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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Optimizing the Resolution of Hydrodynamic Simulations for MCRaT Radiative Transfer Calculations

Despite their discovery about half a century ago, the Gamma-ray burst (GRB) prompt emission mechanism is still not well understood. Theoretical modeling of the prompt emission has advanced considerably due to new computational tools and techniques. One such tool is the PLUTO hydro dynamics code, which is used to numerically simulate GRB outflows. PLUTO uses Adaptive Mesh Refinement to focus computational efforts on the portion of the grid that contains the simulated jet. Another tool is the Monte Carlo Radiation Transfer (MCRaT) code, which predicts electromagnetic signatures of GRBs by conducting photon scatterings within a jet using PLUTO. The effects of the underlying resolution of a PLUTO simulation with respect to MCRaT post-processing radiative transfer results have not yet been quantified. We analyze an analytic spherical outflow and a hydrodynamically simulated GRB jet with MCRaT at varying spatial and temporal resolutions and quantify how decreasing both resolutions affect the resulting mock observations. We find that changing the spatial resolution changes the hydrodynamic properties of the jet, which directly affect the MCRaT mock observable peak energies. We also find that decreasing the temporal resolution artificially decreases the high energy slope of the mock observed spectrum, which increases both the spectral peak energy and the luminosity. We show that the effects are additive when both spatial and temporal resolutions are modified. Our results allow us to understand how decreased hydrodynamic temporal and spatial resolutions affect the results of post-processing radiative transfer calculations, allowing for the optimization of hydrodynamic simulations for radiative transfer codes.

Jose Arita-Escalante↗
NASA NTRSDate not supplied

Additive Manufacture of Novel Tungsten Wicking and Heat Transfer Structures

Additive manufacturing (AM) is utilized for fabricating complex geometries from refractory metals, such as tungsten and molybdenum. In this study, plates with ultra-fine and fine lattice structures were manufactured from tungsten to demonstrate printability and the component fabrication advantages of AM. Previous work was completed on individual tungsten lattice structures; this work demonstrates the advantages of printing these structures on tubing and first-wall materials. Initial work using stainless steel demonstrated increased heat transfer properties promoted by these lattice structures. Applications for these structures include wicking structures, heat pipes, and first-wall materials in fusion devices. A major advantage of these designs is the capability to produce a monolithic component with tailored heat transfer and wicking properties. This research helps promote the ability to use liquid lithium in fusion devices since these lattice structures manufactured from tungsten could act as a high temperature first-wall or divertor material and as a wicking structure for liquid lithium. Different lattice structures with varying unit cell sizes and strut thicknesses were printed and the effects of these structures on heat transfer properties were measured. Abrasion resistance of these structures was also investigated. This presentation will discuss the results of these experiments and their implications related to heat transfer applications. This work will help inform the development and implementation of complex geometries made from tungsten for future heat pipe and fusion first-wall or divertor component designs.

Carly J. Romnes↗
NASA NTRSDate not supplied

Fast Radiative Transfer Model and Retrieval Algorithm Development for Satellite Remote Sensing Applications

The radiative transfer model (RTM) has a wide range of applications in satellite remote sensing and atmospheric radiation studies. For example, it can be used as a forward model for an inversion algorithm and a satellite data assimilation system, or as a L1 data simulator for pre-launch end-to-end satellite sensor performance studies. However, millions of line-by-line (LBL) radiative transfer calculations at fine monochromatic frequencies are needed in order to properly calculate spectral contributions of water vapor and trace gases in the atmosphere in infrared and solar spectral regions. Therefore, fast, and accurate radiative transfer models are needed. A Principal Component-based radiative transfer model (PCRTM) was developed at NASA Langley to fulfil this need. The PCRTM can simulate the top-of-atmosphere (TOA) radiance or reflectance spectra from 250 nm to 2000 micrometers with several orders of magnitude faster speed as compared to a LBL RTM. It is also extremely accurate compared to LBL RTM benchmarks. The PCRTM model has been developed for hyperspectral sensors such as AIRS, CrIS, IASI, NAST-I, SHIS, CPF, TEMPO, EMIT, OMI, and SCIAMACHY. By using the PCRTM as forward model for an inversion algorithm, one can reduce the data dimension significantly while maintaining original information content by compressing the TOA radiance spectrum into PC-scores. The PCRTM can directly compute the PC-scores and their derivatives with respect to retrieved parameters. Examples of using various PCRTM inversion algorithms to retrieve atmospheric temperature, water vapor, and trace gas profiles, as well as cloud and surface properties from satellite hyperspectral remote sensors will be given. Some of the algorithms have been transitioned to NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC) for public access of high-quality L2 and L3 data.

