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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

The dynamical oscillation and propulsion of magnetic fields in the convective zone of a star. I - General considerations

Observations of the sun show that the magnetic flux of the large activity complexes emerges in localized sites in brief bursts at intervals of many days or a few weeks. The quantity of flux arriving at the surface suggests that the mean aximuthal field of the sun in the lower convective zone is not less than 3000 G and may perhaps be considerably more. Such a field inhibits the convective transport of heat. Hence there is a cool shadow on the upper side of the field, and that cool shadow presses downward so hard as to suppress the magnetic buoyancy, forcing the field to remain in the lower convective zone. The accumulation of heat below the field forces intruding fingers of gas up through the field, forming thermal plumes extending up to the visible surface. It is suggested that the process is intermittent, providing a thermal relaxation oscillation with a period of the order of one week. The activity complexes observed at the surface are the consequence of these eruptions of fluid and entrained field from the lower convective zone.

Parker, E. N.↗
DOE OSTI2019

Application of time-of-flight secondary ion mass spectrometry to the detection of surface intermediates during the first cycle of atomic layer deposition (ALD) of platinum on silica surfaces

Atomic layer deposition (ALD) has become the method of choice for many applications requiring the controlled growth of thin films on solid surfaces. Yet, the use of metalorganic precursors typical in these depositions adds significant complexity to the chemistry involved. Unfortunately, it is difficult to obtain direct information about the surface species that participate in the reaction mechanisms of ALD. Here we illustrate the value of using time-of-flight secondary ion mass spectrometry (ToF-SIMS) for this purpose. A specific example is provided, a study of the first cycle of deposition of platinum using trimethyl(methylcyclopentadienyl)platinum (IV), or MeCpPt(CH 3 ) 3, on silicon oxide surfaces. In previous investigations of this process, we have determined that the low reactivity of the MeCpPt(CH 3 ) 3 precursor, which hinders fast deposition, can be partially overcome by gas-phase electron-impact activation. What has not been clear is what chemical species form on the solid surface as a result of such activation. Here we show that the MeCp ligand is quite stable and that it remains intact and coordinated to the Pt atoms upon adsorption on the surface. It was also established that some of the methyl groups may remain bound to the Pt center: the main species detected on the silicon oxide surfaces were MeCpPt and MeCpPt(CH 3 ). On the other hand, it appears that no Pt intermediates without MeCp ligands are formed during this initial adsorption. Finally, O 2 treatment of these surfaces at elevated temperature to complete the first ALD cycle leads to the complete removal of all the organic ligands: no evidence for MeCp or methyl groups is seen in the ToF-SIMS traces from the final samples.

