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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Behavior of Long-Chain Hydrocarbons at High Pressures and Temperatures

Although long-chain aliphatic hydrocarbons are documented in meteorites, their origin is poorly understood. A key question is whether they are pristine or a byproduct of terrestrial alteration? Thus, to understand if these long-chain hydrocarbons are indigenous, it will be important to explore their thermodynamic and mechanical stability at conditions experienced by extraterrestrial objects during atmospheric entry and passage. Extreme pressures and temperatures experienced by meteorites are likely to alter the molecular organization of these long-chain hydrocarbons. These structural changes associated with extreme conditions are often documented via laboratory-based Raman spectroscopic measurements. So far, Raman spectroscopic measurements have investigated the effect of static compression on the aliphatic hydrocarbons. The effect of temperature on the structural changes remains poorly explored. To bridge this gap, in this study, we have explored the behavior of two aliphatic hydrocarbons at simultaneously high pressures and temperatures. We have used a resistively heated diamond anvil cell. On compression to moderate pressures, the appearance of new vibrational modes in the low-energy region confirms prior studies and is related to the bending of the linear chains. Upon heating to ~220 °C, we note that the new low-energy mode undergoes softening. The mode softening is likely due to the combination of unbending of the alkane chain and mode anharmonicity.

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

Explanation of the seasonal variation of cosmic multiple muon events observed with the NOvA Near Detector

The flux of cosmic ray muons at the Earth’s surface exhibits seasonal variations due to changes in the temperature of the atmosphere affecting the production and decay of mesons in the upper atmosphere. Using 1473 live days of data collected by the NuMI Off-axis 𝜈 𝑒 Appearance (NOvA) Near Detector during 2018–2022, we studied the seasonal pattern in the multiple-muon event rate. The data confirm an anticorrelation between the multiple-muon event rate and effective atmospheric temperature, consistent across all the years of data. Previous analyses from MINOS and NOvA saw a similar anticorrelation but did not include an explanation. We find that this anticorrelation is driven by altitude–geometry effects as the average muon production height changes with the season. This has been studied with a CORSIKA cosmic ray simulation package by varying atmospheric parameters, and provides an explanation to a longstanding discrepancy between the seasonal phases of single and multiple-muon events.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

SPRUCE Warming Promotes the Use of Organic Matter as an Electron Acceptor in a Peatland: Supporting Data

These data are provided in support of the publication: Warming Promotes the Use of Organic Matter as an Electron Acceptor in a Peatland (Rush et al., 2021). Rush et al. (2021) reported on the effect of temperature on microbial organic matter reduction at the SPRUCE study site and S1 bog. Specifically, electron shuttling capacity (ESC), CH4 production, CO2 production, and acetate concentration were measured to explore both direct and indirect (through changes in soil quality and water-table level) effects of warming on microbial activity. Samples were collected in the summer of 2016 and 2017 depending on the experiment. This dataset contains five files in comma separated (*.csv) format. The SPRUCE Experiment Site is located in a Picea mariana [black spruce] Sphagnum spp. bog forest in northern Minnesota, 40 km north of Grand Rapids, in the USDA Forest Service Marcell Experimental Forest (MEF). This ecosystem, which is located at the southern margin of the boreal forest, is considered especially vulnerable to climate change and anticipated to be near its tipping point.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Thermal conductivity tensor of γ and ε -hexanitrohexaazaisowurtzitane as a function of pressure and temperature

Using reverse non-equilibrium molecular dynamics simulations, we have determined the dependences on temperature and pressure of the thermal conductivity tensors for the monoclinic γ and ε polymorphs of hexanitrohexaazaisowurtzitane (HNIW or CL20). In this work, a recently developed non-reactive force field [X. Bidault and S. Chaudhuri, RSC Adv. 9, 39649–39661 (2019)], designed to study polymorphism and phase transitions in CL20, is employed. The effects of temperature and pressure are investigated between 200 and 500 K and up to 0.5 GPa for γ-CL20 and 2 GPa for ε-CL20. In order to obtain the full thermal conductivity tensor, $κ_{ij}$, for the monoclinic crystals, four distinct heat propagation directions are used. We find that $κ_{ij}$ for both polymorphs is more isotropic than for other energetic molecular crystals, including α- and γ-RDX, β-HMX, and PETN, with a maximum difference of 9.8% between orientations observed at 300 K and 0 GPa for γ-CL20 and a maximum difference of 4.8% for ε-CL20. The average thermal conductivity, $\bar{κ}$, of ε-CL20 is 6.4% larger than that of γ-CL20 at 300 K and 0 GPa. Analytic linear functions of the inverse temperature and the pressure are provided, which fit the data well and can be used to predict the thermal conductivity of both polymorphs for any orientation, pressure, and temperature in and around the fitting range. Our predictions agree reasonably well with the limited available experimental data, for which the polymorph type is unknown.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Stomatal closure as a driver of minimum leaf conductance declines at high temperature and vapor pressure deficit in Quercus

