Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “solution chemistry”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Molecular Identifications in Experiments with Astronomical Ice Analogues: New Data, Old Strategies, and the N2 + Acetone System

A recent publication on the radiation chemistry and IR spectroscopy of N2 plus acetone ices is used to illustrate some of the difficulties encountered in the study of astronomical ice analogues. Concerns and problems are identified and suggestions for their solution are presented, including new infrared (IR) spectra of amorphous ices. The hazards of using peak positions alone for assignments of the IR spectra of irradiated ices are illustrated, and the importance of considering the underlying reaction chemistry is shown. Several experiments are proposed as a way to investigate the behaviour of acetone in cold, extraterrestrial environments. Electronic versions of IR spectra are provided and several new refractive indices of ices are reported.

Hudson, Reggie L.↗
DOE OSTI2021

Perovskite Oxide–Halide Solid Solutions: A Platform for Electrocatalysts

The successful integration or hybridization of perovskite oxides with their halide cousins would enable the formation of both multi-anionic and multi-cationic solid solutions with unique metal-ion sites and synergistic properties that could potentially surpass the performance of classic perovskites. However, such solid solutions had not been produced previously owing to their distinct formation energies and different synthesis conditions. Solid solutions combining perovskite oxides with fluorides were produced in this study by mechanochemical synthesis. The obtained perovskite oxide–halide solid solutions had highly mixed elements and valences, uniform element distributions, and single-phase crystalline structures. In this work, the solid solution with an optimized combination of oxides and fluorides exhibited enhanced catalytic performance in the oxygen evolution reaction.

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

Structure Activity Relationship Approach toward the Improved Separation of Rare-Earth Elements Using Diglycolamides

The separation of adjacent lanthanides continues to be a challenge worldwide because of the similar physical and chemical properties of these elements and a necessity to advance the use of clean-energy applications. In this paper, a systematic structure–performance relationship approach toward understanding the effect of N-alkyl group characteristics in diglycolamides (DGAs) on the separation of lanthanides(III) from a hydrochloric acid medium is presented. In addition to the three most extensively studied DGA complexants [N,N,N',N'-tetra(n-octyl)diglycolamide, TODGA; N,N,N',N'-tetra(2-ethylhexyl)diglycolamide, TEHDGA; N,N'-dimethyl-N,N'-di(n-octyl)diglycolamide, DMDODGA], 12 new extracting agents with varying substitution patterns were designed to study the interplay of steric and electronic effects that control rare-earth element extraction. Subtle changes in the structure around diglycolamide carbonyl oxygen atoms result in dramatic shifts in the lanthanide extraction strength and selectivity. The effects of the chain length and branching position of N-alkyl substituents in DGAs are elaborated on with the use of experimental, computational, and solution-structure characterization techniques.

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

Thermodynamics and kinetics of solution combustion synthesis: Ni(NO 3 ) 2 + fuels systems

Solution combustion synthesis (SCS) utilizes exothermic self-propagating reactions to prepare nanoscale materials that can be used widely in energy, electronics, and biomedical technologies and other applications. SCS is a specific variety of a more general combustion synthesis (CS) method. Investigations of the thermodynamics, kinetics, and the mechanisms of SCS reactions, are not as well studied as the other CS processes. This work reports on a systematic study of the thermodynamics and kinetics of SCS reactions involving Ni(NO 3 ) 2 , an oxidizer, and either glycine (C 2 H 5 NO 2 ) or hexamethylenetetramine (HMT, C 6 H 12 N 4 ) as fuels. A thermodynamic modeling approach, based on the Gibbs free energy minimization principle, is applied to the simultaneous calculations of the adiabatic temperatures and compositions of the equilibrium products. Our calculations reveal the influence of fuel-to-oxidizer ratio, amount of water, and the oxygen in air on the combustion temperature under adiabatic conditions and the composition of the resulting products. We have, in turn, measured the combustion temperature and phase composition of products and compared them with the calculations. Variations of drying times for the solutions yield precursor gels with varying water contents. This approach enables the manipulation of combustion parameters and confirms the use of calculated activation energies for reactions using the Merzhanov-Khaikin method. Here, the results show that SCS reactions in fuel-lean solutions producing NiO have higher activation energy in contrast to reactions with fuel-rich solutions that form Ni. Reduction of activation energies due to the increase in the fuel-to-oxidizer ratio could be related to the observed change of the rate-limiting stages of the endothermic decomposition of the individual reactants to the exothermic decomposition of coordinate compounds formed between the reactants.