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

Cathodic Protection Modeling for Hanford Underground Double-Shell Tank Farms

Hanford stores millions of gallons of radioactive and chemically hazardous waste from the production of weapon materials in tank farms consisting of underground carbon-steel storage tanks surrounded by reinforced concrete. Six of these Hanford tank farms use double-shell storage tanks (DSTs). The DST farms were constructed from 1968 to 1986 with a planned 40–50 year design life, so some are already operating beyond their initial life expectancy. Ultrasonic testing (UT) has indicated significant thinning on the bottom of the secondary (outer) liner of these tanks, believed to arise from groundwater intrusion driving concrete side corrosion. There is no direct access to the steel/concrete interface between the tank and the concrete pad, making it difficult to apply a chemical-based mitigation strategy or to conduct repairs, but cathodic protection (CP) is a possible method to inhibit further concrete-side corrosion. Hanford already uses CP to protect below grade steel piping within the tank farms and connected to the tanks, but this system was not designed to protect the tank bottoms. CP design must account for the structures surrounding the DSTs, including the steel reinforcing bars (rebar) within the concrete pad and vault, various process lines, and the existing CP system. In this study, finite element analysis (FEA) modeling was carried out to simulate CP protection of 1) a single tank and CP anode to develop options for modeling the rebar and to compare to a simpler circuit model and 2) the entire Hanford AN tank farm as a representative example consisting of seven tanks, associated piping, and both existing and new CP anodes. Both circuit and FEA models predict that significant protective current could be delivered to the bottoms of the tanks with the addition of tank-protection anodes below the depth of the tanks. Simulations with only the existing pipe-protection anodes active confirmed that only a very small current to the tank bottoms is predicted under present conditions. Multiple simplified representations of the dome and wall rebar were tested to reduce the computational complexity of the tank-farm simulations, resulting in modeling the rebar as edge elements with a prescribed effective circumference that matches the real rebar surface area. The geometry of the rebar is also simplified into horizontal hoops around the tank walls and radial rebar over the dome with increased effective circumference to retain the target surface area. This simplification was found to greatly reduce the complexity and solution time of the models without large changes in current distributions, especially to the tank bottom. A range of values were tested for model parameters such as soil and concrete resistivities and polarization resistance to investigate their impact on the current and electric potential distributions. Depending on the parameters used, FEA simulations predict some risk of overprotection, particularly on the piping system; since overprotection can also lead to surface damage associated with hydrogen gas generation at the interface (e.g. hydrogen embrittlement or damage to coatings), this needs to be considered when refining the design of the new CP system. Comparison between the FEA models and the circuit model representation demonstrated that the circuit model could not match the predicted FEA current distribution, even when using the exact same surface areas. This discrepancy appeared to be at least partly attributable to the impact of the relative positions of the tank components and anodes to each other and to the ground surface. The FEA model accounts for the relative positions since it solves the governing equations in three dimensions, but the circuit model cannot account for the positioning. In particular, the circuit model underpredicts the current to the tank bottom and overpredicts the current to the dome compared to FEA for the baseline geometry. The FEA models omitted the electrically isolated rebar in the bottom concrete slab. However, a circuit based stray current model estimated that only 2.1% of the total current through the slab would stray into the rebar, corresponding to ~0.21 A for a target current density of 2 mA/ft2 to the tank bottom. The estimated corrosion driven by this amount of stray current is predicted to yield a lifetime of >400 years for the minimum rebar diameter, assuming an acceptable cross-section area loss of 10%.

d'Entremont, Anna [Savannah River National Laborat↗
DOE OSTI2022

Challenges to Reliable Production Nitrogen Doping of Nb for SRF Accelerating Cavities

Over the last several years, alloying of the surface layer of niobium SRF cavities has been demonstrated to beneficially lower the superconducting RF surface resistance. Nitrogen, titanium, and oxygen have all been demonstrated as effective alloying agents, occupying interstitial sites in the niobium lattice within the RF penetration depth and even deeper, when allowed to thermally diffuse into the surface at appropriate temperatures. The use of nitrogen for this function has been often termed ’nitrogen doping’ and is being applied in the LCLS-II and LCLS-II HE projects. We report characterization studies of the distribution of nitrogen into the exposed niobium surface and how such distribution is affected by the quality of the vacuum furnace environment in which the doping takes place, and the complexity of nitride crystal growth on different grain orientations of surface niobium. Using state-of-the-art quantification methods by dynamic secondary ion mass spectrometry (SIMS) depth profiling in niobium, we identify several phenomena involving furnace-sourced contamination. We also highlight a potential issue with N₂ flow constraints from the flange ’caps’ used during heat treatments.

Reece, Charles↗
DOE OSTI2024

Characterizing Land-Atmosphere Interactions During the Afternoon-to-Evening Transition Using ARM SGP Observations

The land-atmosphere (LA) system consists of the soil, vegetation, and lowest layer of the atmosphere. The energy and water transport processes in this system contribute to the structure and the daily cycle of the atmospheric boundary layer (ABL), which is the layer between the land surface and the free troposphere that controls the exchange of momentum, energy, and water. The state of the ABL is the result of complex two-way interactions between local processes such as surface fluxes and entrainment at the ABL top as well as large-scale and mesoscale processes such as advection and subsidence.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1992

