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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

The Behavior of Methane-Air Partially Premixed Flames Under Normal- and Zero-G Conditions

Partially premixed flames (PPFs) represent a class of hybrid flames containing multiple reaction zones. These flames are established when less than stoichiometric quantity of oxidizer is molecularly mixed with the fuel stream before entering the reaction zone where additional oxidizer is available for complete combustion. This mode of combustion can be used to exploit the advantages of both nonpremixed and premixed flames regarding operational safety, lower pollutant emissions and flame stabilization. A double flame containing a fuel-rich premixed reaction zone, which is anchored by a nonpremixed reaction zone, is one example of a partially premixed flame. A triple flame is also a PPF that contains three reaction zones, namely, a fuel-rich premixed zone, a fuel-lean premixed zone, and a nonpremixed reaction zone. Herein we focus on two aspects of our investigation, one involving the development of optical diagnostics that can be used on a microgravity rig, which has been recently fabricated, and the other on the numerically predicted differences between normal- and zero-gravity PPFs. Both the measurements and simulations examine the detailed structure of methane-air PPFs stabilized on a Wolfhard-Parker slot burner.

Puri, Ishwar K.↗
DOE OSTI2019

Droplet Imbibition Enables Nonequilibrium Interfacial Reactions in Charged Microdroplets

A droplet imbibition experiment is proposed to study interfacial effects, which appears to be the main factor influencing reaction acceleration in charged microdroplets produced by electrospray ionization (ESI). One reagent is deposited onto the surface of rapidly moving microdroplets containing the second reagent to be reacted. In this manner, reactions are hindered from reaching equilibrium and monitored in real time by mass spectrometry. We demonstrated this phenomenon using Katritzky chemistry, which is known to proceed either by the solvent-stabilized 2H-pyran intermediate or via the surface-active pseudobase intermediate. Additionally, comparisons with reactions performed using ESI show obvious surface effects in favor of the droplet imbibition experiment. By keeping reactant mole ratio constant, it was demonstrated that similar interfacial effects observed in the droplet imbibition experiment can be reached by allowing ESI microdroplets containing premixed reagents to traverse a distance >16 mm. At such spray distance, molecular diffusion and droplet lifetime become comparable allowing reactants to be enriched at droplet surface. Reactions were also conducted in rapid mixing, theta capillary-based droplets, which showed markedly reduced yields compared with the interfacial droplet imbibition experiment.

36 MATERIALS SCIENCE↗
NASA NTRS2004

Simulation of Aerosols and Chemistry with a Unified Global Model

This project is to continue the development of the global simulation capabilities of tropospheric and stratospheric chemistry and aerosols in a unified global model. This is a part of our overall investigation of aerosol-chemistry-climate interaction. In the past year, we have enabled the tropospheric chemistry simulations based on the GEOS-CHEM model, and added stratospheric chemical reactions into the GEOS-CHEM such that a globally unified troposphere-stratosphere chemistry and transport can be simulated consistently without any simplifications. The tropospheric chemical mechanism in the GEOS-CHEM includes 80 species and 150 reactions. 24 tracers are transported, including O3, NOx, total nitrogen (NOy), H2O2, CO, and several types of hydrocarbon. The chemical solver used in the GEOS-CHEM model is a highly accurate sparse-matrix vectorized Gear solver (SMVGEAR). The stratospheric chemical mechanism includes an additional approximately 100 reactions and photolysis processes. Because of the large number of total chemical reactions and photolysis processes and very different photochemical regimes involved in the unified simulation, the model demands significant computer resources that are currently not practical. Therefore, several improvements will be taken, such as massive parallelization, code optimization, or selecting a faster solver. We have also continued aerosol simulation (including sulfate, dust, black carbon, organic carbon, and sea-salt) in the global model to cover most of year 2002. These results have been made available to many groups worldwide and accessible from the website http://code916.gsfc.nasa.gov/People/Chin/aot.html.

