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Sample records for alkali-metal vapor density

  1. Faraday rotation density measurements of optically thick alkali metal vapors

    NASA Astrophysics Data System (ADS)

    Vliegen, E.; Kadlecek, S.; Anderson, L. W.; Walker, T. G.; Erickson, C. J.; Happer, William

    2001-03-01

    We investigate the measurement of alkali number densities using the Faraday rotation of linearly polarized light. We find that the alkali number density may be reliably extracted even in regimes of very high buffer gas pressure, and very high alkali number density. We have directly verified our results in potassium using absorption spectroscopy on the second resonance (4 2S→5 2P).

  2. Effects of spin-exchange collisions in a high-density alkali-metal vapor in low magnetic fields

    SciTech Connect

    Savukov, I.M.; Romalis, M.V.

    2005-02-01

    Spin-exchange collisions often play a dominant role in the broadening of Zeeman resonances in an alkali-metal vapor. Contrary to intuitive expectations, at high alkali-metal densities this broadening can be completely eliminated by operating in a low magnetic field, allowing construction of ultrasensitive atomic magnetometers. We describe a detailed study of the Zeeman resonance frequencies and linewidths as a function of the magnetic field, alkali-metal density, and the degree of spin polarization of the atoms. Due to the nonlinear nature of the density matrix equations describing the spin-exchange collisions both the gyromagnetic ratio and the linewidth change as a function of the polarization. The results of experimental measurements are in excellent agreement with analytical and numerical solutions of the density matrix equations.

  3. Integrating Sphere Alkali-Metal Vapor Cells

    NASA Astrophysics Data System (ADS)

    McGuyer, Bart; Ben-Kish, Amit; Jau, Yuan-Yu; Happer, William

    2010-03-01

    An integrating sphere is an optical multi-pass cavity that uses diffuse reflection to increase the optical path length. Typically applied in photometry and radiometry, integrating spheres have previously been used to detect trace gases and to cool and trap alkali-metal atoms. Here, we investigate the potential for integrating spheres to enhance optical absorption in optically thin alkali-metal vapor cells. In particular, we consider the importance of dielectric effects due to a glass container for the alkali-metal vapor. Potential applications include miniature atomic clocks and magnetometers, where multi-passing could reduce the operating temperature and power consumption.

  4. Alkali metal vapors - Laser spectroscopy and applications

    NASA Technical Reports Server (NTRS)

    Stwalley, W. C.; Koch, M. E.

    1980-01-01

    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.

  5. (abstract) Fundamental Mechanisms of Electrode Kinetics and Alkali Metal Atom Transport at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S. K.

    1993-01-01

    The mechanisms of electrode kinetics and mass transport of alkali metal oxidation and alkali metal cation reduction at the solid electrolyte/porous electrode boundary as well as alkali metal transport through porous metal electrodes has important applications in optimizing device performance in alkali metal thermal to electric converter (AMTEC) cells which are high temperature, high current density electrochemical cells. Basic studies of these processes also affords the opportunity to investigate a very basic electrochemical reaction over a wide range of conditions; and a variety of mass transport modes at high temperatures via electrochemical techniques. The temperature range of these investigations covers 700K to 1240K; the alkali metal vapor pressures range from about 10(sup -2) to 10(sup 2) Pa; and electrodes studied have included Mo, W, Mo/Na(sub 2)MoO(sub 4), W/Na(sub 2)WO(sub 4), WPt(sub x), and WRh(sub x) (1.0 < x < 6.0 ) with Na at Na-beta'-alumina, and Mo with K at K-beta'-alumina. Both liquid metal/solid electrolyte/alkali metal vapor and alkali metal vapor/solid electrolyte/vapor cells have been used to characterize the reaction and transport processes. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes.

  6. Spill-Resistant Alkali-Metal-Vapor Dispenser

    NASA Technical Reports Server (NTRS)

    Klipstein, William

    2005-01-01

    A spill-resistant vessel has been developed for dispensing an alkali-metal vapor. Vapors of alkali metals (most commonly, cesium or rubidium, both of which melt at temperatures slightly above room temperature) are needed for atomic frequency standards, experiments in spectroscopy, and experiments in laser cooling. Although the present spill-resistant alkali-metal dispenser was originally intended for use in the low-gravity environment of outer space, it can also be used in normal Earth gravitation: indeed, its utility as a vapor source was confirmed by use of cesium in a ground apparatus. The vessel is made of copper. It consists of an assembly of cylinders and flanges, shown in the figure. The uppermost cylinder is a fill tube. Initially, the vessel is evacuated, the alkali metal charge is distilled into the bottom of the vessel, and then the fill tube is pinched closed to form a vacuum seal. The innermost cylinder serves as the outlet for the vapor, yet prevents spilling by protruding above the surface of the alkali metal, no matter which way or how far the vessel is tilted. In the event (unlikely in normal Earth gravitation) that any drops of molten alkali metal have been shaken loose by vibration and are floating freely, a mesh cap on top of the inner cylinder prevents the drops from drifting out with the vapor. Liquid containment of the equivalent of 1.2 grams of cesium was confirmed for all orientations with rubbing alcohol in one of the prototypes later used with cesium.

  7. On-chip fabrication of alkali-metal vapor cells utilizing an alkali-metal source tablet

    NASA Astrophysics Data System (ADS)

    Tsujimoto, K.; Ban, K.; Hirai, Y.; Sugano, K.; Tsuchiya, T.; Mizutani, N.; Tabata, O.

    2013-11-01

    We describe a novel on-chip microfabrication technique for the alkali-metal vapor cell of an optically pumped atomic magnetometer (OPAM), utilizing an alkali-metal source tablet (AMST). The newly proposed AMST is a millimeter-sized piece of porous alumina whose considerable surface area holds deposited alkali-metal chloride (KCl) and barium azide (BaN6), source materials that effectively produce alkali-metal vapor at less than 400 °C. Our experiments indicated that the most effective pore size of the AMST is between 60 and 170 µm. The thickness of an insulating glass spacer holding the AMST was designed to confine generated alkali metal to the interior of the vapor cell during its production, and an integrated silicon heater was designed to seal the device using a glass frit, melted at an optimum temperature range of 460-490 °C that was determined by finite element method thermal simulation. The proposed design and AMST were used to successfully fabricate a K cell that was then operated as an OPAM with a measured sensitivity of 50 pT. These results demonstrate that the proposed concept for on-chip microfabrication of alkali-metal vapor cells may lead to effective replacement of conventional glassworking approaches.

  8. Solar-powered alkali metal vapor lasers

    NASA Technical Reports Server (NTRS)

    Blount, Charles E.

    1989-01-01

    The emission spectrum of the A(1 Sigma u +) - X(1 Sigma g +) band of Na2 has been recorded following excitation by monochromatic radiation in the region of X-A and X-B absorption. The spectral profile has been investigated as a function of excitation wavelength, sodium vapor temperature and buffer gas pressure. Additionally, gain measurements were made for the satellite of the A-X band as a function of the sodium vapor temperature and buffer gas pressure.

  9. Magnetic Resonance Reversals in Optically Pumped Alkali-Metal Vapor

    NASA Astrophysics Data System (ADS)

    Gong, Fei; Jau, Yuan-Yu; Happer, William

    2007-06-01

    We report an unusual new phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the ``zero-dip" resonance (Zeeman resonance at zero field) of optically-pumped, alkali-metal vapors. These anomalies occur when a ``weak" circular polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in simple, semi-quantitative way with reference to this distribution. uantitative computer simulations are in excellent greement with observations.

  10. Magnetic resonance reversals in optically pumped alkali-metal vapor

    NASA Astrophysics Data System (ADS)

    Gong, F.; Jau, Y.-Y.; Happer, W.

    2007-05-01

    We report an unusual phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the zero-dip resonance (Zeeman resonance at zero field) of optically pumped, alkali-metal vapors. These anomalies occur when a weak circularly polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in a simple, semiquantitative way with reference to the spin-temperature distribution. Quantitative computer simulations are in excellent agreement with observations.

  11. Spin-exchange frequency shift in alkali-metal-vapor cell frequency standards

    SciTech Connect

    Micalizio, Salvatore; Godone, Aldo; Levi, Filippo; Vanier, Jacques

    2006-03-15

    In this paper we calculate the effect of spin-exchange collisions in alkali-metal vapors. In the framework of the high-energy approximation, we evaluate the spin-exchange cross sections related to the line broadening and to the frequency shift of the ground state hyperfine transition. We do the calculation for the four isotopes, {sup 23}Na, {sup 39}K, {sup 87}Rb, and {sup 133}Cs. The results are used in particular to evaluate the spin-exchange frequency shift in Rb vapor cell frequency standards used in many applications. It turns out that, due to possible fluctuations in the atomic density, spin exchange may affect significantly the medium and long term frequency stability of the frequency standard.

  12. Saturated vapor pressure above the amalgam of alkali metals in discharge lamps

    NASA Astrophysics Data System (ADS)

    Gavrish, S. V.

    2011-12-01

    A theoretical and numerical analysis of the evaporation process of two-component compounds in vapors of alkali metals in discharge lamps is presented. Based on the developed mathematical model of calculation of saturated vapor pressure of the metal above the amalgam, dependences of mass fractions of the components in the discharge volume on design parameters and thermophysical characteristics of the lamp are obtained.

  13. [The Measuring Method of Atomic Polarization of Alkali Metal Vapor Based on Optical Rotation and the Analysis of the Influence Factors].

    PubMed

    Shang, Hui-ning; Quan, Wei; Chen, Yao; Li, Yang; Li, Hong

    2016-02-01

    High sensitivity measurements of inertia and magnetic field could be achieved by utilizing a category of devices, which manipulate the atomic spins in the spin-exchange-relaxation-free regime. The alkali cell which contains the alkali metal vapor is used to sense magnetic field and inertia. The atomic number density of alkali vapor and the polarization of alkali metal vapor are two of the most important parameters of the cell. They play an important role in the research on atomic spins in the spin-exchange-relaxation-free regime. Besides, optical polarization plays an important role in quantum computing and atomic physics. We propose a measurement of alkali vapor polarization and alkali number density by detecting the optical rotation in one system. This method simplifies existing experimental equipment and processes. A constant bias magnetic field is applied and the Faraday rotation angle is detected by a bunch of the probe beam to deduce alkali-metal density. Then the magnetic field is closed and a bunch of the pump laser is utilized to polarize alkali-metal. Again, the probe beam is utilized to obtain the polarization of alkali metal. The alkali density obtained at first is used to deduce the polarization. This paper applies a numerical method to analyze the Faraday rotation and the polarization rotation. According to the numerical method, the optimal wavelength for the experiment is given. Finally, the fluctuation of magnetic field and wavelength on signal analysis are analyzed. PMID:27209720

  14. Ab Initio Molecular Dynamics of Dimerization and Clustering in Alkali Metal Vapors.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2016-06-30

    Alkali metals are known to form dimers, trimers, and tetramers in their vapors. The mechanism and regularities of this phenomenon characterize the chemical behavior of the first group elements. We report ab initio molecular dynamics (AIMD) simulations of the alkali metal vapors and characterize their structural properties, including radial distribution functions and atomic cluster size distributions. AIMD confirms formation of Men, where n ranges from 2 to 4. High pressure sharply favors larger structures, whereas high temperature decreases their fraction. Heavier alkali metals maintain somewhat larger fractions of Me2, Me3, and Me4, relative to isolated atoms. A single atom is the most frequently observed structure in vapors, irrespective of the element and temperature. Due to technical difficulties of working with high temperatures and pressures in experiments, AIMD is the most affordable method of research. It provides valuable understanding of the chemical behavior of Li, Na, K, Rb, and Cs, which can lead to development of new chemical reactions involving these metals. PMID:27294399

  15. Investigation of anti-Relaxation coatings for alkali-metal vapor cells using surface science techniques

    SciTech Connect

    Seltzer, S. J.; Michalak, D. J.; Donaldson, M. H.; Balabas, M. V.; Barber, S. K.; Bernasek, S. L.; Bouchiat, M.-A.; Hexemer, A.; Hibberd, A. M.; Jackson Kimball, D. F.; Jaye, C.; Karaulanov, T.; Narducci, F. A.; Rangwala, S. A.; Robinson, H. G.; Shmakov, A. K.; Voronov, D. L.; Yashchuk, V. V.; Pines, A.; Budker, D.

    2010-10-11

    Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10?000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C=C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials.

  16. PROCESS OF RECOVERING ALKALI METALS

    DOEpatents

    Wolkoff, J.

    1961-08-15

    A process is described of recovering alkali metal vapor by sorption on activated alumina, activated carbon, dehydrated zeolite, activated magnesia, or Fuller's earth preheated above the vaporization temperature of the alkali metal and subsequent desorption by heating the solvent under vacuum. (AEC)

  17. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Quarterly report, April-June 1980

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.; Boyd, W.A.

    1980-07-01

    In the application of pressurized fluidized-bed combustors (PFBC) to the generation of electricity, hot corrosion of gas turbine components by alkali metal compounds is a potential problem. The objective of this investigation is to develop a method for removing these gaseous alkali metal compounds from the high-pressure high-temperature gas from a PFBC before the gas enters the gas turbine. A granular-bed filter, using either diatomaceous earth or activated bauxite as the bed material, is the concept currently being studied. Results are presented for the testing of diatomaceous earth for alkali vapor sorption at 800/sup 0/C and 9-atm pressure, using a simulated flue gas. Activated bauxite sorbent can be regenerated by leaching with water, and the kinetics of the leaching is under study.

  18. New studies of optical pumping, spin resonances, and spin exchange in mixtures of inert gases and alkali-metal vapors

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu

    In this thesis, we present new studies of alkali-hyperfine resonances, new optical pumping of alkali-metal atoms, and the new measurements of binary spin-exchange cross-section between alkali-metal atoms and xenon atoms. We report a large light narrowing effect of the hyperfine end-resonance signals, which was predicted from our theory and observed in our experiments. By increasing the intensity of the circularly polarized pumping beam, alkali-metal atoms are optically pumped into a state of static polarization, and trapped into the hyperfine end-state. Spin exchange between alkali-metal atoms has minimal effect on the end-resonance of the highly spin-polarized atoms. This new result will possibly benefit the design of atomic clocks and magnetometer. We also studied the pressure dependence of the atomic-clock resonance linewidth and pointed out that the linewidth was overestimated by people in the community of atomic clock. Next, we present a series study of coherent population trapping (CPT), which is a promising technique with the same or better performance compared to the traditional microwave spectroscopy. For miniature atomic clocks, CPT method is thought to be particularly advantages. From our studies, we invented a new optical-pumping method, push-pull optical pumping, which can pump atoms into nearly pure 0-0 superposition state, the superposition state of the two ground-state hyperfine sublevels with azimuthal quantum number m = 0. We believe this new invention will bring a big advantage to CPT frequency standards, the quantum state preparation for cold atoms or hot vapor, etc. We also investigated the pressure dependence of CPT excitation and the line shape of the CPT resonance theoretically and experimentally. These two properties are important for CPT applications. A theoretical study of "photon cost" of optical pumping is also presented. Finally, we switch our attention to the problem of spin exchange between alkali-metal atoms and xenon gas. This

  19. Buffer-gas-induced shift and broadening of hyperfine resonances in alkali-metal vapors

    NASA Astrophysics Data System (ADS)

    Oreto, P. J.; Jau, Y.-Y.; Post, A. B.; Kuzma, N. N.; Happer, W.

    2004-04-01

    We review the shift and broadening of hyperfine resonance lines of alkali-metal atoms in buffer gases. We present a simple theory both for the shift and the broadening induced by He gas. The theory is parametrized by the scattering length of slow electrons on He atoms and by the measured hyperfine intervals and binding energies of the S states of alkali-metal atoms. The calculated shifts and their temperature dependence are in good agreement with the published experimental data. The calculated broadening is 1.6 times smaller than the recent measurements, and more than 20 times smaller than the earlier measurements. We attribute much of the linewidth in the earlier experiments to possible small temperature gradients and the resulting inhomogeneous line broadening from the temperature dependence of hyperfine frequency shift at constant buffer-gas pressure.

  20. Alkali metal ionization detector

    DOEpatents

    Bauerle, James E.; Reed, William H.; Berkey, Edgar

    1978-01-01

    Variations in the conventional filament and collector electrodes of an alkali metal ionization detector, including the substitution of helical electrode configurations for either the conventional wire filament or flat plate collector; or, the substitution of a plurality of discrete filament electrodes providing an in situ capability for transferring from an operationally defective filament electrode to a previously unused filament electrode without removing the alkali metal ionization detector from the monitored environment. In particular, the helical collector arrangement which is coaxially disposed about the filament electrode, i.e. the thermal ionizer, provides an improved collection of positive ions developed by the filament electrode. The helical filament design, on the other hand, provides the advantage of an increased surface area for ionization of alkali metal-bearing species in a monitored gas environment as well as providing a relatively strong electric field for collecting the ions at the collector electrode about which the helical filament electrode is coaxially positioned. Alternatively, both the filament and collector electrodes can be helical. Furthermore, the operation of the conventional alkali metal ionization detector as a leak detector can be simplified as to cost and complexity, by operating the detector at a reduced collector potential while maintaining the sensitivity of the alkali metal ionization detector adequate for the relatively low concentration of alkali vapor and aerosol typically encountered in leak detection applications.

  1. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating

    NASA Astrophysics Data System (ADS)

    Tretiak, O. Yu.; Blanchard, J. W.; Budker, D.; Olshin, P. K.; Smirnov, S. N.; Balabas, M. V.

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene.

  2. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating.

    PubMed

    Tretiak, O Yu; Blanchard, J W; Budker, D; Olshin, P K; Smirnov, S N; Balabas, M V

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene. PMID:26957176

  3. [Measurement of Mole Ratio for Alkali Metal Mixture by Using Spectral Absorption Method].

    PubMed

    Zou, Sheng; Zhang, Hong; Chen, Yao; Chen, Xi-yuan

    2015-08-01

    The ratio of alkali metal mixture is one of the most important parameters in gauge head belonging to the ultra-sensitivity inertial measurement equipment, which is required to detect precisely. According to the feature that ratio of alkali metal is related to alkali metal vapor density, the theory of optical depth is used to detect the ratio of alkali metal in the present article. The result shows that the data got by the theory of optical depth compared with empirical formula differs at three orders of magnitude, which can't ensure the accuracy. By changing the data processing method, model between spectral absorption rate and temperature in cell is established. The temperature in alkali metal cell is calibrated by spectral absorption rate. The ratio of alkali metal atoms in the cell is analyzed by calculating the alkali density with empirical formula. The computational error is less than 10%. PMID:26672309

  4. Sub-Shot-Noise Magnetometry with a Correlated Spin-Relaxation Dominated Alkali-Metal Vapor

    SciTech Connect

    Kominis, I. K.

    2008-02-22

    Spin noise sets fundamental limits to the precision of measurements using spin-polarized atomic vapors, such as performed with sensitive atomic magnetometers. Spin squeezing offers the possibility to extend the measurement precision beyond the standard quantum limit of uncorrelated atoms. Contrary to current understanding, we show that, even in the presence of spin relaxation, spin squeezing can lead to a significant reduction of spin noise, and hence an increase in magnetometric sensitivity, for a long measurement time. This is the case when correlated spin relaxation due to binary alkali-atom collisions dominates independently acting decoherence processes, a situation realized in thermal high atom-density magnetometers and clocks.

  5. Alkali metal for ultraviolet band-pass filter

    NASA Technical Reports Server (NTRS)

    Mardesich, Nick (Inventor); Fraschetti, George A. (Inventor); Mccann, Timothy A. (Inventor); Mayall, Sherwood D. (Inventor); Dunn, Donald E. (Inventor); Trauger, John T. (Inventor)

    1993-01-01

    An alkali metal filter having a layer of metallic bismuth deposited onto the alkali metal is provided. The metallic bismuth acts to stabilize the surface of the alkali metal to prevent substantial surface migration from occurring on the alkali metal, which may degrade optical characteristics of the filter. To this end, a layer of metallic bismuth is deposited by vapor deposition over the alkali metal to a depth of approximately 5 to 10 A. A complete alkali metal filter is described along with a method for fabricating the alkali metal filter.

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

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Underwood, M. L.; Wheeler, B. L.; Loveland, M. E.; Kikkert, S. J.; Lamb, J. L.; Cole, T.; Kummer, J. T.; Bankston, C. P.

    1989-01-01

    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.

  7. Alkali metal sources for OLED devices

    NASA Astrophysics Data System (ADS)

    Cattaneo, Lorena; Longoni, Giorgio; Bonucci, Antonio; Tominetti, Stefano

    2005-07-01

    In OLED organic layers electron injection is improved by using alkali metals as cathodes, to lower work function or, as dopants of organic layer at cathode interface. The creation of an alkali metal layer can be accomplished through conventional physical vapor deposition from a heated dispenser. However alkali metals are very reactive and must be handled in inert atmosphere all through the entire process. If a contamination takes place, it reduces the lithium deposition rate and also the lithium total yield in a not controlled way. An innovative alkali metal dispensing technology has been developed to overcome these problems and ensure OLED alkali metal cathode reliability. The alkali Metal dispenser, called Alkamax, will be able to release up to a few grams of alkali metals (in particular Li and Cs) throughout the adoption of a very stable form of the alkali metal. Lithium, for example, can be evaporated "on demand": the evaporation could be stopped and re-activated without losing alkali metal yield because the metal not yet consumed remains in its stable form. A full characterization of dispensing material, dispenser configuration and dispensing process has been carried out in order to optimize the evaporation and deposition dynamics of alkali metals layers. The study has been performed applying also inside developed simulations tools.

  8. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

    A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of purified alkali metal nitrates.

  9. Hybrid Optical Pumping of Optically Dense Alkali-Metal Vapor without Quenching Gas

    SciTech Connect

    Romalis, M. V.

    2010-12-10

    Optical pumping of an optically thick atomic vapor typically requires a quenching buffer gas, such as N{sub 2}, to prevent radiation trapping of unpolarized photons which would depolarize the atoms. We show that optical pumping of a trace contamination of Rb present in K metal results in a 4.5 times higher polarization of K than direct optical pumping of K in the absence of N{sub 2}. Such spin-exchange polarization transfer from optically thin species is useful in a variety of areas, including spin-polarized nuclear scattering targets and electron beams, quantum-nondemolition spin measurements, and ultrasensitive magnetometry.

  10. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

  11. Study of complexation between two 1,3-alternate calix[4]crown derivatives and alkali metal ions by electrospray ionization mass spectrometry and density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Shamsipur, Mojtaba; Allahyari, Leila; Fasihi, Javad; Taherpour, Avat (Arman); Asfari, Zuhair; Valinejad, Azizollah

    2016-03-01

    Complexation of two 1,3-alternate calix[4]crown ligands with alkali metals (K+, Rb+ and Cs+) has been investigated by electrospray ionization mass spectrometry (ESI-MS) and density functional theory calculations. The binding selectivities of the ligands and the binding constants of their complexes in solution have been determined using the obtained mass spectra. Also the percentage of each formed complex species in the mixture of each ligand and alkali metal has been experimentally evaluated. For both calix[4]crown-5 and calix[4]crown-6 ligands the experimental and theoretical selectivity of their alkali metal complexes found to follow the trend K+ > Rb+ > Cs+. The structures of ligands were optimized by DFT-B3LYP/6-31G method and the structures of complexes were obtained by QM-SCF-MO/PM6 method and discussed in the text.

  12. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Annual report, October 1979-September 1980

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.

    1980-10-01

    In the application of pressurized fluidized-bed combustion (PFBC) to the generation of electricity, hot corrosion of the gas turbine (downstream from the combustor) by alkali metal compounds is a potential problem. The objective of this investigation is to develop a method for the removal of gaseous alkali metal compounds from the high-pressure high-temperature gas from a PFBC before the gas enters the gas turbine. The use of a granular bed filter, with either diatomaceous earth or activated bauxite as the bed material, is under study. Breakthrough data are reported on the sorption of gaseous NaCl by activated bauxite. Results are reported for the regeneration of activated bauxite using water leaching and a thermal swing method.

  13. Effect of charge density in chain extension reactions involving complexes of 4, 4'-diaminodiphenylmethane and various alkali metal salts

    NASA Astrophysics Data System (ADS)

    Deshmukh, Subrajeet; Carrasquillo, Katherine; Tsai, Fang Chang; Wu, Lina; Hsu, Shaw Ling; University of Massachusetts Amherst Team

    Controlling the reaction of methylene diphenyl diisocyanate (MDI)-terminated polyester prepolymer and 4, 4'-diaminodiphenylmethane (MDA) is extremely important in many large scale applications. The ion-diamine complex has the advantage of blocking the instantaneous reaction between the diamine and isocyanate from taking place until it is released at elevated temperatures. We synthesized complexes of MDA with various alkali metal salts. These complexes create a barrier between the diamine and isocyanate thus preventing the premature reaction. We compared the complexes in terms of their dissociation and the subsequent curing with the prepolymer. Charge density had a tremendous effect. DSC showed that Na complexes dissociated at a lower temperature and needed less energy to dissociate than the Li complexes. The effect of change in cation on complex dissociation was more pronounced compared to the change in anion. Also, the ionic liquid introduced greatly altered the dissociation behavior. Temperature and time resolved IR spectroscopy was used to monitor the urea and NH band. By DSC and IR, we showed that NaCl complex is best suited for the curing of prepolymer with regards to curing temperature and energy.

  14. Alkali metal vapor removal from pressurized fluidized-bed combustor flue gas. Quarterly report, October-December 1979

    SciTech Connect

    Johnson, I.; Swift, W.M.; Lee, S.H.D.; Jonke, A.A.

    1980-07-01

    This work supports the program to develop methods for the cleanup of combustion gases from pressurized fluidized-bed coal combustors so that the cleaned gases can be used for downstream gas turbines. This report presents the results of studies to develop granular sorbents for removing gaseous alkali metal compounds from high-temperature high-pressure combustion gases. Activated bauxite, one of the sorbents found to be effective, can be reused after removal of the alkali compound by a water-leaching process. Results of testing of this leaching process are reported. An experimental appartus for testing sorbents at high pressure has been built; results of preliminary tests are reported.

  15. Density functional study of isoguanine tetrad and pentad sandwich complexes with alkali metal ions.

    PubMed

    Meyer, Michael; Steinke, Thomas; Sühnel, Jürgen

    2007-02-01

    Isoguanine tetraplexes and pentaplexes contain two or more stacked polyads with intercalating metal ions. We report here the results of a density functional study of sandwiched isoguanine tetrad and pentad complexes consisting of two polyads with Na(+), K(+) and Rb(+) ions at the B3LYP level. In comparison to single polyad metal ion complexes, there is a trend towards increased non-planarity of the polyads in the sandwich complexes. In general, the pentad sandwiches have relatively planar polyad structures, whereas the tetrad complexes contain highly non-planar polyad building blocks. As in other sandwich complexes and in metal ion complexes with single polyads, the metal ion-base interaction energy plays an essential role. In iG sandwich structures, this interaction energy is slightly larger than in the corresponding guanine sandwich complexes. Because the base-base interaction energy is even more increased in passing from guanine to isoguanine, the isoguanine sandwiches are thus far the only examples where the base-base interaction energy is larger than the base-metal ion interaction energy. Stacking interactions have been studied in smaller models consisting of two bases, retaining the geometry from the complete complex structures. From the data obtained at the B3LYP and BH&H levels and with Møller-Plesset perturbation theory, one can conclude that the B3LYP method overestimates the repulsion in stacked base dimers. For the complexes studied in this work, this is only of minor importance because the direct inter-tetrad or inter-pentad interaction is supplemented by a strong metal ion-base interaction. Using a microsolvation model, the metal ion preference K(+) approximately Rb(+) > Na(+) is found for tetrad complexes. On the other hand, for pentads the ordering is Rb(+) > K(+) > Na(+). In the latter case experimental data are available that agree with this prediction. PMID:17013632

  16. Effects of the adsorption of alkali metal oxides on the electronic, optical, and thermodynamic properties of the Mg12O12nanocage: a density functional theory study.

    PubMed

    Mohammadi Hesari, Asghar; Shamlouei, Hamid Reza; Raoof Toosi, Ali

    2016-08-01

    The effect of alkali metal oxides M n O (M = Li, Na, K; n = 2, 3, 4) on the geometric, electronic, and linear and nonlinear optical properties of the Mg12O12 nanocage was investigated by density-functional-based methods. According to the computational results, these alkali metal oxides are adsorbed on the Mg12O12 nanocage because this adsorption reduces its energy gap. The static first hyperpolarizability (β 0) of the nanocage is dramatically increased in the presence of the alkali metal oxides, with the greatest increase seen in the presence of the superalkalis (i.e., M3O; M = Li, Na, and K). The highest first hyperpolarizability (β 0 ≈ 600,000 a.u.) was calculated for K3O@Mg12O12, which was considerably more than that for Mg12O12. The thermodynamic properties and relative stabilities of these inorganic compounds are discussed. Graphical Abstract Optimized structure and DOS spectrum of K3O(e@Mg12O12). PMID:27449668

  17. Methods of recovering alkali metals

    DOEpatents

    Krumhansl, James L; Rigali, Mark J

    2014-03-04

    Approaches for alkali metal extraction, sequestration and recovery are described. For example, a method of recovering alkali metals includes providing a CST or CST-like (e.g., small pore zeolite) material. The alkali metal species is scavenged from the liquid mixture by the CST or CST-like material. The alkali metal species is extracted from the CST or CST-like material.

  18. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells

    NASA Astrophysics Data System (ADS)

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-02-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1-xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells.

  19. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells.

    PubMed

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-01-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1-xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber(|)buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells. PMID:26916212

  20. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells

    PubMed Central

    Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

    2016-01-01

    Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1−xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells. PMID:26916212

  1. Hydrothermal alkali metal recovery process

    DOEpatents

    Wolfs, Denise Y.; Clavenna, Le Roy R.; Eakman, James M.; Kalina, Theodore

    1980-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by treating them with a calcium or magnesium-containing compound in the presence of water at a temperature between about 250.degree. F. and about 700.degree. F. and in the presence of an added base to establish a pH during the treatment step that is higher than would otherwise be possible without the addition of the base. During the treating process the relatively high pH facilitates the conversion of water-insoluble alkali metal compounds in the alkali metal residues into water-soluble alkali metal constituents. The resultant aqueous solution containing water-soluble alkali metal constituents is then separated from the residue solids, which consist of the treated particles and any insoluble materials formed during the treatment step, and recycled to the gasification process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. Preferably, the base that is added during the treatment step is an alkali metal hydroxide obtained by water washing the residue solids produced during the treatment step.

  2. Alkali metal ion battery with bimetallic electrode

    SciTech Connect

    Boysen, Dane A; Bradwell, David J; Jiang, Kai; Kim, Hojong; Ortiz, Luis A; Sadoway, Donald R; Tomaszowska, Alina A; Wei, Weifeng; Wang, Kangli

    2015-04-07

    Electrochemical cells having molten electrodes having an alkali metal provide receipt and delivery of power by transporting atoms of the alkali metal between electrode environments of disparate chemical potentials through an electrochemical pathway comprising a salt of the alkali metal. The chemical potential of the alkali metal is decreased when combined with one or more non-alkali metals, thus producing a voltage between an electrode comprising the molten the alkali metal and the electrode comprising the combined alkali/non-alkali metals.

  3. Alkali metal intercalates of molybdenum disulfide.

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1973-01-01

    Study of some of the physicochemical properties of compounds obtained by subjecting natural molybdenite and single crystals of molybdenum disulfide grown by chemical vapor transport to intercalation with the alkali group of metals (Li, Na, K, Rb, and Cs) by means of the liquid ammonia technique. Reported data and results include: (1) the intercalation of the entire alkali metal group, (2) stoichiometries and X-ray data on all of the compounds, and (3) superconductivity data for all the intercalation compounds.

  4. Preparation of alkali metal dispersions

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Landel, R. F. (Inventor)

    1968-01-01

    A method is described for producing alkali metal dispersions of high purity. The dispersions are prepared by varying the equilibrium solubility of the alkali metal in a suitable organic solvent in the presence of aromatic hydrocarbons. The equilibrium variation is produced by temperature change. The size of the particles is controlled by controlling the rate of temperature change.

  5. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  6. Hall Determination of Atomic Radii of Alkali Metals

    ERIC Educational Resources Information Center

    Houari, Ahmed

    2008-01-01

    I will propose here an alternative method for determining atomic radii of alkali metals based on the Hall measurements of their free electron densities and the knowledge of their crystal structure. (Contains 2 figures.)

  7. Upgrading platform using alkali metals

    SciTech Connect

    Gordon, John Howard

    2014-09-09

    A process for removing sulfur, nitrogen or metals from an oil feedstock (such as heavy oil, bitumen, shale oil, etc.) The method involves reacting the oil feedstock with an alkali metal and a radical capping substance. The alkali metal reacts with the metal, sulfur or nitrogen content to form one or more inorganic products and the radical capping substance reacts with the carbon and hydrogen content to form a hydrocarbon phase. The inorganic products may then be separated out from the hydrocarbon phase.

  8. Alkali-metal azides interacting with metal-organic frameworks.

    PubMed

    Armata, Nerina; Cortese, Remedios; Duca, Dario; Triolo, Roberto

    2013-01-14

    Interactions between alkali-metal azides and metal-organic framework (MOF) derivatives, namely, the first and third members of the isoreticular MOF (IRMOF) family, IRMOF-1 and IRMOF-3, are studied within the density functional theory (DFT) paradigm. The investigations take into account different models of the selected IRMOFs. The mutual influence between the alkali-metal azides and the π rings or Zn centers of the involved MOF derivatives are studied by considering the interactions both of the alkali-metal cations with model aromatic centers and of the alkali-metal azides with distinct sites of differently sized models of IRMOF-1 and IRMOF-3. Several exchange and correlation functionals are employed to calculate the corresponding interaction energies. Remarkably, it is found that, with increasing alkali-metal atom size, the latter decrease for cations interacting with the π-ring systems and increase for the azides interacting with the MOF fragments. The opposite behavior is explained by stabilization effects on the azide moieties and determined by the Zn atoms, which constitute the inorganic vertices of the IRMOF species. Larger cations can, in fact, coordinate more efficiently to both the aromatic center and the azide anion, and thus stabilizing bridging arrangements of the azide between one alkali-metal and two Zn atoms in an η(2) coordination mode are more favored. PMID:23161861

  9. Hydrothermal alkali metal catalyst recovery process

    DOEpatents

    Eakman, James M.; Clavenna, LeRoy R.

    1979-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles primarily in the form of water soluble alkali metal formates by treating the particles with a calcium or magnesium-containing compound in the presence of water at a temperature between about 250.degree. F. and about 700.degree. F. and in the presence of added carbon monoxide. During the treating process the water insoluble alkali metal compounds comprising the insoluble alkali metal residues are converted into water soluble alkali metal formates. The resultant aqueous solution containing water soluble alkali metal formates is then separated from the treated particles and any insoluble materials formed during the treatment process, and recycled to the gasification process where the alkali metal formates serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary.

  10. Alkali-metal intercalation in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Béguin, F.; Duclaux, L.; Méténier, K.; Frackowiak, E.; Salvetat, J. P.; Conard, J.; Bonnamy, S.; Lauginie, P.

    1999-09-01

    We report on successful intercalation of multiwall (MWNT) and single wall (SWNT) carbon nanotubes with alkali metals by electrochemical and vapor phase reactions. A LiC10 compound was produced by full electrochemical reduction of MWNT. KC8 and CsC8-MWNT first stage derivatives were synthesized in conditions of alkali vapor saturation. Their identity periods and the 2×2 R 0° alkali superlattice are comparable to their parent graphite compounds. The dysonian shape of KC8 EPR line and the temperature-independent Pauli susceptibility are both characteristic of a metallic behavior, which was confirmed by 13C NMR anisotropic shifts. Exposure of SWNT bundles to alkali vapor led to an increase of the pristine triangular lattice from 1.67 nm to 1.85 nm and 1.87 nm for potassium and rubidium, respectively.

  11. Electrodes For Alkali-Metal Thermoelectric Converters

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Wheeler, Bob L.; Jeffries-Nakamura, Barbara; Lamb, James L.; Bankston, C. Perry; Cole, Terry

    1989-01-01

    Combination of thin, porous electrode and overlying collector grid reduces internal resistance of alkali-metal thermoelectric converter cell. Low resistance of new electrode and grid boosts power density nearly to 1 W/cm2 of electrode area at typical operating temperatures of 1,000 to 1,300 K. Conductive grid encircles electrode film on alumina tube. Bus wire runs along tube to collect electrical current from grid. Such converters used to transform solar, nuclear, and waste heat into electric power.

  12. Alkali metal/sulfur battery

    DOEpatents

    Anand, Joginder N.

    1978-01-01

    Alkali metal/sulfur batteries in which the electrolyte-separator is a relatively fragile membrane are improved by providing means for separating the molten sulfur/sulfide catholyte from contact with the membrane prior to cooling the cell to temperatures at which the catholyte will solidify. If the catholyte is permitted to solidify while in contact with the membrane, the latter may be damaged. The improvement permits such batteries to be prefilled with catholyte and shipped, at ordinary temperatures.

  13. Superconductivity in alkali metal fullerides

    NASA Astrophysics Data System (ADS)

    Murphy, D. W.; Rosseinsky, M. J.; Haddon, R. C.; Ramirez, A. P.; Hebard, A. F.; Tycko, R.; Fleming, R. M.; Dabbagh, G.

    1991-12-01

    The recent synthesis of macroscopic quantities of spherical molecular carbon compounds, commonly called fullerenes, has stimulated a wide variety of studies of the chemical and physical properties of this novel class of compounds. We discovered that the smallest of the known fullerenes, C 60, could be made conducting and superconducting by reaction with alkali metals. In this paper, an overview of the motivation for these discoveries and some recent results are presented.

  14. Alkali-Metal Spin Maser.

    PubMed

    Chalupczak, W; Josephs-Franks, P

    2015-07-17

    Quantum measurement is a combination of a read-out and a perturbation of the quantum system. We explore the nonlinear spin dynamics generated by a linearly polarized probe beam in a continuous measurement of the collective spin state in a thermal alkali-metal atomic sample. We demonstrate that the probe-beam-driven perturbation leads, in the presence of indirect pumping, to complete polarization of the sample and macroscopic coherent spin oscillations. As a consequence of the former we report observation of spectral profiles free from collisional broadening. Nonlinear dynamics is studied through exploring its effect on radio frequency as well as spin noise spectra. PMID:26230788

  15. Process for the disposal of alkali metals

    DOEpatents

    Lewis, Leroy C.

    1977-01-01

    Large quantities of alkali metals may be safely reacted for ultimate disposal by contact with a hot concentrated caustic solution. The alkali metals react with water in the caustic solution in a controlled reaction while steam dilutes the hydrogen formed by the reaction to a safe level.

  16. Method of handling radioactive alkali metal waste

    DOEpatents

    Wolson, Raymond D.; McPheeters, Charles C.

    1980-01-01

    Radioactive alkali metal is mixed with particulate silica in a rotary drum reactor in which the alkali metal is converted to the monoxide during rotation of the reactor to produce particulate silica coated with the alkali metal monoxide suitable as a feed material to make a glass for storing radioactive material. Silica particles, the majority of which pass through a 95 mesh screen or preferably through a 200 mesh screen, are employed in this process, and the preferred weight ratio of silica to alkali metal is 7 to 1 in order to produce a feed material for the final glass product having a silica to alkali metal monoxide ratio of about 5 to 1.

  17. Method of handling radioactive alkali metal waste

    DOEpatents

    Wolson, R.D.; McPheeters, C.C.

    Radioactive alkali metal is mixed with particulate silica in a rotary drum reactor in which the alkali metal is converted to the monoxide during rotation of the reactor to produce particulate silica coated with the alkali metal monoxide suitable as a feed material to make a glass for storing radioactive material. Silica particles, the majority of which pass through a 95 mesh screen or preferably through a 200 mesh screen, are employed in this process, and the preferred weight ratio of silica to alkali metal is 7 to 1 in order to produce a feed material for the final glass product having a silica to alkali metal monoxide ratio of about 5 to 1.

  18. Alkali metal crystalline polymer electrolytes.

    PubMed

    Zhang, Chuhong; Gamble, Stephen; Ainsworth, David; Slawin, Alexandra M Z; Andreev, Yuri G; Bruce, Peter G

    2009-07-01

    Polymer electrolytes have been studied extensively because uniquely they combine ionic conductivity with solid yet flexible mechanical properties, rendering them important for all-solid-state devices including batteries, electrochromic displays and smart windows. For some 30 years, ionic conductivity in polymers was considered to occur only in the amorphous state above Tg. Crystalline polymers were believed to be insulators. This changed with the discovery of Li(+) conductivity in crystalline poly(ethylene oxide)(6):LiAsF(6). However, new crystalline polymer electrolytes have proved elusive, questioning whether the 6:1 complex has particular structural features making it a unique exception to the rule that only amorphous polymers conduct. Here, we demonstrate that ionic conductivity in crystalline polymers is not unique to the 6:1 complex by reporting several new crystalline polymer electrolytes containing different alkali metal salts (Na(+), K(+) and Rb(+)), including the best conductor poly(ethylene oxide)(8):NaAsF(6) discovered so far, with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)(6):LiAsF(6). These are the first crystalline polymer electrolytes with a different composition and structures to that of the 6:1 Li(+) complex. PMID:19543313

  19. Alkali Metal Handling Practices at NASA MSFC

    NASA Technical Reports Server (NTRS)

    Salvail, Patrick G.; Carter, Robert R.

    2002-01-01

    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.

  20. Developments in alkali-metal atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Seltzer, Scott Jeffrey

    Alkali-metal magnetometers use the coherent precession of polarized atomic spins to detect and measure magnetic fields. Recent advances have enabled magnetometers to become competitive with SQUIDs as the most sensitive magnetic field detectors, and they now find use in a variety of areas ranging from medicine and NMR to explosives detection and fundamental physics research. In this thesis we discuss several developments in alkali-metal atomic magnetometry for both practical and fundamental applications. We present a new method of polarizing the alkali atoms by modulating the optical pumping rate at both the linear and quadratic Zeeman resonance frequencies. We demonstrate experimentally that this method enhances the sensitivity of a potassium magnetometer operating in the Earth's field by a factor of 4, and we calculate that it can reduce the orientation-dependent heading error to less than 0.1 nT. We discuss a radio-frequency magnetometer for detection of oscillating magnetic fields with sensitivity better than 0.2 fT/ Hz , which we apply to the observation of nuclear magnetic resonance (NMR) signals from polarized water, as well as nuclear quadrupole resonance (NQR) signals from ammonium nitrate. We demonstrate that a spin-exchange relaxation-free (SERF) magnetometer can measure all three vector components of the magnetic field in an unshielded environment with comparable sensitivity to other devices. We find that octadecyltrichlorosilane (OTS) acts as an anti-relaxation coating for alkali atoms at temperatures below 170°C, allowing them to collide with a glass surface up to 2,000 times before depolarizing, and we present the first demonstration of high-temperature magnetometry with a coated cell. We also describe a reusable alkali vapor cell intended for the study of interactions between alkali atoms and surface coatings. Finally, we explore the use of a cesium-xenon SERF comagnetometer for a proposed measurement of the permanent electric dipole moments (EDMs

  1. The alkali metals: 200 years of surprises.

    PubMed

    Dye, James L

    2015-03-13

    Alkali metal compounds have been known since antiquity. In 1807, Sir Humphry Davy surprised everyone by electrolytically preparing (and naming) potassium and sodium metals. In 1808, he noted their interaction with ammonia, which, 100 years later, was attributed to solvated electrons. After 1960, pulse radiolysis of nearly any solvent produced solvated electrons, which became one of the most studied species in chemistry. In 1968, alkali metal solutions in amines and ethers were shown to contain alkali metal anions in addition to solvated electrons. The advent of crown ethers and cryptands as complexants for alkali cations greatly enhanced alkali metal solubilities. This permitted us to prepare a crystalline salt of Na(-) in 1974, followed by 30 other alkalides with Na(-), K(-), Rb(-) and Cs(-) anions. This firmly established the -1 oxidation state of alkali metals. The synthesis of alkalides led to the crystallization of electrides, with trapped electrons as the anions. Electrides have a variety of electronic and magnetic properties, depending on the geometries and connectivities of the trapping sites. In 2009, the final surprise was the experimental demonstration that alkali metals under high pressure lose their metallic character as the electrons are localized in voids between the alkali cations to become high-pressure electrides! PMID:25666067

  2. SAFE Alkali Metal Heat Pipe Reliability

    NASA Astrophysics Data System (ADS)

    Reid, Robert S.

    2003-01-01

    Alkali metal heat pipes are among the best understood and tested of components for first generation space fission reactors. A flight reactor will require production of a hundred or more heat pipes with assured reliability over a number of years. To date, alkali metal heat pipes have been built mostly in low budget development environments with little formal quality assurance. Despite this, heat pipe test samples suggest that high reliability can be achieved with the care justified for space flight qualification. Fabrication procedures have been established that, if consistently applied, ensure long-term trouble-free heat pipe operation. Alkali metal heat pipes have been successfully flight tested in micro gravity and also have been shown capable of multi-year operation with no evidence of sensitivity to fast neutron fluence up to 1023 n/cm2. This represents 50 times the fluence of the proposed Safe Affordable Fission Engine (SAFE-100) heat pipe reactor core.

  3. Optimal densities of alkali metal atoms in an optically pumped K-Rb hybrid atomic magnetometer considering the spatial distribution of spin polarization.

    PubMed

    Ito, Yosuke; Sato, Daichi; Kamada, Keigo; Kobayashi, Tetsuo

    2016-07-11

    An optically pumped K-Rb hybrid atomic magnetometer can be a useful tool for biomagnetic measurements due to the high spatial homogeneity of its sensor property inside a cell. However, because the property varies depending on the densities of potassium and rubidium atoms, optimization of the densities is essential. In this study, by using the Bloch equations of K and Rb and considering the spatial distribution of the spin polarization, we confirmed that the calculation results of spin polarization behavior are in good agreement with the experimental data. Using our model, we calculated the spatial distribution of the spin polarization and found that the optimal density of K atoms is 3 × 1019 m-3 and the optimal density ratio is nK/nRb ~ 400 to maximize the output signal and enhance spatial homogeneity of the sensor property. PMID:27410815

  4. Theory of Magnetotransport Anomalies in Alkali Metals

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaodong

    The galvanomagnetic properties of alkali metals, especially those of potassium, are studied taking into account the existence of an incommensurate change-density wave (CDW) structure. Occurrence of the CDW broken symmetry truncates the Fermi surface with a large number of energy gaps. Furthermore, any macroscopic crystal is likely divided into CDW (')Q-domains. An orientational (')Q-texture leads to a preferred direction in the crystal. For such an exotic system the effective magnetoresistivity tensor is anomalous and is derived for various magnetic fields. The residual (zero-field) resistance is also anisotropic. For fields 0.5 - 3T, Hall coefficients are found to be anisotropic, and a longitudinal-transverse mixing effect is discovered. The diagonal elements of the magnetoresistivity tensor are found to have a linear magnetoresistance. When the field is increased above 4T sharp open-orbit magnetoresistance spectrum develops. From the theoretical magnetoresistivity tensor, the induced-torque amplitude and phase patterns for potassium spheres are calculated. The theory quantitatively explains all of the induced-torque anomalies found experimentally in the last fourteen years. An interacting electron system, which is free of the CDW instabilities, is also studied by considering its spin response to a weak sinusoidal magnetic field. The many-body correction G(,-)((')q,(omega)) caused by exchange and correlation is introduced to describe the correct wave -vector- and frequency-dependent spin susceptibility. The exact behavior of G(,-)((')q,(omega)) in the large-q limit is shown to be related to the pair distribution function g((')r) at r = 0. G(,-)((')q,(omega)) (--->) 4g(0)-1 /3, as q (--->) (INFIN).At metallic densities this value is negative, opposite in sign to the limit at small wave vectors. Thus the spin susceptibility for large wave vectors is suppressed, rather than enhanced, by many-body effects.

  5. Recovery of alkali metal constituents from catalytic coal conversion residues

    DOEpatents

    Soung, W.Y.

    In a coal gasification operation (32) or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by contacting them with water or an aqueous solution to remove water-soluble alkali metal constituents and produce an aqueous solution enriched in said constituents. The aqueous solution thus produced is then contacted with carbon dioxide to precipitate silicon constituents, the pH of the resultant solution is increased, preferably to a value in the range between about 12.5 and about 15.0, and the solution of increased pH is evaporated to increase the alkali metal concentration. The concentrated aqueous solution is then recycled to the conversion process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst.

  6. Salts of alkali metal anions and process of preparing same

    DOEpatents

    Dye, James L.; Ceraso, Joseph M.; Tehan, Frederick J.; Lok, Mei Tak

    1978-01-01

    Compounds of alkali metal anion salts of alkali metal cations in bicyclic polyoxadiamines are disclosed. The salts are prepared by contacting an excess of alkali metal with an alkali metal dissolving solution consisting of a bicyclic polyoxadiamine in a suitable solvent, and recovered by precipitation. The salts have a gold-color crystalline appearance and are stable in a vacuum at -10.degree. C. and below.

  7. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for...

  8. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for...

  9. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for...

  10. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkali metal alkyl borohydride... Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... alkali metal alkyl borohydride (PMN P-00-1089) is subject to reporting under this section for...

  11. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alcohol, alkali metal salt. 721.4660... Substances § 721.4660 Alcohol, alkali metal salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as alcohol, alkali metal salt (PMN P-91-151)...

  12. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alcohol, alkali metal salt. 721.4660... Substances § 721.4660 Alcohol, alkali metal salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as alcohol, alkali metal salt (PMN P-91-151)...

  13. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alcohol, alkali metal salt. 721.4660... Substances § 721.4660 Alcohol, alkali metal salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as alcohol, alkali metal salt (PMN P-91-151)...

  14. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alcohol, alkali metal salt. 721.4660... Substances § 721.4660 Alcohol, alkali metal salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as alcohol, alkali metal salt (PMN P-91-151)...

  15. 40 CFR 721.4660 - Alcohol, alkali metal salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alcohol, alkali metal salt. 721.4660... Substances § 721.4660 Alcohol, alkali metal salt. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as alcohol, alkali metal salt (PMN P-91-151)...

  16. Alkali metal recovery from carbonaceous material conversion process

    DOEpatents

    Sharp, David W.; Clavenna, LeRoy R.; Gorbaty, Martin L.; Tsou, Joe M.

    1980-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced in the gasifier or similar reaction zone, alkali metal constitutents are recovered from the particles by withdrawing and passing the particles from the reaction zone to an alkali metal recovery zone in the substantial absence of molecular oxygen and treating the particles in the recovery zone with water or an aqueous solution in the substantial absence of molecular oxygen. The solution formed by treating the particles in the recovery zone will contain water-soluble alkali metal constituents and is recycled to the conversion process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. Preventing contact of the particles with oxygen as they are withdrawn from the reaction zone and during treatment in the recovery zone avoids the formation of undesirable alkali metal constituents in the aqueous solution produced in the recovery zone and insures maximum recovery of water-soluble alkali metal constituents from the alkali metal residues.

  17. Removal of Retired Alkali Metal Test Systems

    SciTech Connect

    BREHM, W.F.

    2003-01-01

    This paper describes the successful effort to remove alkali metals, alkali metal residues, and piping and structures from retired non-radioactive test systems on the Hanford Site. These test systems were used between 1965 and 1982 to support the Fast Flux Test Facility and the Liquid Metal Fast Breeder Reactor Program. A considerable volume of sodium and sodium-potassium alloy (NaK) was successfully recycled to the commercial sector; structural material and electrical material such as wiring was also recycled. Innovative techniques were used to safely remove NaK and its residues from a test system that could not be gravity-drained. The work was done safely, with no environmental issues or significant schedule delays.

  18. Removal of Retired Alkali Metal Test Systems

    SciTech Connect

    Brehm, W. F.; Church, W. R.; Biglin, J. W.

    2003-02-26

    This paper describes the successful effort to remove alkali metals, alkali metal residues, and piping and structures from retired non-radioactive test systems on the Hanford Site. These test systems were used between 1965 and 1982 to support the Fast Flux Test Facility and the Liquid Metal Fast Breeder Reactor Program. A considerable volume of sodium and sodium-potassium alloy (NaK) was successfully recycled to the commercial sector; structural material and electrical material such as wiring was also recycled. Innovative techniques were used to safely remove NaK and its residues from a test system that could not be gravity-drained. The work was done safely, with no environmental issues or significant schedule delays.

  19. Alkali Metal Heat Pipe Life Issues

    NASA Technical Reports Server (NTRS)

    Reid, Robert S.

    2004-01-01

    One approach to space fission power system design is predicated on the use of alkali metal heat pipes, either as radiator elements, thermal management components, or as part of the core primary heat-transfer system. This synopsis characterizes long-life core heat pipes. References are included where more detailed information can be found. Specifics shown here are for demonstrational purposes and do not necessarily reflect current Project Prometheus point designs.

  20. Alkali metal protective garment and composite material

    SciTech Connect

    Ballif, J.L.; Yuan, W.W.

    1980-09-16

    A protective garment and composite material providing satisfactory heat resistance and physical protection for articles and personnel exposed to hot molten alkali metals, such as sodium are described. Physical protection is provided by a continuous layer of nickel foil. Heat resistance is provided by an underlying backing layer of thermal insulation. Overlying outer layers of fireproof woven ceramic fibers are used to protect the foil during storage and handling.

  1. Alkali metal protective garment and composite material

    SciTech Connect

    Ballif, III, John L.; Yuan, Wei W.

    1980-01-01

    A protective garment and composite material providing satisfactory heat resistance and physical protection for articles and personnel exposed to hot molten alkali metals, such as sodium. Physical protection is provided by a continuous layer of nickel foil. Heat resistance is provided by an underlying backing layer of thermal insulation. Overlying outer layers of fireproof woven ceramic fibers are used to protect the foil during storage and handling.

  2. Superconductivity in the alkali metal intercalates of molybdenum disulphide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1972-01-01

    The complete series of alkali metals, lithium through cesium, have been intercalated into molybdenum disulphide, using both the liquid ammonia and vapor techniques. All the intercalates with the exception of lithium yielded full superconducting transitions with onset temperatures of 6 K for AxMoS2(Ax=K,Rb,Cs) and 4 K for BxMoS2(Bx=Li,Na). The superconducting transition for lithium was incomplete down to 1.5 K. Stoichiometries and unit cell parameters have been determined for the intercalation compounds. Both rhombohedral and hexagonal polymorphs of MoS2 have been intercalated and found to exhibit the same superconductivity behavior. The nature of the extraneous superconducting transition of some intercalated samples on exposure to air was elucidated.

