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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Repetitive Dosing of Fumed Silica Leads to Profibrogenic Effects through Unique Structure–Activity Relationships and Biopersistence in the Lung

Contrary to the notion that the use of fumed silica in consumer products can “generally (be) regarded as safe” (GRAS), the high surface reactivity of pyrogenic silica differs from other forms of synthetic amorphous silica (SAS), including the capacity to induce membrane damage and acute proinflammatory changes in the murine lung. Additionally, the chain-like structure and reactive surface silanols also allow fumed silica to activate the NLRP3 inflammasome, leading to IL-1β production. This pathway is known to be associated with subchronic inflammation and profibrogenic effects in the lung by α-quartz and carbon nanotubes. Different from the latter materials, bolus dose instillation of 21 mg/kg fumed silica did not induce sustained IL-1β production or subchronic pulmonary effects. In contrast, the NLRP3 inflammasome pathway was continuously activated by repetitive-dose administration of 3 × 7 mg/kg fumed silica, 1 week apart. We also found that while single-dose exposure failed to induce profibrotic effects in the lung, repetitive dosing can trigger increased collagen production, even at 3 × 3 mg/kg. The change between bolus and repetitive dosing was due to a change in lung clearance, with recurrent dosing leading to fumed silica biopersistence, sustained macrophage recruitment, and activation of the NLRP3 pathway. These subchronic proinflammatory effects disappeared when less surface-reactive titanium-doped fumed silica was used for recurrent administration. Finally, these data indicate that while fumed silica may be regarded as safe for some applications, we should reconsider the GRAS label during repetitive or chronic inhalation exposure conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Structural and magnetic effects of Cd{sub 1-x}In{sub x}Cr{sub 2}Se{sub 4}

Polycrystalline CdCr{sub 2}Se{sub 4} spinels with non-magnetic indium substitution were investigated with an aim to study the influence of non-magnetic substitution at the Cd site on its structural and magnetic properties. We carried out powder XRD and magnetic measurements on three compositions: Cd{sub 1-x}In{sub x}Cr{sub 2}Se{sub 4} (x=0, 0.05, 0.1). The XRD patterns were analyzed by carrying out Rietveld analysis and structural parameters were estimated. Phase purity of the compounds using reitveld refinement technique where confirming the indium distribution at tetrahedral site of the cubic close-packed sublattice formed by the selenium ions. The chemical compositions of these compounds were determined by energy dispersive x-ray analysis. Compared to parent compound, CdCr{sub 2}Se{sub 4}, the ferromagnetic Curie temperature T{sub C} was found to decrease from 130K to 123K and 114K as x varied from 0 to 0.05 and 0.1 respectively, whereas the saturation magnetization increases in Cd{sub 0.95}In{sub 0.05}Cr{sub 2}Se{sub 4} and again decreases in Cd{sub 0.9}In{sub 0.1}Cr{sub 2}Se{sub 4}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Multifunctional Cationic Iridium(III) Complexes Bearing 2-Aryloxazolo[4,5- f ][1,10]phenanthroline (N^N) Ligand: Synthesis, Crystal Structure, Photophysics, Mechanochromic/Vapochromic Effects, and Reverse Saturable Absorption