Chin, Mian↗
DOE OSTI2021

Method—Using Microelectrodes to Explore Solid Polymer Electrolytes

Solid polymer electrolytes are an emerging technology in electrochemistry driven by their use in energy applications such as fuel cells, electrolyzers, and solid-state batteries. Compared to traditional liquid electrolytes, solid polymer electrolytes provide safer, cheaper, and potentially improved device performance. However, there is a lack of standard experimental methods for studying solid electrolytes. Microelectrodes have inherent benefits capable of filling this experimental gap due primarily to their integration into model electrochemical cells with solid electrolytes that represent complex interfaces, enabling additional insight into reaction processes. In this tutorial review, we explore the use of microelectrodes to study solid polymer electrolytes, beginning with a brief history of the field including common experimental cell designs and their benefits and drawbacks. Methods of evaluating essential kinetic and mass-transport parameters are then examined. In addition, the key studies of the past 30 years utilizing microelectrode cells and solid polymer electrolytes are summarized, with important results highlighted and compared. Finally, future studies of solid polymer electrolytes with microelectrodes and potential new avenues of research are commented on.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

Potential energy surfaces for atomic oxygen reactions: Formation of singlet and triplet biradicals as primary reaction products with unsaturated organic molecules

The experimental study of the interaction of atomic oxygen with organic polymer films under LEO conditions has been hampered by the inability to conduct detailed experiments in situ. As a result, studies of the mechanism of oxygen atom reactions have relied on laboratory O-atom sources that do not fully reproduce the orbital environment. For example, it is well established that only ground electronic state O atoms are present at LEO, yet most ground-based sources are known to produce singlet O atoms and molecules and ions in addition to O(3P). Engineers should not rely on such facilities unless it can be demonstrated either that these different O species are inert or that they react in the same fashion as ground state atoms. Ab initio quantum chemical calculations have been aimed at elucidating the biradical intermediates formed during the electrophilic addition of ground and excited-state O atoms to carbon-carbon double bonds in small olefins and aromatic molecules. These biradicals are critical intermediates in any possible insertion, addition and elimination reaction mechanisms. Through these calculations, we will be able to comment on the relative importance of these pathways for O(3P) and O(1D) reactions. The reactions of O atoms with ethylene and benzene are used to illustrate the important features of the mechanisms of atomic oxygen reaction with unsaturated organic compounds and polymeric materials.

Jaffe, Richard L.↗
DOE OSTI2026

Investigation of the 244 Pu ⁢( 48 Ca,𝑥⁢𝑛) 292−𝑥 Fl reaction with the LBNL SHREC detector: Investigation of decay chains of isotopes of flerovium (𝑍=114)

The 244 Pu ⁢( 48 Ca,𝑥⁢𝑛)⁢ 292−𝑥 Fl reaction was investigated at Lawrence Berkeley National Laboratory’s 88 Inch Cyclotron using the Berkeley Gas-filled Separator (BGS), the newly installed Superheavy Recoil detector, along with an upgraded digital electronics and data acquisition system. Seven decay chains were observed starting with an evaporation residue, followed by a single 𝛼 decay and a spontaneous fission. The decay characteristics of these seven decay chains led to an assignment to 288 Fl , the product of the 4⁢𝑛 reaction channel. Two additional chains were (tentatively) assigned to the decay of the 3⁢𝑛 exit channel, 289 Fl . Cross sections for the 4⁢𝑛 and 3⁢𝑛 exit channels were 𝜎 prod =6.7⁢($^{36}_{25}$) pb and 𝜎 prod =1.6⁢($^{22}_{11}$) pb, respectively. Another decay chain, tentatively assigned to the 5⁢𝑛 exit channel through the 48 Ca + 244 Pu reaction or the 3⁢𝑛 exit channel of the 48 Ca + 242 Pu reaction, was also detected. Detailed information regarding the observed decay chains and their nuclear structure aspects is discussed, along with the performance of the BGS and the new detection system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1975

Chemical reactions of metal powders with organic and inorganic liquids during ball milling

Chromium and/or nickel powders were milled in metal chlorides and in organic liquids representative of various functional groups. The powders always reacted with the liquid and became contaminated with elements from them. The milled powders had specific surface areas ranging from 0.14 to 37 sq m/g, and the total contamination with elements from the milling liquid ranged from 0.01 to 56 weight percent. Compounds resulting from substitution, addition, or elimination reactions formed in or from the milling liquid.