  3. Release and sorption of alkali metals in coal conversion

    SciTech Connect

    Witthohn, A.; Oeltjen, L.; Hilpert, K.

    1998-07-01

    Released as gaseous species during coal combustion and gasification, alkali metal compounds cause high temperature corrosion especially at the gas turbine blading of coal-fired combined cycle power plants. Experimental and theoretical basic investigations are presented, which contribute to the understanding of the release and sorption of these contaminants. Knudsen effusion mass spectrometry was used to study the vaporization of coal ashes and slags at temperatures between 200 and 1,800 C and to determine the released alkali species and their partial pressures. The data base system FACT and the modified quasi-chemical model for non-ideal solutions were applied to model the thermodynamic behavior of coal slags and to determine material compositions of maximum alkali sorption capacity.

  4. Theoretical study on the adsorption of carbon dioxide on individual and alkali-metal doped MOF-5s

    NASA Astrophysics Data System (ADS)

    Ha, Nguyen Thi Thu; Lefedova, O. V.; Ha, Nguyen Ngoc

    2016-01-01

    Density functional theory (DFT) calculations were performed to investigate the adsorption of carbon dioxide (CO2) on metal-organic framework (MOF-5) and alkali-metal (Li, K, Na) doped MOF-5s. The adsorption energy calculation showed that metal atom adsorption is exothermic in MOF-5 system. Moreover, alkali-metal doping can significantly improve the adsorption ability of carbon dioxide on MOF-5. The best influence is observed for Li-doping.

  5. Method for the safe disposal of alkali metal

    DOEpatents

    Johnson, Terry R.

    1977-01-01

    Alkali metals such as those employed in liquid metal coolant systems can be safely reacted to form hydroxides by first dissolving the alkali metal in relatively inert metals such as lead or bismuth. The alloy thus formed is contacted with a molten salt including the alkali metal hydroxide and possibly the alkali metal carbonate in the presence of oxygen. This oxidizes the alkali metal to an oxide which is soluble within the molten salt. The salt is separated and contacted with steam or steam-CO.sub.2 mixture to convert the alkali metal oxide to the hydroxide. These reactions can be conducted with minimal hydrogen evolution and with the heat of reaction distributed between the several reaction steps.

  6. Cathode architectures for alkali metal / oxygen batteries

    SciTech Connect

    Visco, Steven J; Nimon, Vitaliy; De Jonghe, Lutgard C; Volfkovich, Yury; Bograchev, Daniil

    2015-01-13

    Electrochemical energy storage devices, such as alkali metal-oxygen battery cells (e.g., non-aqueous lithium-air cells), have a cathode architecture with a porous structure and pore composition that is tailored to improve cell performance, especially as it pertains to one or more of the discharge/charge rate, cycle life, and delivered ampere-hour capacity. A porous cathode architecture having a pore volume that is derived from pores of varying radii wherein the pore size distribution is tailored as a function of the architecture thickness is one way to achieve one or more of the aforementioned cell performance improvements.

  7. Electrochemical devices utilizing molten alkali metal electrode-reactant

    DOEpatents

    Hitchcock, D.C.; Mailhe, C.C.; De Jonghe, L.C.

    1985-07-10

    Electrochemical cells are provided with a reactive metal to reduce the oxide of the alkali metal electrode-reactant. Cells employing a molten alkali metal electrode, e.g., sodium, in contact with a ceramic electrolyte, which is a conductor of the ions of the alkali metal forming the electrode, exhibit a lower resistance when a reactive metal, e.g., vanadium, is allowed to react with and reduce the alkali metal oxide. Such cells exhibit less degradation of the electrolyte and of the glass seals often used to joining the electrolyte to the other components of the cell under cycling conditions.

  8. Electrochemical devices utilizing molten alkali metal electrode-reactant

    DOEpatents

    Hitchcock, David C.; Mailhe, Catherine C.; De Jonghe, Lutgard C.

    1986-01-01

    Electrochemical cells are provided with a reactive metal to reduce the oxide of the alkali metal electrode-reactant. Cells employing a molten alkali metal electrode, e.g., sodium, in contact with a ceramic electrolyte, which is a conductor of the ions of the alkali metal forming the electrode, exhibit a lower resistance when a reactive metal, e.g., vanadium, is allowed to react with and reduce the alkali metal oxide. Such cells exhibit less degradation of the electrolyte and of the glass seals often used to joining the electrolyte to the other components of the cell under cycling conditions.

  9. The Alkali Metal Thermal-To-Electric Converter for Solar System Exploration

    NASA Technical Reports Server (NTRS)

    Ryan, M.

    1999-01-01

    AMTEC, the Alkali Metal Thermal to Electric Converter, is a direct thermal to electric energy conversion device; it has been demostrated to perform at high power densities, with open circuit voltages in single electrochemical cells up to 1.6 V and current desities up to 2.0 A/cm(sup 2).

  10. High bandwidth vapor density diagnostic system

    DOEpatents

    Globig, Michael A.; Story, Thomas W.

    1992-01-01

    A high bandwidth vapor density diagnostic system for measuring the density of an atomic vapor during one or more photoionization events. The system translates the measurements from a low frequency region to a high frequency, relatively noise-free region in the spectrum to provide improved signal to noise ratio.

  11. Superconductivity in alkali metal intercalated iron selenides.

    PubMed

    Krzton-Maziopa, A; Svitlyk, V; Pomjakushina, E; Puzniak, R; Conder, K

    2016-07-27

    Alkali metal intercalated iron selenide superconductors A x Fe2-y Se2 (where A  =  K, Rb, Cs, Tl/K, and Tl/Rb) are characterized by several unique properties, which were not revealed in other superconducting materials. The compounds crystallize in overall simple layered structure with FeSe layers intercalated with alkali metal. The structure turned out to be pretty complex as the existing Fe-vacancies order below ~550 K, which further leads to an antiferromagnetic ordering with Néel temperature fairly above room temperature. At even lower temperatures a phase separation is observed. While one of these phases stays magnetic down to the lowest temperatures the second is becoming superconducting below ~30 K. All these effects give rise to complex relationships between the structure, magnetism and superconductivity. In particular the iron vacancy ordering, linked with a long-range magnetic order and a mesoscopic phase separation, is assumed to be an intrinsic property of the system. Since the discovery of superconductivity in those compounds in 2010 they were investigated very extensively. Results of the studies conducted using a variety of experimental techniques and performed during the last five years were published in hundreds of reports. The present paper reviews scientific work concerning methods of synthesis and crystal growth, structural and superconducting properties as well as pressure investigations. PMID:27248118

  12. Superconductivity in alkali metal intercalated iron selenides

    NASA Astrophysics Data System (ADS)

    Krzton-Maziopa, A.; Svitlyk, V.; Pomjakushina, E.; Puzniak, R.; Conder, K.

    2016-07-01

    Alkali metal intercalated iron selenide superconductors A x Fe2‑y Se2 (where A  =  K, Rb, Cs, Tl/K, and Tl/Rb) are characterized by several unique properties, which were not revealed in other superconducting materials. The compounds crystallize in overall simple layered structure with FeSe layers intercalated with alkali metal. The structure turned out to be pretty complex as the existing Fe-vacancies order below ~550 K, which further leads to an antiferromagnetic ordering with Néel temperature fairly above room temperature. At even lower temperatures a phase separation is observed. While one of these phases stays magnetic down to the lowest temperatures the second is becoming superconducting below ~30 K. All these effects give rise to complex relationships between the structure, magnetism and superconductivity. In particular the iron vacancy ordering, linked with a long-range magnetic order and a mesoscopic phase separation, is assumed to be an intrinsic property of the system. Since the discovery of superconductivity in those compounds in 2010 they were investigated very extensively. Results of the studies conducted using a variety of experimental techniques and performed during the last five years were published in hundreds of reports. The present paper reviews scientific work concerning methods of synthesis and crystal growth, structural and superconducting properties as well as pressure investigations.

  13. Recovery of alkali metal constituents from catalytic coal conversion residues

    DOEpatents

    Soung, Wen Y.

    1984-01-01

    In a coal gasification operation (32) or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by contacting them (46, 53, 61, 69) with water or an aqueous solution to remove water-soluble alkali metal constituents and produce an aqueous solution enriched in said constituents. The aqueous solution thus produced is then contacted with carbon dioxide (63) to precipitate silicon constituents, the pH of the resultant solution is increased (81), preferably to a value in the range between about 12.5 and about 15.0, and the solution of increased pH is evaporated (84) to increase the alkali metal concentration. The concentrated aqueous solution is then recycled to the conversion process (86, 18, 17) where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst.

  14. 40 CFR 721.4740 - Alkali metal nitrites.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... defined in 40 CFR 721.3) containing amines. (b) ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal nitrites. 721.4740... Substances § 721.4740 Alkali metal nitrites. (a) Chemical substances and significant new use subject...

  15. 40 CFR 721.4740 - Alkali metal nitrites.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... defined in 40 CFR 721.3) containing amines. (b) ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkali metal nitrites. 721.4740... Substances § 721.4740 Alkali metal nitrites. (a) Chemical substances and significant new use subject...

  16. 40 CFR 721.4740 - Alkali metal nitrites.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... defined in 40 CFR 721.3) containing amines. (b) ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkali metal nitrites. 721.4740... Substances § 721.4740 Alkali metal nitrites. (a) Chemical substances and significant new use subject...

  17. 40 CFR 721.4740 - Alkali metal nitrites.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... defined in 40 CFR 721.3) containing amines. (b) ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkali metal nitrites. 721.4740... Substances § 721.4740 Alkali metal nitrites. (a) Chemical substances and significant new use subject...

  18. Self-discharge in bimetallic cells containing alkali metal

    NASA Technical Reports Server (NTRS)

    Foster, M. S.; Hesson, J. C.; Shimotake, H.

    1969-01-01

    Theoretical analysis of thermally regenerative bimetallic cells with alkali metal anodes shows a relation between the current drawn and the rate of discharge under open-circuit conditions. The self-discharge rate of the cell is due to the dissolution and ionization of alkali metal atoms in the fused-salt electrolyte

  19. COMPLEX FLUORIDES OF PLUTONIUM AND AN ALKALI METAL

    DOEpatents

    Seaborg, G.T.

    1960-08-01

    A method is given for precipitating alkali metal plutonium fluorides. such as KPuF/sub 5/, KPu/sub 2/F/sub 9/, NaPuF/sub 5/, and RbPuF/sub 5/, from an aqueous plutonium(IV) solution by adding hydrogen fluoride and alkali-metal- fluoride.

  20. 40 CFR 721.4740 - Alkali metal nitrites.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.4740 Alkali metal nitrites. (a) Chemical substances and significant new use subject to reporting. (1) The category of chemical substances which are nitrites of the alkali metals (Group IA in...

  1. 40 CFR 721.1878 - Alkali metal alkyl borohydride (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.1878 Alkali metal alkyl borohydride (generic). (a) Chemical substance... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal alkyl...

  2. Heat pipes containing alkali metal working fluid

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1981-01-01

    A technique for improving high temperature evaporation-condensation heat-transfer devices which have important and unique advantage in terrestrial and space energy processing is described. The device is in the form of a heat pipe comprising a sealed container or envelope which contains a capillary wick. The temperature of one end of the heat pipe is raised by the input of heat from an external heat source which is extremely hot and corrosive. A working fluid of a corrosive alkali metal, such as lithium, sodium, or potassium transfers this heat to a heat receiver remote from the heat source. The container and wick are fabricated from a superalloy containing a small percentage of a corrosion inhibiting or gettering element. Lanthanum, scandium, yttrium, thorium, and hafnium are utilized as the alloying metal.

  3. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, M.M.; Peng, M.Y.; Ma, Y.; Visco, S.J.; DeJonghe, L.C.

    1996-09-24

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M{sub x}Z{sub y}Mn{sub (1{minus}y)}O{sub 2}, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell. 11 figs.

  4. Alkali Metal Variation and Twisting of the FeNNFe Core in Bridging Diiron Dinitrogen Complexes.

    PubMed

    McWilliams, Sean F; Rodgers, Kenton R; Lukat-Rodgers, Gudrun; Mercado, Brandon Q; Grubel, Katarzyna; Holland, Patrick L

    2016-03-21

    Alkali metal cations can interact with Fe-N2 complexes, potentially enhancing back-bonding or influencing the geometry of the iron atom. These influences are relevant to large-scale N2 reduction by iron, such as in the FeMoco of nitrogenase and the alkali-promoted Haber-Bosch process. However, to our knowledge there have been no systematic studies of a large range of alkali metals regarding their influence on transition metal-dinitrogen complexes. In this work, we varied the alkali metal in [alkali cation]2[LFeNNFeL] complexes (L = bulky β-diketiminate ligand) through the size range from Na(+) to K(+), Rb(+), and Cs(+). The FeNNFe cores have similar Fe-N and N-N distances and N-N stretching frequencies despite the drastic change in alkali metal cation size. The two diketiminates twist relative to one another, with larger dihedral angles accommodating the larger cations. In order to explain why the twisting has so little influence on the core, we performed density functional theory calculations on a simplified LFeNNFeL model, which show that the two metals surprisingly do not compete for back-bonding to the same π* orbital of N2, even when the ligand planes are parallel. This diiron system can tolerate distortion of the ligand planes through compensating orbital energy changes, and thus, a range of ligand orientations can give very similar energies. PMID:26925968

  5. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, Marca M.; Peng, Marcus Y.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard C.

    1996-01-01

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

  6. Controlled in-situ dissolution of an alkali metal

    DOEpatents

    Jones, Jeffrey Donald; Dooley, Kirk John; Tolman, David Donald

    2012-09-11

    A method for the controllable dissolution of one or more alkali metals from a vessel containing a one or more alkali metals and/or one or more partially passivated alkali metals. The vessel preferably comprising a sodium, NaK or other alkali metal-cooled nuclear reactor that has been used. The alkali metal, preferably sodium, potassium or a combination thereof, in the vessel is exposed to a treatment liquid, preferably an acidic liquid, more preferably citric acid. Preferably, the treatment liquid is maintained in continuous motion relative to any surface of unreacted alkali metal with which the treatment liquid is in contact. The treatment liquid is preferably pumped into the vessel containing the one or more alkali metals and the resulting fluid is extracted and optionally further processed. Preferably, the resulting off-gases are processed by an off-gas treatment system and the resulting liquids are processed by a liquid disposal system. In one preferred embodiment, an inert gas is pumped into the vessel along with the treatment liquid.

  7. Electrochemical cell utilizing molten alkali metal electrode-reactant

    DOEpatents

    Virkar, Anil V.; Miller, Gerald R.

    1983-11-04

    An improved electrochemical cell comprising an additive-modified molten alkali metal electrode-reactant and/or electrolyte is disclosed. Various electrochemical cells employing a molten alkali metal, e.g., sodium, electrode in contact with a cationically conductive ceramic membrane experience a lower resistance and a lower temperature coefficient of resistance whenever small amounts of selenium are present at the interface of the electrolyte and the molten alkali metal. Further, cells having small amounts of selenium present at the electrolyte-molten metal interface exhibit less degradation of the electrolyte under long term cycling conditions.

  8. Bioinorganic Chemistry of the Alkali Metal Ions.

    PubMed

    Kim, Youngsam; Nguyen, Thuy-Tien T; Churchill, David G

    2016-01-01

    The common Group 1 alkali metals are indeed ubiquitous on earth, in the oceans and in biological systems. In this introductory chapter, concepts involving aqueous chemistry and aspects of general coordination chemistry and oxygen atom donor chemistry are introduced. Also, there are nuclear isotopes of importance. A general discussion of Group 1 begins from the prevalence of the ions, and from a comparison of their ionic radii and ionization energies. While oxygen and water molecule binding have the most relevance to biology and in forming a detailed understanding between the elements, there is a wide range of basic chemistry that is potentially important, especially with respect to biological chelation and synthetic multi-dentate ligand design. The elements are widely distributed in life forms, in the terrestrial environment and in the oceans. The details about the workings in animal, as well as plant life are presented in this volume. Important biometallic aspects of human health and medicine are introduced as well. Seeing as the elements are widely present in biology, various particular endogenous molecules and enzymatic systems can be studied. Sodium and potassium are by far the most important and central elements for consideration. Aspects of lithium, rubidium, cesium and francium chemistry are also included; they help in making important comparisons related to the coordination chemistry of Na(+) and K(+). Physical methods are also introduced. PMID:26860297

  9. Method of treating alkali metal sulfide and carbonate mixtures

    DOEpatents

    Kohl, Arthur L.; Rennick, Robert D.; Savinsky, Martin W.

    1978-01-01

    A method of removing and preferably recovering sulfur values from an alkali metal sulfide and carbonate mixture comprising the steps of (1) introducing the mixture in an aqueous medium into a first carbonation zone and reacting the mixture with a gas containing a major amount of CO.sub.2 and a minor amount of H.sub.2 S; (2) introducing the resultant product from step 1 into a stripping zone maintained at subatmospheric pressure, and contacting this product with steam to produce a gaseous mixture, comprising H.sub.2 S and water vapor, and a liquor of reduced sulfide content; (3) introducing the liquor of reduced sulfide content into a second carbonation zone, and reacting the liquor with substantially pure gaseous CO.sub.2 in an amount sufficient to precipitate bicarbonate crystals and produce an offgas containing CO.sub.2 and H.sub.2 S for use in step 1; (4) recovering the bicarbonate crystals from step 3, and thermally decomposing the crystals to produce an alkaline metal carbonate product and a substantially pure CO.sub.2 offgas for use in step 3.

  10. The 4843 Alkali Metal Storage Facility Closure Plan

    SciTech Connect

    Not Available

    1991-06-01

    The 4843 AMSF has been used primarily to provide a centralized building to receive and store dangerous and mixed alkali metal waste, including sodium and lithium, which has been generated at the Fast Flux Test Facility and at various other Hanford Site operations that used alkali metals. Most of the dangerous and mixed alkali metal waste received consists of retired equipment from liquid sodium processes. The unit continues to store material. In general, only solid alkali metal waste that is water reactive is stored at the 4843 AMSF. The 4843 AMSF will be closed in a manner consistent with Ecology guidelines and regulations (WAC 173-303-610). The general closure procedure is detailed as follows.

  11. Method for intercalating alkali metal ions into carbon electrodes

    DOEpatents

    Doeff, M.M.; Ma, Y.; Visco, S.J.; DeJonghe, L.

    1995-08-22

    A low cost, relatively flexible, carbon electrode for use in a secondary battery is described. A method is provided for producing same, including intercalating alkali metal salts such as sodium and lithium into carbon.

  12. Method for intercalating alkali metal ions into carbon electrodes

    DOEpatents

    Doeff, Marca M.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard

    1995-01-01

    A low cost, relatively flexible, carbon electrode for use in a secondary battery is described. A method is provided for producing same, including intercalating alkali metal salts such as sodium and lithium into carbon.

  13. Apparatus enables accurate determination of alkali oxides in alkali metals

    NASA Technical Reports Server (NTRS)

    Dupraw, W. A.; Gahn, R. F.; Graab, J. W.; Maple, W. E.; Rosenblum, L.

    1966-01-01

    Evacuated apparatus determines the alkali oxide content of an alkali metal by separating the metal from the oxide by amalgamation with mercury. The apparatus prevents oxygen and moisture from inadvertently entering the system during the sampling and analytical procedure.

  14. Electrochemical cell having an alkali-metal-nitrate electrode

    DOEpatents

    Roche, M.F.; Preto, S.K.

    1982-06-04

    A power-producing secondary electrochemical cell includes a molten alkali metal as the negative-electrode material and a molten-nitrate salt as the positive-electrode material. The molten material in the respective electrodes are separated by a solid barrier of alkali-metal-ion conducting material. A typical cell includes active materials of molten sodium separated from molten sodium nitrate and other nitrates in mixture by a layer of sodium ..beta..'' alumina.

  15. A Quantitative Tunneling/Desorption Model for the Exchange Current at the Porous Electrode/Beta - Alumina/Alkali Metal Gas Three Phase Zone at 700-1300K

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Ryan, M. A.; Saipetch, C.; LeDuc, H. G.

    1996-01-01

    The exchange current observed at porous metal electrodes on sodium or potassium beta -alumina solid electrolytes in alkali metal vapor is quantitatively modeled with a multi-step process with good agreement with experimental results.

  16. X-ray Compton scattering experiments for fluid alkali metals at high temperatures and pressures

    SciTech Connect

    Matsuda, K. Fukumaru, T.; Kimura, K.; Yao, M.; Tamura, K.; Katoh, M.; Kajihara, Y.; Inui, M.; Itou, M.; Sakurai, Y.

    2015-08-17

    We have developed a high-pressure vessel and a cell for x-ray Compton scattering measurements of fluid alkali metals. Measurements have been successfully carried out for alkali metal rubidium at elevated temperatures and pressures using synchrotron radiation at SPring-8. The width of Compton profiles (CPs) of fluid rubidium becomes narrow with decreasing fluid density, which indicates that the CPs sensitively detect the effect of reduction in the valence electron density. At the request of all authors of the paper, and with the agreement of the Proceedings Editor, an updated version of this article was published on 10 September 2015. The original article supplied to AIP Publishing was not the final version and contained PDF conversion errors in Formulas (1) and (2). The errors have been corrected in the updated and re-published article.

  17. Progress in High-Field Optical Pumping of Alkali Metal Nuclei

    NASA Astrophysics Data System (ADS)

    Patton, B.; Ishikawa, K.; Jau, Y.-Y.; Happer, W.

    2006-05-01

    We present preliminary results of an attempt to polarize alkali metal nuclei via optical pumping in a large (9.4-tesla) magnetic field. NMR measurements of ^87Rb and ^133Cs films in optical cells will be reported. Depopulation pumping of alkalis can easily produce electron polarizations of order unity, as measured during spin-exchange optical pumping of noble gases [1]. At low magnetic fields (< ˜1 kG), the strong hyperfine coupling between the alkali electron and nucleus allows angular momentum exchange from one to the other, resulting in nuclear polarization enhancement through optical pumping. In the high magnetic fields required for NMR, however, this interaction is largely decoupled and electron-nuclear spin exchange must rely upon the δA I .S interaction induced by buffer gas collisions (also called the ``Carver rate''). High-field optical pumping experiments may allow for a more precise measurement of this rate, as well as yielding insight into the transfer of angular momentum from the polarized alkali vapor to the bulk alkali metal on the cell walls. The technical challenges of high-resolution NMR of alkali metals at 9.4 tesla will be discussed. 1. E. Babcock, I. Nelson, S. Kadlecek, et al., Physical Review Letters 91, 123003 (2003).

  18. Two-phase alkali-metal experiments in reduced gravity

    SciTech Connect

    Antoniak, Z.I.

    1986-06-01

    Future space missions envision the use of large nuclear reactors utilizing either a single or a two-phase alkali-metal working fluid. The design and analysis of such reactors require state-of-the-art computer codes that can properly treat alkali-metal flow and heat transfer in a reduced-gravity environment. A literature search of relevant experiments in reduced gravity is reported on here, and reveals a paucity of data for such correlations. The few ongoing experiments in reduced gravity are noted. General plans are put forth for the reduced-gravity experiments which will have to be performed, at NASA facilities, with benign fluids. A similar situation exists regarding two-phase alkali-metal flow and heat transfer, even in normal gravity. Existing data are conflicting and indequate for the task of modeling a space reactor using a two-phase alkali-metal coolant. The major features of past experiments are described here. Data from the reduced-gravity experiments with innocuous fluids are to be combined with normal gravity data from the two-phase alkali-metal experiments. Analyses undertaken here give every expectation that the correlations developed from this data base will provide a valid representation of alkali-metal heat transfer and pressure drop in reduced gravity.

  19. (abstract) Alkali Metal Diffusion Through Porous Metal Electrodes in AMTEC Cells

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S.

    1993-01-01

    The mechanisms of mass transport of an alkali metal through porous metal electrodes in alkali metal thermal-to-electric converter AMTEC cells is important in optimizing these high current density devices, but also affords the opportunity to investigate a variety of simple mass transport modes at high temperatures via electrochemical techniques. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes. Quantitative investigations of Na transport through WPt(sub 3.5) via surface or grain boundary diffusion, and K transport through porous Mo electrodes by free molecular flow, over large ranges of temperature have been performed. WPt(sub 3.5) has especially low transport impedance over the 950 to 1200K temperature range. New results are the Na through porous WPt(sub 3.5) and K through porous Mo diffusion rates and mechanisms.

  20. An Aqueous Redox Flow Battery Based on Neutral Alkali Metal Ferri/ferrocyanide and Polysulfide Electrolytes

    SciTech Connect

    Wei, Xiaoliang; Xia, Gordon; Kirby, Brent W.; Thomsen, Edwin C.; Li, Bin; Nie, Zimin; Graff, Gordon L.; Liu, Jun; Sprenkle, Vincent L.; Wang, Wei

    2015-11-13

    Aiming to explore low-cost redox flow battery systems, a novel iron-polysulfide (Fe/S) flow battery has been demonstrated in a laboratory cell. This system employs alkali metal ferri/ferrocyanide and alkali metal polysulfides as the redox electrolytes. When proper electrodes, such as pretreated graphite felts, are used, 78% energy efficiency and 99% columbic efficiency are achieved. The remarkable advantages of this system over current state-of-the-art redox flow batteries include: 1) less corrosive and relatively environmentally benign redox solutions used; 2) excellent energy and utilization efficiencies; 3) low cost for redox electrolytes and cell components. These attributes can lead to significantly reduced capital cost and make the Fe/S flow battery system a promising low-cost energy storage technology. The major drawbacks of the present cell design are relatively low power density and possible sulfur species crossover. Further work is underway to address these concerns.

  1. Theoretical investigations on the stability of alkali metal substituted phenylpentazole.

    PubMed

    Zhang, Xueli; Gong, Xuedong

    2016-05-01

    The alkali metal (M=Li, Na, and K) para-substituted (M-1), meta-substituted (M-2) or ortho-substituted (M-3) derivatives of phenylpentazole (PhN5) were studied using density functional theory. The substituted metals improve the energy barrier for decomposition of the N5 ring of PhN5 by 19.3 ∼ 65.0 kJ/mol. M-3 has the ionic N-M bond, which is not found for M-1 and M-2. M-1 and M-2 have similar electrostatic potentials and dispersion interactions between metal and N5 ring. The comparable intramolecular interactions of M-1 and M-2 lead to similar N5 ring stability. Compared to M-1 and M-2, M-3 has a more negative charge on N5 ring and stronger dispersion interaction. The stronger intramolecular interactions of M-3 result in the higher N5 ring stability. For M-1 and M-2, different metals have slight affects on N5 ring stability. For M-3, N5 ring stability decreases in the order of Li > Na > K. The substituted metal lowers E g of PhN5. PMID:27083566

  2. Alkali metal yttrium neo-pentoxide double alkoxide precursors to alkali metal yttrium oxide nanomaterials

    DOE PAGESBeta

    Boyle, Timothy J.; Neville, Michael L.; Sears, Jeremiah Matthew; Cramer, Roger

    2016-03-15

    In this study, a series of alkali metal yttrium neo-pentoxide ([AY(ONep)4]) compounds were developed as precursors to alkali yttrium oxide (AYO2) nanomaterials. The reaction of yttrium amide ([Y(NR2)3] where R=Si(CH3)3) with four equivalents of H-ONep followed by addition of [A(NR2)] (A=Li, Na, K) or Ao (Ao=Rb, Cs) led to the formation of a complex series of AnY(ONep)3+n species, crystallographically identified as [Y2Li3(μ3-ONep)(μ3-HONep)(μ-ONep)5(ONep)3(HONep)2] (1), [YNa2(μ3-ONep)4(ONep)]2 (2), {[Y2K3(μ3-ONep)3(μ-ONep)4(ONep)2(ηξ-tol)2][Y4K2(μ4-O)(μ3-ONep)8(ONep)4]•ηx-tol]} (3), [Y4K2(μ4-O)(μ3-ONep)8(ONep)4] (3a), [Y2Rb3(μ4-ONep)3(μ-ONep)6] (4), and [Y2Cs4(μ6-O)(μ3-ONep)6(μ3-HONep)2(ONep)2(ηx-tol)4]•tol (5). Compounds 1–5 were investigated as single source precursors to AYOx nanomaterials following solvothermal routes (pyridine, 185 °C for 24h). The final products after thermal processing weremore » found by powder X-ray diffraction experiments to be Y2O3 with variable sized particles based on transmission electron diffraction. Energy dispersive X-ray spectroscopy studies indicated that the heavier alkali metal species were present in the isolated nanomaterials.« less

  3. Structure and properties of alizarin complex formed with alkali metal hydroxides in methanol solution.

    PubMed

    Jeliński, Tomasz; Cysewski, Piotr

    2016-06-01

    Quantum chemical computations were used for prediction of the structure and color of alizarin complex with alkali metal hydroxides in methanolic solutions. The color prediction relying on the single Gaussian-like band once again proved the usefulness of the PBE0 density functional due to the observed smallest color difference between computed and experimentally derived values. It was found that the alkali metal hydroxide molecules can bind to the two oxygen atoms of both hydroxyl groups of alizarin or to one of these atoms and the oxygen atom from the keto group in a complex with three methanol molecules. This means that two electronic transitions need to be taken into account when considering the spectra of the studied complexes. The resulting bond lengths and angles are correlated with the properties of the alkali metal atoms. The molar mass, the atomic radius, and the Pauling electronegativity of studied metals are quite accurate predictors of the geometric properties of hydroxide complexes with alizarin in methanol solution. Graphical abstract The spectra of the neutral and monoanionic form of alizarin together with color changes resulting from addition of different metal hydroxides and represented in CIE color space. PMID:27178415

  4. Theoretical study of alpha/beta-alanine and their protonated/alkali metal cationized complexes.

    PubMed

    Abirami, S; Xing, Y M; Tsang, C W; Ma, N L

    2005-01-27

    Density functional theory has been employed to model the structure and the relative stabilities of alpha/beta-alanine conformers and their protonated and alkali metal cationized complexes. In general, we find that the behavior of the beta-alanine (beta-Ala) system is quite similar to that of alpha-alanine (alpha-Ala). However, the presence of the methylene group (-CH2-) at the beta position in beta-Ala leads to a few key differences. First, the intramolecular hydrogen bonding patterns are different between free alpha- and beta-Ala. Second, the stability of zwitterionic species (in either the free ligand or alkali metal cationized complexes) is often enhanced in beta-Ala. Third, the preferred mode of alkali metal cation (M+) binding may also differ in alpha- and beta-Ala. Natural energy decomposition analysis has been applied here to gain further insight into the effects of the ligand, cation size, and mode of binding on the nature of interaction in these M+-Ala complexes. PMID:16833371

  5. Neuropsychiatric manifestations of alkali metal deficiency and excess.

    PubMed

    Yung, C Y

    1984-01-01

    The alkali metals from the Group IA of the periodic table (lithium, sodium, potassium, rubidium, cesium and francium) are reviewed. The neuropsychiatric aspects of alkali metal deficiencies and excesses (intoxications) are described. Emphasis was placed on lithium due to its clinical uses. The signs and symptoms of these conditions are characterized by features of an organic brain syndrome with delirium and encephalopathy prevailing. There are no clinically distinctive features that could be reliably used for diagnoses. Sodium and potassium are two essential alkali metals in man. Lithium is used as therapeutic agent in bipolar affective disorders. Rubidium has been investigated for its antidepressant effect in a group of psychiatric disorders. Cesium is under laboratory investigation for its role in carcinogenesis and in depressive illness. Very little is known of francium due to its great instability for experimental study. PMID:6395136

  6. Neuropsychiatric manifestations of alkali metal deficiency and excess

    SciTech Connect

    Yung, C.Y.

    1984-01-01

    The alkali metals from the Group IA of the periodic table (lithium, sodium, potassium, rubidium, cesium and francium) are reviewed. The neuropsychiatric aspects of alkali metal deficiencies and excesses (intoxications) are described. Emphasis was placed on lithium due to its clinical uses. The signs and symptoms of these conditions are characterized by features of an organic brain syndrome with delirium and encephalopathy prevailing. There are no clinically distinctive features that could be reliably used for diagnoses. Sodium and potassium are two essential alkali metals in man. Lithium is used as therapeutic agent in bipolar affective disorders. Rubidium has been investigated for its antidepressant effect in a group of psychiatric disorders. Cesium is under laboratory investigation for its role in carcinogenesis and in depressive illness. Very little is known of francium due to its great instability for experimental study.

  7. Interaction of alkali-metal overlayers with oxygen

    SciTech Connect

    Hrbek, J.; Xu, G.; Sham, T.K.; Shek, M.L.

    1989-05-01

    The interaction of oxygen with alkali metals (Li, Na, K, and Cs) was studied with valence and core-level photoemission (PE) using synchrotron radiation and by multiple mass thermal desorption (TDS). During a stepwise coadsorption of oxygen at 80 K, an increase in the emission intensity, a linewidth broadening, and a negative binding-energy shift of alkali-metal core levels is observed. Two stages of oxygen adsorption are identified in PE and TDS. In the low O/sub 2/ exposure range, an oxide species is formed; at higher exposures, peroxide and superoxide species are observed in Na, K, and Cs. The potassium--oxygen interaction is discussed in detail.

  8. Upgrading of petroleum oil feedstocks using alkali metals and hydrocarbons

    SciTech Connect

    Gordon, John Howard

    2014-09-09

    A method of upgrading an oil feedstock by removing heteroatoms and/or one or more heavy metals from the oil feedstock composition. This method reacts the oil feedstock with an alkali metal and an upgradant hydrocarbon. The alkali metal reacts with a portion of the heteroatoms and/or one or more heavy metals to form an inorganic phase separable from the organic oil feedstock material. The upgradant hydrocarbon bonds to the oil feedstock material and increases the number of carbon atoms in the product. This increase in the number of carbon atoms of the product increases the energy value of the resulting oil feedstock.

  9. Multi-photon processes in alkali metal vapors

    NASA Astrophysics Data System (ADS)

    Gai, Baodong; Hu, Shu; Li, Hui; Shi, Zhe; Cai, Xianglong; Guo, Jingwei; Tan, Yannan; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Achieving population inversion through multi-photon cascade pumping is almost always difficult, and most laser medium work under 1-photon excitation mechanism. But for alkali atoms such as cesium, relatively large absorption cross sections of several low, cascading energy levels enable them properties such as up conversion. Here we carried out research on two-photon excitation alkali fluorescence. Two photons of near infrared region are used to excite alkali atoms to n 2 D5/2, n 2 D3/2 or higher energy levels, then the blue fluorescence of (n+1) 2 P3/2,(n+1) 2 P1/2-->n 2 S1/2 are observed. Different pumping paths are tried and by the recorded spectra, transition routes of cesium are deducted and concluded. Finally the possibility of two-photon style DPALs (diode pumped alkali laser) are discussed, such alkali lasers can give output wavelengths in the shorter end of visual spectroscopy (400-460 nm) and are expected to get application in underwater communication and material laser processing.

  10. Structural models for alkali-metal complexes of polyacetylene

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1990-02-01

    Structural models for a stage-2 complex are proposed for polyacetylene doped with less than about 0.1 potassium or rubidium atoms per carbon. These structures utilize as a basic motif an alkali-metal column surrounded by four planar-zig-zag polyacetylene chains, a structure found at the highest dopant levels. In the new stage-2 structures, each polyacetylene chain neighbors only one alkali-metal column, so the phase contains four polymer chains per alkali-metal column. Basic structural aspects for stage-1 and stage-2 structures are now established for both potassium- and rubidium-doped polyacetylene. X-ray-diffraction and electrochemical data show that undoped and doped phases coexist at low dopant concentrations (<0.06 K atom per C). X-ray-diffraction data, down to a Bragg spacing of 1.3 Å, for polyacetylene heavily doped with potassium (0.125-0.167 K atom per C) is fully consistent with our previously proposed stage-1 tetragonal unit cell containing two polyacetylene chains per alkali-metal column. There is no evidence for our samples requiring a distortion to a monoclinic unit cell as reported by others for heavily doped samples. The nature of structural transformations and the relationship between structure and electronic properties are discussed for potassium-doped polyacetylene.

  11. Method of assembling and sealing an alkali metal battery

    DOEpatents

    Elkins, P.E.; Bell, J.E.; Harlow, R.A.; Chase, G.G.

    1983-03-01

    A method of initially assembling and then subsequently hermetically sealing a container portion of an alkali metal battery to a ceramic portion of such a battery is disclosed. Sealing surfaces are formed respectively on a container portion and a ceramic portion of an alkali metal battery. These sealing surfaces are brought into juxtaposition and a material is interposed there between. This interposed material is one which will diffuse into sealing relationship with both the container portion and the ceramic portion of the alkali metal battery at operational temperatures of such a battery. A pressure is applied between these sealing surfaces to cause the interposed material to be brought into intimate physical contact with such juxtaposed surfaces. A temporary sealing material which will provide a seal against a flow of alkali metal battery reactants there through at room temperatures and is applied over the juxtaposed sealing surfaces and material interposed there between. The entire assembly is heated to an operational temperature so that the interposed material diffuses into the container portion and the ceramic portion to form a hermetic seal there between. The pressure applied to the juxtaposed sealing surfaces is maintained in order to ensure the continuation of the hermetic seal. 4 figs.

  12. High capacity nickel battery material doped with alkali metal cations

    DOEpatents

    Jackovitz, John F.; Pantier, Earl A.

    1982-05-18

    A high capacity battery material is made, consisting essentially of hydrated Ni(II) hydroxide, and about 5 wt. % to about 40 wt. % of Ni(IV) hydrated oxide interlayer doped with alkali metal cations selected from potassium, sodium and lithium cations.

  13. Method of assembling and sealing an alkali metal battery

    DOEpatents

    Elkins, Perry E.; Bell, Jerry E.; Harlow, Richard A.; Chase, Gordon G.

    1983-01-01

    A method of initially assembling and then subsequently hermetically sealing a container portion of an alkali metal battery to a ceramic portion of such a battery is disclosed. Sealing surfaces are formed respectively on a container portion and a ceramic portion of an alkali metal battery. These sealing surfaces are brought into juxtaposition and a material is interposed therebetween. This interposed material is one which will diffuse into sealing relationship with both the container portion and the ceramic portion of the alkali metal battery at operational temperatures of such a battery. A pressure is applied between these sealing surfaces to cause the interposed material to be brought into intimate physical contact with such juxtaposed surfaces. A temporary sealing material which will provide a seal against a flow of alkali metal battery reactants therethrough at room temperatures and is applied over the juxtaposed sealing surfaces and material interposed therebetween. The entire assembly is heated to an operational temperature so that the interposed material diffuses into the container portion and the ceramic portion to form a hermetic seal therebetween. The pressure applied to the juxtaposed sealing surfaces is maintained in order to ensure the continuation of the hermetic seal.

  14. Aqueous alkali metal hydroxide insoluble cellulose ether membrane

    NASA Technical Reports Server (NTRS)

    Hoyt, H. E.; Pfluger, H. L. (Inventor)

    1969-01-01

    A membrane that is insoluble in an aqueous alkali metal hydroxide medium is described. The membrane is a resin which is a water-soluble C2-C4 hydroxyalkyl cellulose ether polymer and an insolubilizing agent for controlled water sorption, a dialytic and electrodialytic membrane. It is particularly useful as a separator between electrodes or plates in an alkaline storage battery.

  15. The role of alkali metal cations in the stabilization of guanine quadruplexes: why K(+) is the best.

    PubMed

    Zaccaria, F; Paragi, G; Fonseca Guerra, C

    2016-08-21

    The alkali metal ion affinity of guanine quadruplexes has been studied using dispersion-corrected density functional theory (DFT-D). We have done computational investigations in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. In both cases, an alkali metal cation is needed to assist self-assembly. Our quantum chemical computations on these supramolecular systems are able to reproduce the experimental order of affinity of the guanine quadruplexes for the cations Li(+), Na(+), K(+), Rb(+), and Cs(+). The strongest binding is computed between the potassium cation and the quadruplex as it occurs in nature. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Until now, the relative importance of these two factors has remained unclear and debated. By assessing the quantum chemical 'size' of the cation, determining the amount of deformation of the quadruplex needed to accommodate the cation and through the energy decomposition analysis (EDA) of the interaction energy between the cation and the guanines, we reveal that the desolvation and size of the alkali metal cation are both almost equally responsible for the order of affinity. PMID:27185388

  16. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting...

  17. 40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Fatty alkyl phosphate, alkali metal... Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... as a fatty alkyl phosphate, alkali metal salt (PMN P-99-0385) is subject to reporting under...

  18. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting...

  19. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting...

  20. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting...

  1. Controlling Metal-Halide Vapor Density in Lasers

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.

    1984-01-01

    Streams of buffer gas convect and dilute metal-halide vapor. Technique uses flow of buffer gas through reservoir, which contains heated metal halide, to convect vapors into discharge tube. Second stream of buffer gas dilutes vapor. Final vapor density in laser tube controlled and changed by adjusting either one or both of buffer gas flow rates.

  2. Alkali Metal Backup Cooling for Stirling Systems - Experimental Results

    NASA Technical Reports Server (NTRS)

    Schwendeman, Carl; Tarau, Calin; Anderson, William G.; Cornell, Peggy A.

    2013-01-01

    In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 C temperature increase from the nominal vapor temperature. The 19 C temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental

  3. Alkali Metal Backup Cooling for Stirling Systems - Experimental Results

    NASA Technical Reports Server (NTRS)

    Schwendeman, Carl; Tarau, Calin; Anderson, William G.; Cornell, Peggy A.

    2013-01-01

    In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental

  4. Half metallic ferromagnetism in alkali metal nitrides MN (M = Rb, Cs): A first principles study

    SciTech Connect

    Murugan, A. Rajeswarapalanichamy, R. Santhosh, M. Sudhapriyanga, G.; Kanagaprabha, S.

    2014-04-24

    The structural, electronic and elastic properties of two alkali metal nitrides (MN: M= Rb, Cs) are investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At ambient pressure the two nitrides are stable in ferromagnetic state with CsCl structure. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials are half metallic in nature. A pressure-induced structural phase transition from CsCl to ZB phase is observed in RbN and CsN.

  5. Intercalation of heavy alkali metals (K, Rb and Cs) in the bundles of single wall nanotubes

    NASA Astrophysics Data System (ADS)

    Duclaux, L.; Méténier, K.; Lauginie, P.; Salvetat, J. P.; Bonnamy, S.; Beguin, F.

    2000-11-01

    The electric-arc discharge carbon deposits (collaret) containing Single Wall Carbon Nanotubes (SWNTs) were heat treated at 1600 °C during 2 days under N2 flow in order to eliminate the Ni catalyst by sublimation, without modifications of the SWNTs ropes. Sorting this deposit by gravity enabled to obtain in the coarsest particles higher amount of SWNTs ropes than in other particle sizes. The coarser particles of the carbon deposits were reacted with the alkali metals vapor giving intercalated samples with a MC8 composition. The intercalation led to an expansion of the 2D lattice of the SWNTs so that the alkali metals were intercalated in between the tubes within the bundles. Disordered lattices were observed after intercalation of Rb and Cs. The simulations of the X-ray diffractograms of SWNTs reacted with K, gave the best fit for three K ions occupying the inter-tubes triangular cavities. The investigations by EPR, and 13C NMR, showed that doped carbon deposits are metallic.

  6. Wetting Transitions of Inert Gases on Alkali Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Bojan, M. J.; McDonald, I. A.; Cole, M. W.; Steele, W. A.

    1996-03-01

    Theoretical and experimental discoveries have been made recently of wetting and prewetting transitions of helium and hydrogen films on alkali metal surfaces [1,2]. New experiments show anomalous nonwetting behavior of Ne on Rb and Cs [3]. Building on earlier work [4], we have done and will describe results from the first Monte Carlo simulations showing wetting transitions for classical gases on alkali metal surfaces. * Research supported by an NSF Materials Research Group grant. 1. R. B.Hallock, J. Low Temp. Phys. 101, 31, 1995 2. M. W. Cole, J. Low Temp. Phys. 101, 25, 1995. 3. G. B. Hess, M. Sabatini, and M. H. W. Chan, unpublished 4. J. E. Finn and P. A. Monson, Phys. Rev. A 39, 6402, 1989.

  7. Superconductivity above 30 K in alkali-metal-doped hydrocarbon

    PubMed Central

    Xue, Mianqi; Cao, Tingbing; Wang, Duming; Wu, Yue; Yang, Huaixin; Dong, Xiaoli; He, Junbao; Li, Fengwang; Chen, G. F.

    2012-01-01

    The recent discovery of superconductivity with a transition temperature (Tc) at 18 K in Kxpicene has extended the possibility of high-Tc superconductors in organic materials. Previous experience based on similar hydrocarbons, like alkali-metal doped phenanthrene, suggested that even higher transition temperatures might be achieved in alkali-metals or alkali-earth-metals doped such polycyclic-aromatic-hydrocarbons (PAHs), a large family of molecules composed of fused benzene rings. Here we report the discovery of high-Tc superconductivity at 33 K in K-doped 1,2:8,9-dibenzopentacene (C30H18). To our best knowledge, it is higher than any Tc reported previously for an organic superconductor under ambient pressure. This finding provides an indication that superconductivity at much higher temperature may be possible in such PAHs system and is worthy of further exploration. PMID:22548129

  8. The structure of metallic complexes of polyacetylene with alkali metals

    NASA Astrophysics Data System (ADS)

    Baughman, R. H.; Murthy, N. S.; Miller, G. G.

    1983-07-01

    The crystal structures of sodium, potassium, rubidium, and cesium doped polyacetylene have been determined using crystal packing and x-ray diffraction analyses. Each of these metallic complexes is tetragonal, with the polyacetylene chains forming a host lattice in which the alkali metal ions are present in channels. Lithium appears to be too small to stabilize the channel structure and an amorphous structure is observed. Predicted unit cell parameters and x-ray diffraction intensities are in agreement with observed values. Similarities with the alkali metal doped graphite suggest that hybridization between carbon pz orbitals and metal s orbitals occurs. Such hybridization is expected to result in a high conductivity component normal to the chain direction. On the other hand, direct overlap between polymer chains appears small, since alkali metal columns separate polymer chains. Compositions calculated for the channel structures (from meridional diffraction spacings, the intensity of equatorial diffraction lines, measured volume expansion, and distances in model complexes) all range from y=0.12 to 0.18 for (CHMy)x, where M is sodium, potassium, rubidium, or cesium.

  9. Process for carbonaceous material conversion and recovery of alkali metal catalyst constituents held by ion exchange sites in conversion residue

    DOEpatents

    Sharp, David W.

    1980-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered for the particles by contacting or washing them with an aqueous solution containing calcium or magnesium ions in an alkali metal recovery zone at a low temperature, preferably below about 249.degree. F. During the washing or leaching process, the calcium or magnesium ions displace alkali metal ions held by ion exchange sites in the particles thereby liberating the ions and producing an aqueous effluent containing alkali metal constituents. The aqueous effluent from the alkali metal recovery zone is then recycled to the conversion process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst.

  10. Alkali Metal Based Micro Combustion Using Graphene Micro-valve Trigger

    NASA Astrophysics Data System (ADS)

    Ruyack, A.; Gund, V.; Camera, K.; Ardanuç, S.; Ober, C.; Lal, A.

    2015-12-01

    Controllable combustion of alkali metals offers a pathway to high energy density, high power density scalable thermal systems. The volatile nature of these materials however, has limited their incorporation into useable devices. Recent findings in low trigger power MEMS one-shot valves offer a viable pathway forward for creating systems in which to exploit the unique properties of alkali metals as thermal energy sources. By miniaturizing and combining these fuels with such a valve, and incorporating them with a polymer substrate, a micro-packet of combustible metal can be created. Here we report such a device utilizing a graphene based micro-valve trigger and a rubidium metal fuel source to realize an arrayable micro-scale electrical to thermal energy amplification scheme. Using this approach we can react nanoliter droplets of rubidium with ambient air on demand, producing electrical to thermal energy gains of seventy five times. By arraying the fuel into discrete packets, we can also achieve temporal control of the fuel source, allowing for tailored peak and average power output.

  11. Transport properties of alkali metal doped fullerides

    SciTech Connect

    Yadav, Daluram Yadav, Nishchhal

    2015-07-31

    We have studied the intercage interactions between the adjacent C{sub 60} cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C{sub 60} phonons. We considered a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. Coulomb repulsive parameter and the electron phonon coupling strength are obtained within the random phase approximation. Transition temperature, T{sub c}, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C{sub 60} phonons as 5 K, which is much lower as compared to reported T{sub c} (20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. The importance of the present study, the pressure effect and normal state transport properties are calculated within the same model leading superconductivity.

  12. Transport properties of alkali metal doped fullerides

    NASA Astrophysics Data System (ADS)

    Yadav, Daluram; Yadav, Nishchhal

    2015-07-01

    We have studied the intercage interactions between the adjacent C60 cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C60 phonons. We considered a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. Coulomb repulsive parameter and the electron phonon coupling strength are obtained within the random phase approximation. Transition temperature, Tc, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C60 phonons as 5 K, which is much lower as compared to reported Tc (20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. The importance of the present study, the pressure effect and normal state transport properties are calculated within the same model leading superconductivity.

  13. The relationship between molecular structure and biological activity of alkali metal salts of vanillic acid: Spectroscopic, theoretical and microbiological studies

    NASA Astrophysics Data System (ADS)

    Świsłocka, Renata; Piekut, Jolanta; Lewandowski, Włodzimierz

    In this paper we investigate the relationship between molecular structure of alkali metal vanillate molecules and their antimicrobial activity. To this end FT-IR, FT-Raman, UV absorption and 1H, 13C NMR spectra for lithium, sodium, potassium, rubidium and caesium vanillates in solid state were registered, assigned and analyzed. Microbial activity of studied compounds was tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Proteus vulgaris, Bacillus subtilis and Candida albicans. In order to evaluate the dependence between chemical structure and biological activity of alkali metal vanillates the statistical analysis was performed for selected wavenumbers from FT-IR spectra and parameters describing microbial activity of vanillates. The geometrical structures of the compounds studied were optimized and the structural characteristics were determined by density functional theory (DFT) using at B3LYP method with 6-311++G** as basis set. The obtained statistical equations show the existence of correlation between molecular structure of vanillates and their biological properties.

  14. Recent materials compatibility studies in refractory metal-alkali metal systems for space power applications.

    NASA Technical Reports Server (NTRS)

    Harrison, R. W.; Hoffman, E. E.; Davies, R. L.

    1972-01-01

    Advanced Rankine and other proposed space power systems utilize refractory metals in contact with both single-phase and two-phase alkali metals at elevated temperatures. A number of recent compatibility experiments are described which emphasize the excellent compatibility of refractory metals with the alkali metals, lithium, sodium, and potassium, under a variety of environmental conditions. The alkali metal compatibilities of tantalum-, columbium-, molybdenum-, and tungsten-base alloys are discussed.

  15. Alkali metal/halide thermal energy storage systems performance evaluation

    NASA Technical Reports Server (NTRS)

    Phillips, W. M.; Stearns, J. W.

    1986-01-01

    A pseudoheat-pipe heat transfer mechanism has been demonstrated effective in terms of both total heat removal efficiency and rate, on the one hand, and system isothermal characteristics, on the other, for solar thermal energy storage systems of the kind being contemplated for spacecraft. The selection of appropriate salt and alkali metal substances for the system renders it applicable to a wide temperature range. The rapid heat transfer rate obtainable makes possible the placing of the thermal energy storage system around the solar receiver canister, and the immersing of heat transfer fluid tubes in the phase change salt to obtain an isothermal heat source.

  16. Optical response of alkali metal atoms confined in nanoporous glass

    SciTech Connect

    Burchianti, A; Marinelli, C; Mariotti, E; Bogi, A; Marmugi, L; Giomi, S; Maccari, M; Veronesi, S; Moi, L

    2014-03-28

    We study the influence of optical radiation on adsorption and desorption processes of alkali metal atoms confined in nanoporous glass matrices. Exposure of the sample to near-IR or visible light changes the atomic distribution inside the glass nanopores, forcing the entire system to evolve towards a different state. This effect, due to both atomic photodesorption and confinement, causes the growth and evaporation of metastable nanoparticles. It is shown that, by a proper choice of light characteristics and pore size, these processes can be controlled and tailored, thus opening new perspectives for fabrication of nanostructured surfaces. (nanoobjects)

  17. Chemical compatibility of structural materials in alkali metals

    SciTech Connect

    Natesan, K.; Rink, D.L.; Haglund, R.

    1995-04-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments.

  18. Nuclear alkali metal Rankine power systems for space applications

    SciTech Connect

    Moyers, J.C.; Holcomb, R.S.

    1986-08-01

    Nucler power systems utilizing alkali metal Rankine power conversion cycles offer the potential for high efficiency, lightweight space power plants. Conceptual design studies are being carried out for both direct and indirect cycle systems for steady state space power applications. A computational model has been developed for calculating the performance, size, and weight of these systems over a wide range of design parameters. The model is described briefly and results from parametric design studies, with descriptions of typical point designs, are presented in this paper.

  19. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  20. Theoretical determination of the alkali-metal superoxide bond energies

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Sodupe, Mariona; Langhoff, Stephen R.

    1992-01-01

    The bond dissociation energies for the alkali-metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional level. Our computed D0 values are 61.4, 37.2, 40.6, and 38.4 kcal/mol for LiO2, NaO2, KO2, and RbO2, respectively. These values, which are expected to be lower bounds and accurate to 2 kcal/mol, agree well with some of the older flame data, but rule out several recent experimental measurements.

  1. Laser synthesis of ultracold alkali metal dimers: optimization and control

    NASA Astrophysics Data System (ADS)

    Pazyuk, E. A.; Zaitsevskii, A. V.; Stolyarov, A. V.; Tamanis, M.; Ferber, R.

    2015-10-01

    The review concerns the potential of modern high-resolution laser spectroscopy and state-of-the-art ab initio electronic structure calculations used to obtain comprehensive information on the energy and radiative properties of strongly coupled rovibronic diatomic states. The possibility of deperturbation treatment of the intermediate electronically excited states at the experimental (spectroscopic) level of accuracy is demonstrated taking alkali metal dimers as examples. The deperturbation analysis is of crucial importance to optimize multistep laser synthesis and stabilization of ultracold molecular ensembles in their absolute ground level. The bibliography includes 227 references.

