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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Formation and Evolution Simulations of Saturn, Including Composition Gradients and Helium Immiscibility

In this paper, the formation of Saturn is modeled by detailed numerical simulations according to the core-nucleated accretion scenario. Previous models are enhanced to include the dissolution of accreting planetesimals, composed of water ice, rock, and iron, in the gaseous envelope of the planet, leading to a nonuniform composition with depth. The immiscibility of helium in metallic hydrogen layers is also considered. The calculations start at a mass of 0.5 Earth masses and are extended to the present day. At 4.57 Gyr, the model, proceeding outward, has the following structure: (i) a central core composed of 100% heavy elements and molecules, (ii) a region with a decreasing heavy-element mass fraction, down to a value of 0.1, (iii) a layer of uniform composition with the helium mass fraction Y enhanced over the primordial value, (iv) a helium rain region with a gradient in Y, (v) an outer convective, adiabatic region with uniform composition in which Y is reduced from the primordial value, and (vi) the very outer layers where cloud condensation of the heavy elements occurs. Models of the distribution of heavy elements as a function of radius are compared with those derived to fit the observations of the Cassini mission, with rough qualitative agreement. The helium mass fraction in Saturn’s outer layers is estimated to be around 20%. Models are found that provide good agreement with Saturn’s intrinsic luminosity and radius.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

An integrated process for butanol production from cellulosic biomass and CO 2 using engineered clostridia in a linear immobilized bioreactor

Engineered platforms using mixed microbial consortia to consolidate multiple reaction steps and perform disparate conversions simultaneously can substantially enhance the carbon efficiency of biomass conversion processes and lower the biofuel cost to an economically competitive level. In this project, an integrated process will be developed to produce n-butanol from cellulosic biomass and waste gas streams using two engineered clostridial strains, one butanol-tolerant solventogenic strain and one carboxydotrophic acetogen, co-immobilized in a “Linear Immobilized Bioreactor” (LIBR). The CO 2 and H 2 produced by the solventogenic strain will be used by the carboxydotrophic strain to produce acetate (and butyrate) that in turns can be used by the solventogenic strain to produce more butanol. Such a co-cultured fermentation has the potential to increase butanol production from biomass hydrolysate sugars by up to 50% with 100% reduction in CO 2 emission. Butanol produced in the fermentation will be stripped by the rising bubbles of fermentation produced gases (CO 2 and H 2 ) in the LIBR and separated via a condenser, alleviating butanol inhibition while achieving continuous butanol production at a high productivity and product titer, which can reduce both water and energy consumptions by over 50% compared to conventional ethanol and ABE fermentation processes. Phase I study proved the new bioprocess concept and verified our hypothesis that the proposed LIBR and co-cultured fermentation can enhance the conversion of lignocellulosic sugars to butanol with higher butanol yield, productivity and titer, leading to reduced biobutanol cost to compete more favorably with bioethanol and fossil fuels. A prototype lab-scale LIBR for multiphase fermentation was constructed to investigate and demonstrate the technical feasibility and advantages of the LIBR for multiphase fermentation involving sugars and gaseous substrates. The LIBR will be optimized and evaluated for its economic feasibility for biobutanol production from lignocellulosic biomass and industrial waste gases in Phase II.

09 BIOMASS FUELS↗
DOE OSTI2020

Hydrazone-Linked Heptazine Polymeric Carbon Nitrides for Synergistic Visible-Light-Driven Catalysis

Heptazine-based conjugated polymeric carbon nitrides (PCNs) are promising metal-free photocatalysts, yet their synthesis is challenging due to the electron-deficiency and insolubility of heptazine units. Indeed, heptazine-containing polymers have only been prepared through nucleophilic substitution with amines by using toxic cyameluric chloride as the starting material. Herein, we report the novel and environmentally friendly method for preparing heptazine-based mesoporous PCNs with hydrazone links formed through a simple Schiff base condensation of melem-NH 2 and aldehydes. Unlike cyameluric chloride, melem-NH 2 is non-toxic, stable, and can be readily obtained from melem and hydrazine in solution. We demonstrate that the hydrazone linkages and the heptazine units synergistically enhance the photocatalytic activity of PCNs in visible-light-driven aerobic oxidation of benzyl alcohol to benzaldehyde. In particular, the polymer constructed from melem-NH2 and p-phthalaldehyde shows 17 times more activity than graphitic carbon nitride (g-C 3 N 4 ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Rotating quantum turbulence in the unitary Fermi gas