Hypersonic flows as related to the national aerospace plane

The study in the last 6 months has observed a clear evidence that the current two-equation models tend to under-predict flow separation and over-predict heat transfer rate near flow re-attachment regions. In hypersonic flow calculations, these model deficiencies appear to be even more pronounced. This is particularly true in the incapability of the model to predict the extent of the flow separation. Two major deficiencies of the current two-equation models in predicting complex hypersonic flows have been reported, i.e., under-prediction of flow separation and over-prediction of peak heat transfer rate. Two modifications to the k - epsilon model were reported and tested over a range of flows. Based on our limited study, the modified models have been found to give better agreements in both surface pressure and heat transfer predictions for several complex shock-wave boundary-layer interaction flows. However, in order to confirm our observation, more calculations will be performed in the future study covering a wider range of flows and conditions than reported here.

Kussoy, Marvin↗
DOE OSTI2020

Revealing and Elucidating ALD-Derived Control of Lithium Plating Microstructure

The practical implementation of Li metal batteries is hindered by difficulties in controlling the Li metal plating microstructure. While previous atomic layer deposition (ALD) studies have focused on directly coating Li metal with thin films for the passivation of the electrode–electrolyte interface, a different approach is adopted, situating the ALD film beneath Li metal and directly on the copper current collector. Here, a mechanistic explanation for this simple strategy of controlling the Li metal plating microstructure using TiO 2 grown on copper foil by ALD is presented. In contrast to previous studies where ALD-grown layers act as artificial interphases, this TiO 2 layer resides at the copper–Li metal interface, acting as a nucleation layer to improve the Li metal plating morphology. Upon lithiation of TiO 2 , a Li x TiO 2 complex forms; this alloy provides a lithiophilic surface layer that enables uniform and reversible Li plating. The reversibility of lithium deposition is evident from the champion cell (5 nm TiO 2 ), which displays an average Coulombic efficiency (CE) of 96% after 150 cycles at a moderate current density of 1 mA cm –2 . This simple approach provides the first account of the mechanism of ALD-derived Li nucleation control and suggests new possibilities for future ALD-synthesized nucleation layers.

25 ENERGY STORAGE↗
DOE OSTI2017

Catalytic Reaction Rates Controlled by Metal Oxidation State: C−H Bond Cleavage in Methane over Nickel‐Based Catalysts

Abstract The role of low concentrations of carbon complexes in hydrocarbon decomposition over transition metal surfaces has been a topic of much debate over the past decades. It is also a mystery as to whether or not electric fields can enhance hydrocarbon conversion in an electrochemical device at lower than normal reforming temperatures. To provide a “bottom‐up” fundamental insight, C−H bond cleavage in methane over Ni‐based catalysts was investigated. Our theoretical results show that the presence of carbon or carbide‐like species at the interface between the Ni cluster and its metal‐oxide support, as well as the application of an external positive electric field, can significantly increase the Ni oxidation state. Furthermore, the first C−H bond cleavage in methane is favored as the local oxidation state of Ni increases. Thus, the presence of a low concentration of carbon species, or the addition of a positive electric field will improve the hydrocarbon activation process.

Che, Fanglin↗
DOE OSTI2017

Catalytic Reaction Rates Controlled by Metal Oxidation State: C−H Bond Cleavage in Methane over Nickel‐Based Catalysts

Abstract The role of low concentrations of carbon complexes in hydrocarbon decomposition over transition metal surfaces has been a topic of much debate over the past decades. It is also a mystery as to whether or not electric fields can enhance hydrocarbon conversion in an electrochemical device at lower than normal reforming temperatures. To provide a “bottom‐up” fundamental insight, C−H bond cleavage in methane over Ni‐based catalysts was investigated. Our theoretical results show that the presence of carbon or carbide‐like species at the interface between the Ni cluster and its metal‐oxide support, as well as the application of an external positive electric field, can significantly increase the Ni oxidation state. Furthermore, the first C−H bond cleavage in methane is favored as the local oxidation state of Ni increases. Thus, the presence of a low concentration of carbon species, or the addition of a positive electric field will improve the hydrocarbon activation process.

