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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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Hybrid gels via bulk interfacial complexation of supramolecular polymers and polyelectrolytes

Hierarchical self-assembly leading to organized supramolecular structures across multiple length scales has been of great recent interest. Earlier work from our laboratory reported the complexation of peptide amphiphile (PA) supramolecular polymers with oppositely charged polyelectrolytes into a single solid membrane at a macroscopic interface. We report here the formation of bulk gels with many internal interfaces between the covalent and supramolecular polymer components formed by the rapid chaotic mixing of solutions, one containing negatively charged PA nanofibers and the other the positively charged biopolymer chitosan. We found that formation of a contact layer at the interface of the solutions locks the formation of hydrogels with lamellar microstructure. The nanofiber morphology of the supramolecular polymer is essential to this process since gels do not form when solutions of supramolecular assemblies form spherical micelles. Here, we found that rheological properties of the gels can be tuned by changing the relative amounts of each component. Furthermore, both positively and negatively charged proteins are easily encapsulated within the contact layer of the gel, which provides an interesting biomedical function for these systems.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Rare-earth leaching from Florida phosphate rock in wet-process phosphoric acid production

Phosphorite, or phosphate rock, is the most significant secondary rare-earth resource. It contains high amounts of phosphate-bearing minerals along with low contents of rare earth elements (REEs). In Florida, about 19 Mt of phosphate rock are mined annually and most are used to manufacture fertilizers using a wet process, in which sulfuric acid reacts with phosphates to produce phosphoric acid and phosphogypsum. In the wet process, REEs are also leached out into solution and eventually get lost in the leaching residue and phosphate fertilizer. Recovering REEs from Florida phosphate rock in the wet process will be beneficial to broadening rare-earth availability, improving the quality of phosphoric acid product and protecting the environment. Here, this study focuses on the influences of wet-process operating conditions on REE leaching efficiency. The results indicate that REE leaching efficiency increases with phosphoric acid addition in the initial pulp. At a temperature of 75 °C, a stoichiometric ratio of sulfuric acid (H2 SO4 ) to calcium oxide (CaO) of 1.05 and a weight ratio of liquid to solid of 3.5, REE leaching efficiency reached a relatively high value of 52.82 percent. The trends of REE leaching efficiency were similar to those for phosphoric acid (P2O5 ). Extensive tests on the leaching residue showed that during leaching, about 90 percent of the REEs were released from the phosphate rock but only 52.82 percent ended up in the leaching solution. This phenomenon can be attributed to two factors: (1) the effect of phosphate ions (PO43-) in the solution, which caused REE ions to form REE phosphates and be precipitated into the leaching residue, and (2) the influence of large amounts of anions such as sulfate (SO42-), dihydrogen phosphate (H2 PO4-) and hydrogen phosphate (HPO42-) anions as well as the polar molecule H3 PO4 , which surrounded the REE cations and formed an ion atmosphere that prevented the PO43- from contacting and combining with REE cations. Finally, interaction of these two opposite effects determined the REE distribution between leaching solution and residue.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Finding diverse ways to improve algebraic connectivity through multi-start optimization

The algebraic connectivity, also known as the Fiedler value, is a spectral measure of network connectivity that can be increased through edge addition. We present an algorithm for producing many diverse ways to add a fixed number of edges to a network to achieve a near optimal Fiedler value. Previous Fielder value optimization algorithms (i.e. the greedy algorithm) output only one solution. Obtaining a single solution is rarely good enough for real-world network redesign problems, as practical constraints (political, physical or financial) may prevent implementation. Our algorithm takes a multi-start optimization approach, adding a random initial edge and then applies a greedy heuristic to improve the Fiedler value. The random choice moves us to a new region of the search space, enabling discovery of diverse solutions. Additionally, we present a Determinantal Point Process framework for quantifying diversity. We then apply a Markov chain Monte Carlo technique to sift through the large number of output solutions and locate a smaller, more manageable collection of highly diverse solutions that can be presented to network redesign engineers. We demonstrate the effectiveness of our algorithm on real-world graphs with varied structures.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Upscaling of U(VI) Desorption and Transport from Decimeter-Scale Heterogeneity to Plume-Scale Modeling

