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Results for “ALKALI METAL”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Alkali Metal Handling Practices at NASA MSFC

NASA Marshall Space Flight Center (MSFC) is NASA s principle propulsion development center. Research and development is coordinated and carried out on not only the existing transportation systems, but also those that may be flown in the near future. Heat pipe cooled fast fission cores are among several concepts being considered for the Nuclear Systems Initiative. Marshall Space Flight Center has developed a capability to handle high-purity alkali metals for use in heat pipes or liquid metal heat transfer loops. This capability is a low budget prototype of an alkali metal handling system that would allow the production of flight qualified heat pipe modules or alkali metal loops. The processing approach used to introduce pure alkali metal into heat pipe modules and other test articles are described in this paper.

Salvail, Patrick G.↗
DOE OSTI2024

Elucidating the Link Between Alkali Metal Ions and Reaction-Transport Mechanisms in Cathode Electrodes for Alkali-ion Batteries

Our long-term goal is to improve the reliability of electrode materials and their ability to transport and store various metal ions for electrochemical energy storage applications. The main objective of this work was to investigate the intrinsic relationship between the role of alkali metal ions and electrochemically driven mechanical stability and kinetic properties of battery materials. The overall question was “What is the role of alkali metal ions on the electrochemical and mechanical behavior of cathode electrodes? Our guiding hypothesis was that intercalation of larger alkali metal ions (Na and K) inevitably alters the coupled transport-reaction processes during battery operation in organic electrolytes, leading to more intensive chemo-mechanical instabilities in cathode electrodes, resulting in rapid capacity fade. To validate the hypothesis, we experimentally characterized the reaction-transport processes and governing forces driving the instability of electrode materials in different alkali metal-ion environments. The project had three main tasks. The first one was to investigate intercalation-induced strains and associated stress generation, and their impact on structural deformations in composite cathode electrodes. The second task focused on identifying potential-dependent dynamic changes in the electrode-electrolyte interface in alkali metal ion batteries. The last task was focused on determining how larger alkali metal ions with slower diffusivity affect the transport-mechanics coupling at faster scan rates, compared to smaller ions with faster diffusivity in electrodes. We shortly provided the outcome of each task in the accomplishment section. This project produced 10 peer-reviewed publications (9 research papers and one review manuscript) and supported two Ph.D. students, who graduated from Oklahoma State University.

25 ENERGY STORAGE↗
DOE OSTI2025

Promoting the oxidative coupling of methanol and dimethylamine using group 1 alkali metals on palladium-gold nanoparticles

PdAu/SiO 2 catalysts were synthesized by strong electrostatic adsorption (SEA) and characterized by TEM, DRIFTS, XRD, XAS, and O 2 -TPD. The use of group 1 alkali salt solutions to control pH during SEA syntheses led to uptake of alkali metals observed reductions in the densities of terminal silanol groups of the SiO 2 support. In the absence of alkali metals, PdAu/SiO 2 catalyzes oxidative C-N bond formation between methanol and dimethylamine (DMA), yielding dimethylformamide (DMF) with ∼95 % carbon selectivity (CO 2 ∼5 %) at temperatures below 413 K. When Na, K, and Cs were present on the catalyst, methyl formate (MF) and tetramethylurea (TMU) were observed as additional products (combined ∼30 % carbon selectivity) while only TMU was detected for the Li-promoted catalyst. Total coupling product rate increased for promoted samples in the order Li < Na < Cs < K, and the apparent kinetics over the Cs-promoted catalyst were distinct from those over the alkali-free catalyst as the apparent reaction order with respect to DMA decreased and the apparent activation energy increased. Finally, this work demonstrates the sensitivity of oxidative coupling reactions to alkali metal promoters and the opportunity to achieve alkali promotion of metal catalysts during SEA synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Alkali metal vapors - Laser spectroscopy and applications

The paper examines the rapidly expanding use of lasers for spectroscopic studies of alkali metal vapors. Since the alkali metals (lithium, sodium, potassium, rubidium and cesium) are theoretically simple ('visible hydrogen'), readily ionized, and strongly interacting with laser light, they represent ideal systems for quantitative understanding of microscopic interconversion mechanisms between photon (e.g., solar or laser), chemical, electrical and thermal energy. The possible implications of such understanding for a wide variety of practical applications (sodium lamps, thermionic converters, magnetohydrodynamic devices, new lasers, 'lithium waterfall' inertial confinement fusion reactors, etc.) are also discussed.

Stwalley, W. C.↗
NASA NTRS1993

Alkali metal carbon dioxide electrochemical system for energy storage and/or conversion of carbon dioxide to oxygen

An alkali metal, such as lithium, is the anodic reactant; carbon dioxide or a mixture of carbon dioxide and carbon monoxide is the cathodic reactant; and carbonate of the alkali metal is the electrolyte in an electrochemical cell for the storage and delivery of electrical energy. Additionally, alkali metal-carbon dioxide battery systems include a plurality of such electrochemical cells. Gold is a preferred catalyst for reducing the carbon dioxide at the cathode. The fuel cell of the invention produces electrochemical energy through the use of an anodic reactant which is extremely energetic and light, and a cathodic reactant which can be extracted from its environment and therefore exacts no transportation penalty. The invention is, therefore, especially useful in extraterrestrial environments.

