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Sample records for alkali halide crystal

  1. Radiation damage in the alkali halide crystals

    International Nuclear Information System (INIS)

    A general review is given of the experimental data on radiation damage in the alkali halide crystals. A report is presented of an experimental investigation of irradiation produced interstitial dislocation loops in NaCl. These loops are found to exhibit the usual growth and coarsening behaviour during thermal annealing which operates by a glide and self-climb mechanism. It is shown that the recombination of defects in these crystals is a two stage process, and that the loss of interstitials stabilized at the loops is caused by extrinsic vacancies. The theoretical techniques used in simulating point defects in ionic crystals are described. Shell model potentials are derived for all the alkali halide crystals by fitting to bulk crystal data. The fitting is supplemented by calculations of the repulsive second neighbour interactions using methods based on the simple electron gas model. The properties of intrinsic and substitutional impurity defects are calculated. The HADES computer program is used in all the defect calculations. Finally the report returns to the problems of irradiation produced interstitial defects. The properties of H centres are discussed; their structure, formation energies, trapping at impurities and dimerization. The structure, formation energies and mobility of the intermediate and final molecular defects are then discussed. The thermodynamics of interstitial loop formation is considered for all the alklai halide crystals. The nucleation of interstitial loops in NaCl and NaBr is discussed, and the recombination of interstitial and vacancy defects. The models are found to account for all the main features of the experimental data. (author)

  2. Dielectric and anharmonic behaviour of alkali halide crystals

    International Nuclear Information System (INIS)

    The dielectric and anharmonic behaviour of alkali halide crystals is studied by determining the volume derivatives of low frequency dielectric constant and polarizability. An interionic force model which takes into account the contributions arising from the short range overlap repulsion and the van der Waals interactions is used in calculations. The implicit and explicit temperature derivatives of low frequency and high frequency dielectric constants are obtained separately for all the alkali halide crystals with NaCl and CsCl structures. The anharmonic contribution to the dielectric constant is calculated using theoretical models due to Szigeti and Havinga. The recent analysis of pressure dependence of effective charge parameter and dielectric constant of ionic crystals performed by Varotsos is shown to be invalid. (author)

  3. Crystal-liquid interface energy and surface stress of alkali halides

    International Nuclear Information System (INIS)

    A model to determine surface stress (f) and crystal-liquid interface energy (?) of (1 0 0) face of NaCl type alkali halides without free parameters is established. While the predicted ? values are thermodynamically reasonable, the model predictions on f are in agreement with other theoretical calculations for (1 0 0) face of NaCl type alkali halides

  4. Anharmonic and photoelastic behaviour of alkali halide crystals

    International Nuclear Information System (INIS)

    An attempt is made to describe the anharmonic and photoelastic behaviour of some alkali halide crystals by means of a well known three-body-force shell model (TSM) after introducing some modifications suggested by Singh and Gupta. The interaction system of this model includes the long-range Coulomb and three-body forces and the short-range overlap repulsion operative between the nearest-neighbour ions only. The effect of anharmonicity has been taken into account by one redundant parameter (C) whose value is determined by deriving a plausible empirical relation between the overlap repulsive parameters of Born-Mayer type. This procedure has made it possible to predict the third order elastic (TOE) constants, the pressure derivatives of the effective SOE constants and the strain derivatives of the electronic dielectric constant and the results are found to agree fairly well with earlier observed data. (K.B.)

  5. Cu halide nanoparticle formation by diffusion of copper in alkali halide crystals

    Scientific Electronic Library Online (English)

    A., Pérez-Rodríguez; M., Flores-Acosta; R., Rodríguez-Mijangos; R., Pérez-Salas.

    2006-04-01

    Full Text Available Atomos de cobre han sido introducidos por difusión en cristales de NaCl, KCl y KBr a 500°C. Los cristales han sido analizados ópticamente con medidas de fotoluminiscencia y por microscopía electrónica de barrido. Los espectros de emisión y excitación, medidos a baja temperatura muestran el efecto de [...] confinamiento de exciton, indicando la formación de nanopartículas de CuX (X=Cl, Br), lo cual ha sido confirmado por imágenes de microscopía electrónica. Este método es propuesto como un método alternativo para obtener nanopartículas de CuX en cristales halogenuros alcalinos. Abstract in english Copper atoms have been introduced by diffusion in NaCl, KCl and KBr crystals at 500°C. The crystals have been optically analyzed with photoluminescence measurements and by scanning electron microscopy. The emission and excitation spectra measured at low temperatures show the exciton confinement effe [...] ct, indicating the formation of CuX (X=Cl, Br) nanoparticles, which has been confirmed by electron microscopy images. This is proposed as an alternative method to obtain CuX nanoparticles in alkali halides crystals.