Che, Fanglin↗
DOE OSTI2018

Multi-electrode Harmonized Kingdon Traps

Based on the analysis of the results of the study of various designs of multi-electrode harmonized Kingdon traps, we propose a new type of trap with two merged internal electrodes that has the ability to capture and accumulate ions formed inside. We also investigated the influence of inaccuracies in the manufacture of the electrodes on the field inside such trap. The four-electrode trap, which actually degenerates into a two-electrode device with traces of two other electrodes present at the ends of the internal electrodes (their splitting) has been found as the less sensitive to inaccuracies caused by manufacturing and cutting the ends of trap electrodes. We show that a mass spectrometer with a relatively high resolving power can be created on the basis of such a trap. The creation of the traps requires the manufacture of complex electrodes with demanded accuracy of their surfaces. This becomes possible with the advent of 3D printers. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Characteristics and mechanisms of hydrogen-induced quasi-cleavage fracture of lath martensitic steel

Here this study presents an in-depth characterization of the microstructures, crystallographic orientations, and dislocation characteristics beneath hydrogen-induced quasi-cleavage fracture features of an as-quenched, lath martensitic (α') 22MnB5 steel. The fracture surfaces of gaseous hydrogen-embrittled martensitic specimens were analyzed by a combination of multiple analytical tools: scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and transmission Kikuchi diffraction (TKD). The dominant fracture mode in the hydrogen-affected zones was quasi-cleavage fracture, which involved significant plasticity, evidenced by plastic zones near tear ridges and a high density of dislocations beneath the quasi-cleavage facets. The martensite constituent sizes, variant orientations, and boundaries influenced the quasi-cleavage surface morphologies. Fractography revealed the occurrence of {100} α' -type cleavage across martensitic laths, developing relatively “flat” quasi-cleavage surfaces, in addition to {110} α' -type cracking likely along lath and block boundaries, and fracture along non-cleavage planes. The likelihood of the formation of the relatively “flat” quasi-cleavage surfaces increased with increasing martensitic constituent sizes. Substantial dislocation bands formed on intersecting {112} α' slip planes within a martensite block below the hydrogen-induced cleavage fractures on {100} α' planes. River markings on the quasi-cleavage surfaces were found to originate from the complex, hierarchical lath martensitic microstructure. Steps and ridges on the quasi-cleavage facets generally linked with the various martensitic boundaries, suggesting that they were produced as a result of crack deviations at those boundaries. The fracture paths and martensite quasi-cleavage mechanisms are discussed in the context of the role of hydrogen and Cottrell cleavage model.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Shape evolution and growth mechanisms of 3D-printed nanowires

3D printing of nanowires using Focused Electron Beam Induced Deposition (FEBID) enables the direct-write fabrication of complex 3D objects on almost any substrate surface. The physical properties of such freestanding structures are determined by the dimensions of constituent nanowires. However, little knowledge is available about the exact shape of the nanowires, which is indispensable for calculations and simulations as well as for optimization in applications. In this study, we evaluate the thicknesses and widths of freestanding segments as a function of the inclination angles, primary electron energy, beam currents, and precursor flux. Furthermore, the cross-sectional shape, the cross-sectional area, and the evolution along the length of the wire are investigated. Basing on detailed scanning electron microscopy measurements and Monte Carlo/Finite Differences simulations, the effects that the growth parameters have on the segment growth are elucidated. Furthermore, the results shed light on the growth evolution of the structures and form the basis for future studies on the fabrication of high-precision, arbitrarily shaped nanowires.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Probing the initial stages of iron surface corrosion: Effect of O 2 and H 2 O on surface carbonation

