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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Extended chondrule formation intervals in distinct physicochemical environments: Evidence from Al-Mg isotope systematics of CR chondrite chondrules with unaltered plagioclase

Al-Mg isotope systematics of twelve FeO-poor (type I) chondrules from CR chondrites Queen Alexandra Range 99177 and Meteorite Hills 00426 were investigated by secondary ion mass spectrometry (SIMS). Five chondrules with Mg#’s of 99.0 to 99.2 and Δ 17 O of -4.2‰ to -5.3‰ have resolvable excess 26 Mg. Their inferred ( 26 Al/ 27 Al) 0 values range from (3.5 ± 1.3) × 10 -6 to (6.0 ± 3.9) × 10 -6 . This corresponds to formation times of 2.2 (–0.5/+1.1) Myr to 2.8 (-0.3/+0.5) Myr after CAIs, using a canonical ( 26 Al/ 27 Al) 0 of 5.23 × 10 -5 , and assuming homogeneously distributed 26Al that yielded a uniform initial 26 Al/ 27 Al in the Solar System. Seven chondrules lack resolvable excess 26 Mg. They have lower Mg#’s (94.2 to 98.7) and generally higher Δ 17 O (-0.9‰ to -4.9‰) than chondrules with resolvable excess 26 Mg. Their inferred ( 26 Al/ 27 Al) 0 upper limits range from 1.3 × 10 -6 to 3.2 × 10 -6 , corresponding to formation >2.9 to >3.7 Myr after CAIs. Al-Mg isochrons depend critically on chondrule plagioclase, and several characteristics indicate the chondrule plagioclase is unaltered: (1) SIMS 27 Al/ 24 Mg depth profile patterns match those from anorthite standards, and SEM/EDS of chondrule SIMS pits show no foreign inclusions; (2) transmission electron microscopy (TEM) reveals no nanometer-scale micro-inclusions and no alteration due to thermal metamorphism; (3) oxygen isotopes of chondrule plagioclase match those of coexisting olivine and pyroxene, indicating a low extent of thermal metamorphism; and (4) electron microprobe data show chondrule plagioclase is anorthite-rich, with excess structural silica and high MgO, consistent with such plagioclase from other petrologic type 3.00-3.05 chondrites. We conclude that the resolvable ( 26 Al/ 27 Al) 0 variabilities among chondrules studied are robust, corresponding to a formation interval of at least 1.1 Myr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Slip delocalization and diffusion mediated carbide formation during fatigue of a nickel-base superalloy

Fatigue crack initiation at high temperatures occurs at microscopic fatigue shear bands that form near twin boundaries in polycrystalline nickel-base superalloys that contain minimal metallurgical defects. The associated dislocation sub-structure is complex and dependent on thermal and mechanical conditions. Here we show the formation of fine-scale carbide precipitates along these fatigue shear bands in a nickel-base superalloy during fatigue above 650 °C. The formation of carbide precipitates is studied using calculations of bulk and pipe diffusion. The contribution of pipe diffusion is observed to be critical in the formation of fine-scale carbides and occurs coincident with the delocalization of slip during fatigue.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The geospatial and economic viability of CO 2 storage in hydrocarbon depleted fractured shale formations

Hydrocarbon depleted fractured shale (HDFS) formations could be attractive for geologic carbon dioxide (CO 2 ) storage. Shale formations may be able to leverage existing infrastructure, have larger capacities, and be more secure than saline aquifers. We compared regional storage capacities and integrated CO 2 capture, transport, and storage systems that use HDFS with those that use saline aquifers in a region of the United States with extensive shale development that overlies prospective saline aquifers. We estimated HDFS storage capacities with a production-based method and costs by adapting methods developed for saline aquifers and found that HDFS formations in this region might be able to store with less cost an estimated ~14× more CO 2 on average than saline aquifers at the same location. The potential for smaller Areas of Review and less investment in infrastructure accounted for up to 84% of the difference in estimated storage costs. We implemented an engineering-economic geospatial optimization model to determine and compare the viability of storage capacity for these two storage resources. Across the state-specific and regional scenarios we investigated, our results for this region suggest that integrated CCS systems using HDFS could be more centralized, require less pipelines, prioritize different routes for trunklines, and be 6.4–6.8% ($5-10/tCO 2 ) cheaper than systems using saline aquifers. In conclusion, overall, CO 2 storage in HDFS could be technically and economically attractive and may lower barriers to large scale CO 2 storage if they can be permitted.