Arias, A.↗
DOE OSTI2026

Porous reaction-bonded silicon nitride: Size effects for pressureless nitriding of binder jet additively manufactured silicon

The direct nitridation of binder jet additively manufactured silicon to produce porous reaction-bonded silicon nitride was explored to determine the maximum thickness of the sample that could be converted to >99% silicon nitride. The maximum thickness that could be nitrided was investigated by nitriding cubes of increasing physical size on the millimeter scale. Highly porous samples with high conversion ( > 99%) to silicon nitride were achieved in cubes with 35 mm edge length. It was shown that the silicon nitride phase content changes with increasing sample size.

Aguirre, Trevor [ORNL] (ORCID:0000000281469630)↗
NASA NTRS1976

Metal powder reactions in ball milling

On milling chromium powder in three metal chlorides and either chromium or nickel powders in ten organic liquids representative of nine different functional groups, the powders always reacted with the liquids and became contaminated with elements from them. The milled powders had specific surface areas ranging from 0.14 to 37 sq m/g, and the total contamination with elements from the milling liquid ranged from 0.01 to 56 wt%. In most milling runs, compounds resulting from substitution, addition, or elimination reactions formed in or from the milling liquid, and in most runs with organic liquids H2, CH4, and CO2 were generated.

Arias, A.↗
DOE OSTI2020

Influence of the double bond position in combustion chemistry of methyl butene isomers: A shock tube and laser absorption study

Shock tube experiments have been carried out on 2–methyl–1–butene (2M1B), 2–methyl–2–butene (2M2B), and 3–methyl–1–butene (3M1B)—the three isomers of methyl butene compound. Here, carbon monoxide (CO) time–histories and ignition delay times are obtained behind reflected shockwaves over the temperature range of 1350–1630 K and pressures of 8.3–10.5 atm with stoichiometric mixtures of 0.075% fuel in O 2 /Ar. Comparative ignition study reveals that 3M1B ignites significantly faster than the other two isomers, while 2M1B dissociates earlier but ignites later than 2M2B. Possible mechanisms for this behavior are discussed with ignition delay time sensitivity and reaction path analysis. In addition, time–resolved CO measurements are compared with three different reaction mechanisms from the literature. Sensitivity analyses have been carried out to identify important reactions that need attention to accurately predict the chemistry of these isomers. Further investigation into the rates of unimolecular fuel decomposition reactions and C 3 H 3 + O 2 = CH 2 CO + HCO reaction are suggested based on the current investigation.

09 BIOMASS FUELS↗
NASA NTRSDate not supplied

Predicting Thermal Response in a Li-ion Cell on a UAV Fight Profile

As the energy storage devices continue to "pack" more energy in a small space, any damage, battery component failure, manufacturing defect, or electrically abusing the battery can lead to catastrophic thermal runaway events. A catastrophic thermal event in a cell leads to high temperature, in some instances spewing of battery materials due to gas development from side reactions initiated due to high internal temperatures. Also, a thermal runaway event can propagate from a single "failed" cell to the pack in a battery pack, leading to a more significant event. Mitigating a thermal runaway event is important in the commercial and automotive sectors. However, preventing such events in an electric aircraft (or air taxis) is paramount due to the lack of alternatives in the event of a failure. Battery prognostics algorithms allow the prediction of state-of-charge (SOC) and end-of-life (EOL) of a Li-ion battery in a UAV (unmanned air vehicle) [1]. For this presentation, we will extend this two-level battery predictive algorithm to predict SOC, EOL, and estimated maximum temperature during a simulated flight. The model is extended by integrating a lumped physics-driven thermal model for high current densities [2]. The parameters used to control SOC and EOL are maximum storable charge, time constant for Li-ion diffusivity in the carbon particles, and internal cell resistance. Cycling leads to an increase in the heat generated by an aged Li-ion cell with a LiyCoO2 (LCO) cathode and a LixC6 (MCMB) anode. The aging of a cell leads to increase in SEI layer thickness, the diffusion time for the lithium ions inside the electrodes, and the local reaction rates, in addition to the thermodynamic abuse caused by fixed cycling voltages controlled by a Battery Management System. As the battery ages, the cell resistance increases, while the onset temperature of the thermal runaway decreases (depends on the cell chemistry and cell abuse history). Any large deviation of the cell temperature from the estimated (expected) value can identify a faulty cell. Since SEI decomposition has the lowest onset temperature in the series of reactions leading to thermal runaway, the model considers the self-heating rate of the SEI decomposition as onset temperature (similar to Ref. [3]). The parameters in the Arrhenius equation for the SEI heating rate depend on the number of cycles, the cell's operating temperature, and the cell's abuse history [4,5]. Coupling the electrochemical, thermal, and aging model allow the prognostic algorithm to estimate a typical cell voltage and temperature as a function of age (cycling and calendar), whose departure from measured values from the BMS is used to identify a safety event. In addition, we will present the results from two simulated flight scenarios for a UAV: typical and extreme, since the power requirements vary significantly during take-off, landing, and changing altitudes, while the power requirements remain low during the cruise. For this presentation, the power requirement for a battery pack in a UAV is scaled to a single cell. This cell is cycled through a simulated profile, and the data is collected and used to predict a safety event.