  2. Alkali-metal silicate binders and methods of manufacture

    NASA Technical Reports Server (NTRS)

    Schutt, J. B. (Inventor)

    1979-01-01

    A paint binder is described which uses a potassium or sodium silicate dispersion having a silicon dioxide to alkali-metal oxide mol ratio of from 4.8:1 to 6.0:1. The binder exhibits stability during both manufacture and storage. The process of making the binder is predictable and repeatable and the binder may be made with inexpensive components. The high mol ratio is achieved with the inclusion of a silicon dioxide hydrogel. The binder, which also employs a silicone, is in the final form of a hydrogel sol.

  3. Nonlinear pressure shifts of alkali-metal atoms in xenon

    NASA Astrophysics Data System (ADS)

    McGuyer, Bart; Xia, Tian; Jau, Yuan-Yu; Happer, William

    2011-05-01

    Compact, portable atomic frequency standards are based on the microwave resonance frequencies of alkali-metal atoms in inert buffer gases. The frequency shift of these resonances due to collisions with the buffer gas is known as the pressure shift. We demonstrate that the microwave resonance frequencies of ground-state 87Rb and 133Cs atoms have a nonlinear dependence on the pressure of the buffer gas Xe. Previous work has demonstrated a nonlinear dependence in Ar and Kr, but not He and N2, which is thought to be due to the loosely-bound van der Waals molecules that are known to form between alkali-metal and buffer-gas atoms in Ar, Kr, and Xe, but not He and N2. Surprisingly, we find that the nonlinearities in Xe are of the opposite sign to those in Ar and Kr, even though the overall shifts for each of these gases are negative. This discrepancy suggests that though the shifts due to the molecules in Ar and Kr are positive, the shifts due to the molecules in Xe are negative. No nonlinearities were observed in the buffer gas Ne to within our experimental accuracy, which suggests that molecules do not form in Ne. Additionally, we present improved measurements of the shifts of Rb and Cs in He and N2 and of Rb in Ar and Kr. This work was supported by the Air Force Office of Scientific Research and the Department of Defense through the NDSEG program.

  4. Substitution mechanism of alkali metals for strontium in strontium hydroxyapatite

    SciTech Connect

    Naddari, Thouraya; Hamdi, Besma; Savariault, Jean Michel; El Feki, Hafed; Ben Salah, Abdelhamid

    2003-01-25

    Strontium hydroxyapatites substituted by alkali metals are synthesized by double decomposition method in basic medium. Structures of Sr{sub 9.50}Na{sub 0.30}(PO{sub 4}){sub 6}(OH){sub 1.30} (SrNaHAp) and Sr{sub 9.81}K{sub 0.12}(PO{sub 4}){sub 6}(OH){sub 1.74} (SrKHAp) are determined by X-ray powder diffraction. Both compounds are isotypic and crystallize in hexagonal system (space group P63/m) with the following cells: a=9.751(3) A and c=7.279(3) A for SrNaHAp and a=9.755(4) A and c=7.284(3) A for SrKHAp. Results are compared to those of Sr{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}. According to the site occupancy factors, in SrNaHAp sodium is localized in site (I) and in SrKHAp potassium in site (II). Both structures contain vacancies in hydroxyl and metal sites. The mechanism of alkali metals substitution for strontium proposed explains the vacancies formation.

  5. Universalities in ultracold reactions of alkali-metal polar molecules

    NASA Astrophysics Data System (ADS)

    Quéméner, Goulven; Bohn, John L.; Petrov, Alexander; Kotochigova, Svetlana

    2011-12-01

    We consider ultracold collisions of ground-state heteronuclear alkali-metal dimers that are susceptible to four-center chemical reactions 2AB→A2+B2 even at submicrokelvin temperatures. These reactions depend strongly on species, temperature, electric field, and confinement in an optical lattice. We calculate ab initio van der Waals coefficients for these interactions and use a quantum formalism to study the scattering properties of such molecules under an external electric field and optical lattice. We also apply a quantum threshold model to explore the dependence of reaction rates on the various parameters. We find that, among the heteronuclear alkali-metal fermionic species, LiNa is the least reactive, whereas LiCs is the most reactive. For the bosonic species, LiK is the most reactive in zero field, but all species considered, LiNa, LiK, LiRb, LiCs, and KRb, share a universal reaction rate once a sufficiently high electric field is applied. For indistinguishable bosons, the inelastic/reactive rate increases as d2 in the quantum regime, where d is the dipole moment induced by the electric field. This is a weaker power-law dependence than for indistinguishable fermions, for which the rate behaves as d6.

  6. Difficulties in Interpreting Alkali Metal Trends at the Senior Chemistry Level.

    ERIC Educational Resources Information Center

    de Berg, Kevin

    2001-01-01

    Explores the reasons for the differences in alkali metal reactivity in water in terms of thermodynamics rather than ionization trends. Shows that differences in alkali metal reactivity with water are more appropriately explained in terms of the kinetics of the reactions. (MM)

  7. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal salt of...

  8. 40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... metal salts. 721.4663 Section 721.4663 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical... fluorinated carboxylic acid alkali metal salts (PMNs P-95-979/980/981) are subject to reporting under...

  9. 40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... salt (generic). 721.5985 Section 721.5985 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... as a fatty alkyl phosphate, alkali metal salt (PMN P-99-0385) is subject to reporting under...

  10. 40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... salt (generic). 721.5985 Section 721.5985 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... as a fatty alkyl phosphate, alkali metal salt (PMN P-99-0385) is subject to reporting under...

  11. 40 CFR 721.10097 - Disubstituted benzenesulfonic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., alkali metal salt (generic). 721.10097 Section 721.10097 Protection of Environment ENVIRONMENTAL... metal salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as disubstituted benzenesulfonic acid, alkali metal salt (PMN...

  12. 40 CFR 721.10097 - Disubstituted benzenesulfonic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., alkali metal salt (generic). 721.10097 Section 721.10097 Protection of Environment ENVIRONMENTAL... metal salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as disubstituted benzenesulfonic acid, alkali metal salt (PMN...

  13. 40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... metal salts. 721.4663 Section 721.4663 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical... fluorinated carboxylic acid alkali metal salts (PMNs P-95-979/980/981) are subject to reporting under...

  14. 40 CFR 721.10098 - Disubstituted benzoic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... metal salt (generic). 721.10098 Section 721.10098 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10098 Disubstituted benzoic acid, alkali metal salt... identified generically as disubstituted benzoic acid, alkali metal salt (PMN P-03-643) is subject...

  15. 40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... salt (generic). 721.5985 Section 721.5985 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... as a fatty alkyl phosphate, alkali metal salt (PMN P-99-0385) is subject to reporting under...

  16. 40 CFR 721.10098 - Disubstituted benzoic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... metal salt (generic). 721.10098 Section 721.10098 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10098 Disubstituted benzoic acid, alkali metal salt... identified generically as disubstituted benzoic acid, alkali metal salt (PMN P-03-643) is subject...

  17. 40 CFR 721.10098 - Disubstituted benzoic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... metal salt (generic). 721.10098 Section 721.10098 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10098 Disubstituted benzoic acid, alkali metal salt... identified generically as disubstituted benzoic acid, alkali metal salt (PMN P-03-643) is subject...

  18. 40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... metal salts. 721.4663 Section 721.4663 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical... fluorinated carboxylic acid alkali metal salts (PMNs P-95-979/980/981) are subject to reporting under...

  19. 40 CFR 721.10098 - Disubstituted benzoic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... metal salt (generic). 721.10098 Section 721.10098 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10098 Disubstituted benzoic acid, alkali metal salt... identified generically as disubstituted benzoic acid, alkali metal salt (PMN P-03-643) is subject...

  20. 40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... metal salts. 721.4663 Section 721.4663 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a) Chemical... fluorinated carboxylic acid alkali metal salts (PMNs P-95-979/980/981) are subject to reporting under...

  1. 40 CFR 721.10097 - Disubstituted benzenesulfonic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., alkali metal salt (generic). 721.10097 Section 721.10097 Protection of Environment ENVIRONMENTAL... metal salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as disubstituted benzenesulfonic acid, alkali metal salt (PMN...

  2. 40 CFR 721.10097 - Disubstituted benzenesulfonic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., alkali metal salt (generic). 721.10097 Section 721.10097 Protection of Environment ENVIRONMENTAL... metal salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as disubstituted benzenesulfonic acid, alkali metal salt (PMN...

  3. Crystal Structures of Three Framework Alkali Metal Uranyl Phosphate Hydrates

    NASA Astrophysics Data System (ADS)

    Locock, Andrew J.; Burns, Peter C.

    2002-08-01

    Three homeotypic hydrated alkali metal uranyl phosphates, A2(UO 2)[(UO 2)(PO 4)] 4(H 2O) 2, A=Cs ( CsUP), Rb ( RbUP), K ( KUP), were synthesized by hydrothermal methods. Intensity data were collected at room temperature using Mo Kα radiation and a CCD-based area detector. Their crystal structures were solved by Patterson ( CsUP) and direct ( RbUP, KUP) methods and refined by full-matrix least-squares techniques to agreement indices ( CsUP, RbUP, KUP) w R2=0.048, 0.230, 0.072 for all data, and R1=0.023, 0.078, 0.038 calculated for 5338, 4738, 4514 unique observed reflections (∣ Fo∣≥4 σF), respectively. The compound CsUP is orthorhombic, space group Cmc2 1, Z=4, a=14.854(1), b=13.879(1), c=12.987(1) Å, V=2677.5(3) Å 3. Both RbUP and KUP are monoclinic, space group Cm, but are presented in the unconventional pseudo-orthorhombic space group Fm11 to facilitate comparison with CsUP and to allow a model for RbUP that includes the effects of pseudo-merohedral twinning. RbUP is monoclinic, space group Fm11, Z=4, a=15.72(2), b=13.84(1), c=13.05(1) Å, α=90.39°(2), V=2839(5) Å 3; KUP is monoclinic, space group Fm11, Z=4, a=15.257(1), b=13.831(1), c=13.007(1) Å, α=91.760°(1), V=2743.4(3) Å 3. The structures consist of sheets of phosphate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO 2)(PO 4)] -, that are topologically identical to the uranyl silicate sheets in uranophane-beta. These sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with two phosphate tetrahedra on each of two adjacent sheets and whose fifth equatorial vertex is an H 2O group, resulting in an open framework with alkali metal cations in the larger cavities of the structures. Where CsUP and RbUP have two alkali metal positions and a H 2O group in these cavities, KUP has four K atoms and two H 2O groups, all of which are partially occupied, in the interstitial sites.

  4. First-principles study of d0 ferromagnetism in alkali-metal doped GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Yong

    2016-08-01

    The d0 ferromagnetism in GaN has been studied based on density functional theory. Our results show that GaN with sufficient hole become spin-polarized. Alkali-metal doping can introduce holes in GaN. Among them, both of Li- and Na-doping induce ferromagnetism in GaN and Na-doped GaN behaves as half-metallic ferromagnet. Moreover, at a growth temperature of 2000 K under N-rich condition, both concentrations can exceed 18%, which is sufficient to produce detectable macroscopic magnetism in GaN. The Curie temperature of Li- and Na-doped GaN is estimated to be 304 and 740 K, respectively, which are well above room temperature.

  5. The alkali metal thermoelectric converter /AMTEC/ - A new direct energy conversion technology for aerospace power

    NASA Technical Reports Server (NTRS)

    Bankston, C. P.; Cole, T.; Jones, R.; Ewell, R.

    1982-01-01

    A thermally regenerative electrochemical device for the direct conversion of heat to electrical energy, the alkali metal thermoelectric converter (AMTEC), is characterized by potential efficiencies on the order of 15-40% and possesses no moving parts, making it a candidate for space power system applications. Device conversion efficiency is projected on the basis of experimental voltage vs current curves exhibiting power densities of 0.7 W/sq cm and measured electrode efficiencies of up to 40%. Preliminary radiative heat transfer measurements presented may be used in an investigation of methods for the reduction of AMTEC parasitic radiation losses. AMTEC assumes heat input and rejection temperatures of 900-1300 K and 400-800 K, respectively. The working fluid is liquid sodium, and the porous electrode employed is of molybdenum.

  6. Mechanical stiffening and thermal softening of superionic alkali metal oxides

    NASA Astrophysics Data System (ADS)

    Chaudhary, S.; Shriya, S.; Kumar, J.; Ameri, M.; Varshney, Dinesh

    2015-06-01

    The mechanical (pressure) and thermal (temperature) dependent nature of superionic cubic M2O (M = Li, Na, K, and Rb) alkali metal oxides is studied. The model Hamiltonian in ab initio theory include long-range Coulomb, charge transfer, covalency, van der Waals interaction and the short-range repulsive interaction upto second-neighbor ions. The second order elastic constants as functions of pressure discern increasing trend, while to that they decreases with enhanced temperature. From the knowledge of elastic constants, Pugh ratio, Poisson's ratio, heat capacity and thermal expansion coefficient are calculated. It is noticed that cubic M2O is brittle on applied pressure and temperature and mechanically stiffened as a consequence of bond compression and bond strengthening and thermally softened due to bond expansion and bond weakening due to lattice vibrations.

  7. Thermodynamics of Liquid Alkali Metals and Their Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakor, P. B.; Patel, Minal H.; Gajjar, P. N.; Jani, A. R.

    2009-07-01

    The theoretical investigation of thermodynamic properties like internal energy, entropy, Helmholtz free energy, heat of mixing (ΔE) and entropy of mixing (ΔS) of liquid alkali metals and their binary alloys are reported in the present paper. The effect of concentration on the thermodynamic properties of Ac1Bc2 alloy of the alkali-alkali elements is investigated and reported for the first time using our well established local pseudopotential. To investigate influence of exchange and correlation effects, we have used five different local field correction functions viz; Hartree(H), Taylor(T), Ichimaru and Utsumi(IU), Farid et al. (F) and Sarkar et al. (S). The increase of concentration C2, increases the internal energy and Helmholtz free energy of liquid alloy Ac1Bc2. The behavior of present computation is not showing any abnormality in the outcome and hence confirms the applicability of our model potential in explaining the thermodynamics of liquid binary alloys.

  8. Alkali metal-refractory metal biphase electrode for AMTEC

    NASA Technical Reports Server (NTRS)

    Williams, Roger M. (Inventor); Bankston, Clyde P. (Inventor); Cole, Terry (Inventor); Khanna, Satish K. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Wheeler, Bob L. (Inventor)

    1989-01-01

    An electrode having increased output with slower degradation is formed of a film applied to a beta-alumina solid electrolyte (BASE). The film comprises a refractory first metal M.sup.1 such as a platinum group metal, suitably platinum or rhodium, capable of forming a liquid or a strong surface adsorption phase with sodium at the operating temperature of an alkali metal thermoelectric converter (AMTEC) and a second refractory metal insoluble in sodium or the NaM.sup.1 liquid phase such as a Group IVB, VB or VIB metal, suitably tungsten, molybdenum, tantalum or niobium. The liquid phase or surface film provides fast transport through the electrode while the insoluble refractory metal provides a structural matrix for the electrode during operation. A trilayer structure that is stable and not subject to deadhesion comprises a first, thin layer of tungsten, an intermediate co-deposited layer of tungsten-platinum and a thin surface layer of platinum.

  9. Generalized oscillator strengths and photoionization of alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Tiwary, S. N.; Nicolaides, C. A.

    1984-10-01

    Calculations of the continuum generalized oscillator strengths (CGOS) for ns → kp dipole transitions as a function of the momentum transfer K and the photoionization cross sections σ nl of the light alkali-metal atoms (Li, Na and K, with n = 2, 3, 4 respectively) have been performed within the framework of the first Born approximation (FBA) and the Vainshtein approximation (VPSA) employing Hartree-Fock (HF) wave functions. Also the influence of core-polarization is examined. Our present results exhibit the existence of the minimum and the maximum in the CGOS curve, the Cooper minimum in the σ nl curves of Na and K, the important role of core-polarization and finally, the dependence of the VPSA CGOS on the incident energy.

  10. Alkali Metal Thermoelectric Conversion (AMTEC) for space nuclear power systems

    NASA Technical Reports Server (NTRS)

    Bankston, C. P.; Cole, T.; Khanna, S. K.; Thakoor, A. P.

    1985-01-01

    Performance parameters of the Alkali Metal Thermoelectric Converter (AMTEC) for a 100 kW electric power system have been calculated at four technological levels assuming a heat pipe-cooled nuclear reactor heat source. The most advanced level considered would operate between 1180 K converter temperature and 711 K radiator temperature at 16 percent efficiency, and would weigh 1850 kg with a radiator area of 43 sq m. In addition, electrode research studies for the AMTEC systems have been conducted utilizing an experimental test cell of Bankston et al. (1983) and Mo and several Mo-Ti electrodes. It was found that the Mo-Ti electrodes offered no improvement in lifetime characteristics over the pure Mo electrodes, however, oxygen treatment of a degraded Mo electrode restored its specific power output to 90 percent of its original specific power and maintained this level for 60 hr, thus offering a potential for lifetime stability.

  11. Cold collisions of alkali-metal atoms and chromium atoms

    NASA Astrophysics Data System (ADS)

    Jeung, G.-H.; Hagebaum-Reignier, D.; Jamieson, M. J.

    2010-12-01

    We present ab initio potentials for ground state lithium, sodium, potassium and rubidium atoms interacting with ground state chromium atoms via the 6Σ+ and 8Σ+ states of the corresponding dimers. Each potential is matched to the leading van der Waals dispersion energy -C6/R6 - C8/R8 and an exchange energy; we list the values of C6, C8 and the exchange fitting parameters. We present calculated values from quantal and semi-classical approximations for the s-wave scattering length and effective range and the p-wave scattering volume for collisions of each of the alkali-metal atoms lithium, sodium, potassium and rubidium with 52chromium atoms and comment on s-wave scattering by 53chromium atoms.

  12. 3718-F Alkali Metal Treatment and Storage Facility Closure Plan

    SciTech Connect

    1991-12-01

    Since 1987, Westinghouse Hanford Company has been a major contractor to the U.S. Department of Energy-Richland Operations Office and has served as co-operator of the 3718-F Alkali Metal Treatment and Storage Facility, the waste management unit addressed in this closure plan. The closure plan consists of a Part A Dangerous waste Permit Application and a RCRA Closure Plan. An explanation of the Part A Revision (Revision 1) submitted with this document is provided at the beginning of the Part A section. The closure plan consists of 9 chapters and 5 appendices. The chapters cover: introduction; facility description; process information; waste characteristics; groundwater; closure strategy and performance standards; closure activities; postclosure; and references.

  13. Relativistic optimized effective potential method-application to alkali metals.

    PubMed

    Ködderitzsch, D; Ebert, H; Akai, H; Engel, E

    2009-02-11

    We present a relativistic formulation of the optimized effective potential method (ROEP) and its implementation within the Korringa-Kohn-Rostoker multiple scattering formalism. The scheme is an all-electron approach, treating core and band states formally on the same footing. We use exact exchange (EXX) as an approximation to the exchange correlation functional. Numerical four-component wavefunctions for the description of core and valence electrons and the corresponding ingredients of the ROEP integral equation are employed. The exact exchange expression for the valence states is reformulated in terms of the electronic Green's function that in turn is evaluated by making use of multiple scattering formalism. We present and discuss the application of the formalism to non-magnetic alkali metals. PMID:21715911

  14. An Alkali Metal-Capped Cerium(IV) Imido Complex.

    PubMed

    Solola, Lukman A; Zabula, Alexander V; Dorfner, Walter L; Manor, Brian C; Carroll, Patrick J; Schelter, Eric J

    2016-06-01

    Structurally authenticated, terminal lanthanide-ligand multiple bonds are rare and expected to be highly reactive. Even capped with an alkali metal cation, poor orbital energy matching and overlap of metal and ligand valence orbitals should result in strong charge polarization within such bonds. We expand on a new strategy for isolating terminal lanthanide-ligand multiple bonds using cerium(IV) complexes. In the current case, our tailored tris(hydroxylaminato) ligand framework, TriNOx(3-), provides steric protection against ligand scrambling and metal complex oligomerization and electronic protection against reduction. This strategy culminates in isolation of the first formal Ce═N bonded moiety in the complex [K(DME)2][Ce═N(3,5-(CF3)2C6H3)(TriNOx)], whose Ce═N bond is the shortest known at 2.119(3) Å. PMID:27163651

  15. Probe for measurement of velocity and density of vapor in vapor plume

    DOEpatents

    Berzins, Leon V.; Bratton, Bradford A.; Fuhrman, Paul W.

    1997-01-01

    A probe which directs a light beam through a vapor plume in a first direction at a first angle ranging from greater than 0.degree. to less than 90.degree., reflecting the light beam back through the vapor plume at a 90.degree. angle, and then reflecting the light beam through the vapor plume a third time at a second angle equal to the first angle, using a series of mirrors to deflect the light beam while protecting the mirrors from the vapor plume with shields. The velocity, density, temperature and flow direction of the vapor plume may be determined by a comparison of the energy from a reference portion of the beam with the energy of the beam after it has passed through the vapor plume.

  16. Probe for measurement of velocity and density of vapor in vapor plume

    DOEpatents

    Berzins, L.V.; Bratton, B.A.; Fuhrman, P.W.

    1997-03-11

    A probe is disclosed which directs a light beam through a vapor plume in a first direction at a first angle ranging from greater than 0{degree} to less than 90{degree}, reflecting the light beam back through the vapor plume at a 90{degree} angle, and then reflecting the light beam through the vapor plume a third time at a second angle equal to the first angle, using a series of mirrors to deflect the light beam while protecting the mirrors from the vapor plume with shields. The velocity, density, temperature and flow direction of the vapor plume may be determined by a comparison of the energy from a reference portion of the beam with the energy of the beam after it has passed through the vapor plume. 10 figs.

  17. Modification of conductive properties of (10, 0) zigzag single-walled carbon nanotubes (SWCNT) by alkali metals absorption

    NASA Astrophysics Data System (ADS)

    Hamadanian, Masood; Tavangar, Zahra; Noori, Banafsheh

    2014-11-01

    We have investigated the electronic and structural properties of (10, 0) zigzag single-walled carbon nanotubes (SWCNT) which have adsorbed different alkali metals (X: Li, Na, K, and Cs) and the hydrogen atom by using Density Functional Theory (DFT). It was discovered that among the alkali elements, Li atoms form the strongest bond with SWCNT. In addition, a significant shift was observed in the electronic state of alkali-adsorbed SWCNT compared to pristine SWCNT. Finally, it was proposed that due to showing excellent electronic structure, these modified nanotubes can be applied in new electronic devices, such as transistors, and field emission displays.

  18. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    NASA Astrophysics Data System (ADS)

    Liu, X. H.; Luo, H.; Qu, T. L.; Yang, K. Y.; Ding, Z. C.

    2015-10-01

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  19. Field desorption microscopy of graphene on iridium in intercalation with alkali metals

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2014-12-01

    Field-desorption and field-emission electron microscopy methods have been used to study the effect of a strong electric field on the processes of potassium and cesium desorption from the graphene surface on an iridium field emitter. It was found that two phases of field desorption may exist for these alkali metals. In the low-field phase, alkali metal atoms adsorbed on the surface are desorbed. The existence of the high-field phase is attributed to the egress from under the graphene film and ionization of intercalated alkali metal atoms under the action of the electric field.

  20. Calculation of radiative corrections to E1 matrix elements in the neutral alkali metals

    SciTech Connect

    Sapirstein, J.; Cheng, K.T.

    2005-02-01

    Radiative corrections to E1 matrix elements for ns-np transitions in the alkali-metal atoms lithium through francium are evaluated. They are found to be small for the lighter alkali metals but significantly larger for the heavier alkali metals, and in the case of cesium much larger than the experimental accuracy. The relation of the matrix element calculation to a recent decay rate calculation for hydrogenic ions is discussed, and application of the method to parity nonconservation in cesium is described.

  1. Negative electrodes for non-aqueous secondary batteries composed on conjugated polymer and alkali metal alloying or inserting material

    SciTech Connect

    Shacklette, L.W.; Jow, T.R.; Toth, E.; Maxfield, M.

    1987-05-26

    A battery is described comprising: an anode comprising as the anode active materials one or more conjugated backbone polymers and one or more electroactive materials selected from the group consisting of metals which alloy with alkali metals and alkali metal cation inserting materials; an electrolyte comprising an organic solvent and an alkali-metal salt, and a cathode. The alkali-metal cations from the electrolyte are inserted into the anode as a metal alloy or as an inserted ion in the alkali metal cation inserting material during the charging of the battery.

  2. Zintl cluster chemistry in the alkali-metal-gallium systems

    SciTech Connect

    Henning, R.

    1998-03-27

    Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga{sub 11}{sup 13{minus}} to Ga{sub 11}{sup 7{minus}} is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na{sub 10}Ga{sub 10}Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K{sub 2}Ga{sub 3} Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x} is nonstoichiometric and needs only a small amount of silver to form (x {approximately} 2--6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa{sub 3{minus}x}Au{sub x} system is also nonstoichiometric with a three-dimensional structure composed of Ga{sub 8} dodecahedra and four-bonded gallium atoms. Unlike Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x}, the RbGa{sub 3} binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary is discussed but the structure has not been completely

  3. Synthesis and Properties of Alkali Metal Intercalated Fullerene-like MS2 (M=W,Mo) Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zak, Alla; Feldman, Yishay; Lyakhovitskaya, Vera; Leitus, Gregory; Popovitz-Biro, Ronit; Wachtel, Ellen; Cohen, Hagai; Reich, Shimon; Tenne, Reshef

    2002-10-01

    Layered metal disulfides - MoS2 and WS2 in the form of fullerene-like (IF) nanoparticles and in the form of platelets (crystallites of the 2H polytype) have been intercalated by exposure to alkali metal (potassium and sodium) vapor using a two-zone transport method. The composition of the intercalated systems was established using X-ray energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). X-ray powder diffraction (XRD) analysis and transmission electron microscopy (TEM) of the samples, which were not exposed to the ambient atmosphere, showed that they suffered little change in their lattice parameters. On the other hand, after exposure to ambient atmosphere, substantial increase in the interplanar spacing (3-5 Å) was observed for the intercalated phases. Insertion of one to two water molecules per intercalated metal atom was suggested as a possible explanation for this large expansion along the c-axis. The modifications in magnetic and transport properties of the intercalated materials were investigated, and are believed to occur via charge transfer from the alkali metal to the conduction band of the host lattice. Restacking of the MS2 layers after prolonged exposure to the atmosphere and recovery of the pristine compound properties were observed as a result of deintercalation of the metal atoms.

  4. Silicon halide-alkali metal flames as a source of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Olson, D. B.; Miller, W. J.; Gould, R. K.

    1980-01-01

    The feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells was demonstrated. Low pressure experiments were performed demonstrating the production of free silicon and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents and relatively pure silicon was produced. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger scaled well stirred reactor was built. Experiments were performed to investigate the compatability of graphite based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

  5. 40 CFR 721.10097 - Disubstituted benzenesulfonic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES... metal salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as disubstituted benzenesulfonic acid, alkali metal salt (PMN...

  6. Modification of alkali metals on silicon-based nanoclusters: An enhanced nonlinear optical response

    NASA Astrophysics Data System (ADS)

    Li, Xiaojun; Han, Quan; Yang, Xiaohui; Song, Ruijuan; Song, Limei

    2016-08-01

    Structures, chemical stabilities and nonlinear optical properties of alkali metals-adsorbed niobium-doped silicon (M@SinNb+) clusters are investigated using the DFT methods. The alkali metals prefer energetically to be attached as bridged bond rather than M-Si single bond in most of optimized structures. Adsorption of alkali metals on doped silicon clusters gradually enhances their chemical stabilities with increasing cluster size. Noteworthily, the first hyperpolarizabilities (βtot) of the M@SinNb+ clusters, obtained by using the long-range corrected CAM-B3LYP functional, are large enough to establish their strong nonlinear optical behavior, especially for M@Si9Nb+ (M = Li, Na, and K), and the enhanced βtot ordering by alkali metals is Na > K > Li.

  7. Is Electronegativity a Useful Descriptor for the "Pseudo-Alkali-Metal" NH4?

    SciTech Connect

    Whiteside, Alexander; Xantheas, Sotiris S.; Gutowski, Maciej S.

    2011-11-18

    Molecular ions in the form of "pseudo-atoms" are common structural motifs in chemistry, with properties that are transferrable between different compounds. We have determined the electronegativity of the "pseudo-alkali metal" ammonium (NH4) and evaluated its reliability as a descriptor in comparison to the electronegativities of the alkali metals. The computed properties of its binary complexes with astatine and of selected borohydrides confirm the similarity of NH4 to the alkali metal atoms, although the electronegativity of NH4 is relatively large in comparison to its cationic radius. We paid particular attention to the molecular properties of ammonium (angular anisotropy, geometric relaxation, and reactivity), which can cause deviations from the behaviour expected of a conceptual "true alkali metal" with this electronegativity. These deviations allow for the discrimination of effects associated with the polyatomic nature of NH4.

  8. Is electronegativity a useful descriptor for the pseudo-alkali metal NH4?

    PubMed

    Whiteside, Alexander; Xantheas, Sotiris S; Gutowski, Maciej

    2011-11-18

    Molecular ions in the form of "pseudo-atoms" are common structural motifs in chemistry, with properties that are transferrable between different compounds. We have determined one such property--the electronegativity--for the "pseudo-alkali metal" ammonium (NH(4)), and evaluated its reliability as a descriptor versus the electronegativities of the alkali metals. The computed properties of ammonium's binary complexes with astatine and of selected borohydrides confirm the similarity of NH(4) to the alkali metal atoms, although the electronegativity of NH(4) is relatively large in comparison to its cationic radius. We have paid particular attention to the molecular properties of ammonium (angular anisotropy, geometric relaxation and reactivity), which can cause deviations from the behaviour expected of a conceptual "true alkali metal" with this electronegativity. These deviations allow for the discrimination of effects associated with the molecular nature of NH(4). PMID:21928287

  9. Method and composition for testing for the presence of an alkali metal

    DOEpatents

    Guon, Jerold

    1981-01-01

    A method and composition for detecting the presence of an alkali metal on the surface of a body such as a metal plate, tank, pipe or the like is provided. The method comprises contacting the surface with a thin film of a liquid composition comprising a light-colored pigment, an acid-base indicator, and a nonionic wetting agent dispersed in a liquid carrier comprising a minor amount of water and a major amount of an organic solvent selected from the group consisting of the lower aliphatic alcohols, ketones and ethers. Any alkali metal present on the surface in elemental form or as an alkali metal hydroxide or alkali metal carbonate will react with the acid-base indicator to produce a contrasting color change in the thin film, which is readily discernible by visual observation or automatic techniques.

  10. Highly polar bonds and the meaning of covalency and ionicity--structure and bonding of alkali metal hydride oligomers.

    PubMed

    Bickelhaupt, F Matthias; Solà, Miquel; Guerra, Célia Fonseca

    2007-01-01

    The hydrogen-alkali metal bond is simple and archetypal, and thus an ideal model for studying the nature of highly polar element-metal bonds. Thus, we have theoretically explored the alkali metal hydride monomers, HM, and (distorted) cubic tetramers, (HM)4, with M = Li, Na, K, and Rb, using density functional theory (DFT) at the BP86/TZ2P level. Our objective is to determine how the structure and thermochemistry (e.g., H-M bond lengths and strengths, oligomerization energies, etc.) of alkali metal hydrides depend on the metal atom, and to understand the emerging trends in terms of quantitative Kohn-Sham molecular orbital (KS-MO) theory. The H-M bond becomes longer and weaker, both in the monomers and tetramers, if one descends the periodic table from Li to Rb. Quantitative bonding analyses show that this trend is not determined by decreasing electrostatic attraction but, primarily, by the weakening in orbital interactions. The latter become less stabilizing along Li-Rb because the bond overlap between the singly occupied molecular orbitals (SOMOs) of H* and M* radicals decreases as the metal ns atomic orbital (AO) becomes larger and more diffuse. Thus, the H-M bond behaves as a text-book electron-pair bond and, in that respect, it is covalent, despite a high polarity. For the lithium and sodium hydride tetramers, the H4 tetrahedron is larger than and surrounds the M4 cluster (i.e., H-H > M-M). Interestingly, this is no longer the case in the potassium and rubidium hydride tetramers, in which the H4 tetrahedron is smaller than and inside the M4 cluster (i.e., H-H < M-M). PMID:17328442

  11. In situ formation of coal gasification catalysts from low cost alkali metal salts

    DOEpatents

    Wood, Bernard J.; Brittain, Robert D.; Sancier, Kenneth M.

    1985-01-01

    A carbonaceous material, such as crushed coal, is admixed or impregnated with an inexpensive alkali metal compound, such as sodium chloride, and then pretreated with a stream containing steam at a temperature of 350.degree. to 650.degree. C. to enhance the catalytic activity of the mixture in a subsequent gasification of the mixture. The treatment may result in the transformation of the alkali metal compound into another, more catalytically active, form.

  12. Identifying alkali metal inhibitors of crystal growth: a selection criterion based on ion pair hydration energy.

    PubMed

    Farmanesh, Sahar; Alamani, Bryan G; Rimer, Jeffrey D

    2015-09-21

    We show that alkali metals function as effective modifiers of calcium oxalate monohydrate (COM) crystallization wherein alkali-oxalate ion parings reduce the rate of crystal growth by as much as 60%. Our findings reveal a distinct trend in alkali metal efficacy that cannot be explained by colloidal theories or simple descriptors, such as ion size, but is consistent with a theoretical model that accounts for the ion pair's affinity for water. PMID:26242310

  13. The effect of different alkali metal hydroxides on nickel electrode life

    NASA Technical Reports Server (NTRS)

    Lim, H. S.; Verzwyvelt, S. A.; Clement, S. K.

    1988-01-01

    An accelerated cycle-life test (100-percent depth of discharge) of a sintered-type Ni electrode has been carried out in a flooded cell containing different alkali metal hydroxide electrolytes such as LiOH, NaOH, KOH, RbOH, and CsOH. Decrease in Ni electrode capacity with cycling was reduced as the radius of the alkali metal ions, with possible exception of CsOH.

  14. Stability of alkali-metal hydrides: effects of n-type doping

    NASA Astrophysics Data System (ADS)

    Olea Amezcua, Monica Araceli; de La Peña Seaman, Omar; Rivas Silva, Juan Francisco; Heid, Rolf; Bohnen, Klaus-Peter

    Metal hydrides could be considered ideal solid-state hydrogen storage systems, they have light weight and high hydrogen volumetric densities, but the hydrogen desorption process requires excessively high temperatures due to their high stability. Efforts have been performed to improve their dehydrogenation properties, based on the introduction of defects, impurities and doping. We present a systematic study of the n-type (electronic) doping effects on the stability of two alkali-metal hydrides: Na1-xMgxH and Li1-xBexH. These systems have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the self-consistent version of the virtual crystal approximation to model the doping. The full-phonon dispersions are analyzed for several doping content, paying special attention to the crystal stability. It is found a doping content threshold for each system, where they are close to dynamical instabilities, which are related to charge redistribution in interstitial zones. Applying the quasiharmonic approximation, the vibrational free energy, the linear thermal expansion and heat capacities are obtained for both hydrides systems and are analyzed as a function of the doping content. This work is partially supported by the VIEP-BUAP 2016 and CONACYT-México (No.221807) projects.

  15. Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect

    NASA Astrophysics Data System (ADS)

    Samsonowicz, M.; Regulska, E.; Lewandowski, W.

    2011-11-01

    The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions [1]. The vibrational FT-IR (in KBr and ATR techniques) and 1H and 13C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg → Ba were compared with series of univalent metal Li → Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.

  16. Effect of sorbed molecules on the resistivity of alkali metal-graphite intercalation compounds

    SciTech Connect

    Akuzawa, Noboru Kunihashi, Yoji; Sato, Yuki; Tsuchiya, Ken-ichi; Matsumoto, Rika

    2007-03-15

    Alkali metal-graphite intercalation compounds with the composition of MC{sub 24} (M=K, Rb, Cs) were prepared by heating a mixture of MC{sub 8} (saturated compound) and graphite sheet (Grafoil) at 350-450 deg. C. The resistivity perpendicular to the layer planes ({rho} {sub c}) of the resulting compounds was determined by the two-terminal method. The anisotropy factor of the resistivity, ({rho} {sub c}/{rho} {sub a}), of KC{sub 24} prepared from Grafoil was {approx}130, being about 1/6-1/10 in magnitude compared with that of KC{sub 24} prepared from highly oriented pyrolytic graphite. The resistivity change during sorption of hydrogen (at 90 K), ethylene (at 194 K) and acetylene (at 194 K) was determined. The resistivity of MC{sub 24} increased with increase of the sorbed amount of H{sub 2}. The magnitude of the increase was in the order KC{sub 24}>RbC{sub 24}>CsC{sub 24}. This resistivity increase was considered to be due to the expansion along c-direction which reduces the charge-transfer interaction between the carbon layers and potassium ions, resulting in the decrease of the density of the conduction electron. The resistivity of MC{sub 24} increased extensively during sorption of C{sub 2}H{sub 4} and C{sub 2}H{sub 2}. It was discussed in connection with the in-plane structural transition and chemical interaction between alkali metal ions and sorbed molecules. - Graphical abstract: The resistivity of MC{sub 24} increased with increase of the sorbed amount of H{sub 2}. The magnitude of the increase was in the order KC{sub 24}>RbC{sub 24}>CsC{sub 24}. This resistivity increase was considered to be due to the expansion along c-direction which reduces the charge-transfer interaction between the carbon layers and potassium ions.

  17. Charge oscillations and structure for alkali-metal-doped polyacetylene

    NASA Astrophysics Data System (ADS)

    Baughman, R. H.; Murthy, N. S.; Eckhardt, H.; Kertesz, M.

    1992-11-01

    predictions for oligomers, and good agreement is obtained between calculated and observed x-ray photoelectron spectra for sodium-doped polyacetylene. Emphasis is placed on the results of crystallographic studies of alkali-metal-doped polyacetylene and on the relationship between the experimentally derived symmetry breaking in interchain packing and the molecular symmetry breaking predicted by theory. Since presently available experimental data are insufficient for complete determination of structure, the present theoretical results can be useful for refinements in the interpretation of these data, as well as for refined crystal-packing calculations.

  18. Optical stabilization of Rb vapor density above thermal equilibrium

    NASA Astrophysics Data System (ADS)

    Burchianti, A.; Bogi, A.; Marinelli, C.; Mariotti, E.; Moi, L.

    2010-08-01

    We stabilize the Rb vapor density above its thermal equilibrium value in sealed glass cells, which are generally used in atomic physics experiments. The method relies on light-induced desorption of Rb atoms from dielectric surfaces. The process does not demand high light intensities so that LEDs or laser diodes can be used as desorbing sources. The experiments are carried out in Pyrex cells either coated with a polydimethylsiloxane film or containing a porous glass sample. Under illumination both the organic coating and the porous sample release a large amount of Rb atoms into the cell volume. We show that the Rb vapor density can be maintained to a preset value, using a desorbing light intensity controlled by a feedback signal given by the Rb absorption or fluorescence level. Moreover, we find that the stabilization technique does not depend on the microscopic mechanisms underlying photodesorption.

  19. Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism

    PubMed Central

    Boughlala, Zakaria; Fonseca Guerra, Célia

    2016-01-01

    Abstract We have analyzed the structure and bonding of gas‐phase Cl−X and [HCl−X]+ complexes for X+= H+, CH3 +, Li+, and Na+, using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl− and HCl for the various cations. The Cl−X bond becomes longer and weaker along X+ = H+, CH3 +, Li+, and Na+. Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn–Sham molecular orbital (KS‐MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities. PMID:27551660

  20. Stable Alkali-Metal Complexes of Hybrid Disila-Crown Ethers.

    PubMed

    Reuter, Kirsten; Buchner, Magnus R; Thiele, Günther; von Hänisch, Carsten

    2016-05-01

    The complexation ability of hybrid disilane and ethylene containing crown ether ring systems was analyzed using 1,2-disila[12]crown-4 (1), 1,2-disila[15]crown-5 (2), 1,2-disila[18]crown-6 (3), and 1,2,7,8-tetrasila[12]crown-4 (7). Alkali-metal complexes (Li(+), Na(+), K(+)) were obtained and analyzed via X-ray diffraction. The complex stability of [Li(1,2-disila[12]crown-4)](+) and [Li(1,2,7,8-tetrasila[12]crown-4)](+) was determined, in relation to the lithium complex of [12]crown-4, by density functional theory (DFT) calculations employing the BP86/def2-TZVP level of theory. In solution, the exchange of lithium cations between pure [12]crown-4 and hybrid [12]crown-4 is on even terms, as has been shown from the relative binding affinity of compounds 1 and 7 by means of dynamic proton nuclear magnetic resonance (NMR) spectroscopy. PMID:27082743

  1. Electrical Transport Properties of C60 Single Crystals Doped with Alkali Metals

    NASA Astrophysics Data System (ADS)

    Ogata, Hironori; Maruyama, Yusei; Inabe, Tamotsu; Achiba, Yohji; Suzuki, Sinzo; Kikuchi, Koichi; Ikemoto, Isao

    Electronic structures of various kinds of alkali metal (Na, K, Rb or Cs)-doped C60 solids are studied by electrical resistivity and thermoelectric power measurements by using C60 single crystals prepared from a CS2 solution as a starting material. For K-or Rb-doped C60, metallic conducting behaviors in the normal conducting state and relatively sharp superconducting transitions are observed by the electrical resistivity measurements. Nearly linear-temperature dependences with the negative sign are observed in the thermoelectric power measurements at the normal conducting states for K-or Rb-doped C60. From electron diffusion term of the thermoelectric power, the values of Fermi energy and the density of states at the Fermi energy are estimated by assuming the three-dimensional free electron model, which are in substantial agreement with the results of other experiments and calculations. "Metal-semiconductor transition" is observed in both the electrical resistivity and the thermoelectric power measurements for Na-doped C60. Existence of metallic phase is confirmed by the thermoelectric power measurement in Cs-doped C60.

  2. Alkali Metal Cation versus Proton and Methyl Cation Affinities: Structure and Bonding Mechanism.

    PubMed

    Boughlala, Zakaria; Fonseca Guerra, Célia; Bickelhaupt, F Matthias

    2016-06-01

    We have analyzed the structure and bonding of gas-phase Cl-X and [HCl-X](+) complexes for X(+)= H(+), CH3 (+), Li(+), and Na(+), using relativistic density functional theory (DFT). We wish to establish a quantitative trend in affinities of the anionic and neutral Lewis bases Cl(-) and HCl for the various cations. The Cl-X bond becomes longer and weaker along X(+) = H(+), CH3 (+), Li(+), and Na(+). Our main purpose is to understand the heterolytic bonding mechanism behind the intrinsic (i.e., in the absence of solvent) alkali metal cation affinities (AMCA) and how this compares with and differs from those of the proton affinity (PA) and methyl cation affinity (MCA). Our analyses are based on Kohn-Sham molecular orbital (KS-MO) theory in combination with a quantitative energy decomposition analysis (EDA) that pinpoints the importance of the different features in the bonding mechanism. Orbital overlap appears to play an important role in determining the trend in cation affinities. PMID:27551660

  3. Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

    DOEpatents

    Tsang, Floris Y.

    1980-01-01

    Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

  4. Dissolution Process of Palladium in Hydrochloric Acid: A Route via Alkali Metal Palladates

    NASA Astrophysics Data System (ADS)

    Kasuya, Ryo; Miki, Takeshi; Morikawa, Hisashi; Tai, Yutaka

    2015-12-01

    To improve the safety of the Pd recovery processes that use toxic oxidizers, dissolution of Pd in hydrochloric acid with alkali metal palladates was investigated. Alkali metal palladates were prepared by calcining a mixture of Pd black and alkali metal (Li, Na, and K) carbonates in air. Almost the entire amount of Pd was converted into Li2PdO2 after calcination at 1073 K (800 °C) using Li2CO3. In contrast, PdO was obtained by calcination at 1073 K (800 °C) using Na and K carbonates. Our results indicated that Li2CO3 is the most active reagent among the examined alkali metal carbonates for the formation of palladates. In addition, dissolution of the resulting Li2PdO2 in HCl solutions was evaluated under various conditions. In particular, Li2PdO2 rapidly dissolved in diluted (0.1 M) HCl at ambient temperature. Solubility of Pd of Li2PdO2 was found to be 99 pct or larger after dissolution treatment at 353 K (80 °C) for 5 minutes; in contrast, PdO hardly dissolved in 0.1 M HCl. The dissolution mechanism of Li2PdO2 in HCl was also elucidated by analysis of crystal structures and particulate properties. Since our process is completely free from toxic oxidizers, the dissolution process via alkali metal palladates is much safer than currently employed methods.

  5. Raman spectroscopic investigation of alkali-metal hexachloro compounds of refractory metals

    SciTech Connect

    Kipouros, G.J.; Flint, J.H.; Sadoway, D.R.

    1985-11-06

    The Raman spectra of molten alkali-metal hexachlorozirconate, hexachlorohafnate, hexachloroniobate, and hexachlorotantalate compounds have been obtained in the temperature range 623-1143 K. The results confirm that the refractory metal exists in the form of an octahedrally coordinated complex anion that is stable even in the molten state. For a given refractory metal the frequency of the nu/sub 1/ line increases as the size of the alkali-metal cation decreases. For a given alkali metal the frequency of the nu/sub 1/ line increases as the valence of the refractory metal increases. This last observation may serve as the basis for detecting, by Raman spectroscopy, aliovalent species that may form during the electrolysis of melts containing refractory-metal chlorides. 22 references, 4 figures, 2 tables.

  6. Development of operationally stable inverted organic light-emitting diode prepared without using alkali metals (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Fukagawa, Hirohiko; Morii, Katsuyuki; Hasegawa, Munehiro; Gouda, Shun; Tsuzuki, Toshimitsu; Shimizu, Takahisa; Yamamoto, Toshihiro

    2015-10-01

    The OLED is one of the key devices for realizing future flexible displays and lightings. One of the biggest challenges left for the OLED fabricated on a flexible substrate is the improvement of its resistance to oxygen and moisture. A high barrier layer [a water vapor transmission rate (WVTR) of about 10-6 g/m2/day] is proposed to be necessary for the encapsulation of conventional OLEDs. Some flexible high barrier layers have recently been demonstrated; however, such high barrier layers require a complex process, which makes flexible OLEDs expensive. If an OLED is prepared without using air-sensitive materials such as alkali metals, no stringent encapsulation is necessary for such an OLED. In this presentation, we will discuss our continuing efforts to develop an inverted OLED (iOLED) prepared without using alkali metals. iOLEDs with a bottom cathode are considered to be effective for realizing air-stable OLEDs since the electron injection layer (EIL) can be prepared by fabrication processes that might damage the organic layers, resulting in the enhanced range of materials suitable for EILs. We have demonstrated that a highly efficient and relatively air-stable iOLED can be realized by employing poly(ethyleneimine) as an EIL. Dark spot formation was not observed after 250 days in the poly(ethyleneimine)-based iOLED encapsulated by a barrier film with a WVTR of 10-4 g/m2/day. In addition, we have demonstrated the fabrication of a highly operational stable iOLED utilizing a newly developed EIL. The iOLED exhibits an expected half-lifetime of over 10,000 h from an initial luminance of 1,000 cd/m2.

  7. On-sun test results from second-generation and advanced-concepts alkali-metal pool-boiler receivers

    SciTech Connect

    Moreno, J.B.; Andraka, C.E.; Moss, T.A.; Cordeiro, P.G.; Dudley, V.E.; Rawlinson, K.S.

    1994-05-01

    Two 75-kW{sub t} alkali-metal pool-boiler solar receivers have been successfully tested at Sandia National Laboratories` National Solar Thermal Test Facility. The first one, Sandia`s `` second-generation pool-boiler receiver,`` was designed to address commercialization issues identified during post-test assessment of Sandia`s first-generation pool-boiler receiver. It was constructed from Haynes alloy 230 and contained the alkali-metal alloy NaK-78. The absorber`s wetted side had a brazed-on powder-metal coating to stabilize boiling. This receiver was evaluated for boiling stability, hot- and warm-restart behavior, and thermal efficiency. Boiling was stable under all conditions. All of the hot restarts were successful. Mild transient hot spots observed during some hot restarts were eliminated by the addition of 1/3 torr of xenon to the vapor space. All of the warm restarts were also successful. The heat-transfer crisis that damaged the first receiver did not recur. Thermal efficiency was 92.3% at 750{degrees}C with 69.6 kW{sub t} solar input. The second receiver tested, Sandia`s ``advanced-concepts receiver,`` was a replica of the first-generation receiver except that the cavities, which were electric-discharge-machined in the absorber for boiling stability, were eliminated. This step was motivated by bench-scale test results that showed that boiling stability improved with increased heated-surface area, tilt of the heated surface from vertical, and added xenon. The bench-scale results suggested that stable boiling might be possible without heated-surface modification in a 75-kW{sub t} receiver. Boiling in the advanced-concepts receiver with 1/3 torr of xenon added has been stable under all conditions, confirming the bench-scale tests.

  8. Rock Degradation by Alkali Metals: A Possible Lunar Erosion Mechanism.

    PubMed

    Naughton, J J; Barnes, I L; Hammond, D A

    1965-08-01

    When rocks melt under ultrahigh-vacuum conditions, their alkali components volatilize as metals. These metal vapors act to comminute polycrystalline rocks to their component minerals. The resultant powder is porous and loosely packed and its characteristics may be compatible with the lunar surface as revealed by the Ranger photographs. If meteorite impact or lunar volcanism has produced vaporization or areas of molten lava, alkali erosion may have given dust of this character in adjacent solid areas. PMID:17747570

  9. Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes.

    PubMed

    Uzelac, Marina; Borilovic, Ivana; Amores, Marco; Cadenbach, Thomas; Kennedy, Alan R; Aromí, Guillem; Hevia, Eva

    2016-03-24

    By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways. PMID:26916525

  10. Hydrogen generation using silicon nanoparticles and their mixtures with alkali metal hydrides

    NASA Astrophysics Data System (ADS)

    Patki, Gauri Dilip

    mole of Si. We compare our silicon nanoparticles (˜10nm diameter) with commercial silicon nanopowder (<100nm diameter) and ball-milled silicon powder (325 mesh). The increase in rate upon decreasing the particle size to 10 nm was even greater than would be expected based upon the increase in surface area. While specific surface area increased by a factor of 6 in going from <100 nm to ˜10 nm particles, the hydrogen production rate increased by a factor of 150. However, in all cases, silicon requires a base (e.g. NaOH, KOH, hydrazine) to catalyze its reaction with water. Metal hydrides are also promising hydrogen storage materials. The optimum metal hydride would possess high hydrogen storage density at moderate temperature and pressure, release hydrogen safely and controllably, and be stable in air. Alkali metal hydrides have high hydrogen storage density, but exhibit high uncontrollable reactivity with water. In an attempt to control this explosive nature while maintaining high storage capacity, we mixed our silicon nanoparticles with the hydrides. This has dual benefits: (1) the hydride- water reaction produces the alkali hydroxide needed for base-catalyzed silicon oxidation, and (2) dilution with 10nm coating by, the silicon may temper the reactivity of the hydride, making the process more controllable. Initially, we analyzed hydrolysis of pure alkali metal hydrides and alkaline earth metal hydrides. Lithium hydride has particularly high hydrogen gravimetric density, along with faster reaction kinetics than sodium hydride or magnesium hydride. On analysis of hydrogen production we found higher hydrogen yield from the silicon nanoparticle—metal hydride mixture than from pure hydride hydrolysis. The silicon-hydride mixtures using our 10nm silicon nanoparticles produced high hydrogen yield, exceeding the theoretical yield. Some evidence of slowing of the hydride reaction rate upon addition of silicon nanoparticles was observed.

  11. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    SciTech Connect

    Liu, X. H.; Luo, H.; Qu, T. L. Yang, K. Y.; Ding, Z. C.

    2015-10-15

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  12. Oxygen production by molten alkali metal salts using multiple absorption-desorption cycles

    DOEpatents

    Cassano, A.A.

    1985-07-02

    A continuous chemical air separation is performed wherein oxygen is recovered with a molten alkali metal salt oxygen acceptor in a series of absorption zones which are connected to a plurality of desorption zones operated in separate parallel cycles with the absorption zones. A greater recovery of high pressure oxygen is achieved at reduced power requirements and capital costs. 3 figs.

  13. Oxygen production by molten alkali metal salts using multiple absorption-desorption cycles

    DOEpatents

    Cassano, Anthony A.

    1985-01-01

    A continuous chemical air separation is performed wherein oxygen is recovered with a molten alkali metal salt oxygen acceptor in a series of absorption zones which are connected to a plurality of desorption zones operated in separate parallel cycles with the absorption zones. A greater recovery of high pressure oxygen is achieved at reduced power requirements and capital costs.

  14. Unidirectional thermal expansion in KZnB3O6: role of alkali metals.

    PubMed

    Lou, Yanfang; Li, Dandan; Li, Zhilin; Zhang, Han; Jin, Shifeng; Chen, Xiaolong

    2015-12-14

    The driving force of the unidirectional thermal expansion in KZnB3O6 has been studied experimentally and theoretically. Our results show that the low-energy vibrational modes of alkali metals play a crucial role in this unusual thermal behavior. PMID:26515521

  15. Method for inhibiting alkali metal corrosion of nickel-containing alloys

    DOEpatents

    DeVan, Jackson H.; Selle, James E.

    1983-01-01

    Structural components of nickel-containing alloys within molten alkali metal systems are protected against corrosion during the course of service by dissolving therein sufficient aluminum, silicon, or manganese to cause the formation and maintenance of a corrosion-resistant intermetallic reaction layer created by the interaction of the molten metal, selected metal, and alloy.

  16. Enhancing electrocatalytic hydrogen evolution by nickel salicylaldimine complexes with alkali metal cations in aqueous media.

    PubMed

    Shao, Haiyan; Muduli, Subas K; Tran, Phong D; Soo, Han Sen

    2016-02-18

    New salicylaldimine nickel complexes, comprising only earth-abundant elements, have been developed for electrocatalytic hydrogen evolution in aqueous media. The second-sphere ether functionalities on the periphery of the complexes enhance the electrocatalytic activity in the presence of alkali metal cations. The electrocatalysts demonstrate improved performances especially in the economical and sustainable seawater reaction medium. PMID:26779580

  17. Characterization of lanthanide(III) DOTP complexes: Thermodynamics, protonation, and coordination to alkali metal ions

    SciTech Connect

    Sherry, A.D.; Ren, J.; Huskens, J.