Quantized vortices carry the angular momentum in rotating superfluids, and are key to the phenomenon of quantum turbulence. Advances in ultracold-atom technology enable quantum turbulence to be studied in regimes with both experimental and theoretical control, unlike the original contexts of superfluid helium experiments. While much work has been performed with bosonic systems, detailed studies of fermionic quantum turbulence are nascent, despite wide applicability to other contexts such as rotating neutron stars. In this paper, we present a large-scale study of quantum turbulence in rotating fermionic superfluids using an accurate time-dependent density functional theory called the superfluid local density approximation. We identify two different modes of turbulent decay in the dynamical equilibration of a rotating fermionic superfluid, and contrast these results with a computationally simpler description provided by the Gross-Pitaevskii equation, which we find can qualitatively reproduce these decay mechanisms if dissipation is explicitly included. These results demonstrate that dissipation mechanisms intrinsic to fermionic superfluids play a key role in differentiating fermionic from bosonic turbulence, which manifests by enhanced damping of Kelvin waves.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Numerical analysis of air dehumidification through electrospray-enhanced vortical flow cyclone separator

The dehumidification of air is a highly energy-intensive process, typically requiring vapor compression systems to cool the air significantly below its dew point temperature. Here, this study numerically investigates air dehumidification achieved by electrostatic and dielectrophoresis forces in a converging duct and centrifugal principles in cyclone separators. An electrospray was employed to energize water droplets, which then captured water vapor via dielectrophoresis. A novelty of the present study is the inclusion of a cyclone separator positioned downstream of the electrospray. This combination increased the dehumidification efficiency and controlled the flow of the condensate. By integrating electrospray technology and applying an electric field, this study examines the impact of particle separation efficiency, pressure drops, and cyclone performance on air dehumidification. The control parameters for air dehumidification were investigated. Three cyclones were modelled for airflow rates of 5 cubic feet per minute [cfm] (0.0024 m 3 /s), 38 cfm (0.0179 m 3 /s), and 200 cfm (0.094 m 3 /s). The results indicated air dehumidification was up to 5.7 % under environmental conditions, similar to those used to validate the CFD model. The degree of air dehumidification was primarily influenced by the electric charge acquired by the water droplets, their flight trajectory, and the vorticity intensity within the cyclone. Air dehumidification could increase by up to 13 % by increasing the number of droplets injected into the air stream, the flight time, and the electrical charge. The breakdown electric field strength threshold near the electrospray was a limiting factor for further enhancing dehumidification performance. This study examines the optimization of an electro-assisted dehumidification system that includes cyclone-based droplet separation through numerical analysis. The results provide insights into the design of energy-efficient air treatment technologies.

42 ENGINEERING↗
DOE OSTI2023

A novel mineral-acid free biphasic deep eutectic solvent/γ-valerolactone system for furfural production and boosting the enzymatic hydrolysis of lignocellulosic biomass

The failure of hemicellulose valorization in a deep eutectic solvent (DES) pretreatment has become a bottleneck that challenges its further development. Here, to address this issue, this study developed a DES/GVL (γ-valerolactone) biphasic system for effective hemicellulose-furfural conversion, enhanced cellulose saccharification and lignin isolation. The results indicated that the biphasic system could significantly improve the lignin removal (as high as 89.1%), 86.0% higher than the monophasic DES, accompanied by ~100% hemicellulose degradation. Notably, the GVL in the biphasic solvent restricted the condensation of hemicellulose degradation products, which as a result generated large amount of furfural in the pretreatment liquid with a yield of 68.6%. With the removal of hemicellulose and lignin, cellulose enzymatic hydrolysis yield was boosted and reached near 100%. This study highlighted that the novel DES/GVL is capable of fractionating the biomass and benefiting their individual utilization, which could provide a new biorefinery configuration for a DES pretreatment.

