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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Calorimetry can detect the early onset of hydrolysis in hybrid supercapacitors with aqueous electrolytes

This study investigates the effect of cation species on the onset of electrolyte hydrolysis in hybrid supercapacitors with aqueous electrolytes using isothermal operando calorimetry. The cells consisted of a positive α-MnO 2 cryptomelane electrode and a negative activated carbon (AC) electrode with either 0.5 M K 2 SO 4 or 0.5 M Cs 2 SO 4 aqueous electrolytes. They were characterized using cyclic voltammetry and galvanostatic cycling. In addition, the instantaneous heat generation rate at each electrode was measured using a custom isothermal operando calorimeter. Heat generation associated with resistive losses (Joule heating) and reversible ion adsorption/desorption was clearly identified. For larger potential windows, an endothermic dip, attributed to the onset of hydrolysis, was observed at the positive α-MnO 2 electrode where K + and Cs + ions engaged in fast surface redox reactions. Interestingly, this endothermic dip appeared at 1.8 V and 2.0 V for K 2 SO 4 and Cs 2 SO 4 aqueous electrolytes, respectively. The difference in the stable operating potential window was attributed to thinner solvation shell around Cs + cation than for K + thus reducing the amount of water present near the electrodes as ions partially shed their solvation shells during adsorption. The early onset of hydrolysis could be observed by isothermal operando calorimetry before it could be observed with conventional electrochemical methods.

42 ENGINEERING↗
DOE OSTI2014

Phase transitions and unusual behavior of heat capacity in metal organic framework compound Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}·N{sub 2}(CH{sub 2}){sub 6}

Thermodynamic properties of high-porous metal-organic framework (MOF) compound Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}·N{sub 2}(CH{sub 2}){sub 6} were studied in the temperature range 8.9–300 K using low-temperature adiabatic calorymetry and DSC methods. Phase transitions were observed at ∼15, ∼60, and ∼135 K. It is shown that specific heat of the compound obeys the classical Debye law C{sub p}∼T{sup 3} only below 15 K, whereas above 15 K it is proportional to the first degree of temperature, C{sub p}∼T, to indicate a strong anisotropy of crystal vibrations corresponding to 1D continuum. It is shown that the strong anisotropy can be related to coordination interaction of Zn{sup 2+} and N{sub 2}(CH{sub 2}){sub 6} ligands in the specific structure of compound Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}·N{sub 2}(CH{sub 2}){sub 6}. - Graphical abstract: Specific heat C{sub p} is proportional to the first degree of temperature showing a strong anisotropy of crystal vibrations corresponding to 1D continuum in Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}·N{sub 2}(CH{sub 2}){sub 6.} - Highlights: • Specific heat capacity of Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}·N{sub 2}(CH{sub 2}){sub 6} was first studied at 8.9–300 K. • Phase transitions were observed at ∼15, ∼60, and ∼135 K. • The heat capacity is proportional to the first degree of temperature above 15 K. • The discovered dependency corresponds to a one-dimensional vibration continuum.

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

Highly sensitive optical ammonia gas sensor based on Sn Doped V2O5 Nanoparticles

Highlights: • Facile synthesis of pure and Sn-doped vanadium oxide (V{sub 2}O{sub 5}) nanoparticles. • Fabrication of Optical ammonia gas sensors based on synthesized nanoparticles. • High optical sensing response (77.84%) for synthesized 2 wt% Sn doped V{sub 2}O{sub 5} nanoparticles towards ammonia gas. - Abstract: Herein, we present the synthesis, characterization and optical ammonia gas sensing of pure and Sn-doped vanadium oxide (V{sub 2}O{sub 5}) nanoparticles prepared by the sol-gel process. The V{sub 2}O{sub 5} nanoparticles were doped with Sn concentrations of 2 wt%–6 wt%, and characterized using X-ray diffraction, atomic force microscopy, UV–vis spectroscopy and photoluminescence spectroscopy which confirmed the orthorhombic crystal structure. The crystalline size was found to decrease with enhancing the doping concentrations of Sn. The lattice-strain and crystalline size with the peak-broadening of pure and Sn doped V{sub 2}O{sub 5} nanoparticles were analyzed by William-Hall (W-H) method and size-strain plot. The UV–vis absorption showed a decrease in the energy band gap (3.27 eV–3.07 eV) with an increase in the Sn doping concentration. The Sn-doped V{sub 2}O{sub 5} nanoparticles were used to detect ammonia gas (5–50 ppm) through photoluminescence based detection method. Interestingly, it was observed that the optical response for the 2 wt% Sn doped V{sub 2}O{sub 5} nanoparticles was maximum (77.84%) towards 50 ppm ammonia compared to other V{sub 2}O{sub 5}nanoparticles based samples.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