    1996-07-31

    The chemical and thermodynamic characterization of Lanthanide(III) DOTP complexes was performed. Spectrophotometry, potentiometry, osmometry, and NMR spectroscopy were used in this characterization. Stability constants, protonation equilibria, and interactions of the complexes with alkali metal ions were measured and summarized.

  18. 40 CFR 721.5985 - Fatty alkyl phosphate, alkali metal salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.5985 Fatty alkyl phosphate, alkali metal salt (generic). (a) Chemical... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fatty alkyl phosphate, alkali...

  19. 40 CFR 721.10098 - Disubstituted benzoic acid, alkali metal salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... metal salt (generic). 721.10098 Section 721.10098 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10098 Disubstituted benzoic acid, alkali metal...

  20. 40 CFR 721.4663 - Fluorinated carboxylic acid alkali metal salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... metal salts. 721.4663 Section 721.4663 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.4663 Fluorinated carboxylic acid alkali metal salts. (a)...

  1. Affinity Capillary Electrophoresis Applied to Investigation of Valinomycin Complexes with Ammonium and Alkali Metal Ions.

    PubMed

    Štěpánová, Sille; Kašička, Václav

    2016-01-01

    This chapter deals with the application of affinity capillary electrophoresis (ACE) to investigation of noncovalent interactions (complexes) of valinomycin, a macrocyclic dodecadepsipeptide antibiotic ionophore, with ammonium and alkali metal ions (lithium, sodium, potassium, rubidium, and cesium). The strength of these interactions was characterized by the apparent binding (stability, association) constants (K b) of the above valinomycin complexes using the mobility shift assay mode of ACE. The study involved measurements of effective electrophoretic mobility of valinomycin at variable concentrations of ammonium or alkali metal ions in the background electrolyte (BGE). The effective electrophoretic mobilities of valinomycin measured at ambient temperature and variable ionic strength were first corrected to the reference temperature 25 °C and constant ionic strength (10 or 25 mM). Then, from the dependence of the corrected valinomycin effective mobility on the ammonium or alkali metal ion concentration in the BGE, the apparent binding constants of the valinomycin-ammonium or valinomycin-alkali metal ion complexes were determined using a nonlinear regression analysis. Logarithmic form of the binding constants (log K b) were found to be in the range of 1.50-4.63, decreasing in the order Rb(+) > K(+) > Cs(+) > > Na(+) > NH4 (+) ~ Li(+). PMID:27473493

  2. The interactions of sorbates with gallosilicates and alkali-metal exchanged gallosilicates

    NASA Astrophysics Data System (ADS)

    Limtrakul, J.; Kuno, M.; Treesukol, P.

    1999-11-01

    Structures, energetics and vibrational frequencies of the interaction of adsorbates with H-aluminosilicates (H-AlZ), H-gallosilicates (H-GaZ), alkali-metal exchanged aluminosilicates (X-AlZ) and alkali-metal exchanged gallosilicates (X-GaZ), where X being Li, Na, or K, have been carried out at B3LYP and HF levels of theory with 6-31G(d) as the basis set. The charge compensating alkali-metal ions can affect the catalytically active site (Si-O-T where T=Al or Ga) by weakening the Si-O, Al-O, and Ga-O bonds as compared to their anionic frameworks. Comparing the net stabilization energies, Δ ENSE, of the naked alkali-metal/H 2O adducts with those of the alkali-metal exchanged zeolite/H 2O systems, the latter amounts only to about 50% of the former, which is partly due to the destabilizing role of the negative zeolitic oxygen frameworks surrounding the cations. The interaction of sorbates with the alkali-metal exchanged gallosilicates can be employed to probe the field strength inside the catalytic frameworks as indicated by the plot of the binding energy, Δ E, versus 1/ RX-O w2, with R(X-O w) being the distance between the cationic nucleus and the oxygen atom of the adsorbate. The IR spectra of H 2O adsorbed on Na-AlZ are calculated to be 3584, 3651, and 1686 cm -1. The obtained results are in excellent agreement with the very recent experimental IR spectra of water adsorbed on Na-ZSM-5 of Zecchina et al. (J. Phys. Chem., 100 (1996) 16 484). Other important features, i.e. the correlation between Δ νOH and, Δ E, R(X-O w) , and 1/ RX-O w2, cationic size, demonstrate that the interactions of sorbates with alkali-metal exchanged gallosilicates are well approximated by electrostatic contribution.

  3. Study on the Characteristics of an Alkali-Metal Thermoelectric Power Generation System

    NASA Astrophysics Data System (ADS)

    Lee, Wook-Hyun; Hwang, Hyun-Chang; Lee, Ji-Su; Kim, Pan-Jo; Lim, Sang-Hyuk; Rhi, Seok-Ho; Lee, Kye-Bock; Lee, Ki-Woo

    2015-10-01

    In the present study, a numerical simulation and experimental studies of an alkali-metal thermoelectric energy converter (AMTEC) system were carried out. The present, unique AMTEC model consists of an evaporator, a β-alumina solid electrolyte (BASE) tube, a condenser, and an artery cable wick. The key points for operation of the present AMTEC were 1100 K in the evaporator and 600 K in the condenser. A numerical model based on sodium-saturated porous wicks was developed and shown to be able to simulate the AMTEC system. The simulation results show that the AMTEC system can generate up to 100 W with a given design. The AMTEC system developed in the present work and used in the practical investigations could generate an electromotive force of 7 V. Artery wick and evaporator wick structures were simulated for the optimum design. Both sodium-saturated wicks were affected by numerous variables, such as the input heat power, cooling temperature, sodium mass flow rate, and capillary-driven fluid flow. Based on an effective thermal conductivity model, the presented simulation could successfully predict the system performance. Based on the numerical simulation, the AMTEC system operates with efficiency near 10% to 15%. In the case of an improved BASE design, the system could reach efficiency of over 30%. The system was designed for 0.6 V power, 25 A current, and 100 W power input. In addition, in this study, the temperature effects in each part of the AMTEC system were analyzed using a heat transfer model in porous media to apply to the computational fluid dynamics at a predetermined temperature condition for the design of a 100-W AMTEC prototype. It was found that a current density of 0.5 A/cm2 to 0.9 A/cm2 for the BASE is suitable when the temperatures of the evaporator section and condenser section are 1100 K and 600 K, respectively.

  4. Elucidation of transport mechanism and enhanced alkali ion transference numbers in mixed alkali metal-organic ionic molten salts.

    PubMed

    Chen, Fangfang; Forsyth, Maria

    2016-07-28

    Mixed salts of Ionic Liquids (ILs) and alkali metal salts, developed as electrolytes for lithium and sodium batteries, have shown a remarkable ability to facilitate high rate capability for lithium and sodium electrochemical cycling. It has been suggested that this may be due to a high alkali metal ion transference number at concentrations approaching 50 mol% Li(+) or Na(+), relative to lower concentrations. Computational investigations for two IL systems illustrate the formation of extended alkali-anion aggregates as the alkali metal ion concentration increases. This tends to favor the diffusion of alkali metal ions compared with other ionic species in electrolyte solutions; behavior that has recently been reported for Li(+) in a phosphonium ionic liquid, thus an increasing alkali transference number. The mechanism of alkali metal ion diffusion via this extended coordination environment present at high concentrations is explained and compared to the dynamics at lower concentrations. Heterogeneous alkali metal ion dynamics are also evident and, somewhat counter-intuitively, it appears that the faster ions are those that are generally found clustered with the anions. Furthermore these fast alkali metal ions appear to correlate with fastest ionic liquid solvent ions. PMID:27375042

  5. Adsorption of Ar on planar surfaces studied with a density functional theory.

    PubMed

    Sartarelli, Salvador A; Szybisz, Leszek

    2009-11-01

    The adsorption of Ar on planar structureless substrates of alkali metals, alkaline-earth metal Mg, CO2 , and Au was analyzed by applying a density functional formalism which includes a recently proposed effective attractive pair potential conditioned to Ar. It is shown that this approach reproduces the experimental surface tension of the liquid-vapor interface over the entire bulk coexistence curve for temperatures T spanning from the triple point Tt up to the critical point Tc. The wetting properties were studied over the entire range temperatures Tt<-->Tc. It was found that Ar wets all the investigated surfaces. The adsorption isotherms for alkali metals exhibit first-order phase transitions. Prewetting lines were resolved even for the less attractive surfaces. In the cases of Mg, CO2 , and Au a continuous growth for T> or =Tt was obtained. A comparison with experimental data and other microscopic calculations is reported. PMID:20365027

  6. FP-APW+lo calculations of the electronic and optical properties of alkali metal sulfides under pressure.

    PubMed

    Khachai, H; Khenata, R; Bouhemadou, A; Haddou, A; Reshak, Ali H; Amrani, B; Rached, D; Soudini, B

    2009-03-01

    The electronic and optical properties of M(2)S (M = Li, Na, K and Rb) compounds in the cubic antifluorite structure have been calculated, using a full relativistic version of the full-potential augmented plane-wave plus local orbitals method based on density functional theory, within both the local density approximation (LDA) and the generalized gradient approximation (GGA). Moreover, the Engel-Vosko GGA formalism (EV-GGA) is applied so as to optimize the corresponding potential for band structure calculations. The calculated equilibrium lattices and bulk moduli are in good agreement with the available data. Band structure, density of states, electron charge density and pressure coefficients of energy gaps are given. Results obtained for band structure using EV-GGA are larger than those with LDA and GGA. It is found that the spin-orbit coupling lifts the triple degeneracy at the Γ point and the double degeneracy at the X point. The analysis of the electron charge density shows that the M-S bonds have a significant ionic character. The complex dielectric functions ε(2)(ω) for alkali metal sulfides were calculated for radiation up to 30 eV and the assignment of the critical points to the band structure energy differences at various points of the Brillouin zone was made. The pressure and volume dependence of the static dielectric constant and the refractive index are calculated. PMID:21817390

  7. An optically trapped mixture of alkali-metal and metastable helium atoms

    NASA Astrophysics Data System (ADS)

    Flores, Adonis; Mishra, Hari Prasad; Vassen, Wim; Knoop, Steven

    2016-05-01

    Ultracold collisions between alkali-metal and metastable triplet helium (He*) atoms provide the opportunity to study Feshbach resonances in the presence of a strong loss channel, namely Penning ionization, which strongly depends on the internal spin-states of the atoms. Recently we have realized the first optically trapped alkali-metal-metastable helium mixture. To prepare the ultracold 87 Rb+4 He* mixture in a single beam optical dipole trap (ODT), we apply evaporative cooling in a strong quadrupole magnetic trap (QMT) for both species and subsequent transfer to the ODT via a hybrid trap. We will present lifetime measurements of different spin-state mixtures, testing the application of the universal loss model to this interesting multichannel collision system.

  8. Alkali-Metal-Ion-Assisted Hydrogen Atom Transfer in the Homocysteine Radical.

    PubMed

    Lesslie, Michael; Lau, Justin Kai-Chi; Lawler, John T; Siu, K W Michael; Oomens, Jos; Berden, Giel; Hopkinson, Alan C; Ryzhov, Victor

    2016-02-12

    Intramolecular hydrogen atom transfer (HAT) was examined in homocysteine (Hcy) thiyl radical/alkali metal ion complexes in the gas phase by combination of experimental techniques (ion-molecule reactions and infrared multiple photon dissociation spectroscopy) and theoretical calculations. The experimental results unequivocally show that metal ion complexation (as opposed to protonation) of the regiospecifically generated Hcy thiyl radical promotes its rapid isomerisation into an α-carbon radical via HAT. Theoretical calculations were employed to calculate the most probable HAT pathway and found that in alkali metal ion complexes the activation barrier is significantly lower, in full agreement with the experimental data. This is, to our knowledge, the first example of a gas-phase thiyl radical thermal rearrangement into an α-carbon species within the same amino acid residue and is consistent with the solution phase behaviour of Hcy radical. PMID:26836574

  9. 'Doubly Magic' Conditions in Magic-Wavelength Trapping of Ultracold Alkali-Metal Atoms

    SciTech Connect

    Derevianko, Andrei

    2010-07-16

    In experiments with trapped atoms, atomic energy levels are shifted by the trapping optical and magnetic fields. Regardless of this strong perturbation, precision spectroscopy may be still carried out using specially crafted, 'magic' trapping fields. Finding these conditions for particularly valuable microwave transitions in alkali-metal atoms has so far remained an open challenge. Here I demonstrate that the microwave transitions in alkali-metal atoms may be indeed made impervious to both trapping laser intensity and fluctuations of magnetic fields. I consider driving multiphoton transitions between the clock levels and show that these 'doubly magic' conditions are realized at special values of trapping laser wavelengths and fixed values of relatively weak magnetic fields. This finding has implications for precision measurements and quantum information processing with qubits stored in hyperfine manifolds.

  10. Reactions between cold methyl halide molecules and alkali-metal atoms

    SciTech Connect

    Lutz, Jesse J.; Hutson, Jeremy M.

    2014-01-07

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH{sub 3}X (X = F, Cl, Br, I) and alkali-metal atoms A (A = Li, Na, K, Rb) using high-level ab initio calculations. We examine the anisotropy of each intermolecular potential energy surface (PES) and the mechanism and energetics of the only available exothermic reaction pathway, CH{sub 3}X + A → CH{sub 3} + AX. The region of the transition state is explored using two-dimensional PES cuts and estimates of the activation energies are inferred. Nearly all combinations of methyl halide and alkali-metal atom have positive barrier heights, indicating that reactions at low temperatures will be slow.

  11. Alkali Metal Carbenoids: A Case of Higher Stability of the Heavier Congeners.

    PubMed

    Molitor, Sebastian; Gessner, Viktoria H

    2016-06-27

    As a result of the increased polarity of the metal-carbon bond when going down the group of the periodic table, the heavier alkali metal organyl compounds are generally more reactive and less stable than their lithium congeners. We now report a reverse trend for alkali metal carbenoids. Simple substitution of lithium by the heavier metals (Na, K) results in a significant stabilization of these usually highly reactive compounds. This allows their isolation and handling at room temperature and the first structure elucidation of sodium and potassium carbenoids. The control of stability was used to control reactivity and selectivity. Hence, the Na and K carbenoids act as selective carbene-transfer reagents, whereas the more labile lithium systems give rise to product mixtures. Additional fine tuning of the M-C interaction by means of crown ether addition further allows for control of the stability and reactivity. PMID:27100278

  12. Calculation of radiative corrections to hyperfine splittings in the neutral alkali metals

    SciTech Connect

    Sapirstein, J.; Cheng, K.T.

    2003-02-01

    The radiative correction to hyperfine splitting in hydrogen is dominated by the Schwinger term, {alpha}/2{pi} E{sub F}, where E{sub F} is the lowest-order hyperfine splitting. Binding corrections to this term, which enter as powers and logarithms of Z{alpha}, can be expected to be increasingly important in atoms with higher nuclear charge Z. Methods that include all orders of Z{alpha}, developed first to study highly charged ions, are adapted to the study of the neutral alkali metals, lithium through francium. It is shown that the use of the Schwinger term alone to account for radiative corrections to hyperfine splittings becomes qualitatively incorrect for the heavier alkali metals.0.

  13. High field superconductivity in alkali metal intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Flood, D. J.; Wagoner, D. E.; Somoano, R. B.; Rembaum, A.

    1973-01-01

    In the search for better high temperature, high critical field superconductors, a class of materials was found which have layered structures and can be intercalated with various elements and compounds. Since a large number of compounds can be formed, intercalation provides a method of control of superconducting properties. They also provide the possible medium for excitonic superconductivity. Results of magnetic field studies are presented on alkali metal (Na, K, Rb, and Cs) intercalated MoS2 (2H polymorph).

  14. Development of processes for the production of solar grade silicon from halides and alkali metals

    NASA Technical Reports Server (NTRS)

    Dickson, C. R.; Gould, R. K.

    1980-01-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon in volume at low cost were studied. Experiments were performed to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, determine the effects of reactants and/or products on materials of reactor construction, and make preliminary engineering and economic analyses of a scaled-up process.

  15. EPR study of polarons in a conducting polymer with nondegenerate ground states: Alkali metal complexes of poly (p-phenylene) and phenylene oligomers

    SciTech Connect

    Kispert, L.D.; Joseph, J.; Miller, G.G.; Baughman, R.H.

    1984-08-15

    EPR measurements are used to characterize electronic states relevant for carrier transport in alkali metal doped poly(p-phenylene), PPP, fully deuterated poly(p-phenylene), DPPP, and phenylene oligomers. Observed spin concentrations per carbon are at least one decade higher than the Curie spin concentration for Na-doped polyacetylene. The number of these spins, which likely corresponds to polarons (mobile radical anions), is much less than the amount of alkali metal dopant, suggesting that much of the charge on the polymer chains is in bipolarons (spinless dianions). Relevant to the interaction between spins on the polymer chain and the metal cations, the observed g values are close to the free electron value and do not substantially vary with the donor dopant, temperature, or the molecular weight of the phenylene chain. Although the spin-orbit effect on g values is small, room temperature linewidth tends to increase with increasing atomic number of dopant: suggesting some interaction, albeit a smaller magnitude effect than for alkali-metal graphite complexes. The EPR linewidths are exchange narrowed and proton hyperfine broadening is significant. The latter explains the generally broader linewidths for doped PPP than for doped DPPP. The measured susceptibilities have a temperature dependence which suggests equilibrium between separated polaron defects and singlet and triplet spin states formed intermolecularly via polaron pairing. The interaction is antiferromagnetic and the binding energy between polarons is about 2.2 to 3.3 meV. An upper limit estimate of the Fermi-surface density of states for K-doped PPP (0.7 states/eV phenyl) is derived from an upper limit estimate of Pauli susceptibility.

  16. Equation of state for solid rare gases and alkali metals under pressure

    NASA Astrophysics Data System (ADS)

    Bonnet, Pierre

    2016-07-01

    This investigation is based on an atomic equation of state which takes into account the excluded volume of the atom being considered. Study of solid rare gases allows following the packing factor of the solid in equilibrium with the gas at different temperatures and of the solid and the liquid in the case of solid-liquid equilibria. The application of a pressure to the solid up to 9800 MPa allows determining the decrease in atomic volume and thus the compressibility. Such a study leads to proposing a new expression through dividing the pressure derivative (as a function of the excluded volume) by the pressure. This new coefficient is a pressure-independent constant but varies with the atom considered. Multiplied by the initial atomic volume, this coefficient has a unique value for all the rare gases. Furthermore, this is also true for the series of alkali metals with however a lower value of the coefficient. The atomic configurations of the two series are very different with one free electron for the alkali metals but closed shells for the rare gases. The alkali metals are therefore more complex than the rare gases. It is worthwhile to note that study of the equilibrium has not required the use of the principles of thermodynamics.

  17. A hexagonal structure for alkali-metal doped poly (p-phenylene)

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Baughman, R. H.; Shacklette, L. W.; Fark, H.; Fink, J.

    1991-05-01

    An hexagonal structure (space group p overline62m, a = 8.6 Å) is proposed for sodium-doped poly(p-phenylene), PPP. The diffraction pattern calculated using only one freely adjustable parameter (the distance between the alkali-metal column and the polymer backbone) is in good agreement with the observed electron diffraction patterns. A similar structure ( a = 9.2 Å) is also suggested by diffraction data for potassium-doped PPP. This hexagonal structure is analogous to that reported for sodium-doped poly(p-phenylene vinylene), lithium-doped polyacetylene, and sodium-doped polyacetylene. The three chain per column arrangement provides a fundamental structural motif which maximizes the coordination of the negatively charged carbon atoms with both the alkali metal ions and the hydrogens, and maximizes interchain, intercolumn, and hydrogen to alkali-metal separations. The size of the dopant-ion relative to the cross-sectional dimensions of the host polymer determines whether the dopant-ion columns are formed in triangular (three chain per column) or tetragonal (four chain per column) channels.

  18. Solid state cell with alkali metal halo-alkali thiocyanate electrolyte

    SciTech Connect

    Rao, B. M.; Silbernagel, B. G.

    1980-02-26

    A novel electrochemical cell is disclosed utilizing: (A) an anode which contains an alkali metal as an anode-active material; (B) a cathode and (C) an electrolyte comprising an electrolytically effective amount of one or more compounds having the formula: (Ax)ma'scn wherein a is an alkali metal, X is a halogen, a' is an alkali metal and 0.1 < or = N < or = 10. Preferred systems include lithium-containing anodes, lithium-containing electrolytes and cathodes which contain cathode-active material selected from the group consisting of cathode-active sulfurs, halogens, halides, chromates, phosphates, oxides and chalcogenides, especially those chalcogenides of the empirical formula mzm wherein M is one or more metals selected from the group consisting of iron, titanium, zirconium, hafnium, niobium, tantalum and vanadium, Z is one or more chalcogens selected from the group consisting of oxygen, sulfur, selenium and tellurium, and M is a numerical value between about 1.8 and about 3.2.

  19. Design of low work function materials using alkali metal-doped transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Kim, Sol; Lee, Man Young; Lee, Seong; Jhi, Seung-Hoon

    Engineering the work function is a key issue in surface science. Particularly, discovering the materials that have work functions less than 1eV is essential for efficient thermionic energy conversion. The lowest work function of materials, reported so far, is in a range of about 1eV. To design low work function materials, we chose MX2 (M =Mo and W; X =S, Se and Te) as substrates and alkali metals (Li, Na, K, Rb and Cs) as dopants, and studied their electronic structures, charge transfer, induced surface dipole moment, and work function using first-principles calculations. We found that the charge transfer from alkali metals to MX2 substrates decreases as the atomic radius of alkali metals increases. Regardless of the amount of the charge transfer, K on WTe2 exhibits the biggest surface dipole moment, which consequently makes the surface work function the lowest. Also, we found a correlation between the binding distance and the work function.

  20. Secondary nucleation of gibbsite crystals from synthetic Bayer liquors: effect of alkali metal ions

    NASA Astrophysics Data System (ADS)

    Li, Jun; Prestidge, Clive A.; Addai-Mensah, Jonas

    2000-11-01

    The effect of alkali metal ions (Na + versus K +) on secondary nucleation of gibbsite ( γ-Al(OH) 3) from synthetic Bayer liquors has been investigated under seeded, isothermal, batch crystallisation conditions. The nucleation kinetics showed a fourth-order dependence upon Al(III) relative supersaturation and a strong temperature effect. An activation energy of 132 kJ mol -1, which was independent of alkali metal ion, was calculated. Secondary nucleation and subsequent crystal growth rates however, were greater in sodium than in potassium aluminate solution. The Arrhenius, pre-exponential factor was at least three times larger in sodium than in potassium aluminate solutions at equivalent crystal surface area, similar supersaturation and temperature. The results indicated that secondary nucleation of Al(OH) 3 is a chemical reaction-controlled process which is alkali metal ion-mediated. Na + ions provide a more favourable pathway than potassium ions for the formation of Al(III)-containing clusters, higher collision frequency between the species and crystal surface, and faster growth of potential secondary nuclei in the solutions.

  1. Note: An ion source for alkali metal implantation beneath graphene and hexagonal boron nitride monolayers on transition metals

    NASA Astrophysics Data System (ADS)

    de Lima, L. H.; Cun, H. Y.; Hemmi, A.; Kälin, T.; Greber, T.

    2013-12-01

    The construction of an alkali-metal ion source is presented. It allows the acceleration of rubidium ions to an energy that enables the penetration through monolayers of graphene and hexagonal boron nitride. Rb atoms are sublimated from an alkali-metal dispenser. The ionization is obtained by surface ionization and desorption from a hot high work function surface. The ion current is easily controlled by the temperature of ionizer. Scanning Tunneling Microscopy measurements confirm ion implantation.

  2. Note: An ion source for alkali metal implantation beneath graphene and hexagonal boron nitride monolayers on transition metals

    SciTech Connect

    Lima, L. H. de; Cun, H. Y.; Hemmi, A.; Kälin, T.; Greber, T.

    2013-12-15

    The construction of an alkali-metal ion source is presented. It allows the acceleration of rubidium ions to an energy that enables the penetration through monolayers of graphene and hexagonal boron nitride. Rb atoms are sublimated from an alkali-metal dispenser. The ionization is obtained by surface ionization and desorption from a hot high work function surface. The ion current is easily controlled by the temperature of ionizer. Scanning Tunneling Microscopy measurements confirm ion implantation.

  3. First-principles molecular dynamics of liquid alkali metals based on the quantal hypernetted chain theory

    NASA Astrophysics Data System (ADS)

    Kambayashi, Shaw; Chihara, Junzo

    1996-06-01

    A first-principles molecular dynamics (MD) scheme is presented on the basis of the density-functional (DF) theory with use of the the quantal hypernetted chain (QHNC) approximation. The DF theory brings about exact expressions for the ion-electron and ion-ion radial distribution functions (RDF) of an electron-ion mixture as a model of a simple liquid metal. These exact expressions prove that an ion-electron mixture can be treated as a one-component liquid interacting only via a pairwise interaction in the evaluation of the ion-ion RDF, and provide a set of integral equations: one is an exact integral equation for the ion-ion RDF and another for an effective ion-ion interaction, which depends on the ion configuration specified by the ion-ion RDF. Hence, after some approximations are introduced, the MD simulation can be performed to get the ion-ion RDF using the ion-ion interaction determined so as to be consistent to the ion-ion RDF: the MD simulation and the procedure to determine the effective interaction from the QHNC equation are performed iteratively. This MD simulation coupled with the QHNC equation (QHNC-MD method) for the effective interaction provides a first-principles calculation of structures of simple liquid metal: the ion-ion and electron-ion RDF's, the charge distributions of an ion and a pseudoatom, the effective ion-ion interaction and the ion-ion bridge function are evaluated in a self-consistent manner from the atomic number as the only input. We have applied this QHNC-MD method to Li, Na, K, Rb, and Cs near the melting temperature using up to 16 000 particles for the MD simulation. It is found that the convergence of the effective ion-ion interaction is fast enough for practical application to alkali metals; two MD runs are enough for convergence within accuracy of 3 to 4 digits, if the initial effective potential is properly set up. The structure factors, thus obtained, show excellent agreement with the experimental data observed by x-ray and

  4. A curious interplay in the films of N-heterocyclic carbene PtII complexes upon deposition of alkali metals

    NASA Astrophysics Data System (ADS)

    Makarova, Anna A.; Grachova, Elena V.; Niedzialek, Dorota; Solomatina, Anastasia I.; Sonntag, Simon; Fedorov, Alexander V.; Vilkov, Oleg Yu.; Neudachina, Vera S.; Laubschat, Clemens; Tunik, Sergey P.; Vyalikh, Denis V.

    2016-05-01

    The recently synthesized series of PtII complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned PtII complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination PtII centre to Pt0 and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system “Pt complex-alkali metal ion” the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the PtII complexes for a variety of biomedical, sensing, chemical, and electronic applications.

  5. A curious interplay in the films of N-heterocyclic carbene PtII complexes upon deposition of alkali metals

    PubMed Central

    Makarova, Anna A.; Grachova, Elena V.; Niedzialek, Dorota; Solomatina, Anastasia I.; Sonntag, Simon; Fedorov, Alexander V.; Vilkov, Oleg Yu.; Neudachina, Vera S.; Laubschat, Clemens; Tunik, Sergey P.; Vyalikh, Denis V.

    2016-01-01

    The recently synthesized series of PtII complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned PtII complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination PtII centre to Pt0 and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system “Pt complex-alkali metal ion”; the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the PtII complexes for a variety of biomedical, sensing, chemical, and electronic applications. PMID:27151364

  6. A curious interplay in the films of N-heterocyclic carbene Pt(II) complexes upon deposition of alkali metals.

    PubMed

    Makarova, Anna A; Grachova, Elena V; Niedzialek, Dorota; Solomatina, Anastasia I; Sonntag, Simon; Fedorov, Alexander V; Vilkov, Oleg Yu; Neudachina, Vera S; Laubschat, Clemens; Tunik, Sergey P; Vyalikh, Denis V

    2016-01-01

    The recently synthesized series of Pt(II) complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned Pt(II) complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination Pt(II) centre to Pt(0) and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system "Pt complex-alkali metal ion"; the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the Pt(II) complexes for a variety of biomedical, sensing, chemical, and electronic applications. PMID:27151364

  7. High power densities from high-temperature material interactions. [in thermionic energy conversion and metallic fluid heat pipes

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1981-01-01

    Thermionic energy conversion (TEC) and metallic-fluid heat pipes (MFHPs), offering unique advantages in terrestrial and space energy processing by virtue of operating on working-fluid vaporization/condensation cycles that accept great thermal power densities at high temperatures, share complex materials problems. Simplified equations are presented that verify and solve such problems, suggesting the possibility of cost-effective applications in the near term for TEC and MFHP devices. Among the problems discussed are: the limitation of alkali-metal corrosion, protection against hot external gases, external and internal vaporization, interfacial reactions and diffusion, expansion coefficient matching, and creep deformation.

  8. Selective removal of alkali metal cations from multiply-charged ions via gas-phase ion/ion reactions using weakly coordinating anions.

    PubMed

    Luongo, Carl A; Bu, Jiexun; Burke, Nicole L; Gilbert, Joshua D; Prentice, Boone M; Cummings, Steven; Reed, Christopher A; McLuckey, Scott A

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 (-)), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 (-)). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations. PMID:25560986

  9. Selective Removal of Alkali Metal Cations from Multiply-Charged Ions via Gas-Phase Ion/Ion Reactions Using Weakly Coordinating Anions

    NASA Astrophysics Data System (ADS)

    Luongo, Carl A.; Bu, Jiexun; Burke, Nicole L.; Gilbert, Joshua D.; Prentice, Boone M.; Cummings, Steven; Reed, Christopher A.; McLuckey, Scott A.

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 -), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 -). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations.

  10. The effect of iron vapor on electron density of hyperbaric arc plasma

    SciTech Connect

    Ogawa, Yoji

    1993-12-31

    In the hyperbaric arc welding, the arc characteristics are very strongly affected by the local density of iron vapor, because of its lower ionization potential compared with those of the components of shielding gas for hyperbaric welding such as argon and helium. The set of Saha-Eggert equations which include the ionization of iron vapor is solved from the assumption of local thermodynamic equilibrium. Particle densities of argon-helium mixed shielding gas which is contaminated by iron vapor are calculated for temperatures between 3,000 and 30,000 K and pressures between 0.1 and 100 atmospheres (0.01 and 10 MPa). The results show that electron densities at relatively low temperature are increased by iron vapor, and the amount is directly proportional to the square root of contaminated coefficient of iron vapor in the shielding gas. The effect of component ratios of argon and helium on electron densities is also considered in detail.

  11. Binding of monovalent alkali metal ions with negatively charged phospholipid membranes.

    PubMed

    Maity, Pabitra; Saha, Baishakhi; Kumar, Gopinatha Suresh; Karmakar, Sanat

    2016-04-01

    We have systematically investigated the effect of various alkali metal ions with negatively charged phospholipid membranes. Size distributions of large unilamellar vesicles have been confirmed using dynamic light scattering. Zeta potential and effective charges per vesicle in the presence of various alkali metal ions have been estimated from the measured electrophoretic mobility. We have determined the intrinsic binding constant from the zeta potential using electrostatic double layer theory. The reasonable and consistent value of the intrinsic binding constant of Na(+), found at moderate NaCl concentration (10-100 mM), indicates that the Gouy-Chapman theory cannot be applied for very high (> 100mM) and very low (< 10 mM) electrolyte concentrations. The isothermal titration calorimetry study has revealed that the net binding heat of interaction of the negatively charged vesicles with monovalent alkali metal ions is small and comparable to those obtained from neutral phosphatidylcholine vesicles. The overall endothermic response of binding heat suggests that interaction is primarily entropy driven. The entropy gain might arise due to the release of water molecules from the hydration layer vicinity of the membranes. Therefore, the partition model which does not include the electrostatic contribution suffices to describe the interaction. The binding constant of Na(+) (2.4 ± 0.1 M(-1)), obtained from the ITC, is in agreement with that estimated from the zeta potential (-2.0 M(-1)) at moderate salt concentrations. Our results suggest that hydration dynamics may play a vital role in the membrane solution interface which strongly affects the ion-membrane interaction. PMID:26802251

  12. Theory of magic optical traps for Zeeman-insensitive clock transitions in alkali-metal atoms

    SciTech Connect

    Derevianko, Andrei

    2010-05-15

    Precision measurements and quantum-information processing with cold atoms may benefit from trapping atoms with specially engineered, 'magic' optical fields. At the magic trapping conditions, the relevant atomic properties remain immune to strong perturbations by the trapping fields. Here we develop a theoretical analysis of magic trapping for especially valuable Zeeman-insensitive clock transitions in alkali-metal atoms. The involved mechanism relies on applying a magic bias B field along a circularly polarized trapping laser field. We map out these B fields as a function of trapping laser wavelength for all commonly used alkalis. We also highlight a common error in evaluating Stark shifts of hyperfine manifolds.

  13. Threshold behavior of positronium formation in positron-alkali-metal scattering

    NASA Astrophysics Data System (ADS)

    Lugovskoy, A. V.; Utamuratov, R.; Kadyrov, A. S.; Stelbovics, A. T.; Bray, I.

    2013-04-01

    We consider positron scattering on the alkali-metal atoms of Li, Na, and K at very low energies, where only the elastic scattering and positronium formation in the ground state are the two open channels. Utilizing the recently developed two-center convergent close-coupling method [Lugovskoy, Kadyrov, Bray, and Stelbovics, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.82.062708 82, 062708 (2010)] we investigate the behavior of the cross sections as the impact energy goes to zero and demonstrate their convergence. The study sets quantitative benchmarks for any rigorous theoretical treatment of the collision problems.

  14. Positron binding to alkali-metal hydrides: The role of molecular vibrations

    NASA Astrophysics Data System (ADS)

    Gianturco, Franco A.; Franz, Jan; Buenker, Robert J.; Liebermann, Heinz-Peter; Pichl, Lukáš; Rost, Jan-Michael; Tachikawa, Masanori; Kimura, Mineo

    2006-02-01

    The bound vibrational levels for J=0 have been computed for the series of alkali-metal hydride molecules from LiH to RbH, including NaH and KH. For all four molecules the corresponding potential-energy curves have been obtained for each isolated species and for its positron-bound complex (e+XH) . It is found that the calculated positron affinity values strongly depend on the molecular vibrational state for which they are obtained and invariably increase as the molecular vibrational energy content increases. The consequences of our findings on the likelihood of possibly detecting such weakly bound species are briefly discussed.

  15. Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

    NASA Astrophysics Data System (ADS)

    Rudakov, A. M.; Sergievskii, V. V.; Zhukova, T. V.

    2014-06-01

    A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Hückel equation are developed.

  16. Alkali-metal gases in optical lattices: Possible new type of quantum crystals

    NASA Astrophysics Data System (ADS)

    Meyerovich, A. E.

    2003-11-01

    Similarities between alkali-metal gases in optical lattices with noninteger occupation of the lattice sites and quantum crystals are explored. The analogy with the vacancy liquid (VL) provides an alternative explanation to the Mott transition for the recent experiment on the phase transition in the lattice. The VL can undergo Bose-Einstein condensation (BEC) with Tc within experimental reach. Direct and vacancy-assisted mechanisms of the band motion for hyperfine impurities are discussed. A large concentration of vacancies can result in the spatial decomposition of the system into pure hyperfine components. Below the vacancy condensation the impurity component resembles 3He in 3He He II mixtures.

  17. Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter

    NASA Technical Reports Server (NTRS)

    Wheeler, B. L.; Williams, R. M.; Jeffries-Nakamura, B.; Lamb, J. L.; Loveland, M. E.; Bankston, C. P.; Cole, T.

    1988-01-01

    Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.

  18. Ab initio study of electronic structure, elastic and optical properties of anti-perovskite type alkali metal oxyhalides

    NASA Astrophysics Data System (ADS)

    Ramanna, J.; Yedukondalu, N.; Ramesh Babu, K.; Vaitheeswaran, G.

    2013-06-01

    We report the structural, elastic, electronic, and optical properties of antiperovskite alkali metal oxyhalides Na3OCl, Na3OBr, and K3OBr using two different density functional methods within generalized gradient approximation (GGA). Plane wave pseudo potential (PW-PP) method has been used to calculate the ground state structural and elastic properties while the electronic structure and optical properties are calculated explicitly using full potential-linearized augmented plane wave (FP-LAPW) method. The calculated ground state properties of the investigated compounds agree quite well with the available experimental data. The predicted elastic constants using both PW-PP and FP-LAPW methods are in good accord with each other and show that the materials are mechanically stable. The low values of the elastic moduli indicate that these materials are soft in nature. The bulk properties such as shear moduli, Young's moduli, and Poisson's ratio are derived from the calculated elastic constants. Tran-Blaha modified Becke-Johnson (TB-mBJ) potential improves the band gaps over GGA and Engel-Vosko GGA. The computed TB-mBJ electronic band structure reveals that these materials are direct band gap insulators. The complex dielectric function of the metal oxyhalide compounds have been calculated and the observed prominent peaks are analyzed through the TB-mBJ electronic structures. By using the knowledge of complex dielectric function other important optical properties including absorption, reflectivity, refractive index and loss function have been obtained as a function of energy.

  19. Carboxylate Ion Pairing with Alkali-Metal Ions for β-Lactoglobulin and Its Role on Aggregation and Interfacial Adsorption.

    PubMed

    Beierlein, Frank R; Clark, Timothy; Braunschweig, Björn; Engelhardt, Kathrin; Glas, Lena; Peukert, Wolfgang

    2015-04-30

    We report a combined experimental and computational study of the whey protein β-lactoglobulin (BLG) in different electrolyte solutions. Vibrational sum-frequency generation (SFG) and ellipsometry were used to investigate the molecular structure of BLG modified air-water interfaces as a function of LiCl, NaCl, and KCl concentrations. Molecular dynamics (MD) simulations and thermodynamic integration provided details of the ion pairing of protein surface residues with alkali-metal cations. Our results at pH 6.2 indicate that BLG at the air-water interface forms mono- and bilayers preferably at low and high ionic strength, respectively. Results from SFG spectroscopy and ellipsometry are consistent with intimate ion pairing of alkali-metal cations with aspartate and glutamate carboxylates, which is shown to be more effective for smaller cations (Li(+) and Na(+)). MD simulations show not only carboxylate-alkali-metal ion pairs but also ion multiplets with the alkali-metal ion in a bridging position between two or more carboxylates. Consequently, alkali-metal cations can bridge carboxylates not only within a monomer but also between monomers, thus providing an important dimerization mechanism between hydrophilic surface patches. PMID:25825918

  20. Potential energy curves via double electron-attachment calculations: Dissociation of alkali metal dimers

    NASA Astrophysics Data System (ADS)

    Musiał, Monika; Kowalska-Szojda, Katarzyna; Lyakh, Dmitry I.; Bartlett, Rodney J.

    2013-05-01

    The recently developed method [M. Musiał, J. Chem. Phys. 136, 134111 (2012), 10.1063/1.3700438] to study double electron attached states has been applied to the description of the ground and excited state potential energy curves of the alkali metal dimers. The method is based on the multireference coupled cluster scheme formulated within the Fock space formalism for the (2,0) sector. Due to the use of the efficient intermediate Hamiltonian formulation, the approach is free from the intruder states problem. The description of the neutral alkali metal dimers is accomplished via attaching two electrons to the corresponding doubly ionized system. This way is particularly advantageous when a closed shell molecule dissociates into open shell subunits while its doubly positive cation generates the closed shell fragments. In the current work, we generate the potential energy curves for the ground and multiple excited states of the Li2 and Na2 molecules. In all cases the potential energy curves are smooth for the entire range of interatomic distances (from the equilibrium point to the dissociation limit). Based on the calculated potential energy curves, we are able to compute spectroscopic parameters of the systems studied.

  1. Conducting films of C60 and C70 by alkali-metal doping

    NASA Astrophysics Data System (ADS)

    Haddon, R. C.; Hebard, A. F.; Rosseinsky, M. J.; Murphy, D. W.; Duclos, S. J.

    1991-03-01

    The preparation is reported of alkali-metal-doped films of C60 and C70 which have electrical conductivities at room temperature comparable to those attained by n-type doped polyacetylene. The highest conductivities observed in the doped films are: 4 S/cm (Cs/C60), 100 (Rb/C60), 500 (K/C60), 20 (Na/C60), 10 (Li/C60), 2 (K/C70). The doping process is reversed on exposure of the films to the atmosphere. At high doping level, the films become more resistive. The conductivity induced in these films is attributed to the formation of energy bands from the pi orbitals of C60 or C70, which become partially filled with carriers on doping. The smaller alkali metal ions should be able to fit into the interstices in the lattice without disrupting the network of contacts between the carbon spheroids. In the case of C60, this would allow the development of an isotropic band structure, and it is proposed that these materials may constitute the first three-dimensional 'organic' conductors.

  2. Alkali metal control over N-N cleavage in iron complexes.

    PubMed

    Grubel, Katarzyna; Brennessel, William W; Mercado, Brandon Q; Holland, Patrick L

    2014-12-01

    Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber-Bosch process, there is still ambiguity about the number of Fe atoms involved during the N-N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe-N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N-N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N-N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2. PMID:25412468

  3. Subtask 12E1: Compatibility of structural materials in liquid alkali metals

    SciTech Connect

    Natesan, K.; Rink, D.L.; Haglund, R.; Clark, R.W.

    1995-03-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures that are in the range of interest for the International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal environments. Candidate structural materials are being evaluated for their compatibility, interstitial-element transfer, and corrosion in liquid alkali-metal systems such as lithium and NaK. Type 316 stainless steel and V-5Cr-5Ti coupon specimens with and without prealuminizing treatment have been exposed to NaK and lithium environments of commercial purity for times up to 3768 h at temperatures between 300 and 400{degrees}C. 13 refs., 8 figs., 3 tabs.

  4. Adiabatic hyperspherical study of weakly bound helium-helium-alkali-metal triatomic systems

    SciTech Connect

    Suno, Hiroya; Esry, B. D.

    2010-12-15

    {sup 4}He{sub 2}-alkali-metal triatomic molecular systems are studied using the adiabatic hyperspherical representation. By adopting the best pairwise He-He and He-X interaction potentials, we search for weakly bound states of {sup 4}He{sub 2}X systems with X={sup 6}Li, {sup 7}Li, {sup 23}Na, {sup 39}K, {sup 40}K, {sup 41}K, {sup 85}Rb, {sup 87}Rb, and {sup 133}Cs. We consider not only zero total angular momentum J=0 states, but also J>0 states. We find that the {sup 4}He{sub 2}{sup 6}Li and {sup 4}He{sub 2}{sup 7}Li systems each possess two bound states with J{sup {Pi}=}0{sup +} symmetry and none with J>0, while the other {sup 4}He{sub 2}-alkali-metal species are found to support one 0{sup +} and one 1{sup -} bound state. We calculate the bound-state energies of these molecular species and discuss the essential features of the wave functions associated with these bound states.

  5. Higher-order C{sub n} dispersion coefficients for the alkali-metal atoms

    SciTech Connect

    Mitroy, J.; Bromley, M.W.J.

    2005-04-01

    The van der Waals coefficients, from C{sub 11} through to C{sub 16} resulting from second-, third-, and fourth-order perturbation theory are estimated for the alkali-metal (Li, Na, K, and Rb) atoms. The dispersion coefficients are also computed for all possible combinations of the alkali-metal atoms and hydrogen. The parameters are determined from sum rules after diagonalizing a semiempirical fixed core Hamiltonian in a large basis. Comparisons of the radial dependence of the C{sub n}/r{sup n} potentials give guidance as to the radial regions in which the various higher-order terms can be neglected. It is seen that including terms up to C{sub 10}/r{sup 10} results in a dispersion interaction that is accurate to better than 1% whenever the inter-nuclear spacing is larger than 20a{sub 0}. This level of accuracy is mainly achieved due to the fortuitous cancellation between the repulsive (C{sub 11},C{sub 13},C{sub 15}) and attractive (C{sub 12},C{sub 14},C{sub 16}) dispersion forces.

  6. 3718-F Alkali Metal Treatment and Storage Facility Closure Plan. Revision 1

    SciTech Connect

    1992-11-01

    The Hanford Site, located northwest of the city of Richland, Washington, houses reactors, chemical-separation systems, and related facilities used for the production of special nuclear materials, as well as for activities associated with nuclear energy development. The 300 Area of the Hanford Site contains reactor fuel manufacturing facilities and several research and development laboratories. The 3718-F Alkali Metal Treatment and Storage Facility (3718-F Facility), located in the 300 Area, was used to store and treat alkali metal wastes. Therefore, it is subject to the regulatory requirements for the storage and treatment of dangerous wastes. Closure will be conducted pursuant to the requirements of the Washington Administrative Code (WAC) 173-303-610 (Ecology 1989) and 40 CFR 270.1. Closure also will satisfy the thermal treatment facility closure requirements of 40 CFR 265.381. This closure plan presents a description of the 3718-F Facility, the history of wastes managed, and the approach that will be followed to close the facility. Only hazardous constituents derived from 3718-F Facility operations will be addressed.

  7. Alkali Metal Control over N–N Cleavage in Iron Complexes

    PubMed Central

    2015-01-01

    Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber–Bosch process, there is still ambiguity about the number of Fe atoms involved during the N–N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe–N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N–N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N–N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2. PMID:25412468

  8. Lanthanoid/Alkali Metal β-Triketonate Assemblies: A Robust Platform for Efficient NIR Emitters.

    PubMed

    Reid, Brodie L; Stagni, Stefano; Malicka, Joanna M; Cocchi, Massimo; Sobolev, Alexandre N; Skelton, Brian W; Moore, Evan G; Hanan, Garry S; Ogden, Mark I; Massi, Massimiliano

    2015-12-01

    The reaction of hydrated lanthanoid chlorides with tribenzoylmethane and an alkali metal hydroxide consistently resulted in the crystallization of neutral tetranuclear assemblies with the general formula [Ln(Ae⋅HOEt)(L)4 ]2 (Ln=Eu(3+) , Er(3+) , Yb(3+) ; Ae=Na(+) , K(+) , Rb(+) ). Analysis of the crystal structures of these species revealed a coordination geometry that varied from a slightly distorted square antiprism to a slightly distorted triangular dodecahedron, with the specific geometrical shape being dependent on the degree of lattice solvation and identity of the alkali metal. The near-infrared (NIR)-emitting assemblies of Yb(3+) and Er(3+) showed remarkably efficient emission, characterized by significantly longer excited-state lifetimes (τobs ≈37-47 μs for Yb(3+) and τobs ≈4-6 μs for Er(3+) ) when compared with the broader family of lanthanoid β-diketonate species, even in the case of perfluorination of the ligands. The Eu(3+) assemblies show bright red emission and a luminescence performance (τobs ≈0.5 ms, ${{\\Phi}{{{\\rm L}\\hfill \\atop {\\rm Ln}\\hfill}}}$≈35-37 %, ηsens ≈68-70 %) more akin to the β-diketonate species. The results highlight that the β-triketonate ligand offers a tunable and facile system for the preparation of efficient NIR emitters without the need for more complicated perfluorination or deuteration synthetic strategies. PMID:26511032

  9. A study on optical properties of poly (ethylene oxide) based polymer electrolyte with different alkali metal iodides

    NASA Astrophysics Data System (ADS)

    Rao, B. Narasimha; Suvarna, R. Padma

    2016-05-01

    Polymer electrolytes were prepared by adding poly (ethylene glycol) dimethyl ether (PEGDME), TiO2 (nano filler), different alkali metal iodide salts RI (R+=Li+, Na+, K+, Rb+, Cs+) and I2 into Acetonitrile gelated with Poly (ethylene oxide) (PEO). Optical properties of poly (ethylene oxide) based polymer electrolytes were studied by FTIR, UV-Vis spectroscopic techniques. FTIR spectrum reveals that the alkali metal cations were coordinated to ether oxygen of PEO. The optical absorption studies were made in the wavelength range 200-800 nm. It is observed that the optical absorption increases with increase in the radius of alkali metal cation. The optical band gap for allowed direct transitions was evaluated using Urbach-edges method. The optical properties such as optical band gap, refractive index and extinction coefficient were determined. The studied polymer materials are useful for solar cells, super capacitors, fuel cells, gas sensors etc.

  10. Coordination effect-regulated CO2 capture with an alkali metal onium salts/crown ether system

    SciTech Connect

    Yang, Zhen-Zhen; Jiang, Deen; Zhu, Xiang; Tian, Chengcheng; Brown, Suree; Do-Thanh, Chi-Linh; He, Liang-Nian; Dai, Sheng

    2014-01-01

    A coordination effect was employed to realize equimolar CO2 absorption, adopting easily synthesized amino group containing absorbents (alkali metal onium salts). The essence of our strategy was to increase the steric hindrance of cations so as to enhance a carbamic acid pathway for CO2 capture. Our easily synthesized alkali metal amino acid salts or phenolates were coordinated with crown ethers, in which highly sterically hindered cations were obtained through a strong coordination effect of crown ethers with alkali metal cations. For example, a CO2 capacity of 0.99 was attained by potassium prolinate/18-crown-6, being characterized by NMR, FT-IR, and quantum chemistry calculations to go through a carbamic acid formation pathway. The captured CO2 can be stripped under very mild conditions (50 degrees C, N-2). Thus, this protocol offers an alternative for the development of technological innovation towards efficient and low energy processes for carbon capture and sequestration.

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

    NASA Technical Reports Server (NTRS)

    Hagedorn, Norman H. (Inventor)

    1993-01-01

    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.

  12. Effects of the polarizability and packing density of transparent oxide films on water vapor permeation.

    PubMed

    Koo, Won Hoe; Jeong, Soon Moon; Choi, Sang Hun; Kim, Woo Jin; Baik, Hong Koo; Lee, Sung Man; Lee, Se Jong

    2005-06-01

    The tin oxide and silicon oxide films have been deposited on polycarbonate substrates as gas barrier films, using a thermal evaporation and ion beam assisted deposition process. The oxide films deposited by ion beam assisted deposition show a much lower water vapor transmission rate than those by thermal evaporation. The tin oxide films show a similar water vapor transmission rate to the silicon oxide films in thermal evaporation but a lower water vapor transmission rate in IBAD. These results are related to the fact that the permeation of water vapor with a large dipole moment is affected by the chemistry of oxides and the packing density of the oxide films. The permeation mechanism of water vapor through the oxide films is discussed in terms of the chemical interaction with water vapor and the microstructure of the oxide films. The chemical interaction of water vapor with oxide films has been investigated by the refractive index from ellipsometry and the OH group peak from X-ray photoelectron spectroscopy, and the microstructure of the composite oxide films was characterized using atomic force microscopy and a transmission electron microscope. The activation energy for water vapor permeation through the oxide films has also been measured in relation to the permeation mechanism of water vapor. The diffusivity of water vapor for the tin oxide films has been calculated from the time lag plot, and its implications are discussed. PMID:16852387

  13. Ab initio interaction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Kedziera, Dariusz; Mentel, Łukasz; Żuchowski, Piotr S.; Knoop, Steven

    2015-06-01

    We have obtained accurate ab initio +4Σ quartet potentials for the diatomic metastable triplet helium+alkali-metal (Li, Na, K, Rb) systems, using all-electron restricted open-shell coupled cluster singles and doubles with noniterative triples corrections CCSD(T) calculations and accurate calculations of the long-range C6 coefficients. These potentials provide accurate ab initio quartet scattering lengths, which for these many-electron systems is possible, because of the small reduced masses and shallow potentials that result in a small amount of bound states. Our results are relevant for ultracold metastable triplet helium+alkali-metal mixture experiments.

  14. Method of and apparatus for measuring vapor density

    DOEpatents

    Nelson, L.D.; Cerni, T.A.

    1989-10-17

    Apparatus and method are disclosed which determine the concentration of an individual component, such as water vapor, of a multi-component mixture, such as a gaseous mixture for cooling a nuclear reactor. A hygrometer apparatus includes an infrared source for producing a broadband infrared energy beam that includes a strong water vapor absorption band and a weak water vapor absorption region. The beam is chopped to select infrared pulses. A temporally first pulse has a wavelength in the weakly absorbing region, a temporally second pulse has a wavelength in the strong band and a temporally third pulse has a wavelength in the weakly absorbing region. A fourth reference pulse representing background radiation is interposed in such chopped pulses. An indium arsenide infrared sensor is responsive to the pulses for generating an output signal in proportion to an equation given in the patent where N1 is proportional to the transmission through the sample of the first signal, N4 is related to the background radiation, and [K2 (N2-N4) + K3 (N3-N4)] is the time-weighted average of the transmission through the sample of the second and third pulses applicable at the time of the second pulse, with the reference pulse N4 being subtracted in each case to render the ratio independent of variations in the background radiation. 11 figs.

  15. Method of and apparatus for measuring vapor density

    DOEpatents

    Nelson, Loren D.; Cerni, Todd A.

    1989-01-01

    Apparatus and method determine the concentration of an individual component, such as water vapor, of a multi-component mixture, such as a gaseous mixture for cooling a nuclear reactor. A hygrometer apparatus includes an infrared source for producing a broadband infrared energy beam that includes a strong water vapor absorption band and a weak water vapor absorption region. The beam is chopped to select infrared pulses. A temporally first pulse has a wavelength in the weakly absorbing region, a temporally second pulse has a wavelength in the strong band and a temporally third pulse has a wavlength in the weakly absorbing region. A fourth reference pulse representing background radiation is interposed in such chopped pulses. An indium arsenide infrared sensor is responsive to the pulses for generating an output signal in proportion to: ##EQU1## where N1 is proportional to the transmission through the sample of the first signal, N4 is related to the background radiation, and [K2 (N2-N4)+K3 (N3-N4)] is the time-weighted average of the transmission through the sample of the second and third pulses applicable at the time of the second pulse, with the reference pulse N4 being subtracted in each case to render the ratio independent of variations in the background radiation.

  16. "XA6" octahedra influencing the arrangement of anionic groups and optical properties in inverse-perovskite [B6O10]XA3 (X = Cl, Br; A = alkali metal).

    PubMed

    Yang, Zhihua; Lei, Bing-Hua; Yang, Bin; Pan, Shilie

    2016-06-01

    Exploring the effect of microscopic units, which set up the perovsikte framework, is of importance for material design. In this study, a series of borate halides with inverse-perovskite structures [B6O10]XA3 (X = Cl, Br; A = alkali metal) have been studied. It was revealed that the distortion and volume of XA6 octahedra influence the arrangement of anionic groups, which leads to the flexibility of the perovskite-related framework and differences in optical properties. Under the structural control scheme, the structure of Rb3B6O10Cl was predicted. The stability of the predicted structure was confirmed by an ab initio density functional theory-based method. The calculation shows Rb3B6O10Cl has a short UV cutoff edge of less than 200 nm, a moderate birefringence and a large second harmonic generation response. PMID:27211304

  17. Spin-axis relaxation in spin-exchange collisions of alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Kadlecek, S.; Walker, T.; Walter, D. K.; Erickson, C.; Happer, W.

