscopy to disentangle quantum-well-thickness-dependent exciton diffusion and annihilation in twodimensional perovskites, unraveling the key role of electron-hole interactions and dielectric screening. The exciton diffusion constant is found to increase with quantum-well thickness, ranging from 0.06 ± 0.03 to 0.34 ± 0.03 cm 2 s –1 , which leads to long-range exciton diffusion over hundreds of nanometers. The exciton annihilation rates are more than one order of magnitude lower than those found in the monolayers of transition metal dichalcogenides. The combination of long-range exciton transport and slow annihilation highlights the unique attributes of two-dimensional perovskites as an exciting class of optoelectronic materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

RedOx-controlled sorption of iodine anions by hydrotalcite composites

The radioactive contaminant iodine-129 (I-129) is one of the top risk drivers at radiological waste disposal and contaminated groundwater sites where nuclear material fabrication or reprocessing has occurred. Currently there are very few options available to treat I-129 in the groundwater, which is partially related to its complex biogeochemical behavior in the subsurface and occurrence in the multiple chemical forms. We hypothesize that layered hydrotalcite materials containing redox active transition metal ions offer a potential solution, benefiting from the simultaneous adsorption of iodate (IO3-) and iodide (I-) anions, which exhibit different electronic and structural properties and therefore may require dissimilar hosts. To test this hypothesis, Cr3+- based materials were selected based on the rationale that Cr3+ readily reduces IO3- in solution. It was combined with either redox-active Co2+ or redox-inactive Ni2+ so that two model materials were prepared by hydrothermal synthesis including Co2+-Cr3+ and Ni2+-Cr3+(M-Cr). Obtained M-Cr materials comprised of Co2+-Cr3+ or Ni2+-Cr3+ layered hydrotalcite and small fractions of Co3O4 spinel or Ni(OH)2 theophrastite phases were structurally characterized before and after uptake of periodate (IO4-), IO3-, and I- anions. It was found that the IO3- uptake is driven by its chemical reduction to I2 and I-. Interestingly, in the Co2+-Cr3+ hydrotalcite, Co2+ and not Cr3+ serves as a reductant while in the Ni2+-Cr3+ hydrotalcite Cr3+ is responsible for the reduction of IO3-. A different uptake mechanism was identified for the IO4- anion. The Co2+-Cr3+ hydrotalcite phase efficiently uptakes IO4- by a diffusion-limited ion exchange mechanism and is not accompanied by the redox process, while Cr3+ in the Ni2+-Cr3+ hydrotalcite reduces IO4- to IO3-, I2 and I-. Iodide exhibited high affinity only to the Co-Cr material. The Co-Cr material performed remarkably well for the removal of IO3-, I- and total iodine from the groundwater collected from the US DOE Hanford site, WA, USA outperforming non-redox active hydrotalcites (e.g., Mg2+-Al3+) reported previously. This work demonstrates that redox-controlled sorption can be a highly effective method for the treatment of anions based on elements with mobile oxidation states. Further, multiple anions of interest could be simultaneously removed through combination of approaches.

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

Scaling arguments for a plasma experiment relevant to an interplanetary coronal mass ejection

We present the design of a plasma experiment scaled to be relevant to an interplanetary coronal mass ejection (ICME) traveling from the Sun to the Earth. The experiment would launch a compact torus of plasma (the scaled analog of the coronal mass ejected by the Sun) into a magnetized background plasma (the scaled analog of the interplanetary medium, the diffuse magnetized plasma that fills the Solar System). We present the complete process of scaling the ICME system to a laboratory experiment: beginning with the ICME features that we aim to replicate with a laboratory experiment, explaining how these desired features are translated into specific design constraints, and presenting a set of experimental parameters that meet those constraints. We find that the experiment would be possible with plasma conditions typically achieved in large-scale facilities such as the Big Red Ball at the University of Wisconsin or the LArge Plasma Device at the University of California, Los Angeles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Effect of diffusion constant on the morphology of dendrite growth in lithium metal batteries

Lithium dendrites can lead to a short circuit and battery failure, and developing strategies for their suppression is of considerable importance. In this work, we study the growth of dendrites in a simple model system where the solvent is a continuum and the lithium ions are hard spheres that can deposit by sticking to existing spheres or the electrode surface. Using stochastic dynamics simulations, we investigate the effect of applied voltage and diffusion constant on the growth of dendrites. We find that the diffusion constant is the most significant factor, and the inhomogeneity of the electric field does not play a significant role. Additionally, the growth is most pronounced when the applied voltage and diffusion constant are both low. We observe a structural change from broccoli to cauliflower shape as the diffusion constant is increased. The simulations suggest that a control of electrolyte parameters that impact lithium diffusion might be an attractive route to controlling dendrite growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

DYNAMICAL HEATING INDUCED BY DWARF PLANETS ON COLD KUIPER BELT–LIKE DEBRIS DISKS

With the use of long-term numerical simulations, we study the evolution and orbital behavior of cometary nuclei in cold Kuiper belt–like debris disks under the gravitational influence of dwarf planets (DPs); we carry out these simulations with and without the presence of a Neptune-like giant planet. This exploratory study shows that in the absence of a giant planet, 10 DPs are enough to induce strong radial and vertical heating on the orbits of belt particles. On the other hand, the presence of a giant planet close to the debris disk, acts as a stability agent reducing the radial and vertical heating. With enough DPs, even in the presence of a Neptune-like giant planet some radial heating remains; this heating grows steadily, re-filling resonances otherwise empty of cometary nuclei. Specifically for the solar system, this secular process seems to be able to provide material that, through resonant chaotic diffusion, increase the rate of new comets spiraling into the inner planetary system, but only if more than the ∼10 known DP sized objects exist in the trans-Neptunian region.

79 ASTRONOMY AND ASTROPHYSICS↗