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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Explicit expressions of self-diffusion coefficient, shear viscosity, and the Stokes-Einstein relation for binary mixtures of Lennard-Jones liquids

Explicit expressions of the self-diffusion coefficient, D{sub i}, and shear viscosity, η{sub sv}, are presented for Lennard-Jones (LJ) binary mixtures in the liquid states along the saturated vapor line. The variables necessary for the expressions were derived from dimensional analysis of the properties: atomic mass, number density, packing fraction, temperature, and the size and energy parameters used in the LJ potential. The unknown dependence of the properties on each variable was determined by molecular dynamics (MD) calculations for an equimolar mixture of Ar and Kr at the temperature of 140 K and density of 1676 kg m{sup −3}. The scaling equations obtained by multiplying all the single-variable dependences can well express D{sub i} and η{sub sv} evaluated by the MD simulation for a whole range of compositions and temperatures without any significant coupling between the variables. The equation for D{sub i} can also explain the dual atomic-mass dependence, i.e., the average-mass and the individual-mass dependence; the latter accounts for the “isotope effect” on D{sub i}. The Stokes-Einstein (SE) relation obtained from these equations is fully consistent with the SE relation for pure LJ liquids and that for infinitely dilute solutions. The main differences from the original SE relation are the presence of dependence on the individual mass and on the individual energy parameter. In addition, the packing-fraction dependence turned out to bridge another gap between the present and original SE relations as well as unifying the SE relation between pure liquids and infinitely dilute solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Ionic Liquid and Silica Sol-Gel Composite Materials Doped with N,N,N ',N '-tetra(n-octyl)diglycolamide for Extraction of La3+ and Ba2+

Sol-gel processed silica materials which incorporated ionic liquids and tetraoctyldiglycolamide (TODGA) were prepared and used for extraction of La3+ and Ba2+ from aqueous solution. Imidazolium-based ionic liquids, 1-alkyl-3-methylimidazolium bis(trifluoromethane)sulfonimide ([Cnmim][NTf2]) were entrapped in the monolithic composite sorbents. Extraction efficiency was found to be dependent upon both the volume of IL used in the silica matrix, and the alkyl chain length of the IL cation. The silica composite sorbent containing [C8mim][NTf2] exhibited the best extraction efficiency for La3+ and the best separation factor for La3+ / Ba 2+. The results were analyzed by both Langmuir and Freundlich adsorption isotherm models, and the Freundlich model was found to give better fit.

36 MATERIALS SCIENCE↗
NASA NTRS1992

A numerical model for coupling between atomization and spray dynamics in liquid rocket thrust chambers

This paper describes a novel method of coupling the atomization and spray combustion processes encountered in coaxial injection elements of liquid rocket engine thrust chambers. This method is based on the Jet-Embedding technique in which the liquid jet core equations and the gas phase equations are solved separately. The liquid and gas phase solutions, however, are coupled through the boundary conditions at the interface between the phases. The computational grid for the gas phase calculations are adapted to the shape of the liquid jet core. The axial variation of droplet sizes are calculated using a stability analysis appropriate for the atomization regime of liquid jet breakup. The predictions of this method have been validated with experimental data on low speed water jets. Using this method, calculations are performed for the SSME fuel preburner single injector flow field. The results obtained are in good agreement with the predictions of the volume-of-fluid method.

Giridharan, M. G.↗
DOE OSTI2013

Flow of colloid particle solution past macroscopic bodies and drag crisis

The motion of colloid particles in a viscous fluid flow is considered. Small sizes of colloid particles as compared to the characteristic scale of the flow make it possible to calculate their velocity relative to the liquid. If the density of a colloid particle is higher than the density of the liquid, the flow splits into regions in which the velocity of colloid particles coincides with the velocity of the liquid and regions of flow stagnation in which the colloid velocity is higher than the velocity of the fluid. This effect is used to explain qualitatively the decrease in the drag to the flows past macroscopic bodies and flows in pipes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Complexation Enhancement Drives Water-to-Oil Ion Transport: A Simulation Study

We address the structures and energetics of ion solvation in aqueous and organic solutions to understand liquid-liquid ion transport. Atomistic molecular dynamics (MD) simulations with polarizable force field are performed to study the coordination transformations driving lanthanide (Ln(III)) and nitrate ion transport between aqueous and an alkylamide-oil solution. An enhancement of the coordination behavior in the organic phase is achieved in contrast with the aqueous solution. In particular, the coordination number of Ce3+ increases from 8.9 in the aqueous to 9.9 in the organic solutions (from 8 in the aqueous to 8.8 in the organic systems for Yb3+). Moreover, the local coordination environ ment changes dramatically. Potential of mean force calculations show that the Ln(III)-ligand coordination interaction strengths follow the order of Ln(III-)nitrate> Ln(III)-water>Ln(III)-DMDBTDMA. They increase 2-fold in the lipophilic environment in comparison to the aqueous phase, and we attribute this to the shedding of the outer solvation shell. Our findings highlight the importance of outer sphere interactions on the competitive solvation energetics that cause ions to migrate between immiscible phases; an essential ingredient for advancing important applications such as rare earth metal separations. Some open questions in simulating the coordination behavior of heavy metals are also addressed.