    2001-05-01

    We present calculations of spin-relaxation rates of alkali-metal atoms due to the spin-axis interaction acting in binary collisions between the atoms. We show that for the high-temperature conditions of interest here, the spin-relaxation rates calculated with classical-path trajectories are nearly the same as those calculated with the distorted-wave Born approximation. We compare these calculations to recent experiments that used magnetic decoupling to isolate spin relaxation due to binary collisions from that due to the formation of triplet van der Waals molecules. The values of the spin-axis coupling coefficients deduced from measurements of binary collision rates are consistent with those deduced from molecular decoupling experiments, and follow a physically plausible scaling law for the spin-axis coupling coefficients.

  18. Post-Harvest Processing Methods for Reduction of Silica and Alkali Metals in Wheat Straw

    SciTech Connect

    Thompson, David Neal; Lacey, Jeffrey Alan; Shaw, Peter Gordon

    2002-04-01

    Silica and alkali metals in wheat straw limit its use for bioenergy and gasification. Slag deposits occur via the eutectic melting of SiO2 with K2O, trapping chlorides at surfaces and causing corrosion. A minimum melting point of 950°C is desirable, corresponding to SiO2:K2O of about 3:1. Mild chemical treatments were used to reduce Si, K, and Cl, while varying temperature, concentration, %-solids, and time. Dilute acid was more effective at removing K and Cl, while dilute alkali was more effective for Si. Reduction of minerals in this manner may prove economical for increasing utilization of the straw for combustion or gasification.

  19. Silicon Halide-alkali Metal Flames as a Source of Solar Grade Silicon

    NASA Technical Reports Server (NTRS)

    Olson, D. B.; Gould, R. K.

    1979-01-01

    A program is presented which was aimed at determining the feasibility of using high temperature reactions of alkali metals and silicon halides to produce low cost solar-grade silicon. Experiments are being conducted to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, and determine the effects of the reactants and/or products on materials of reactor construction. During the current reporting period, the results of heat release experiments were used to design and construct a new type of thick-wall graphite reactor to produce larger quantities of silicon. A reactor test facility was constructed. Material compatibility tests were performed for Na in contact with graphite and several coated graphites. All samples were rapidly degraded at T = 1200K, while samples retained structural strength at 1700K. Pyrolytic graphite coatings cracked and separated from substances in all cases.

  20. Measurements of positron scattering by hydrogen, alkali metal, and other atoms

    NASA Astrophysics Data System (ADS)

    Stein, T. S.; Harte, M.; Jiang, J.; Kauppila, W. E.; Kwan, C. K.; Li, H.; Zhou, S.

    1998-08-01

    Recent developments in measurements of total and positronium (Ps) formation cross sections for positrons (in the energy range of 1-300 eV) scattered by hydrogen, alkali metal, and other atoms are reviewed. Measurements and calculations of total and Ps formation cross section ( QPs's) for positrons scattered by hydrogen atoms are in very good agreement, and for the most part there is also good agreement for sodium, potassium, and rubidium atoms, but there is a puzzling discrepancy between measured and recently calculated QPs's for sodium. Preliminary measurements of QPs's for Mg show a very rapid rise to a large maximum value less than 2 eV above the Ps formation threshold energy (0.8 eV) which may be related to the proximity of that threshold to zero energy. It appears that structure observed in e +-Ar and Kr QPs measurements may be related to capture of inner-subshell electrons.

  1. Alkali metal compatibility testing of candidate heater head materials for a Stirling engine heat transport system

    NASA Astrophysics Data System (ADS)

    Noble, Jack E.; Hickman, Gary L.; Grobstein, Toni

    The authors describe work performed as part of the 25-kWe advanced Stirling conversion system project. Liquid alkali metal compatibility is being assessed in an ongoing test program to evaluate candidate heater head materials and fabrication processes at the temperatures and operating conditions required for Stirling engines. Specific materials under evaluation are alloy 713LC, alloy 713LC coated with nickel aluminide, and Udimet 720, each in combination with Waspaloy. The tests were run at a constant 700 C. A eutectic alloy of sodium and potassium (NaK) was the working fluid. Titanium sheet in the system was shown to be an effective oxygen getter. Metallographic and microchemical examination of material surfaces, joints, and their interfaces revealed little or no corrosion after 1000 h. Tests are in progress, with up to 10,000 h exposure.

  2. Structure of the ambient temperature alkali metal molten salt AlCl3/LiSCN

    NASA Astrophysics Data System (ADS)

    Lee, Yi-Chia; Price, David L.; Curtiss, Larry A.; Ratner, Mark A.; Shriver, Duward F.

    2001-03-01

    The structure of the ambient temperature alkali metal molten salt system LiSCN/AlCl3 1:1 adduct was investigated by neutron diffraction, which demonstrates that the aluminum atom is surrounded by three chlorine atoms and one nitrogen atom, indicating the existence of the AlCl3NCS- anion, in which the NCS- coordinates to the Al center through nitrogen. Molecular orbital calculations using ab initio methods are also performed to study the optimized structures of the AlCl3NCS- and its isomer, AlCl3SCN-. The results are consistent with the neutron diffraction data and indicate that AlCl3NCS- is the major anionic complex in the 1:1 LiSCN/AlCl3 adduct.

  3. H-1 NMR study of ternary ammonia-alkali metal-graphite intercalation compounds

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Fronko, R. M.; Resing, H. A.; Qian, X. W.; Solin, S. A.

    1987-01-01

    For the first-stage ternary ammonia-alkali metal-graphite intercalation compounds M(NH3)(x)C24(x of about 4, M = K, Rb, Cs), three sets of triplet H-1 NMR spectral lines have been observed at various temperatures and orientations due to the H-1 - H-1 and N-14 - H-1 dipolar interactions. The structures of these compounds have been inferred as mobile (liquid-like) intercalant layers of planar M(NH3)4 ions in between the carbon layers. For the intercalated ammonia molecules, the potential barrier is about 0.2 eV and the molecular geometry is very close to the free NH3 in gas phase.

  4. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems. PMID:25317749

  5. Ternary Amides Containing Transition Metals for Hydrogen Storage: A Case Study with Alkali Metal Amidozincates.

    PubMed

    Cao, Hujun; Richter, Theresia M M; Pistidda, Claudio; Chaudhary, Anna-Lisa; Santoru, Antonio; Gizer, Gökhan; Niewa, Rainer; Chen, Ping; Klassen, Thomas; Dornheim, Martin

    2015-11-01

    The alkali metal amidozincates Li4 [Zn(NH2)4](NH2)2 and K2[Zn(NH2)4] were, to the best of our knowledge, studied for the first time as hydrogen storage media. Compared with the LiNH2-2 LiH system, both Li4 [Zn(NH2)4](NH2)2-12 LiH and K2[Zn(NH2)4]-8 LiH systems showed improved rehydrogenation performance, especially K2[Zn(NH2)4]-8 LiH, which can be fully hydrogenated within 30 s at approximately 230 °C. The absorption properties are stable upon cycling. This work shows that ternary amides containing transition metals have great potential as hydrogen storage materials. PMID:26463124

  6. Thermal characterization of an AMTEC recirculating test cell. [Alkali Metal ThermoElectric Converter

    NASA Technical Reports Server (NTRS)

    Underwood, M. L.; O'Connor, D.; Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Bankston, C. P.

    1990-01-01

    An alkali metal thermoelectric converter (AMTEC) recirculating test cell has been operated in order to determine the magnitudes of the primary heat losses of the cell and the value of the emissivity of the condenser surface. The energy balance included radiation losses, conductive losses, and losses due to the flow of sodium into the cell. The radiative heat flux dominated the heat loss mechanism of the cell at open circuit, and the condenser emissivity was calculated to be about 0.1. It is shown that, if this emissivity can be reduced to 0.02, then parasitic losses in an AMTEC recirculating test cell operating near peak power would be less than 40 percent of the heat required by the cell. The condenser emissivity decreases with elapsed time, resulting in improved thermal performance of the cell.

  7. Alkali metal compatibility testing of candidate heater head materials for a Stirling engine heat transport system

    NASA Technical Reports Server (NTRS)

    Noble, Jack E.; Hickman, Gary L.; Grobstein, Toni

    1991-01-01

    The authors describe work performed as part of the 25-kWe advanced Stirling conversion system project. Liquid alkali metal compatibility is being assessed in an ongoing test program to evaluate candidate heater head materials and fabrication processes at the temperatures and operating conditions required for Stirling engines. Specific materials under evaluation are alloy 713LC, alloy 713LC coated with nickel aluminide, and Udimet 720, each in combination with Waspaloy. The tests were run at a constant 700 C. A eutectic alloy of sodium and potassium (NaK) was the working fluid. Titanium sheet in the system was shown to be an effective oxygen getter. Metallographic and microchemical examination of material surfaces, joints, and their interfaces revealed little or no corrosion after 1000 h. Tests are in progress, with up to 10,000 h exposure.

  8. Sputtering and secondary ion emission properties of alkali metal films and adsorbed monolayers

    SciTech Connect

    Krauss, A R; Gruen, D M

    1980-01-01

    The secondary ion emission of alkali metal adsorbed monlayer and multilayer films has been studied. Profiling with sub-monolayer resolution has been performed by Auger, x-ray photoemission and secondary ion mass spectroscopy. Characteristic differences in the sputtering yields, and ion fraction have been observed which are associated with both the surface bonding properties and the mechanism leading to the formation of secondary ions. By sputtering with a negative bias applied to the sample, positive secondary ions are returned to the surface, resulting in a reduced sputter-induced erosion rate. Comparison with the results obtained with K and Li overlayers sputtered without sample bias provides an experimental value of both the total and secondary ion sputtering yields. The first and second monolayers can be readily identified and the first monolayer exhibits a lower sputtering yield and higher secondary ion fraction. This result is related to adsorption theory and measured values are compared with those obtained by thermal desorption measurements.

  9. Laboratory studies of alkali metal filter deposition, ultraviolet transmission, and visible blocking.

    PubMed

    Clarke, J T; Skinner, W R; Vincent, M B; Irgang, T; Suratkal, V; Grassl, H; Trauger, J T

    1999-03-20

    Far-ultraviolet alkali metal or Wood's filters have been produced and tested supporting the production of a flight filter for the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Sodium layers 0.5-1-microm thick transmit up to 40% in the ultraviolet while efficiently blocking visible wavelengths. The prevention of visible pinholes is assisted by a clean, sleek-free surface and a cooled substrate during deposition. The coatings are stabilized efficiently by a bismuth overcoating whose transmission spectrum is presented. We also report for the first time, to our knowledge, the first demonstrated long-wavelength cutoff from a lithium filter, with a shorter cutoff wavelength than sodium and potentially higher stability for astronomical imaging. PMID:18305811

  10. Voltammetric studies of porous molybdenum electrodes for the alkali metal thermoelectric converter

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Bankston, C. P.; Khanna, S. K.; Cole, T.

    1986-01-01

    Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from about 600 to 1000 K revealed a series of redox processes within the AMTEC operational voltage range which can be used to establish the electronic and ionic conductivities of these electrodes. Improved estimates of the free energies of formation of Na2Mo3O6, NaMoO2, and Na3MoO4 are obtained. Evidence is provided for the slow corrosive attack by Na2MoO4 on molybdenum. The ionic conductivity of Na2MoO4 is found to be sufficiently large at temperatures of greater than 700 K to explain the observed electrochemical phenomena in addition to the enhanced sodium transport in AMTEC electrodes below the freezing point of Na2MoO4.

  11. Influence of calcium chloride on the thermal behavior of heavy and alkali metals in sewage sludge incineration.

    PubMed

    Han, Jun; Xu, Minghou; Yao, Hong; Furuuchi, Masami; Sakano, Takeo; Kim, Hee Joon

    2008-01-01

    In order to separate and reuse heavy and alkali metals from flue gas during sewage sludge incineration, experiments were carried out in a pilot incinerator. The experimental results show that most of the heavy and alkali metals form condensed phase at temperature above 600 degrees C. With the addition of 5% calcium chloride into sewage sludge, the gas/solid transformation temperature of part of the metals (As, Cu, Mg and Na) is evidently decreased due to the formation of chloride, while calcium chloride seems to have no significant influence on Zn and P. Moreover, the mass fractions of some heavy and alkali metals in the collected fly ash are relatively high. For example, the mass fractions for Pb and Cu in the fly ash collected by the filter are 1.19% and 19.7%, respectively, which are well above those in lead and copper ores. In the case of adding 5% calcium chloride, the heavy and alkali metals can be divided into three groups based on their conversion temperature: Group A that includes Na, Zn, K, Mg and P, which are converted into condensed phase above 600 degrees C; Group B that includes Pb and Cu which solidify when the temperature is above 400 degrees C; and Group C that includes As, whose condensation temperature is as low as 300 degrees C. PMID:17412581

  12. Adsorption properties of carbon materials produced by thermolysis of brown coal in the presence of alkali metal hydroxides

    SciTech Connect

    Tamarkina, Y.V.; Maslova, L.A.; Khabarova, T.V.; Kucherenko, V.A.

    2008-07-15

    Activated carbons produced by thermolysis of brown coal impregnated with an alkali metal hydroxide MOH (M = Li, Na, K) at an MOH/coal ratio R-MOH = 80 mol kg{sup -1} were studied. Dependences of the adsorption capacities for iodine and Methylene Blue dye, specific surface area, and yield of activated carbons on the ratio R-MOH were obtained.

  13. Electric dipole polarizabilities at imaginary frequencies for hydrogen, the alkali-metal, alkaline-earth, and noble gas atoms

    SciTech Connect

    Derevianko, Andrei Porsev, Sergey G. Babb, James F.

    2010-05-15

    The electric dipole polarizabilities evaluated at imaginary frequencies for hydrogen, the alkali-metal atoms, the alkaline-earth atoms, and the noble gases are tabulated along with the resulting values of the atomic static polarizabilities, the atom-surface interaction constants, and the dispersion (or van der Waals) constants for the homonuclear and the heteronuclear diatomic combinations of the atoms.

  14. James C. McGroddy Prize Talk: Superconductivity in alkali-metal doped Carbon-60

    NASA Astrophysics Data System (ADS)

    Hebard, Arthur

    2008-03-01

    Carbon sixty (C60), which was first identified in 1985 in laser desorption experiments, is unquestionably an arrestingly beautiful molecule. The high symmetry of the 12 pentagonal and 20 hexagonal faces symmetrically arrayed in a soccer-ball like structure invites special attention and continues to stimulate animated speculation. The availability in 1990 of macroscopic amounts of purified C60 derived from carbon-arc produced soot allowed the growth and characterization of both bulk and thin-film samples. Crystalline C60 is a molecular solid held together by weak van der Waals forces. The fcc structure has a 74% packing fraction thus allowing ample opportunity (26% available volume) for the intercalation of foreign atoms into the interstitial spaces of the three dimensional host. This opportunity catalyzed much of the collaborative work amongst chemists, physicists and materials scientists at Bell Laboratories, and resulted in the discovery of superconductivity in alkali-metal doped C60 with transition temperatures (Tc) in the mid-30-kelvin range. In this talk I will review how the successes of this initial team effort stimulated a worldwide collaboration between experimentalists and theorists to understand the promise and potential of an entirely new class of superconductors containing only two elements, carbon and an intercalated alkali metal. Although the cuprates still hold the record for the highest Tc, there are still open scientific questions about the mechanism that gives rise to such unexpectedly high Tc's in the non-oxide carbon-based superconductors. The doped fullerenes have unusual attributes (e.g., narrow electronic bands, high disorder, anomalous energy scales, and a tantalizing proximity to a metal-insulator Mott transition), which challenge conventional thinking and at the same time provide useful insights into new directions for finding even higher Tc materials. The final chapter of the `soot to superconductivity' story has yet to be written.

  15. Method and apparatus for convection control of metallic halide vapor density in a metallic halide laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J. (Inventor)

    1982-01-01

    An apparatus is disclosed in which a reservoir containing copper chloride is heated so that the copper chloride is maintained in a liquid form. The apparatus includes a means for flowing a buffer gas (which in the exemplary embodiment is neon) over the liquid copper chloride to provide a mixture of copper chloride vapor and neon above the liquid copper chloride. A conduit provides fluid communication between the reservoir containing the copper chloride vapor/neon mixture and the laser. The copper chloride vapor density in the laser is related to the liquid copper chloride temperature and the neon flow rate through the reservoir. In accordance with a further feature of the exemplary embodiment, neon is also provided directly to the laser in order to provide a further means of controlling the copper chloride vapor density in the laser.

  16. Theoretical assessment of the electro-optical features of the group III nitrides (B12N12, Al12N12 and Ga12N12) and group IV carbides (C24, Si12C12 and Ge12C12) nanoclusters encapsulated with alkali metals (Li, Na and K)

    NASA Astrophysics Data System (ADS)

    Tahmasebi, Elham; Shakerzadeh, Ehsan; Biglari, Zeinab

    2016-02-01

    Density functional theory (DFT) calculations have been carried out to study the influence of alkali metals (Li, Na and K) encapsulation within the group III nitrides (B12N12, Al12N12 and Ga12N12) and the group IV carbides (C24, Si12C12and Ge12C12) nanoclusters. The encapsulation of Li, Na and K atoms is found to narrow the HOMO-LUMO gaps of the considered clusters. The electronic properties of these clusters, especially the group III nitrides nanoclusters, are strongly sensitive to interaction with the alkali metals. Moreover it is observed that the encapsulation of alkali metals enhances the first hyperpolarizabilities of B12N12 nanocluster. Surprisingly, due to the alkali metals encapsulation within B12N12 nanocluster, the first hyperpolarizability values are remarkably increased to 8505.49 and 122,503.76 a.u. for Na@B12N12 and K@B12N12, respectively. Also the TD-DFT calculations at both CAM-B3LYP/6-311+G(d) and PBE0/6-311+G(d) levels of theory are also performed to investigate the origin of first hyperpolarizabilities.

  17. Vapor Liquid Equilibria of Hydrofluorocarbons Using Dispersion-Corrected and Nonlocal Density Functionals.

    PubMed

    Goel, Himanshu; Butler, Charles L; Windom, Zachary W; Rai, Neeraj

    2016-07-12

    Recent developments in dispersion corrected and nonlocal density functionals are aimed at accurately capturing dispersion interactions, a key shortcoming of local and semilocal approximations of density functional theory. These functionals have shown significant promise for dimers and small clusters of molecules as well as crystalline materials. However, their efficacy for predicting vapor liquid equilibria is largely unexplored. In this work, we examine the accuracy of dispersion-corrected and nonlocal van der Waals functionals by computing the vapor liquid coexistence curves (VLCCs) of hydrofluoromethanes. Our results indicate that the PBE-D3 functional performs significantly better in predicting saturated liquid densities than the rVV10 functional. With the PBE-D3 functional, we also find that as the number of fluorine atoms increase in the molecule, the accuracy of saturated liquid density prediction improves as well. All the functionals significantly underpredict the saturated vapor densities, which also result in an underprediction of saturated vapor pressure of all compounds. Despite the differences in the bulk liquid densities, the local microstructures of the liquid CFH3 and CF2H2 are relatively insensitive to the density functional employed. For CF3H, however, rVV10 predicts slightly more structured liquid than the PBE-D3 functional. PMID:27295451

  18. The Synthesis and Characterization of Ionic Liquids for Alkali-Metal Batteries and a Novel Electrolyte for Non-Humidified Fuel Cells

    NASA Astrophysics Data System (ADS)

    Tucker, Telpriore G.

    This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries and 2) gel membrane for proton conduction in fuel cells; where overall aims were encouraged by the U.S. Department of Energy. Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300ºC) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl 4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping >140ºC. Battery testing based on [EMI+][FeCl4 -] with NaAlCl4 functioned exceptional (range 150-180ºC) at an impressive energy efficiency >96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br 7, melted at 94ºC. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62ºC ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265ºC and less expensive chemical synthesis. [PBr4 +][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements. Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases

  19. Room temperature inorganic ``quasi-molten salts`` as alkali-metal electrolytes

    SciTech Connect

    Xu, K.; Zhang, S.; Angell, C.A.

    1996-11-01

    Room temperature inorganic liquids of high ionic conductivity have been prepared by reacting Lewis acid AlCl with sulfonyl chlorides. The mechanism is not clear at this time since a crystal structure study of the 1:1 complex with CH{sub 3}SO{sub 2}Cl (T{sub m} = 30 C) is not consistent with a simple chloride transfer to create AlClO{sub 4}{sup {minus}} anions. The liquid is in a state somewhere between ionic and molecular. A new term quasi-molten salt is adopted to describe this state. A comparably conducting liquid can be made using BCL{sub 3} in place of AlCl{sub 3}. Unlike their organic counterparts based on ammonium cations (e.g., pyridinium or imidazolium) which reduce in the presence of alkali metals, this inorganic class of cation shows great stability against electrochemical reduction (ca. {minus}1.0 V vs. Li{sup +}/Li), with the useful consequence that reversible lithium and sodium metal deposition/stripping can be supported. The electrochemical window for these quasi-salts with AlCl{sub 3} ranges up to 5.0 V, and their room temperature conductivities exceed 10{sup {minus}4} S/cm. They dissolve lithium and sodium tetrachloroaluminates up to mole fraction {approximately} 0.6 at 100 C and intermediate compositions are permanently stable at ambient. The resultant lithium or sodium salt solutions exhibit electrochemical windows of 4.5--5.0 V vs. Li{sup +}/Li or Na{sup +}/Na and show room temperature conductivities of 10{sup {minus}3.0}--10{sup {minus}2.5} S/cm. In preliminary charge/discharge tests, the cell Li/``quasi-ionic liquid electrolyte``/Li{sub 1+x}Mn{sub 2}O{sub 4} showed a discharge capacity of ca. 110 mAh/(g of cathode) and sustained 80% of the initial capacity after 60 cycles, indicating that these quasi-molten salt-based electrolytes are promising candidates for alkali-metal batteries.

  20. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, K.; Berzins, L.; Galkowski, J.; Seng, R.

    1996-08-27

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer`s law. 6 figs.

  1. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, Karla; Berzins, Leon; Galkowski, Joseph; Seng, Rita

    1996-01-01

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer's law.

  2. Density-Driven Migration of Heavy NAPL Vapor in the Unsaturated Zone

    NASA Astrophysics Data System (ADS)

    Kleinknecht, S. M.; Class, H.; Braun, J.

    2014-12-01

    Contamination of the subsoil is a major concern in industrially developed as well as developing countries. Liquids introduced into the unsaturated zone will migrate as a liquid phase, however, they will also vaporize and migrate in a gaseous state. In particular, vapor (gas) plumes migrate easily in the unsaturated zone. Heavy vapors migrate, preferentially downward, due to their greater density and thus pose a potential threat to aquifers. Large scale column experiments and numerical simulations were conducted to investigate migration of carbon disulfide vapor. Carbon disulfide (CS2), amongst others used for the manufacture of viscous rayon, is an industrial, non-polar solvent. It is highly volatile and characterized by a higher density than water (ρ = 1.263 g/cm3) and, above all, denser than air when in a gaseous state (1.6 compared to air). The goals of these investigations were to quantitatively describe density-driven vapor migration in the subsurface at a large scale with clearly defined and controlled boundary conditions. The experiments were conducted in vertical, large columns (ID = 0.109 m) of 4 m length packed with dry porous medium in which the migration behavior of CS2vapor was characterized. Different types of glass beads were used to investigate the influence of permeability. The porous medium was kept dry to avoid partitioning effects due to pore water. The upper and lower boundaries were open to the atmosphere and hence constant pressure boundaries which allowed for an unhindered migration of the heavy vapor injected in the middle section of the column. Gas samples were taken along the column throughout the experiment and analyzed using a GC (HP 6890 Series) to quantify time and space dependent migration. The set-up of the experiment was numerically reproduced employing a 1-D, two-phase, two-component, isothermal model. Simulation results were compared with data from vapor migration experiments to verify the model. Variations were performed to

  3. Ground state of the polar alkali-metal-atom-strontium molecules: Potential energy curve and permanent dipole moment

    SciTech Connect

    Guerout, R.; Aymar, M.; Dulieu, O.

    2010-10-15

    In this study, we investigate the structure of the polar alkali-metal-atom-strontium diatomic molecules as possible candidates for the realization of samples of ultracold polar molecular species not yet investigated experimentally. Using a quantum chemistry approach based on effective core potentials and core polarization potentials, we model these systems as effective three-valence-electron systems, allowing for calculation of electronic properties with full configuration interaction. The potential curve and the permanent dipole moment of the {sup 2}{Sigma}{sup +} ground state are determined as functions of the internuclear distance for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-metal-atom-Rb molecules.

  4. Characterization of Adsorbed Alkali Metal Ions in 2:1 Type Clay Minerals from First-Principles Metadynamics.

    PubMed

    Ikeda, Takashi; Suzuki, Shinichi; Yaita, Tsuyoshi

    2015-07-30

    Adsorption states of alkali metal ions in three kinds of 2:1 type clay minerals are systematically investigated via first-principles-based metadynamics. Our reconstructed free energy surfaces in a two-dimensional space of coordination numbers specifically employed as collective variables for describing the interlayer cations show that an inner-sphere (IS) complex is preferentially formed for Cs(+) in the 2:1 type trioctahedral clay minerals with saponite-like compositions, where lighter alkali metal ions show a tendency to form an outer-sphere one instead. The strong preference for an IS complex observed for Cs(+) is found to result partially from the capability of recognizing selectively Cs(+) ions at the basal O atoms with the Lewis basicity significantly enhanced by the isomorphic substitution in tetrahedral sheets. PMID:26151150

  5. Mobile lidar system for measurement of water vapor mixing ratio and ozone number density

    NASA Technical Reports Server (NTRS)

    Whiteman, D.

    1988-01-01

    The Water Vapor Lidar was modified and extended to make differential absorption measurements of ozone. Water vapor measurements make use of a weak molecular scattering process known as Raman scattering. It is characterized by a shift in wavelength of the scattered beam of light relative to the incident one. Some of the energy of the incident photon is converted to vibrational or rotational energy within the molecule leaving the scattered photon shifted to a slightly longer wavelength. When performing water vapor measurements, profiles are acquired of water vapor mixing ratio from near the ground to beyond 7 km every 2 minutes. By forming a color composite image of the individual profiles, the spatial and temporal evolution of water vapor is visible with vertical resolution of 75 to 150m and temporal resolution of 2 minutes. The ozone lidar is intended for use as a cross calibration facility for other stationary ozone lidar systems. The ozone measurement employs the technique known as differential absorption. The backscattered laser radiation from two different wavelengths is measured. Successful measurements of 308 nm returns were made from 80 km with an averaging period of 6 hours. Using these data and a standard atmosphere density curve, an ozone number density profile was made which agrees very well with the standard ozone curve between 20 and 40 km.

  6. Alkali metal pool boiler life tests for a 25 kWe advanced Stirling conversion system

    NASA Astrophysics Data System (ADS)

    Anderson, W. G.; Rosenfeld, J. H.; Noble, J.

    The overall operating temperature and efficiency of solar-powered Stirling engines can be improved by adding an alkali metal pool boiler heat transport system to supply heat more uniformly to the heater head tubes. One issue with liquid metal pool boilers is unstable boiling. Stable boiling is obtained with an enhanced boiling surface containing nucleation sites that promote continuous boiling. Over longer time periods, it is possible that the boiling behavior of the system will change. An 800-h life test was conducted to verify that pool boiling with the chosen fluid/surface combination remains stable as the system ages. The apparatus uses NaK boiling on a - 100 + 140 stainless steel sintered porous layer, with the addition of a small amount of xenon. Pool boiling remained stable to the end of life test. The pool boiler life test included a total of 82 cold starts, to simulate startup each morning, and 60 warm restarts, to simulate cloud cover transients. The behavior of the cold and warm starts showed no significant changes during the life test. In the experiments, the fluid/surface combination provided stable, high-performance boiling at the operating temperature of 700 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

  7. Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Yi, Ming; Tian, Wei; Bourret-Courchesne, Edith; Birgeneau, Robert J.

    2016-02-01

    The complex interdigitated phases have greatly frustrated attempts to document the basic features of the superconductivity in the alkali metal intercalated iron chalcogenides. Here, using elastic neutron scattering, energy-dispersive x-ray spectroscopy, and resistivity measurements, we elucidate the relations of these phases in RbxFeySe2 -zSz . We find (i) the iron content is crucial in stabilizing the stripe antiferromagnetic (AF) phase with rhombic iron vacancy order (y ≈1.5 ) , the block AF phase with √{5 }×√{5 } iron vacancy order (y ≈1.6 ) , and the iron vacancy-free phase (y ≈2 ) ; and (ii) the iron vacancy-free superconducting phase (z =0 ) evolves into an iron vacancy-free metallic phase with sulfur substitution (z >1.5 ) due to the progressive decrease of the electronic correlation strength. Both the stripe AF phase and the block AF phase are Mott insulators. The iron-rich compounds (y >1.6 ) undergo a first order transition from an iron vacancy disordered phase at high temperatures into the √{5 }×√{5 } iron vacancy ordered phase and the iron vacancy-free phase below Ts. Our data demonstrate that there are miscibility gaps between these three phases. The existence of the miscibility gaps in the iron content is a key to understanding the relationship between these complicated phases.

  8. A novel alkali metals/strontium co-substituted calcium polyphosphate scaffolds in bone tissue engineering.

    PubMed

    Song, Wei; Wang, Qiguang; Wan, Changxiu; Shi, Tong; Markel, David; Blaiser, Ralph; Ren, Weiping

    2011-08-01

    Our purpose of this study is to develop potassium or sodium/strontium co-substituted calcium polyphosphate (K/Sr-CPP or Na/Sr-CPP) bioceramics in application of bone repairing scaffold. The incorporation of K, Na, and Sr into CPP substrate via a calcining-sintering process was confirmed by X-ray diffractometry and inductively coupled plasma atomic emission spectroscopy. In vitro degradation study of co-substituted CPP indicated the incorporation of alkali metal elements promoted the degradability of CPP, and the scanning electron microscope showed the apatite-like minerals were precipitated on the surface of co-substituted CPP. The compress resistant strength of co-substituted CPP was elevated by dopants. The MTT assay and confocal laser-scanning microscope on osteoblasts culturing with co-substituted CPP showed no cytotoxicity. The cell proliferation on co-substituted CPP was even better than others. Thus, this co-substituted CPP bioceramics might have potential of applications in orthopedic field. PMID:21732528

  9. Silicon halide-alkali metal flames as a source of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Olsen, D. B.; Miller, W. J.

    1979-01-01

    The feasibility of using alkali metal-silicon halide diffusion flames to produce solar-grade silicon in large quantities and at low cost is demonstrated. Prior work shows that these flames are stable and that relatively high purity silicon can be produced using Na + SiCl4 flames. Silicon of similar purity is obtained from Na + SiF4 flames although yields are lower and product separation and collection are less thermochemically favored. Continuous separation of silicon from the byproduct alkali salt was demonstrated in a heated graphite reactor. The process was scaled up to reduce heat losses and to produce larger samples of silicon. Reagent delivery systems, scaled by a factor of 25, were built and operated at a production rate of 0.5 kg Si/h. Very rapid reactor heating rates are observed with wall temperatures reaching greater than 2000 K. Heat release parameters were measured using a cooled stainless steel reactor tube. A new reactor was designed.

  10. Interaction of alkali metals with perylene-3,4,9,10- tetracarboxylic-dianhydride thin films

    SciTech Connect

    Wuesten, J.; Berger, S.; Heimer, K.; Lach, S.; Ziegler, Ch.

    2005-07-01

    n doping of the molecular organic semiconductor perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) is often achieved by use of alkali metals as dopants. This doping process is commonly performed in two steps. In the first the dopant is evaporated onto the surface of the PTCDA film. As it has been believed that the dopant shows an inhomogeneous diffusion profile through the layer with most of the dopant accumulated in the first few layers, a subsequent annealing step has been performed in order to reach a homogeneous distribution of the dopant in the whole layer. In this paper experimental results concerning chemical composition ((angle resolved) X-ray photoemission spectroscopy, secondary-ion-mass spectrometry, Fourier transform infrared spectroscopy), electronic structure (ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy), as well as electrical properties (conductivity, Seebeck coefficient) are shown before and after doping and before and after annealing. These results suggest that the deposited dopant is redistributed and partially removed during the annealing step. A model for the dopant distribution is suggested.

  11. Atomic many-body effects and Lamb shifts in alkali metals

    NASA Astrophysics Data System (ADS)

    Ginges, J. S. M.; Berengut, J. C.

    2016-05-01

    We present a detailed study of the radiative potential method [V. V. Flambaum and J. S. M. Ginges, Phys. Rev. A 72, 052115 (2005), 10.1103/PhysRevA.72.052115], which enables the accurate inclusion of quantum electrodynamics (QED) radiative corrections in a simple manner in atoms and ions over the range 10 ≤Z ≤120 , where Z is the nuclear charge. Calculations are performed for binding energy shifts to the lowest valence s , p , and d waves over the series of alkali-metal atoms Na to E119. The high accuracy of the radiative potential method is demonstrated by comparison with rigorous QED calculations in frozen atomic potentials, with deviations on the level of 1%. The many-body effects of core relaxation and second- and higher-order perturbation theory on the interaction of the valence electron with the core are calculated. The inclusion of many-body effects tends to increase the size of the shifts, with the enhancement particularly significant for d waves; for K to E119, the self-energy shifts for d waves are only an order of magnitude smaller than the s -wave shifts. It is shown that taking into account many-body effects is essential for an accurate description of the Lamb shift.

  12. An extended basis set {ital ab} {ital initio} study of alkali metal cation--water clusters

    SciTech Connect

    Feller, D.; Glendening, E.D.; Woon, D.E.; Feyereisen, M.W.

    1995-09-01

    Ionic clusters comprised of a single alkali metal cation and up to eight water molecules were studied at the Hartree--Fock and correlated levels of theory using the correlation consistent sequence of basis sets. Estimates of the degree of convergence in the computed properties with respect to the complete basis set limit were facilitated by the underlying systematic manner in which the correlation consistent sets approach completeness. In favorable cases, improved property values could be obtained by fitting finite basis set results with a simple analytical expression in order to extrapolate to the complete basis set limit. The sensitivity of structures and binding energies were analyzed with regard to the inclusion of valence and core-valence correlation recovery at the MP2, MP4, and CCSD(T) levels of theory. The replacement of metal core electrons and the introduction of relativistic contributions via effective core potentials was compared to corresponding all-electron results. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  13. Alkali metal pool boiler life tests for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Noble, J.

    1991-01-01

    The overall operating temperature and efficiency of solar-powered Stirling engines can be improved by adding an alkali metal pool boiler heat transport system to supply heat more uniformly to the heater head tubes. One issue with liquid metal pool boilers is unstable boiling. Stable boiling is obtained with an enhanced boiling surface containing nucleation sites that promote continuous boiling. Over longer time periods, it is possible that the boiling behavior of the system will change. An 800-h life test was conducted to verify that pool boiling with the chosen fluid/surface combination remains stable as the system ages. The apparatus uses NaK boiling on a - 100 + 140 stainless steel sintered porous layer, with the addition of a small amount of xenon. Pool boiling remained stable to the end of life test. The pool boiler life test included a total of 82 cold starts, to simulate startup each morning, and 60 warm restarts, to simulate cloud cover transients. The behavior of the cold and warm starts showed no significant changes during the life test. In the experiments, the fluid/surface combination provided stable, high-performance boiling at the operating temperature of 700 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

  14. Mechanism for alkali metal-catalyzed CO/sub 2/ gasification of carbon

    SciTech Connect

    Saber, J.M.

    1987-01-01

    Alkali metal-catalyzed gasification of carbon by CO/sub 2/ was studied using Temperature-programmed reaction and isotopic tracers. Between 500 and 1000 K, oxide groups on the carbon surface interact with potassium carbonate to form carbonate/oxygen/carbon complexes. The complexes exchange carbon and oxygen isotopes readily with gas-phase carbon dioxide. Sodium carbonate, however, does not appear to complex with the surface oxide groups under these conditions. The surface oxide groups also stabilize potassium on the carbon surface, thus, less potassium volatilizes from higher-oxygen-content carbons than from lower oxygen content carbons. Above 1000 K, both potassium and sodium carbonate decompose coincident with catalyzed CO/sub 2/ gasification to form a metal oxide with a metal:oxygen ratio of 2. The oxide can be oxidized to give a metal:0 ratio of 1. The carbonate does not appear to be the catalytically active species. Reactions describing Na-catalyzed gasification via oxygen. Transfer mechanisms are proposed.

  15. Research Investigation Directed Toward Extending the Useful Range of the Electromagnetic Spectrum. [atomic spectra and electronic structure of alkali metals

    NASA Technical Reports Server (NTRS)

    Hartmann, S. R.; Happer, W.

    1974-01-01

    The report discusses completed and proposed research in atomic and molecular physics conducted at the Columbia Radiation Laboratory from July 1972 to June 1973. Central topics described include the atomic spectra and electronic structure of alkali metals and helium, molecular microwave spectroscopy, the resonance physics of photon echoes in some solid state systems (including Raman echoes, superradiance, and two photon absorption), and liquid helium superfluidity.

  16. Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

    PubMed

    Lee, Myung Churl; Choi, Wonyong

    2002-03-15

    Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas. PMID:11944694

  17. Properties of alkali metal atoms deposited on a MgO surface: a systematic experimental and theoretical study.

    PubMed

    Finazzi, Emanuele; Di Valentin, Cristiana; Pacchioni, Gianfranco; Chiesa, Mario; Giamello, Elio; Gao, Hongjun; Lian, Jichun; Risse, Thomas; Freund, Hans-Joachim

    2008-01-01

    The adsorption of small amounts of alkali metal atoms (Li, Na, K, Rb, and Cs) on the surface of MgO powders and thin films has been studied by means of EPR spectroscopy and DFT calculations. From a comparison of the measured and computed g values and hyperfine coupling constants (hfccs), a tentative assignment of the preferred adsorption sites is proposed. All atoms bind preferentially to surface oxide anions, but the location of these anions differs as a function of the deposition temperature and alkali metal. Lithium forms relatively strong bonds with MgO and can be stabilized at low temperatures on terrace sites. Potassium interacts very weakly with MgO and is stabilized only at specific sites, such as at reverse corners where it can interact simultaneously with three surface oxygen atoms (rubidium and cesium presumably behave in the same way). Sodium forms bonds of intermediate strength and could, in principle, populate more than a single site when deposited at room temperature. In all cases, large deviations of the hfccs from the gas-phase values are observed. These reductions in the hfccs are due to polarization effects and are not connected to ionization of the alkali metal, which would lead to the formation of an adsorbed cation and a trapped electron. In this respect, hydrogen atoms behave completely differently. Under similar conditions, they form (H(+))(e(-)) pairs. The reasons for this different behavior are discussed. PMID:18381711

  18. Element specificity of ortho-positronium annihilation for alkali-metal loaded SiO{sub 2} glasses

    SciTech Connect

    Sato, K.; Hatta, T.

    2015-03-07

    Momentum distributions associated with ortho-positronium (o-Ps) pick-off annihilation photon are often influenced by light elements, as, e.g., carbon, oxygen, and fluorine. This phenomenon, so-called element specificity of o-Ps pick-off annihilation, has been utilized for studying the elemental environment around the open spaces. To gain an insight into the element specificity of o-Ps pick-off annihilation, the chemical shift of oxygen 1s binding energy and the momentum distributions associated with o-Ps pick-off annihilation were systematically investigated for alkali-metal loaded SiO{sub 2} glasses by means of X-ray photoelectron spectroscopy and positron-age-momentum correlation spectroscopy, respectively. Alkali metals introduced into the open spaces surrounded by oxygen atoms cause charge transfer from alkali metals to oxygen atoms, leading to the lower chemical shift for the oxygen 1s binding energy. The momentum distribution of o-Ps localized into the open spaces is found to be closely correlated with the oxygen 1s chemical shift. This correlation with the deepest 1s energy level evidences that the element specificity of o-Ps originates from pick-off annihilation with orbital electrons, i.e., dominantly with oxygen 2p valence electrons and s electrons with lower probability.

  19. Negative ion production by backscattering from alkali-metal surfaces bombarded by ions of hydrogen and deuterium

    SciTech Connect

    Schneider, P.J.

    1980-03-01

    Measurements have been made of the total backscattered D/sup -/ and H/sup -/ yields from thick, clean targets of Cs, Rb, K, Na, and Li, bombarded with H/sub 2//sup +/, H/sub 3//sup +/, D/sub 2//sup +/, and D/sub 3//sup +/ with incident energies from 0.15 to 4.0 keV/nucleus. All of the measurements were made at background pressures less than 10/sup -9/ Torr and the alkali-metal targets were evaporated onto a cold substrate (T = 77K) in situ to assure thick, uncontaminated targets. Measurements of the H/sup -/ yield from various transition metal targets with thin coverages of alkali-metals have also been made as a function of the surface work function. The negative ion yields are discussed in terms of the probabilities of reflection of the incident particles, of formation of the negative ion at the surface and of the survival of the negative ion leaving the surface. For each thick alkali-metal target, the negative ion yield measurements have been used in a least squares fit to determine two parameters in a theoretically derived expression for the negative ion yield. The parameters obtained from a thick Na target have been used to calculate the yield from a Cu target with thin coverage of Na (such that the surface work function is equal to thick Na).

  20. Physical vapor deposited aluminum foils from high energy density physics experiments

    SciTech Connect

    Barthell, B.L.; Anderson, W.E.; Gomez, V.M.; Henneke, B.F.; Moore, J.E.; Reeves, G.A.; Salazar, M.A.; Townsend, J.D.

    1995-09-01

    Fabrication of cylindrical aluminum load foils and graded thickness aluminum vacuum opening switch foils is described. Load foils are vaporized by joule heating and imploded by J {times} B forces to stagnate on axis and create soft x-rays. Plasma flow switch foils are mounted to shunt the vacuum power flow channel of a coaxial gun and are vaporized by joule heating. The resultant graded density plasma is magnetically driven down the annular power flow channel. Opening switch action occurs when the shunt plasma crosses a load slot in the center conductor. These foil components have been used in both the Pegasus and Procyon experiments.

  1. Iron-catalysed propylene epoxidation by nitrous oxide: dramatic shift of allylic oxidation to epoxidation by the modification with alkali metal salts.

    PubMed

    Wang, Xiaoxing; Zhang, Qinghong; Guo, Qian; Lou, Yinchuan; Yang, Lujuan; Wang, Ye

    2004-06-21

    A dramatic shift of allylic oxidation to epoxidation has been observed during the oxidation of propylene by N(2)O when the FeO(x)/SBA-15 catalyst is modified with alkali metal salts, and the roles of alkali metal salts are to suppress the reactivity of lattice oxygen and to induce an iron coordination structure effective for epoxidation with N(2)O. PMID:15179482

  2. New density functional approach for solid-liquid-vapor transitions in pure materials.

    PubMed

    Kocher, Gabriel; Provatas, Nikolas

    2015-04-17

    A new phase field crystal (PFC) type theory is presented, which accounts for the full spectrum of solid-liquid-vapor phase transitions within the framework of a single density order parameter. Its equilibrium properties show the most quantitative features to date in PFC modeling of pure substances, and full consistency with thermodynamics in pressure-volume-temperature space is demonstrated. A method to control either the volume or the pressure of the system is also introduced. Nonequilibrium simulations show that 2- and 3-phase growth of solid, vapor, and liquid can be achieved, while our formalism also allows for a full range of pressure-induced transformations. This model opens up a new window for the study of pressure driven interactions of condensed phases with vapor, an experimentally relevant paradigm previously missing from phase field crystal theories. PMID:25933321

  3. New Density Functional Approach for Solid-Liquid-Vapor Transitions in Pure Materials

    NASA Astrophysics Data System (ADS)

    Kocher, Gabriel; Provatas, Nikolas

    2015-04-01

    A new phase field crystal (PFC) type theory is presented, which accounts for the full spectrum of solid-liquid-vapor phase transitions within the framework of a single density order parameter. Its equilibrium properties show the most quantitative features to date in PFC modeling of pure substances, and full consistency with thermodynamics in pressure-volume-temperature space is demonstrated. A method to control either the volume or the pressure of the system is also introduced. Nonequilibrium simulations show that 2- and 3-phase growth of solid, vapor, and liquid can be achieved, while our formalism also allows for a full range of pressure-induced transformations. This model opens up a new window for the study of pressure driven interactions of condensed phases with vapor, an experimentally relevant paradigm previously missing from phase field crystal theories.

  4. Ca(2+) function in photosynthetic oxygen evolution studied by alkali metal cations substitution.

    PubMed

    Ono, T; Rompel, A; Mino, H; Chiba, N

    2001-10-01

    Effects of adding monovalent alkali metal cations to Ca(2+)-depleted photosystem (PS)II membranes on the biochemical and spectroscopic properties of the oxygen-evolving complex were studied. The Ca(2+)-dependent oxygen evolution was competitively inhibited by K(+), Rb(+), and Cs(+), the ionic radii of which are larger than the radius of Ca(2+) but not inhibited significantly by Li(+) and Na(+), the ionic radii of which are smaller than that of Ca(2+). Ca(2+)-depleted membranes without metal cation supplementation showed normal S(2) multiline electron paramagnetic resonance (EPR) signal and an S(2)Q(A)(-) thermoluminescence (TL) band with a normal peak temperature after illumination under conditions for single turnover of PSII. Membranes supplemented with Li(+) or Na(+) showed properties similar to those of the Ca(2+)-depleted membranes, except for a small difference in the TL peak temperatures. The peak temperature of the TL band of membranes supplemented with K(+), Rb(+), or Cs(+) was elevated to approximately 38 degrees C which coincided with that of Y(D)(+)Q(A)(-) TL band, and no S(2) EPR signals were detected. The K(+)-induced high-temperature TL band and the S(2)Q(A)(-) TL band were interconvertible by the addition of K(+) or Ca(2+) in the dark. Both the Ca(2+)-depleted and the K(+)-substituted membranes showed the narrow EPR signal corresponding to the S(2)Y(Z)(+) state at g = 2 by illuminating the membranes under multiple turnover conditions. These results indicate that the ionic radii of the cations occupying Ca(2+)-binding site crucially affect the properties of the manganese cluster. PMID:11566758

  5. Design and Test of Advanced Thermal Simulators for an Alkali Metal-Cooled Reactor Simulator

    NASA Technical Reports Server (NTRS)

    Garber, Anne E.; Dickens, Ricky E.

    2011-01-01

    The Early Flight Fission Test Facility (EFF-TF) at NASA Marshall Space Flight Center (MSFC) has as one of its primary missions the development and testing of fission reactor simulators for space applications. A key component in these simulated reactors is the thermal simulator, designed to closely mimic the form and function of a nuclear fuel pin using electric heating. Continuing effort has been made to design simple, robust, inexpensive thermal simulators that closely match the steady-state and transient performance of a nuclear fuel pin. A series of these simulators have been designed, developed, fabricated and tested individually and in a number of simulated reactor systems at the EFF-TF. The purpose of the thermal simulators developed under the Fission Surface Power (FSP) task is to ensure that non-nuclear testing can be performed at sufficiently high fidelity to allow a cost-effective qualification and acceptance strategy to be used. Prototype thermal simulator design is founded on the baseline Fission Surface Power reactor design. Recent efforts have been focused on the design, fabrication and test of a prototype thermal simulator appropriate for use in the Technology Demonstration Unit (TDU). While designing the thermal simulators described in this paper, effort were made to improve the axial power profile matching of the thermal simulators. Simultaneously, a search was conducted for graphite materials with higher resistivities than had been employed in the past. The combination of these two efforts resulted in the creation of thermal simulators with power capacities of 2300-3300 W per unit. Six of these elements were installed in a simulated core and tested in the alkali metal-cooled Fission Surface Power Primary Test Circuit (FSP-PTC) at a variety of liquid metal flow rates and temperatures. This paper documents the design of the thermal simulators, test program, and test results.

  6. Building a Chemical Intuition Under Pressure: Prediction of Alkali Metal Polyhydrides and Subhydrides

    NASA Astrophysics Data System (ADS)

    Zurek, Eva

    2013-06-01

    Stabilization of solid phases with unusual combinations or stoichiometries, and unexpected electronic structures may be achieved by applying external pressure. The prediction of these structures using our chemical intuition (developed at 1 atmosphere) would be exceedingly difficult, making automated structure search techniques prudent. For this reason, we have written XtalOpt, an open-source evolutionary algorithm for crystal structure prediction. Whereas at 1 atmosphere the classic alkali hydrides combine in a one-to-one ratio, M+H-, under pressure non-classic stoichiometries MHn(n > 1) and MmH (m > 1) are preferred. For example, theoretical work has predicted that LiH6 and NaH9 become particularly stable phases at about 100 and 25 GPa, respectively. And the potassium, rubidium and cesium polyhydrides all contain the H3-anion, the simplest exaple of a three centered four electron bond. The alkaline-earth polyhydrides are considered as well. Chemical trends relating the stabilization pressure to the ionization potential, and the nature of the hydrogenic sublattice to the strength of the metal-hydride interaction can be made. These hydrogen-rich materials with nontraditional stoichiometries are computed to undergo an insulator to metal transition at pressures attainable in diamond anvil cells. It may be that these systems are superconductors at experimentally achievable pressures. The metal-rich region of the alkali/hydrogen phase diagram under pressure shows that alkali-metal subhydrides may also be stabilized under pressure. We acknowledge the NSF (DMR-1005413) for financial support.

  7. N-alkyl pyrrolidone ether podands as versatile alkali metal ion chelants.

    PubMed

    Perrin, Andrea; Myers, Dominic; Fucke, Katharina; Musa, Osama M; Steed, Jonathan W

    2014-02-28

    This work explores the coordination chemistry of a bis(pyrrolidone) ether ligand. Pyrrolidones are commercially important functional groups because of the high polarity and hence high hydrophilicity and surface affinity. An array of alkali metal ion complexes of a podand bearing two pendant pyrrolidone functionalities, namely 1-{2-[2-(2-oxo-pyrrolid-1-yl)-ethoxy]-ethyl}-pyrrolid-2-one (1) are reported. Reaction of this ligand with sodium hexafluorophosphate gives two discrete species of formulae [Na(1)2]PF6 (3) and [Na3(H2O)2(μ-1)2](PF6)3 (4), and a coordination polymer {[Na3(μ3-1)3(μ2-1)](PF6)3}n (5). The same reaction in methanol gives a 1 : 1 complex, namely [Na2(μ-1)2(MeOH)2](PF6)2 (6). Use of tetraphenyl borate as a less coordinating counter ion gives [Na2(1)2(H2O)4](BPh4)2 (7) and [Na2(1)4](BPh4)2 (8). Two potassium complexes have also been isolated, a monomer [K(1)2]PF6 (9) and a cyclic tetramer [K4(μ4-H2O)2(μ-1)4](PF6)4 (10). The structures illustrate the highly polar nature of the amide carbonyl moiety within bis(pyrrolidone) ethers with longer interactions to the ether oxygen atom. The zinc complex is also reported and {[ZnCl2(μ-1)]}n (11) exhibits bonding only to the carbonyl moieties. The ether oxygen atom is not necessary for Na(+) complexation as exemplified by the structure of the sodium complex of the analogue 1,3-bis(pyrrolid-2-on-1-yl)butane (2). Reaction of compound 1 with lithium salts results in isolation of the protonated ligand. PMID:24336897

  8. Density Profiles of Liquid/Vapor Interfaces Away from Their Critical Points

    SciTech Connect

    Bu, Wei; Kim, Doseok; Vaknin, David

    2014-06-12

    We examine the applicability of various model profiles for the liquid/vapor interface by X-ray reflectivities on water and ethanol and their mixtures at room temperature. Analysis of the X-ray reflecivities using various density profiles shows an error-function like profile is the most adequate within experimental error. Our findings, together with recent observations from simulation studies on liquid surfaces, strongly suggest that the capillary-wave dynamics shapes the interfacial density profile in terms of the error function.

  9. Gas-phase silicon atom densities in the chemical vapor deposition of silicon from silane

    SciTech Connect

    Coltrin, M.E.; Breiland, W.G.; Ho, P.

    1993-12-31

    Silicon atom number density profiles have been measured using laser-induced fluorescence during the chemical vapor deposition of silicon from silane. Measurements were obtained in a rotating-disk reactor as a function of silane partial pressure and the amount of hydrogen added to the carrier gas. Absolute number densities were obtained using an atomic absorption technique. Results were compared with calculated density profiles from a model of the coupled fluid flow, gas-phase and surface chemistry for an infinite-radius rotating disk. An analysis of the reaction mechanism showed that the unimolecular decomposition of SiH{sub 2} is not the dominant source of Si atoms. Profile shapes and positions, and all experimental trends are well matched by the calculations. However, the calculated number density is up to 100 times smaller than measured.