Iron plays a vital role in natural processes such as water, mineral, iron, and nutrient cycles. Iron undergoes reduction-oxidation and catalytic reactions to produce various corrosion films depending on its chemical environment. Near ambient pressure X-ray photoelectron spectroscopy, polarized modulated infrared reflection absorption spectroscopy, and Auger electron spectroscopy were used to study the key reactants, from O 2 (g), H 2 O vapor, Na + and Cl – on the initial stages of iron surface corrosion. Here, with increasing the ratio of O 2 and H 2 O, surface hydrocarbons were shown to oxidize into carbonates, while the Cl – was found to migrate into the interface. The effect of each individual reactant was measured separately and water was shown to have a first order rate dependence on the carbonate growth at low pressures, with little dependence for O 2 . Near ambient pressures, both H 2 O and O 2 were found to increase the carbonate growth, which was estimated using the Langmuir isotherm model, yielding Gibbs energies between –9.8 to –8.5 kJ/mol. A mechanism is suggested to explain the oxidation is catalyzed by NaCl on iron surfaces and the adventitious hydrocarbons served as the source for surface carbonation. These findings have implications for understanding other surface catalytic and redox interface chemistry in complex environments.

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

Role of N-myristoylation in stability and subcellular localization of the CLPABP protein

Highlights: • N-myristoylation of the CLPABP protein was predicted to affect its stability. • N-myristoylation of CLPABP was not related to its mitochondrial localization. • Both PH domains of CLPABP may be necessary to colocalize with mitochondria. Cardiolipin and phosphatidic acid-binding protein (CLPABP) controls the stability of the mRNA harboring an AU-rich element (ARE) in the 3′ UTR with the help of the RNA stabilizer, human antigen R (HuR). Although CLPABP is localized on the mitochondrial surface as a large protein-RNA complex, its precise role is not yet known. Recently, CLPABP was identified as an N-myristoylated protein. Here, we demonstrate the effects of N-myristoylation on the functions of CLPABP. In the present study, compared to the wild-type protein that possessed the “MG” motif at the N-terminus for N-myristoylation, the mutant CLPABP protein that lacked N-myristoylation modification site was unstable. Furthermore, the expression of the G/A mutant of CLPABP, which lacked N-myristoylation site, induced morphological alterations in mitochondria. Because pleckstrin homology domain-deleted mutant, which was fused with the N-myristoylation site derived from intact CLPABP, could not colocalize with mitochondria, N-myristoylation of CLPABP was predicted to affect its stability onto the mitochondrial membrane rather than its subcellular localization.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Photoelectrocatalytic reduction of CO 2 to formate using immobilized molecular manganese catalysts on oxidized porous silicon

The reduction of carbon dioxide (CO 2 ) to formate using molecular catalysts immobilized on high surface area porous silicon is described. Manganese complexes of the type ( R bpy)Mn(CO) 3 Br (bpy = 2,2′-bipyridine) were prepared with silatrane groups on the bpy ligand for attachment to oxide-coated porous silicon (SiO x -porSi). SiO x -porSi wafers were formed by heating hydrogen-terminated p-type porous silicon wafers under air, and the manganese complexes were immobilized on SiO x -porSi by heating at 80°C. The resulting hybrid photoelectrodes are photoelectrocatalysts for CO 2 reduction in acetonitrile containing 2.0 M triethylamine and 2.0 M isopropanol, yielding formate with high selectivity (>96%) and current density (∼0.6 mA/cm 2 ), excellent reproducibility, and a photovoltage of 280 mV at −1.75 V (versus ferrocenium/ferrocene) under 1 sun illumination. Here, the applied potential is close to the equilibrium potential for CO 2 reduction to formate. This work presents rare examples of immobilized molecular catalysts for CO 2 reduction to formate and the first on semiconducting silicon.