Xu Liu↗
NASA NTRSDate not supplied

An Eddy Current Case Study using NASA’s Transfer Function and Limited-Sample Probability of Detection Guidebooks

Probability of detection (POD) requirements for NASA fracture-critical human-rated systems can be met by (1) claiming ‘similarity’ to NASA Standard Nondestructive Evaluation (NDE) flaw sizes or (2) by inspector-specific POD demonstration, known as NASA Special NDE. Standard NDE flaw sizes are intended to represent the detection capability of most qualified inspectors, and were primarily based on POD studies in the development of the Space Shuttle Program Orbiter fracture control plan. However, these Standard NDE flaw sizes were based on fatigue cracks in flat panels of one material alloy over a limited range of panel thicknesses. While the POD study was comprehensive, the inspection conditions are relatively narrow. An evaluation of similarity between the Standard NDE POD study and flight component conditions is required to apply Standard NDE to specific flight component inspections. A similarity evaluation may include differences in materials, surface finish, component geometry (e.g., curvature, corners, welds), and inspection access. Similarity is typically based on a qualitative engineering evaluation. Recently, NASA published a quantitative methodology to assess similarity. If similarity is not supported by test and analysis, then the methodology provides a transfer function of flaw size for Special NDE POD demonstration. NASA recommends that Special POD demonstrations use flaws that are flight-like or more difficult to detect than flight component flaws, which are commonly induced fatigue cracks. Often, it is not feasible to induce fatigue cracks in flight component geometry, and therefore, a simpler representative geometry is used, commonly a flat panel, for POD demonstration. Inducing cracks in simple geometry specimens can be time-consuming and expensive, and thus, minimizing the number of flawed specimens is desired. Traditionally, NASA Special NDE demonstration was limited to MIL-HDBK-1823A methods or the binomial point-estimate method (PEM), commonly known as 29/29. Recently, NASA published a limited-sample POD (LS-POD) methodology for signal-response NDE techniques (e.g., eddy current) that provides POD demonstration with fewer specimens than previous approaches. LS-POD suggests a minimum of 10 flawed specimens, compared to 29 in the PEM and the suggested minimum of 40 from MIL-HDBK-1823A. The methodology also includes new guidance on evaluating the probability of false calls. In this presentation, these new transfer function and LS-POD methodologies are described and illustrated through an eddy current detection capability of far-side flaws on thin welded panels. A geometry-based transfer function is developed using electro-discharge machined (EDM) notches in flight component and simple geometry to estimate the Special NDE flaw size that is representative of the critical initial flaw size required by the fracture analysis. Then, fatigue cracks are induced in simple flat panels of the transferred flaw size, and the LS-POD methodology is used for Special NDE demonstration.

