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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

A CFD Study Assisted with Experimental Confirmation for Liquid Shape Control of Electromagnetically Levitated Bulk Materials

Two types of optimized electromagnetic levitators were designed to achieve the free surface shape control of metallic melts as the combined results of the Lorentz force, sample gravity, and surface tension. The levitation behavior of bulk melts was investigated using computational fluid dynamics (CFD) modeling coupled with high-frequency electromagnetic field analysis and the arbitrary Lagrangian–Eulerian (ALE) method. The difference in the oscillation behavior between the solid and molten samples was explained by the damping of the electromagnetic induction and liquid viscosity. The motion of the mass center, melt shape, flow pattern, and Lorentz force in the levitated melt were determined within a wide excitation current range. With the increase in the applied current, the melt’s centroid position rose sharply in the area with low current but displayed a slow increase in the area with high current. Meanwhile, the stable shape of the bulk melt showed the typical transition from a long taper through a short taper and then into a rhombus. The internal flow pattern transformed from a simple double-loop structure to a complex configuration with three or four loops. The dependence of the deformation on the Bond number was analyzed in the two types of levitators. In addition, the stable shape and swing process of the bulk Al melt within the two types of electromagnetic levitation (EML) systems were quantitatively studied under protective inert gas conditions. The melt contour could be well described by the 10th Legendre polynomial function with a deviation of less than 0.5 pct.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Constitutive Behavior and Hot Workability of a Hot Isostatic Pressed Ti-22Al-25Nb Alloy during Hot Compression

A Ti-22Al-25Nb alloy was fabricated from prealloyed powders by hot isostatic pressing for 2 h at a temperature of 1050 °C and pressure of 100 MPa. The hot deformation behavior of the Ti-22Al-25Nb alloy was characterized by isothermal compression testing at deformation temperatures between 900 and 1060 °C and strain rates between 0.001 and 1 s{sup −1}. Based on the true stress–strain curves, a constitutive equation was constructed to describe the flow stress as a function of the strain rate and deformation temperature. Three-dimensional (3D) processing maps were developed based on dynamic material model theory using the stress flow data to identify the instability and optimization regions of the hot processing parameters. The results show that the flow stress decreases with increasing deformation temperature and decreasing strain rate, and the softening mechanisms are different under different deformation conditions. The apparent activation energies in the (α{sub 2} + β/B2 + O) and (α{sub 2} + B2) phase regions are calculated to be 865.177 and 590.661 kJ/mol, respectively, which suggests that the hot isostatic pressed (HIPed) Ti-22Al-25Nb alloy requires a high hot deformation activation energy. Combined with microstructural observations, the optimal processing domains are determined to be a temperature range of 1030-1060 °C and strain rate range of 0.01-0.1 s{sup −1} in the α{sub 2} + B2 phase region. Moreover, the results indicate that adiabatic shear bands and severe inhomogeneous deformation cause flow instability at lower temperatures (900-1005 °C) and higher strain rates (> 0.1 s{sup −1}).

36 MATERIALS SCIENCE↗
DOE OSTI2022

Biocatalytic system for comparatively assessing the functional association of monolignol cytochrome P450 monooxygenases with their redox partners

Lignin is a complex heterogenous polymer derived from oxidative radical polymerization of three monolignols, i.e., p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. These lignin monomeric precursors structurally differ in their methoxy groups of the benzene rings. In phenylpropanoid-monolignol biosynthetic pathway, the endoplasmic reticulum (ER)-resident cytochrome P450 monooxygenases, cinnamate 4-hydroxylase, coumaroyl ester 3´-hydroxylase and ferulate 5-hydroxylase, establish the key structural characteristics of monolignols. The catalysis of cytochrome P450 monooxygenase requires reducing power, which is supplied by the ER electron transfer chains, composed of cytochrome P450 oxidoreductase (CPR), cytochrome b5 reductase (CBR) and/or cytochrome b5 protein (CB5), from cofactor NADPH or NADH. While NADPH-dependent CPR serves as the typical electron donor for most P450 enzymes, in some cases, the CBR-CB5 or CPR-CB5 electron transfer system also transfers electrons to the terminal P450 enzymes. There are tremendous studies focusing on the discovery and characterization of cytochrome P450 monooxygenases. However, very limited attention has been paid to the versatility and the roles of electron transfer components in the P450 catalytic system. Due to the membrane-residence property of both P450 enzymes and electron transfer components, it is challenging to establish an effective experimental system to evaluate the functional association of P450s with their redox partners. This chapter describes a yeast cell biocatalytic system and the related experimental procedures for comparatively assessing the functional relationship of monolignol biosynthetic P450 enzymes and different redox partners in their catalysis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Process optimization of complex geometries using feed forward control for laser powder bed fusion additive manufacturing