Li-ion↗
DOE OSTI2025

Solar fusion III: New data and theory for hydrogen-burning stars

In stars that lie on the main sequence in the Hertzsprung-Russell diagram, like our Sun, hydrogen is fused to helium in a number of nuclear reaction chains and series, such as the proton-proton chain and the carbon-nitrogen-oxygen cycles. Precisely determined thermonuclear rates of these reactions lie at the foundation of the standard solar model. This review, the third decadal evaluation of the nuclear physics of hydrogen-burning stars, is motivated by the great advances made in recent years by solar neutrino observatories, putting experimental knowledge of the proton-proton (𝑝⁢𝑝)-chain neutrino fluxes in the few-percent precision range. The basis of the review is a one-week community meeting held in July 2022 in Berkeley, California, and many subsequent digital meetings and exchanges. The relevant reactions of solar and stellar hydrogen burning are reviewed here from both theoretical and experimental perspectives. Recommendations for the state of the art of the astrophysical 𝑆 factor and its uncertainty are formulated for each of them. Furthermore, several other topics of paramount importance for the solar model are reviewed as well: recent and future neutrino experiments, electron screening, radiative opacities, and current and upcoming experimental facilities. In addition to reaction-specific recommendations, general recommendations are also formed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Effects of gas purity on backgrounds of collision reaction cell-equipped MC-ICP-MS

The advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) instruments equipped with collision reaction cells (CRCs) facilitates interference removal/mitigation via online gas phase separations. This approach has proven effective for high intensity ion beams measured on Faraday collectors; however, it has been observed that introduction of gas in the CRC can result in significant background signals relative to the more sensitive ion counters. These backgrounds hinder use of these instruments for low level concentration and isotopic ratio measurements when employing a reaction gas. Here, this work directly evaluates the effect of gas purity on backgrounds of CRC-MC-ICP-MS instruments. Introducing high-purity research grade O 2 (99.999%) into the CRC produces complex background spectra with intensities >10 4 cps observed at most masses across the measured mass range (7-300 m / z ). Some features of the observed spectra (i.e., positive mass defects) can be attributed to molecular compounds comprised of significant hydrogen. Additionally, some specific molecular species can be identified (i.e., MoO x H y + ) and appear to be derived from molybdenum rods comprising the CRC. Further purifying the gas reduces the intensity of these backgrounds by several orders of magnitude, to <10 2 cps in many cases, and reduces complexity of the resulting spectra. This reduction in background appears to be in part driven by removal of impurities (i.e., H 2 O) from the gas. This work demonstrates that additional purification of reaction gases prior to introduction into the CRC significantly reduces backgrounds detected, potentially expanding the utility of CRC-MC-ICP-MS for making low level measurements using inline gas phase ion separations.