A review of setup error in supine breast radiotherapy using cone-beam computed tomography

Setup error in breast radiotherapy (RT) measured with 3-dimensional cone-beam computed tomography (CBCT) is becoming more common. The purpose of this study is to review the literature relating to the magnitude of setup error in breast RT measured with CBCT. The different methods of image registration between CBCT and planning computed tomography (CT) scan were also explored. A literature search, not limited by date, was conducted using Medline and Google Scholar with the following key words: breast cancer, RT, setup error, and CBCT. This review includes studies that reported on systematic and random errors, and the methods used when registering CBCT scans with planning CT scan. A total of 11 relevant studies were identified for inclusion in this review. The average magnitude of error is generally less than 5 mm across a number of studies reviewed. The common registration methods used when registering CBCT scans with planning CT scan are based on bony anatomy, soft tissue, and surgical clips. No clear relationships between the setup errors detected and methods of registration were observed from this review. Further studies are needed to assess the benefit of CBCT over electronic portal image, as CBCT remains unproven to be of wide benefit in breast RT.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

The transport of suspended sediment in the wake of a marine hydrokinetic turbine: Simulations via a validated Discrete Random Walk (DRW) model

The interaction of sediment with Marine Hydrokinetic (MHK) Turbines is studied via turbulent flow simulation coupled with a model for particle dynamics. The Discrete Random Walk (DRW) model is commonly used for simulations of particle dispersion in environmental flows. A method to improve the accuracy of the DRW model in conjunction with RANS simulations of the flow around MHK turbines is presented. A key issues for the use of the DRW model in marine applications is identified, finding the right characteristic eddy lifetime scale, and a simple methodology based on G.I. Taylor's classical dispersion theory is develop to calibrate this physical model parameter. The model is validated against experiments in the literature and the physics of suspended sediment transport in the wake of an MHK turbine is studied with this improved method. The qualitative changes observed in the particle trajectories agree well with theoretical and empirical observations and the quantitive trends allow for comparison of multiple particle cases under different flow conditions, confirming that this implementation of CFD can become a powerful tool to select the most challenging cases, among the thousands of potential studies on the environmental effects of MHK energy, for further study with experiments and pilot projects.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

A data analytical approach for assessing the efficacy of Operational Technology active defenses against insider threats

In recent years, the need for Operational Technology (OT) defenses has been recognized, serving as an additional line of defense when Information Technology (IT) defenses are bypassed. This is no longer considered an uncommon possibility when dealing with advanced persistent threat (APT) actors expected to be state-sponsored and receiving insider assistance. In these extreme adversarial situations, OT defenses aim to provide another layer of defense for the system, introduced directly at the physical process level, as described by the sensors data, the system model, and control actions. Just like IT defenses, two schools of thought, i.e., passive and active defenses, have emerged to address this challenge. In active defenses, representing the focus of this paper, known signatures, synthesized based on the system's unique characteristics, are inserted into the system. In contradistinction, passive methods rely solely on observing system behavior in search of patterns of normal behavior with deviations thereof representing abnormal behavior. In their most sophisticated implementations, both passive and active defenses rely on the use of data analytics to identify the patterns and synthesize the observed and/or inserted signatures. Past research has shown that passive defenses may be bypassed by APT actors relying on data analytics and their intimate knowledge of the system to evade detection by respecting the patterns identified by the defenders. Here this manuscript explores the use of active defenses under the assumption that the attacker has privileged access to the system, including access to the system's model and sensors data. Specifically, this manuscript assesses the ability of active defenses to remain invisible to the attackers, and discusses the associated challenges that must be addressed to ensure their resiliency against APT actors.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2014

Adaptive and Unstructured Mesh Cleaving

We propose a new strategy for boundary conforming meshing that decouples the problem of building tetrahedra of proper size and shape from the problem of conforming to complex, nonmanifold boundaries. This approach is motivated by the observation that while several methods exist for adaptive tetrahedral meshing, they typically have difficulty at geometric boundaries. The proposed strategy avoids this conflict by extracting the boundary conforming constraint into a secondary step. We first build a background mesh having a desired set of tetrahedral properties, and then use a generalized stenciling method to divide, or “cleave”, these elements to get a set of conforming tetrahedra, while limiting the impacts cleaving has on element quality. In developing this new framework, we make several technical contributions including a new method for building graded tetrahedral meshes as well as a generalization of the isosurface stuffing and lattice cleaving algorithms to unstructured background meshes.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Organization of Lithium Cubane Clusters into Three-Dimensional Porous Frameworks by Self-Penetration and Self-Polymerization

