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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Effect of Solvent Quality on Structure and Dynamics of Lignin in Solution

The conversion of lignin into useful chemicals and monomers requires that different linkages connecting monomers are exposed to the catalytic sites. As most conversion processes are expected to occur in the liquid phase, it is important to understand the structure and dynamics of lignin in solution. Here, we have examined the structure and dynamics of hardwood- and softwood-derived lignin model compounds with 61 monomers in methanol/water solution.

09 BIOMASS FUELS↗
DOE OSTI2022

Prediction of local concentration fields in porous media with chemical reaction using a multi scale convolutional neural network

The study of solute transport in porous media is of interest in many chemical engineering systems. Some example applications include packed bed catalytic reactors, filtration devices, and batteries. The pore scale modeling of these systems is time consuming and may require large computing resources, for this reason computational fluid dynamics (CFD) simulations are not practical if a large number of simulations is required, like in multiscale modeling, where a model at a large scale calls for pore scale simulations. It has been shown that neural networks can be trained with a dataset of flow simulations and then predict fields orders of magnitude faster, and with less computational resources, in new domains. However, it is crucial to provide the neural network with an effective description of the domain and the undergoing operating conditions to be able to train models that generalize accurately in unseen samples. Therefore, research is needed to employ neural networks in new complex systems. The appropriate training of a network for predicting coupled flow and solute transport processes is an outstanding problem due to the complex interplay between geometry and operating conditions. In this work, we train a multi scale convolutional neural network (MSNet) with a diverse dataset of simulations of transport and chemical reaction in porous media to predict the local concentration fields in images of porous media. Our dataset contains a wide diversity of sphere pack arrangements under different operating conditions (Péclet and Reynolds numbers). Further, we train a robust model by employing different input descriptors that represent the medium and the different operating conditions of each system. Our trained model is able to provide nearly instantaneous predictions, compared to around twenty hours of the CFD workflow, with less than 3.5% error on new geometries and transport conditions. Thus the model could be easily integrated in a multiscale workflow where fast response is needed.

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

Characterization of Hanford LAW Phase 3 Glasses

This report provides analyses of glass compositions, wash solution compositions, and Product Consistency Test (PCT) leachate compositions for a series of simulated low-activity waste (LAW) glasses fabricated at the Pacific Northwest National Laboratory (PNNL). These data will be used in the development of improved property/composition models for LAW glass at Hanford. Chemical analyses were performed on a representative sample of each of the quenched and sulfur saturated glasses to allow for comparisons with the targeted compositions. For some of the quenched glasses, measured concentrations of Cr₂O₃, K₂O, Na₂O, P₂O₅, and ZrO₂ were below the targeted values. For some of the sulfur saturated glasses, the measured concentrations of Al₂O₃, Cl⁻, Cr₂O₃, F⁻, K₂O, Na₂O, P₂O₅, V₂O₅, and ZrO₂ were generally low relative to the targeted values. A comparison of the measured compositions of the quenched and sulfur saturated versions of the study glasses showed that the measured concentrations of Al₂O₃, Cl⁻, and F⁻ were lower for most of the sulfur saturated glasses. The measured Cr₂O₃ and K₂O concentrations were markedly lower for the sulfur saturated versions of the glasses as compared to the quenched versions, which may indicate that these elements partitioned to the soluble sulfur salts. A set of modified glasses was received from PNNL later in this study. Chemical analysis showed that these glasses generally met their targeted compositions. The measured SO₃ concentrations were higher for most of the sulfur saturated glasses relative to those of the quenched versions, as expected. Chemical analysis of the wash solutions that resulted from preparation of the sulfur saturated melts identified Cr, K, Na, P, S, and V as the major elements in solution. With the exception of sulfur, this may explain why the measured concentrations of these components in the study glasses were generally below the targeted values. PNNL performed PCTs on quenched and canister centerline cooled (CCC) versions of the study glasses, as well as the modified glasses. The leachates were sent to SRNL for chemical analysis. Minor scatter in the measured values among the triplicate samples for each glass was noted. Several of the study glasses, both quenched and CCC, have NCi values that are greater than the immobilized LAW constraint of 4 g/L for B, Na, and Si.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1988