  6. An optical criterion to obtain miscible mixed crystals in alkali halides

    Directory of Open Access Journals (Sweden)

    R. Rodr\\u00EDguez-Mij\\u00E1ngos

    2008-01-01

    Full Text Available This work gives a novel criterion to predict the formation of alkali halide solid solutions and discusses some results obtained in the development of ternary and quaternary miscible crystalline dielectric mixtures of alkali halides. These mixtures are miscible in any concentration of their components. The miscibility of these mixed crystals is quite related to the F center through the behavior observed in the spectral position of the optical absorption F band as a function of the lattice constant of the alkali halide where the F center was formed. By inspection of an energy graph of the F band energy versus lattice constant (Mollwo-Ivey law, a set of points is observed corresponding to several pure alkali halides (such as KCl, KBr, RbCl, which gives a notion of possible mixed materials that would correspond to adjacent points and a solid solution could be obtained, meaning a single phase crystal, which result in ternary and quaternary mixed crystals. Thus, the optical absorption F band allows have a numerical criterion, based on the percentage respective of the F band energy, in order to predict possible solid solutions. We obtained experimental information using diffractograms of the mixed crystals, from which the lattice constant was obtained and compared with a theoretical calculus using a generalization of Vegard's law, finally it is discussed the case of a crystal growing, starting from five components, picking up five consecutive dots from the graph of Mollwo-Ivey's law.

  7. Anharmonic relaxation times of molecular vibrational modes in alkali halide crystals

    International Nuclear Information System (INIS)

    Low-temperature infrared-saturation and hole-burning measurements have been performed on an internal vibrational mode of a spherical-top molecule embedded in a variety of alkali halide crystals. The vibrational relaxation times T1 and T2 satisfy the relation T2approx. =2T1 but T1 (< or =38 nsec) is orders of magnitude smaller than expected for multiphonon decay. A study of the alkali halide dependence of these relaxation times suggests that a specific combination of internal, local, and band modes is involved in the decay process

  8. Thermoluminescence response of a mixed ternary alkali halide crystals exposed to gamma rays

    International Nuclear Information System (INIS)

    Ionic crystals, mainly alkali halide crystals have been the subject of intense research for a better understanding of the luminescence properties of defects induced by ionizing radiation. The defects in crystals can be produced in appreciable concentration due to elastic stresses, radiation, and addition of impurities. These defects exhibit remarkable thermoluminescence properties. This work is concerned with the Tl properties of a ternary alkali halide crystal after being irradiated with gamma and beta rays. It has been found that the Tl glow peak of the crystal follows a rule of average associated to the Tl Temperatures of the components of the mixture, similarly to the response of europium doped binary mixed crystals KClxKBr1-x and KBrxRbBr1-x. (Author)

  9. Thermoluminescence response of a mixed ternary alkali halide crystals exposed to gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez M, R.; Perez S, R. [Universidad de Sonora, Departamento de Investigacion en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico); Vazquez P, G.; Riveros, H. [UNAM, Instituto de Fisica, Apdo. Postal 20-364, 01000 Mexico D. F. (Mexico); Gonzalez M, P., E-mail: mijangos@cifus.uson.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-08-15

    Ionic crystals, mainly alkali halide crystals have been the subject of intense research for a better understanding of the luminescence properties of defects induced by ionizing radiation. The defects in crystals can be produced in appreciable concentration due to elastic stresses, radiation, and addition of impurities. These defects exhibit remarkable thermoluminescence properties. This work is concerned with the Tl properties of a ternary alkali halide crystal after being irradiated with gamma and beta rays. It has been found that the Tl glow peak of the crystal follows a rule of average associated to the Tl Temperatures of the components of the mixture, similarly to the response of europium doped binary mixed crystals KCl{sub x}KBr{sub 1-x} and KBr{sub x}RbBr{sub 1-x}. (Author)

  10. Electrical conduction of alkali-halide crystals after ion-heat modification

    International Nuclear Information System (INIS)