Metal–organic frameworks based on lithium inherit the unique chemical and structural features of the metal ion itself. While the monomeric lithium node, usually 4-connected, is very desirable for designing zeolite-type networks, the resulting lithium MOF usually has limited stability, especially for 3-connected nets due to the solvent termination. The conventional design strategy based on lithium aryloxide clusters makes use of phenol-type ligands for cluster formation and a separate bifunctional ligand for cross-linking, which also leads to 4-connected nets. By integrating the roles of cluster-formation and framework-formation into a single ligand, 4-hydroxypyridine was previously shown to give a highly stable 8-connected framework. Still, its shortness and rigidity limit both the porosity and the type of framework topologies. Here, we demonstrate the new chemical and structural features of lithium cubane clusters with an elongated ligand, which results in two high-connected 3-D framework materials characterized by self-penetration and self-polymerization, respectively, unlike the commonly observed interpenetration. Such a method provides a feasible path to tune both stability and porosity in lithium-based MOFs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Defects in Layered van der Waals Heterostructures: Implications for Thermoelectrics

Layered van der Waals heterostructures provide extraordinary opportunities for applications such as thermoelectrics and allow for tunability of optical and electronic properties. The performance of devices made from these heterostructures will depend on their properties, which are sensitive to the nanoarchitecture (constituent layer thicknesses, layer sequence, etc.). However, performance will also be impacted by defects, which will vary in concentration and identity with the nanoarchitecture and preparation conditions. Here, we identify several types of defects and propose mechanisms for their formation, focusing on compounds in the ([SnSe] 1+δ ) m (TiSe 2 ) n system prepared using the modulated elemental reactants method. The defects were observed by atomic resolution high-angle annular dark-field scanning transmission electron microscopy and can be broadly categorized into those that form domain boundaries as a result of rotational disorder from the self-assembly process and those that are layer-thickness-related and result from local or global deviations in the amount of material deposited. Furthermore, defect type and density were found to depend on the nanoarchitecture of the heterostructure. Categorizing the defects provides insights into defect formation in these van der Waals layered heterostructures and suggests strategies for controlling their concentrations. Strategies for controlling defect type and concentration are proposed, which would have implications for transport properties for applications in thermoelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Biopolymer-Templated Titania Film Formation for Nanostructured Coatings Revealed by Machine Learning-Supported Time-Resolved Analysis

This study presents a machine learning approach to derive the film formation of biopolymer-templated titania nanostructures during spray deposition, in combination with in situ grazing-incidence small-angle X-ray scattering (GISAXS). A neural network trained on synthetic GISAXS data directly predicts domain-size distributions from experimental two-dimensional scattering patterns, capturing the full kinetics of nanostructure evolution with high temporal resolution. The predictions reveal hierarchical size distributions and periodic growth features, consistent with layer-by-layer spray deposition and validated by complementary scanning electron microscopy (SEM) imaging. Quantitative comparison with conventional parametric GISAXS fits shows good qualitative agreement, with systematic differences explained by domain-shape assumptions and resolved by applying a geometric scaling factor. Simulated SEM-like surfaces derived from neural network outputs reproduce the porous, foam-like nanoscale morphology observed experimentally, reinforcing the method’s credibility. This integrated approach enables real-time, nondestructive, statistically averaged monitoring of bulk nanostructure development in functional coatings, offering a scalable methodology to accelerate the characterization and process control of sustainably manufactured nanostructured titania films for energy-related applications such as photocatalysis and photovoltaics.

Heger, JulianEliah↗
DOE OSTI2019

Operando Spectroscopic and Kinetic Characterization of Aerobic Allylic C–H Acetoxylation Catalyzed by Pd(OAc) 2 /4,5-Diazafluoren-9-one

Allylic C–H acetoxylations are among the most widely studied palladium(II)-catalyzed C–H oxidation reactions. While the principal reaction steps are well established, key features of the catalytic mechanisms are poorly characterized, including the identity of the turnover-limiting step and the catalyst resting state. In this study, we report a mechanistic study of aerobic allylic acetoxylation of allylbenzene with a catalyst system composed of Pd(OAc) 2 and 4,5-diazafluoren-9-one (DAF). The DAF ligand is unique in its ability to support aerobic catalytic turnover, even in the absence of benzoquinone or other co-catalysts. Herein, we describe operando spectroscopic analysis of the catalytic reaction using X-ray absorption and NMR spectroscopic methods that allow direct observation of the formation and decay of a palladium(I) species during the reaction. Kinetic studies reveal the presence of two distinct kinetic phases: (1) a burst phase, involving rapid formation of the allylic acetoxylation product and formation of the dimeric Pd I complex [Pd I (DAF)(OAc)] 2 , followed by (2) a post-burst phase that coincides with evolution of the catalyst resting state from the Pd I dimer into a π-allyl-Pd II species. The data provide unprecedented insights into the role of ancillary ligands in supporting catalytic turnover with O 2 as the stoichiometric oxidant and establish an important foundation for the development of improved catalysts for allylic oxidation reactions.