42 ENGINEERING↗
DOE OSTI2019

CO 2 storage in the Paluxy formation at the Kemper County CO 2 storage complex: Pore network properties and simulated reactive permeability evolution

The Paluxy formation is being considered as a prospective CO 2 reservoir at the Kemper County CO 2 Storage Complex. Herein, the pore and pore-throat size distributions and connectivity of the Paluxy formation is evaluated through analysis of 3D X-ray Computed Tomography images. In spite of resolution limitations that constrain the pore-throat sizes detectable by imaging, the permeability contributing pore-throats are successfully characterized through 3D imaging analysis. Image-obtained pore and pore-throat size distributions and pore connectivity are then utilized to construct pore network models and simulate permeability. After CO 2 is injected, it will dissolve into formation brine and create conditions favorable for dissolution of primary minerals and precipitation of secondary minerals. These reactions will alter the porosity and permeability of the system to varying degrees depending on the spatial location of reactions. In this research, the possible porosity-permeability evolution is simulated using pore network models considering mineral reactions occurring uniformly and non-uniformly throughout the network. For a given change in porosity, there is a large range of possible permeability outcomes. Depending on the extent and spatial location of mineral reactions, permeability may decrease by more than one order of magnitude as minerals precipitate. During dissolution, simulated permeability increases as much as 500%.

03 NATURAL GAS↗
DOE OSTI2022

Supercritical, liquid, and gas CO 2 reactive transport and carbonate formation in portland cement mortar

In this paper, we investigate carbonate formation and reactive transport rate in variably saturated portland cement mortars when high concentrations of gas, liquid, or supercritical CO 2 flow through their pore network. Xray computed tomography completed during CO 2 flow is used to quantify the microstructural evolution as the mortar carbonates. After in situ tests, higher resolution scans, thermogravimetric analysis, and desorption isotherm analysis are performed to further quantify microstructural changes. We found that at dry conditions supercritical CO 2 moves more rapidly through the pore space and precipitates more carbonates than liquid or gas CO 2 . However, at 50% degree of saturation (DOS) the CO 2 state did not affect the rate of transport in that each specimen exposed to a different CO 2 state carbonated within the first hour of CO 2 exposure. When the pore space is at 50 or 100% DOS, supercritical CO 2 did not react with hydration products more rapidly nor did it result in more carbonate formation during exposure compared to gas or liquid CO 2 . The amount of Ca(OH) 2 that contributes to CaCO 3 formation is correlated to the DOS. For the mortar composition analyzed, Ca(OH) 2 contributes to approximately 40% of the carbonates formed in the 50% DOS specimens and 15% in the 100% DOS specimens. In other words, as the amount of moisture in the pore space increases, phases other than Ca(OH) 2 contribute to more than 50% of the total CaCO 3 formed.

42 ENGINEERING↗
DOE OSTI2021

Superhydrophobic heat exchangers delay frost formation and enhance efficency of electric vehicle heat pumps

The number of electric vehicles has rapidly expanded as high-performance automotive lithium-ion batteries have become more affordable. However, the range of electric vehicles decreases in cold climates partly because of the additional thermal loads associated with cabin heating. One way to improve the efficiency of cabin heating is to replace resistive heating elements with an air-source heat pump system. However, to gain the full benefit of heat pumping, frost formation on the outdoor heat exchanger must be minimized. In this work, we modified the surface wettability of aluminum louvered-fin automotive heat pump evaporators and tested them under realistic operating conditions in a transcritical carbon dioxide (CO 2 ) heat pump. Each heat exchanger underwent several consecutive frosting and defrosting cycles to understand the cyclic performance of the system. The heat exchanger with a superhydrophobic outer surface was able to delay frost formation and maintain higher heat transfer rates when compared to heat exchangers with higher surface energies (hydrophilic). The delayed frost formation resulted in a system efficiency benefit in the first few frosting cycles but diminished in later cycles due to water retention and incomplete defrosting. However, for most automotive applications the superhydrophobic heat exchanger showed substantial benefits for normal driving trips. We report the scalable and optimized superhydrophobic heat exchangers developed here have the potential to increase the efficiency of automotive heat pumps and consequently increase the range and reduce energy consumption of electric vehicles.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Galinstan liquid metal breakup and droplet formation in a shock-induced cross-flow