    The influence of ion-heat modification modes on the change of electrical conduction ? of alkali-halide crystals is explored. The most essential changes of ? are result in ionic intermixing and subsequent heat treatment at 550-750 K. The conduction elevation is stipulated by defect formation accompanying radiolysis product appearance on the surface and forming the metal formation in modified layer and on the surface. Evaporation of crystals and change of their morphology and annealing of defects at temperature above optimum (individual for each compounds) lead to decrease of electrical conduction also

  11. Transmission electron microscopy of extended defects in alkali halide crystals

    International Nuclear Information System (INIS)

    The subject is covered in sections entitled: introduction (general description of the scope of the review); principles of electron microscopy; thin foil preparation; electron-specimen interaction (charge aquisition, electron irradiation damage, electron beam heating); electron microscopy of point defect aggregates (interstitial dislocation loops, alkali metal colloids, halogen bubbles); electron microscopy of deformation defects (intrinsic deformation behaviour, irradiation and deformation). (U.K.)

  12. Optical Constants and Excitons of Alkali Cuprous Halide Crystals

    Science.gov (United States)

    Edamatsu, Keiichi; Nanba, Takao; Ikezawa, Mikihiko

    1989-01-01

    The anisotropic reflection spectra of K2AgI3, Rb2AgI3 and Rb2AgBr3 have been measured in the range from 4 to 26 eV using synchrotron radiation. The optical constants have been obtained through the Kramers-Kronig analysis. The characters of the band edge excitons of K2AgI3 and Rb2AgI3 are very similar to those of the alkali iodides. However, the perturbation calculation has indicated that the spin-orbit interaction scarcely affect the outline of the valence band structure of Rb2AgI3 and that no spin-orbit doublet appears in the absorption spectra. The anisotropic absorption due to the core excitons of K+ or Rb+ have been found around 20 or 17 eV, respectively. The prominent structures due to plasmons of valence electrons have been found at 10-12 eV in the energy loss spectra.

  13. Accidental birefringence and annealing effects in alkali halide single crystals

    International Nuclear Information System (INIS)

    Photoelasticity is used to explain the accidental birefringence patterns induced by thermal stresses in KCl and KBr-KCl crystals. It is shown that the residual stress and plastic deformations are essentially due to the variable temperature gradients. An optimal thermal treatment in order to eliminate the residual stresses is presented. (author)

  14. An optical criterion to obtain miscible mixed crystals in alkali halides

    Scientific Electronic Library Online (English)

    R, Rodríguez-Mijángos; G, Vázquez-Polo; J.J., Palafox; R, Pérez-Salas.

    2008-11-01

    Full Text Available Este trabajo ofrece un nuevo criterio para predecir la formación de soluciones sólidas en halogenuros alcalinos cristalinos y discute algunos resultados obtenidos en el desarrollo de mezclas dieléctricas cristalinas miscibles de halogenuros alcalinos ternarias y cuaternarias. Estas mezclas son misci [...] bles en cualquier concentración de sus componentes. Tener el resultado de estas mezclas cristalinas está relacionado al centro F a través del comportamiento observado en la banda F de absorción en función de la constante de red de los halogenuros alcalinos donde el defecto fue formado (centro F). Dando un vistazo a la gráfica de Energía de banda F versus constante de red (ley de Mollwo-Ivey), se observa un conjunto de puntos, que dan la pauta (tal como KCl, KBr, RbCl), de posibles mezclas de materiales correspondientes a puntos adyacentes y una solución sólida podría formarse, significando un cristal de una sola fase, que dan por resultado cristales ternarios y cuaternarios. Así, la banda F de absorción nos permite tener un criterio numérico, basado en el porcentaje de cambio de la energía de la banda F que permite obtener soluciones sólidas. Encontramos información experimental, usando difractogramas de las mezclas cristalinas, se obtienen las constantes de red y se comparan con la obtenida teóricamente a través de la generalización de la Regla de Vegard, finalmente se discute la posibilidad de crecer cristales partiendo de cinco componentes, tomando cinco puntos consecutivos en la grafica de la Ley de Mollwo-Ivey. Abstract in english This work gives a novel criterion to predict the formation of alkali halide solid solutions and discusses some results obtained in the development of ternary and quaternary miscible crystalline dielectric mixtures of alkali halides. These mixtures are miscible in any concentration of their component [...] s. The miscibility of these mixed crystals is quite related to the F center through the behavior observed in the spectral position of the optical absorption F band as a function of the lattice constant of the alkali halide where the F center was formed. By inspection of an energy graph of the F band energy versus lattice constant (Mollwo-Ivey law), a set of points is observed corresponding to several pure alkali halides (such as KCl, KBr, RbCl), which gives a notion of possible mixed materials that would correspond to adjacent points and a solid solution could be obtained, meaning a single phase crystal, which result in ternary and quaternary mixed crystals. Thus, the optical absorption F band allows have a numerical criterion, based on the percentage respective of the F band energy, in order to predict possible solid solutions. We obtained experimental information using diffractograms of the mixed crystals, from which the lattice constant was obtained and compared with a theoretical calculus using a generalization of Vegard's law, finally it is discussed the case of a crystal growing, starting from five components, picking up five consecutive dots from the graph of Mollwo-Ivey's law.