  10. Alkali-Metal-Ion-Functionalized Graphene Oxide as a Superior Anode Material for Sodium-Ion Batteries.

    PubMed

    Wan, Fang; Li, Yu-Han; Liu, Dai-Huo; Guo, Jin-Zhi; Sun, Hai-Zhu; Zhang, Jing-Ping; Wu, Xing-Long

    2016-06-01

    Although graphene oxide (GO) has large interlayer spacing, it is still inappropriate to use it as an anode for sodium-ion batteries (SIBs) because of the existence of H-bonding between the layers and ultralow electrical conductivity which impedes the Na(+) and e(-) transformation. To solve these issues, chemical, thermal, and electrochemical procedures are traditionally employed to reduce GO nanosheets. However, these strategies are still unscalable, consume high amounts of energy, and are expensive for practical application. Here, for the first time, we describe the superior Na storage of unreduced GO by a simple and scalable alkali-metal-ion (Li(+) , Na(+) , K(+) )-functionalized process. The various alkali metals ions, connecting with the oxygen on GO, have played different effects on morphology, porosity, degree of disorder, and electrical conductivity, which are crucial for Na-storage capabilities. Electrochemical tests demonstrated that sodium-ion-functionalized GO (GNa) has shown outstanding Na-storage performance in terms of excellent rate capability and long-term cycle life (110 mAh g(-1) after 600 cycles at 1 A g(-1) ) owing to its high BET area, appropriate mesopore, high degree of disorder, and improved electrical conductivity. Theoretical calculations were performed using the generalized gradient approximation (GGA) to further study the Na-storage capabilities of functionalized GO. These calculations have indicated that the Na-O bond has the lowest binding energy, which is beneficial to insertion/extraction of the sodium ion, hence the GNa has shown the best Na-storage properties among all comparatives functionalized by other alkali metal ions. PMID:27136376

  11. Model analysis of ground-state dissociation energies and equilibrium separations in alkali-metal diatomic compounds

    NASA Astrophysics Data System (ADS)

    Lombardi, Erminio; Jansen, Laurens

    1986-05-01

    Ground-state dissociation energies De and equilibrium distances Re for the series of homonuclear alkali-metal diatomic molecules Li2,Na2,..., as well as those for six heteronuclear alkali-metal diatomic compounds, are evaluated on the basis of a simple valence-bond model. Each alkali-metal atom in a diatomic molecule is characterized by two quantities: a Gaussian parameter βe of the valence-electron function and a valence-to-core ``relative-size'' parameter γ≡(βc/βe)2, with βc the Gaussian parameter for the core-electron charge distribution. For the homonuclear diatomic molecules, accurate results are obtained with a 2s Gaussian valence function (r2-a2)G orthogonalized to the core. For each homonuclear diatomic molecule there exists an optimal (βe,γ) set yielding values of De and Re in practically quantitative agreement with experiment. The quantities βe and γ exhibit the expected physical behavior over the series in that βe decreases from Li2 to Cs2, and γ is highest for the lightest diatomic molecule Li2. The compounds K2, Rb2, and Cs2 are found to be ``Heitler-London'' molecules to within 5% of their binding energies. An approximate, similar, analysis of six heteronuclear diatomic compounds yields close agreement with experiment for LiNa and RbCs, whereas with the other four compounds (LiK, NaK, NaRb, and NaCs) the agreement with experimental De and Re is to within at most 5%. Also RbCs is a ``Heitler-London'' molecule to a very good approximation.

  12. Magnetic Slowing Down of Spin Relaxation due to Binary Collisions of Alkali-Metal Atoms with Buffer-Gas Atoms

    NASA Astrophysics Data System (ADS)

    Walter, D. K.; Griffith, W. M.; Happer, W.

    2002-03-01

    We report the first studies of magnetic decoupling of the spin relaxation of alkali-metal atoms due to binary collisions with buffer gases. When binary collisions are the dominant relaxation mechanism, the relaxation and its magnetic decoupling are well described by the S-damping rate ΓSD due to the spin-rotation interaction γN˙S, the spin exchange rate ΓEX for collisions between alkali atoms, and a new ``Carver rate'' ΓC, due to the pressure-shift interaction δAİS, which can substantially broaden the magnetic decoupling curve while having no influence on the zero-field rates.

  13. Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

    PubMed

    Aoki, Katsuyuki; Murayama, Kazutaka; Hu, Ning-Hai

    2016-01-01

    This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described. PMID:26860299

  14. Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions

    SciTech Connect

    Aymar, M.; Dulieu, O.; Guerout, R.

    2011-08-14

    The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.

  15. Collimated, single-pass atom source from a pulsed alkali metal dispenser for laser-cooling experiments

    SciTech Connect

    Moore, Kevin L.; Purdy, Thomas P.; Murch, Kater W.; Leslie, Sabrina; Gupta, Subhadeep; Stamper-Kurn, Dan M.

    2005-02-01

    We have developed an improved scheme for loading atoms into a magneto-optical trap (MOT) from a directed rubidium alkali metal dispenser in <10{sup -10} Torr ultrahigh vacuum conditions. A current-driven dispenser was surrounded with a cold absorbing 'shroud' held at {<=}0 deg. C, pumping rubidium atoms not directed into the MOT. This nearly eliminates background atoms and reduces the detrimental rise in pressure normally associated with these devices. The system can be well-described as a current-controlled, rapidly switched, two-temperature thermal beam, and was used to load a MOT with 3x10{sup 8} atoms.

  16. Sensitive determination of the spin polarization of optically pumped alkali-metal atoms using near-resonant light.

    PubMed

    Ding, Zhichao; Long, Xingwu; Yuan, Jie; Fan, Zhenfang; Luo, Hui

    2016-01-01

    A new method to measure the spin polarization of optically pumped alkali-metal atoms is demonstrated. Unlike the conventional method using far-detuned probe light, the near-resonant light with two specific frequencies was chosen. Because the Faraday rotation angle of this approach can be two orders of magnitude greater than that with the conventional method, this approach is more sensitive to the spin polarization. Based on the results of the experimental scheme, the spin polarization measurements are found to be in good agreement with the theoretical predictions, thereby demonstrating the feasibility of this approach. PMID:27595707

  17. Sensitive determination of the spin polarization of optically pumped alkali-metal atoms using near-resonant light

    PubMed Central

    Ding, Zhichao; Long, Xingwu; Yuan, Jie; Fan, Zhenfang; Luo, Hui

    2016-01-01

    A new method to measure the spin polarization of optically pumped alkali-metal atoms is demonstrated. Unlike the conventional method using far-detuned probe light, the near-resonant light with two specific frequencies was chosen. Because the Faraday rotation angle of this approach can be two orders of magnitude greater than that with the conventional method, this approach is more sensitive to the spin polarization. Based on the results of the experimental scheme, the spin polarization measurements are found to be in good agreement with the theoretical predictions, thereby demonstrating the feasibility of this approach. PMID:27595707

  18. Alkali Metal Ion Complexes with Phosphates, Nucleotides, Amino Acids, and Related Ligands of Biological Relevance. Their Properties in Solution.

    PubMed

    Crea, Francesco; De Stefano, Concetta; Foti, Claudia; Lando, Gabriele; Milea, Demetrio; Sammartano, Silvio

    2016-01-01

    Alkali metal ions play very important roles in all biological systems, some of them are essential for life. Their concentration depends on several physiological factors and is very variable. For example, sodium concentrations in human fluids vary from quite low (e.g., 8.2 mmol dm(-3) in mature maternal milk) to high values (0.14 mol dm(-3) in blood plasma). While many data on the concentration of Na(+) and K(+) in various fluids are available, the information on other alkali metal cations is scarce. Since many vital functions depend on the network of interactions occurring in various biofluids, this chapter reviews their complex formation with phosphates, nucleotides, amino acids, and related ligands of biological relevance. Literature data on this topic are quite rare if compared to other cations. Generally, the stability of alkali metal ion complexes of organic and inorganic ligands is rather low (usually log K < 2) and depends on the charge of the ligand, owing to the ionic nature of the interactions. At the same time, the size of the cation is an important factor that influences the stability: very often, but not always (e.g., for sulfate), it follows the trend Li(+) > Na(+) > K(+) > Rb(+) > Cs(+). For example, for citrate it is: log K ML = 0.88, 0.80, 0.48, 0.38, and 0.13 at 25 °C and infinite dilution. Some considerations are made on the main aspects related to the difficulties in the determination of weak complexes. The importance of the alkali metal ion complexes was also studied in the light of modelling natural fluids and in the use of these cations as probes for different processes. Some empirical relationships are proposed for the dependence of the stability constants of Na(+) complexes on the ligand charge, as well as for correlations among log K values of NaL, KL or LiL species (L = generic ligand). PMID:26860301

  19. Theoretical analysis of oxygen diffusion at startup in an alkali metal heat pipe with gettered alloy walls

    NASA Technical Reports Server (NTRS)

    Tower, L. K.

    1973-01-01

    The diffusion of oxygen into, or out of, a gettered alloy exposed to oxygenated alkali liquid metal coolant, a situation arising in some high temperature heat transfer systems, was analyzed. The relation between the diffusion process and the thermochemistry of oxygen in the alloy and in the alkali metal was developed by making several simplifying assumptions. The treatment is therefore theoretical in nature. However, a practical example pertaining to the startup of a heat pipe with walls of T-111, a tantalum alloy, and lithium working fluid illustrates the use of the figures contained in the analysis.

  20. AMTEC vapor-vapor series connected cells

    NASA Technical Reports Server (NTRS)

    Underwood, Mark L. (Inventor); Williams, Roger M. (Inventor); Ryan, Margaret A. (Inventor); Nakamura, Barbara J. (Inventor); Oconnor, Dennis E. (Inventor)

    1995-01-01

    An alkali metal thermoelectric converter (AMTEC) having a plurality of cells structurally connected in series to form a septum dividing a plenum into two chambers, and electrically connected in series, is provided with porous metal anodes and porous metal cathodes in the cells. The cells may be planar or annular, and in either case a metal alkali vapor at a high temperature is provided to the plenum through one chamber on one side of the wall and returned to a vapor boiler after condensation at a chamber on the other side of the wall in the plenum. If the cells are annular, a heating core may be placed along the axis of the stacked cells. This arrangement of series-connected cells allows efficient generation of power at high voltage and low current.

  1. Theoretical description of transverse measurements of polarization in optically-pumped Rb vapor cells

    NASA Astrophysics Data System (ADS)

    Dreiling, Joan; Tupa, Dale; Norrgard, Eric; Gay, Timothy

    2012-06-01

    In optical pumping of alkali-metal vapors, the polarization of the atoms is typically determined by probing along the entire length of the pumping beam, resulting in an averaged value of polarization over the length of the cell. Such measurements do not give any information about spatial variations of the polarization along the pump beam axis. Using a D1 probe beam oriented perpendicular to the pumping beam, we have demonstrated a heuristic method for determining the polarization along the pump beam's axis. Adapting a previously developed theory [1], we provide an analysis of the experiment which explains why this method works. The model includes the effects of Rb density, buffer gas pressure, and pump detuning. [4pt] [1] E.B. Norrgard, D. Tupa, J.M. Dreiling, and T.J. Gay, Phys. Rev. A 82, 033408 (2010).

  2. XPS studies and photocurrent applications of alkali-metals-doped ZnO nanoparticles under visible illumination conditions

    NASA Astrophysics Data System (ADS)

    Saáedi, Abdolhossein; Yousefi, Ramin; Jamali-Sheini, Farid; Zak, Ali Khorsand; Cheraghizade, Mohsen; Mahmoudian, M. R.; Baghchesara, Mohammad Amin; Dezaki, Abbas Shirmardi

    2016-05-01

    The present work is a study about a relationship between X-ray photoelectron spectrometer (XPS) results and photocurrent intensity of alkali-metals-elements doped ZnO nanoparticles, which is carried out under visible illumination conditions. The nanoparticles were synthesized by a simple sol-gel method. Structure and morphology studies of the NPs were carried out by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The effect of doping on the optical band-gap was investigated by using UV-visible spectrometer. The absorption peak of the doped ZnO NPs was red-shifted with respect to that of the undoped ZnO NPs. After that, the photocurrent application of the products was examined under a white light source at 2 V bias. The photocurrent results showed that, the current intensity of the ZnO NPs was increased by doping materials. However, K-doped ZnO NPs showed the highest photocurrent intensity. Finally, a discussion was carried out about the obtained photocurrent results by the O-1s spectra of the XPS of the samples. Our results suggest that the alkali-metals-doped ZnO NPs exhibit considerable promise for highly sensitive visible-light photodetectors.

  3. Influence of alkali metal cations on the thermal, mechanical and morphological properties of rectorite/chitosan bio-nanocomposite films.

    PubMed

    Babul Reddy, A; Jayaramudu, J; Siva Mohan Reddy, G; Manjula, B; Sadiku, E R

    2015-05-20

    The main theme of this work is to study the influence of ion-exchangeable alkali metal cations, such as: Li(+), Na(+), K(+), and Cs(+) on the thermal, mechanical and morphological properties. In this regard, a set of rectorite/chitosan (REC-CS) bio-nanocomposite films (BNCFs) was prepared by facile reaction of chitosan with ion-exchanged REC clay. The microstructure and morphology of BNCFs were investigated with XRD, TEM, SEM and AFM. Thermal and tensile properties of BNCFs were also investigated. As revealed from TEM and XRD results, the BNCFs featured a mixed morphology. Some intercalated clay sheets, together with nano-sized clay tactoids were obtained in LiREC/CS, NaREC/CS and KREC/CS of the BNCFs. From fractured surface study, via SEM, it was observed that the dispersion of chitosan polymer attaches to (and covers) the clay platelets. FTIR confirmed strong hydrogen bonds between clay and chitosan polymer. In addition, the thermal stabilities significantly varied when alkali metal cations varied from Li(+) to Cs(+). The BNCFs featured high tensile strengths (up to 84 MPa) and tensile moduli (up to 45 GPa). After evaluating these properties of BNCFs, we came to conclusion that these bio-nano composites can be used for packaging applications. PMID:25817663

  4. Structural and electronic engineering of 3DOM WO3 by alkali metal doping for improved NO2 sensing performance.

    PubMed

    Wang, Zhihua; Fan, Xiaoxiao; Han, Dongmei; Gu, Fubo

    2016-05-19

    Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and excellent selectivity. More importantly, the response of 3DOM WO3/Li to 500 ppb NO2 was up to 55 at room temperature (25 °C). The especially high response to ppb level NO2 at room temperature (25 °C) in this work has a very important practical significance. The best sensing performance of 3DOM WO3/Li could be ascribed to the most structure defects and the highest carrier mobility. And the possible gas sensing mechanism based on the model of the depletion layer was proposed to demonstrate that both structural and electronic properties are responsible for the NO2 sensing behavior. PMID:27109698

  5. Molecular origin of high free energy barriers for alkali metal ion transfer through ionic liquid-graphene electrode interfaces.

    PubMed

    Ivaništšev, Vladislav; Méndez-Morales, Trinidad; Lynden-Bell, Ruth M; Cabeza, Oscar; Gallego, Luis J; Varela, Luis M; Fedorov, Maxim V

    2016-01-14

    In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li(+) and K(+) at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li(+) in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li(+) than for K(+). The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested. PMID:26661060

  6. Universal scaling of potential energy functions describing intermolecular interactions. II. The halide-water and alkali metal-water interactions

    SciTech Connect

    Werhahn, Jasper C.; Akase, Dai; Xantheas, Sotiris S.

    2014-08-14

    The scaled versions of the newly introduced [S. S. Xantheas and J. C. Werhahn, J. Chem. Phys.141, 064117 (2014)] generalized forms of some popular potential energy functions (PEFs) describing intermolecular interactions – Mie, Lennard-Jones, Morse, and Buckingham exponential-6 – have been used to fit the ab initio relaxed approach paths and fixed approach paths for the halide-water, X-(H2O), X = F, Cl, Br, I, and alkali metal-water, M+(H2O), M = Li, Na, K, Rb, Cs, interactions. The generalized forms of those PEFs have an additional parameter with respect to the original forms and produce fits to the ab initio data that are between one and two orders of magnitude better in the χ2 than the original PEFs. They were found to describe both the long-range, minimum and repulsive wall of the respective potential energy surfaces quite accurately. Overall the 4-parameter extended Morse (eM) and generalized Buckingham exponential-6 (gBe-6) potentials were found to best fit the ab initio data for these two classes of ion-water interactions. Finally, the fitted values of the parameter of the (eM) and (gBe-6) PEFs that control the repulsive wall of the potential correlate remarkably well with the ionic radii of the halide and alkali metal ions.

  7. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    DOE PAGESBeta

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable groupmore » are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.« less

  8. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    SciTech Connect

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable group are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.

  9. Diffusion with chemical reaction: An attempt to explain number density anomalies in experiments involving alkali vapor

    NASA Technical Reports Server (NTRS)

    Snow, W. L.

    1974-01-01

    The mutual diffusion of two reacting gases is examined which takes place in a bath of inert gas atoms. Solutions are obtained between concentric spheres, each sphere acting as a source for one of the reactants. The calculational model is used to illustrate severe number density gradients observed in absorption experiments with alkali vapor. Severe gradients result when sq root k/D R is approximately 5 where k, D, and R are respectively the second order rate constant, the multicomponent diffusion constant, and the geometrical dimension of the experiment.

  10. Three Alkali-Metal-Gold-Gallium Systems. Ternary Tunnel Structures and Some Problems with Poorly Ordered Cations

    SciTech Connect

    Smetana, Volodymyr; Miller, Gordon J.; Corbett, John D.

    2012-06-27

    Six new intermetallic compounds have been characterized in the alkali metal (A = Na, Rb, Cs)–gold–gallium systems. Three isostructural compounds with the general composition A0.55Au2Ga2, two others of AAu3Ga2 (A = Rb, Cs), and the related Na13Au41.2Ga30.3 were synthesized via typical high-temperature reactions and their crystal structures determined by single-crystal X-ray diffraction analysis: Na0.56(9)Au2Ga2 (I, I4/mcm, a = 8.718(1) Å, c = 4.857(1) Å, Z = 4), Rb0.56(1)Au2Ga2 (II, I4/mcm, a = 8.950(1) Å, c = 4.829(1) Å, Z = 4), Cs0.54(2)Au2Ga2 (III, I4/mcm, a = 9.077(1) Å, c = 4.815(1) Å, Z = 4), RbAu3Ga2 (IV, Pnma, a = 13.384(3) Å, b = 5.577(1) Å, c = 7.017(1) Å, Z = 4), CsAu3Ga2 (V, Pnma, a = 13.511(3) Å, b = 5.614(2) Å, c = 7.146(1) Å, Z = 4), Na13Au41.2(1)Ga30.3(1) (VI, P6 mmm, a = 19.550(3) Å, c = 8.990(2) Å, Z = 2). The first three compounds (I–III) are isostructural with tetragonal K0.55Au2Ga2 and likewise contain planar eight-member Au/Ga rings that stack along c to generate tunnels and that contain varying degrees of disordered Na–Cs cations. The cation dispositions are much more clearly and reasonably defined by electron density mapping than through least-squares refinements with conventional anisotropic ellipsoids. Orthorhombic AAu3Ga2 (IV, V) are ordered ternary Rb and Cs derivatives of the SrZn5 type structure, demonstrating structural variability within the AAu3Ga2 family. All attempts to prepare an isotypic “NaAu3Ga2” were not successful, but yielded only a similar composition Na13Au41.2Ga30.3 (NaAu3.17Ga2.33) (VI) in a very different structure with two types of cation sites. Crystal orbital Hamilton population (COHP) analysis obtained from tight-binding electronic structure calculations for idealized I–IV via linear muffin-tin-orbital (LMTO) methods emphasized the major contributions of heteroatomic Au–Ga bonding to the structural stability of these compounds. The relative minima (pseudogaps) in the DOS curves for IV

  11. Use of alkali metal salts to prepare high purity single-walled carbon nanotube solutions and thin films

    NASA Astrophysics Data System (ADS)

    Ashour, Rakan F.

    Single-walled carbon nanotubes (SWCNTs) display interesting electronic and optical properties desired for many advanced thin film applications, such as transparent conductive electrodes or thin-film transistors. Large-scale production of SWCNTs generally results in polydispersed mixtures of nanotube structures. Since SWCNT electronic character (conducting or semiconducting nature) depends on the nanotube structure, application performance is being held back by this inability to discretely control SWCNT synthesis. Although a number of post-production techniques are able to separate SWCNTs based on electronic character, diameter, or chirality, most still suffer from the disadvantage of high costs of materials, equipment, or labor intensity to be relevant for large-scale production. On the other hand, chromatographic separation has emerged as a method that is compatible with large scale separation of metallic and semiconducting SWCNTs. In this work, SWCNTs, in an aqueous surfactant suspension of sodium dodecyl sulfate (SDS), are separated by their electronic character using a gel chromatography process. Metallic SWCNTs (m-SWCNTs) are collected as initial fractions since they show minimum interaction with the gel medium, whereas, semiconducting SWCNTs (sc- SWCNTs) remain adsorbed to the gel. The process of sc-SWCNT retention in the gel is found to be driven by the packing density of SDS around the SWCNTs. Through a series of separation experiments, it is shown that sc-SWCNTs can be eluted from the gel simply by disturbing the configuration of the SDS/SWCNT micellar structure. This is achieved by either introducing a solution containing a co-surfactant, such as sodium cholate (SC), or solutions of alkali metal ionic salts. Analysis of SWCNT suspensions by optical absorption provides insights into the effect of changing the metal ion (M+ = Li+, Na+, and K+) in the eluting solution. Salts with smaller metal ions (e.g. Li+) require higher concentrations to achieve

  12. Light-induced changes in an alkali metal atomic vapor cell coating studied by X-ray photoelectron spectroscopy

    SciTech Connect

    Hibberd, A. M.; Bernasek, S. L.; Seltzer, S. J.; Balabas, M. V.; Morse, M.; Budker, D.

    2013-09-07

    The light-induced desorption of Rb atoms from a paraffin coating is studied with depth-profiling X-ray photoelectron spectroscopy (XPS) using tunable synchrotron radiation. Following Rb exposure, shifts of the C1s signal to higher binding energies, as well as the appearance of lower binding energy components in the O1s region, were observed. These effects were diminished after irradiation with desorbing light. Additionally, following desorbing-light irradiation, changes in the depth-dependent concentration of carbon were observed. These observations offer an insight into the microscopic changes that occur during light-induced atomic desorption and demonstrate the utility of XPS in understanding atom-coating interactions.

  13. Column densities resulting from shuttle sublimator/evaporator operation. [optical density of nozzle flow containing water vapor

    NASA Technical Reports Server (NTRS)

    Naumann, R. J.

    1973-01-01

    The proposed disposal of H2O from the shuttle fuel cell operation by ejecting it in vapor form through a supersonic nozzle at the rate of 100 lb/day has been investigated from the point of view of the possible interference to astronomical experiments. If the nozzle is located at the tail and directed along the shuttle longitudinal axis, the resulting column density will be less than 10 to th 12th power molecules/sq cm at viewing angles larger than 48 deg above the longitudinal axis. The molecules in the trail will diffuse rapidly. The column density contribution from molecules expelled on the previous orbit is 1.3 x 10 to the 8th power molecules/sq cm. This contribution diminishes by the inverse square root of the number of orbits since the molecules were expelled. The molecular backscatter from atmospheric molecules is also calculated. If the plume is directed into the flight path, the column density along a perpendicular is found to be 1.5 x 10 to the 11th power molecules/sq cm. The return flux is estimated to be of the order of 10 to the 12th power molecules/sq cm/sec at the stagnation point. With reasonable care in design of experiments to protect them from the backscatter flux of water molecules, the expulsion of 100 lb/day does not appear to create an insurmountable difficulty for the shuttle experiments.

  14. Demonstration of a vapor density monitoring system using UV radiation generated from quasi-phasematched SHG waveguide devices

    SciTech Connect

    Galanti, S.A.; Berzins, L.V.; Brown, J.B.; Tamosaitis, R.S.; Bortz, M.L.; Day, T.; Fejer, M.M.; Wang, W.

    1996-01-29

    Many industrial applications require non-intrusive diagnostics for process monitoring and control. One example is the physical vapor deposition of titanium alloys. In this paper we present a system based on laser absorption spectroscopy for monitoring titanium vapor. Appropriate transitions for monitoring high rate vaporization of titanium require extension of available IR diode technology to the UV. The heart of this vapor density monitoring system is the 390nm radiation generated from quasi-phase matched interactions within periodically poled waveguides. In this paper, key system components of a UV laser absorption spectroscopy based system specific for titanium density monitoring are described. Analysis is presented showing the minimum power levels necessary from the ultraviolet laser source. Performance data for prototype systems using second harmonic generation (SHG) waveguide technology is presented. Application of this technology to other alloy density monitoring systems is discussed.

  15. Esr Spectra of Alkali-Metal Atoms on Helium Nanodroplets: a Theoretical Model for the Prediction of Helium Induced Hyperfine Structure Shifts

    NASA Astrophysics Data System (ADS)

    Hauser, Reas W.; Filatov, Michael; Ernst, Wolfgang E.

    2013-06-01

    We predict He-droplet-induced changes of the isotropic HFS constant a_{HFS} of the alkali-metal atoms M = Li, Na, K and Rb on the basis of a model description. Optically detected electron spin resonance spectroscopy has allowed high resolution measurements that show the influence of the helium droplet and its size on the unpaired electron spin density at the alkali nucleus. Our theoretical approach to describe this dependence is based on a combination of two well established techniques: Results of relativistic coupled-cluster calculations on the alkali-He dimers (energy and HFS constant as functions of the binding length) are mapped onto the doped-droplet-situation with the help of helium-density functional theory. We simulate doped droplets He_{N} with N ranging from 50 to 10000, using the diatomic alkali-He-potential energy curves as input. From the obtained density profiles we evaluate average distances between the dopant atom and its direct helium neighborhood. The distances are then set in relation to the variation of the HFS constant with binding length in the simplified alkali-He-dimer model picture. This method yields reliable relative shifts but involves a systematic absolute error. Hence, the absolute values of the shifts are tied to one experimentally determined HFS constant for ^{85}Rb-He_{N = 2000}. With this parameter choice we obtain results in good agreement with the available experimental data for Rb and K^{a,b} confirming the predicted 1/N trend of the functional dependence^{c}. M. Koch, G. Auböck, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 103, 035302-1-4 (2009) M. Koch, C. Callegari, and W. E. Ernst, Mol. Phys. 108 (7), 1005-1011 (2010) A. W. Hauser, T. Gruber, M. Filatov, and W. E. Ernst, ChemPhysChem (2013) online DOI: 10.1002/cphc.201200697

  16. Patterned growth of carbon nanotubes obtained by high density plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Mousinho, A. P.; Mansano, R. D.

    2015-03-01

    Patterned growth of carbon nanotubes by chemical vapor deposition represents an assembly approach to place and orient nanotubes at a stage as early as when they are synthesized. In this work, the carbon nanotubes were obtained at room temperature by High Density Plasmas Chemical Vapor Deposition (HDPCVD) system. This CVD system uses a new concept of plasma generation, where a planar coil coupled to an RF system for plasma generation was used with an electrostatic shield for plasma densification. In this mode, high density plasmas are obtained. We also report the patterned growth of carbon nanotubes on full 4-in Si wafers, using pure methane plasmas and iron as precursor material (seed). Photolithography processes were used to pattern the regions on the silicon wafers. The carbon nanotubes were characterized by micro-Raman spectroscopy, the spectra showed very single-walled carbon nanotubes axial vibration modes around 1590 cm-1 and radial breathing modes (RBM) around 120-400 cm-1, confirming that high quality of the carbon nanotubes obtained in this work. The carbon nanotubes were analyzed by atomic force microscopy and scanning electron microscopy too. The results showed that is possible obtain high-aligned carbon nanotubes with patterned growth on a silicon wafer with high reproducibility and control.

  17. Application of Molecular Dynamics Simulations in Molecular Property Prediction I: Density and Heat of Vaporization

    PubMed Central

    Wang, Junmei; Tingjun, Hou

    2011-01-01

    Molecular mechanical force field (FF) methods are useful in studying condensed phase properties. They are complementary to experiment and can often go beyond experiment in atomic details. Even a FF is specific for studying structures, dynamics and functions of biomolecules, it is still important for the FF to accurately reproduce the experimental liquid properties of small molecules that represent the chemical moieties of biomolecules. Otherwise, the force field may not describe the structures and energies of macromolecules in aqueous solutions properly. In this work, we have carried out a systematic study to evaluate the General AMBER Force Field (GAFF) in studying densities and heats of vaporization for a large set of organic molecules that covers the most common chemical functional groups. The latest techniques, such as the particle mesh Ewald (PME) for calculating electrostatic energies, and Langevin dynamics for scaling temperatures, have been applied in the molecular dynamics (MD) simulations. For density, the average percent error (APE) of 71 organic compounds is 4.43% when compared to the experimental values. More encouragingly, the APE drops to 3.43% after the exclusion of two outliers and four other compounds for which the experimental densities have been measured with pressures higher than 1.0 atm. For heat of vaporization, several protocols have been investigated and the best one, P4/ntt0, achieves an average unsigned error (AUE) and a root-mean-square error (RMSE) of 0.93 and 1.20 kcal/mol, respectively. How to reduce the prediction errors through proper van der Waals (vdW) parameterization has been discussed. An encouraging finding in vdW parameterization is that both densities and heats of vaporization approach their “ideal” values in a synchronous fashion when vdW parameters are tuned. The following hydration free energy calculation using thermodynamic integration further justifies the vdW refinement. We conclude that simple vdW parameterization

  18. Spin Relaxation Resonances due to the Spin-Axis Interaction in Dense Rubidium and Cesium Vapor

    NASA Astrophysics Data System (ADS)

    Erickson, C. J.; Levron, D.; Happer, W.; Kadlecek, S.; Chann, B.; Anderson, L. W.; Walker, T. G.

    2000-11-01

    Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers (likely accurate to a factor of 2) are \\|λ\\|/h = 290 MHz for Rb; 2500 MHz for Cs.

  19. Design of a vapor-liquid-equilibrium, surface tension, and density apparatus

    SciTech Connect

    Holcomb, C.D.; Outcalt, S.L.

    1997-12-31

    The design and performance of a unique vapor-liquid equilibrium (VLE) apparatus with density and surface tension capabilities is presented. The apparatus operates at temperatures ranging from 218 to 423 K, at pressures to 17 MPa, at densities to 1100 kg/m{sup 3}, and at surface tensions ranging from 0.1 to 75 mN/m. Temperatures are measured with a precision of {+-}0.02 K, pressures with a precision of {+-}0.1% of full scale, densities with a precision of {+-}0.5 kg/m{sup 3}, surface tensions with a precision of {+-}0.2 mN/m, and compositions with a precision of {+-}0.005 mole fraction. The apparatus is designed to be both accurate and versatile. Capabilities include: (1) the ability to operate the apparatus as a bubble point pressure or an isothermal pressure-volume-temperature (PVT) apparatus, (2) the ability to measure densities and surface tensions of the coexisting phases, and (3) the ability for either trapped or capillary sampling. We can validate our VLE and density data by measuring PVT or bubble point pressures in the apparatus. The use of the apparatus for measurements of VLE, densities, and surface tensions over wide ranges of temperature and pressure is important in equation of state and transport property model development. The use of different sampling procedures allows measurement of a wider variety of fluid mixtures. VLE measurements on the alternative refrigerant system R32/134a are presented and compared to literature results to verify the performance of the apparatus.

  20. Third order nonlinear optical properties and optical limiting behavior of alkali metal complexes of p-nitrophenol

    NASA Astrophysics Data System (ADS)

    Thangaraj, M.; Vinitha, G.; Sabari Girisun, T. C.; Anandan, P.; Ravi, G.

    2015-10-01

    Optical nonlinearity of metal complexes of p-nitrophenolate (M=Li, Na and K) in ethanol is studied by using a continuous wave (cw) diode pumped Nd:YAG laser (532 nm, 50 mW). The predominant mechanism of observed nonlinearity is thermal in origin. The nonlinear refractive index and the nonlinear absorption coefficient of the samples were found to be in the order of 10-8 cm2/W and 10-3 cm/W respectively. Magnitude of third-order optical parameters varies according to the choice of alkali metal chosen for metal complex formation of p-nitrophenolate. The third-order nonlinear susceptibility was found to be in the order of 10-6 esu. The observed saturable absorption and the self-defocusing effect were used to demonstrate the optical limiting action at 532 nm by using the same cw laser beam.

  1. Crown-Ether Derived Graphene Hybrid Composite for Membrane-Free Potentiometric Sensing of Alkali Metal Ions.

    PubMed

    Olsen, Gunnar; Ulstrup, Jens; Chi, Qijin

    2016-01-13

    We report the design and synthesis of newly functionalized graphene hybrid material that can be used for selective membrane-free potentiometric detection of alkali metal ions, represented by potassium ions. Reduced graphene oxide (RGO) functionalized covalently by 18-crown[6] ether with a dense surface coverage is achieved by the introduction of a flexible linking molecule. The resulting hybrid composite is highly stable and is capable of detecting potassium ions down to micromolar ranges with a selectivity over other cations (including Ca(2+), Li(+), Na(+), NH4(+)) at concentrations up to 25 mM. This material can be combined further with disposable chips, demonstrating its promise as an effective ion-selective sensing component for practical applications. PMID:26703780

  2. Hyperfine-induced quadrupole moments of alkali-metal-atom ground states and their implications for atomic clocks

    NASA Astrophysics Data System (ADS)

    Derevianko, Andrei

    2016-01-01

    Spherically symmetric ground states of alkali-metal atoms do not posses electric quadrupole moments. However, the hyperfine interaction between nuclear moments and atomic electrons distorts the spherical symmetry of electronic clouds and leads to nonvanishing atomic quadrupole moments. We evaluate these hyperfine-induced quadrupole moments using techniques of relativistic many-body theory and compile results for Li, Na, K, Rb, and Cs atoms. For heavy atoms we find that the hyperfine-induced quadrupole moments are strongly (two orders of magnitude) enhanced by correlation effects. We further apply the results of the calculation to microwave atomic clocks where the coupling of atomic quadrupole moments to gradients of electric fields leads to clock frequency uncertainties. We show that for 133Cs atomic clocks, the spatial gradients of electric fields must be smaller than 30 V /cm2 to guarantee fractional inaccuracies below 10-16.

  3. Structural and electronic engineering of 3DOM WO3 by alkali metal doping for improved NO2 sensing performance

    NASA Astrophysics Data System (ADS)

    Wang, Zhihua; Fan, Xiaoxiao; Han, Dongmei; Gu, Fubo

    2016-05-01

    Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and excellent selectivity. More importantly, the response of 3DOM WO3/Li to 500 ppb NO2 was up to 55 at room temperature (25 °C). The especially high response to ppb level NO2 at room temperature (25 °C) in this work has a very important practical significance. The best sensing performance of 3DOM WO3/Li could be ascribed to the most structure defects and the highest carrier mobility. And the possible gas sensing mechanism based on the model of the depletion layer was proposed to demonstrate that both structural and electronic properties are responsible for the NO2 sensing behavior.Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and

  4. Alkali Metal Halide Salts as Interface Additives to Fabricate Hysteresis-Free Hybrid Perovskite-Based Photovoltaic Devices.

    PubMed

    Wang, Lili; Moghe, Dhanashree; Hafezian, Soroush; Chen, Pei; Young, Margaret; Elinski, Mark; Martinu, Ludvik; Kéna-Cohen, Stéphane; Lunt, Richard R

    2016-09-01

    A new method was developed for doping and fabricating hysteresis-free hybrid perovskite-based photovoltaic devices by using alkali metal halide salts as interface layer additives. Such salt layers introduced at the perovskite interface can provide excessive halide ions to fill vacancies formed during the deposition and annealing process. A range of solution-processed halide salts were investigated. The highest performance of methylammonium lead mixed-halide perovskite device was achieved with a NaI interlayer and showed a power conversion efficiency of 12.6% and a hysteresis of less than 2%. This represents a 90% improvement compared to control devices without this salt layer. Through depth-resolved mass spectrometry, optical modeling, and photoluminescence spectroscopy, this enhancement is attributed to the reduction of iodide vacancies, passivation of grain boundaries, and improved hole extraction. Our approach ultimately provides an alternative and facile route to high-performance and hysteresis-free perovskite solar cells. PMID:27532662

  5. Alkali metal salts of rutin - Synthesis, spectroscopic (FT-IR, FT-Raman, UV-VIS), antioxidant and antimicrobial studies.

    PubMed

    Samsonowicz, M; Kamińska, I; Kalinowska, M; Lewandowski, W

    2015-12-01

    In this work several metal salts of rutin with lithium, sodium, potassium, rubidium and cesium were synthesized. Their molecular structures were discussed on the basis of spectroscopic (FT-IR, FT-Raman, UV-VIS) studies. Optimized geometrical structure of rutin was calculated by B3LYP/6-311++G(∗∗) method and sodium salt of rutin were calculated by B3LYP/LanL2DZ method. Metal chelation change the biological properties of ligand therefore the antioxidant (FRAP and DPPH) and antimicrobial activities (toward Escherichia coli, Staphylococcus aureus, Enterococcus faecium, Proteus vulgaris, Pseudomonas aeruginosa, Klebsiella pneumonia, Candida albicans and Saccharomyces cerevisiae) of alkali metal salts were evaluated and compared with the biological properties of rutin. PMID:26184478

  6. Synthesis and X-ray Characterization of Alkali Metal 2-Acyl-1,1,3,3-tetracyanopropenides.

    PubMed

    Karpov, Sergey V; Grigor'ev, Arthur A; Kayukov, Yakov S; Karpova, Irina V; Nasakin, Oleg E; Tafeenko, Victor A

    2016-08-01

    A novel route for synthesis of 2-acyl-1,1,3,3-tetracyanopropenides (ATCN) salts in high yields and excellent purities starting from readily available methyl ketones, malononitrile, bromine, and alkali metal acetates is reported. The starting aryl(heteroaryl) methyl ketones were oxidized to the corresponding α-ketoaldehydes by new a DMSO-NaBr-H2SO4 oxidation system in yields up to 90% within a short reaction time of 8-10 min. The subsequent stages of ATCN preparation are realized in aqueous media without use of any toxic solvents, in accordance with principle 5 of "green chemistry". Lithium, sodium, potassium, rubidium, and cesium 2-benzoyl-1,1,3,3-tetracyanopropenides were characterized by X-ray diffraction analysis. These salts show a good potential for synthesis of five- and six-membered heterocycles and may serve as potentially useful ligands in coordination and supramolecular chemistry. PMID:27384963

  7. One- and two-photon spectroscopy of highly excited states of alkali-metal atoms on helium nanodroplets

    SciTech Connect

    Pifrader, Alexandra; Allard, Olivier; Auboeck, Gerald; Callegari, Carlo; Ernst, Wolfgang E.; Huber, Robert; Ancilotto, Francesco

    2010-10-28

    Alkali-metal atoms captured on the surface of superfluid helium droplets are excited to high energies ({approx_equal}3 eV) by means of pulsed lasers, and their laser-induced-fluorescence spectra are recorded. We report on the one-photon excitation of the (n+1)p(leftarrow)ns transition of K, Rb, and Cs (n=4, 5, and 6, respectively) and on the two-photon one-color excitation of the 5d(leftarrow)5s transition of Rb. Gated-photon-counting measurements are consistent with the relaxation rates of the bare atoms, hence consistent with the reasonable expectation that atoms quickly desorb from the droplet and droplet-induced relaxation need not be invoked.

  8. Dispersion coefficients for H and He interactions with alkali-metal and alkaline-earth-metal atoms

    SciTech Connect

    Mitroy, J.; Bromley, M.W.J.

    2003-12-01

    The van der Waals coefficients C{sub 6}, C{sub 8}, and C{sub 10} for H and He interactions with the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are determined from oscillator strength sum rules. The oscillator strengths were computed using a combination of ab initio and semiempirical methods. The dispersion parameters generally agree with close to exact variational calculations for Li-H and Li-He at the 0.1% level of accuracy. For larger systems, there is agreement with relativistic many-body perturbation theory estimates of C{sub 6} at the 1% level. These validations for selected systems attest to the reliability of the present dispersion parameters. About half the present parameters lie within the recommended bounds of the Standard and Certain compilation [J. Chem. Phys. 83, 3002 (1985)].

  9. Highly sensitive sensors for alkali metal ions based on complementary-metal-oxide-semiconductor-compatible silicon nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Jun; Agarwal, Ajay; Buddharaju, Kavitha D.; Singh, Navab; Gao, Zhiqiang

    2007-06-01

    Highly sensitive sensors for alkali metal ions based on complementary-metal-oxide- semiconductor-compatible silicon nanowires (SiNWs) with crown ethers covalently immobilized on their surface are presented. A densely packed organic monolayer terminated with amine groups is introduced to the SiNW surface via hydrosilylation. Amine-modified crown ethers, acting as sensing elements, are then immobilized onto the SiNWs through a cross-linking reaction with the monolayer. The crown ether-functionalized SiNWs recognize Na+ and K+ according to their complexation ability to the crown ethers. The SiNW sensors are highly selective and capable of achieving an ultralow detection limit down to 50nM, over three orders of magnitude lower than that of conventional crown ether-based ion-selective electrodes.

  10. Development of processes for the production of solar grade silicon from halides and alkali metals, phase 1 and phase 2

    NASA Technical Reports Server (NTRS)

    Dickson, C. R.; Gould, R. K.; Felder, W.

    1981-01-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon are described. Product separation and collection processes were evaluated, measure heat release parameters for scaling purposes and effects of reactants and/or products on materials of reactor construction were determined, and preliminary engineering and economic analysis of a scaled up process were made. The feasibility of the basic process to make and collect silicon was demonstrated. The jet impaction/separation process was demonstrated to be a purification process. The rate at which gas phase species from silicon particle precursors, the time required for silane decomposition to produce particles, and the competing rate of growth of silicon seed particles injected into a decomposing silane environment were determined. The extent of silane decomposition as a function of residence time, temperature, and pressure was measured by infrared absorption spectroscopy. A simplistic model is presented to explain the growth of silicon in a decomposing silane enviroment.

  11. Modeling insights into the locations of density enhancements from the Enceladus water vapor jets

    NASA Astrophysics Data System (ADS)

    Hurley, Dana M.; Perry, Mark E.; Waite, J. Hunter

    2015-11-01

    Monte Carlo modeling of the vapor erupting from Enceladus' south polar region is presented to demonstrate the influence of physical characteristics of the emitted vapor on the distribution of particles at altitude. The modeled sources include localized jets and eruptions distributed along the surface features labeled "tiger stripes." The modeling reveals that density enhancements are displaced from the source location caused not only by the angle of emission but also by superposition of material from nearby sources. The altitude of the superposition is mass dependent and contributes to differences observed in the mass 28 and mass 44 channels of the Cassini Ion and Neutral Mass Spectrometer (INMS) during Enceladus encounters. INMS data are well modeled using only the tiger stripe sources; however, certain regions require additional sources to reproduce some features of the data. In particular, an excess source is required for 44 unified atomic mass unit (u) on the Saturn-facing hemisphere of Baghdad Sulcus. It is apparent in three parallel Cassini flybys. A relative decrease in the source rate is observed for mass 28 u for E14. The more diffuse nature of the 28 u INMS observations compared to the more collimated structure of the 44 u INMS observations is consistent with increased thermal spreading for low-mass constituents of the plume.

  12. Estimates of the relative magnitudes of the isotropic and anisotropic magnetic-dipole hyperfine interactions in alkali-metal-noble-gas systems

    NASA Astrophysics Data System (ADS)

    Walter, D. K.; Happer, W.; Walker, T. G.

    1998-11-01

    We present a detailed theoretical analysis of the noble-gas nuclear-spin relaxation due to the anisotropic magnetic-dipole hyperfine interaction between the noble-gas nucleus and alkali-metal valence electron vis à vis the already well-understood (spin-conserving) isotropic magnetic-dipole hyperfine interaction in alkali-metal-noble-gas systems. We find that, for all pairs in which the noble gas is not helium, the predicted spin-relaxation rate from the anisotropic interaction does not exceed 2.5% of the rate from the isotropic interaction, thereby not appreciably limiting the maximum noble-gas nuclear polarization attainable via spin-exchange collisions with polarized alkali-metal atoms. For alkali-metal-helium pairs, we predict that the anisotropic interaction has a slightly larger relative effect, perhaps limiting the nuclear polarization to ~95% of the electronic polarization in the Rb-3He system; however, our confidence in the helium results is limited by a lack of knowledge of the interatomic potentials necessary for the calculation.

  13. MS/MS and LC-MS/MS analysis of choline/ethanolamine plasmalogens via promotion of alkali metal adduct formation.

    PubMed

    Otoki, Yurika; Nakagawa, Kiyotaka; Kato, Shunji; Miyazawa, Teruo

    2015-11-01

    Tandem mass spectrometry (MS/MS) has been used for the analysis of plasmalogen (Pls), a physiologically important class of vinyl ether-linked phospholipid. However, MS/MS generally causes little fragmentation of Pls, especially choline Pls (PC-Pls). Previous MS/MS studies reported an increased formation of product ions of PC-Pls (and also ethanolamine Pls (PE-Pls)) in the presence of 'alkali metals.' Therefore, use of alkali metals considerably leads to the development of a method for analysis of both PC- and PE-Pls. In this study, this notion was evaluated using quadrupole-time-of-flight MS/MS and liquid chromatography (LC) coupled with MS/MS. Results from MS/MS confirmed that alkali metals (e.g., sodium) produced significant fragmentation of PC-Pls and PE-Pls. A number of structure-diagnostic product ions exhibiting high intensities were observed under optimized MS/MS conditions using alkali metals. Moreover, the ability to selectively and sensitively identify PC-Pls and PE-Pls at the molecular species level in biological samples (rat brain and heart) was demonstrated using LC-MS/MS. Therefore, the herein developed method appears to be a powerful tool for analyzing Pls and may provide a better understanding of their physiological roles in vivo. PMID:26447938

  14. A series of new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems.

    PubMed

    Gu, Qian-Hua; Hu, Chun-Li; Zhang, Jian-Han; Mao, Jiang-Gao

    2011-03-21

    Six new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems have been prepared by solid-state reactions at high-temperatures. Their structures were determined by single-crystal X-ray diffraction studies. AM(3)O(6)(QO(3))(2) (A = K, Rb, M = Nb, Ta, Q = Te; A = K, M = Nb, Q = Se) are isomorphous and their structures feature a 3D network with 1D 4- and 6-MRs tunnels along the a-axis which is composed of 2D layers of corner-sharing MO(6) octahedra bridged by QO(3) groups. The alkali metal ions are located at the above 1D tunnels of 6-MRs. The structure of Cs(3)Nb(9)O(18)(TeO(3))(2)(TeO(4))(2) features a thick Nb-Te-O layer built of corner-sharing NbO(6) octahedra, TeO(3) and TeO(4) groups. The 2D layer of the NbO(6) octahedra with 1D tunnels of 6-MRs along the c-axis are formed by 1D chains of NbO(6) chains along the c-axis and linear Nb(4)O(21) tetramers by corner-sharing. The TeO(3) and TeO(4) groups are grafted on both sides of the niobium-oxide layer via Nb-O-Te or/and Te-O-Te bridges. The caesium(i) ions are located at the above 1D tunnels of 6-MRs. TGA, UV-vis and infrared spectral measurements as well as electronic structure calculations have also been performed. PMID:21293821

  15. Transition rates for lithium-like ions, sodium-like ions, and neutral alkali-metal atoms

    SciTech Connect

    Johnson, W.R.; Liu, Z.W.; Sapirstein, J.

    1996-11-01

    Third-order many-body perturbation theory is used to obtain E1 transition amplitudes for ions of the lithium and sodium isoelectronic sequences and for the neutral alkali-metal atoms potassium, rubidium, cesium, and francium. Complete angular reductions of the first, second, and third-order amplitudes are given. Tables of transition energies and rates are given for the 2p{sub {1/2}} {yields} 2s{sub {1/2}}, 2p{sub 3/2} {yields} 2s{sub {1/2}}, 3s{sub {1/2}} {yields} 2p{sub {1/2}}, and 3s{sub {1/2}} {yields} 2p{sub 3/2} transitions in the lithium isoelectronic sequence and for the corresponding 3p{sub 1/2} {yields} 3s{sub 1/2}, 3p{sub 3/2} {yields} 3s{sub {1/2}}, 4s{sub {1/2}} {yields} 3p{sub 1/2}, and 4s{sub {1/2}} {yields} 3p{sub 3/2} transitions in the sodium sequence. For neutral alkali atoms, amplitudes of np{sub {1/2}} {yields} ns{sub {1/2}}, np{sub 3/2} {yields} ns{sub {1/2}}, (n + 1)s{sub {1/2}} {yields} np{sub {1/2}}, and (n + 1)s{sub {1/2}} {yields} np{sub 3/2} transitions are evaluated, where n is the principal quantum number of the valence electron in the atomic ground state, Semi-empirical corrections for the omitted fourth- and higher-order terms in perturbation theory are given for the neutral alkali-metal atoms. Comparisons with previous high-precision calculations and with experiment are made. 42 refs., 1 fig., 12 tabs.

  16. Relativistic many-body investigation of hyperfine interactions in excited S states of alkali metals: Francium and potassium

    SciTech Connect

    Owusu, A.; Dougherty, R.W.; Gowri, G.; Das, T.P.; Andriessen, J.

    1997-07-01

    To enhance the current understanding of mechanisms contributing to magnetic hyperfine interactions in excited states of atomic systems, in particular, alkali-metal atom systems, the hyperfine fields in the excited 5{sup 2}S{sub 1/2}{endash}8{sup 2}S{sub 1/2} states of potassium and 8{sup 2}S{sub 1/2}{endash}12{sup 2}S{sub 1/2} states of francium atoms have been studied using the relativistic linked-cluster many-body perturbation procedure. The net theoretical values of the hyperfine fields for the excited states studied are in excellent agreement with available experimental data for both atoms. There is a significant decrease in importance of the correlation contribution in going from the ground state to the excited states, the correlation contributions as ratios of the direct contribution decreasing rapidly as one moves to the higher excited states. However, the contribution from the exchange core polarization (ECP) effect is nearly a constant fraction of the direct effect for all the excited states considered. Physical explanations are offered for the observed trends in the contributions from the different mechanisms. A comparison is made of the different contributing effects to the hyperfine fields in potassium and francium to those in the related system, rubidium, studied earlier. Extrapolating from our results to the highly excited states of alkali-metal atoms, referred to as the Rydberg states, it is concluded that in addition to the direct contribution from the excited valence electron to the hyperfine fields, a significant contribution is expected from the ECP effect arising from the influence of exchange interactions between electrons in the valence and core states. {copyright} {ital 1997} {ital The American Physical Society}

  17. Density Relaxation of Liquid-Vapor Critical Fluids Examined in Earth's Gravity

    NASA Technical Reports Server (NTRS)

    Wilkinson, R. Allen

    2000-01-01

    This work shows quantitatively the pronounced differences between the density equilibration of very compressible dense fluids in Earth's gravity and those in microgravity. The work was performed onsite at the NASA Glenn Research Center at Lewis Field and is complete. Full details are given in references 1 and 2. Liquid-vapor critical fluids (e.g., water) at their critical temperature and pressure, are very compressible. They collapse under their own weight in Earth's gravity, allowing only a thin meniscus-like layer with the critical pressure to survive. This critical layer, however, greatly slows down the equilibration process of the entire sample. A complicating feature is the buoyancy-driven slow flows of layers of heavier and lighter fluid. This work highlights the incomplete understanding of the hydrodynamics involved in these fluids.

  18. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼10{sup 17} cm{sup −3} to (2–5) × 10{sup 14} cm{sup −3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5 × 10{sup 13} cm{sup −3} versus 2.9 × 10{sup 16} cm{sup −3} in the standard samples, with a similar decrease in the electron traps concentration.

  19. Competition between pi and non-pi cation-binding sites in aromatic amino acids: a theoretical study of alkali metal cation (Li+, Na+, K+)-phenylalanine complexes.

    PubMed

    Siu, Fung Ming; Ma, Ngai Ling; Tsang, Chun Wai

    2004-04-19

    To understand the cation-pi interaction in aromatic amino acids and peptides, the binding of M(+) (where M(+) = Li(+), Na(+), and K(+)) to phenylalanine (Phe) is studied at the best level of density functional theory reported so far. The different modes of M(+) binding show the same order of binding affinity (Li(+)>Na(+)>K(+)), in the approximate ratio of 2.2:1.5:1.0. The most stable binding mode is one in which the M(+) is stabilized by a tridentate interaction between the cation and the carbonyl oxygen (O[double bond]C), amino nitrogen (--NH(2)), and aromatic pi ring; the absolute Li(+), Na(+), and K(+) affinities are estimated theoretically to be 275, 201, and 141 kJ mol(-1), respectively. Factors affecting the relative stabilities of various M(+)-Phe binding modes and conformers have been identified, with ion-dipole interaction playing an important role. We found that the trend of pi and non-pi cation bonding distances (Na(+)-pi>Na(+)-N>Na(+)-O and K(+)-pi>K(+)-N>K(+)-O) in our theoretical Na(+)/K(+)-Phe structures are in agreement with the reported X-ray crystal structures of model synthetic receptors (sodium and potassium bound lariat ether complexes), even though the average alkali metal cation-pi distance found in the crystal structures is longer. This difference between the solid and the gas-phase structures can be reconciled by taking the higher coordination number of the cations in the lariat ether complexes into account. PMID:15079836

  20. Critical points of metal vapors

    SciTech Connect

    Khomkin, A. L. Shumikhin, A. S.

    2015-09-15

    A new method is proposed for calculating the parameters of critical points and binodals for the vapor–liquid (insulator–metal) phase transition in vapors of metals with multielectron valence shells. The method is based on a model developed earlier for the vapors of alkali metals, atomic hydrogen, and exciton gas, proceeding from the assumption that the cohesion determining the basic characteristics of metals under normal conditions is also responsible for their properties in the vicinity of the critical point. It is proposed to calculate the cohesion of multielectron atoms using well-known scaling relations for the binding energy, which are constructed for most metals in the periodic table by processing the results of many numerical calculations. The adopted model allows the parameters of critical points and binodals for the vapor–liquid phase transition in metal vapors to be calculated using published data on the properties of metals under normal conditions. The parameters of critical points have been calculated for a large number of metals and show satisfactory agreement with experimental data for alkali metals and with available estimates for all other metals. Binodals of metals have been calculated for the first time.

  1. Vapor phase crystallization in Apollo 14 breccia.

    NASA Technical Reports Server (NTRS)

    Mckay, D. S.; Clanton, U. S.; Morrison, D. A.; Ladle, G. H.

    1972-01-01

    The vugs contained in many of the highly recrystallized breccias from Apollo 14 are discussed, along with the well-developed crystals of plagioclase, pyroxene, ilmenite, apatite, whitlockite, iron, nickel-iron, and troilite that extend from the vug walls and bridge open spaces. These crystals are interpreted as having formed by deposition from a hot vapor containing oxides, halides, sulfides, alkali metals, iron and possibly other chemical species. The hot vapor was associated with the thermal metamorphism and subsequent cooling of the Fra Mauro formation after it had been deposited as an ejecta blanket by the Imbrian impact.

  2. Method for the generation of variable density metal vapors which bypasses the liquidus phase

    DOEpatents

    Kunnmann, Walter; Larese, John Z.

    2001-01-01

    The present invention provides a method for producing a metal vapor that includes the steps of combining a metal and graphite in a vessel to form a mixture; heating the mixture to a first temperature in an argon gas atmosphere to form a metal carbide; maintaining the first temperature for a period of time; heating the metal carbide to a second temperature to form a metal vapor; withdrawing the metal vapor and the argon gas from the vessel; and separating the metal vapor from the argon gas. Metal vapors made using this method can be used to produce uniform powders of the metal oxide that have narrow size distribution and high purity.