09 BIOMASS FUELS↗
DOE OSTI2023

Multiscale Imaging of Nuclear Deformation at the Electron-Ion Collider

We show within the Color Glass Condensate framework that exclusive vector meson production at high energy is sensitive to the geometric deformation of the target nucleus at multiple length scales. Studying e+U collisions and varying the deformation of the uranium target, we demonstrate that larger deformations result in enhanced incoherent vector meson production cross sections. Further, different multipole deformation parameters affect different regions of transverse momentum transfer. Employing JIMWLK evolution to study the Bjorken-x dependence of our results, we find that the ratio of incoherent to coherent cross sections decreases with decreasing x, largely independently of the quadrupole deformation of the target. Comparing results for the same process using 20 Ne targets with 16 O targets, we find that differences in deformation are clearly visible in the incoherent cross section. These findings show that certain observables at the Electron-Ion Collider are very sensitive to nuclear structure. Consequently, deformations need to be taken into account when interpreting experimental results. More importantly, this also means that |t|-differential diffractive vector meson production could become a powerful tool, enabling the most direct measurements of nuclear structure at different length scales, ranging from nuclear deformation at low |t| to nucleon and subnucleon-size scales at higher |t|.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO 2

We detail the estimation of activation energies and quantum nuclear vibrational tunneling effects for hydrogen diffusion in PuO 2 based on Density Functional Theory calculations and a quantum double well approximation. We find that results are relatively insensitive to choice of exchange correlation functional. In addition, the representation of spin in the system and use of an extended Hubbard U correction has only a small effect on hydrogen point defect formation energies when the PuO 2 lattice is held fixed at the experimental density. We then compute approximate activation energies for transitions between hydrogen interstitial sites seeded by a semi-empirical quantum model and determine the quantum tunneling enhancement relative to classical kinetic rates. Our model indicates that diffusion rates in H/PuO 2 systems could be enhanced by more than one order of magnitude at ambient conditions and that these effects persist at high temperature. The method we propose here can be used as a fast screening tool for assessing possible quantum nuclear vibrational effects in any number of condensed phase materials and surfaces, where hydrogen hopping tends to follow well defined minimum energy pathways.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effect of metamaterial engineering on the superconductive properties of ultrathin layers of NbTiN

The electronic transport and optical properties of high quality multilayers of NbTiN/AlN with ultrathin NbTiN layers were characterized. The anisotropy of the dielectric function of the multilayers confirmed their hyperbolic metamaterial properties. Here, the superconductive transition temperature, T c , of these engineered superconductors was enhanced up to 32% compared to the T c of a single ultrathin NbTiN layer while the resistivity per NbTiN layer remained unchanged. We have demonstrated that this T c increase can be attributed to enhanced electron–electron interaction in superconducting hyperbolic metamaterials. The measured critical fields are high and have an anomalous temperature dependence on the direction perpendicular to the magnetic field. These results demonstrate that the metamaterial engineering approach can be used to enhance H c2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Observation of Magnon Polarons in a Uniaxial Antiferromagnetic Insulator

Magnon polarons, a type of hybridized excitations between magnons and phonons, were first reported in yttrium iron garnet as anomalies in the spin Seebeck effect responses. Here, we report an observation of antiferromagnetic (AFM) magnon polarons in a uniaxial AFM insulator Cr 2 O 3 . Despite the relatively higher energy of magnon than that of the acoustic phonons, near the spin-flop transition of ~ 6 T , the left-handed magnon spectrum shifts downward to hybridize with the acoustic phonons to form AFM magnon polarons, which can also be probed by the spin Seebeck effect. The spin Seebeck signal is founded to be enhanced due to the magnon polarons at low temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Enhanced contribution of the pairing gap to the QCD equation of state at large isospin chemical potential

In this paper QCD at large isospin density is studied, which is known to be in the superfluid state with Cooper pairs carrying the same quantum number as pions. The gap equation derived from the perturbation theory up to the next-to-leading-order corrections is solved. The pairing gap at large isospin chemical potential is found to be enhanced compared to the color-superconducting gap at large baryon chemical potential due to the 2 difference in the exponent arising from the stronger attraction in one-gluon exchange in the singlet channel. Then, using the gap function, the contribution of the condensation energy of the superfluid state to the QCD equation of state is evaluated. At isospin chemical potential of a few GeV, where the lattice QCD and the perturbative QCD can be both applied, the effect of the condensation energy becomes dominant even compared to the next-to-leading order corrections to the pressure in the perturbation theory. It resolves the discrepancy between the recent lattice QCD results and the perturbative QCD result. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2023