P. A. Parker↗
DOE OSTI2024

Microchannel Geometries for Improved Heat Transfer with Low-GWP refrigerants

Due to efforts aimed at decarbonizing industries, the use of refrigerants with low global warming potential (GWP) is highly recommended in the air-conditioning and refrigeration sectors. Despite possessing low-GWP values of less than 150, hydrofluoroolefins (HFO) exhibit relatively lower heat transfer performance compared to conventional hydrofluorocarbons (HFC) under certain operating conditions. In contrast to HFCs, there is a high demand for enhanced surfaces to meet the needs of heat transfer systems utilizing low GWP refrigerants. Accordingly, this study analyzes the pool boiling performance of low-GWP refrigerants in microchannel geometries. The experiments were carried out at various heat flux levels on both smooth and enhanced surfaces. The pool boiling behavior of low-GWP refrigerant R1234yf was compared to that of R-134a refrigerant in terms of heat transfer coefficient and wall superheat. The results indicate that the heat transfer coefficients of the enhanced surface are significantly higher than those of the smooth surface. Furthermore, the microchannel geometry demonstrated a lower wall superheat compared to the smooth surface. Additionally, a visualization study was performed using a high-speed camera to understand the pool boiling mechanism of low-GWP refrigerants on both smooth and enhanced surfaces.

Murugan, Muneeshwaran↗
DOE OSTI2024

Polyphase wireless power transfer systems, coil assemblies and resonant networks

Polyphase wireless power transfer systems are provided. The transfer system may be used for charging hybrid and electric vehicles. The systems are capable of transferring over 50 KW over an air gap of 15 cm. The systems use a rotating magnetic field to transfer power. The system may comprise transmitter coil assembly. The coil assembly may be one or more layers. The system may employ either unipolar or bipolar coils. The transmitter also comprises compensating capacitance connected in series with at least one coil for each phase. A value of the compensating capacitance for each phase is determined such that the transmitter has at least two independently excitable resonant modes at a resonant frequency. The transmitter is compatible with a plurality of different receivers including three-phase, single phase with a circular coil and single phase with DD coils.

Pries, Jason L.↗
DOE OSTI2026

Plasmon-Induced Resonance Energy Transfer in Hybrid Nanomaterials

Plasmon-induced resonance energy transfer (PIRET) has emerged as a powerful mechanism for harnessing and redirecting plasmon energy before it dissipates into hot carriers or heat. By matching plasmon resonance frequencies with acceptor absorption bands, PIRET extends plasmon-driven processes beyond the charge transfer pathway, enabling selective energy flow into excitonic transitions. Here, this review highlights important progress in elucidating the fundamental plasmon decay processes and transitioning them into hybrid nanomaterials under PIRET. Employing specialized single-particle spectroscopic techniques based on scattering, extinction, and emission enables demonstration of PIRET in the face of competing mechanisms, such as interfacial charge transfer and thermalization. Finally, we complete this review by addressing strategies for active modulation of PIRET and present applications, ranging from plasmon photocatalysis to intracellular biochemical sensing.

Energy transfer↗
NASA NTRS1953

Forced-convection Heat-transfer Characteristics of Molten Sodium Hydroxide

The forced-convection heat-transfer characteristics of sodium hydroxide were experimentally investigated. The heat-transfer data for heating fall slightly above the McAdams correlation line, and the heat-transfer data for cooling are fairly well represented by the McAdams correlation line.

NUCLEAR-ENERGY SYSTEMS↗
DOE OSTI2024

Room-Temperature Formate Ester Transfer Hydrogenation Enables an Electrochemical/Thermal Organometallic Cascade for Methanol Synthesis from CO 2

The reduction of CO 2 to synthetic fuels is a valuable strategy for energy storage. However, the formation of energy-dense liquid fuels such as methanol remains rare, particularly under low-temperature and low-pressure conditions that can be coupled to renewable electricity sources via electrochemistry. Here, in this study, a multicatalyst system pairing an electrocatalyst with a thermal organometallic catalyst is introduced, which enables the reduction of CO 2 to methanol at ambient temperature and pressure. The cascade methanol synthesis proceeds via CO 2 reduction to formate by electrocatalyst [Cp*Ir(bpy)Cl] + (Cp*=pentamethylcyclopentadienyl, bpy=2,2'-bipyridine), Fischer esterification of formate to isopropyl formate catalyzed by trifluoromethanesulfonic acid (HOTf), and thermal transfer hydrogenation of isopropyl formate to methanol facilitated by the organometallic catalyst (H-PNP)Ir(H) 3 (H-PNP=HN(C 2 H 4 P i Pr 2 ) 2 ). The isopropanol solvent plays several crucial roles: activating formate ion as isopropyl formate, donating hydrogen for the reduction of formate ester to methanol via transfer hydrogenation, and lowering the barrier for transfer hydrogenation through hydrogen bonding interactions. In addition to reporting a method for room-temperature reduction of challenging ester substrates, this work provides a prototype for pairing electrochemical and thermal organometallic reactions that will guide the design and development of multicatalyst cascades.

