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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Automated concentration of [ 18 F]fluoride into microliter volumes

Concentration of [ 18 F]fluoride has been mentioned in literature, however, reports have lacked details about system designs, operation, and performance. Here, we describe in detail a compact, fast, fully-automated concentration system based on a micro-sized strong anion exchange cartridge. The concentration of radionuclides enables scaled-up microfluidic synthesis. Our system can also be used to provide highly concentrated [ 18 F]fluoride with minimal water content. We demonstrate how the concentrator can produce varying concentrations of [ 18 F]fluoride for the macroscale synthesis of N-boc-5-[ 18 F]fluoroindole without an azeotropic drying process, while enabling high starting radioactivity. By appropriate choice of solid-phase resin, flow conditions, and eluent solution, we believe this approach can be extended beyond [ 18 F]fluoride to other radionuclides.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

A low-temperature synthetic route to ternary iron-manganese metal fluorides nanoparticles

Ternary metal fluoride Fe{sub x}Mn{sub 1−x}F{sub 2} (x = 0.00, 0.25, 0.50, 0.75, and 1.00), which is a potential cathode material for next-generation Li-ion batteries, were synthesized via a convenient, low-temperature, bottom-up solution-phase method. The lattice dimensions deduced from X-ray diffraction suggested formation of homogeneous solid solutions. With increasing Fe content, the morphology of the solid changed from cubic particles to dendritic, with an average particle size of 20–40 nm. The results suggested that this synthetic method constitutes a translatable route to large-scale production of ternary metal fluoride nanoparticles. - Graphical abstract: Homogeneous random solid solutions of ternary metal fluoride Fe{sub x}Mn{sub 1−x}F{sub 2} can be prepared by room temperature coprecipitation of precursors followed by drying and calcination at 350 °C. Display Omitted - Highlights: • Homogeneous ternary mixed metal iron-manganese fluoride Fe{sub x}Mn{sub 1−x}F{sub 2} nanoparticles prepared by room temperature coprecipitation and calcination. • Fe{sub x}Mn{sub 1−x}F{sub 2} nanoparticles form different morphology aggregates depending on the composition. • Lattice dimensions from X-ray diffraction suggested formation of homogeneous solid solutions.

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

Choline Fluoride-Ethylene glycol deep eutectic solvent mixture – Synthesis and physicochemical properties

A critical factor in achieving tunability in DESs is varying the type of hydrogen bond acceptors (HBAs) and donors (HBDs). Choline halides (ChX), such as ChCl and ChBr, have been studied to investigate the effect of the choline anion on DESs. However, ChF-based DESs have been underrepresented in scientific research. ChF has excellent potential, such as high electron affinity, ionization potential, and strong hydrogen bond interactions. Moreover, ChF-based DES can lead to a deeper understanding of DESs due to the NMR-active 19F nuclear spin nature. We report the first synthesis and characterization of choline fluoride-EG (1:2, ChF:EG) DES, which we named “EthalineF.” We studied this mixture using various spectroscopic techniques, including NMR, FT-IR, Raman, and UV–vis spectroscopies. Polarity, density, viscosity, and conductivity measurements were collected as well. Transient absorption spectroscopy (TAS) was used to study the solvation dynamics of EthalineF. 19F NMR indicated that some fluoride anions (~15%) are coordinated to the choline cation. In EthalineF, the new type of observed fluoride anions is proposed to be a tight-binding choline-fluoride ion pair. Further, EthalineF has a larger solvodynamic radius than Ethaline. This can explain the lower conductivity for EthalineF compared to Ethaline despite the higher fluidity and solvation dynamics for EthalineF.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Formation and Scrolling Behavior of Metal Fluoride and Oxyfluoride Nanosheets