Scientifically defensible predictions of field scale U(VI) transport in groundwater requires an understanding of key processes at multiple scales. These scales range from smaller than the sediment grain scale (less than 10 μm) to as large as the field scale which can extend over several kilometers. The key processes that need to be considered include both geochemical reactions in solution and at sediment surfaces as well as physical transport processes including advection, dispersion, and pore-scale diffusion. The research summarized in this report includes both experimental and modeling results in batch, column and tracer tests. The objectives of this research were to: (1) quantify the rates of U(VI) desorption from sediments acquired from a uranium contaminated aquifer in batch experiments;(2) quantify rates of U(VI) desorption in column experiments with variable chemical conditions, and(3) quantify nonreactive tracer and U(VI) transport in field tests.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Spectroscopic Online Monitoring: Using a Multi-Track Visible Spectrometer to Facilitate a Mass Balance Study in a Simulated TALSPEAK Process

Nuclear energy is a promising low-carbon energy candidate to meet the increased demand for green energy, where the integration of fuel recycling can have significant benefits for material usage and waste reduction. Utilizing in situ monitoring tools can provide ample opportunities to better control and safeguard nuclear material recycle processes while also offering knowledge and insight into real-time solution properties. The simultaneous measurement of analytical targets in multiple process locations can enable real-time mass balance and material accountancy calculations. This is demonstrated here with a mass balance study of Nd 3+ on countercurrent aqueous/organic metal extraction within a single centrifugal contactor. The Nd 3+ concentration was simultaneously monitored at the inlets and outlets of both aqueous and organic phases using a visible absorbance detector that allowed for the simultaneous measurement of up to six locations. The Nd 3+ concentration was calculated by using chemical data science algorithms, where model training sets were collected on a single track of the detector. The discussion includes addressing the challenges of using a model collected on a single track and applying it as a model across the other tracks on the detector. Each track of the detector corresponds to one measurement location on the contactor. The difference in the integrated moles of Nd 3+ between the inlet and outlet at the end of the experiment was near zero, indicating that the mass balance of this experiment was maintained. Overall, the online spectroscopic monitoring was able to follow changing solution conditions and accurately measure the concentration of Nd 3+ in different locations within the contactor system.

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

Simulation of macromolecule self-assembly in solution: A multiscale approach

One of the most common processes to produce polymer nanoparticles is to induce self-assembly by using the solvent-displacement method, in which the polymer is dissolved in a “good” solvent and the solution is then mixed with an “anti-solvent”. The polymer ability to self-assemble in solution is therefore determined by its structural and transport properties in solutions of the pure solvents and at the intermediate compositions. In this work, we focus on poly-ε-caprolactone (PCL) which is a biocompatible polymer that finds widespread application in the pharmaceutical and biomedical fields, performing simulation at three different scales using three different computational tools: full atomistic molecular dynamics (MD), population balance modeling (PBM) and computational fluid dynamics (CFD). Simulations consider PCL chains of different molecular weight in solution of pure acetone (good solvent), of pure water (anti-solvent) and their mixtures, and mixing at different rates and initial concentrations in a confined impinging jets mixer (CIJM). Our MD simulations reveal that the nano-structuring of one of the solvents in the mixture leads to an unexpected identical polymer structure irrespectively of the concentration of the two solvents. In particular, although in pure solvents the behavior of the polymer is, as expected, very different, at intermediate compositions, the PCL chain shows properties very similar to those found in pure acetone as a result of the clustering of the acetone molecules in the vicinity of the polymer chain. We derive an analytical expression to predict the polymer structural properties in solution at different solvent compositions and use it to formulate an aggregation kernel to describe the self-assembly in the CIJM via PBM and CFD. Simulations are eventually validated against experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The relative viscosity of NaNO 3 and NaNO 2 aqueous solutions

In aqueous solution, both nitrate and nitrite are planar, monovalent, and have the same elements but different sizes and charge densities. Comparing the viscosity of NaNO 2 and NaNO 3 aqueous solutions provides an opportunity to determine the relative importance of anion size versus strength of anion interaction with water. The viscosity of aqueous NaNO 2 and NaNO 3 were measured over a temperature and concentration range relevant to nuclear waste processing. The viscosity of NaNO 2 solutions was consistently larger than NaNO 3 under all conditions, even though nitrate is larger than nitrite. This was interpreted in terms of quantum mechanical charge field molecular dynamics calculations that indicate that nitrite forms more and stronger hydrogen bonds with water per oxygen atom than nitrate. Furthermore, these hydrogen bonds inhibit rotational motion required for fluid flow, thus increasing the nitrite solution viscosity relative to that of an equivalent nitrate solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (f{sub c}) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (f{sub CNTs}) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same f{sub CNTs}, the ternary BNNSs/CNTs/PVDF nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (f{sub CNTs} < f{sub c}) shows a 79.59% enhancement from 49 to 88 after the incorporation of 3 vol. % BNNSs. For the other CNTs/PVDF system with 8 vol. % CNTs (f{sub CNTs} > f{sub c}), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Gas Generation Testing of Crystalline Silicotitanate Ion Exchange Media