Abstract Rising global temperatures and vapor pressure deficits (VPDs) are increasing plant water demand and becoming major drivers of large-scale plant mortality. Controlling transient leaf water loss after stomatal closure (minimum stomatal conductance [gmin]) is recognized as a key trait determining how long plants survive during soil drought. Yet, substantial uncertainty remains regarding how gmin responds to elevated temperatures and VPD and the underlying mechanisms. We measured gmin in 24 Quercus species from temperate and Mediterranean climates to determine whether gmin was sensitive to a coupled temperature and VPD increase. We also explored mechanistic links to phenology, climate, evolutionary history, and leaf anatomy. We found that gmin in all species exhibited a nonlinear negative temperature and VPD dependence. At 25 °C (VPD = 2.2 kPa), gmin varied from 1.19 to 8.09 mmol m−2 s−1 across species but converged to 0.57 ± 0.06 mmol m−2 s−1 at 45 °C (VPD = 6.6 kPa). In a subset of species, the effect of temperature and VPD on gmin was reversible and linked to the degree of stomatal closure, which was greater at 45 °C than at 25 °C. Our results show that gmin is dependent on temperature and VPD, is highly conserved in Quercus species, and is linked to leaf anatomy and stomatal behavior.

Zailaa, Joseph (ORCID:000000019103190X)↗
DOE OSTI2022

Analytical benchmark solution for 1-D neutron transport coupled with thermal conduction and material expansion

In this work we present fully analytical solutions for a class of finite, homogeneous, 1-D slab benchmark problems with nonlinear temperature feedback effects. The proposed class of benchmarks include multiplicative 1-D neutron transport (limited to quasistatic S{sub 2} with μ = ±1) coupled with thermal conduction, convection, Doppler broadening, and expansion effects along the length of the slab. This class of benchmark models, along with the corresponding analytical solutions, are valuable for validating multiphysics analysis frameworks that support coupled neutronics/thermal/structural calculations. Analytical solutions for the benchmarks are obtained by introducing an ansatz that the equilibrium flux and temperature distributions in the slab have the same shape. Specific values for the total microscopic cross section, σ{sub t,0}, and conductive heat transfer coefficient, h, that satisfy the assumed ansatz are then determined. A discussion of the procedure for generating benchmark models and analytical solutions is provided, along with numerical results for an example set of model parameters and thoughts on practical applications of the benchmarks for multiphysics code validation. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Enhanced diffusion bonding of alloy 617 using electric field-assisted sintering

The development of compact heat exchangers (CHXs) has gained increasing interest in many industries owing to their high thermal efficiency and reduced size. Diffusion bonding (DB) is an advantageous technique for fabricating CHXs. Alloy 617 is a candidate for manufacturing CHXs for high-temperature advanced nuclear reactors due to its elevated-temperature properties. Previous endeavors in DB of Alloy 617 were conducted by hot pressing (HP), which reported precipitates at the diffusion-bond interface, limited grain boundary (GB) migration, and significantly reduced high-temperature mechanical properties. To overcome these challenges, this study investigated DB of Alloy 617 using electric field-assisted sintering (EFAS). Stacks composed of three sheets were bonded with EFAS using different temperatures, pressures, and hold times. DB using HP as the zero-current analog of EFAS was also performed for comparison. The result shows that Cr- and Mo-rich precipitates were formed at the interface of the hot-pressed samples. The electric current and temperature in EFAS play a significant role in precipitation and GB migration. The electric current coupled with correct temperatures can effectively prevent precipitate formation at the interface and achieve excellent GB migration. Nanoscale Al-rich oxide was formed at the interface of the samples made by both HP and EFAS, but grain boundaries can ignore the nanoscale Al-oxide and migrate across the interface. The temperature, pressure, and hold time also affected diffusion. The temperature is a prerequisite for a successful GB migration, and GB migration can be enhanced by increasing pressure and hold time.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Intrinsic Junction Thermocouples For Surface Temperature Measurement