Qiao, Baofu↗
DOE OSTI2026

A new water-based scintillator for efficient Cherenkov and scintillation separation

Neutrinos offer a unique window into the world around us, allowing us to probe otherwise unreachable regions like the interior of stars and the depths of the earth, as well as potentially offering a mechanism for monitoring nuclear activity. Both pure-water and organic liquid scintillators have been used as the detection medium of large-scale neutrino detectors. Organic liquid scintillators offer higher sensitivity at lower energies, which is desirable for many applications, but detection of the Cherenkov radiation required for directional sensitivity is very difficult. A possible solution is to use water-based liquid scintillators (WbLSs), where some fraction of the water is replaced with a micellar solution of the liquid scintillator. This can enhance the detection sensitivity beyond that of pure water, without significantly affecting the ability to leverage the topological Cherenkov signature. Very specific scintillation properties are required to achieve this goal: the scintillation decay time should be significantly slower than that of the Cherenkov emission, so timing-based discrimination of Cherenkov light from scintillation can be applied. At the same time, the light yield should be high enough to enhance the overall sensitivity of the detector, but without losing too much of the Cherenkov light. In this study, we report a new water-based liquid scintillation cocktail based on a 9-methylcarbazole fluorescent dye and a linear alkylbenzene solvent. Here, the proposed composition offers 13.8 ns scintillation decay time and 368 nm emission that matches the desired properties.

Wolszczak, Weronika W. [Lawrence Berkeley National↗
DOE OSTI2019

An Adaptable Device for Scalable Electrospinning of Low- and High-Viscosity Solutions

This paper summarizes the design and construction of an adaptable electrospinner capable of spinning fluids over a large range of viscosities. The design accommodates needless electrospinning technologies and enables researchers to explore a large range of testing parameters. Modular parts can be exchanged for alternative versions that adapt to the research question at hand. A rotating drum electrode immersed halfway into a solution bath provides the liquid film surface from which electrospinning occurs. We tested and assessed several electrode designs and their electrospinning performance at higher (<500 poise) viscosities. Relative humidity was found to affect the onset of electrospinning of highly viscous solutions. We demonstrate robust device performance at applied voltage up to 90 kV between the electrospinning electrode and the collector. Design and fabrication aspects are discussed in practical terms, with the intent of making this device reproducible in an academic student machine shop.

McCarty, Ryan J. (ORCID:0000000224178917)↗
DOE OSTI2011

Liquid-phase and vapor-phase dehydration of organic/water solutions

Processes for dehydrating an organic/water solution by pervaporation or vapor separation using fluorinated membranes. The processes are particularly useful for treating mixtures containing light organic components, such as ethanol, isopropanol or acetic acid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2019

Electrochemical, Polarization, and Crevice Corrosion Testing of Inconel X750: A Supplement to the Environmental Control and Life Support System Sustaining Metal Materials Compatibility Study

In previous studies, electrochemical test results were experimentally acquired and then presented for several noble alloys in two specific solutions representative of waste liquids generated or present within the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). Subsequently, another metal candidate, Inconel X750, has been submitted and was subjected to the same test routines in the same solutions and evaluated with the same statistical/analytical methodologies as those utilized in the earlier studies. Previous studies included three titanium grades, (Commercially Pure, 6Al-4V alloy, and 6Al-4V Low Interstitial alloy), two nickel-chromium alloys (Inconel® 625 and Hastelloy® C276), one high tier stainless steel (Cronidur® 30), and a nickel-titanium alloy (Nitinol 60). Thus far, all candidate alloys have exhibited excellent corrosion protection and galvanic compatibility attributes and have been deemed qualified materials for application within the ECLSS facility. Inconel X750 now joins that group. The titanium alloys gave the best results of all the metal candidates by demonstrating superior nobility and galvanic protection properties. It is worth noting that the corrosion performance properties for the three titanium alloys were essentially indistinguishable. As such and for expediency, this study and all future evaluations will refer only to the comparative properties already documented for Titanium 6Al-4V as this alloy is representative of all three alloys and considered to be more mainstream. Now the measured corrosion properties for Inconel X750 were very similar to those determined previously for Inconel 625 and Hastelloy C276 which were also determined to be very high performers. For the current effort, the results have clearly shown that Inconel X750 possesses exceptional anti-corrosion attributes comparable to metals in the highest tier of the galvanic series. Overall, one can conclude that Inconel X750 is quite noble, highly corrosion resistant and galvanically compatible with the other metal groups from both an electrochemical perspective and a long-term exposure scenario. This was clearly demonstrated after utilizing the same techniques as those applied in previous studies which included linear, Tafel and cyclic polarization, galvanic coupling with each of the other metal candidates, and pitting/crevicing assessments after one full year of immersion in the subject test solutions. Attributes defining the nobility and anti-corrosion capabilities for X750 appear to be on par with all the other candidates thus far and this alloy can now be classified as ‘excellent’ exhibiting very high resistance toward general, localized, and galvanic corrosion in the subject test media.