The Direct Feed Low-Activity Waste (DFLAW) process has been proposed to support early production of immobilized low-activity waste (LAW) at the Hanford site. As planned, Hanford tank waste would be sent to the Tank Side Cesium Removal (TSCR) system for solids removal (by filtration) and cesium removal (by ion exchange) during the initial phase of the DFLAW process. The resultant treated waste would be delivered to the LAW Vitrification Facility at the Hanford Tank Waste Treatment and Immobilization Plant (WTP) for immobilization. The ongoing technology maturation of TSCR system components is being conducted by Washington River Protection Solutions, LLC (WRPS). The ion exchange process in the TSCR system will use columns of crystalline silicotitanate (CST) to remove cesium from the LAW. This report describes gas generation testing of the crystalline silicotitanate ion exchange media that was conducted to strengthen the technical basis of the media for use in the TSCR system. Specifically, the described study will inform the safety basis of both the operation of the TSCR system and the interim storage condition of the TSCR ion exchange columns after loading. Previous data on gas generation of CST are limited to a handful of studies using CST or similar media under unrepresentative conditions and durations. The safety basis underlying operation and storage of the CST columns needs to consider the rate and extent of radiolytic flammable gas generation. No existing studies provide a comprehensive set of gas generation data for column operating and storage conditions representative of those expected for TSCR. To address the data gap, this study was conducted under the following conditions (each in duplicate): (1) CST in water at 25°C tested to 300 Mrad total dose, (2) wet CST (soaked in water, then free-drained) at 25°C tested to both 300 Mrad and 900 Mrad total dose, (3) dry CST (air-dried, free-flowing material equilibrated to laboratory conditions) at 25°C tested to both 300 Mrad and 900 Mrad total dose, (4) CST in 5.6M Na simulant at 25°C tested to 300 Mrad total dose, and (5) CST in 5.6M Na simulant with 1% (w/w) total organic carbon as Na 3 -HEDTA at 25°C and 70°C tested to 300 Mrad total dose. For each of the listed conditions, the generation of the following gas species was measured: hydrogen, oxygen, nitrous oxide, and methane. The test data was used to determine the amount of gas generated (total and on a per-component basis), gas generation rates normalized to the CST bed volume tested, and G-values for each gas species. The reported results illustrate that the CST-in-water condition bounds the gas generation rate (at 25°C) of all other conditions, but there is some variability in the hydrogen G-value, depending on the lot of CST tested and the amount of residual moisture present at the start of the test.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Gas Generation Testing of Crystalline Silicotitanate Ion Exchange Media

The Direct Feed Low-Activity Waste (DFLAW) process has been proposed to support early production of immobilized low-activity waste (LAW) at the Hanford site. As planned, Hanford tank waste would be sent to the Tank Side Cesium Removal (TSCR) system for solids removal (by filtration) and cesium removal (by ion exchange) during the initial phase of the DFLAW process. The resultant treated waste would be delivered to the LAW Vitrification Facility at the Hanford Tank Waste Treatment and Immobilization Plant (WTP) for immobilization. The ongoing technology maturation of TSCR system components is being conducted by Washington River Protection Solutions, LLC (WRPS). The ion exchange process in the TSCR system will use columns of crystalline silicotitanate (CST) to remove cesium from the LAW. This report describes gas generation testing of the crystalline silicotitanate ion exchange media that was conducted to strengthen the technical basis of the media for use in the TSCR system. Specifically, the described study will inform the safety basis of both the operation of the TSCR system and the interim storage condition of the TSCR ion exchange columns after loading. Previous data on gas generation of CST are limited to a handful of studies using CST or similar media under unrepresentative conditions and durations. The safety basis underlying operation and storage of the CST columns needs to consider the rate and extent of radiolytic flammable gas generation. No existing studies provide a comprehensive set of gas generation data for column operating and storage conditions representative of those expected for TSCR. To address the data gap, this study was conducted under the following conditions (each in duplicate): (1) CST in water at 25°C tested to 300 Mrad total dose, (2) wet CST (soaked in water, then free-drained) at 25°C tested to both 300 Mrad and 900 Mrad total dose, (3) dry CST (air-dried, free-flowing material equilibrated to laboratory conditions) at 25°C tested to both 300 Mrad and 900 Mrad total dose, (4) CST in 5.6M Na simulant at 25°C tested to 300 Mrad total dose, and (5) CST in 5.6M Na simulant with 1%(w/w) total organic carbon as Na3-HEDTA at 25°C and 70°C tested to 300 Mrad total dose. For each of the listed conditions, the generation of the following gas species was measured: hydrogen, oxygen, nitrous oxide, and methane. The test data was used to determine the amount of gas generated (total and on a per component basis), gas generation rates normalized to the CST bed volume tested, and G-values for each gas species. The reported results illustrate that the CST in water condition bounds the gas generation rate (at 25°C) of all other conditions, but there is some variability in the hydrogen G-value, depending on the lot of CST tested and the amount of residual moisture present at the start of the test.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Solute Redistribution During Aging in a Laser-Based Powder Bed Fusion-Produced Fe-18Ni-9Co-5Mo-Ti Maraging Steel