  3. Photosynthetic photon flux density, carbon dioxide concentration, and vapor pressure deficit effects on photosynthesis in cacao seedlings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cacao (Theobroma cacao) is a shade plant, native to the under-story of the evergreen rain forest of the Amazon basin and adapted to low levels of photosynthetic photon flux density (PPFD). The influence of PPFD, leaf to air water vapor pressure deficit (VPD) and external carbon dioxide concentration...

  4. Alkali-metal-atom polarization imaging in high-pressure optical-pumping cells

    NASA Astrophysics Data System (ADS)

    Baranga, A. Ben-Amar; Appelt, S.; Erickson, C. J.; Young, A. R.; Happer, W.

    1998-09-01

    We present a detailed experimental analysis of Rb-polarization imaging in high-pressure gas cells. The Rb vapor in these cells is optically pumped by high-power diode-laser arrays. We present images for high (35 G) and low (4 G) magnetic fields and for different He and Xe buffer-gas mixtures. We demonstrate that high-field imaging provides an absolute measurement of the Rb-polarization distribution in the cell, based on the fact that a spin-temperature distribution of the hyperfine magnetic sublevels is established in high-pressure buffer gases. A survey of various mechanisms that broaden the Rb magnetic-resonance lines is presented. These broadening mechanisms determine the limits of the spatial resolution achievable for images of the Rb-polarization distribution.

  5. Alkali metal Rankine cycle boiler technology challenges and some potential solutions for space nuclear power and propulsion applications

    NASA Astrophysics Data System (ADS)

    Stone, James R.

    1994-07-01

    Alkali metal boilers are of interest for application to future space Rankine cycle power conversion systems. Significant progress on such boilers was accomplished in the 1960's and early 1970's, but development was not continued to operational systems since NASA's plans for future space missions were drastically curtailed in the early 1970's. In particular, piloted Mars missions were indefinitely deferred. With the announcement of the Space Exploration Initiative (SEI) in July 1989 by President Bush, interest was rekindled in challenging space missions and, consequently in space nuclear power and propulsion. Nuclear electric propulsion (NEP) and nuclear thermal propulsion (NTP) were proposed for interplanetary space vehicles, particularly for Mars missions. The potassium Rankine power conversion cycle became of interest to provide electric power for NEP vehicles and for 'dual-mode' NTP vehicles, where the same reactor could be used directly for propulsion and (with an additional coolant loop) for power. Although the boiler is not a major contributor to system mass, it is of critical importance because of its interaction with the rest of the power conversion system; it can cause problems for other components such as excess liquid droplets entering the turbine, thereby reducing its life, or more critically, it can drive instabilities-some severe enough to cause system failure. Funding for the SEI and its associated technology program from 1990 to 1993 was not sufficient to support significant new work on Rankine cycle boilers for space applications. In Fiscal Year 1994, funding for these challenging missions and technologies has again been curtailed, and planning for the future is very uncertain. The purpose of this paper is to review the technologies developed in the 1960's and 1970's in the light of the recent SEI applications. In this way, future Rankine cycle boiler programs may be conducted most efficiently. This report is aimed at evaluating alkali metal boiler

  6. Use the superconducting proximity effect to investigate alkali metal films and the comparison between the experiment and theory

    NASA Astrophysics Data System (ADS)

    Zhang, Manjiang

    Bilayers of Pb and the alkali metals Cs, Rb, K and Na were quench condensed on the quartz plate. The transition temperature measurement provides information about interface barriers between the Pb and the alkali metals. Such a barrier, which is not due to impurities or oxidation, is particularly large in Pb/Cs sandwiches. The thin K film is forced into an insulating state by being covered with sub-monolayers of Pb. The SPE is used to investigate the electronic change in the alkali film. The K film behaves as if its electrons are unable to carry a current in the x-y-plane but can easily move in the z-direction. This shows on the length scale of the K film thickness, the electronic properties of the film do not change noticeably during the metal-insulator transition. The superconducting proximity effect is investigated for SN-double layers in the thin film limit. In this regime, the normalized initial slope Ssn = (ds=Ts )|dTc=ddn| is independent of the thickness of the superconductor, the mean free path of the films and the transparency of the interface if it is not too small. The transition temperature Tc is compared with a numerical calculation developed in our group. The deviation between the experiment and theory decreases from the normal metal to the superconductor with a relative high transition temperature. The deviation factor decreases from 2.5 for Cu, Ag, Au, Mg to 1.5 for Cd, Zn, Al and finally no disagreement for In and Sn. A weak perpendicular magnetic field is applied on the super- and normal conductor double layers. The difference of the transition temperature dTc measured with and without magnetic field increases with increasing the normal metal thickness. A quantitative explanation is given based on the increased dephasing of the electrons in the magnetic field. Numerical calculation of the transition temperature based on the strong coupling theory is also given and compared with the experimental results.

  7. Alkali Metal Rankine Cycle Boiler Technology Challenges and Some Potential Solutions for Space Nuclear Power and Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Stone, James R.

    1994-01-01

    Alkali metal boilers are of interest for application to future space Rankine cycle power conversion systems. Significant progress on such boilers was accomplished in the 1960's and early 1970's, but development was not continued to operational systems since NASA's plans for future space missions were drastically curtailed in the early 1970's. In particular, piloted Mars missions were indefinitely deferred. With the announcement of the Space Exploration Initiative (SEI) in July 1989 by President Bush, interest was rekindled in challenging space missions and, consequently in space nuclear power and propulsion. Nuclear electric propulsion (NEP) and nuclear thermal propulsion (NTP) were proposed for interplanetary space vehicles, particularly for Mars missions. The potassium Rankine power conversion cycle became of interest to provide electric power for NEP vehicles and for 'dual-mode' NTP vehicles, where the same reactor could be used directly for propulsion and (with an additional coolant loop) for power. Although the boiler is not a major contributor to system mass, it is of critical importance because of its interaction with the rest of the power conversion system; it can cause problems for other components such as excess liquid droplets entering the turbine, thereby reducing its life, or more critically, it can drive instabilities-some severe enough to cause system failure. Funding for the SEI and its associated technology program from 1990 to 1993 was not sufficient to support significant new work on Rankine cycle boilers for space applications. In Fiscal Year 1994, funding for these challenging missions and technologies has again been curtailed, and planning for the future is very uncertain. The purpose of this paper is to review the technologies developed in the 1960's and 1970's in the light of the recent SEI applications. In this way, future Rankine cycle boiler programs may be conducted most efficiently. This report is aimed at evaluating alkali metal boiler

  8. Relationship between chemical structure and biological activity of alkali metal o-, m- and p-anisates. FT-IR and microbiological studies

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Piekut, J.; Lewandowski, W.

    2011-11-01

    In this work we investigated relationship between molecular structure of alkali metal o-, m-, p-anisate molecules and their antimicrobial activity. For this purpose FT-IR spectra for lithium, sodium, potassium, rubidium and caesium anisates in solid state and solution were recorded, assigned and analysed. Microbial activity of studied compounds was tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris. In order to evaluate the dependency between chemical structure and biological activity of alkali metal anisates the statistical analysis (multidimensional regression and principal component) was performed for selected wavenumbers from FT-IR spectra and parameters that describe microbial activity of anisates. The obtained statistical equations show the existence of correlation between molecular structure of anisates and their biological properties.

  9. Local alkali-metal-promoted oxidation of Si(100)-(2×1) surfaces: A generalized-Hubbard-model calculation

    NASA Astrophysics Data System (ADS)

    Refolio, M. C.; López Sancho, J. M.; López Sancho, M. P.; Rubio, J.

    1994-01-01

    In order to study the local regime in the alkali-metal-promoted oxidation of silicon, we consider the coadsorption of an oxygen molecule and a potassium atom on the dimerized Si(100)-(2×1) surface. Antiferromagnetic (singlet) spin correlations within the Si dimers are taken into account from the outset by working with a generalized Hubbard Hamiltonian. In this background, the adsorption of a K atom strongly polarizes the medium creating a local charge-spin bag, around the K+ ion, which sets the scenario for promoted oxidation. When an O2 molecule in its ground state (3Σg) approaches this region of the surface, it is influenced by the attractive electrostatic field of the K+ ion, with the corresonding lowering of its affinity level. This eventually crosses the Fermi level and captures the excess electron charge in the bag. A superoxide O2 ion, the 2Πg state, is thereby formed, ionicly bonded to K+ and covalently bonded to the Si dimer. In the absence of potassium, the oxygen molecule simply physisorbs in a state adiabatically connected to its gas-phase ground state.

  10. The electronic properties of bare and alkali metal adsorbed two-dimensional GeSi alloy sheet

    NASA Astrophysics Data System (ADS)

    Qiu, Wenhao; Ye, Han; Yu, Zhongyuan; Liu, Yumin

    2016-09-01

    In this paper, the structural and electronic properties of both bare and alkali metal (AM) atoms adsorbed two-dimensional GeSi alloy sheet (GeSiAS) are investigated by means of first-principles calculations. The band gaps of bare GeSiAS are shown slightly opened at Dirac point with the energy dispersion remain linear due to the spin-orbit coupling effect at all concentrations of Ge atoms. For metal adsorption, AM atoms (including Li, Na and K) prefer to occupy the hexagonal hollow site of GeSiAS and the primary chemical bond between AM adatom and GeSiAS is ionic. The adsorption energy has an increase tendency with the increase of the Ge concentration in supercell. Besides, single-side adsorption of AM atoms introduces band gap at Dirac point, which can be tuned by the Ge concentration and the species of AM atoms. The strong relation between the band gaps and the distribution of Si and Ge atoms inside GeSiAS are also demonstrated. The opened band gaps of AM covered GeSiAS range from 14.8 to 269.1 meV along with the effective masses of electrons ranging from 0.013 to 0.109 me, indicating the high tunability of band gap as well as high mobility of carriers. These results provide a development in two-dimensional alloys and show potential applications in novel micro/nano-electronic devices.

  11. The Debaryomyces hansenii NHA1 gene encodes a plasma membrane alkali-metal-cation antiporter with broad substrate specificity.

    PubMed

    Velkova, Klara; Sychrova, Hana

    2006-03-15

    Debaryomyces hansenii is a yeast species often found in salty environments. Its genome sequence is known completely, but the mechanisms behind its halotolerance are poorly understood. In the D. hansenii genome, there is a gene strongly homologous to the Saccharomyces cerevisiae NHA1 gene (encoding a plasma membrane Na+/H+ antiporter). We isolated this DhNHA1 gene from two D. hansenii strains (CBS 767 and CBS 1793) differing in their osmotolerance. Both DhNHA1 alleles were heterologously expressed in a S. cerevisiae strain lacking its own systems for the efflux of alkali metal cations (BW31a, ena1-4delta nha1delta). D. hansenii Na+/H+ antiporters were localized in the plasma membrane of BW31a cells, their presence increased BW31a tolerance to sodium, potassium, lithium and also rubidium. Measurements of Na+ and K+ efflux from S. cerevisiae cells expressing DhNHA1 alleles show that the D. hansenii antiporters efficiently transported both cations out of cells. The sodium and potassium transport activity of Nha1 antiporters from both D. hansenii strains was almost identical, indicating that plasma membrane antiporter activity is not one of the factors determining the different levels of halotolerance in the two strains. PMID:16303259

  12. Theoretical calculation of plane wave speeds for alkali metals under pressure.

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Macdonald, D. E.; Arkilic, G. M.

    1971-01-01

    Theoretical calculations of the variation with pressure of small amplitude plane wave speeds are performed for sodium and potassium at zero temperature. The results obtained for wave speeds associated with volume dependent second-order elastic coefficients show better agreement with experimental data than for wave speeds associated with shear dependent coefficients. This result is believed to be due to omission of the band structure correction to the strain energy density.

  13. ACE applied to the quantitative characterization of benzo-18-crown-6-ether binding with alkali metal ions in a methanol-water solvent system.

    PubMed

    Ehala, Sille; Makrlík, Emanuel; Toman, Petr; Kasicka, Václav

    2010-01-01

    ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo-18-crown-6-ether (B18C6) and several alkali metal ions, Li(+), Na(+), K(+), Rb(+) and Cs(+), in a mixed binary solvent system, methanol-water (50/50 v/v). The apparent binding (stability) constants (K(b)) of B18C6-alkali metal ion complexes in the hydro-organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25 degrees C, and the constant ionic strength, 10 mM. In the 50% v/v methanol-water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K(b)=2.89+/-0.17), the weakest complex with cesium ion (log K(b)=2.04+/-0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol-water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water. PMID:20108263

  14. Conditions for preparation of ultrapure beryllium by electrolytic refining in molten alkali-metal chlorides

    SciTech Connect

    Wohlfarth, Hagen

    1982-02-01

    Electrolytic refining is regarded as the most suitable process for the production of beryllium with impurity contents below 1 at.-ppM. Several parameters are important for electrolytic refining of beryllium in a BeCl/sub 2/-containing LiCl-KCl melt: current density, BeCl/sub 2/ content, electrolyte temperature, composition of the unpurified beryllium and impurity-ion concentrations in the melt, as well as apparatus characteristics such as rotation speed of the cathode and condition of the crucible material. These factors were studied and optimized such that extensive removal of the maximum number of accompanying and alloying elements was achieved.

  15. SHOULD LATITUDINAL ATMOSPHERIC TRACE VAPOR CONCENTRATIONS BE REPORTED ON A MASS DENSITY BASIS?

    EPA Science Inventory

    For the past several decades the issue of global atmospheric trace vapor migration has been of concern to environmental professionals concerned with global distillation/cold condensation of toxic compounds, contamination of remote ecosystems, global climate change and stratospher...

  16. Alkali Metal-Glucose Interaction Probed with Infrared Pre-Dissociation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kregel, Steven J.; Marsh, Brett; Zhou, Jia; Garand, Etienne

    2015-06-01

    The efficient extraction of cellulose from biomass and its subsequent conversion to glucose derivatives is an attractive goal in the field of energy science. However, current industrial methods require high ionic strength and harsh conditions. Ionic liquids (IL's) are a class of "green" compounds that have been shown to dissolve cellulose in concentrations of up to 25 wt%. In order to understand IL's extraordinary cellulose dissolving power, a molecular level understanding of the IL-cellulose interaction is needed. Toward that end, we have acquired infrared pre-dissociation spectra of M+-glucose, where M+=Li+, Na+, or K+. Through comparisons with density functional theory calculations, we have determined the relative abundances of various M+-glucose binding motifs in both the thermodynamic and kinetic limits. These results provide insight on the hydrogen bonding dynamics of glucose and are a step towards a fuller understanding of cellulose interactions with ionic liquids.

  17. Low temperature alkali metal-sulfur batteries. Final report, December 1, 1974-November 30, 1978

    SciTech Connect

    Brummer, S.B.; Rauh, R.D.; Abraham, K.M.; Dampier, F.W.; Subrahmanyam, V.; Pearson, G.F.; Surprenant, J.K.; Buzby, J.M.

    1980-03-01

    Work on the development of rechargeable, ambient-temperature Li/sulfur and Li/metal sulfide batteries is reported. The Li/S system has the cathode material dissolved in the electrolyte, as Li/sub 2/S/sub n/. Tetrahydrofuran, 1M LiAsF/sub 6/, is one of the more attractive electrolytes discovered for this cell, since it can dissolve up to approx. 10M S as Li/sub 2/Sn. Despite the oxidative nature of the electrolyte, Li is stable in it and can be electrodeposited from it on battery charge. Cells of the configuration Li 5M S (as Li/sub 2/S/sub n/), THF, 1M LiAsF/sub 6//carbon can be discharged at 50/sup 0/C with a utilization of nearly 1.5e/sup -//S at the C/3 rate. This corresponds to the rate-capacity goal for this battery in its proposed vehicular or load-leveling applications. Further improvements in rate are possible. Rechargeability of 135 cycles of 0.1 e/sup -//S and approx. 45 cycles of 0.5 e/sup -//S was demonstrated. The self-discharge reaction keeps the Li electrode free of electrically isolated dendrites. Ultimate failure on cycling is due to cathode depletion via precipitation of Li/sub 2/S on the anode in a form insoluble in the electrolyte. Attempts to solubilize the Li/sub 2/S by the internal generation of an oxidizing scavenger (e.g., Br/sub 2/) or by addition of Lewis acids have met only with limited success. Cells of configuration Li/THF, 1M LiAsF/sub 6//insoluble metal sulfide were investigated, using the following cathodes: CuS, NiS, SiS/sub 2/, MnS/sub 2/, FeS, and Bi/sub 2/S/sub 3/. Of these, the most promising new material in terms of energy density and rechargeability is CuS. Well over 100 cycles for Li/CuS cells with moderate cathode loadings were demonstrated. CuS compares favorably with TiS/sub 2/ in terms of energy density and rechargeability and is superior in terms of economics. 39 figures, 19 tables.

  18. Thermodynamic investigation of the effect of alkali metal impuries on the processing of aluminum and magnesium alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Shengjun

    2006-12-01

    of aluminum and magnesium alloys. As the first step of the thermodynamic description of the high-order system, the constitutive-binary systems were modeled in the present work using the CALPHAD technique combined with first-principles calculations. Then, ternaries and higher order systems can be modeled. For ternary systems without experimental data, the thermodynamic description is extrapolated by combining three constitutive-binary systems. Alkali-metal induced high temperature embrittlement (HTE) and loss of ductility were investigated in Al-Li, Al-Mg and Mg-Li alloys. It was discovered that the alkali-metal-rich liquid-2 phase is the cause of HTE and the loss of ductility is proportional to the mole fraction of the liquid phase and the grain size. The calculated results are consistent with experimental observations in the literature and were used to determine HTE safe and sensitive zones, maximum and critical hot-rolling temperatures and the maximum allowable Na content in alloys, which can be used to industrial processing of Al and Mg alloys. The degree of HTE is proportional to the mole fraction of the liquid-2 phase and the grain size.

  19. Transport of Carbon Tetrachloride in a Fractured Vadose Zone due to Atmospheric Pressure Fluctuations, Diffusion, and Vapor Density

    NASA Astrophysics Data System (ADS)

    McCray, J. E.; Downs, W.; Falta, R. W.; Housley, T.

    2005-12-01

    DNAPL sources of carbon tetrachloride (CT) vapors are of interest at the Radioactive Waste Management Complex (RWMC) at the Idaho National Engineering and Environmental Laboratory (INEEL). The site is underlain by thick fractured basalt that includes sedimentary interbeds, each are a few meters thick. Daily atmospheric pressure fluctuations serve as driving forces for CT vapor transport in the subsurface. Other important transport processes for vapor movement include gas-phase diffusion and density-driven transport. The objective of this research is to investigate the influence and relative importance of these processes on gaseous transport of CT. Gas pressure and vapor concentration measurements were conducted at various depths in two wells. A numerical multiphase flow model (TOUGH2), calibrated to field pressure data, is used to conduct sensitivity analyses to elucidate the importance of the different transport mechanisms. Results show that the basalt is highly permeable to vertical air flow. The pressure dampening occurs mainly in the sedimentary interbeds. Model-calibrated permeability values for the interbeds are similar to those obtained in a study by the U.S. Geological Survey for shallow sediments, and an order of magnitude higher than column-scale values obtained by previous studies conducted by INEEL scientists. The transport simulations indicate that considering the effect of barometric pressure changes is critical to simulating transport of pollutants in the vadose zone above the DNAPL source. Predicted concentrations can be orders of magnitude smaller than actual concentrations if the effect is not considered. Below the DNAPL vapor source, accounting for density and diffusion alone would yield acceptable results provided that a 20% error in concentrations are acceptable, and that simulating concentrations trends (and not actual concentrations) is the primary goal.

  20. Alkali metal ion induced cube shaped mesoporous hematite particles for improved magnetic properties and efficient degradation of water pollutants.

    PubMed

    Roy, Mouni; Naskar, Milan Kanti

    2016-07-27

    Mesoporous cube shaped hematite (α-Fe2O3) particles were prepared using FeCl3 as an Fe(3+) precursor and 1-butyl-3-methylimidazolium bromide (ionic liquid) as a soft template in the presence of different alkali metal (lithium, sodium and potassium) acetates, under hydrothermal conditions at 150 °C/4 h followed by calcination at 350 °C. The formation of the α-Fe2O3 phase in the synthesized samples was confirmed by XRD, FTIR and Raman spectroscopy. Unlike K(+) ions, intercalation of Li(+) and Na(+) ions occurred in α-Fe2O3 crystal layers as evidenced by XRD and Raman spectroscopy. Electron microscopy (FESEM and TEM) images showed the formation of cube-like particles of different sizes in the presence of Li(+), Na(+) and K(+) ions. The mesoporosity of the products was confirmed by N2 adsorption-desorption studies, while their optical properties were analyzed by UV-DRS. Na(+) ion intercalated α-Fe2O3 microcubes showed improved coercivity (5.7 kOe) due to increased strain in crystals, and shape and magnetocrystalline anisotropy. Temperature dependent magnetization of the samples confirmed the existence of Morin temperature in the range of 199-260 K. Catalytic degradation of methylene blue (MB), a toxic water pollutant, was studied using the synthesized products via a heterogeneous photo-Fenton process. The degradation products were traced by electrospray ionization-mass spectrometry (ESI-MS). The α-Fe2O3 microcubes obtained in the presence of Na(+) ions exhibited a more efficient degradation of MB to non-toxic open chain products. PMID:27406648

  1. Comparison of dissociation mechanism between collisionally activated dissociation and charge inversion using alkali metal targets for chlorophenol isomers

    NASA Astrophysics Data System (ADS)

    Hayakawa, Shigeo; Kawamura, Yoshiaki; Takahashi, Yutaka

    2005-11-01

    Chlorinated aromatic compounds are well-known environmental pollutants whose toxicities depend dramatically on the chlorine substitution pattern, making differentiation of chlorophenol isomers important for environmental analysis. Collisionally activated dissociation (CAD) spectra and charge inversion spectra of ortho-, meta-, and para-chlorophenols (ClC6H4OH) and their partially deuterated forms (ClC6H4OD) were measured using alkali metal targets. The peaks associated with C6H4O+ and C5H5Cl+ ions observed in the CAD spectra result from the loss of HCl and CO fragments, respectively, after the re-arrangement of the hydroxyl hydrogen atom. The peaks associated with C6H4OH- and ClC6H4O- ions observed in the charge inversion spectra result from Cl loss and from hydroxyl bond dissociation, respectively. Isomeric differentiation is possible based on the clear differences observed in the relative intensities of these pairs of peaks. Although the intensities of the peaks associated with C6H4O+ relative to those of C5H5Cl+ in the CAD spectra are independent of the target species, the intensities of the peaks associated with C6H4OH- relative to those of ClC6H4O- in the charge inversion spectra are target dependent. The isomeric dependence of the positive ion distribution patterns in the CAD spectra is proposed to be due to the differences in the rate of the hydrogen atom re-arrangement process. In contrast, the isomeric dependence of the negative ion distribution patterns in the charge inversion spectra is attributed to differences in the bond strength involved in the direct dissociation process in the neutral intermediate species.

  2. Soil sampling and analysis plan for the 3718-F Alkali Metal Treatment and Storage Facility closure activities

    SciTech Connect

    Sonnichsen, J.C.

    1997-05-01

    Amendment V.13.B.b to the approved closure plan (DOE-RL 1995a) requires that a soil sampling and analysis plan be prepared and submitted to the Washington State Department of Ecology (Ecology) for review and approval. Amendment V.13.B.c requires that a diagram of the 3718-F Alkali Metal Treatment and Storage Facility unit (the treatment, storage, and disposal [TSD] unit) boundary that is to be closed, including the maximum extent of operation, be prepared and submitted as part is of the soil sampling and analysis plan. This document describes the sampling and analysis that is to be performed in response to these requirements and amends the closure plan. Specifically, this document supersedes Section 6.2, lines 43--46, and Section 7.3.6 of the closure plan. Results from the analysis will be compared to cleanup levels identified in the closure plan. These cleanup levels will be established using residential exposure assumptions in accordance with the Model Toxics Control Act (MTCA) Cleanup Regulation (Washington Administrative Code [WAC] 173-340) as required in Amendment V.13.B.I. Results of all sampling, including the raw analytical data, a summary of analytical results, a data validation package, and a narrative summary with conclusions will be provided to Ecology as specified in Amendment V.13.B.e. The results and process used to collect and analyze the soil samples will be certified by a licensed professional engineer. These results and a certificate of closure for the balance of the TSD unit, as outlined in Chapter 7.0 of the approved closure plan (storage shed, concrete pad, burn building, scrubber, and reaction tanks), will provide the basis for a closure determination.

  3. Transfer of spin angular momentum from Cs vapor to nearby Cs salts through laser-induced spin currents

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.

    2011-06-01

    Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.

  4. Transfer of spin angular momentum from Cs vapor to nearby Cs salts through laser-induced spin currents

    SciTech Connect

    Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.

    2011-06-15

    Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.

  5. A Three Level Analytic Model for Alkali Vapor Lasers

    SciTech Connect

    Hager, Gordon D.; Perram, Glen P.

    2010-10-08

    A three level analytic model for optically pumped alkali metal vapor lasers is developed considering the steady-state rate equations for the longitudinally averaged number densities of the ground {sup 2}S{sub 1/2} and first excited {sup 2}P{sub 1/2} and {sup 2}P{sub 3/2} states. The threshold pump intensity includes both the requirements to fully bleach the pump transition and exceed optical losses, typically about 200 W/cm{sup 2}. Slope efficiency depends critically on the fraction of incident photons absorbed and the overlap of pump and resonator modes, approaching the quantum efficiency of 0.95-0.98, depending on alkali atom. For efficient operation, the collisional relaxation between the two upper levels should be fast relative to stimulated emission. By assuming a statistical distribution between the upper levels, the limiting analytic solution for the quasi-two level system is achieved. Application of the model and comparisons to recent laser demonstrations is presented.

  6. Molecular Weight Determination by an Improved Temperature-Monitored Vapor-Density Method.

    ERIC Educational Resources Information Center

    Grider, Douglas J.; And Others

    1988-01-01

    Recommends determining molecular weights of liquids by use of a thermocouple. Utilizing a mathematical gas equation, the molecular weight can be determined from the measurement of the vapor temperature upon complete evaporation. Lists benefits as reduced time and cost, and improved safety factors. (ML)

  7. Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels.

    PubMed

    Boday, Dylan J; Stover, Robert J; Muriithi, Beatrice; Keller, Michael W; Wertz, Jason T; Defriend Obrey, Kimberly A; Loy, Douglas A

    2009-07-01

    Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density. PMID:20355935

  8. Spectrum, radial wave functions, and hyperfine splittings of the Rydberg states in heavy alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Sanayei, Ali; Schopohl, Nils

    2016-07-01

    We present numerically accurate calculations of the bound-state spectrum of the highly excited valence electron in the heavy alkali-metal atoms solving the radial Schrödinger eigenvalue problem with a modern spectral collocation method that applies also for a large principal quantum number n ≫1 . As an effective single-particle potential we favor the reputable potential of Marinescu et al. [Phys. Rev. A 49, 982 (1994)], 10.1103/PhysRevA.49.982. Recent quasiclassical calculations of the quantum defect of the valence electron agree for orbital angular momentum l =0 ,1 ,2 ,... overall remarkably well with the results of the numerical calculations, but for the Rydberg states of rubidium and also cesium with l =3 this agreement is less fair. The reason for this anomaly is that in rubidium and cesium the potential acquires for l =3 deep inside the ionic core a second classical region, thus invalidating a standard Wentzel-Kramers-Brillouin (WKB) calculation with two widely spaced turning points. Comparing then our numerical solutions of the radial Schrödinger eigenvalue problem with the uniform analytic WKB approximation of Langer constructed around the remote turning point rn,j ,l (" close=")n -δ0)">+ we observe everywhere a remarkable agreement, apart from a tiny region around the inner turning point rn,j ,l (-). For s states the centrifugal barrier is absent and no inner turning point exists: rn,j ,0 (-)=0 . With the help of an ansatz proposed by Fock we obtain for the s states a second uniform analytic approximation to the radial wave function complementary to the WKB approximation of Langer, which is exact for r →0+ . From the patching condition, that is, for l =0 the Langer and Fock solutions should agree in the intermediate region 0

  9. CO2 Extraction from Ambient Air Using Alkali-Metal Hydroxide Solutions Derived from Concrete Waste and Steel Slag

    NASA Astrophysics Data System (ADS)

    Stolaroff, J. K.; Lowry, G. V.; Keith, D. W.

    2003-12-01

    To mitigate global climate change, deep reductions in CO2 emissions are required in the coming decades. Carbon sequestration will play a crucial role in this reduction. Early adoption of carbon sequestration in low-cost niche markets will help develop the technology and experience required for large-scale deployment. One such niche may be the use of alkali metals from industrial waste streams to form carbonate minerals, a safe and stable means of sequestering carbon. In this research, the potential of using two industrial waste streams---concrete and steel slag---for sequestering carbon is assessed. The scheme is outlined as follows: Ca and Mg are leached with water from a finely ground bed of steel slag or concrete. The resulting solution is sprayed through air, capturing CO2 and forming solid carbonates, and collected. The feasibility of this scheme is explored with a combination of experiments, theoretical calculations, cost accounting, and literature review. The dissolution kinetics of steel slag and concrete as a function of particle size and pH is examined. In stirred batch reactors, the majority of Ca which dissolved did so within the first hour, yielding between 50 and 250 (mg; Ca)/(g; slag) and between 10 and 30 (mg; Ca)/(g; concrete). The kinetics of dissolution are thus taken to be sufficiently fast to support the type of scheme described above. As proof-of-concept, further experiments were performed where water was dripped slowly through a stagnant column of slag or concrete and collected at the bottom. Leachate Ca concentrations in the range of 15 mM were achieved --- sufficient to support the scheme. Using basic physical principles and numerical methods, the quantity of CO2 captured by falling droplets is estimated. Proportion of water loss and required pumping energy is similarly estimated. The results indicate that sprays are capable of capturing CO2 from the air and that the water and energy requirements are tractable. An example system for

  10. High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of mixed-alkali metals uranyl silicates

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Hsin; Liu, Hsin-Kuan; Chang, Wen-Jung; Tzou, Der-Lii; Lii, Kwang-Hwa

    2016-04-01

    Three mixed-alkali metals uranyl silicates, Na3K3[(UO2)3(Si2O7)2]·2H2O (1), Na3Rb3[(UO2)3(Si2O7)2] (2), and Na6Rb4[(UO2)4Si12O33] (3), have been synthesized by high-temperature, high-pressure hydrothermal reactions at 550 °C and 1440 bar, and characterized by single-crystal X-ray diffraction, photoluminescence, and thermogravimetric analysis. Compound 1 and 2 are isostructural and contain layers of uranyl disilicate. The smaller cation, Na+, is located in the intralayer channels, whereas the larger cations, K+ and Rb+, and water molecule are located in the interlayer region. The absence of lattice water in 2 can be understood according to the valence-matching principle. The structure is related to that of a previously reported mixed-valence uranium(V,VI) silicate. Compound 3 adopts a 3D framework structure and contains a unique unbranched dreier fourfold silicate chain with the structural formula {uB,41∞}[3Si12O33] formed of Q2, Q3, and Q4 Si. The connectivity of the Si atoms in the Si12O3318- anion can be interpreted on the basis of Zintl-Klemm concept. Crystal data for compound 1: triclinic, P-1, a=5.7981(2) Å, b=7.5875(3) Å, c=12.8068(5) Å, α=103.593(2)°, β=102.879(2)°, γ=90.064(2)°, V=533.00(3) Å3, Z=1, R1=0.0278; compound 2: triclinic, P-1, a=5.7993(3) Å, b=7.5745(3) Å, c=12.9369(6) Å, α=78.265(2)°, β=79.137(2)°, γ=89.936(2)°, V=546.02(4) Å3, Z=1, R1=0.0287; compound 3: monoclinic, C2/m, a=23.748(1) Å, b=7.3301(3) Å, c=15.2556(7) Å, β=129.116(2)°, V=2060.4(2) Å3, Z=2, R1=0.0304.

  11. Ab initio study of the adsorption, diffusion, and intercalation of alkali metal atoms on the (0001) surface of the topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Ryabishchenkova, A. G.; Otrokov, M. M.; Kuznetsov, V. M.; Chulkov, E. V.

    2015-09-01

    Ab initio study of the adsorption, diffusion, and intercalation of alkali metal adatoms on the (0001) step surface of the topological insulator Bi2Se3 has been performed for the case of low coverage. The calculations of the activation energies of diffusion of adatoms on the surface and in van der Waals gaps near steps, as well as the estimate of diffusion lengths, have shown that efficient intercalation through steps is possible only for Li and Na. Data obtained for K, Rb, and Cs atoms indicate that their thermal desorption at high temperatures can occur before intercalation. The results have been discussed in the context of existing experimental data.

  12. CH 3Cl adsorption on a Si(100)2 × 1 surface modified by alkali metal overlayer studied by soft X-ray photoemission using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Gentle, T. M.; Soukiassian, P.; Schuette, K. P.; Bakshi, M. H.; Hurych, Z.

    1988-08-01

    We present the first study of the effect of an alkali metal overlayer on the adsorption of an organic molecule, methylchloride, on a Si(100)2 × 1 surface. In strong contrast to the behavior of molecular oxygen or nitrogen which were found to react with the silicon substrate, there was no significant interaction between methylchloride and silicon, rather, the formation of alkali-chlorine bonds was observed. Core level and valence band spectroscopies using synchrotron radiation were used to study these systems. Sodium was found to exhibit the strongest interaction with mehtylchloride which was dissociated, while the effects produced by K and Cs were weaker.

  13. The Production of Polycyclic Aromatic Hydrocarbon Anions in Inert Gas Matrices Doped with Alkali Metals. Electronic Absorption Spectra of the Pentacene Anion (C22H14(-))

    NASA Technical Reports Server (NTRS)

    Halasinski, Thomas M.; Hudgins, Douglas M.; Salama, Farid; Allamandola, Louis J.; Mead, Susan (Technical Monitor)

    1999-01-01

    The absorption spectra of pentacene (C22H14) and its radical cation (C22H14(+)) and anion (C22H14(-)) isolated in inert-gas matrices of Ne, Ar, and Kr are reported from the ultraviolet to the near-infrared. The associated vibronic band systems and their spectroscopic assignments are discussed together with the physical and chemical conditions governing ion (and counterion) production in the solid matrix. In particular, the formation of isolated pentacene anions is found to be optimized in matrices doped with alkali metal (Na and K).

  14. Alkali metal, alkaline earth metal, and ammonium ion selectivities of dibenzo-16-crown-5 compounds with functional side arms in ion-selective electrodes

    SciTech Connect

    Ohki, Akira; Lu, J.P.; Huang, X.; Bartsch, R.A. )

    1994-12-01

    Potentiometric selectivities of 11 dibenzo-16-crown-5 compounds for alkali metal, alkaline earth metal, and ammonium ions have been determined in solvent polymeric membrane electrodes. The ionophores bear one or two pendent groups on the central carbon of the three-carbon bridge in the polyether ring. Side-arm variation includes OCH[sub 3], OCH[sub 2]CH[sub 2]OCH[sub 3], OCH[sub 2]CO[sub 2]C[sub 2]H[sub 5], OCH[sub 2]C(O)N(C[sub 2]H[sub 5])[sub 2], and OCH[sub 2]C(O)N(C[sub 5]H[sub 11])[sub 2] units. Attachment of a propyl group to the ring carbon that bears an extended, oxygen-containing side arm increases the selectivity for Na[sup +] relative to larger alkali metal and alkaline earth metal cations. For a given side arm, a linear relationship is obtained when the enhancement in Na[sup +] selectivity produced by attachment of a geminal propyl group is plotted against the diameter of the interference ion. Potentiometric responses of the dibenzo-16-crown-5 compounds are rationalized in terms of the crown ether ring size and the oxygen basicity, conformational positioning, and rigidity of the side arm. 22 refs., 3 figs., 2 tabs.

  15. Different Cation Arrangements in Au-In Networks. Syntheses and Structures of Six Intermetallic Compounds in Alkali-Metal-Au-In Systems

    SciTech Connect

    Bin Li; John D. Corbett

    2007-06-20

    Six robust intermetallic compounds with cations in three different tunnel-like structures have been synthesized in alkali-metal-Au-In systems via high-temperature solid-state methods and characterized by X-ray diffraction: AAu{sub 4}-In{sub 6} [A = K (I), Rb (II), F6m2, Z = 1], K{sub 1.76(6)}Au{sub 6}Ln{sub 4} (III,; 4/mcm, Z = 4), and A{sub x}Au{sub 2}In{sub 2} [x{approx} 0.7, A = K (IV), Rb (V), Cs (VI), P4{sub 2}/nmc, Z = 8]. The first type is constructed from a single cage unit: an alkali-metal-centered 21-vertex polyhedron A@AugIn12 with 6-9-6 arrangement of planar rings. The others contain uniaxial arrays of tunnels built of differently puckered eight- and four-member Au/In rings. The largely different cation distributions depend on the tunnel constitutions and cation sizes. Tight-binding electronic structure calculations by linear muffin-tin-orbital (LMTO) methods were performed for I and idealized III in order to help understand their chemical bonding. These also reveal large differences in relativistic effects for Au d orbitals, as well as for different Au sites in each structure.

  16. Different Cation Arrangements in Au-In Networks. Syntheses and Structures of Six Intermetallic compounds in Alkali-Metal-Au-In Systems

    SciTech Connect

    Li, Bin; Corbett, John D.

    2007-06-20

    Six robust intermetallic compounds with cations in three different tunnel-like structures have been synthesized in alkali-metal-Au-In systems via high-temperature solid-state methods and characterized by X-ray diffraction: AAu{sub 4}-In{sub 6} [A = K (I), Rb (II), F6m2, Z = 1], K{sub 1.76(6)}Au{sub 6}Ln{sub 4} (III, /4/mcm, Z = 4), and A{sub x}Au{sub 2}In{sub 2} [x {approx} 0.7, A = K (IV), Rb (V), Cs (VI), P4{sub 2}/nmc, Z = 8]. The first type is constructed from a single cage unit: an alkali-metal-centered 21-vertex polyhedron A{at}AugIn{sub 12} with 6-9-6 arrangement of planar rings. The others contain uniaxial arrays of tunnels built of differently puckered eight- and four-member Au/In rings. The largely different cation distributions depend on the tunnel constitutions and cation sizes. Tight-binding electronic structure calculations by linear muffin-tin-orbital (LMTO) methods were performed for I and idealized III in order to help understand their chemical bonding. These also reveal large differences in relativistic effects for Au d orbitals, as well as for different Au sites in each structure.

  17. Temporal evolution of the electron density produced by nanosecond repetitively pulsed discharges in water vapor at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Sainct, Florent; Lacoste, Deanna; Kirkpatrick, Michael; Odic, Emmanuel; Laux, Christophe

    2014-10-01

    A study of plasma discharges produced by nanosecond repetitive pulses (NRP) in water vapor at 450 K and 1 atm is presented. The plasma was generated between two point electrodes with 20-ns duration, high-voltage (0--20 kV) pulses, at a repetition frequency of 10 kHz, in the spark regime (2 mJ/pulse). Atomic lines measured by optical emission spectroscopy were used to determine the electron number density in this non-equilibrium water-vapor plasma. The broadenings and shifts of the Hα and Hβ lines of the hydrogen Balmer series and of the atomic oxygen triplet at 777 nm were analyzed. For a maximum reduced electric field of about 200 Td, a maximum electron density of 2 × 1018 cm-3 was measured, corresponding to an ionization level of about 10 %. This ionization level is two orders of magnitude higher than the one obtained for similar NRP discharges in air at atmospheric pressure.

  18. Carbon dioxide laser vaporization: Relationship of scar formation to power density

    SciTech Connect

    Dobry, M.M.; Padilla, R.S.; Pennino, R.P.; Hunt, W.C.

    1989-07-01

    A direct relationship exists between the power density of a carbon dioxide laser and the thickness of scars it produces in rat skin. Statistically significant positive relationships were noted between laser power and scar thickness at days 14, 21, and 32. The slope of the curve increased as the number of days elapsed. At day 32, the ratio of scar thickness to CO/sub 2/ laser power density delivered was 0.3 microns/W-cm/sup 2/. Scar formation took longer for completion at higher wattages of irradiation.

  19. Novel solid-phase epitaxy for multi-component materials with extremely high vapor pressure elements: An application to KFe2As2

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Taisuke; Sato, Hikaru; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2016-05-01

    We propose a novel solid-phase epitaxy technique applicable to high annealing temperatures up to 1000 °C without re-vaporization of alkali metal elements with high vapor pressures. This technique is demonstrated through the successful growth of high-quality KFe2As2 epitaxial films. The key factors are employing a custom-designed alumina vessel/cover and sealing it in a stainless tube with a large amount of atmospheric KFe2As2 powder in tightly closed sample spaces. This technique can also be effective for other materials composed of elements with very high vapor pressures, such as alkali metals, and can lead to the realization of spintronics devices in the future using KFe2As2.

  20. Ab initio study of the adsorption, diffusion, and intercalation of alkali metal atoms on the (0001) surface of the topological insulator Bi2 Se3

    NASA Astrophysics Data System (ADS)

    Otrokov, Mikhail; Ryabishchenkova, Anastasia; Gosalvez, Miguel Angel; Kuznetsov, Vladimir; Chulkov, Evgueni

    We present the results of an ab initio study of the adsorption, diffusion, and intercalation of alkali metal adatoms on the (0001) stepped surface of the topological insulator Bi2Se3 for the case of low coverage. The calculations of the activation energies of the adatoms diffusion on the surface and in the van der Waals gaps near the steps, as well as the estimation of diffusion lengths, show that efficient intercalation through the steps is possible only for Li and Na. Data obtained for K, Rb, and Cs atoms indicate that their thermal desorption at high temperatures can start before intercalation. These results are discussed in the context of the experimental data available.

  1. Effects of Na2MoO4 and Na2WO4 on molybdenum and tungsten electrodes for the alkali metal thermoelectric converter (AMTEC)

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Wheeler, B. L.; Jeffries-Nakamura, B.; Loveland, M. E.; Bankston, C. P.

    1988-01-01

    The effects of adding Na2MoO4 and Na2WO4 to porous Mo and W electrodes, respectively, on the performance and impedance characteristics of the electrodes in an alkali metal thermoelectric converter (AMTEC) were investigated. It was found that corrosion of the porous electrode by Na2MoO4 or Na2WO4 to form Na2MO3O6 and WO2, respectively, and recrystallization of the Mo or W as the salt evaporates, result in major morphological changes including a loss of columnar structure and a significant increase in porosity. This effect is more pronounced in Na2MoO4/Mo electrodes, due to the lower stability of Na2MoO4.

  2. Dispersion coefficients for the interactions of the alkali-metal and alkaline-earth-metal ions and inert-gas atoms with a graphene layer

    NASA Astrophysics Data System (ADS)

    Kaur, Kiranpreet; Arora, Bindiya; Sahoo, B. K.

    2015-09-01

    Largely motivated by a number of applications, the van der Waals dispersion coefficients C3 of the alkali-metal ions Li+,Na+,K+, and Rb+, the alkaline-earth-metal ions Ca+,Sr+,Ba+, and Ra+, and the inert-gas atoms He, Ne, Ar, and Kr with a graphene layer are determined precisely within the framework of the Dirac model. For these calculations, we evaluate the dynamic polarizabilities of the above atomic systems very accurately by evaluating the transition matrix elements employing relativistic many-body methods and using the experimental values of the excitation energies. The dispersion coefficients are given as functions of the separation distance of an atomic system from the graphene layer and the ambiance temperature during the interactions. For easy extraction of these coefficients, we give a logistic fit to the functional forms of the dispersion coefficients in terms of the separation distances at room temperature.

  3. Improved thermoelectric performance in polycrystalline p-type Bi2Te3 via an alkali metal salt hydrothermal nanocoating treatment approach

    NASA Astrophysics Data System (ADS)

    Ji, Xiaohua; He, Jian; Su, Zhe; Gothard, Nick; Tritt, Terry M.

    2008-08-01

    We report herein a proof-of-principle study of grain boundary engineering in the polycrystalline p-type Bi2Te3 system. Utilizing the recently developed hydrothermal nanocoating treatment technique, we fabricated an alkali-metal(s)-containing surface layer on the p-Bi2Te3 bulk grain, which in turn became part of the grain boundary upon hot pressing densification. Compared to the untreated bulk reference, the dimensionless figure of merit ZT has been improved by ˜30% in the Na-treated sample chiefly due to the reduced thermal conductivity, and ˜38% in the Rb-treated sample mainly owing to the improved power factor. The grain boundary phase provides a new avenue by which one can potentially decouple the otherwise inter-related electrical resistivity, Seebeck coefficient, and thermal conductivity within one thermoelectric material.

  4. Atomic arrangement and electron band structure of Si(1 1 1)-ß-√3 x √3-Bi reconstruction modified by alkali-metal adsorption: ab initio study.

    PubMed

    Eremeev, S V; Chukurov, E N; Gruznev, D V; Zotov, A V; Saranin, A A

    2015-08-01

    Using ab initio calculations, atomic structure and electronic properties of Si(1 1 1)[Formula: see text]-Bi surface modified by adsorption of 1/3 monolayer of alkali metals, Li, Na, K, Rb and Cs, have been explored. Upon adsorption of all metals, a similar atomic structure develops at the surface where twisted chained Bi trimers are arranged into a honeycomb network and alkali metal atoms occupy the [Formula: see text] sites in the center of each honeycomb unit. Among other structural characteristics, the greatest variation concerns the relative heights at which alkali metals reside with respect to Bi-trimer layer. Except for Li, the other metals reside higher than Bi layer and their heights increase with atomic number. All adsorbed surface structures display similar electron band structures of which the most essential feature is metallic surface-state band with a giant spin splitting. This electronic property allows one to consider the Si(1 1 1)[Formula: see text]-Bi surfaces modified by alkali metal adsorption as a set of material systems showing promise for spintronic applications. PMID:26151642

  5. Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Delichere, P.

    1996-12-01

    Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminates, obtained by sol-gel techniques, with a different amount of sodium, and R equal to 2.1 and 6.1 respectively. LEIS experiments and electron microscopy demonstrate a different location of alkali metal ions in the first two series: in the Na-Pd/SiO{sub 2} catalysts sodium is distributed in a way which is not uniform on the support and on the palladium metal, which is partly decorated with Na ions, whereas in the Pd/natural-pumice series the palladium surface is sodium-free. The results on the third series of catalysts, Pd/model pumice, are not definitive on the basis of the LEIS and TEM analyses, but by FTIR study of CO and CO{sub 2} adsorption, the decoration of palladium by sodium ions could be excluded. The results confirm the importance of the alkali metal ion location in alkali-promoted palladium catalysts and open new possibilities in the design of palladium-supported catalysts by a better control of promoter location. 18 refs., 5 figs., 2 tabs.

  6. Nonlinear infrared generation in alkali metal vapors: Steady state susceptibilities and dynamic behavior. Effective relaxation rates and preliminary Raman gain predictions for the Cs system

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.

    1986-01-01

    Effective relaxation rates for atomic cesium pumped by doubled Alexandrite radiation are presented. Laser radiation levels are 8S 1/2 and 9S 1/2; resonance levels 3 = 8P 1/2 and 8P 1/2, respectively. In addition, Raman gain is represented in two graphs which plot chi per atom (10 to the -13 power) at Raman peak versus the infrared wave number per centimeter and the corresponding doubled Alexandrite wave number. One graph covers resonance level 8P, the other 9P; in both cases cesium is pumped with a peak pulse height of 0.5 MW in a 200 micron diameter spot size.

  7. Density change and viscous flow during structural relaxation of plasma-enhanced chemical-vapor-deposited silicon oxide films

    NASA Astrophysics Data System (ADS)

    Cao, Zhiqiang; Zhang, Xin

    2004-10-01

    The structural relaxation of plasma-enhanced chemical-vapor-deposited (PECVD) silane-based silicon oxide films during thermal cycling and annealing has been studied using wafer curvature measurements. These measurements, which determine stress in the amorphous silicon oxide films, are sensitive to both plastic deformation and density changes. A quantitative case study of such changes has been done based upon the experimental results. A microstructure-based mechanism elucidates seams as a source of density change and voids as a source of plastic deformation, accompanied by a viscous flow. This theory was then used to explain a series of experimental results that are related to thermal cycling as well as annealing of PECVD silicon oxide films including stress hysteresis generation and reduction and coefficient of thermal-expansion changes. In particular, the thickness effect was examined; PECVD silicon oxide films with a thickness varying from 1to40μm were studied, as certain demanding applications in microelectromechanical systems require such thick films serving as heat/electrical insulation layers.

  8. Structures of Hydrated Alkali Metal Cations, M+(H2O)nAr (m = Li, Na, K, rb and Cs, n = 3-5), Using Infrared Photodissociation Spectroscopy and Thermodynamic Analysis

    NASA Astrophysics Data System (ADS)

    Ke, Haochen; van der Linde, Christian; Lisy, James M.

    2014-06-01

    Alkali metal cations play vital roles in chemical and biochemical systems. Lithium is widely used in psychiatric treatment of manic states and bipolar disorder; Sodium and potassium are essential elements, having major biological roles as electrolytes, balancing osmotic pressure on body cells and assisting the electroneurographic signal transmission; Rubidium has seen increasing usage as a supplementation for manic depression and depression treatment; Cesium doped compounds are used as essential catalysts in chemical production and organic synthesis. Since hydrated alkali metal cations are ubiquitous and the basic form of the alkali metal cations in chemical and biochemical systems, their structural and thermodynamic properties serve as the foundation for modeling more complex chemical and biochemical processes, such as ion transport and ion size-selectivity of ionophores and protein channels. By combining mass spectrometry and infrared photodissociation spectroscopy, we have characterized the structures and thermodynamic properties of the hydrated alkali metal cations, i.e. M+(H2O)nAr, (M = Li, Na, K, Rb and Cs, n = 3-5). Ab initio calculations and RRKM-EE (evaporative ensemble) calculations were used to assist in the spectral assignments and thermodynamic analysis. Results showed that the structures of hydrated alkali metal cations were determined predominantly by the competition between non-covalent interactions, i.e. the water---water hydrogen bonding interactions and the water---cation electrostatic interactions. This balance, however, is very delicate and small changes, i.e. different cations, different levels of hydration and different effective temperatures clearly impact the balance.

  9. Electron Density Dropout Near Enceladus in the Context of Water-Vapor and Water-Ice

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Johnson, R. E.; Kaiser, M. L.; Wahlund, J.-E.; Waite, J. H., Jr.

    2009-01-01

    On 12 March 2008, the Cassini spacecraft made a close encounter with the Saturnian moon Enceladus, passing within 52 km of the moon. The spacecraft trajectory was intentionally-oriented in a southerly direction to create a close alignment with the intense water-dominated plumes emitted from the south polar region. During the passage, the Cassini Radio and Plasma Wave System (RPWS) detected two distinct radio signatures: 1) Impulses associated with small water-ice dust grain impacts and 2) an upper hybrid (UH) resonance emission that both intensified and displayed a sharp frequency decrease in the near-vicinity of the moon. The frequency decrease of the UH emission is associated with an unexpectedly sharp decrease in electron density from approximately 90 el/cubic cm to below 20 el/cubic cm that occurs on a time scale of a minute near the closest encounter with the moon. In this work, we consider a number of scenarios to explain this sharp electron dropout, but surmise that electron absorption by ice grains is the most likely process.

  10. Spin-polarized lithium diffusion in a glass hot-vapor cell

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kiyoshi

    2016-08-01

    We report diffusion coefficients of optically pumped lithium atoms in helium buffer gas. The free-induction decay and the spin-echo signals of ground-state atoms were optically detected in an external magnetic field with the addition of field gradient. Lithium hot vapor was produced in a borosilicate-glass cell at a temperature between 290 and 360°C. The simple setup using the glass cells enabled lithium atomic spectroscopy in a similar way to other alkali-metal atoms and study of the collisional properties of lithium atoms in a hot-vapor phase.

  11. Preparation of FePt Magnetic Nanoparticle Film by Plasma Chemical Vapor Deposition for Ultrahigh Density Data Storage Media

    NASA Astrophysics Data System (ADS)

    Matsui, Isao

    2006-10-01

    We prepared an FePt nanoparticle film for magnetic storage media using 13.56 MHz glow-discharge plasma. Vapors of metal organics, namely biscyclopentadienyl iron (ferrocene) for Fe and (methylcyclopentadienyl)trimethyl platinum for Pt, were introduced into a capacitively coupled flow—through plasma chamber, which consisted of a shower head RF electrode and a grounded orifice plate electrode. Synthesized nanoparticles were directly collected onto a transmission electron microscope (TEM) grid or MgO substrate placed just below the grounded orifice electrode. TEM images showed two kinds of particles, one of which was nanometer sized and isolated and the other appeared as a coagulate of small particles. The diameter of the coagulated particle was larger than 10 nm. Nanometer size particles were separated and deposited on MgO substrate by adjusting the gas flow rate through the grounded orifice plate. The magnetization of the FePt nanoparticle film was evaluated by magneto-optical Kerr effect (MOKE) spectroscopy. As-synthesized nanoparticles did not exhibit a loop-shape magnetization curve. Annealing in atmospheric hydrogen was conducted to transform crystal from fcc structure to fct L10 ordered structure. The higher annealing temperature resulted in the more ordered L10 phase formation and the larger coercivity. A sample annealed at 750 °C exhibited a room temperature coercivity of 10 kOe. Also, it was confirmed that nanoparticle film density is critical to the magnetization.

  12. Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation

    SciTech Connect

    Majumder, A.; Dikshit, B.; Bhatia, M. S.; Mago, V. K.

    2008-09-15

    State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data.

  13. Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation.

    PubMed

    Majumder, A; Dikshit, B; Bhatia, M S; Mago, V K

    2008-09-01

    State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data. PMID:19044405

  14. Conformation of Alkali Metal Ion-Benzo-12-Crown-4 Complexes Investigated by UV Photodissociation and UV-UV Hole-Burning Spectroscopy.