Liquid metal breakup processes are important for understanding a variety of physical phenomena including metal powder formation, thermal spray coatings, fragmentation in explosive detonations and metalized propellant combustion. Since the breakup behaviors of liquid metals are not well studied, we experimentally investigate the roles of higher density and fast elastic surface oxide formation on breakup morphology and droplet characteristics. This work compares the column breakup of water with Galinstan, a room-temperature eutectic liquid metal alloy of gallium, indium and tin. A shock tube is used to generate a step change in convective velocity and back-lit imaging is used to classify morphologies for Weber numbers up to 250. Digital in-line holography (DIH) is then used to quantitatively capture droplet size, velocity and three-dimensional position information. Differences in geometry between canonical spherical drops and the liquid columns utilized in this paper are likely responsible for observations of earlier transition Weber numbers and uni-modal droplet volume distributions. Scaling laws indicate that Galinstan and water share similar droplet size-velocity trends and root-normal volume probability distributions. Furthermore, measurements indicate that Galinstan breakup occurs earlier in non-dimensional time and produces more non-spherical droplets due to fast oxide formation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Investigation of crossed-twin structure formation in magnesium and magnesium alloys

In this work, the effect of alloying addition on the propensity for twin-twin interactions to transform into crossed-twin structures in magnesium alloys is investigated. A full-field elasto-viscoplastic fast Fourier transform (EVP-FFT) framework combined with a discrete twin model and dislocation density-based hardening law for slip strengths is used to calculate the micromechanical fields in the crystalline matrix around the interacting twins. AZ31 and MgLi alloys are selected along with pure Mg to study the influence of plastic anisotropy in connection with alloying elements. These alloys were selected since their plastic anisotropy measure, which is defined as the ratio between the critical resolved shear stress for pyramidal $\langle$c +a$\rangle$ and basal $\langle$a$\rangle$ slip modes, spanned a wide range. To quantify the role of twin thicknesses, we probe a range of impinging twin thicknesses while fixing the recipient twin thickness. The analysis reveals that: (i) the local driving stress for crossed twin structure formation generated from the interaction of the two twins is lower in a low plastically anisotropic material, like a MgLi alloy, than a high plastically anisotropic material like pure Mg and (ii) the critical impinging twin thickness needed to form the crossed twin structure in pure Mg, AZ31 and MgLi alloys is ~0.5, ~0.75 and ~1.5 times the recipient twin thickness. We propose a relationship between the tendency for crossed twin structure formation and the experimentally observed higher ductility in MgLi alloys compared to pure Mg. Finally, one key implication of the findings is that crossed- twin structure formation can be hindered and the ductility of magnesium alloy thereby improved by properly choosing alloying elements that lower the slip strength for pyramidal $\langle$c + a$\rangle$ slip.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Intermetallic phase formation in Al-Si-Zr alloys during hot isostatic pressing revealed by experiments and molecular dynamics

Understanding phase transformations at alloy interfaces is critical for the design of advanced structural materials. Here, in this study, we investigate the formation mechanisms of the Al 2 SiZr intermetallic phase in the Al-Si-Zr system under hot isostatic pressing (HIP) using molecular dynamics (MD) simulations and thermodynamic analysis. A unique aspect of our approach in MD involves the replacement of a disordered Al 2 SiZr stoichiometry with an ordered phase at the Al-Zr interface once HIP results in the desired Al 2 SiZr stoichiometry, allowing us to compute the total energetic cost of transformation by accounting for both formation energies and diffusion barriers. Diffusion coefficients and activation energies, extracted across a range of temperatures, reveal that HIP substantially enhances atomic mobility, creating favorable stoichiometry for phase evolution. Our results show that Al 2 SiZr phase formation is kinetically unfavorable at lower temperatures but becomes feasible when the thermodynamic driving energy surpass a critical energy threshold.

Roy, Ankit [Pacific Northwest National Laboratory ↗
DOE OSTI2022

Crystallization pathways and interfacial drivers for the formation of hierarchical architectures

The development of structural hierarchy on various length scales during crystallization process is ubiquitous in biological systems and is also observed in synthetic nanomaterials. The driving forces for the formations of complex architectures range from local interfacial interactions, that modify interfacial speciation, local supersaturation, and nucleation barriers, to macroscopic interparticle forces. Although it is enticing to interpret the formation of hierarchical architectures as the assembly of independently nucleated building blocks, often crystallization pathways follow monomer-by-monomer addition with structural complexity arising from interfacial chemical coupling and strongly correlated fluctuation dynamics in the electric double layers. Here, the mechanism of the development of structural hierarchy through heterogeneous nucleation, coupled interfacial nucleation and assembly, and oriented attachment of independently nucleated particles is discussed. In this article, the emphasis is made on the discussion of the underlying interfacial forces and chemical coupling that drives crystallization pathways towards the formation of structural hierarchy.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Magnetic phase formation in irradiated austenitic alloys