13 HYDRO ENERGY↗
DOE OSTI2023

A sharp interface Lagrangian-Eulerian method for flexible-body fluid-structure interaction

This paper introduces a sharp-interface approach to simulating fluid-structure interaction (FSI) involving flexible bodies described by general nonlinear material models and across a broad range of mass density ratios. This new flexible-body immersed Lagrangian-Eulerian (ILE) scheme extends our prior work on integrating partitioned and immersed approaches to rigid-body FSI. Our numerical approach incorporates the geometrical and domain solution flexibility of the immersed boundary (IB) method with an accuracy comparable to body-fitted approaches that sharply resolve flows and stresses up to the fluid-structure interface. Unlike many IB methods, our ILE formulation uses distinct momentum equations for the fluid and solid subregions with a Dirichlet-Neumann coupling strategy that connects fluid and solid subproblems through simple interface conditions. As in earlier work, we use approximate Lagrange multiplier forces to treat the kinematic interface conditions along the fluid-structure interface. This penalty approach simplifies the linear solvers needed by our formulation by introducing two representations of the fluid-structure interface, one that moves with the fluid and another that moves with the structure, that are connected by stiff springs. This approach also enables the use of multi-rate time stepping, which allows us to use different time step sizes for the fluid and structure subproblems. Our fluid solver relies on an immersed interface method (IIM) for discrete surfaces to impose stress jump conditions along complex interfaces while enabling the use of fast structured-grid solvers for the incompressible Navier-Stokes equations. The dynamics of the volumetric structural mesh are determined using a standard finite element approach to large-deformation nonlinear elasticity via a nearly incompressible solid mechanics formulation. This formulation also readily accommodates compressible structures with a constant total volume, and it can handle fully compressible solid structures for cases in which at least part of the solid boundary does not contact the incompressible fluid. Selected grid convergence studies demonstrate second-order convergence in volume conservation and in the pointwise discrepancies between corresponding positions of the two interface representations as well as between first and second-order convergence in the structural displacements. The time stepping scheme is also demonstrated to yield second-order convergence. To assess and validate the robustness and accuracy of the new algorithm, comparisons are made with computational and experimental FSI benchmarks. Test cases include both smooth and sharp geometries in various flow conditions. Furthermore, we also demonstrate the capabilities of this methodology by applying it to model the transport and capture of a geometrically realistic, deformable blood clot in an inferior vena cava filter.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

High energy storage properties of (Ni1/3Nb2/3)4+ complex-ion modified (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 ceramics

Highlights: • BCZT-xNN ceramics showed single phase perovskite structure without an obvious second phase after adding NN, and exhibited both good temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz) stability. • The highest energy storage density can reach 0.66 J/cm{sup 3} and the energy efficiency is 88.1% was achieved in x = 0.3. • The environmental friendly (lead-free) BCZT-xNN ceramics are good candidate for application in energy storage devices. • This paper also developes a new method to obtain high energy storage density and efficiency of ceramic capacitor, which aims to adjust the T{sub c} of ceramics far below room temperature. - Abstract: In this study, paraelectric ceramics, (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90}){sub 1-x}(Ni{sub 1/3}Nb{sub 2/3}){sub x}O{sub 3,} abbreviated as BCZT-xNN (with x = 0.1, 0.2, 0.3, 0.4) were prepared via a solid-state reaction method. By introducing a B-site complex-ion, (Ni{sub 1/3}Nb{sub 2/3}){sup 4+}, the Curie temperature of the ceramic could be reduced to below room temperature. The effects of this B-site (Ni{sub 1/3}Nb{sub 2/3}){sup 4+} complex-ion substitution on the phase structure, surface microstructure as well as the dielectric, ferroelectric, and energy storage properties of the ceramic were systematically investigated. After adding NN, BCZT-xNN shows a single phase perovskite structure without evidence of a second phase . In addition, we observed high stability with respect to both temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz). Doping with NN produces slim polarization-electric field hysteresis loops and enhanced energy storage properties, while the efficiency decreases. When x = 0.3, the highest energy storage density reached 0.66 J/cm{sup 3} for a high electric field (20 kV/mm), and the respective energy efficiency was 88.1%. These properties indicate that the environmental friendly BCZT-xNN ceramics are promising candidates for commercial energy storage devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