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

Hydroxy-substituted electron deficient Pd porphyrin cofactors illuminate ultrafast proton transfer reactions

Coordinated electron and proton movement drive bioenergetic functions. Relative to electron transfer reactions, tracking proton transport over fast-to-ultrafast time scales is challenging. Optical resolution of proton transfer dynamics can take advantage of chromophoric photoacids that not only trigger proton migration upon photoexcitation, but produce distinct spectroscopic changes associated with protonation/deprotonation. Here, in this work, we report the design of a hydroxy-substituted electron deficient Pd porphyrin, PPd(C 6 F 5 ) 3 OH; upon photoexcitation, the acidity constant of this weak acid (pKa = 6.49) dramatically drops (pKa* = 0.97). Electronic excitation of PPd(C 6 F 5 ) 3 OH triggers an ultrafast proton transfer reaction (PPd(C 6 F 5 ) 3 OH +:B + hυ → 1[PPd(C 6 F 5 ) 3 OH]* +:B → 1 [PPd(C 6 F 5 ) 3 O]−* + HB + ; τ PT = 342 fs) to a H-bonded base (B) in solution. Both PPd(C 6 F 5 ) 3 OH and its conjugate anion PPd(C 6 F 5 ) 3 O − exhibit distinct vis-NIR spectral features for their respective ground and excited states. Because the electroni-cally excited triplet lifetimes of these species exceed tens of microseconds, the PPd(C 6 F 5 ) 3 OH photoacid defines an ideal cofactor to probe light-triggered proton release and track long-range proton migration in protein environments.

Palladium↗
DOE OSTI2026

Mechanistic mass transfer in hollow fiber membrane solvent extraction for bio-based isobutanol

Membrane solvent extraction (MSE) has emerged as a promising method for selectively recovering bioproducts from complex aqueous streams. Bio-isobutanol, a next-generation feedstock for biofuel, remains challenging to recover because of its low concentration and the presence of inhibitory substances. This study explores the potential of hollow fiber (HF) MSE for bio-isobutanol recovery and systematically examines the coupled effects of fiber packing, shell-side flow dynamics, and aqueous chemistry on performance. A resistance-in-series model is applied to understand mass transfer in the HF MSE modules, quantify local resistances, and validate overall performance. The results show that increasing the fiber packing provides a larger interfacial area but induces poor flow distribution and channeling, hindering effective isobutanol transport. Meanwhile, increasing the shell-side velocity improves isobutanol recovery due to reductions in the boundary layer thickness. The presence of salts, added to mimic fermentation broth, increases the partition coefficient through salting-out effects, further improving isobutanol flux. A modified correlation for the shell-side mass transfer coefficient (k s,ϕ+v ), integrating geometric and hydrodynamic effects, was developed and validated. The proposed model achieves highly predictive accuracy (r 2 = 0.9808) across a wide range of conditions, outperforming previous models. The findings provide mechanistic insight into the interaction of geometric packing, hydrodynamics, and chemistry in governing mass transfer in HF MSE. Overall, this work demonstrates the potential of HF MSE for efficient bio-isobutanol recovery and also provides practical guidelines on critical factors (packing fraction, partition coefficient, and shell-side velocity), aiding in the design and scaling of MSE systems for resource recovery.