A series of 2-aryloxazolo[4,5-$f$][1,10]phenanthroline ligands (N^N ligands) and their cationic iridium(III) complexes (1–11, aryl = 4-NO 2 -phenyl (1), 4-Br-phenyl (2), Ph (3), 4-NPh 2 -phenyl (4), 4-NH 2 -phenyl (5), pyridin-4-yl (6), naphthalen-1-yl (7), naphthalen-2-yl (8), phenanthren-9-yl (9), anthracen-9-yl (10), and pyren-1-yl (11)) were synthesized and characterized. By introducing different electron-donating or electron-withdrawing substituents at the 4-position of the 2-phenyl ring (1–5), or different aromatic substituents with varied degrees of π-conjugation (6–11) on oxazolo[4,5-$f$][1,10]phenanthroline ligand, we aim to understand the effects of terminal substituents at the N^N ligands on the photophysics of cationic Ir(III) complexes using both spectroscopic methods and quantum chemistry calculations. Complexes with the 4-R-phenyl substituents adopted an almost coplanar structure with the oxazolo[4,5-$f$][1,10]phenanthroline motif, while the polycyclic aryl substituents (except for naphthalen-2-yl) were twisted away from the oxazolo[4,5-$f$][1,10]phenanthroline motif. All complexes possessed strong absorption bands below 350 nm that emanated from the ligand-localized 1 $π,π*$/ 1 ILCT (intraligand charge transfer) transitions, mixed with 1 LLCT (ligand-to-ligand charge transfer)/ 1 MLCT (metal-to-ligand charge transfer) transitions. At the range of 350–570 nm, all complexes exhibited moderately strong 1 ILCT/ 1 LLCT/ 1 MLCT transitions at 350-450 nm, and broad but very weak 3 LLCT/ 3 MLCT absorption at 450-570 nm. Most of the complexes demonstrated moderate to strong room temperature phosphorescence both in solution and in the solid state. Among them, complex 7 also manifested a drastic mechanochromic and vapochromic luminescence effect. Except for complexes 1 and 4 that contain NO 2 or NPh 2 substituent at the phenyl ring, respectively, all other complexes exhibited moderate to strong triplet excited-state absorption in the spectral region of 440–750 nm. Moderate to very strong reverse saturable absorption (RSA) of these complexes appeared at 532 nm for 4.1 ns laser pulses. The RSA strength followed the trend of $7 > 11 > 9 > 3 > 2 ≈ 4 > 5 ≈ 10 ≈ 6 ≈ 8 > 1$. The photophysical studies revealed that the different 2-aryl substituents on the oxazole ring impacted the singlet and triplet excited-state characteristics dramatically, which in turn notably influenced the RSA of these complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Sr doping effect on micro structural, transport and magnetic properties in Pr{sub 1-x}Sr{sub x}MnO{sub 3} (0.2 ≤ x ≤ 0.4) nanomanganite

In this article, microstructural, magnetic, magneto-transport, electronic transport properties of Pr{sub 1-x}Sr{sub x}MnO{sub 3} system have been systematically studied in nanometric dimension over the range 0.2 ≤ x ≤ 0.4 by preparing the compound through pyrophoric reaction route. XRD diffraction measurements indicate that all the samples are in orthorhombic Pbnm space group. Electronic and magneto-transport properties of these materials have been thoroughly investigated in nanometric grain size modulation. These Sr doped compounds at x=0.3 exhibit more ferromagnetic metallic behavior at zero field and negative magneto resistance in low temperature. The different magnetic phase was found using ac magnetic susceptibility measurement. Magneto –transport nature is explained using spin polarization tunneling model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

The Effectiveness of Gd Contents of Fuel Basket Wall in UNF Shipping and Storage Cask - 16598

A more effective basket structure, which employs the single wall basket structure and more effective neutron absorbing materials compared to the conventional 3 wall structure with boron neutron absorber, is under development. The criticality of the cask was evaluated as a function of the Gd and B contents in the plate and the Gd-containing SS plate thickness while maintaining the basic geometry the same as the reference cask which uses boron compound as neutron absorber. The KENO-VI code in SCALE with the data library ENDF/B-VII 238-group was used. In all the range of interest, the k{sub eff} values are below 0.4 which is much lower than licensing limit of 0.95. As Gd content increases, the k{sub eff} exponentially decreases. The Gd added SS shows higher performance than B added case in low atomic percent region. The B case curve showed less steep slope than the Gd case. The results of the wall thickness effect calculation indicated that the k{sub eff} decreases with thickness increase until ∼6 mm and it increases as thickness increases over ∼7 mm. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Phosphonium-Organophosphate Ionic Liquids as Lubricant Additives: Effects of Cation Structure on Physicochemical and Tribological Characteristics