Additive manufacturing (AM) enables the fabrication of complex designs that are difficult to create by other means. Metal parts manufactured by laser powder bed fusion (LPBF) can incorporate intricate design features and demonstrate desirable mechanical properties. However, printing a part that is qualified for its intended application often involves reprinting and discarding many parts to eliminate defects, improve dimensional accuracy, and increase repeatability. The process of iteratively converging on the appropriate build parameters increases the time and cost of creating functional LPBF manufactured parts. This work describes a fast, scalable method for part-scale process optimization of arbitrary geometries. Additionally, the computational approach uses feature extraction to identify scan vectors in need of parameter adaptation and applies results from simulation-based feed forward control models. This method provides a framework to quickly optimize complex parts through the targeted application of models with a range of fidelity and by automating the transfer of optimization strategies to new part designs. The computational approach and algorithmic framework are described, a software package is implemented, the method is applied to parts with complex features, and parts are printed on a customized open architecture LPBF machine.

3D printing↗
DOE OSTI2023

The neutron number probability distribution in coupled lumped assemblies

Here, the validity of the gamma distribution in describing the neutron number probability distribution function for both isolated and coupled multiplying assemblies when constrained to reproduce the true mean and variance is investigated in lumped geometry by numerical comparison with kinetic Monte Carlo simulations. The mean and variance are obtained from numerical solution of moment equations constructed from the relevant forward Master equation with assembly coupling coefficients obtained from a view factor method. Numerical results for a two-group, two coupled assemblies model, with static and dynamic reactivity insertion, show that except for subcritical assemblies, the gamma distribution well-approximates the number distribution. Differences in the fast and thermal neutron population shapes are explained in terms of effective source strengths due to downscatter and coupling.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Expression of ZO1, vimentin, pan-cadherin and AGTR1 in tanycyte-like cells of the sulcus medianus organum

Highlights: • Sulcus Medianus Organum contains ependyma with distinct tanycyte-like population. • These cells express ZO1, vimentin, pan-cadherin and angiotensin II type 1 receptors. • Long basal processes bridge these tanycyte-like cells to deeper blood vessels. Tanycytes are a specialized ependymal lining of brain ventricles with exceptional features of having long basal processes and junctional complexes between cell bodies. These tanycytes are present at the regions of circumventricular organs (CVOs) which possess common morphological and functional features enabling them to be described as the brain windows where the barrier systems have special properties. Previous studies detailed seven of these CVOs but little information is available regarding another putative site at the rostral part of the median sulcus of the 4th ventricle, or the sulcus medianus organum (SMO). Here we performed a pilot immunohistochemical study to support earlier observations suggesting the SMO as a novel CVO. We labeled rat brain with ZO1, vimentin, pan-cadherin and angiotensin II type 1 receptors markers which showed a morphologically distinct population of cells at the region of the SMO similar to tanycytes present in the median eminence, a known CVO. These cells had basal processes reaching the deeply seated blood vessels while the caudal part of the median sulcus did not show similar long cellular extensions. We concluded that tanycyte-like cells are present in the SMO in a pattern resembling that of other CVOs where the strategic location of the SMO is probably for signal integration between brainstem nuclei and the rostrally located neuronal centers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Through a glass darkly: In-situ x-ray computed tomography imaging of feed melting in continuously fed laboratory-scale glass melter

his study describes the first direct in-situ 3-D observation of a steady-state melting process by imaging a laboratory-scale slurry-fed glass melter in operation by x-ray computed tomography. Features of the reacting glass-feed, the foam layer underneath, and cavities in the glass melt pool are reconstructed in three-dimensional images. A slurry pool formed in a deep central caldera of dense dried feed, which penetrated into the glass melt. Slurry overflow from the caldera led to fast-dried and highly porous feed structure. A thin layer of foam separated the caldera from the melt. Bubbles ?5-15 mm in diameter were seen to grow beneath the reacting feed and move through the melt to escape at the edge. Pore morphology is benchmarked against computed tomography scans of a pellet of reacting simulated waste glass feed, and evolved gas analysis describes the gases generated as a function of temperature. Cooling artifacts are imaged and compared to previous studies of quenched cold caps. Detailed understanding of processes occurring during the conversion process in and below the reacting feed layer is necessary for the development of representative models of the melting process.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Results on radiation tolerance of diamond detectors