  15. A mass-spectrometric determination of the work function of alkali metal halide crystals

    Science.gov (United States)

    Kudin, L. S.; Dunaev, A. M.; Butman, M. F.; Kryuchkov, A. S.

    2011-02-01

    Thermochemical cycles including experimentally measured enthalpies of sublimation of alkali metal halides in the form of M2X+ and MX{2/?} ionic clusters and MX molecules were used to calculate work functions for NaCl, NaBr, NaI, KCl, KBr, KI, RbCl, and RbI.

  16. Luminescent unit computerization to research spectral characteristics of fine film alkali halide crystal

    International Nuclear Information System (INIS)

    The fundamental optical absorption of ion crystals characterizes the creation of different free low energetic electronic excitation (the excitons and electron-hole pairs), but their straight registration is not possible because of incommensurable big absorption factor of alkali halide monocrystals. So to registration the spectrums of alkali halide monocrystal very fine layers are necessary. We have received fine films of Nal and KCl in system of KCl-Nal-KCl, KCl-KI-KCl on the base of universal vacuum post VUP-4, VUP-5 by thermal evaporation. A unique spectral unit has been created For this on the basic the SDL-2 complex. Complex consists of radiator, systems of condensers, monochromators MDR-12 and MDR-23, receivers of radiation, controller by unit. Connect and control of monochromators by means of IBM-compatible computer has been created. Kinematics schemes of monochromators provide consequent removing on output slot of monochromatic radiation in operating range of each diffraction lattice and indication its wavelength. The tumbling diffraction lattices is done the crossbar engines SHDR-711. For this special plate of control and block of reinforcement for crossbar engines in monochromators MDR-12 and MDR-23 are designed and constructed. Created controller of monochromators consists of double cascade preamplifier on transistors n-p-n type (815G) and logical scheme, constructed on summers and K555 series triggers. The preamplifier is used for reinforcement of signal toier is used for reinforcement of signal to available amplifier on transistors KT837D. The logical scheme reduces the number of used categories of bidirectional port and enables unhooking the feeding to the windings of crossbar engine at conservation of previous combination of signals. The connection controller of monochromators is done through controller of port of computer with use the parallel interface. For installing computerized system of collection and data processing is provided marketed by means of modern object-oriented programming languages (Visual C++ 6.0, Visual Basic 6.0). As the result of the experiments it has been noted that the burning effect of own luminescence is in its maximum in the iodides of alkaline metals, for instance, in KI, NaI, RbI, and CsI crystals. From the point of the experimental equipment in order to registration the fundamental optical absorption of these crystals there is no necessity in such rare vacuum monochromators

  17. The experimental estimation of screen barrier of self trapped excitons' relaxation in alkali halide crystals

    International Nuclear Information System (INIS)

    Full text: Earlier the effect of intrinsic luminescence ignition of alkali halide crystals (AHC) at lattice symmetry lowering was found. This is probably connected with the efficiency decrease of nonradiative channel of exciton decay into initial radiation defects. It is well known that at self trapped exciton (STE) luminescence quenching the radiation defects creation efficiency increases. Experimental method for the estimation of nonradiative STE transfer activation energy in AHC at low temperature uniaxial stress is proposed. On the basis of values of STE luminescence quenching activation energy for the range of AHC obtained by temperature dependence of X-ray luminescence for both in absentia and at low temperature uniaxial stress, we can mark out the main rule: the activation energy increase at elastic uniaxial stress is observed in the range KBr?NaCl ?KI?Rbl?CsBr and explained by the increase of potential barrier of STE nonradiative decay into radiation defects. It is represented the values of STE luminescence quenching activation energy for the range of AHC for both in absentia and at low temperature uniaxial stress. Thus, it becomes obvious that radiation defects' creation decrease in KI and Rbl crystals depends on elastic stress degree because of the increase of potential barrier sharing radiative and nonradiative STE decay channels