In our previous work we suggest great potential for a phosphonium-organophosphate ionic liquid (IL) as an antiwear lubricant additive. In this study, a set of five ILs were carefully designed and synthesized, with identical organophosphate anions but dissimilar phosphonium cations, to allow systematic investigation of the effects of cation alkyl chain length and symmetry on physicochemical and tribological properties. Symmetric cations with shorter alkyl chains seem to increase the density and thermal stability due to closer packing. On the other hand, either higher cation symmetry or longer alkyl moieties induce a higher viscosity, though the viscosity index is dependent more on molecular mass than on symmetry. While a larger cation size generally increases an IL’s solubility in nonpolar hydrocarbon oils, six-carbon seems to be the critical minimum alkyl chain length for high oil miscibility. Both the two ILs, that are mutually oil miscible, have demonstrated promising lubricating performance at 1.04% treat rate, though the symmetric-cation IL moderately outperformed the asymmetric-cation IL. Moreover, characterizations on the tribofilm formed by the best-performing symmetric-cation IL revealed the film thickness, nanostructure, and chemical composition. Our results provide fundamental insights for future molecular design in developing oil-soluble ILs as lubricant additives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Nuclear quantum effects on the structure and the dynamics of [H{sub 2}O]{sub 8} at low temperatures

We use ring-polymer-molecular-dynamics (RPMD) techniques and the semi-empirical q-TIP4P/F water model to investigate the relationship between hydrogen bond connectivity and the characteristics of nuclear position fluctuations, including explicit incorporation of quantum effects, for the energetically low lying isomers of the prototype cluster [H{sub 2}O]{sub 8} at T = 50 K and at 150 K. Our results reveal that tunneling and zero-point energy effects lead to sensible increments in the magnitudes of the fluctuations of intra and intermolecular distances. The degree of proton spatial delocalization is found to map logically with the hydrogen-bond connectivity pattern of the cluster. Dangling hydrogen bonds exhibit the largest extent of spatial delocalization and participate in shorter intramolecular O-H bonds. Combined effects from quantum and polarization fluctuations on the resulting individual dipole moments are also examined. From the dynamical side, we analyze the characteristics of the infrared absorption spectrum. The incorporation of nuclear quantum fluctuations promotes red shifts and sensible broadening relative to the classical profile, bringing the simulation results in much more satisfactory agreement with direct experimental information in the mid and high frequency range of the stretching band. While RPMD predictions overestimate the peak position of the low frequency shoulder, the overall agreement with that reported using an accurate, parameterized, many-body potential is reasonable, and far superior to that one obtains by implementing a partially adiabatic centroid molecular dynamics approach. Quantum effects on the collective dynamics, as reported by instantaneous normal modes, are also discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Ligand effects on electronic structure and bonding in U(iii) coordination complexes: a combined MCD, EPR and computational study

The trivalent oxidation state of uranium has been shown to undergo unique reactivity, from its ability to activate a variety of small molecules to its role in the catalytic reduction of ethene to ethane amongst others. Central to this unique reactivity and ability to rationally design ligands for isotope separation is the underlying uranium electronic structure. While electronic structure studies of U(IV), U(V), and U(VI) have been extensive, by comparison, analogous studies of more reduced oxidation states such as U(III) remains underdeveloped. Herein we report a combined MCD and EPR spectroscopic approach along with density functional theory and multireference wavefunction calculations to elucidate the effects of ligand perturbation in three uranium(III) Tp* complexes. Overall, the experimental and computational insight suggests that the change in ligand environment across this series of U(III) complexes resulted in only minor perturbations in the uranium electronic structure. This combined approach was also used to redefine the electronic ground state of a U(III) complex with a redox non-innocent Bipy - ligand. Overall, these studies demonstrate the efficacy of the combined experimental and theoretical approach towards evaluating electronic structure and bonding in U(III) complexes and provide important insight into the challenges in altering ligand environments to modify bonding and reactivity in uranium coordination chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of Molecular Structure on the CO 2 Separation Properties of Hydrophobic Solvents Consisting of Grafted Poly Ethylene Glycol and Poly Dimethylsiloxane Units