Approximations for hypervelocity nonequilibrium radiating, reacting, and conducting stagnation regions

An approximate solution which includes the effects of chemical and thermal nonequilibrium and nonequilibrium nongray radiative transfer and which is suitable for rapidly obtaining approximate solutions for flowfield structure and estimates of radiative heat transfer is presented. Comparisons are made with Fire 2 data and example applications to a hypothetical Mars return AOTV are presented. Parametric results indicate that further studies of VUV processes and radiation models are needed.

Carlson, Leland A.↗
NASA NTRS2006

Preventing Ice Before it Forms

In the late 1990s, a team of engineers at Ames Research Center invented an anti-icing fluid to keep ice from building up on airplane wings. Ice on wings can be a serious safety hazard, especially during takeoff, when a sheet of ice the thickness of a compact disc can reduce lift by 25 percent or more. The typical approach to clearing off the ice is to use a deicing solution once the ice has built up. The fluid created by the Ames team, though, when applied to a dry surface, prevents the ice from even forming a surface bond, which saves deicing time and money, while also preventing excessive use of chemical solvents. If, however, the solution is not applied before ice forms, it also serves as a traditional deicing formula. The formula contains propylene glycol, which has a very low freezing point, and a thickener, which helps the fluid adhere to the surface. Ice gathers on top of the formula, and then it can be wiped off with little effort. This thickening agent, a pseudo-plastic, sprays on as a liquid, like lemonade, gels like a lemon sherbet, turns back to a liquid when wiped, and then gels again into its sherbet consistency when left to solidify. The sherbet-gel stage is especially important when the formula is sprayed onto a vertical or steeped surface, as it clings better than a liquid would.

Source record↗
DOE OSTI2026

Viscous Gubser flow with conserved charges to benchmark fluid simulations

We present semi-analytical solutions for the evolution of both the temperature and chemical potentials for viscous Gubser flow with conserved charges. Such a solution can be especially useful in testing numerical codes intended to simulate relativistic fluids with large chemical potentials. The freeze-out hypersurface profiles for constant energy density are calculated, along with the corresponding normal vectors, and presented as a new unit test for numerical codes. We also compare the influence of the equation of state on the semi-analytical solutions. We benchmark the newly developed smoothed particle hydrodynamics code ccake that includes both shear viscosity and three conserved charges. Here, the numerical solutions are in excellent agreement with the semi-analytical solution and are also able to accurately reproduce the hypersurface at freeze-out.

Hydrodynamic models↗
NASA NTRS1976

Non-equilibrium radiation from viscous chemically reacting two-phase exhaust plumes

A knowledge of the structure of the rocket exhaust plumes is necessary to solve problems involving plume signatures, base heating, plume/surface interactions, etc. An algorithm is presented which treats the viscous flow of multiphase chemically reacting fluids in a two-dimensional or axisymmetric supersonic flow field. The gas-particle flow solution is fully coupled with the chemical kinetics calculated using an implicit scheme to calculate chemical production rates. Viscous effects include chemical species diffusion with the viscosity coefficient calculated using a two-equation turbulent kinetic energy model.

Penny, M. M.↗
NASA NTRS1980

Chemical research projects office: An overview and bibliography, 1975-1980

The activities of the Chemical Research Projects Office at Ames Research Center, Moffett Field, California are reported. The office conducts basic and applied research in the fields of polymer chemistry, computational chemistry, polymer physics, and physical and organic chemistry. It works to identify the chemical research and technology required for solutions to problems of national urgency, synchronous with the aeronautic and space effort. It conducts interdisciplinary research on chemical problems, mainly in areas of macromolecular science and fire research. The office also acts as liaison with the engineering community and assures that relevant technology is made available to other NASA centers, agencies, and industry. Recent accomplishments are listed in this report. Activities of the three research groups, Polymer Research, Aircraft Operating and Safety, and Engineering Testing, are summarized. A complete bibliography which lists all Chemical Research Projects Office publications, contracts, grants, patents, and presentations from 1975 to 1980 is included.