Here we report 1–2 unit-cell-thick CaF 2 nanosheets, which can be converted topochemically into LaF 3–2 x O x nanosheets that scroll spontaneously. The formation of CaF 2 nanosheets is achieved through interlayer confinement and templating within CaSi 2 during reaction with aqueous HF. The structure and morphology of these nanosheets are characterized by HRTEM, AFM, and powder XRD. Solid-state MAS and solution 19 F NMR spectroscopies provide further information about interstitial fluoride sites within CaF 2 nanosheets as well as help identify side products of the CaSi 2 + HF reaction. CaF 2 nanosheets react with lanthanide salts at room temperature to yield nanostructured hexagonal LnF 3 (Ln = Ce, Pr, Nd, Sm, Eu), orthorhombic LnF 3 (Ln = Gd, Dy, Ho, Er, Yb), and cubic YbF 3– x products. Furthermore, the reaction of CaF 2 nanosheets with lanthanum salts is unique in producing LaF 3–2 x O x . The evidence for this composition includes powder XRD, EDS, XPS, and 19 F NMR data. The structure of LaF 3–2 x O x differs from hexagonal LaF 3 only in the replacement of two fluorides by one oxygen. While this topochemical transformation preserves the two-dimensional morphology it also causes lattice strain that initiates scrolling. The resulting product consists of remarkable ~20 × 5 nm scroll-like tubes of LaF 3–2 x O x that are unique among metal fluoride materials. These results demonstrate novel metal fluoride nanochemistry and a new scrolling mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influence of Polymorphs and Local Defect Structures on NMR Parameters of Graphite Fluorides

In this study, the role of local molecular structure on calculated 13 C and 19 F NMR chemical shifts for graphite fluoride materials was explored by using gauge-including projector augmented wave (GIPAW) computational methods for different periodic crystal polymorphs and density functional theory (DFT) gauge-including atomic orbital (GIAO) computational methods for individual graphite fluoride platelets, i.e., fluorinated graphene (FG). The impact of stacking sequences, d -spacing, and ring conformations on fully fluorinated graphite fluoride structures was investigated. A range of different defects including Stone–Wales, F and C vacancies, void formation, and F inversion were also evaluated using FG structures. These calculations show that distinct chemical shift signatures exist for many of these polymorphs and defects, therefore providing a basis for spectral assignment and development of models describing the mean local CF structure in disordered graphite fluoride materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Generation of Axially Chiral Fluoroallenes through a Copper-Catalyzed Enantioselective β-Fluoride Elimination

Herein we report the copper-catalyzed silylation of propargylic difluorides to generate axially chiral, tetrasubstituted monofluoroallenes in both good yields (27 examples >80%) and enantioselectivities (82-98% ee). Compared to previously reported synthetic routes to axially chiral allenes (ACAs) from prochiral substrates, a mechanistically distinct reaction has been developed: the enantiodiscrimination between enantiotopic fluorides to set an axial stereocenter. DFT calculations and vibrational circular dichroism (VCD) suggest that β-fluoride elimination from an alkenyl copper intermediate likely proceeds through a syn -β-fluoride elimination pathway rather than an anti -elimination pathway. The effects of the C1-symmetric Josiphos-derived ligand on reactivity and enantioselectivity were investigated. Not only does this report showcase that alkenyl copper species (like their alkyl counterparts) can undergo β-fluoride elimination, but this elimination can be achieved in an enantioselective fashion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

High Energy-Density and Reversibility of Iron Fluoride Cathode Enabled Via an Intercalation-Extrusion Reaction

Iron fluoride, an intercalation-conversion cathode for lithium ion batteries, promises a high theoretical energy density of 1922 Wh Kg –1 . However, poor electrochemical reversibility due to repeated breaking/reformation of metal-fluoride bonds poses a grand challenge for its practical application. Here we report that both a high reversibility over 1000 cycles and a high capacity of 420 mAh g –1 can be realized by concerted doping of cobalt and oxygen into iron fluoride. In the doped nanorods, an energy density of ~1000 Wh Kg –1 with a decay rate of 0.03% per cycle is achieved. The anion and cation’s co-substitutions thermodynamically reduce conversion-reaction potential and shift the reaction from less reversible intercalation-conversion reaction in iron fluoride to a highly reversible intercalation-extrusion reaction in doped material. Furthermore, the co-substitution strategy to tune the thermodynamic features of the reactions could be extended to other high energy conversion materials for improved performance.