Solute distribution during the laser-based powder bed fusion of metals process is highly complex because of solidification. This study builds on a previous investigation of how solute heterogeneities across different scales influence phase distribution and aging physical phenomena in a Fe-18Ni-9Co-5Mo-Ti maraging steel (Santana et al. in Addit Manuf 104494, 2024). Previous work using energy-dispersive X-ray spectroscopy revealed heterogeneous Ni and Mo enrichment at intercellular regions. Using X-ray diffraction, 8 ± 3% retained austenite was quantified in as-built samples. Additionally, electron backscatter diffraction analysis exposed the location of retained austenite along cell boundaries. In this work, scanning transmission electron microscopy results revealed the presence of non-enriched retained austenite in the as-built condition. With increased aging temperature, Ni and Mo enrichment in austenite increased, especially at the austenite/martensite boundary. Solute diffusion was simulated in DICTRA Thermo-Calc® software to assess solute redistribution between the matrix and second phases and to comprehend whether elemental diffusion processes are interconnected. Three different scenarios were considered: (1) solute diffusion in the matrix; (2) diffusion with enriched austenite in the intercellular region; (3) diffusion with non-enriched austenite in the intercellular region. Results showed that Ni partitioning controls austenite growth and that boundary regions exhibit higher element enrichment than the core.

42 ENGINEERING↗
DOE OSTI2016

Development of Treatment Process for Radioactive Wastewater Generated from Molybdenum-99 Study - 16415

Molybdenum-99 (Mo-99) high acidic waste solution was securely stored at INER for numerous years. Until 2004, the procedures of waste solution draw-out and pressure-release were accompanied, along with construction of treatment facilities. In 2009, after simulated solution and small volume Mo-99 waste solution tests, the treatment procedure was determined. Then batch-scale treatment facilities were set up. The waste solution was preserved using the instrument, along with modification of some facilities simultaneously. Ultimately all of 12 tanks of Mo-99 inorganic waste solution stored in Building 014 were finished on July, 2012. And residential 5 tanks of those solution served in Building 015B were also completed on September, 2014. A practicable process has been developed for treating radioactive waste generated from Mo-99 study, and it can effectively remove radionuclides from a nitric acid solution. At first, after the waste was sucked from the bucket, the pH value was adjusted to about 10.0 through acid-alkali neutralization. Then, an adsorbent of natural zeolite powder was added to adsorb nuclides, and two adsorption columns filled with Cs-treat and Sr-treat adsorbents were used for removing nuclear species of Cs-137 and Sr-90. In this step, the nuclear species of Cs-137 and Sr-90 contained in the liquid waste are significantly reduced to a degree for manual operation allowable. Then, nitrate ion and mercury ion were removed through another procedure. As a result, the operations were safer and more efficient than other conventional methods. Additionally, the hazard of accidental leakage caused by corrosion of the bucket after long period of storage can be effectively prevented and potential pollution threats are also eliminated. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Transforming Public Housing with Deep Energy Retrofits

Open Market ESCO’s (OME) Transforming Public Housing through Deep Energy Retrofits project demonstrated new design and financing solutions for implementing deep energy retrofits (DERs) in occupied low-income multifamily housing. The Project performed an integrated project delivery process, including designing low-carbon retrofit solution packages, construction pricing, and financing. The Project developed a constructible and financeable DER scope for a 102-unit extremely low-income multifamily property in Boston. This Project demonstrated a replicable approach for streamlining and implementing DER projects in occupied housing, including real solutions for overcoming design complexities and cost barriers.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