Enhancing photonic systems using topology and non-Hermiticity

The broad goal of this project was to develop new analytical and numerical insights for how important photonic processes can be improved using recently discovered principles in topological and non-Hermitian physics. In particular, there are two recent discoveries that we aimed to harness to achieve this goal. First, it was discovered in condensed matter physics that crystalline symmetries can protect low-dimensional topologically protected states in lattices without the need for breaking time-reversal symmetry. These so-called ‘higher-order’ topological systems represent an important development for photonic systems, where it is very difficult to break time-reversal symmetry, and which had been previously thought necessary to realize topological phenomena. Second, the last decade has seen a significant amount of interest in phenomena which are unique to non-Hermitian systems, i.e., systems which do not conserve energy. For example, spatially patterned gain and loss can be used to realize exceptional points, which are degeneracies in a system’s spectrum where the system becomes defective, while the existence of radiative losses also enables a new route to confinement through bound states in the continuum. For such non-Hermitian phenomena, photonics again represents a critical platform, as photonic systems naturally lose light to their radiative environments, making them generally non-Hermitian, and it is also possible to incorporate additional gain or loss. Based on these broad principles, we pursued a range of projects to harness bound states in the continuum in a variety of different systems and architectures, develop real-space methods for classifying topological systems to yield better photonic design principles, and a novel Brillouin-based fiber laser for sensing strain.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Loop Thermosyphon Enhanced Solar Collector

A two-phase loop thermosyphon solar collector was developed to transfer thermal energy efficiently and passively from a concentrated solar collector to a thermal desalination process. The two-phase flow in the loop thermosyphon is driven by a difference in gravitational pressure head between the liquid return line and the two-phase riser located between the evaporator and condenser. A numerical model incorporating mass, energy, and pressure drop balances was developed to predict system performance and use as a design tool. Three iterations of loop thermosyphon solar collectors were designed, fabricated, and tested to validate the numerical analysis and demonstrate system integration. Additionally, a novel solar receiver design was evaluated based on volumetric absorption of the concentrated sunlight by an optically absorptive two-phase working fluid. Life tests were performed to evaluate the working fluid thermal stability and resistance to ultraviolet degradation. A glass receiver tube and associated glass-to-metal junctions were developed. Finally, a full-scale loop thermosyphon was integrated with a parabolic trough solar collector and tested on-sun.

14 SOLAR ENERGY↗
DOE OSTI2026

Disentangling High Harmonic Generation from Surface and Bulk States of a Topological Insulator

The discovery of topological phases has introduced a new dimension to materials science. Three-dimensional (3D) topological insulators (TIs) are a remarkable class of matter that is insulating in the bulk while hosting conductive topological surface states (TSSs) with unique charge and spin properties. High-order harmonic generation (HHG) has emerged as a powerful tool to probe condensed matter systems by providing insights into their electronic structure and dynamic behavior. Here, we investigate HHG in the prototype 3D-TI Bi$_2$Se$_3$. We demonstrate that the contributions of bulk and surface states to the harmonic emission can be controlled by tuning the thickness of thin film samples. An ultrathin (6 nm) film substantially enhances HHG from the surface states, while the bulk states dominate HHG in a thicker (50 nm) film. By applying a quasi-static terahertz perturbing field, we disentangle the bulk and surface responses and reveal the significant impact of the surface states' shift vector and Berry curvature on HHG. Our study provides effective methods for isolating the optical responses of TSSs from those of the bulk, which opens the door to resolving an ongoing debate regarding whether it is possible to reliably extract topological signatures in HHG.