In sight of the luminosity increase of the High Luminosity-LHC (HL-LHC), most experiments at the CERN Large Hadron Collider (LHC) are planning upgrades for their innermost layers in the next 5–10 years. These upgrades will require more radiation tolerant technologies than exist today. Usage of Chemical Vapor Deposition (CVD) diamond as detector material is one of the potentially interesting technologies for the upgrade. CVD diamond has been used extensively in the beam condition monitors of BaBar, Belle, CDF and all LHC experiments. Measurements of the radiation tolerance of the highest quality polycrystalline CVD material for a range of proton energies, pions and neutrons obtained with this material are presented. In addition, new results on the evolution of various semiconductor parameters as a function of the dose rate are described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Gamma-ray spectroscopy using angular distribution of Compton scattering

We present a novel method to perform gamma-ray spectroscopy suitable for extreme pileup situations, wherein traditional pulse-height spectroscopy is infeasible or impractical. One example of such application is spectral characterization of intense laser-based radiation sources that employ laser wakefield acceleration, in which a large number of photons can be produced in a well-collimated beam on a picosecond or shorter timescale. The method relies on the angularly-resolved calorimetric measurement of Compton scattering. The probability for a photon to undergo Compton scattering into a given solid angle is a function of its energy and is described by the Klein–Nishina formula. By first Compton scattering the incident beam and then measuring the total energies deposited in multiple detectors placed at various scattering angles, the incident beam energy spectrum can be reconstructed without resolving the individual events in detectors. Here, we compare the performance of an maximum likelihood expectation maximization algorithm with that of an artificial neural network to measure the energy spectrum of a beam of monoenergetic gamma rays from 137Cs decay. We demonstrate that the method can be used to reconstruct the characteristic inverse Compton scattering spectra.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Experimental observations of bifurcated power decay lengths in the near Scrape-Off Layer of ST40 High Field Spherical Tokamak

The scrape-off layer parallel heat flux decay lengths measured at ST40, a high field, low aspect ratio spherical tokamak, have been observed to bifurcate into two groups. The wide group follows established H-mode scalings (ranging between 2 to 8 mm) while the narrow group falls up to 10 times below these scalings (between 0.2 and 0.8 mm), being comparable to the ion total Larmor radius rather than the ion poloidal Larmor radius. The heat flux profiles of the latter group can only be described by a multi-exponential function, rather than the single exponential function convoluted with a Gaussian. The onset of the narrow scrape-off layer width is observed to be associated with suppressed magnetic fluctuations, suggesting reduced electromagnetic turbulence levels in the SOL.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

The Fermi function and the neutron's lifetime

The traditional Fermi function ansatz for nuclear beta decay describes enhanced perturbative effects in the limit of large nuclear charge Z and/or small electron velocity β. We define and compute the quantum field theory object that replaces this ansatz for neutron beta decay, where neither of these limits hold. We present a new factorization formula that applies in the limit of small electron mass, analyze the components of this formula through two loop order, and resum perturbative corrections that are enhanced by large logarithms. We apply our results to the neutron lifetime, supplying the first two-loop input to the long-distance corrections. Our result can be summarized as τ n x |V ud | 2 [1 + 3λ 2 ] [1 + Δ R ] = $\frac{5263.284(17) s}{1 + 27.04(7) x 10^{-3}}$ with |V ud | the up-down quark mixing parameter, τ n the neutron's lifetime, λ the ratio of axial to vector charge, and Δ R the short-distance matching correction. We find a shift in the long-distance radiative corrections compared to previous work, and discuss implications for extractions of |V ud | and tests of the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

A Three-Dimensional, Analytical Wind Turbine Wake Model: Flow Acceleration, Empirical Correlations, and Continuity