Hagedorn, Norman H.↗
DOE OSTI2025

Activation of Semicore Electrons in Alkali Metals and Their Role in the B1–B2 Phase Transition under Pressure

Alkali fluorides are often thought of as archetypical ionic compounds whose structures can be understood in terms of the packing of rigid spheres. At ambient pressure, they assume the rocksalt (B1) structure, while under only a few GPa of pressure, the cesium chloride (B2) structure, with higher coordination numbers, is assumed for KF, RbF, and CsF. NaF requires almost 10 times more pressure to undergo this same phase transition, which has not been observed for LiF. Herein, we provide a detailed analysis, based upon quantum chemical calculations, explaining this behavior. We show that for the heavier alkali metals, the semicore p orbitals engage in metal-metal bonding in the B2 phase, facilitating the pressure-induced B1 → B2 structural transition. Furthermore, these findings suggest that the semicore orbitals of heavy alkali metals can be activated without the need of strong oxidants at very mild levels of compression, resulting in the formation of chemical bonds, challenging both traditional and modern core-valence distinctions. In addition, we argue that Cs 5p-5p bonding in CsCl occurs already at ambient pressure, stabilizing the B2 phase, and suggest experiments that may be able to detect signatures of such bonding.

Anions↗
DOE OSTI2025

Alkali Metal Control of Triplet-Mediated C–H Activation in Iron-Mediated Coupling of Dinitrogen and Benzene

Direct coupling of N 2 with abundant feedstocks like benzene to form N-containing organic compounds is a promising strategy for N 2 fixation pathways. The challenge of coupling N 2 activation and C–H bond oxidative addition was recently solved by introducing a reversible benzene C–H bond activation process mediated by a low-valent Fe(0) complex, which gave an organometallic product that could couple with partially reduced N 2 . Interestingly, the energetics of the C–H oxidative addition/reductive elimination step depends on the choice of alkali metal. However, the reason why the alkali metal influences the C–H bond activation remained elusive. In this work, we present a comprehensive study on this Fe(0)-mediated reversible C–H activation. Through density functional theory combined with high-level coupled cluster calculations, we discovered that the intermediate-spin triplet (S = 1) controls the energy of the transition state for C–H cleavage, while the high-spin quintet (S = 2) controls the position of the equilibrium. Na + drives the equilibrium toward oxidative addition due to an electrostatic effect, while K + and Rb + are dominated by a steric effect that favors the iron(0) species. The key role played by nonbonding interactions in the Fe-mediated C–H activation provides a conceptual model for alkali control over organometallic transformations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Alkali Metal Cation Effects on Dinitrogen Complexes and Organometallic Compounds

Alkali metal (AM) cations are often taken for granted as counterions in coordination chemistry and organometallic reactions. However, the AM cation can be more than a bystander in inorganic transformations. This Account focuses on research that has elucidated several types of AM cation effects and how these can be exploited to achieve novel structures and reactivity pathways. Here, a particular focus is on AM cation effects in low-coordinate iron β-diketiminate complexes, though we address general trends and potential applications in systems with other supporting ligands.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

High power density performance of WPt and WRh electrodes in the alkali metal thermoelectric converter

The properties of the alkali metal thermoelectric converter (AMTEC) are discussed together with those of an efficient AMTEC electrode. Three groups of electrodes were prepared and tested for their performance as AMTEC electrodes, including WPt-T3, WRh-B1, and WRh-B2. The best electrodes of both WPt and WRh types typically exhibited low porosity, and thickness greater than 0.8 micron, which indicated that transport in these electrodes does not occur by a purely free-molecular flow mode. The observed values of the exchange current were found to be within the range of those observed for oxide-free Mo electrodes under similar conditions.

Williams, R. M.↗
DOE OSTI2025

Alkali Metal Cation Effects for Rapid C–H Activation by Iron(0) Complexes

C–H oxidative addition is a key reaction in organometallic catalysis, motivating efforts to accelerate it. Here, we examine an anionic beta-diketiminate-supported iron(0) species that was previously observed to activate C-H bonds with Na(15-crown-5), but not with K(18-crown-6) or Rb(18-crown-6). Though crown ethers are usually seen as beneficial due to their ability to solubilize alkali metal cations, we observe that removing the crown ether leads to rapid and complete oxidative addition of the C-H bond even by K, Rb, and Cs. The products are iron(II) phenyl hydride complexes that exist as dimers bridged by the alkali metals. Neutron crystallography of the cesium complex verifies the presence and location of the bridging hydrides. It is likely that the crown-free alkali metal cations have greater Lewis acidity that enables them to facilitate oxidative addition of the C-H bond. This system gives insight on how to control the rate and favorability of C-H activation through manipulation of the countercation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