The material selection, attachment, and calibration of intrinsic junction thermocouples is discussed. Intrinsic junction thermocouples are utilized for their fast response times in surface measurements during high thermal transients. The as-is measurement and calibrated corrections are presented for both the out-of-pile pulse power system and the critical heat flux experiments in the Idaho National Laboratory Transient Reactor Test facility. The fin effect from temperature measurements on the surface of fuel cladding is corrected using a linear coefficient, m, and temperature corrections are sometimes 100 °C or more—representing 18% of the original temperature measurement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Tensile behavior and microstructural evolution of a Fe-25Ni-20Cr austenitic stainless steel (alloy 709) from room to elevated temperatures through in-situ synchrotron X-ray diffraction characterization and transmission electron microscopy

Uniaxial tensile tests were done on Fe-25Ni-20Cr Austenitic Stainless Steel (Alloy 709) along with in-situ synchrotron measurement at different temperatures (25 degrees C, 500 degrees C, 700 degrees C and 900 degrees C). The X-Ray diffraction data was collected in-situ in order to follow the phases present as well as to derive the dislocation density as a function of strain through peak broadening analysis based on the modified Williamson-Hall method and see how trends are affected as a function of temperature. The XRD data were complemented by TEM and STEM-EDX characterization done on the post-experiment samples to observe the deformed microstructures. Finally, the paper presents a depiction of the tensile behavior of this advanced steel by interpreting the stress-strain curves and the effect of temperature through the information gained by in-situ XRD and TEM observations as well as fractography done ex-situ on the samples tested to rupture.

36 MATERIALS SCIENCE↗
DOE OSTI2021

All-Atom Molecular Dynamics Simulations of the Temperature Response of Densely Grafted Polyelectrolyte Brushes

Water acts a “good” solvent for most polyelectrolyte (PE) systems due to its high dielectric strength. Theoretical and experimental studies have highlighted some remarkably unconventional properties of strongly water-swollen PE brushes such as a reduction in brush height with increase in temperature. However, an understanding of the atomistic-scale response of the grafted PE chains as well as the local arrangement and organization of the brush-supported counterions and water molecules to changes in temperature is missing. Here, we conduct an all-atom molecular dynamics (MD) study to probe the influence of temperature on the “microstructure” of densely grafted, fully ionized polyacrylic acid (PAA) brushes. The atomistic insights obtained from our study shed light on prior experimental observations and elucidate the key role played by changes in hydrogen bonding network in dictating the hydrophilicity of the brushes. In addition to the temperature-mediated reduction in height of the PE brush layer, we study the influence of temperature on several properties of the brush-supported water molecules such as the number distribution and kinetics of water-water and water-PE hydrogen bonds (HBs), mass density, orientational tetrahedral order parameter, and the activation energy associated with the self-diffusion of water. The effect of temperature on the properties of the brush-trapped counterions is also quantified via changes in their solvation structure, counterion-water radial distribution function (RDF), and the translational mobility. Our findings unravel several hitherto unknown phenomena such as the enhanced propensity for attaining PE brush-induced “water-in-salt”-like scenarios at elevated temperatures, and an increase in the activation energy for the self-diffusion of water with increase in the degree of PE brush-induced nanoconfinement (from ‘bulk water’ to ‘sparsely grafted PE brushes’ to ‘densely grafted PE brushes’). Further, we anticipate that this work will be helpful in improving our predictive capabilities of the temperature response of water-swollen PE brushes, which would be instrumental for better design of several PE brush systems used in a multitude of applications.

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

Effect of H 2 O on the ethylene glycol/alkali dismantling of bagasse for high-value conversion

Using a high-boiling alcohol system to dismantle main components of biomass is a feasible technology. Reducing dismantle operating costs and improving dismantle efficiency are essential for promoting the green, economical, and sustainable development of biomass refining. Therefore, based on the low cost and chemical properties of H 2 O at high temperature, the effects of different H 2 O dosages in NaOH-catalyzed ethylene glycol (HBAA) system on the dismantling efficiency of bagasse, surface lignin coverage, recovered-lignin activity and enzymatic hydrolysis efficiency were investigated. Compared with the HBAA dismantling system without H 2 O, the HBAA system with 60% w/v H 2 O can obviously increase the removal rates of lignin and hemicellulose, while recovering up to 99% of cellulose and significantly declining surface lignin coverage, thus enhancing the enzymatic hydrolysis efficiency. Additionally, the results of density functional theory calculations and 2D HSQC NMR analysis prove that the synergy between H 2 O and ethylene glycol can promote the esterification reaction occurrence at the α-C carbon cation in β-O-4 structure of lignin, thereby protecting the β-O-4 aromatic ether bond. Simultaneously, when the H 2 O dosage increase from 0% to 60%, the enzymatic yield increases from 84.51% to 93.74% with an enzyme load of 10 FPU/g. Based on experimental results, this study conducted a techno-economic analysis of bagasse dismantling for ethanol and co-production of lignin, achieving a minimum ethanol selling price of $\$$1.07 per kg. Here, in this study, a green and economical solution for dismantling the main components of bagasse is developed, which is important for the high-value conversion of bagasse.