A new, three-dimensional, analytical, steady-state wake model is presented that includes local flow acceleration near the rotor, improving the wake description compared to existing models. Wake structures such as the momentum deficit and regions of accelerated flow are concisely described with compound and normal Gaussian functions. Large-eddy simulations (LES) are used as training data to develop the model using two in-line turbines under various inflow conditions parameterized by hub-height wind speed and turbulence intensity. Mass conservation is considered by fixing two components of the wake velocity model and optimizing the third to best satisfy continuity; after which, the model performs comparably if not better than existing work with regards to both relative error and mass consistency. The final model demonstrates a high degree of flexibility, making use of empirical correlations to scale across different inflow conditions. The inclusion of these effects is capable of revealing unused opportunities for enhanced power generation by aligning wake trajectories with these regions of accelerated flow.

modeling↗
DOE OSTI2024

Kinetic stability of Chapman–Enskog plasmas

In this paper, we investigate the kinetic stability of classical, collisional plasma – that is, plasma in which the mean-free-path $\lambda$ of constituent particles is short compared with the length scale $L$ over which fields and bulk motions in the plasma vary macroscopically, and the collision time is short compared with the evolution time. Fluid equations are typically used to describe such plasmas, since their distribution functions are close to being Maxwellian. The small deviations from the Maxwellian distribution are calculated via the Chapman–Enskog (CE) expansion in $\lambda /L \ll 1$ , and determine macroscopic momentum and heat fluxes in the plasma. Such a calculation is only valid if the underlying CE distribution function is stable at collisionless length scales and/or time scales. We find that at sufficiently high plasma $\beta$ , the CE distribution function can be subject to numerous microinstabilities across a wide range of scales. For a particular form of the CE distribution function arising in strongly magnetised plasma ( viz. plasma in which the Larmor periods of particles are much smaller than collision times), we provide a detailed analytic characterisation of all significant microinstabilities, including peak growth rates and their associated wavenumbers. Of specific note is the discovery of several new microinstabilities, including one at sub-electron-Larmor scales (the ‘whisper instability’) whose growth rate in certain parameter regimes is large compared with other instabilities. Our approach enables us to construct the kinetic stability maps of classical, two-species collisional plasma in terms of $\lambda$ , the electron inertial scale $d_e$ and the plasma $\beta$ . This work is of general consequence in emphasising the fact that high- $\beta$ collisional plasmas can be kinetically unstable; for strongly magnetised CE plasmas, the condition for instability is $\beta \gtrsim L/\lambda$ . In this situation, the determination of transport coefficients via the standard CE approach is not valid.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Tailoring Interfaces in Solid-State Batteries Using Interfacial Thermochemistry and Band Alignment

Solid-state lithium ion batteries have enhanced thermal stability compared to batteries using liquid electrolytes. Although their practical implementation is limited by undesired side reactions between the electrode and electrolyte, different modification strategies have been proposed to stabilize these reactive interfaces. These approaches have been primarily based upon bulk materials properties, however, which may not necessarily be representative of the chemistry at the solid/solid interface. In this work, first principles calculations and X-ray scattering experiments are used to elucidate molecular-level reactivity and develop design principles for tailored interfaces based on surface and interfacial properties. Because of its well-known instability, the interface between the Li metal anode and the lithium lanthanum titanate (LLTO) solid electrolyte is applied as a model system. Density functional theory calculations are used to describe bulk, surface, and interfacial thermochemistry of the Li/LLTO system, and interfacial reconstruction is probed using ab initio molecular dynamics. These simulations of the Li/LLTO interface demonstrate facile decomposition concomitant with reduction of Ti 4+ ions. Based on further insights from computational analysis of the surface band edge positions, La 2 O 3 is proposed as an interlayer coating and is shown to provide an energetic barrier for interfacial charge transfer and decomposition reactions from X-ray reflectivity measurements and theoretical calculations. The findings in this work suggest that design strategies based on surface and interfacial properties can be used to kinetically stabilize electrode/electrolyte interfaces in solid-state batteries.