Atomic Physics (physics.atom-ph)↗
DOE OSTI2021

ATP Drives Efficient Terpene Biosynthesis in Marine Thraustochytrids

Understanding carbon flux controlling mechanisms in a tangled metabolic network is an essential question of cell metabolism. Secondary metabolism, such as terpene biosynthesis, has evolved with low carbon flux due to inherent pathway constraints. Thraustochytrids are a group of heterotrophic marine unicellular protists and can accumulate terpenoids under the high-salt conditions in their natural environment. However, the mechanism behind terpene accumulation is not well understood. Here, we show that terpene biosynthesis in Thraustochytrium sp. ATCC 26185 is constrained by local thermodynamics in the mevalonate pathway. Thermodynamic analysis reveals metabolite limitation in the nondecarboxylative Claisen condensation of acetyl-coenzyme A (CoA) to the acetoacetyl-CoA step, catalyzed by the acetyl-CoA acetyltransferase (ACAT). Through a sodium-elicited mechanism, higher respiration leads to increased ATP investment into the mevalonate pathway, providing a strong thermodynamic driving force for enhanced terpene biosynthesis. Proteomic and metabolomic analyses further show that the increased ATP demands are fulfilled by shifting energy generation from carbohydrate to lipid oxidation. This study demonstrates a unique strategy in nature that uses ATP to drive a low-flux metabolic pathway, providing an alternative solution for efficient terpene metabolic engineering.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Robust d-Wave Superconductivity in the Square-Lattice t–J Model

Unravelling competing orders emergent in doped Mott insulators and their interplay with unconventional superconductivity is one of the major challenges in condensed matter physics. Here, to explore the possible superconducting state in a doped Mott insulator, we study the square-lattice t-J model with both the nearest-neighbor and next-nearest-neighbor electron hoppings and spin interactions. By using the state-of-the-art density matrix renormalization group calculation with imposing charge U(1) and spin SU(2) symmetries on the six-leg cylinders, we establish a quantum phase diagram including three phases: a stripe charge density wave phase, a superconducting phase without static charge order, and a superconducting phase coexistent with a weak charge stripe order. Crucially, we demonstrate that the superconducting phase has a power-law pairing correlation that decays much slower than the charge density and spin correlations, which is a quasi-1D descendant of the uniform d-wave superconductor in two dimensions. These findings reveal that enhanced charge and spin fluctuations with optimal doping is able to produce robust d-wave superconductivity in doped Mott insulators, providing a foundation for connecting theories of superconductivity to models of strongly correlated systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

From Electronic Structure to Ion Transport: Photoelectron Spectroscopy and Molecular Dynamics Simulations Reveal the Role of Anions in Lithium Battery Electrolytes

Electrolyte anions are pivotal for lithium battery performance, yet their fundamental electronic structural properties are not well understood. In this work, we employ a combination of negative-ion photoelectron spectroscopy (NIPES), ab initio calculations, and molecular dynamics (MD) simulations to investigate the electronic structures of three representative electrolyte anions. This multiscale approach enables us to elucidate how their intrinsic electronic properties govern anion–solvent interactions in gas-phase clusters, as well as lithium-ion (Li + ) solvation structures and ion transport behavior in the condensed phase. NIPES reveals that difluoro(oxalato)borate (DFOB – ), bis(fluorosulfonyl)imide (FSI – ), and bis(oxalato)borate (BOB – ) all exhibit high electron binding energies, with vertical/adiabatic detachment energies increasing from DFOB – (6.09/5.70 eV) to FSI – (6.80/6.10 eV) to BOB – (6.82/6.40 eV), correlating with enhanced oxidation stability. Ab initio calculations reveal that DFOB – /FSI – –solvent complexes bind Li + ∼ 10 kcal/mol stronger than BOB – series, aligning with the strength of a Li + –anion model. DFOB – exhibits pronounced charge localization on both oxygen and fluorine atoms, enabling their involvement in Li + coordination. In contrast, fluorine atoms in FSI – are largely electron-depleted and remain excluded from direct Li + binding. MD simulations further demonstrate that LiDFOB and LiFSI systems exhibit Li + diffusion coefficients three and five times higher than those of LiBOB across four common solvents. Notably, LiFSI salt in acetonitrile (AN) exhibits the fastest Li + diffusion among 12 electrolyte systems, highlighting the synergistic effect of FSI – and AN in promoting ion mobility. In conclusion, these findings provide a molecular-level understanding of the critical roles of anion and its microsolvation in optimizing Li + diffusion dynamics, once again emphasizing the positioning of FSI – and DFOB – as prime candidates for next-generation electrolytes.

25 ENERGY STORAGE↗