    PubMed

    Inokuchi, Yoshiya; Nakatsuma, Maki; Kida, Motoki; Ebata, Takayuki

    2016-08-18

    We measure UV photodissociation (UVPD) spectra of benzo-12-crown-4 (B12C4) complexes with alkali metal ions, M(+)·B12C4 (M = Li, Na, K, Rb, and Cs), in the 36300-37600 cm(-1) region. Thanks to the cooling of ions to ∼10 K, all the M(+)·B12C4 complexes show sharp vibronic bands in this region. For UV-UV hole-burning (HB) spectroscopy, we first check if our experimental system works well by observing UV-UV HB spectra of the K(+) complex with benzo-18-crown-6 (B18C6), K(+)·B18C6. In the UV-UV HB spectra of the K(+)·B18C6 complex, gain signals are also observed; these are due to vibrationally hot K(+)·B18C6 complex produced by the UV excitation of cold K(+)·B18C6 complex. Then we apply UV-UV HB spectroscopy to the M(+)·B12C4 complexes, and only one conformer is found for each complex except for the Li(+) complex, which has two conformers. The vibronic structure around the origin band of the UVPD spectra is quite similar for all the complexes, indicating close resemblance of the complex structure. The most stable structures calculated for the M(+)·B12C4 (M = Li, Na, K, Rb, and Cs) complexes also have a similar conformation among them, which coincides with the UVPD results. In these conformers the metal ions are too big to be included in the B12C4 cavity, even for the Li(+) ion. In solution, it was reported that 12-crown-4 (12C4) shows the preference of Na(+) ion among alkali metal ions. From the similarity of the structure for the M(+)·B12C4 complexes, it is suggested that the solvation of free metal ions, not of the M(+)·12C4 complexes, may lead to the selectivity of Na(+) ion for 12C4 in solution. PMID:27459367

  15. Structural changes of polyacids initiated by their neutralization with various alkali metal hydroxides. Diffusion studies in poly(acrylic acid)s.

    PubMed

    Masiak, Michal; Hyk, Wojciech; Stojek, Zbigniew; Ciszkowska, Malgorzata

    2007-09-27

    The changes in the three-dimensional structure of the poly(acrylic acid), PAA, induced by incorporation of various alkali-metal counterions have been evaluated by studying diffusion of an uncharged probe (1,1'-ferrocenedimethanol) in the polymeric media. The studies are supported by the measurements of conductivity and viscosity of the polymeric media. Solutions of linear PAA of four different sizes (molecular weights: 450,000, 750,000, 1,250,000, 4,000,000) were neutralized with hydroxides of alkali metals of group 1 of the periodic table (Li, Na, K, Rb, Cs) to the desired neutralization degree. The transport properties of the obtained polyacrylates were monitored by measuring the changes in the probe diffusion coefficient during the titration of the polyacids. The probe diffusivity was determined from the steady-state current of the probe voltammetric oxidation at disk microelectrodes. Diffusivity of the probe increases with the increase in the degree of neutralization and with the increase in viscosity. It reaches the maximum value at about 60-80% of the polyacid neutralization. The way the probe diffusion coefficients change is similar in all polyacid solutions and gels. The increase in the size of a metal cation causes, in general, an enhancement in the transport of probe molecules. The biggest differences in the probe diffusivities are between lithium and cesium polyacrylates. The differences between the results obtained for cesium and rubidium are not statistically significant due to lack of good precision of the voltammetric measurements. The measurements of the electric conductivity of polyacrylates and the theoretical predictions supplemented the picture of electrostatic interactions between the polyanionic chains and the metal cations of increasing size. In all instances of the PAAs, the viscosity of the solutions rapidly increases in the 0-60% range of neutralization and then becomes constant in the 60-100% region. With the exception of the shortest

  16. Superconductivity of {open_quotes}conducting polymer-fullerene alkali metal{close_quotes} composites: Dreams and realities

    SciTech Connect

    Zakhidov, A.A.; Yoshino, K.

    1996-10-01

    Composites of fullerene C{sub 60} with conjugated polymers (CP) like polyalkylthiophene (PAT) and polyphenylene vinylene derivative (OO-PPV) have earlier demonstrated intensive charge transfer upon photoexcitation. Doping of CP/C{sub 60} composites by A metal vapors (A=K,Rb) is aimed at C{sub 60} induced SC, in which electrons of CP chains may participate in SC pairing, induced via hybridization with C{sub 60} molecules. We have found an SC phase experimentally both in PAT. (C{sub 60}) {sub y}K{sub x} and OO.PPV (C{sub 60}){sub y}K{sub x} by a sensitive method of low field microwave absorption (LFMA), and proved by SQUID. The SCT{sub c} ranges from 12 to 17 K, depending on y and x. This SC phase shows a granular behavior in LFMA, and thus originates from SC A{sub 3}C{sub 60} clusters weakly linked by Josephson junctions. True C{sub 60} induced SC might be masked by granular A{sub 3}C{sub 60}. Anomalous LFMA and paramagnetic Meissner effects observed in SQUID, indicate the existence of Josephson {pi}-junctions. CP is apparently involved in SC via spin carrying polarons P in CP chains, which play a role of {pi}-junctions. Strategies for further search of C{sub 60} induced SC are discussed.

  17. Experimental observation of electrochemical rate limitations affecting sodium ion-electron recombination at electrodes of the alkali metal thermoelectric converter at T about 1200 K

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Loveland, M. E.; Underwood, M. L.; Bankston, C. P.

    1988-01-01

    This paper considers a model of the internal impedances of thin porous Mo and W alkali metal thermoelectric converter (AMTEC), in which the kinetic parameters associated with the reaction of the beta-double-prime alumina solid electrolite (BASE)/porous metal/gas three-phase boundary can be evaluated. Impedance data in the frequency range 0.01-100,000 Hz were collected over a range of AMTEC cell operating voltages for small-area thin porous Mo and W electrodes, yielding apparent charge transfer resistances at a series of cell potentials/currents. The ohmic resistance in the AMTEC cell could be broken down and characterized with three parameters: the BASE ionic resistance, the electrode film sheet resistance, and the contact/lead resistance, all of which could be calculated or measured independently and used to calculate power curves in good agreement with observed power curves. It is shown that these calculations can be used to predict the properties of electrodes with optimized parameters or to detect enhanced transport modes.

  18. Coordination polymers based on diiron tetrakis(dithiolato) bridged by alkali metals, electrical bistability around room temperature, and strong antiferromagnetic coupling.

    PubMed

    Benmansour, Samia; Delgado, Esther; Gómez-García, Carlos J; Hernández, Diego; Hernández, Elisa; Martin, Avelino; Perles, Josefina; Zamora, Félix

    2015-03-01

    Coordination polymer chains have been formed by the direct reaction between HSC6H2Cl2SH and FeCl3·6H2O in the presence of an aqueous solution of the corresponding alkali-metal hydroxide (M = Li, Na, and K) or carbonate (M = Rb and Cs). The structures consist of dimeric [Fe2(SC6H2Cl2S)4](2-) entities bridged by [M2(THF)4] [M = K (1), Rb (2), and Cs (3); THF = tetrahydrofuran] or {[Na2(μ-H2O)2(THF)2] (5 and 5') units. The smaller size of the lithium atom yields an anion/cation ion-pair molecule, [Li(THF)4]2[Fe2(SC6H2Cl2S)4] (4), in which the dianionic moieties are held together by Cl···Cl interactions. Electrical characterization of these compounds shows a general semiconductor behavior in which the conductivity and activation energies are mainly determined by the M-Cl and M-S bond distances. Compounds 1 and 5' are interesting examples of bistability showing reversible transitions centered at ca. 350 and 290 K with very large hysteresis of ca. 60 and 35 K, respectively. All of these compounds exhibit intradimer strong antiferromagnetic Fe···Fe interactions. PMID:25667965

  19. Alkali-Metal-Mediated Magnesiations of an N-Heterocyclic Carbene: Normal, Abnormal, and "Paranormal" Reactivity in a Single Tritopic Molecule.

    PubMed

    Martínez-Martínez, Antonio J; Fuentes, M Ángeles; Hernán-Gómez, Alberto; Hevia, Eva; Kennedy, Alan R; Mulvey, Robert E; O'Hara, Charles T

    2015-11-16

    Herein the sodium alkylmagnesium amide [Na4Mg2(TMP)6(nBu)2] (TMP=2,2,6,6-tetramethylpiperidide), a template base as its deprotonating action is dictated primarily by its 12 atom ring structure, is studied with the common N-heterocyclic carbene (NHC) IPr [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Remarkably, magnesiation of IPr occurs at the para-position of an aryl substituent, sodiation occurs at the abnormal C4 position, and a dative bond occurs between normal C2 and sodium, all within a 20 atom ring structure accommodating two IPr(2-). Studies with different K/Mg and Na/Mg bimetallic bases led to two other magnesiated NHC structures containing two or three IPr(-) monoanions bound to Mg through abnormal C4 sites. Synergistic in that magnesiation can only work through alkali-metal mediation, these reactions add magnesium to the small cartel of metals capable of directly metalating a NHC. PMID:26417985

  20. Complete-velocity-range description of negative-ion conversion of neutral atoms on an alkali-metal-halide surface under grazing geometry

    NASA Astrophysics Data System (ADS)

    Zhou, Hu; Zhou, Wang; Zhang, Meixiao; Zhou, Lihua; Ma, Yulong; Wang, Guangyi; Wu, Yong; Li, Bowen; Chen, Ximeng

    2016-06-01

    We propose a simple theoretical approach to consider negative-ion conversion of neutral atoms grazing on alkali-metal-halide crystal surfaces over the complete velocity range. The conversion process is viewed as a series of successive binary collisions between the projectile and the negatively charged sites on the surface along their trajectories due to localization of valence-band electrons at the anionic sites of the crystal. Conversion from F0 to F- via grazing scattering in LiF(100) and KI(100) is demonstrated with this model, which incorporates the key factors of image interaction and Mott-Littleton polarization interaction for electron capture. It also incorporates the decrease in the electron affinity due to Coulomb barrier tunneling of large-velocity negative ions to the vacuum level near surface anion sites. The pronounced differences in the efficiency of F- formation at LiF(100) and KI(100) surfaces are well explained by the proposed model. The relative efficiency and related saturation of the negative-ion formation for LiF and KI crystals compare well with experimental results.

  1. Structural phase stability, electronic structure and mechanical properties of alkali metal hydrides AMH4 (A=Li, Na; M=B, AL)

    NASA Astrophysics Data System (ADS)

    Santhosh, M.; Rajeswarapalanichamy, R.

    2016-01-01

    The structural stability of Alkali metal hydrides AMH4 (A=Li, Na; M=B, Al) is analyzed among the various crystal structures, namely hexagonal (P63mc), tetragonal (P42/nmc), tetragonal (P-421c), tetragonal (I41/a), orthorhombic (Pnma) and monoclinic (P21/c). It is observed that, orthorhombic (Pnma) phase is the most stable structure for LiBH4, monoclinic (P21/c) for LiAlH4, tetragonal (P42/nmc) for NaBH4 and tetragonal (I41/a) for NaAlH4 at normal pressure. Pressure induced structural phase transitions are observed in LiBH4, LiAlH4, NaBH4 and NaAlH4 at the pressures of 4 GPa, 36.1 GPa, 26.5 GPa and 46 GPa respectively. The electronic structure reveals that these metal hydrides are wide band gap insulators. The calculated elastic constants indicate that these metal hydrides are mechanically stable at normal pressure.

  2. Ion chromatography with the indirect ultraviolet detection of alkali metal ions and ammonium using imidazolium ionic liquid as ultraviolet absorption reagent and eluent.

    PubMed

    Liu, Yong-Qiang; Yu, Hong

    2016-08-01

    Indirect ultraviolet detection was conducted in ultraviolet-absorption-agent-added mobile phase to complete the detection of the absence of ultraviolet absorption functional group in analytes. Compared with precolumn derivatization or postcolumn derivatization, this method can be widely used, has the advantages of simple operation and good linear relationship. Chromatographic separation of Li(+) , Na(+) , K(+) , and NH4 (+) was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid/organic solvent as the mobile phase, in which imidazolium ionic liquids acted as ultraviolet absorption reagent and eluting agent. The retention behaviors of four kinds of cations are discussed, and the mechanism of separation and detection are described. The main factors influencing the separation and detection were the background ultraviolet absorption reagent and the concentration of hydrogen ion in the ion chromatography-indirect ultraviolet detection. The successful separation and detection of Li(+) , Na(+) , K(+) , and NH4 (+) within 13 min was achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.02, 0.11, 0.30, and 0.06 mg/L, respectively. A new separation and analysis method of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection method was developed, and the application range of ionic liquid was expanded. PMID:27377245

  3. Theoretical study on the ground state of the polar alkali-metal-barium molecules: potential energy curve and permanent dipole moment.

    PubMed

    Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

    2015-01-21

    In this paper, we systematically investigate the electronic structure for the (2)Σ(+) ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained. PMID:25612710

  4. Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment

    SciTech Connect

    Gou, Dezhi; Kuang, Xiaoyu Gao, Yufeng; Huo, Dongming

    2015-01-21

    In this paper, we systematically investigate the electronic structure for the {sup 2}Σ{sup +} ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained.

  5. Effects of Multiple Argon Tagging in Alkali Metal M^+H_2OAr_n and M^+D_2OAr_n Studied by Irpd Spectroscopy

    NASA Astrophysics Data System (ADS)

    van der Linde, Christian; Ke, Haochen; Lisy, James M.

    2014-06-01

    Metal ions play important roles in biologically processes. Among these, alkali metal ions are of great importance. Their solvation is one of the fundamental processes having great effect on their activity and has been in focus of research for many years. M^+H_2O cluster are a good model for microscopic solvation. However, modeling gas-phase cluster ions has been a challenge both experimentally and theoretically due to uncertainties in the temperature (or internal energy) of these species. The temperature depends primarily on the composition and method of preparation of the cluster ion. Infrared photodissociation spectroscopy in combination with argon tagging is a well suited tool to study these species. While argon tagging itself is a well established technique for lowering the temperature and sharpening spectral features, experiments with multiple attached Ar atoms are rare. The influence of up to three Ar atoms on cluster temperature, vibrational band origins and rotational constants will be discussed for M = Na, K, Rb and Cs. The structure, arising from rotation of the water subunit, of the asymmetric bands will be analyzed in detail. Many spectra show broadening/splitting of features and an unusual intensity distribution for features associated especially to transitions involving the |K|=1 level. The influence of a low barrier, hindering rotation of the water subunit within the cluster, will be discussed.

  6. Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment

    NASA Astrophysics Data System (ADS)

    Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

    2015-01-01

    In this paper, we systematically investigate the electronic structure for the 2Σ+ ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained.

  7. Uranium Metalla-Allenes with Carbene Imido R2 C=U(IV) =NR' Units (R=Ph2 PNSiMe3 ; R'=CPh3 ): Alkali-Metal-Mediated Push-Pull Effects with an Amido Auxiliary.

    PubMed

    Lu, Erli; Tuna, Floriana; Lewis, William; Kaltsoyannis, Nikolas; Liddle, Stephen T

    2016-08-01

    We report uranium(IV)-carbene-imido-amide metalla-allene complexes [U(BIPM(TMS) )(NCPh3 )(NHCPh3 )(M)] (BIPM(TMS) =C(PPh2 NSiMe3 )2 ; M=Li or K) that can be described as R2 C=U=NR' push-pull metalla-allene units, as organometallic counterparts of the well-known push-pull organic allenes. The solid-state structures reveal that the R2 C=U=NR' units adopt highly unusual cis-arrangements, which are also reproduced by gas-phase theoretical studies conducted without the alkali metals to remove their potential structure-directing roles. Computational studies confirm the double-bond nature of the U=NR' and U=CR2 interactions, the latter increasingly attenuated by potassium then lithium when compared to the hypothetical alkali-metal-free anion. Combined experimental and theoretical data show that the push-pull effect induced by the alkali metal cations and amide auxiliary gives a fundamental and tunable structural influence over the C=U(IV) =N units. PMID:27403746

  8. Density distributions of OH, Na, water vapor, and water mist in atmospheric-pressure dc helium glow plasmas in contact with NaCl solution

    NASA Astrophysics Data System (ADS)

    Sasaki, Koichi; Ishigame, Hiroaki; Nishiyama, Shusuke

    2015-07-01

    This paper reports the density distributions of OH, Na, water vapor and water mist in atmospheric-pressure dc helium glow plasmas in contact with NaCl solution. The densities of OH, Na and H2O had different spatial distributions, while the Na density had a similar distribution to mist, suggesting that mist is the source of Na in the gas phase. When the flow rate of helium toward the electrolyte surface was increased, the distributions of all the species densities concentrated in the neighboring region to the electrolyte surface more significantly. The densities of all the species were sensitive to the electric polarity of the power supply. In particular, we never detected Na and mist when the electrolyte worked as the anode of the dc discharge. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  9. Trends in alkali metal hydrosulfides: A combined Fourier transform microwave/millimeter-wave spectroscopic study of KSH (X~1A')

    NASA Astrophysics Data System (ADS)

    Bucchino, M. P.; Sheridan, P. M.; Young, J. P.; Binns, M. K. L.; Ewing, D. W.; Ziurys, L. M.

    2013-12-01

    The pure rotational spectrum of KSH (tilde X1A') has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) techniques. This work is the first gas-phase experimental study of this molecule and includes spectroscopy of KSD as well. In the millimeter-wave system, KSH was synthesized in a DC discharge from a mixture of potassium vapor, H2S, and argon; a discharge-assisted laser ablation source, coupled with a supersonic jet expansion, was used to create the species in the FTMW instrument. Five and three rotational transitions in the range 3-57 GHz were recorded with the FTMW experiment for KSH and KSD, respectively, in the Ka = 0 component; in these data, potassium quadrupole hyperfine structure was observed. Five to six transitions with Ka = 0-5 were measured in the mm-wave region (260-300 GHz) for the two species. The presence of multiple asymmetry components in the mm-wave spectra indicates that KSH has a bent geometry, in analogy to other alkali hydrosulfides. The data were analyzed with an S-reduced asymmetric top Hamiltonian, and rotational, centrifugal distortion, and potassium electric quadrupole coupling constants were determined for both isotopolgues. The r0 geometry for KSH was calculated to be rS-H = 1.357(1) Å, rK-S = 2.806(1) Å, and θM-S-H (°) = 95.0 (1). FTMW measurements were also carried out on LiSH and NaSH; metal electric quadrupole coupling constants were determined for comparison with KSH. In addition, ab initio computations of the structures and vibrational frequencies at the CCSD(T)/6-311++G(3df,2pd) and CCSD(T)/aug-cc-pVTZ levels of theory were performed for LiSH, NaSH, and KSH. Overall, experimental and computational data suggest that the metal-ligand bonding in KSH is a combination of electrostatic and covalent forces.

  10. Trends in alkali metal hydrosulfides: a combined Fourier transform microwave/millimeter-wave spectroscopic study of KSH (X1A').

    PubMed

    Bucchino, M P; Sheridan, P M; Young, J P; Binns, M K L; Ewing, D W; Ziurys, L M

    2013-12-01

    The pure rotational spectrum of KSH (X(1)A') has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) techniques. This work is the first gas-phase experimental study of this molecule and includes spectroscopy of KSD as well. In the millimeter-wave system, KSH was synthesized in a DC discharge from a mixture of potassium vapor, H2S, and argon; a discharge-assisted laser ablation source, coupled with a supersonic jet expansion, was used to create the species in the FTMW instrument. Five and three rotational transitions in the range 3-57 GHz were recorded with the FTMW experiment for KSH and KSD, respectively, in the K(a) = 0 component; in these data, potassium quadrupole hyperfine structure was observed. Five to six transitions with K(a) = 0-5 were measured in the mm-wave region (260-300 GHz) for the two species. The presence of multiple asymmetry components in the mm-wave spectra indicates that KSH has a bent geometry, in analogy to other alkali hydrosulfides. The data were analyzed with an S-reduced asymmetric top Hamiltonian, and rotational, centrifugal distortion, and potassium electric quadrupole coupling constants were determined for both isotopolgues. The r0 geometry for KSH was calculated to be r(S-H) = 1.357(1) Å, r(K-S) = 2.806(1) Å, and θ(M-S-H) (°) = 95.0 (1). FTMW measurements were also carried out on LiSH and NaSH; metal electric quadrupole coupling constants were determined for comparison with KSH. In addition, ab initio computations of the structures and vibrational frequencies at the CCSD(T)/6-311++G(3df,2pd) and CCSD(T)/aug-cc-pVTZ levels of theory were performed for LiSH, NaSH, and KSH. Overall, experimental and computational data suggest that the metal-ligand bonding in KSH is a combination of electrostatic and covalent forces. PMID:24320380

  11. Influence of density on N-H bond stretch vibration in plasma enhanced chemical vapor deposited SiN{sub x}:H

    SciTech Connect

    Dekkers, H. F. W.; Pourtois, G.; Srinivasan, Nagendra Babu

    2010-01-04

    The infrared absorption of hydrogenated silicon nitride (SiN{sub x}:H) films provides information about the average configuration of covalent bonds in the film. In plasma enhanced chemical vapor deposited SiN{sub x}:H, the absorption spectrum of the N-H bonds shows both a systematic shift and a tailing toward lower frequency with the increase in the film density. First-principles computations of N-H vibrations show an increased degree of anharmonicity when the H site is weakly interacting with a second neighboring N atom. This interaction becomes more pronounced in films with higher density, which consequently shifts the vibrational spectrum down.

  12. Effect of long anneals on the densities of threading dislocations in GaN films grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, Z. T.; Xu, K.; Guo, L. P.; Yang, Z. J.; Su, Y. Y.; Yang, X. L.; Pan, Y. B.; Shen, B.; Zhang, H.; Zhang, G. Y.

    2006-09-01

    Effect of long anneals on densities of different types of threading dislocations (TDs) in GaN films grown onto sapphire substrate by metal-organic chemical vapor deposition was investigated by high-resolution X-ray diffraction. The results showed that the densities of both types of TDs changed obviously but oppositely, and residual stress in the GaN films was relaxed by generating edge-type TDs instead of screw-type TDs. The results obtained from chemical etching experiments and grazing-incidence X-ray diffraction (GIXRD) also supported the proposed defect structure evolution.

  13. Adsorption of Ne on alkali surfaces studied with a density functional theory.

    PubMed

    Sartarelli, Salvador A; Szybisz, Leszek; Urrutia, Ignacio

    2009-01-01

    A density functional formalism is applied to investigate the wetting behavior of Ne adsorbed on planar substrates. The study is performed over the complete range of temperatures spanned from the triple point T_{t} up to the critical one T_{c} . For this purpose, an effective attractive pair potential was built on the basis of a separation procedure. This approach yields a good description of properties of the liquid-vapor interface at coexistence in the whole range of temperatures T_{t} < or = T < or = T_{c} . The adsorption of Ne on alkali metals and the alkaline-earth metal Mg is analyzed. This sequence of substrates exhibit increasing attractive strength leading to a variety of wetting situations throughout the interval T_{t}<-->T_{c} . A comparison with experimental data and other microscopic calculations is done. The predictions of a simple model are discussed. For NeRb we were able to resolve prewetting lines. Results obtained from a density functional are reported for NeK and NeMg . In the case of the latter system the interesting behavior occurs close to T_{t} . According to our results, Ne wets surfaces of Na and Li, and this statement is in agreement with the whole picture of the analyzed substrates. PMID:19257041

  14. Unified picture of the doping dependence of superconducting transition temperatures in alkali metal/ammonia intercalated FeSe

    NASA Astrophysics Data System (ADS)

    Guterding, Daniel; Jeschke, Harald O.; Hirschfeld, P. J.; Valentí, Roser

    2015-01-01

    In the recently synthesized Lix(NH2)y(NH3)zFe2Se2 family of iron chalcogenides, a molecular spacer consisting of lithium ions, lithium amide, and ammonia separates the layers of FeSe. It has been shown that upon variation of the chemical composition of the spacer layer, superconducting transition temperatures can reach Tc˜44 K , but the relative importance of the layer separation and effective doping to the Tc enhancement is currently unclear. Using state of the art band structure unfolding techniques, we construct eight-orbital models from ab initio density functional theory calculations for these materials. Within an RPA spin-fluctuation approach, we show that the electron doping enhances the superconducting pairing, which is of s± symmetry and explain the experimentally observed limit to Tc in the molecular spacer intercalated FeSe class of materials.

  15. Density functional studies of the formation of nitrous acid from the reaction of nitrogen dioxide and water vapor

    SciTech Connect

    Chou, A.; Li, Z.; Tao, F.M.

    1999-09-30

    Nitrous acid (HONO) has long been recognized as an important trace gas in the troposphere where its rapid photolysis represents a significant source of hydroxy (OH) radicals. During the night, HONO has been observed to accumulate to concentrations up to 15 ppb, and this accumulation of HONO has a profound impact on the daytime chemistry of the troposphere. Reaction mechanisms for the production of nitrous acid (HONO ) from the homogeneous gas-phase hydrolysis of nitrogen dioxide (NO{sub 2}) are examined by density functional theory calculations. The molecular structures and energies of the NO{sub 2}-(H{sub 2}O){sub n} (n = 1, 2, 3) and N{sub 2}O{sub 4}-(H{sub 2} O){sub n}(n = 1, 2) systems corresponding to the stationary points on the potential energy surface along the reaction pathways are calculated using the B3LYP method with the 6-311+G(2d,p) basis set. These reaction pathways represent the homogeneous hydrolysis of NO{sub 2} or N{sub 2}O{sub 4} with a varying number of water (H{sub 2}O) molecules. The reactions of NO{sub 2} with water produce HONO, along with the OH radical which was postulated to combine in the next step with a second NO{sub 2} to form nitric acid (HNO{sub 3}). The simple NO{sub 2} + H{sub 2}O bimolecular reaction leads to the highly unstable OH radical which reacts reversibly with HONO without an energy barrier. The introduction of single solvating H{sub 2}O molecule appears to stabilize the transition state as well as an intermediate that contains the OH radical. However, the energy barrier is found to be near 30 kcal mol{sup {minus}1} and is not affected by multiple additional H{sub 2}O molecules. On the other hand, the reaction of N{sub 2}O{sub 4} with water lead directly to HONO and HNO{sub 3}. the energy barrier for the N{sub 2}O{sub 4} reaction is above 30 kcal mol{sup {minus}1} and is also unaffected by additional H{sub 2}O molecules. The study demonstrates that the gas-phase hydrolysis of NO{sub 2} or N{sub 2}O{sub 4} is

  16. Surface charge dynamics and OH and H number density distributions in near-surface nanosecond pulse discharges at a liquid / vapor interface

    NASA Astrophysics Data System (ADS)

    Winters, Caroline; Petrishchev, Vitaly; Yin, Zhiyao; Lempert, Walter R.; Adamovich, Igor V.

    2015-10-01

    The present work provides insight into surface charge dynamics and kinetics of radical species reactions in nanosecond pulse discharges sustained at a liquid-vapor interface, above a distilled water surface. The near-surface plasma is sustained using two different discharge configurations, a surface ionization wave discharge between two exposed metal electrodes and a double dielectric barrier discharge. At low discharge pulse repetition rates (~100 Hz), residual surface charge deposition after the discharge pulse is a minor effect. At high pulse repetition rates (~10 kHz), significant negative surface charge accumulation over multiple discharge pulses is detected, both during alternating polarity and negative polarity pulse trains. Laser induced fluorescence (LIF) and two-photon absorption LIF (TALIF) line imaging are used for in situ measurements of spatial distributions of absolute OH and H atom number densities in near-surface, repetitive nanosecond pulse discharge plasmas. Both in a surface ionization wave discharge and in a double dielectric barrier discharge, peak measured H atom number density, [H] is much higher compared to peak OH number density, due to more rapid OH decay in the afterglow between the discharge pulses. Higher OH number density was measured near the regions with higher plasma emission intensity. Both OH and especially H atoms diffuse out of the surface ionization wave plasma volume, up to several mm from the liquid surface. Kinetic modeling calculations using a quasi-zero-dimensional H2O vapor / Ar plasma model are in qualitative agreement with the experimental data. The results demonstrate the experimental capability of in situ radical species number density distribution measurements in liquid-vapor interface plasmas, in a simple canonical geometry that lends itself to the validation of kinetic models.

  17. The influence of alkali metal ions in the chemisorption of CO and CO{sub 2} on supported palladium catalysts: A Fourier transform infrared spectroscopic study

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Martin, G.A.

    1996-12-01

    Two series of palladium-based catalysts were compared on the basis of the adsorption of CO and CO{sub 2}, monitored by Fourier transform infrared spectroscopy. The first series is represented by a silica-supported palladium catalyst and by some catalysts derived from it by addition of different amounts of sodium ion 0 {le} R {le} 25.6, where R is the atomic ratio Na/Pd. The second series consists of palladium catalysts supported on {open_quotes}model{close_quotes} and natural pumices. The model pumices, obtained by sol-gel techniques, are silico-aluminates containing variable amounts of sodium so that the corresponding Pd catalysts have an R value in the range 0{le}R{le}6.1. In the Pd/natural pumice catalysts, changes of the atomic ratio R{prime} = (Na + K)/Pd are achieved with different palladium loadings. Despite the analogous behaviour of the catalysts of both series when R=0, the presence of increasing alkali metal ions induces different behaviour towards the adsorption of CO. On increasing R in the Na-Pd/SiO{sub 2} series there is a progressive weakening of the C-O bond to produce eventually carbonates, whereas only a decrease of the amount of adsorbed CO occurs in the Pd/model pumice series (R{le}6.1). Furthermore, only physisorbed CO bands are observed in Pd/natural pumice catalysts (R{prime}{le}17). Different behaviour is also noticed towards the adsorption of CO{sub 2}: the equilibrium CO{sub 2}(gas){r_equilibrium}CO{sub ads}+O{sub ads} occurs in the Pd/SiO{sub 2} series, in contrast to the Pd/pumice series where only carbonate species on the surface of the support are detected. 83 refs., 12 figs., 4 tabs.

  18. Slow flows of a vapor-gas mixture with large density and temperature variations in the near-continuum regime

    NASA Astrophysics Data System (ADS)

    Laneryd, Carl-Johan Tor; Aoki, Kazuo; Takata, Shigeru

    2007-10-01

    A binary mixture of a vapor and a noncondensable gas in contact with the boundary made of the condensed phase (liquid or solid) of the vapor is considered in the following situation: the amount of the noncondensable gas contained in the system is of the same order of magnitude as that of the vapor; the temperature variation along the boundary may be large; the boundary is at rest, and there is no flow at infinity when an infinite domain is considered; and the Knudsen number is small (i.e., near-continuum regime). Slow steady flows (with Mach number of the order of Knudsen number, or equivalently, with Reynolds number of the order of unity) of the mixture, mainly caused by evaporation and condensation of the vapor on the boundary, are investigated on the basis of kinetic theory. The basic system used in this work is the fluid-dynamic-type system that was derived systematically from the Boltzmann system in a previous paper [S. Takata and K. Aoki, Transp. Theor. Stat. Phys. 30, 205 (2001); erratum, Transp. Theor. Stat. Phys. 31, 289 (2002)] in connection with the ghost effect, and it is solved numerically by a finite-volume method. Some additional computation using the direct simulation Monte Carlo method, based on the original Boltzmann system, is also performed for comparison. The behavior of the mixture in the continuum limit in which the Knudsen number vanishes is discussed with special interest in the ghost effect.

  19. Raman-Ramsey multizone spectroscopy in a pure rubidium vapor cell

    SciTech Connect

    Failache, H.; Lenci, L.; Lezama, A.

    2010-02-15

    In view of application to a miniaturized spectroscopy system, we consider an optical setup that splits a laser beam into several parallel narrow light sheets allowing an effective beam expansion and consequently longer atom-light interaction times. We analyze the multizone coherent population trapping (MZCPT) spectroscopy of alkali-metal-vapor atoms, without buffer gas, in the presence of a split light beam. We show that the MZCPT signal is largely insensitive to intensity broadening. Experimentally observed spectra are in qualitative agreement with the predictions of a simplified model that describes each spectrum as an integral over the atomic velocity distribution of Ramsey multizone spectra.

  20. Influence of the vapor flux on temperature, density, and abundance distributions in a multicomponent, porous, icy body

    NASA Technical Reports Server (NTRS)

    Benkhoff, J.; Huebner, W. F.

    1995-01-01

    We calculated the vapor flux of the icy components in the surface layer of a porous, short-period, Jupiter-class comet, in order to investigate the relationship of the observed relative molecular abundances in the coma with those in the nucleus. The model assumes a body containing one major ice component (H20) and up to three minor components of higher volatility (e.g., CO, CO2, CH3OH). The body's porous structure is modeled as a bundle of tubes with a given tortuosity and initially a constant pore diameter. The mass and energy equations for the different volatiles are solved simultaneously under appropiate boundary conditions. Heat is conducted by the matrix and carried by the vapors. The one-dimensional model includes radially inward and outward flowing vapor within the body, complete depletion of less volatile ices in outer layers, and recondensation of vapor in deeper, coller layers. As a result, we obtain the temperature and abundance distribution in the nucleus and the gas flux into the interior and into the coma for each of the volatiles at various positions in the orbit. The ratio of the gas flux of minor volatiles to that of H2) in the coma varies by several orders of magnitude throughout the orbit. Thus, the relative abundances of species observed in the coma are in most cases not the same as those in the nucleus. Results also indicate that it will be impossible to determine the relative abundances of ices more volatile than water from samples taken a few meters below the surface during a comet rendezvous mission. We made calculations for a wide range of different parameters, such as porosity, pore radius, and thermal conductivity of the matrix. To introduce the model we present typical results for a dust-free comet.

  1. Densities and vapor-liquid equilibria in binary mixtures formed by propyl methanoate + ethanol, + propan-1-ol, and + butan-1-ol at 160.0 kPa

    SciTech Connect

    Falcon, J.; Ortega, J.; Gonzalez, E.

    1996-07-01

    Densities and excess volumes were determined at 298.15 K for propyl methanoate + ethanol, + propan-1-ol, and + butan-1-ol. The results of those quantities were then correlated to get the concentrations of vapor-liquid equilibrium obtained isobarically at 160 kPa for the same mixtures. Two mixtures show azeotropes: for propyl methanoate (1) + ethanol (2), x{sub 1} = 0.443 at T = 358.7 K; and for propyl methanoate (1) + propan-1-ol (2), x{sub 1} = 0.762 at T = 368.2 K. The mixtures are thermodynamically consistent, and the predictions made using several group-contribution models are satisfactory.

  2. Densities of liquids and vapors in boiling NaCl-H2O solutions: a PVTx summary from 300° to 500°C

    USGS Publications Warehouse

    Bischoff, James L.

    1991-01-01

    Experimental data for densities of liquids and vapors on the two-phase surface of the system NaCl-H2O were compiled and evaluated to provide a complete summary between 300° and 500°C. The results are added to a previously published PTx summary compiled in the same manner to provide a PVTx summary of the present state of knowledge. Results are in table form of use to the understanding of two-phase behaviour in boiling hydrothermal systems and to theoretical modeling of this important system. 

  3. Growth of Horizontal Semiconducting SWNT Arrays with Density Higher than 100 tubes/μm using Ethanol/Methane Chemical Vapor Deposition.

    PubMed

    Kang, Lixing; Zhang, Shuchen; Li, Qingwen; Zhang, Jin

    2016-06-01

    Horizontally aligned semiconducting single-walled carbon nanotube (s-SWNT) arrays with a certain density are highly desirable for future electronic devices. However, obtaining s-SWNT arrays with simultaneously high purity and high density is extremely challenging. We report herein a rational approach, using ethanol/methane chemical vapor deposition, to grow SWNT arrays with a s-SWNT ratio over 91% and a density higher than 100 tubes/μm. In this approach, at a certain temperature, ethanol was fully thermally decomposed to feed carbon atoms for Trojan-Mo catalysts growing high density SWNT arrays, while the incomplete pyrolysis of methane provided appropriate active H radicals with the help of catalytic sapphire surface to inhibit metallic SWNT (m-SWNT) growth. The synergistic effect of ethanol/methane mixtures resulted in enriched semiconducting SWNTs and no obvious decrease in nanotube density due to their milder reactivity and higher controllability at suitable growth conditions. This work represents a step forward in large-area synthesis of high density s-SWNT arrays on substrates and demonstrates potential applications in scalable carbon nanotube electronics. PMID:27177360

  4. Syntheses and characterization of one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs)

    SciTech Connect

    Yohannan, Jinu P.; Vidyasagar, Kanamaluru

    2015-01-15

    Three new isostructural quaternary antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) have been synthesized by using alkali metal thiosulfate flux and structurally characterized by X-ray diffraction. Their structures contain A{sup +} ions around the [Sb{sub 2}Sn{sub 3}S{sub 10}]{sup 2−} chains, which are built from SbS{sub 3} pyramids, SnS{sub 6} octahedra and SnS{sub 4} tetrahedra. Raman and Mössbauer spectroscopic measurements corroborate the oxidation states and coordination environments of Sb(III) and Sn(IV). All three compounds are wide band gap semiconductors. Potassium compound undergoes partial exchange with strontium, cadmium and lead ions. - Graphical abstract: Syntheses, crystal structure, spectroscopic and partial ion-exchange studies of new one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) are described. - Highlights: • Syntheses of new alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs). • Wide band gap semiconductors with one-dimensional structure. • Topotactic partial exchange of K{sup +} ions of K{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} with Sr{sup 2+}, Cd{sup 2+} and Pb{sup 2+} ions.

  5. Correlation between the residual stress and the density of threading dislocations in GaN layers grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Barchuk, M.; Röder, C.; Shashev, Y.; Lukin, G.; Motylenko, M.; Kortus, J.; Pätzold, O.; Rafaja, D.

    2014-01-01

    The correlation between the residual stress and the density of threading dislocations was investigated in polar GaN layers that were grown by using hydride vapor phase epitaxy (HVPE) on three different GaN templates. The first template type was GaN grown on sapphire by metal-organic vapor phase epitaxy. The second template type was a closed GaN nucleation layer grown on sapphire by HVPE. The third template type was a non-closed GaN nucleation layer grown by HVPE, which formed isolated pyramids on the sapphire surface. The residual stress was determined using the combination of micro-Raman spectroscopy and modified sin2 ψ method. The interplanar spacings needed for the sin2 ψ method were obtained from the reciprocal space maps that were measured using high-resolution X-ray diffraction. The density of threading dislocations was concluded from the broadening of the reciprocal lattice points that was measured using high-resolution X-ray diffraction as well. The fitting of the reciprocal space maps allowed the character of the threading dislocations to be described quantitatively in terms of the fractions of edge and screw dislocations. It was found that the threading dislocation density increases with increasing compressive residual stress. Furthermore, the dislocation density and the residual stress decrease with increasing thickness of the GaN layers. The edge component of the threading dislocations was dominant in all samples. Still, some differences in the character of the dislocations were observed for different templates.

  6. Complex peroxyuranates. Synthesis and structural assessment of alkali-metal and ammonium dioxoperoxy(sulfato)aquouranates(VI), A/sub 2/(UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O)) (A = NH/sub 4/, Na), and alkali-metal and ammonium dioxoperoxy(oxalato)uranate(VI) hydrates, A/sub 2/(UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/). H/sub 2/O

    SciTech Connect

    Bhattacharjee, M.; Chaudhuri, M.K.; Purkayastha, R.N.D.

    1986-07-02

    Yellow microcrystalline alkali-metal and ammonium dioxoperoxy(sulfato)aquouranates(VI), A/sub 2/(UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O)) (A = NH/sub 4/, Na), and alkali-metal and ammonium dioxoperoxy(oxalato)uranate(VI) hydrates, A/sub 2/(UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/).H/sub 2/O (A = NH/sub 4/, Na, K), have been synthesized from the reaction of the product obtained by treating an aqueous solution of UO/sub 2/(NO/sub 3/)/sub 2/.6H/sub 2/O with alkali-metal or ammonium hydroxide, AOH, with 30% H/sub 2/O/sub 2/ and aqueous sulfuric acid and oxalic acid solution, respectively, in the mole ratio UO/sub 2/(NO/sub 3/)/sub 2/.6H/sub 2/O:H/sub 2/O/sub 2/:SO/sub 4//sup 2 -/ or C/sub 2/O/sub 4//sup 2 -/ of 1:111:5 or 1, at pH 6 maintained by the addition of the corresponding alkali-metal or ammonium hydroxide. Precipitation was completed by the addition of ethanol. IR and laser Raman spectra suggest that the O/sub 2//sup 2 -/ and SO/sub 4//sup 2 -/ ions in (UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O))/sup 2 -/ are bonded to the UO/sub 2//sup 2 +/ center in a bridging and in a monodentate manner, respectively, while both the O/sub 2//sup 2 -/ and C/sub 2/O/sub 4//sup 2 -/ ions in (UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/)/sup 2 -/ bind the uranyl center in bidentate chelated fashion. The complex peroxyuranates are diamagnetic and insoluble. The A/sub 2/(UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O)) compounds, unlike A/sub 2/(UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/).H/sub 2/O, are stable up to 110 /sup 0/C. Whereas H/sub 2/O in A/sub 2/(UO/sub 2/(O/sub 2/SO/sub 4/(H/sub 2/O)) is coordinated to the UO/sub 2//sup 2 +/ center, it occurs as a water of crystallization in the corresponding peroxy oxalato compounds. 20 references, 3 tables.

  7. Alkylated lariat ethers as solvent extraction reagents: Surveying the extraction of alkali metals by bis-t-octylbenzo-14-crown-4-acetic acid by use of potentiometric two-phase titration

    SciTech Connect

    Sachleben, R.A.; Moyer, B.A.; Case, F.I.; Garmon, S.A.

    1993-01-01

    Two-phase potentiometric titrimetry was used to survey the extraction of alkali metal cations from aqueous chloride solution by the lipophilic, ionizable lariat ether bis-(t-octylbenzo)-14-crown-4-acetic acid (BOB14C4AA) in o-xylene. Analysis of the data indicates that ion-exchange extraction by the crown-carboxylic acid at low loading (i.e., low conversion of BOB14C4AA to its salt form) is stronger for lithium ion than for the other alkali metals. Little or no selectivity occurs at high loadings. In comparison with the long-chain carboxylic acid 2-methyl-2-heptylnonanoic acid (HMHN), BOB14C4AA extracts lithium and sodium at significantly lower pH; in the loading range of 0.1 to 0.7, the pH shift is 1.4-1.8 pH units for sodium ion and 1.7-2.3 pH units for lithium ion. The titration data are interpreted in terms of aggregated organic-phase species. In the case of lithium extraction, clear evidence was found for a species in which neutral BOB14C4AA participates in the organic-phase complexation of the metal cation.

  8. New hypodiphosphates of the alkali metals: Synthesis, crystal structure and vibrational spectra of the hypodiphosphates(IV) M2[(H2P2O6)(H4P2O6)] (M=Rb and Cs)

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Wiegand, Thomas; Eckert, Hellmut; Gjikaj, Mimoza

    2012-10-01

    The new hypodiphosphates(IV) Rb2[(H2P2O6)(H4P2O6)] (1) and Cs2[(H2P2O6)(H4P2O6)] (2) were synthesized by soft chemistry reactions from aqueous solutions of hypophosphoric acid and the corresponding heavy alkali-metal carbonates. Their crystal structures were determined by single crystal X-ray diffraction. Both compounds crystallize isotypic in the triclinic space group P-1 with one formula unit in the unit cell. The structures are built up by discrete (H2P2O6)2- and (H4P2O6) units in staggered conformation for the P2O6 skeleton and the corresponding alkali-metal cations. In the (H2P2O6)2- ion the hydrogen atoms are in a "trans-trans" conformation. O·H-O hydrogen bonds between the (H2P2O6)2- and (H4P2O6) groups consolidate the structures into a three-dimensional network. The FT-Raman and 31P and 1H and MAS NMR spectra of the title compounds have been recorded and interpreted, especially with respect to their assignment to the (H2P2O6)2- and (H4P2O6) groups. Thermogravimetric data of 2 have been interpreted in terms of a thermal decomposition model.

  9. A multinuclear solid-state NMR study of alkali metal ions in tetraphenylborate salts, M[BPh4] (M = Na, K, Rb and Cs): what is the NMR signature of cation-pi interactions?

    PubMed

    Wu, Gang; Terskikh, Victor

    2008-10-16

    We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) conditions at 11.75 and 21.15 T, we have obtained the quadrupole coupling constants, C Q, and the chemical shift tensor parameters for the alkali metal ions in these compounds. We found that the observed quadrupole coupling constant for M (+) in M[BPh 4] is determined by a combination of nuclear quadrupole moment, Sternheimer antishielding factor, and unit cell dimensions. On the basis of a comparison between computed paramagnetic and diamagnetic contributions to the total chemical shielding values for commonly found cation-ligand interactions, we conclude that cation-pi interactions give rise to significantly lower paramagnetic shielding contributions than other cation-ligand interactions. As a result, highly negative chemical shifts are expected to be the NMR signature for cations interacting exclusively with pi systems. PMID:18816043

  10. Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter

    SciTech Connect

    Hunt, Thomas K.

    2001-09-10

    The Alkali Metal Thermal to Electric Converter (AMTEC) is a static energy conversion device that operates at high thermal to electric conversion efficiencies that are essentially independent of size, have reached 19% and are expected to reach 25% to 30% in 1997. AMTEC systems have been chosen by NASA and DOE for spacecraft applications and have considerable promise for a wide variety of terrestrial applications. Reduction of parasitic heat losses in AMTEC systems related to radiative heat transfer from the hot side to the condenser can make a substantial contribution to system efficiency. Through design, analysis and the fabrication and testing of cells and systems, the proposed program to develop a Directed Reflectivity Condenser (DRC) has investigated the feasibility of an improved AMTEC condenser component. Phase 1 work showed the potential for adding from 4% to 7% to overall system efficiency for identical operating conditions using the concept. A detailed thermal analysis of several DRC capped cell designs was carried out and some of the conditions under which a DRC, used as the condenser at an end cap of a cylindrical converter, can reduce thermal radiation related losses were determined. A model experimental converter was built and tested to compare DRC and planar condenser surfaces. The results of both analysis and experiment indicate that for moderate aspect ratios of a cylindrical, end condensed converter, the DRC can reduce overall thermal losses by up to 4%. The initial effort in Phase 2 extended the analysis to a novel 150 watt radial AMTEC cell design. This analysis indicated that for the effective aspect ratio of this new converter design, the system performance at the 100+ watt level was not significantly improved by use of a DRC type condenser surface. Further analyses however showed that for cylindrical, end-condensed converters, optimized for use with internal radiation shields, the use of DRC surfaces on the side walls of the converter could be

  11. The observed relationship between the south pole 225-GHz atmospheric opacity and the water vapor column density

    NASA Astrophysics Data System (ADS)

    Chamberlin, Richard A.; Bally, John

    1995-05-01

    We compare our previously reported measurements of South Pole 225 GHz atmospheric opacity, τ, to the column of precipitable water vapor ( PWV) which was derived from concurrent upper air soundings. From this comparison we found that τ=(2.8±0.1)×10-2+(6.9±0.2)×10-2× PWV with τ in units of nepers/airmass and PWV in units of mm of precipitable H2O. We compared our results to predictions from Grossman's AT atmospheric transparency model which is widely used in the radio astronomy community. The coefficient of the second term of the above relation, 0.069, was consistent with the predictions from the model; however, the first term, 0.028, which represents the dry air opacity, was about five to ten times larger than expected. Most of this discrepancy between the observed and the predicted dry air opacity can be accounted for by including contributions from continuum emission from N2 and O2 as is done in Liebe's MPM atmospheric model.

  12. X-ray determination of threading dislocation densities in GaN/Al{sub 2}O{sub 3}(0001) films grown by metalorganic vapor phase epitaxy

    SciTech Connect

    Kopp, Viktor S. Kaganer, Vladimir M.; Baidakova, Marina V.; Lundin, Wsevolod V.; Nikolaev, Andrey E.; Verkhovtceva, Elena V.; Yagovkina, Maria A.; Cherkashin, Nikolay

    2014-02-21

    Densities of a- and a+c-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films.

  13. Argon–germane in situ plasma clean for reduced temperature Ge on Si epitaxy by high density plasma chemical vapor deposition

    SciTech Connect

    Douglas, Erica A.; Sheng, Josephine J.; Verley, Jason C.; Carroll, Malcolm S.

    2015-06-04

    We found that the demand for integration of near infrared optoelectronic functionality with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation of low temperature germanium on silicon deposition processes. Our work describes the development of a high density plasma chemical vapor deposition process that uses a low temperature (<460 °C) in situ germane/argon plasma surface preparation step for epitaxial growth of germanium on silicon. It is shown that the germane/argon plasma treatment sufficiently removes SiOx and carbon at the surface to enable germanium epitaxy. Finally, the use of this surface preparation step demonstrates an alternative way to produce germanium epitaxy at reduced temperatures, a key enabler for increased flexibility of integration with CMOS back-end-of-line fabrication.

  14. Argon–germane in situ plasma clean for reduced temperature Ge on Si epitaxy by high density plasma chemical vapor deposition

    DOE PAGESBeta

    Douglas, Erica A.; Sheng, Josephine J.; Verley, Jason C.; Carroll, Malcolm S.

    2015-06-04

    We found that the demand for integration of near infrared optoelectronic functionality with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation of low temperature germanium on silicon deposition processes. Our work describes the development of a high density plasma chemical vapor deposition process that uses a low temperature (<460 °C) in situ germane/argon plasma surface preparation step for epitaxial growth of germanium on silicon. It is shown that the germane/argon plasma treatment sufficiently removes SiOx and carbon at the surface to enable germanium epitaxy. Finally, the use of this surface preparation step demonstrates anmore » alternative way to produce germanium epitaxy at reduced temperatures, a key enabler for increased flexibility of integration with CMOS back-end-of-line fabrication.« less

  15. High power densities from high-temperature materials interactions. [thermionic energy conversion and metallic fluid heat pipes

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1981-01-01

    Thermionic energy converters and metallic-fluid heat pipes are well suited to serve together synergistically. The two operating cycles appear as simple and isolated as their material problems seem forebodingly deceptive and complicated. Simplified equations verify material properties and interactions as primary influences on the operational effectiveness of both. Each experiences flow limitations in thermal emission and vaporization because of temperature restrictions redounding from thermophysicochemical stability considerations. Topics discussed include: (1) successful limitation of alkali-metal corrosion; (2) protection against external hot corrosive gases; (3) coping with external and internal vaporization; (4) controlling interfacial reactions and diffusion; and (5) meeting other thermophysical challenges; expansion matches and creep.

  16. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant

    PubMed Central

    2011-01-01

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  17. High critical current densities in YBa sub 2 Cu sub 3 O sub 7 minus x thin films formed by metalorganic chemical vapor deposition at 730 degree C

    SciTech Connect

    Li, Y.Q.; Zhao, J.; Chern, C.S.; Huang, W.; Kulesha, G.A.; Lu, P.; Gallois, B.; Norris, P.; Kear, B.; Cosandey, F. )

    1991-02-11

    YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} superconducting thin films with a critical current density of 2.3{times}10{sup 6} A/cm{sup 2} at 77.7 K and 0 T were prepared by a metalorganic chemical vapor deposition process. The films were formed {ital in} {ital situ} on LaAlO{sub 3} at a substrate temperature of 730 {degree}C in 2 Torr partial pressure of N{sub 2}O. Resistivity and magnetic susceptibility measurements of the as-deposited films show a sharp superconducting transition temperature of 89 K with a narrow width of less than 1 K. Critical current densities were measured by the dc transport method with a patterned bridge of 120 {mu}m{times}40 {mu}m. Both x-ray diffraction and high-resolution electron microscopy measurements indicate that films grew epitaxially with the {ital c} axis perpendicular to the surface of the substrate.

  18. Ab initio study of the adsorption, diffusion, and intercalation of alkali metal atoms on the (0001) surface of the topological insulator Bi{sub 2}Se{sub 3}

    SciTech Connect

    Ryabishchenkova, A. G. Otrokov, M. M.; Kuznetsov, V. M.; Chulkov, E. V.

    2015-09-15

    Ab initio study of the adsorption, diffusion, and intercalation of alkali metal adatoms on the (0001) step surface of the topological insulator Bi{sub 2}Se{sub 3} has been performed for the case of low coverage. The calculations of the activation energies of diffusion of adatoms on the surface and in van der Waals gaps near steps, as well as the estimate of diffusion lengths, have shown that efficient intercalation through steps is possible only for Li and Na. Data obtained for K, Rb, and Cs atoms indicate that their thermal desorption at high temperatures can occur before intercalation. The results have been discussed in the context of existing experimental data.

  19. Polarization and electronic excitation in nonreactive collisions: Basic formulation for quantum calculations of collisions between /sup 2/P-state alkali-metal atoms and H/sub 2/ or D/sub 2/

    SciTech Connect

    Baylis, W.E.; Pascale, J.; Rossi, F.

    1987-11-01

    The inelastic scattering of two structured systems: for example, an excited atom and a molecule: is considered in the case of nonreactive collisions. Explicit formulas are presented for cross sections corresponding to transitions between arbitrary eigenstates of the two isolated systems. These formulas are then used to derive cross sections for polarization transfer and multipole relaxation in one system when the other system is unpolarized. Both space-fixed and body-fixed formulations are given. Explicit matrix elements are worked out for interactions such as occur between model alkali-metal atoms and rigid-rotor diatomic molecules. An effective interaction method is also discussed and related to an adiabatic-state approach.

  20. Synthesis of Li{sub 2}PtH{sub 6} using high pressure: Completion of the homologous series A{sub 2}PtH{sub 6} (A=alkali metal)

    SciTech Connect

    Puhakainen, Kati; Stoyanov, Emil; Evans, Michael J.; Leinenweber, Kurt; Haeussermann, Ulrich

    2010-08-15

    Li{sub 2}PtH{sub 6}, the missing member of the complex transition metal hydride series A{sub 2}PtH{sub 6} (A=alkali metal), was prepared by reacting mixtures of LiH and Pt in the presence of BH{sub 3}NH{sub 3} as hydrogen source at pressures above 8 GPa. According to powder X-ray diffraction analysis, Li{sub 2}PtH{sub 6} is isostructural to its heavier homologues and crystallizes in the cubic K{sub 2}PtCl{sub 6} structure (space group Fm3-bar m, a=6.7681(3), Z=4). However, PtH{sub 6}{sup 2-} octahedral complexes in Li{sub 2}PtH{sub 6} approach each other closely and its structure may likewise be regarded as a defective perovskite structure where half of the octahedrally coordinated atoms (cations) are missing. The IR spectrum of Li{sub 2}PtH{sub 6} reveals the Pt-H T{sub 1u} stretch and bend at 1840 and 889 cm{sup -1}, respectively. - Graphical abstract: Li{sub 2}PtH{sub 6}, the missing start member of the complex metal hydride series A{sub 2}PtH{sub 6} (A=alkali metal) has been prepared by high pressure hydrogenation. In contrast to the heavier homologues, PtH{sub 6}{sup 2-} octahedral units in Li{sub 2}PtH{sub 6} are not well separated and H atoms form a substructure closely corresponding to that of O atoms in cubic perovskite.