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

Regioisomer-Specific Crystallization of Diglycidyl Ether of Bisphenol F Epoxy Resin

Diglycidyl ether of bisphenol F (DGEBF) is a common industrial epoxy resin, desired for its possible replacement of the bisphenol A (BPA) analogue DGEBA due to potential health hazards of BPA. During curing, crystallization of the DGEBF resin can cause inaccurate resin-to-hardener ratios, resulting in incomplete crosslinking; therefore, understanding the crystallization of DGEBF is important for proper industrial control of the material. Here, in this work, we utilized a combination of single-crystal x-ray diffraction, Raman spectroscopy, and 1 H-NMR to investigate the crystallization of DGEBF. We observed crystallization of two DGEBF regioisomers: ortho-ortho’-DGEBF and ortho-para’-DGEBF, and report their crystal structures. Notably, para-para’-DGEBF crystallization is not observed, indicating crystallization of this regioisomer does not occur under ambient conditions. Density functional theory calculations were performed to describe the phonon modes of the ortho-ortho’- and ortho-para’-DGEBF structures, corroborating Raman signatures for the respective isomers. Using a phonon mode analysis, we identify the presence of three specific optical vibrational modes at 631.3, 344.1, and 345.6 cm -1 that are unique to the para monomer. This work offers insights into the crystallization behavior of DGEBF resins under ambient conditions and may inform potential industrial application of this material.

Neu, Jennifer [Oak Ridge National Laboratory (ORNL↗
DOE OSTI2022

Multifunctional Cu 2 TSiS 4 (T = Mn and Fe): Polar Semiconducting Antiferromagnets with Nonlinear Optical Properties

In this work, Cu 2 TSiS 4 (T = Mn and Fe) polycrystalline and single-crystal materials were prepared with high-temperature solid-state and chemical vapor transport methods, respectively. The polar crystal structure (space group Pmn2 1 ) consists of chains of corner-sharing and distorted CuS 4 , Mn/FeS 4 , and SiS 4 tetrahedra, which is confirmed by Rietveld refinement using neutron powder diffraction data, X-ray single-crystal refinement, electron diffraction, energy-dispersive X-ray spectroscopy, and second harmonic generation (SHG) techniques. Magnetic measurements indicate that both compounds order antiferromagnetically at 8 and 14 K, respectively, which is supported by the temperature-dependent (100–2 K) neutron powder diffraction data. Additional magnetic reflections observed at 2 K can be modeled by magnetic propagation vectors k = (1/2,0,1/2) and k = (1/2,1/2,1/2) for Cu 2 MnSiS 4 and Cu 2 FeSiS 4 , respectively. The refined antiferromagnetic structure reveals that the Mn/Fe spins are canted away from the ac plane by about 14°, with the total magnetic moments of Mn and Fe being 4.1(1) and 2.9(1) μ B , respectively. Both compounds exhibit an SHG response with relatively modest second-order nonlinear susceptibilities. Density functional theory calculations are used to describe the electronic band structures.

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

Simplifying the Chemical Design of Nonfused-Ring Electron Acceptors─Lessons Learned from Thienothiophene and Benzodithiophene Cores

Nonfused-ring electron acceptors (NFREA)s have been proposed as alternatives to fused-ring acceptors in organic photovoltaics (OPV)s. The simpler molecular design of NFREAs results in a reduced synthetic complexity, potentially lowering manufacturing costs, and easier access to desired optoelectronic properties by structural modifications. However, they have not seen the same rise in popularity as fused nonfullerene acceptors (NFA)s due to their lower performances in devices. In this work, we explore structure–property relationships of three NFREA molecules based on thieno[3,2-b]thiophene (TT) and benzo[1,2-b:4,5-b′]dithiophene (BDT) cores and malononitrile functionalized-isatin end group acceptors. We describe their synthetic routes, computational analysis, and photophysical and electronic properties. Here, we investigated the effect of changing the core from TT to BDT on electronic properties of the molecules─a result of raising/lowering of the frontier molecular orbital (FMO) levels. We also explored the effect of branched vs nonbranched alkyl groups on the morphological and blend-capabilities in bulk heterojunction (BHJ) OPV devices. These effects were then reflected in the overall device performances, primarily due to favorable FMO energy alignment between the NFREA and polymer. To investigate the behavior of the excited states of the NFREAs within the active layer of the devices, we performed time-resolved microwave conductivity and transient absorption experiments, which confirmed that the TT molecules exhibited very low conductance while the BDT molecule showed moderate photoconductance. Our combined theoretical, synthetic, device, and charge carrier dynamics studies of these materials reveal the central role that structure–property relationships play in future molecular designs of NFREAs that can perform as well as their fused counterparts.

14 SOLAR ENERGY↗