Lee, R. E.↗
DOE OSTI2017

Electronic structure of aqueous solutions: Bridging the gap between theory and experiments

Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. Here, we propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1986

A search for the prewetting line

This paper describes efforts to locate the prewetting line in a binary liquid system (isopropanol-perfluoromethylcyclohexane) at the vapor-liquid interface. Tight upper bounds were placed on the temperature separation (0.2 K) between the prewetting line and the line of bulk liquid phase separation. The prewetting line in systems at equilibrium was not detected. Experimental signatures indicative of the prewetting line occurred only in nonequilibrium situations. Several theories predict that the adsorption of one of the components (the fluorocarbon, in this case) at the liquid-vapor interface should increase abruptly, at a temperature sightly above the temperature at which the mixture separates into two liquid phases. A regular solution calculation indicates that this prewetting line should have been easily detectable with the instruments used in this experiment. Significant features of the experiment are: (1) low-gradient thermostatting, (2) in situ stirring, (3) precision ellipsometry from the vapor-liquid interface, (4) high resolution differential index of refraction measurements using a novel cell design, and (5) computer control.

Schmidt, J. W.↗
NASA NTRS1986

Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts

Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

Su, Ching-Hua↗
DOE OSTI2014

Effect of gas velocity on the weakly nonlinear instability of a planar viscous sheet

A weakly nonlinear spatial instability of a two-dimensional planar viscous sheet for sinuous disturbances in a co-flowing inviscid gas stream is investigated theoretically, with an emphasis on the effect of the surrounding gas velocity. The solutions of the second-order interface disturbances are derived and the wave deformation has been computed. The results indicate that the second-order surface disturbance of the fundamental sinuous mode is varicose, which causes the thinning and the subsequent breakup of the liquid sheet. The nonlinear behaviors of the planar sheet are quite sensitive to variations in gas-to-liquid velocity ratio. The deviation of the velocity ratio from the value of unity leads to a larger growth rate, a larger second-order initial amplitude, and a shorter breakup length, and therefore enhances the instability. The growth rates predicted by the present nonlinear analysis according to the shortest breakup length are generally smaller than the linear predictions and can better conform to the experimental measures of Barreras et al. [“Linear instability analysis of the viscous longitudinal perturbation on an air-blasted liquid sheets,” Atomization Sprays 11, 139 (2001)]. Furthermore, the wave deformations of the most unstable disturbances are presented. The nonlinear instability of the planar sheet for a fixed velocity difference is performed. An equal increase of the gas and liquid velocity reduces the spatial growth rate and increases the breakup length, but generally has no influences on the second-order initial amplitude and the wavelength of the disturbance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Low Temperature Reduction of Alumina Using Fluorine Containing Ionic Liquids