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

A Materials Perspective on Direct Recycling of Lithium-Ion Batteries: Principles, Challenges and Opportunities

As the dominant means of energy storage technology today, the widespread deployment of lithium-ion batteries (LIBs) would inevitably generate countless spent batteries at their end of life. From the perspectives of environmental protection and resource sustainability, recycling is a necessary strategy to manage end-of-life LIBs. Compared with traditional hydrometallurgical and pyrometallurgical recycling methods, the emerging direct recycling technology, rejuvenating spent electrode materials via a non-destructive way, has attracted rising attention due to its energy efficient processes along with increased economic return and reduced CO 2 footprint. This review investigates the state-of-the-art direct recycling technologies based on effective relithiation through solid-state, aqueous, eutectic solution and ionic liquid mediums and thoroughly discusses the underlying regeneration mechanism of each method regarding different battery chemistries. It is concluded that direct regeneration can be a more energy-efficient, cost-effective, and sustainable way to recycle spent LIBs compared with traditional approaches. Additionally, it is also identified that the direct recycling technology is still in its infancy with several fundamental and technological hurdles such as efficient separation, binder removal and electrolyte recovery. Finally, in addressing these remaining challenges, this review proposes an outlook on potential technical avenues to accelerate the development of direct recycling toward industrial applications.

25 ENERGY STORAGE↗
DOE OSTI2022

A step-wise ion hydration model of aqueous electrolyte solution: The 2:2, 2:1 and 1:2 punches

In prior work we showed that the current step-wise hydration framework shows promise for modeling the concentration-activity relationship in aqueous solutions of ions representing 1:1 electrolytes, alcohols, and sugars, and accurately predicting the partitioning of the water between the bound (hydrated) pool and an unbound (free) pool. Here, in the current work, we continue developing this framework by applying it to ions representing 2:2, 2:1 and 1:2 electrolyte in aqueous solutions. Properly treating ion hydration as an ideal solution along with employing mean spherical approximation of the long-range electrostatic interactions yields an accurate model for most electrolytes considered. This simple model of aqueous solutions is robust for electrolytes and organic solutes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Open Circuit Potential of a Au Catalyst during Selective Oxidation of Glycerol

It has been of great interest to understand relationships between the potential of a metal catalyst and its thermochemical catalytic activity, especially in an aqueous phase environment. In the literature, there are correlations of open circuit potential with reaction rates or surface concentrations of reaction intermediates. In this study, we measured the open circuit potential (OCP) of a Au gauze during selective oxidation of glycerol to glyceric acid and hydrogen peroxide in a basic solution, as a function of hydroxide and alcoholate concentrations. It is found that applying a potential to the Au catalyst has no influence on the reaction rate. Although a rough correlation appears to exist between OCP and reaction rate, the data are better fit to an equation which assumes that the potential of the metal (i.e. the OCP) is in equilibrium with the electrochemical potential of the solution, which is defined by the thermodynamic activities of the oxidizing and reducing species. The equation: OCP = constant + Σ ox [(RT/FZ ox )ln[Ox]] - Σ red [(RT/FZ red )ln[Red]] implicitly assumes that the Au metal functions as a probing electrode. It is further found that this equation also applies to the Au-catalyzed H 2 O 2 oxidation/decomposition reaction in a basic medium, and possibly to formic acid dehydrogenation. Here, we postulate that the apparent correlation between OCP and reaction rate is due to the fact that the reaction rate is proportional to the concentrations of the reaction products and/or reactants that define the electrochemical potential of the solution.

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

The influence of Al2O3 on the structural properties of MgSiO3 akimotoite

Abstract Akimotoite, a MgSiO3 polymorph present in the lower transition zone within ultramafic portions of subducting slabs and potentially also in the ambient mantle, will partition some amount of Al, raising the question of how this will affect its crystal structure and properties. In this study, a series of samples along the MgSiO3-Al2O3 (akimotoite-corundum) solid solution have been investigated by means of single-crystal X-ray diffraction to examine their crystal chemistry. Results show a strong nonlinear behavior of the a- and c-axes as a function of Al content, which arises from fundamentally different accommodation mechanisms in the akimotoite and corundum structures. Furthermore, two Al2O3-bearing akimotoite samples were investigated at high pressure to determine the different compression mechanisms associated with Al substitution. Al2O3-bearing akimotoite becomes more compressible at least up to 20 mol% Al2O3, due likely to an increase in compressibility as the Al cation is incorporated into the SiO6 octahedron. This observation is in strong contrast to the stiffer corundum end-member having a KT = 250 GPa, which is larger than that of the akimotoite end-member [KT = 205(1) GPa]. These findings have implications for mineral physics models of elastic properties, which have in the past assumed linear mixing behavior between the MgSiO3 akimotoite and Al2O3 corundum end-members to calculate sound wave velocities for Al-bearing akimotoite at high pressure and temperature.