Aqueous chemistry↗
DOE OSTI2026

Vibrational Spin-Orbit Coupling Contributions to Excited State Decay of Ligand-to-Ligand Charge Transfer States

Controlling excited state relaxation processes is important in a variety of photochemical and photophysical processes, including the generation of ground and excited state spin polarization for quantum information science applications. Here, we address how specific static distortions – based on vibrational spin-orbit active modes at C2v symmetry determined by group theory – in a series of low-symmetry ligand-to-ligand charge transfer complexes enable direct spin-orbit coupling contributions to T1 → S0 excited state decay. These results are used to address spin-vibronic coupling contributions to T1 → S0 decay in a high-symmetry (tBu2bpy)Pt(S,S) (tBu2bpy = 4,4’-di-tert-butyl-2,2’-bipyridine and S,S = benzene-1,2-dithiolate) ligand-to-ligand charge transfer complex with effective C2v symmetry, where T1 relaxation is both spin- and orbitally forbidden due to the direct spin-orbit coupling matrix element being zero by symmetry. Low-frequency vibrations that involve a pyridine-pyridine twisting motion within the bpy ligand generate large ∂/∂Qi values that will contribute significantly to T1 → S0 relaxation. The work advances ligand design strategies for the generation of tailored T1 → S0 relaxation rates, which can be utilized to optimize the generation of electron spin polarization in radical-elaborated ligand-to-ligand charge transfer complexes.

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

Atomic Energy Accuracy of Neural Network Potentials: Harnessing Pretraining and Transfer Learning

Machine learning-based interatomic potentials (MLIPs) have transformed the prediction of potential energy surfaces (PESs), achieving accuracy comparable to ab initio calculations. However, atomic energy predictions, often assumed to lack physical meaning, remain underexplored. In this study, we demonstrate that inaccuracies in atomic energy predictions reduce the robustness and transferability of Neural Network Potentials (NNPs) and atomic energy error can be masked in total energy predictions due to error cancellation. Here, we validate this finding using challenging configurations involving deformation and failure under tensile loading. By pretraining atomic energy predictions using empirical potentials and applying transfer learning with density functional theory (DFT) data, we achieve notable improvements in the accuracy of total energy, forces, and stress predictions. Furthermore, this approach enhances the robustness and transferability of NNPs, emphasizing the importance of atomic energy predictions in developing high-quality and reliable MLIPs.

Active Learning↗
DOE OSTI2024

Tunability and Long-Range Enhancement of Resonance Energy Transfer Facilitated by Plasmonic Nanorods

Resonance energy transfer (RET) between molecules or quantum dots is an important process in many energy-related applications. Different environmental structures have been studied and demonstrated to be able to enhance the RET rates between a nearby donor–acceptor pair. In particular, cylindrical silver nanorods and nanowires have shown an extraordinary ability to transfer energy along their longitudinal axes over large distances. However, the detailed mechanism of such transfer and the effects on the molecular RET process are as yet elusive. In this study, we use the recently developed computational tool based on the plasmon-coupled RET method to systematically study the effects of nanorods with different dimensions on the RET rates. We find that highly frequency-dependent coupling factor (CF) spectra, whose amplitudes determine RET rates, can be obtained due to the localized surface plasmon polariton modes of the rods with nanoscale dimensions. Simple phenomenological models can be derived for the wavelengths of CF peaks in relation to the length and width of the nanorods, providing easy tunability for enhancing the RET rate in specific wavelength ranges. When coupled to longer rods with mesoscale lengths, exponential decay of the CF over long donor–acceptor distances with a small decay constant is observed, leading to the possibility of long-range RET processes. Furthermore, drumhead resonance modes emerge on the flat ends of the rod when the rod’s diameter reaches 300 nm, resulting in extra enhancement to RET rate compared to certain thinner rods. Furthermore, these findings shed new light on the mechanism of plasmonic enhancement with silver nanorods and establish design principles for how to optimally utilize these structures to manipulate RET processes for various applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Interfacial Charge Transfer and Substrate-Dependent Oxidation States Drive SMSI Enhancements in Cobalt Oxide Films