Schlieder, Tyler D. [Pacific Northwest National La↗
DOE OSTI2021

Millisecond timescale reactions observed via X-ray spectroscopy in a 3D microfabricated fused silica mixer

Determination of electronic structures during chemical reactions remains challenging in studies which involve reactions in the millisecond timescale, toxic chemicals, and/or anaerobic conditions. Here, a three-dimensionally (3D) microfabricated microfluidic mixer platform that is compatible with time-resolved X-ray absorption and emission spectroscopy (XAS and XES, respectively) is presented. This platform, to initiate reactions and study their progression, mixes a high flow rate (0.50–1.5 ml min –1 ) sheath stream with a low-flow-rate (5–90 µl min –1 ) sample stream within a monolithic fused silica chip. The chip geometry enables hydro­dynamic focusing of the sample stream in 3D and sample widths as small as 5 µm. The chip is also connected to a polyimide capillary downstream to enable sample stream deceleration, expansion, and X-ray detection. In this capillary, sample widths of 50 µm are demonstrated. Further, convection–diffusion-reaction models of the mixer are presented. The models are experimentally validated using confocal epifluorescence microscopy and XAS/XES measurements of a ferricyanide and ascorbic acid reaction. The models additionally enable prediction of the residence time and residence time uncertainty of reactive species as well as mixing times. Residence times (from initiation of mixing to the point of X-ray detection) during sample stream expansion as small as 2.1 ± 0.3 ms are also demonstrated. Importantly, an exploration of the mixer operational space reveals a theoretical minimum mixing time of 0.91 ms. The proposed platform is applicable to the determination of the electronic structure of conventionally inaccessible reaction intermediates.

3D microfabrication↗
NASA NTRS1999

Methane Pyrolysis and Disposing Off Resulting Carbon

Sabatier/Electrolysis (S/E) is a leading process for producing methane and oxygen for application to Mars ISPP. One significant problem with this process is that it produces an excess of methane for combustion with the amount of oxygen that is produced. Therefore, one must discard roughly half of the methane to obtain the proper stoichiometric methane/oxygen mixture for ascent from Mars. This is wasteful of hydrogen, which must be brought from Earth and is difficult to transport to Mars and store on Mars. To reduced the problem of transporting hydrogen to Mars, the S/E process can be augmented by another process which reduces overall hydrogen requirement. Three conceptual approaches for doing this are (1) recover hydrogen from the excess methane produced by the S/E process, (2) convert the methane to a higher hydrocarbon or other organic with a lower H/C ratio than methane, and (3) use a separate process (such as zirconia or reverse water gas shift reaction) to produce additional oxygen, thus utilizing all the methane produced by the Sabatier process. We report our results here on recovering hydrogen from the excess methane using pyrolysis of methane. Pyrolysis has the advantage that it produces almost pure hydrogen, and any unreacted methane can pass through the S/E process reactor. It has the disadvantage that disposing of the carbon produced by pyrolysis presents difficulties. Hydrogen may be obtained from methane by pyrolysis in the temperature range 10000-12000C. The main reaction products are hydrogen and carbon, though very small amounts of higher hydrocarbons, including aromatic hydrocarbons are formed. The conversion efficiency is about 95% at 12000C. One needs to distinguish between thermodynamic equilibrium conversion and conversion limited by kinetics in a finite reactor.

Sharma, P. K.↗
DOE OSTI2021

Influence of microstructure on replacement and porosity generation during experimental dolomitization of limestones