This work describes the preparation of a set of nine new novel hydrophobic PEG-substituted solvents. These solvents include linear, T-shaped, and disubstituted conformations of the PEG grafted with PDMS molecule. The effect of changing both the molecular conformation and length of PEG side arm on the physical properties and CO 2 absorption capacity was studied. These solvents are intended for separation of CO 2 and H 2 in precombustion CO 2 capture and are intended to replace the current-state-of-the-art glycol-based solvents and operate at a higher temperature. In conclusion, the properties of the disubstituted solvents are exceptionally well suited for precombustion CO 2 capture applications because of their hydrophobicity, high CO 2 solubility, low evaporation rate, and lack of foaming.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Ab initio nuclear structure from lattice effective field theory

This proceedings article reviews recent results by the Nuclear Lattice EFT Collaboration on an excited state of the {sup 12}C nucleus known as the Hoyle state. The Hoyle state plays a key role in the production of carbon via the triple-alpha reaction in red giant stars. We discuss the structure of low-lying states of {sup 12}C as well as the dependence of the triple-alpha reaction on the masses of the light quarks.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Effect of the nuclear charge of a fast structural ion on its internal effective stopping in collisions with atoms

The energy losses of fast structural ions in collisions with atoms have been considered in the eikonal approximation. The structural ions are ions consisting of a nucleus and a certain number of electrons bound to it. The effect of nuclear charge Z of the ion on its effective deceleration κ{sup (p)} (energy losses associated with excitation of only intrinsic ion shells) has been analyzed. It is shown that the allowance for the interaction of an atom with the ion nucleus for Z{sub a}Z/v > 1, where Z{sub a} is the charge of the atomic nucleus and v is the velocity of collisions in atomic units, considerably affects the value of κ{sup (p)}, which generally necessitates taking into account nonperturbatively the effect of both charges Z{sub a} and Z on κ{sup (p)}.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Effects of Phosphonate Structures on Brine–Biotite Interactions under Subsurface Relevant Conditions

Phosphonates have been widely used as scale inhibitors in energy-related subsurface operations, where their performance is greatly affected by interactions with rocks and minerals. However, information about commonly used phosphonate scale inhibitor–shale interactions is limited. In this study, using Fe-bearing mica (biotite) as a model phyllosilicate mineral, the effects of three common phosphonates, namely, iminodi(methylene)phosphonate (IDMP), nitrilotris(methylene)phosphonate (NTMP), and diethylenetriaminepenta(methylene)phosphonate (DTPMP), were studied at 95 °C and 102 atm CO2. During the experiments (0–70 h), IDMP remained stable, while NTMP and DTPMP were degraded and released phosphate, formate, and new phosphonates with smaller molecular weights. As a result of the differences in complexation capability, IDMP, with the fewest phosphonate functional groups, promoted biotite dissolution mainly through surface complexation and DTPMP, with the most functional groups, promoted biotite dissolution mainly through aqueous complexation. Furthermore, the presence of phosphonates enhanced secondary precipitation of P-, Fe-, and Al-bearing minerals, and their phosphonate structures affected the morphologies, phases, and distributions of secondary precipitates. Owing to phosphonate–biotite interactions (mainly as a result of surface adsorption), the biotite surfaces became much more hydrophilic. This study provides new insights into structure-dependent phosphonate–mineral interactions, and the results have important implications for the safety and efficiency of energy-related subsurface operations.

bio-inspired, mechanical behavior, carbon sequestr↗
DOE OSTI2015

Abnormal thermal expansion, multiple transitions, magnetocaloric effect, and electronic structure of Gd{sub 6}Co{sub 4.85}