Here, we investigated the mechanisms underlying strong metal-support interactions in CO oxidation using model systems where noble metal crystals support reducible, monolayer-thick CoO x films. The effect of the Co oxidation state, film thickness, and substrate identity were studied in varying reaction conditions using ambient pressure X-ray photoelectron spectroscopy. At low O 2 pressures, the same oxide phase forms on both Pt(111) and Au(111) surfaces. But when heated at higher O 2 pressures, the oxide phase depends on the substrate. We found that CoO x /Pt is more active for the CO oxidation reaction than CoO x /Au, even when both surfaces stabilize the same oxide phase. DFT calculations on these and related noble-metal-supported CoO x films reveal an SMSI-induced reactivity enhancement that strongly depends on the oxide film thickness and which is mediated by charge transfer between the metal and oxide. Charge transfer is also found to correlate with the reaction energy and activation barrier for CO oxidation. This effect was found to be greatest for oxide films on Pt, decreasing on other noble metal supports in the order Pt > Pd > Au > Ag, in agreement with the experiments. The role of charge transfer in the activation barriers and reaction energies provides insight into the nature of SMSI-induced catalytic activity, and suggests that the noble metal work function can serve as an indicator for the strength of SMSI effects.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Radiative Heat Transfer and 2D Transition Metal Dichalcogenide Materials

Here we study the radiative heat transfer power in the family of transition metal dichalcogenide monolayers in their H- and T-symmetries. For this purpose, the electronic and optical properties computed from first-principles are used in effective models to understand the emerging scaling laws for metals and semiconductors as well as specific material signatures as control knobs for radiative heat transfer. Our combined approach of analytical modeling with properties from ab initio simulations can be used for other materials families to build a materials database for radiative heat transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Modulating Hole Transfer from CdSe Quantum Dots by Manipulating the Surface Ligand Density

The structure and density of surface capping ligands in cadmium chalcogenide quantum dots (QDs) are important considerations for controlling the efficiency of charge separation via the transfer of electrons or holes to molecular acceptors. Here we show how the manipulation of the surface ligand density of oleic acid-capped cadmium selenide (CdSe) QDs impacts the efficiency of hole transfer (HT) to polyoxovanadate alkoxides. Meerwein’s salt is used as a ligand-stripping agent, providing opportunities to quantitatively manipulate the ligand density at the surface of the nanocrystal, as evidenced by 1 H NMR spectroscopy. Time-resolved photoluminescence and transient absorption spectroscopies reveal that the extent of HT is quantitatively related to increased surface accessibility. Collectively, these results show that the reduction of surface ligand density can be used to tune the extent of interactions of molecular acceptors with QDs, providing a route to control charge-transfer processes relevant to improving the efficiency of QDs as photosensitizers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Kinetic Analysis of Proton-Coupled Electron Transfer at an Electrode-Immobilized Complex

An alkyne-terminated cobalt complex, [Co(Cp)(dppe ≡H )(Cl)] + (Cp = cyclopentadienyl; dppe ≡H = 1,2-bis-(di-(4-ethynyl-phenyl)phosphino)ethane), (Co ≡H ) was immobilized onto a glassy carbon electrode using two attachment strategies: Cu(I) catalyzed azide–alkyne click chemistry and reductive electropolymerization. The modified electrodes prepared through reductive electropolymerization exhibit current densities and peak resolutions for the electrochemical reduction of the cobalt species, which are amenable to electroanalytical quantification of coupled chemical reactions. Through peak shift analysis of cyclic voltammograms recorded in the presence of 4-chloroanilinium tetrafluoroborate, we quantified the proton transfer rate constant for the stepwise proton-coupled electron transfer reaction that reduces the electrode-immobilized [Co(Cp)(dppe ≡H )(Cl)] + to [H–Co(Cp)(dppe ≡H )] + (k PT app = (9.3 ± 1.8) × 10 5 M –1 s –1 ). In conclusion, the extraction of kinetic parameters for an elementary proton-coupled electron transfer reaction of an electrode-immobilized complex represents the first experimental measurement of its type and lays crucial groundwork for kinetic analyses of hybrid catalyst–electrode architectures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