25 ENERGY STORAGE↗
DOE OSTI2022

New High-Strength Ni-based Alloys for High Temperature Service in Liquid Fluoride Salt Environments

The ever-increasing demand for higher system thermal efficiency necessitates the operation of power generation cycles and heat conversion systems for chemical processes at progressively higher temperatures. As the system operating temperature increases, fewer and fewer materials are available with the required mechanical properties and environmental compatibility. This dearth of materials is particularly acute in structural applications at temperatures above 700°C in liquid Fluoride Salt Cooled High-Temperature Reactors (FHRs) and Concentrated Solar Power (CSP) systems where liquid fluoride and/or liquid chloride salts are used for their high thermal capacity and low thermal conductivity to store and transport heat. It has been shown that fluorides and chlorides can degrade the properties of the material used for storage and transport due to corrosive effects thus affecting the performance and lifetime characteristics. Thus, materials used for storage and transport for fluoride/chloride-salt must at the minimum have good compatibility with the salt by exhibiting low corrosion rates at the required temperatures. In addition, since many of the components will be subject to stresses in service, they need to have sufficient strength to resist plastic deformation, and the resistance to time dependent creep deformation at these temperatures, and stress levels. Achieving the combination of these properties required for higher temperatures is particularly challenging considering traditionally, the expected lifetime of some of the components used in these systems are from 30 years (CSP) to 80 years (FHRs). Although 316 stainless steel and associated redox corrosion reduction techniques are being considered for use in the first generational systems, use of 316SS is limited to operating temperatures up to ~ 650°C, thereby resulting in lower reactor efficiencies. Hastelloy ® N, developed at ORNL in the 1950s-60s for molten salt service is currently the leading candidate FHR structural alloy but has inadequate creep properties at high temperatures. Using a computationally-guided approach, Oak Ridge National Laboratory had developed new high strength alloys strengthened by γ’ precipitates (about 2X the strength of Hastelloy ® N) in small laboratory-scale heats that show good resistance to corrosion by fluorides and improved creep rupture life at temperatures up to 850°C (U.S. Patent Application No. 13/833,357 entitled “High Strength Alloys for High Temperature Service in Liquid-Salt Cooled Energy Systems”- granted U. S. Patent No. 9,540,714).

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1972

Graphite fluoride as a solid lubricant in a polyimide binder

Polyimide resin (PI) was shown to be a suitable binder material for the solid lubricant graphite fluoride, (CF(1.1))n. Comparisons were made to similar tests using PI-bonded MOS2 films, graphite fluoride rubbed films, and MOS2 rubbed films. The results showed that, at any one specific temperature between 25 and 400 C, the wear life of PI-bonded graphite fluoride films exceeded those of the other three films by at least a factor of 2 and by as much as a factor of 60. Minimum friction coefficients for the PI-bonded films were 0.08 for graphite fluoride and 0.04 for MOS2. The rider wear rates for the two PI-bonded films at 25 C were nearly equal.

Fusaro, R. L.↗
NASA NTRS1974

Tribological properties of self-lubricating fluoride-metal composites to 900 C (1650 F): A review and some new developments

The friction and wear behavior of some fluoride-metal, self-lubricating composites are summarized. Fluoride-infiltrated sintered nickel alloy composites and plasma-sprayed, co-deposited fluoride-nickel alloy composites are described. The importance of proper surface-conditioning of the composites is stressed. Performance of fluoride-metal composites in some machine application evaluation is discussed.

Sliney, H. E.↗
NASA NTRS1988

Fluoride glass: Crystallization, surface tension

Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.

Doremus, R. H.↗
NASA NTRS1971

The Determination of Atmospheric Fluoride with a Specific Ion Electrode

Atmospheric fluoride is collected on lime-coated filter paper exposed to the ambient atmosphere for 30-day periods. The fluoride is eluted from the paper and analyzed with the use of a fluoride specific ion electrode. The technique permits evaluation of potential fluoride sources in terms of downwind concentrations and provides a simple, rapid procedure for the analysis of large numbers of samples.

Feldstein, M.↗
NASA NTRS2007

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

electrolytes↗
DOE OSTI2024

Systems and methods for fluoride ceramic phosphors for LED lighting

The present disclosure relates to a lighting component which may comprise a light emitting diode (LED) or laser diode (LD) for generating at least one of blue light or ultraviolet light. A fluoride phosphor matrix may be included, which may be consolidated into a phosphor ceramic structure including at least one of a transparent fluoride ceramic structure or a translucent fluoride ceramic structure, and positioned adjacent to the LED or LD. The phosphor ceramic structure generates at least one of red or orange light when irradiated by the light emitted from the LED or LD. The phosphor ceramic structure exhibits reduced thermal quenching relative to a fluoride particulate structure irradiated by the LED or LD.