Kourtides, D. A.↗
NASA NTRS1991

Inhomogeneous halo collapse and early Galactic chemical evolution - Globular cluster metallicities

A new solution to the observed Galactic globular cluster metallicity distribution is proposed by considering inhomogeneous collapse of a centrally condensed proto-Galaxy. In contrast to the standard one-zone model, it is shown that, for inhomogeneous models, the metallicity distribution can be reproduced without the need to decrease the nucleosynthetic yield for metal-poor stars. Chemical evolution in free fall is calculated analytically. A hybrid hydroparticle code is developed to study the effect of supernova induced pressure.

Malinie, G.↗
DOE OSTI2025

Prediction of Solute Segregation at Metal/Oxide Interfaces Using Machine Learning Approaches

The atomic structure and chemistry at metal/oxide interfaces play a crucial role in determining their properties. However, studying semi-coherent metal/oxide interfaces that include misfit dislocations through density functional theory (DFT) is often computationally expensive due to the large number of atoms involved, ranging from hundreds to thousands. In this study, we explore solute segregation behavior at the Fe/Y 2 O 3 interface—an important model interface for cladding applications in nuclear fission reactors—by combining DFT calculations with a machine learning (ML) approach. ML models are trained using DFT-calculated segregation energies (𝐸 𝑆𝑒𝑔 ) to identify the key chemical and geometric factors influencing solute segregation at metal/oxide interfaces, revealing the competition between these features in determining 𝐸 𝑆𝑒𝑔 . Moreover, the segregation behavior at a specific Fe/Y 2 O 3 interface is predicted with high accuracy using ML models trained on data from this interface. Furthermore, it is found that the ML models could also predict solute segregation at a different Fe/Y 2 O 3 interface with a new orientation relationship (OR), at a computational cost of less than 1/45 of that required for similar DFT calculations.

36 - MATERIALS SCIENCE↗
NASA NTRS1990

Critical evaluation of Jet-A spray combustion using propane chemical kinetics in gas turbine combustion simulated by KIVA-2

Jet-A spray combustion has been evaluated in gas turbine combustion with the use of propane chemical kinetics as the first approximation for the chemical reactions. Here, the numerical solutions are obtained by using the KIVA-2 computer code. The KIVA-2 code is the most developed of the available multidimensional combustion computer programs for application of the in-cylinder combustion dynamics of internal combustion engines. The released version of KIVA-2 assumes that 12 chemical species are present; the code uses an Arrhenius kinetic-controlled combustion model governed by a four-step global chemical reaction and six equilibrium reactions. Researchers efforts involve the addition of Jet-A thermophysical properties and the implementation of detailed reaction mechanisms for propane oxidation. Three different detailed reaction mechanism models are considered. The first model consists of 131 reactions and 45 species. This is considered as the full mechanism which is developed through the study of chemical kinetics of propane combustion in an enclosed chamber. The full mechanism is evaluated by comparing calculated ignition delay times with available shock tube data. However, these detailed reactions occupy too much computer memory and CPU time for the computation. Therefore, it only serves as a benchmark case by which to evaluate other simplified models. Two possible simplified models were tested in the existing computer code KIVA-2 for the same conditions as used with the full mechanism. One model is obtained through a sensitivity analysis using LSENS, the general kinetics and sensitivity analysis program code of D. A. Bittker and K. Radhakrishnan. This model consists of 45 chemical reactions and 27 species. The other model is based on the work published by C. K. Westbrook and F. L. Dryer.