The major objective of the project is to establish the feasibility of using specific ionic liquids capable of sustaining aluminum electrolysis near room temperature at laboratory and batch recirculation scales. It will explore new technologies for aluminum and other valuable metal extraction and process methods. The new technology will overcome many of the limitations associated with high temperatures processes such as high energy consumption and corrosion attack. Furthermore, ionic liquids are non-toxic and could be recycled after purification, thus minimizing extraction reagent losses and environmental pollutant emissions. Ionic liquids are mixture of inorganic and organic salts which are liquid at room temperature and have wide operational temperature range. During the last several years, they were emerging as novel electrolytes for extracting and refining of aluminum metals and/or alloys, which are otherwise impossible using aqueous media. The superior high temperature characteristics and high solvating capabilities of ionic liquids provide a unique solution to high temperature organic solvent problems associated with device internal pressure build-up, corrosion, and thermal stability. However their applications have not yet been fully implemented due to the insufficient understanding of the electrochemical mechanisms involved in processing of aluminum with ionic liquids. Laboratory aluminum electrodeposition in ionic liquids has been investigated in chloride and bis (trifluoromethylsulfonyl) imide based ionic liquids. The electrowinning process yielded current density in the range of 200-500 A/m 2 , and current efficiency of about 90%. The results indicated that high purity aluminum (>99.99%) can be obtained as cathodic deposits. Cyclic voltammetry and chronoamperometry studies have shown that initial stages of aluminum electrodeposition in ionic liquid electrolyte at 30°C was found to be quasi-reversible, with the charge transfer coefficient α = 0.40. Nucleation phenomena involved in aluminum deposition on copper in AlCl 3 -BMIMCl electrolyte was found to be instantaneous followed by diffusion controlled three-dimensional growth of nuclei. Diffusion coefficient (D o ) of the electroactive species Al 2 Cl 7 ¯ ion was in the range from 6.5 to 3.9x10 -7 cm 2 ∙s -1 at a temperature of 30°C. Relatively little research efforts have been made toward the fundamental understanding and modeling of the species transport and transformation information involved in ionic liquid mixtures, which eventually could lead to quantification of electrochemical properties. Except that experimental work in this aspect usually is time consuming and expensive, certain characteristics of ionic liquids also made barriers for such analyses. Low vapor pressure and high viscosity make them not suitable for atomic absorption spectroscopic measurement. In addition, aluminum electrodeposition in ionic liquid electrolytes are considered to be governed by multi-component mass, heat and charge transport in laminar and turbulent flows that are often multi-phase due to the gas evolution at the electrodes. The kinetics of the electrochemical reactions is in general complex. Furthermore, the mass transfer boundary layer is about one order of magnitude smaller than the thermal and hydrodynamic boundary layer (ReL≈10,000). Other phenomena that frequently occur are side reactions and temperature or concentration driven natural convection. As a result of this complexity, quantitative knowledge of the local parameters (current densities, ion concentrations, electrical potential, temperature, etc.) is very difficult to obtain. This situation is a serious obstacle for improving the quality of products, efficiency of manufacturing and energy consumption. The gap between laboratory/batch scale processing with global process control and nanoscale deposit surface and materials specifications needs to be bridged. A breakthrough can only be realized if on each scale the occurring phenomena are understood and quantified. Multiscale numerical modeling nevertheless can help to bridge this gap. In conjunction with various scale experimental efforts, this project was aim to construct the basis for a strategy for innovation, by developing a generally applicable modeling methodology for understanding and controlling the electrochemical processes of aluminum electrodeposition in ionic liquids with the unifying characteristic that they are based on charge-driven mass transfer. The approaches developed in this project will not only be essential for the mass production of aluminum on any pilot scale or industrial level production processes, leading to the development of a new aluminum production technology, but also bring significant benefits to the society in terms of saving energy, reducing pollutants emission and recovering valuable metals.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Insights into determining pore size properties of ultrafiltration membranes

The selectivity of porous membranes is often characterized using solute rejection tests, where membranes are challenged with dilute aqueous solutions of neutral solutes at operating conditions that minimize concentration polarization and fouling. In single solute tests, a membrane is challenged with one molecular weight (MW) solute at a time from low to high MW. Since single solute methods are time-intensive, mixed solute tests have become more common, where a mixture of several MW solutes challenges a membrane at once. However, the presence of large solutes in a mixture increases the rejection of smaller solutes. Furthermore, there are no universally accepted operating conditions or standard methods used by membrane manufacturers or researchers for the experiments, leading to difficulty in pore size and pore characteristic comparisons. In this paper, commercial ultrafiltration membranes were challenged with single and mixed solute polyethylene glycol (PEG) and dextran aqueous solutions. First, rejection values determined using total organic carbon (TOC) and high-performance liquid chromatography (HPLC) from single solute filtration experiments are compared. Differences in rejection curves obtained by the two techniques are attributed to solute polydispersity. Mixed solute filtration experiments with binary mixtures of solutes showcased co-solute interactions, which increase with both the size and weight percent of large solute in the mixture. Mixed solute filtration experiments at varying operating conditions (i.e., stir speed and flux) were conducted to determine operating conditions that mitigate co-solute interactions. Stir speed had a minimal effect on co-solute interactions. In contrast, low flux conditions can help minimize co-solute interactions, leading to pore size distributions that closely resemble results observed in single solute filtration using narrowly dispersed solutes. Additionally, at low flux conditions, the predicted membrane pore size distributions utilizing mixed solute experiments with PEG and dextran were similar.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Gas Retention and Release from Hanford Site Sludge Waste Tanks

Radioactive wastes from nuclear fuel processing are stored in large underground storage tanks at the Hanford Site. Solid wastes can be divided into saltcake (mostly precipitated soluble sodium nitrate and nitrite salts with some interstitial liquid consisting of concentrated salt solutions) and sludge (mostly low solubility aluminum and iron compounds with relatively dilute interstitial liquid). Waste generates hydrogen through the radiolysis of water and organic compounds, radio-thermolytic decomposition of organic compounds, and corrosion of a tank’s carbon steel walls. Nonflammable gases, such as nitrous oxide and nitrogen, are also produced. Additional flammable gases (e.g., ammonia and methane) are generated by chemical reactions between various degradation products of organic chemicals present in the tanks.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