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

An Overview of Interactions and Feedbacks Between Ice Sheets and the Earth System

Abstract Ice sheet response to forced changes—such as that from anthropogenic climate forcing—is closely regulated by two‐way interactions with other components of the Earth system. These interactions encompass the ice sheet response to Earth system forcing, the Earth system response to ice sheet change, and feedbacks resulting from coupled ice sheet/Earth system evolution. Motivated by the impact of Antarctic and Greenland ice sheet change on future sea level rise, here we review the state of knowledge of ice sheet/Earth system interactions and feedbacks. We also describe emerging observation and model‐based methods that can improve understanding of ice sheet/Earth system interactions and feedbacks. We particularly focus on the development of Earth system models that incorporate current understanding of Earth system processes, ice dynamics, and ice sheet/Earth system couplings. Such models will be critical tools for projecting future sea level rise from anthropogenically forced ice sheet mass loss.

Fyke, Jeremy↗
DOE OSTI2018

Visualizing the bidirectional optical transfer function for near-field enhancement in waveguide coupled plasmonic transducers

Here, we report visualizations of the bidirectional near-field optical transfer function for a waveguide-coupled plasmonic transducer as a metrology technique essential for successful development for mass-fabricated near-field devices. Plasmonic devices have revolutionized the observation of nanoscale phenomena, enabling optical excitation and readout from nanoscale regions of fabricated devices instead of as limited by optical diffraction. Visualizations of the plasmonic transducer modes were acquired both by local near-field excitation of the antenna on the front facet of a waveguide using the focused electron beam of a scanning electron microscope as a probe of the near-field cathodoluminescence during far-field collection from the back facet of the waveguide, and by local mapping of the optical near-field for the same antenna design using scattering scanning near-field optical microscopy as a probe of the near-field optical mode density for far-field light focused into the back facet of the waveguide. Strong agreement between both measurement types and numerical modeling was observed, indicating that the method enables crucial metrological comparisons of as fabricated device performance to as-modeled device expectations for heat-assisted magnetic recording heads, which can be extended to successful development of future near-field-on-chip devices such as optical processor interconnects.

42 ENGINEERING↗
DOE OSTI2018

Incident wavelength and polarization dependence of spectral shifts in β-Ga2O3 UV photoluminescence

Abstract We report polarization dependent photoluminescence studies on unintentionally-, Mg-, and Ca-doped β -Ga 2 O 3 bulk crystals grown by the Czochralski method. In particular, we observe a wavelength shift of the highest-energy UV emission which is dependent on the pump photon energy and polarization. For 240 nm (5.17 eV) excitation almost no shift of the UV emission is observed between E || b and E || c , while a shift of the UV emission centroid is clearly observed for 266 nm (4.66 eV), a photon energy lying between the band absorption onsets for the two polarizations. These results are consistent with UV emission originating from transitions between conduction band electrons and two differentially-populated self-trapped hole (STH) states. Calcuations based on hybrid and self-interaction-corrected density functional theories further validate that the polarization dependence is consistent with the relative stability of two STHs. This observation implies that the STHs form primarily at the oxygen atoms involved in the original photon absorption event, thus providing the connection between incident polarization and emission wavelength. The data imposes a lower bound on the energy separation between the self-trapped hole states of ~70–160 meV, which is supported by the calculations.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Spin dynamics of [1,2- 13 C 2 ]pyruvate hyperpolarization by parahydrogen in reversible exchange at micro Tesla fields

Hyperpolarization of 13 C-pyruvate via Signal Amplification By Reversible Exchange (SABRE) is an important recent discovery because of both the relative simplicity of hyperpolarization and the central biological relevance of pyruvate as a biomolecular probe for in vitro or in vivo studies. Here, we analyze the [1,2- 13 C 2 ]pyruvate-SABRE spin system and its field dependence theoretically and experimentally. We provide first-principles analysis of the governing 4-spin dihydride- 13 C 2 Hamiltonian and numerical spin dynamics simulations of the 7-spin dihydride- 13 C 2 –CH 3 system. Furthermore, the analytical and the numerical results are compared to matching systematic experiments. With these methods we unravel the observed spin state mixing of singlet states and triplet states at microTesla fields and we also analyze the dynamics during transfer from micro-Tesla field to high field for detection to understand the resulting spectra from the [1,2- 13 C 2 ]pyruvate-SABRE system.