The Role of Process-Directing Agents on Enamel Lesion Remineralization: Fluoride Boosters

The aim of this study was to investigate the effects of two process-directing agents (polyaspartic acid and osteopontin) used in a polymer-induced liquid-precursor (PILP) process on the remineralization of bacteria-induced enamel demineralization. Enamel demineralization lesions (depths of about 180–200 µm) were created and exposed to Streptococcus mutans, cultured with a 10% sucrose solution for 21 days, and remineralized using a PILP process (pH = 7.4, 14 days) with a calcium phosphate solution containing either polyaspartic acid or osteopontin in the presence or absence of fluoride (0.5 ppm). The specimens were examined under scanning electron microscopy. The fluoride was successfully incorporated into the PILP remineralization process for both polyaspartic acid and osteopontin. When the fluoride was added to the PILP remineralization solution, there was more uniform remineralization throughout the lesion than with either polyaspartic acid or osteopontin alone. However, in the absence of these process-directing agents, fluoride alone showed less remineralization with the formation of a predominantly surface-only layer. The PILP remineralization process relies on the ability of process-directing agents to stabilize calcium phosphate ions and holds promise for enamel lesion remineralization, and these agents, in the presence of fluoride, seem to play an important role as a booster or supplement in the continuation of remineralization by reducing the mineral gains at the surface layer.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Dynamic Instructions for Nuclear Power Plant Field Workers

Most tasks conducted at a nuclear power plant are guided by a procedure in one way or another. Some tasks must be conducted by strictly adhering to the prescribed steps, while other tasks use the procedures as a reference guide. Traditionally, the procedure process in the nuclear industry has been paper heavy. In recent years however, the nuclear industry has considered adopting more dynamic solutions to improve the efficiency of their work management process, advance human and system performance, as well as reduce the cost of handling paper copies of documentation. As a first step, many nuclear utilities in the U.S. deployed solutions that electronically route the documents through the review and approval processes and where the worker in the field uses an electronic copy of the instruction or procedure on a handheld device. These electronic copies are very similar to the format of the paper instruction but do have some additional capabilities to capture recorded input and notes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Corrosion Behavior of Nano-/Ultrafine-Grained Al-0.2 wt.% Sc Alloy Produced by Accumulative Roll Bonding (ARB)

The corrosion behavior of the Al-0.2 wt.% Sc alloy fabricated by the accumulative roll bonding (ARB) process in a 3.5 wt.% NaCl solution was studied using the electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The effect of the microstructural parameters, such as dislocation density, texture, grain boundary, and lattice strain, on the corrosion behavior was also investigated in this study. The results demonstrated that the ARB process can significantly improve the corrosion resistance and modify the corrosion potential to attain higher positive potentials. In addition, the pitting corrosion changed into the lateral spreading of the pits at the seventh and tenth cycles of the ARB process with average grain size of 410 and 370 nm, respectively. The change in the fraction of the high-angle grain boundary during the ARB process is the most important parameter regarding the variation in corrosion type. The average grain size of 410 nm in seventh cycle, as the optimum average grain size, demonstrated the highest corrosion resistance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Controlling Solvate Intermediate Growth for Phase-Pure Organic Lead Iodide Ruddlesden–Popper (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) n -1 Pb n I 3 n +1 Perovskite Thin Films

The growth of Ruddlesden-Popper perovskite thin films is complicated by the existence of multiple crystallization pathways available to precursors in solution. During conventional thin film growth processes, such as spin-coating or blade-coating, solvents can evaporate too quickly to clearly resolve different reaction intermediates and products that form during crystallization. Here, we resolve multiple reaction products and intermediates that form during Ruddlesden-Popper phase growth by studying drop-cast precursor solutions in situ through the evolution of X-ray diffraction, photoluminescence, and optical micrographs over long timescales in a thin film geometry. We found that methylammonium-rich solvate intermediates play a crucial role in directing the bulk optical properties of the films, and form simultaneously with smaller regions of Ruddlesden-Popper phases during growth. The microstructure and optical properties of these sub-phases were characterized during growth and after annealing, revealing that discrepancies between thin film and single-crystal optical properties originate from solvate intermediates. These lower band-gap solvate-mediated minority phases dominate the optical emission spectrum by means of rapid energy migration, and contribute to sub-band-gap electronic states in photovoltaic devices. Processing routes to yield thin films with optical properties similar to single crystals of Ruddlesden-Popper phases were developed by tuning the precursor stoichiometry and deposition kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