Ethylene glycol↗
DOE OSTI2025

Effects of Landau quantization on neutrino emission and absorption

Some neutron stars known as magnetars possess very strong magnetic fields, with surface fields as large as 10 15 G and internal fields that are possibly stronger. Recent observations of the radio pulsar GLEAM-X J1627 suggest it may have a surface field as strong as 10 16 G. In the presence of a strong magnetic field, Leinson and Perez showed and Baiko and Yakovlev confirmed that the energy levels of electrons and protons are quantized and the direct Urca process allows neutron stars to cool rapidly, even at low density. For the case of magnetic fields 𝐵 ≳ 10 16 G, we find features in the emissivity due to energy quantization that are not captured by the frequently employed quasiclassical approximation where energy levels are treated as nearly continuous. Resonances can result in amplification of the neutrino emissivity at specific densities compared to a calculation that neglects quantization, particularly at low temperature. These effects are not important for the thermal evolution of an entire neutron star, but may be relevant for phenomena that depend on behavior at specific densities. Here, we present a fully relativistic calculation of the direct Urca rate in a strong magnetic field using the standard V-A weak Lagrangian incorporating mean field nuclear effects and discuss approaches to the numerical challenge the modified wave functions present and a new semianalytic approximation. These tools are also applicable to calculating neutrino opacities in strong magnetic fields in the ejecta of binary neutron star mergers. We calculate the opacities for neutrinos capturing on free nucleons at subsaturation densities and temperatures exceeding an MeV. We find an enhancement to capture processes of the lowest energy neutrinos by an order of magnitude or more due to suppression of electron Pauli blocking in the case of capture on neutrons, and from the effect of the nucleon magnetic moments in the case of capture on protons.

astrophysical electromagnetic fields↗
DOE OSTI2021

Simultaneously Blocking Chemical Crosstalk and Internal Short Circuit via Gel-Stretching Derived Nanoporous Non-Shrinkage Separator for Safe Lithium-Ion Batteries

The separator, an ionic permeable and electronic insulating membrane between cathode and anode, plays a crucial role in the electrochemical and safety performance of batteries. However, the commercial polyolefin separators not only suffer from inevitable thermal shrinkage at elevated temperature, but also fail to inhibit the hidden chemical crosstalk of reactive gases such as O 2 , leading to often reported thermal runaway (TR) and hence preventing large-scale implementation of high-energy-density lithium-ion batteries. Herein, a nanoporous non-shrinkage separator (GS-PI) was fabricated via a novel gel-stretching orientation approach to eliminate TR. In situ synchrotron small angle X-ray scattering during heating clearly showed that the as-prepared thin GS-PI separator exhibits superior mechanical tolerance at high temperature, thus effectively preventing internal short circuit. Meanwhile, the unique nanoporous structure design further blocks chemical crosstalk and the associated exothermic reactions. Accelerating Rate Calorimetry test revealed that the practical 1 Ah LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622)/graphite pouch cell using GS-PI nanoporous separator show a maximum temperature rise (dT/dt max ) of only 3.7 °C s -1 compared to 131.6 °C s -1 in the case of Al 2 O 3 @PE macroporous separator. Furthermore, despite the reduced pore size, the GS-PI separator demonstrates better cycling stability than conventional Al 2 O 3 @PE separator at high temperature without sacrificing specific capacity and rate capability.

25 ENERGY STORAGE↗
DOE OSTI2022

Temperature screening and cross-field impurity accumulation from a thermodynamic perspective

In a variety of different systems, high-Z ion species show a marked tendency to accumulate in regions of high plasma density. It has previously been suggested that the apparent universality of this behavior could be explained thermodynamically, in terms of the maximum-entropy state attainable when the system must obey an ambipolarity condition. Furthermore, the previous treatment did not allow for the possibility of temperature gradients. Here, tools from non-equilibrium (Onsager) thermodynamics are used to show that ambipolarity continues to play a key role in producing this behavior in the presence of temperature gradients, and to recover well-known temperature screening effects that appear in these cases.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Growth and Saturation of the Electron Drift Instability in a Crossed Field Plasma