Geochemistry & Geophysics↗
DOE OSTI2020

A short tutorial on uranium electropolishing

Electropolishing of uranium metal is best performed in a simple aqueous solution of phosphoric acid. With +3 to +10 volts of bias potential applied to the uranium (anode) relative to a Pt counter electrode (cathode). As summarized in a Pourbaix stability diagram, these conditions yield dissolution of the U surface as UOX containing solution species without the possibility of injecting hydrogen into the metal surface. However, if the uranium is biased to negative potentials relative to the counter electrode then water may be reduced at the U surface and hydrogen gas becomes available for reaction with the U metal. The stability diagram may be modified if there are other complexing species present in solution and the potential scale shifted if a different metal is use for the counter electrode. These effects can be understood in a known way as long as solution and electrochemical cell conditions are recognized.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Sustainable Functional Epoxies through Boric Acid Templating

Thermoset polymers (e.g. epoxies, vulcanizable rubbers, polyurethanes, etc.) are crosslinked materials with excellent thermal, chemical, and mechanical stability; these properties make thermoset materials attractive for use in harsh applications and environments. Unfortunately, material robustness means that these materials persist in the environment with very slow degradation over long periods of time. Balancing the benefits of material performance with sustainability is a challenge in need of novel solutions. Here, we aimed to address this challenge by incorporating boronic acid-amine complexes into epoxy thermoset chemistries, facilitating degradation of the material under pH neutral to alkaline conditions; in this scenario, water acts as an initiator to remove boron species, creating a porous structure with an enhanced surface area that makes the material more amenable to environmental degradation. Furthermore, the expulsion of the boron leaves the residual pores rich in amines which can be exploited for CO 2 absorption or other functionalization. We demonstrated the formation of novel boron species from neat mixing of amine compounds with boric acid, including one complex that appears highly stable under nitrogen atmosphere up to 600 °C. While degradation of the materials under static, alkaline conditions (our “trigger”) was inconclusive at the time of this writing, dynamic conditions appeared more promising. Additionally, we showed that increasing boronic acid content created materials more resistant to thermal degradation, thus improving performance under typical high temperature use conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microbial Influence on the Mobility of +3 Actinides from a Salt-Based Nuclear Waste Repository

Biologically enhanced transport of radionuclides is one of several processes that can affect the performance of a nuclear waste repository. In this work, several microbial isolates from the Waste Isolation Pilot Plant (WIPP) were tested for their influence on the concentration of neodymium, as an analog for +3 actinides, in simple sodium chloride solutions and in anoxic WIPP brines. Batch sorption experiments were carried out over a period of 4–5 weeks. In many cases, the effect on neodymium in solution was immediate and extensive and assumed to be due to surface complexation. However, over time, the continued loss of Nd from the solution was more likely due to biologically induced precipitation and/or mineralization and possible entrapment in extracellular polymeric substances. The results showed no correlation between organism type and the extent of its influence on neodymium in solution. However, a correlation was observed between different test matrices (simple NaCl versus high-magnesium brine versus high-NaCl brine). Further experiments were conducted to test these matrix effects, and the results showed a significant effect of magnesium concentration on the ability of microorganisms to remove Nd from solution. Possible mechanisms include cation competition and the alteration of cell surface structures. This suggests that the aqueous chemistry of the WIPP environs could play a larger role in the final disposition of +3 actinides than the microbiology.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1989

Boost-phase discrimination research activities

Theoretical research in two areas was performed. The aerothermodynamics research focused on the hard-body and rocket plume flows. Analytical real gas models to describe finite rate chemistry were developed and incorporated into the three-dimensional flow codes. New numerical algorithms capable of treating multi-species reacting gas equations and treating flows with large gradients were also developed. The computational chemistry research focused on the determination of spectral radiative intensity factors, transport properties and reaction rates. Ab initio solutions to the Schrodinger equation provided potential energy curves transition moments (radiative probabilities and strengths) and potential energy surfaces. These surfaces were then coupled with classical particle reactive trajectories to compute reaction cross-sections and rates.

Cooper, David M.↗
NASA NTRS1991

Modern CFD applications for the design of a reacting shear layer facility

The RPLUS2D code, capable of calculating high speed reacting flows, has been adopted to design a compressible shear layer facility. In order to create reacting shear layers at high convective Mach numbers, hot air streams at supersonic speeds, render by converging-diverging nozzles, must be provided. A finite rate chemistry model is used to simulate the nozzle flows. Results are compared with one-dimensional, chemically equilibrium solutions. Additionally, a two equation turbulence model with compressibility effects has been successfully incorporated with the RPLUS code. The model has been applied to simulate a supersonic shear layer. Preliminary results show favorable comparisons with the experimental data.

Yu, S. T.↗
NASA NTRS1991

Development of new flux splitting schemes

Maximizing both accuracy and efficiency has been the primary objective in designing a numerical algorithm for CFD. This is especially important for solution of complex three-dimensional systems of Navier-Stokes equations which often include turbulence modeling and chemistry effects. Recently, upwind schemes have been well received for both their capability of resolving discontinuities and their sound theoretical basis in characteristic theory for hyperbolic systems. With this in mind, two new flux splitting techniques are presented for upwind differencing.

Liou, MENG-S.↗