Replacement reactions commonly alter the multiscale pore structures of rocks during fluid-rock interactions. Analysis of these processes in various model fluid-rock systems during controlled laboratory experiments provides insights into the origins of microstructures found in natural materials. This study focused on understanding the effects of initial starting material permeability and resultant differences in transport pathways on porosity and mineralogical changes during limestone dolomitization.A series of replacement experiments (32–317 days in duration) have been conducted in which 1.59 cm (5/8 in.) diameter cores of two different limestones were reacted with saturated MgCl2 solutions at 200 °C. The Texas Cream (Austin Chalk) is a high-porosity, high-permeability limestone, whereas both the porosity and permeability of the Carthage Marble (Burlington Limestone) are relatively low. Altered limestones were imaged using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), Time-of-Flight Secondary Ion Mass Spectrometry (ToF–SIMS) and electron microprobe analysis (EMPA). A representative grain boundary of the low-porosity limestone was targeted for a focused ion beam (FIB) lift-out and characterized using transmission electron microscopy (TEM). These results were coupled with analyses of radial changes in the porosity distribution of the core derived from X-ray and neutron small- and ultra-small angle scattering ((U)SANS/(U)SAXS).The high-porosity/permeability limestone showed a four times faster bulk replacement rate than the lower-porosity/permeability material, and a different mechanism of porosity development. For the low-porosity limestone, a two-stage replacement occurred, with the reacted region of the core consisting of an inner rim in which the limestone was replaced by two calcite-dolomite solid solutions, and an outer rim in which the dolomite was replaced by magnesite. Elongated pores formed along grain boundaries at the initial limestone/dolomite reaction interface, and additional nanometer-scale porosity was formed at the secondary magnesite replacement rim. Grain boundaries were identified as preferential pathways for transport leading to dolomitization and a grain boundary diffusion rate was calculated based on microstructural characterization. In contrast, replacement in the high-porosity limestone was accompanied by porosity generation through replacement of individual grains by dolomite throughout the sample and, in longer runs, magnesite in outer parts of the core. These observations emphasize that both the mechanisms of the replacement reaction and the microstructure and chemistry of the replaced product are contingent on the initial structure of the starting material.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electrolytes in Multiple-Phase Hydrogen Storage Reactions

Multiple-phase hydrogen storage materials such as metal alanates and borohydrides, and destabilized systems offer the possibility of high hydrogen storage capacity with favorable thermodynamics. However, the multiphase nature of these materials intrinsically limits the kinetics due to the required transport of species between phases, which are typically in dry powder form. To address this limitation, the influence of added electrolytes is explored. This approach is motivated by analogy with similar multiphase battery reactions that show reduced kinetic limitations while necessarily containing electrolytes. Previous experimental results showing improved kinetics for MgH2/Sn (using a LiBH4/KBH4 eutectic electrolyte) and NaAlH4 (using a diglyme electrolyte) are further analyzed in terms of this analogy. The results show that the analogy is useful and rate constants are increased. Importantly, the inclusion of an electrolyte also appears to alleviate the continuously decreasing rates with the extent of reaction, which is characteristic of many multiphase hydrides. Instead, reaction rates are approximately constant until near completion. Together, these effects can lead to >10× shorter overall reaction times. In addition, new results are presented for the hydrogenation of MgB2 using Li/K/CsI and Li/K/CsCl eutectic electrolytes, where >60% conversion to Mg(BH4)2 was demonstrated at 350 bar.

08 HYDROGEN↗
DOE OSTI2026

Influence of Nd(II) and Nd(III) Ions on the Speciation and Kinetic Dynamics of Radiolytic Transients in Molten LiCl-KCl Eutectic Salt Mixtures

In the pyrochemical reprocessing of used nuclear fuel, understanding the effects of ionizing radiation on the chemical behavior of fission products in molten chloride eutectic salt is crucial. Here, this study investigates the impact of radiation on the chemical and kinetic speciation of Nd ions in molten LiCl-KCl eutectic, which are challenging to separate due to their multivalent oxidation states and comproportionation reactions. Electron pulse radiolysis techniques were used to determine transient absorption spectra, chemical kinetics, and activation parameters for the reaction of Nd ions with the primary products of molten LiCl-KCl eutectic radiolysis: the solvated electron (e S - ) and dichlorine radical anion (Cl 2 •- ). Initially, Nd(III) reacted rapidly with e S - , forming Nd(II) with a second-order rate coefficient of k = (4.54 ± 0.07) × 10 10 M -1 s -1 at 673 K. The resulting Nd(II) ions then reacted slowly with Cl 2 •- , regenerating Nd(III) with an estimated rate of k = (1.72 ± 0.04) × 10 10 M -1 s -1 at 673 K. Additionally, the comproportionation reaction of Nd(III) and Nd(s) to form Nd(II) was monitored chemically and electrochemically. This work suggests that the comproportionation reaction of Nd(III) with Nd(s) to form Nd(II) is unstable in molten LiCl-KCl eutectic.

36 - MATERIALS SCIENCE↗