Austenitic alloys are often observed to develop magnetic properties during irradiation, possibly associated with radiation-induced acceleration of the ferrite phase. Some of the parametric sensitivities of this phenomenon have been addressed using a series of alloys irradiated in the BOR-60 reactor at 593K. The rate of development of magnetic phase appears to be sensitive to alloy composition. To the first order, the largest sensitivities to accelerate ferrite formation, as explored in this experiment, are associated with silicon, carbon and manganese and chromium. Si, C, and Mn are thought to influence diffusion rates of point defects while Cr plays a prominent role in defining the chromium equivalent and therefore the amount of ferrite at equilibrium. Pre-irradiation cold working was found to accelerate ferrite formation, but it can play many roles including an effect on diffusion, but on the basis of these results the dominant role or roles of cold-work cannot be identified. Based on the data available, ferrite formation is most probably associated with diffusion.

Gussev, Maxim N↗
DOE OSTI2014

Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover, at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Theoretical assessment of bonaccordite formation in pressurized water reactors

The free energy of formation of bonaccordite (Ni 2 FeBO 5 ) as a function of temperature has been calculated using a technique that combines first principles calculations with experimental free energies of formation of aqueous species. The results suggest that bonaccordite formation from aqueous metal ions (Ni 2+ andFe 3+ ) and boric acid is thermodynamically favorable at elevated temperature and pH that have been predicted to exist at the CRUD-clad interface in deposits thicker than 60 μm.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Radiation-induced grain subdivision and bubble formation in U 3 Si 2 at LWR temperature

Here, U 3 Si 2 , an advanced fuel form proposed for light water reactors (LWR), has excellent thermal conductivity and a higher fissile element density. However, limited understanding of the radiation performance and fission gas behavior of U 3 Si 2 is available at LWR conditions. This study explores the irradiation behavior of U 3 Si 2 by 300 KeV Xe + ion beam bombardment combining with in-situ transmission electron microscopy (TEM) observation. The crystal structure of U 3 Si 2 is stable against radiation-induced amorphization at 350 °C even up to a very high dose of 64 displacements per atom (dpa). Grain subdivision of U 3 Si 2 occurs at a relatively low dose of 0.8 dpa and continues to above 48 dpa, leading to the formation of high-density nanoparticles. Nano-sized Xe gas bubbles prevail at a dose of 24 dpa, and Xe bubble coalescence was identified with an increase of irradiation dose. The volumetric swelling resulting from Xe gas bubble formation and coalescence was estimated with respect to radiation dose, and a 2.2% volumetric swelling was observed for U 3 Si 2 irradiated at 64 dpa considering fission gas only. Due to extremely high susceptibility to oxidation, the nano-sized U 3 Si 2 grains upon radiationinduced grain subdivision were oxidized to nanocrystalline UO 2 in a high vacuum chamber for TEM observation, eventually leading to the formation of UO 2 nanocrystallites up to 80 dpa.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Pectin methyltransferase QUASIMODO2 functions in the formation of seed coat mucilage in Arabidopsis

Pectin, cellulose, and hemicelluloses are major components of primary cell walls in plants. In addition to cell adhesion and expansion, pectin plays a central role in seed mucilage. Seed mucilage contains abundant pectic rhamnogalacturonan-I (RG-I) and lower amounts of homogalacturonan (HG), cellulose, and hemicelluloses. Previously, accumulated evidence has addressed the role of pectin RG-I in mucilage production and adherence. However, less is known about the function of pectin HG in seed coat mucilage formation. In this study, we analyzed a novel mutant, designated things fall apart2 (tfa2), which contains a mutation in HG methyltransferase QUASIMODO2 (QUA2). Etiolated tfa2 seedlings display short hypocotyls and adhesion defects similar to qua2 and tumorous shoot development2 (tsd2) alleles, and show seed mucilage defects. Here, the diminished uronic acid content and methylesterification degree of HG in mutant seed mucilage indicate the role of HG in the formation of seed mucilage. Cellulosic rays in mutant mucilage are collapsed. The epidermal cells of seed coat in tfa2 and tsd2 display deformed columellae and reduced radial wall thickness. Under polyethylene glycol treatment, seeds from these three mutant alleles exhibit reduced germination rates. Together, these data emphasize the requirement of pectic HG biosynthesis for the synthesis of seed mucilage, and the functions of different pectin domains together with cellulose in regulating its formation, expansion, and release.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Polysulfide reduction and Li 2 S phase formation in the presence of lithium metal and solid electrolyte interphase layer