Cherepy, Nerine↗
DOE OSTI2018

Manufacturing of Dysprosium-Iron Alloys by Electrolysis in Fluoride-Based Electrolytes: Oxide Solubility Determinations

Electrolytic production of light rare earth elements and alloys takes place in a fluoride-based electrolyte using rare earth oxides as raw material. The optimization of this method, mainly in terms of the energy efficiency and environmental impact control, is rather challenging. Anode effects, evolution of fluorine-containing compounds, and side cathode reactions could largely be minimized by a good control of the amount of rare earth oxide species dissolved in the fluoride-based electrolyte and their dissolution rate. The oxide content of the fluoride melts REF{sub 3}-LiF (RE = Nd, Dy) at different compositions and temperatures were experimentally determined by carbothermal analysis of melt samples. The highest solubility values of oxide species, added as Dy{sub 2}O{sub 3} and Dy{sub 2}(CO{sub 3}){sub 3}, were obtained to be of ca. 3 wt pct (expressed as Dy{sub 2}O{sub 3}) in the case of the equimolar DyF{sub 3}-LiF melt at 1323 K (1050 °C). The oxide saturation values increased with the amount of REF{sub 3} present in the molten bath and the working temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Photochemical Degradation of Curcumin: a Mechanism for Aqueous Based Sensing of Fluoride

The present work describes the enhanced photochemical degradation of natural dye Curcumin in acetonitrile–water mixture in the presence of fluoride upon irradiation with light. The strong basicity of fluoride modifies the solvent environment around Curcumin molecule leading to alkaline mediated degradation of Curcumin which is further accelerated by irradiation with light. The photochemical degradation of Curcumin is studied using absorption and fluorescence spectroscopy and verified using infrared spectroscopy and fluorescence lifetime studies. The results of the work indicate that the method of Curcumin irradiation can be used as a sensing technique for fluoride detection in a wide range.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Thermochemistry of sodium rare earth ternary fluorides, NaREF 4

Sodium rare earth fluorides, NaREF 4 (RE = rare earth), are used as luminescent materials for light emission and biomedical applications and are important compositions for extracting and separating RE elements. Solution calorimetric measurements of a series of β-structured NaREF 4 (Na 1.5 RE 1.5 F 6 ) phases with various RE elements determined their heats of formation. Though the lattice contracts from light to heavy RE elements, NaREF 4 compounds show more exothermic enthalpies of formation from binary components with the decrease of RE 3+ radii, contrary to behavior seen in most RE oxide ternary compounds. Furthermore, by constructing Born–Haber cycles, the different slopes of lines relating lattice energies to lattice parameters in binary and ternary fluorides appear to be the reason for this reverse trend, which can be associated with changes in the coordination number of RE cations. These trends and the metastability of sodium light RE fluorides not only reveal the key role of ionic radius in RE compound stability, but also are significant for the design and synthesis of new materials and motivate the more effective utilization of RE.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Direct observation of Nd{sup 3+} and Tm{sup 3+} ion distributions in oxy-fluoride glass ceramics containing PbF{sub 2} nanocrystals

Nd{sup 3+} and Tm{sup 3+}, doped oxy-fluoride glasses and glass ceramics were prepared by conventional melt-quenching and subsequent heat-treatment, respectively. β-PbF{sub 2} nanocrystals with diameter 50 –100 nm formed in the glass matrix after heat treatment. The Stark splitting in absorption peaks, enhanced photoluminescence and prolonged lifetimes that β-PbF{sub 2} nanocrystal formation increased the luminescence of rare earth ions. Both Nd{sup 3+} and Tm{sup 3+} ions were incorporated into nanocrystals that were enriched in lead and fluorine, and deficient in oxygen. - Highlights: • EELS analysis for rare-earth ion distribution in oxy-fluoride glass ceramics • No significant changes in lifetimes of Nd{sup 3+}, while obvious change for Tm{sup 3+} • Direct evidence of Nd{sup 3+} and Tm{sup 3+} aggregation into fluoride nanocrystals.

36 MATERIALS SCIENCE↗