Nguyen, H. L.↗
DOE OSTI2024

Chemical specificity in polyzwitterion-polyelectrolyte coacervates: polycations vs polyanions

Aqueous solutions containing polyzwitterions and polyelectrolytes were studied to probe the effects of chemical specificity on the complexation among different types of chains and resulting liquid–liquid phase separation (coacervation). Two kinds of blends were studied. A polyzwitterion, poly(sulfobetaine methacrylate) (PSBMA), was blended with either (1) a polycation, poly(diallydimethylammonium chloride) (PDADMAC), or (2) a polyanion, sodium poly(styrene sulphonate) (NaPSS). Coacervation was observed in both blends after equilibration, while the freshly prepared blend solutions exhibited distinct behavior dependent on the mixing protocols. Mixing solutions of the polyzwitterions and the polycations led to coacervation almost instantaneously. In contrast, the blends containing the same polyzwitterions and the polyanions exhibited no such coacervation by following the same mixing protocol. However, blends prepared after dissolving a solid mixture containing the same polyzwitterions and the polyanions in water exhibited coacervation. Based on the small-angle X-ray scattering (SAXS), cryo-electron microscopy, and rheology measurements, complexation and coacervation in the polyzwitterion-polyelectrolyte blends is rationalized in terms of the entropy change associated with reorganization of solvent (water), which appears to be larger in the polyzwitterion-polycation case in comparison with the polyzwitterion-polyanion blends. These results highlight the importance of chemical specificity and mixing protocols leading to metastable structures in designing a new class of materials based on macromolecular complexation of polyzwitterions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Chemical heterogeneity modulated zero thermal expansion alloy over super-wide temperature range

Chemical heterogeneity is usually avoided in solution chemistry, but it may still occur with sometimes dramatic effects on target materials and their properties. Here, we propose chemical heterogeneity as a counterintuitive strategy to design high-performance zero thermal expansion (ZTE) alloys. We apply this approach in a Hf-Ti-Fe alloy with excess Fe in the Hf/Ti sublattice and produce Hf/Ti concentration alternations at the micro level. Such chemical heterogeneity regulates local magnetic interactions in alloy and triggers a dispersed magnetic phase transition that modulates the thermal expansions at the micro level and hence results in a remarkable ZTE behavior over a super-wide temperature window from 10 to 480 K. This mechanism is supported by comprehensive studies on morphological microstructures, crystal and magnetic structures, and theoretical calculations. The strategy of local chemical heterogeneity opens up an avenue to design ZTE and the related functional materials directly via microstructure engineering.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Chemical Research Projects Office: Functions, accomplishments, and programs

The purpose, technical accomplishments, and related activities of the Chemical Research Project Group are outlined. Data cover efforts made to: (1) identify chemical research and technology required for solutions to problems of national urgency, synchronous with aeronautics and space effort; (2) conduct basic and applied interdisciplinary research on chemical problems in the areas of macromolecular science and fire research, and (3) provide productive liason with the engineering community and effective transfer of technology to other agencies and industry.

Kourtides, D. A.↗
NASA NTRS1992

Organic crystal growth experiment facility (13-IML-1)

The interesting nature of metal-like organic compounds composed of charge transfer complexes has been recently realized. Crystals of these complexes can usually be grown by the solution crystallization method. It is difficult to grow such organic crystals on Earth, especially from the chemical reactions through diffusion controlled process in the solutions, because of gravitational disturbances, or sedimentation. The International Microgravity Lab. (IML-1) Organic Crystal Growth with G-Gitter Preventive Measure (OCGP) experiment is expected to grow a single crystal large enough to allow its intrinsic physical properties to be measured and its detailed crystal structure to be determined. This experiment also attempts to assess the experimental conditions including the microgravity environment for further study of the fundamental process of solution crystallization, nucleation, and growth from supersaturated phases including chemical reactions. Microgravity disturbances, G-jitter, may be an important environmental factor in the experimental method to assess. The vibration damping effects on organic crystal growth can be carefully studied.

Kanbayashi, Akio↗
NASA NTRS1984

Chemical mechanisms and reaction rates for the initiation of hot corrosion of IN-738

Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions: Cr2O3 + 2 Na2SO4(1) + 3/2 O2 yields 2 Na2CrO4(1) + 2 SO3(g)n TiO2 + Na2SO4(1) yields Na2O(TiO2)n + SO3(g)n TiO2 + Na2CrO4(1) yields Na2O(TiO2)n + CrO3(g).

Fryburg, G. C.↗