The linear growth and nonlinear energy transfer of the electron drift instability (EDI) are experimentally measured in the plume of a low-temperature, Hall effect discharge. A frequency-based bispectral analysis technique applied to fast ion density fluctuation measurements shows a growth rate function that is qualitatively similar to predictions from the linear instability dispersion relation, but an order of magnitude smaller. Calculation of the nonlinear transfer function indicates multiple three-wave interactions between high-frequency resonances of the instability in addition to an inverse energy cascade toward lower-frequency modes. Furthermore, these results are discussed in the context of recent theoretical, numerical, and experimental efforts on the EDI in Hall effect discharges and how the EDI may impact anomalous cross field transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Irreparable Interphase Chemistry Degradation Induced by Temperature Pulse in Lithium‐Ion Batteries

Abstract While it is widely recognized that the operating temperature significantly affects the energy density and cycle life of lithium‐ion batteries, the consequence of electrode‐electrolyte interphase chemistry to sudden environmental temperature changes remains inadequately understood. Here, we systematically investigate the effects of a temperature pulse (T pulse) on the electrochemical performance of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) pouch full cells. By utilizing advanced characterization tools, such as time‐of‐flight secondary‐ion mass spectrometry, we reveal that the T pulse can lead to an irreversible degradation of cathode‐electrolyte interphase chemistry and architecture. Despite negligible immediate impacts on the solid‐electrolyte interphase (SEI) on graphite anode, aggregated cathode‐to‐anode chemical crossover gradually degrades the SEI by catalyzing electrolyte reduction decomposition and inducing metallic dead Li formation because of insufficient cathode passivation after the T pulse. Consequently, pouch cells subjected to the T pulse show an inferior cycle stability to those free of the T pulse. This work unveils the effects of sudden temperature changes on the interphase chemistry and cell performance, emphasizing the importance of a proper temperature management in assessing performance.

Cui, Zehao↗
DOE OSTI2025

Anharmonic phonons, thermal expansion, and nuclear quantum effects in Zn

The anharmonic behavior of phonons and thermal expansion of hexagonal zinc were studied from 15 to 690 K by inelastic neutron scattering (INS) and ab initio simulations. Phonon spectra were measured for Q-points covering the full Brillouin zone, giving the phonon density of states (DOS) and dispersions along high-symmetry directions. The dispersions were sharp at 15 K, but diffuse intensity was observed at energies above them. The dispersions broadened with temperature T and the diffuse intensity became stronger. This diffuse intensity appeared in all INS measurements and simulations, except for classical molecular dynamics at 15 K. The temperature-dependent effective potential (TDEP) method, which included the nuclear quantum effect from zero-point vibrational dynamics, was used to calculate the free energy and thermal expansion. For T < 100 K nuclear quantum effects were important for obtaining the correct negative thermal expansion, and path integral molecular dynamics (PIMD) was particularly effective for obtaining the negative thermal expansion in the basal plane. A Heisenberg-Langevin model for interacting phonons coupled to a thermal bath was able to reproduce the shape and intensity of the diffuse spectral features.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Accurate Fe–He machine learning potential for studying He effects in BCC-Fe

Nanostructured Ferritic Alloys (NFAs) containing oxide nanoparticles are prospective advanced structural materials in future fusion reactors. Lacking fusion neutron sources with an adequate flux, modeling is critical to understand radiation damage in the NFAs, including helium effects. Machine learning interatomic potentials (MLPs) have been demonstrated to be capable of describing atomic interactions in chemically complex systems with comparable accuracy to density functional theory (DFT) but with much less computational costs. Hence, MLPs are chosen to study He bubble accumulation in chemically complex NFAs. As a preliminary step, we develop a Fe–He potential, based on ~10,000 atomic configurations. The developed MLP accurately predicts the bulk properties of BCC-Fe compared to DFT, including the lattice constant (2.832 Å), elastic constants (c 11 = 271 GPa, c 12 = 141, c 44 = 93), and phonon frequencies (maximum error < 3.5%). The MLP predicts He binding energies in He n V bubbles and He n clusters with a mean absolute error (MAE) of only ~70 meV, which is ~3 to ~5 times smaller than the MAE of binding energies estimated using empirical potentials. The MLP also accurately predicts the migration barrier of interstitial He (64 meV). Furthermore, the MLP correctly predicts the maximum number of He atoms (critical size) at which a He n V bubble (He n cluster) can kick-out a self-interstitial atom (SIA), forming a bigger He n V 2 bubble (He n V bubble). Subsequently, we use the MLP to perform molecular dynamics simulations to investigate the effect of temperature on the critical size of He n V bubbles and He n clusters. We find that the critical size decreases with increasing temperature — indicating that smaller bubbles and clusters can kick-out an SIA at higher temperatures, thereby escalating the He bubble growth. We report the current Fe–He MLP can be further developed to include all chemical interactions in NFAs.

36 MATERIALS SCIENCE↗