13C pyruvate↗
DOE OSTI2016

Planck 2015 results: XVIII. Background geometry and topology of the Universe

We report that maps of cosmic microwave background (CMB) temperature and polarization from the 2015 release of Planck data provide the highestquality full-sky view of the surface of last scattering available to date. This enables us to detect possible departures from a globally isotropic cosmology. We present the first searches using CMB polarization for correlations induced by a possible non-trivial topology with a fundamental domain that intersects, or nearly intersects, the last-scattering surface (at comoving distance χ rec ), both via a direct scan for matched circular patterns at the intersections and by an optimal likelihood calculation for specific topologies. We specialize to flat spaces with cubic toroidal (T3) and slab (T1) topologies, finding that explicit searches for the latter are sensitive to other topologies with antipodal symmetry. These searches yield no detection of a compact topology with a scale below the diameter of the last-scattering surface. The limits on the radius R i of the largest sphere inscribed in the fundamental domain (at log-likelihood ratio ΔlnL > -5 relative to a simply-connected flat Planck best-fit model) are: R i > 0.97 χ rec for the T3 cubic torus; and R i > 0.56 χ rec for the T1 slab. The limit for the T3 cubic torus from the matched-circles search is numerically equivalent, R i > 0.97 χ rec at 99% confidence level from polarization data alone. We also perform a Bayesian search for an anisotropic global Bianchi VII h geometry. In the non-physical setting, where the Bianchi cosmology is decoupled from the standard cosmology, Planck temperature data favour the inclusion of a Bianchi component with a Bayes factor of at least 2.3 units of log-evidence. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. Fitting the induced polarization pattern for this model to the Planck data requires an amplitude of -0.10 ± 0.04 compared to the value of + 1 if the model were to be correct. In the physically motivated setting, where the Bianchi parameters are coupled and fitted simultaneously with the standard cosmological parameters, we find no evidence for a Bianchi VII h cosmology and constrain the vorticity of such models to (ω/H) 0 < 7.6 × 10 -10 (95% CL).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

GRB 180128A: A second magnetar giant flare candidate from the Sculptor Galaxy

Magnetars are slowly rotating neutron stars that possess the strongest magnetic fields known in the cosmos (10 14 − 10 15 G). They display a range of transient high-energy electromagnetic activity. The brightest and most energetic of these events are the gamma-ray bursts (GRBs) known as magnetar giant flares (MGFs), with isotropic energies E iso ≈ 10 44 − 10 46 erg. Only seven MGF detections have been made to date: three unambiguous events occurred in our Galaxy and the Magellanic Clouds, and the other four MGF candidates are associated with nearby star-forming galaxies. As all seven identified MGFs are bright at Earth, additional weaker events likely remain unidentified in archival data. We conducted a search of the Fermi Gamma-ray Burst Monitor database for candidate extragalactic MGFs and, when possible, collected localization data from the Interplanetary Network (IPN) satellites. Our search yielded one convincing event, GRB 180128A. IPN localizes this burst within NGC 253, commonly known as the Sculptor Galaxy. The event is the second MGF in modern astronomy to be associated with this galaxy and the first time two bursts have been associated with a single galaxy outside our own. Here we detail the archival search criteria that uncovered this event and its spectral and temporal properties, which are consistent with expectations for a MGF. We also discuss the theoretical implications and finer burst structures resolved from various binning methods. Our analysis provides observational evidence of an eighth identified MGF.

Trigg, Aaron C. (ORCID:000900068598728X)↗
DOE OSTI2013

The use of carbon stable isotope ratios in drugs characterization

Isotopic Ratio Mass Spectrometry (IRMS) is an effective toll to be used for drug product authentication. The isotopic composition could be used to assist in the differentiation between batches of drugs and assist in the identification of counterfeit materials on the market. Only two factors affect the isotopic ratios in pharmaceutical components: the isotopic composition of the raw materials and the synthetic processes performed upon them. Counterfeiting of pharmaceutical drugs threatens consumer confidence in drug products companies' economical well-being. In this preliminary study, the analyzed samples consist in two types of commercially available analgesics, which were purchases from Romanian pharmacies. Differences in δ{sup 13}C between batches from −29.7 to −31.6% were observed, demonstrating that this method can be used to differentiate among individual drug batches and subsequently identify counterfeits on the market. On the other hand, carbon isotopic ratios differences among producers were recorded, the variations being between −31.3 to −34.9% for the same type of analgesic, but from different manufactures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