Lithium sulfur battery is an attractive next generation technology that can meet many demands of modern society. Unfortunately, the lithium sulfur battery faces unique issues related to the polysulfide shuttle effect, that is due to reduction products dissolving in the electrolyte and their subsequent reduction on the lithium metal electrode. This adds further problems to the already challenging needs of understanding and engineering a solid electrolyte interphase (SEI) layer with desired properties. One of the most important SEI properties is its passivation of lithium metal which is critically important to the overall battery performance. Passivation is difficult to measure experimentally without the influence of many factors. This study reports an investigation of the reduction of the intermediate Li 2 S 8 over lithium already passivated with Li 2 O, Li 2 CO 3 , LiOH, LiF and Li 2 S along with exploration of Li 2 S 8 reduction over pristine lithium nanoclusters using first principles computational models. Significant formation of Li 2 S phase nucleation is found to stabilize the reduction products of the Li 2 S 8 . Here, the formation of Li 2 S is explored in-depth with lithium nanocluster-based models determining a 2 V potential increase for the reduction of polysulfides due to the formation of Li 2 S. This investigation demonstrates passivation effects of important SEI components including Li 2 S.

25 ENERGY STORAGE↗
DOE OSTI2013

Controlled synthesis and formation mechanism of monodispersive lanthanum vanadate nanowires with monoclinic structure

Monodisperse LaVO{sub 4} nanowires with relatively high aspect ratio larger than 50 have been prepared by a one-step solvothermal synthesis. This method provides a simple, inexpensive, controllable and reproducible process to produce LaVO{sub 4} nanowires with an average diameter of 15 nm and a high aspect ratio. The as-synthesized products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fast Fourier transform spectroscopy (FFT), indicative of a well-crystalline monoclinic structure and ascendant nanowire-morphology. The formation mechanism is suggested that oriented attachment plays a vital role in the growth of LaVO{sub 4} nanowires, which recommends a favorable route to fabricate similar morphological and structural nanometer materials. - Graphical abstract: The formation of LaVO{sub 4} nanowires is attributed to oriented attachment, a combination of nanocrystallites through their suitable surface planes, that is, with the same crystallographic orientations of [−120]. Highlights: ► Monodisperse LaVO{sub 4} nanowires with high aspect ratio have been prepared solvothermally without any templates. ► The morphology and structure of LaVO{sub 4} nanowires were characterized by XRD, SEM, TEM techniques. ► The formation mechanism of LaVO{sub 4} nanowires is suggested that oriented attachment plays a vital role.

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

Control of Y₂O₃ phase and its nanostructure formation through a very high energy mechanical milling

The formation behavior of Y₂O₃ ceramic particles was studied by employing a very high energy ball milling (milling energy: ~165 kJ/g·hit, milling speed: 1000 rpm). Both the XRD and HRTEM studies revealed that the high impact strain energy generated during the milling caused a drastic phase transition from the original C-type cubic (space group Ia3, a=10.58 Å) to the metastable B-type monoclinic (space group C2/m, a=13.89 Å), finally followed by a partial solid-state amorphization. The cubic phase was difficult to be reduced down to smaller than 10 nm, while the monoclinic phase was stabilized at sizes smaller than 10 nm with a mean crystallite size of 7.57 nm. Consequently, the existence of Y₂O₃ at a nanoscale smaller than 10 nm is possible by forming metastable monoclinic crystals, which are strain-induced. - Graphical abstract: The fig shows the solid-state phase formation of Y₂O₃ by very high energy input into the particles during milling: ordered body-centered cubic phase (space group Ia3, a=10.58 Å) nanocrystalline monoclinic phase (space group C2/m, a=13.89 Å) disordered monoclinic phase partial amorphous phase. The formation of Y₂O₃ smaller than 10 nm was strongly dependent on whether the phase transition from cubic to monoclinic occurred. Highlights: • This paper analyses very high energy milling behavior of coarse Y₂O₃ particles. • A drastic phase transition from cubic to monoclinic occurred with a partial amorphization. • An existence of Y₂O₃ smaller than 10 nm is possible by forming strain-induced monoclinic crystals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