The structure of known Gd{sub 4}Co{sub 3} compound is re-determined as Gd{sub 6}Co{sub 4.85}, adopting the Gd{sub 6}Co{sub 1.67}Si{sub 3} structure type, which is characterized by two disorder Co sites filling the Gd octahedral and a short Gd-Gd distance within the octahedra. The compound shows uniaxial negative thermal expansion in paramagnetic state, significant negative expansion in ferromagnetic state, and positive expansion below ca. 140 K. It also exhibits large magnetocaloric effect, with an entropy change of −6.4 J kg{sup −1} K{sup −1} at 50 kOe. In the lattice of the compound, Co atoms at different sites show different spin states. It was confirmed by the X-ray photoelectron spectra and calculation of electronic structure and shed lights on the abnormal thermal expansion. The stability of such compound and the origin of its magnetism are also discussed based on measured and calculated electronic structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Structural and Reactivity Effects of Secondary Metal Doping into Iron-Nitrogen-Carbon Catalysts for Oxygen Electroreduction

While improved activity was recently reported for bimetallic iron-metal-nitrogen-carbon (FeMNC) catalysts for the oxygen reduction reaction (ORR) in acid medium, the nature of active sites and interactions between the two metals are poorly understood. Here, FeSnNC and FeCoNC catalysts were structurally and catalytically compared to their parent FeNC and SnNC catalysts. While CO cryo-chemisorption revealed a twice lower site density of M-N x sites for FeSnNC and FeCoNC relative to FeNC and SnNC, the mass activity of both bimetallic catalysts is 50–100% higher than that of FeNC due to a larger turnover frequency in the bimetallic catalysts. Electron microscopy and X-ray absorption spectroscopy identified the coexistence of Fe-N x and Sn-N x or Co-N x sites, while no evidence was found for binuclear Fe-M-N x sites. 57 Fe Mössbauer spectroscopy revealed that the bimetallic catalysts feature a higher D 1 /D 2 ratio of the spectral signatures assigned to two distinct Fe-N x sites, relative to the FeNC parent catalyst. Furthermore, the addition of the secondary metal favored the formation of D 1 sites, associated with the higher turnover frequency.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A-dependence of weak nuclear structure functions

Effect of nuclear medium on the weak structure functions F{sub 2}{sup A}(x, Q{sup 2}) and F{sub 3}{sup A}(x, Q{sup 2}) have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, F{sub i}{sup A}/F{sub i}{sup proton} and F{sub i}{sup A}/F{sub i}{sup deuteron}(i=2,3, A={sup 12}C, {sup 16}O, CH and H{sub 2}O) are obtained.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Biased Tracers in Redshift Space in the EFT of Large-Scale Structure

The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a novel formalism that is able to accurately predict the clustering of large-scale structure (LSS) in the mildly non-linear regime. Here we provide the first computation of the power spectrum of biased tracers in redshift space at one loop order, and we make the associated code publicly available. We compare the multipoles $\ell=0,2$ of the redshift-space halo power spectrum, together with the real-space matter and halo power spectra, with data from numerical simulations at $z=0.67$. For the samples we compare to, which have a number density of $\bar n=3.8 \cdot 10^{-2}(h \ {\rm Mpc}^{-1})^3$ and $\bar n=3.9 \cdot 10^{-4}(h \ {\rm Mpc}^{-1})^3$, we find that the calculation at one-loop order matches numerical measurements to within a few percent up to $k\simeq 0.43 \ h \ {\rm Mpc}^{-1}$, a significant improvement with respect to former techniques. By performing the so-called IR-resummation, we find that the Baryon Acoustic Oscillation peak is accurately reproduced. Based on the results presented here, long-wavelength statistics that are routinely observed in LSS surveys can be finally computed in the EFTofLSS. This formalism thus is ready to start to be compared directly to observational data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