  18. Ab Initio Calculation of the Lattice Distortions induced by Substitutional $Ag$- and $Cu$-Impurities in Alkali Halide Crystals

    CERN Document Server

    Aguado, A; Alonso, J A; Aguado, Andres; Lopez, Jose M.; Alonso, Julio A.

    2000-01-01

    An ab initio study of the doping of alkali halide crystals (AX: A=Li, Na, K,Rb; X=F, Cl, Br, I) by ns2 anions (Ag- and Cu-) is presented. Large activeclusters with 179 ions embedded in the surrounding crystalline lattice areconsidered in order to describe properly the lattice relaxation induced by theintroduction of substitutional impurities. In all the cases considered, thelattice distortions imply the concerted movement of several shells ofneighbors. The shell displacements are smaller for the smaller anion Cu-, asexpected. The study of the family of rock-salt alkali halides (excepting CsF)allows us to extract trends that might be useful at a predictive level in thestudy of other impurity systems. Those trends are presented and discussed interms of simple geometric arguments.

  19. Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations

    Science.gov (United States)

    Webster, R.; Bernasconi, L.; Harrison, N. M.

    2015-06-01

    We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green's function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional cHF and show that there exists one value of cHF (˜0.32) that reproduces at least semi-quantitatively the optical gap of this material.

  20. Muon radiolysis in alkali halides

    International Nuclear Information System (INIS)

    In order to shed new light on the initial loss of muon spin polarization, or so-called ''missing fraction'', which is commonly observed in non-metallic solids, we have studied muon-induced excitation in various alkali halides by measuring the luminescences associated with the radiative decay of the self-trapped excitons (STE). The result strongly suggests that the spin-exchange interaction between muonium and muon radiolysis products including STE's causes fast muon depolarization in those materials. (orig.)

  1. Measurements of spin-lattice relaxation time in mixed alkali halide crystals

    International Nuclear Information System (INIS)

    Using magneto-optic techniques the ground state spin-lattice relaxation times (T1) of 'F' centers in mixed Alkali Halide cristals (KCl-KBr), was studied. A computer assisted system to optically measure short relaxation times (approx. = 1mS), was described. The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. The T1 magnetic field dependency at 2 K (up to 65 KGauss), was obtained as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behaviour of T1 in mixed cristals. The Direct Process results (T approx. = 2.0 K) compared against that theory shows that the main relaxation mecanism, up to 25 KGauss, continues to be phonon modulation of the hiperfine iteraction between F electrons and surrounding nuclei. (Author)

  2. Optical surface breakdown of alkali halide crystals by microsecond pulses from a wide-aperture CO2 laser

    International Nuclear Information System (INIS)

    A study was made of the dynamics of temporal and spatial changes in the spectral characteristics of plasmas. A three-stage mechanism of the damage to surfaces of alkali halide crystals by microsecond pulses from a TEA CO2 laser was proposed: breakdown initiation (at a distance of 3-5 mm from the surface with a time delay up to 1 ?s relative to the leading edge of a laser pulse), evaporation (after a further delay of 3-5 ?s), and interaction of the adsorbates with a plasma jet and with the laser radiation, as well as heating and cracking of a crystal by the UV plasma radiation. (interaction of laser radiation with matter. laser plasma)

  3. Effect of strong electric fields on the damage and coagulation radiation processes of electron cemters in whisker alkali-halide crystals

    International Nuclear Information System (INIS)

    Effect of electric field on electric processes in whisker alkali-halide crystals is shown to boil down to spatial division of charged particles, that is, to reduction of probability of their recombination. Growth of the rate of radiation destruction of F2-centers and reduction of the efficiency of their coagulation with increase of constant electric field stress are determined experimentally

  4. Formation of radiation-induced defects in alkali halide crystals along tracks of heavy charged particles

    International Nuclear Information System (INIS)

    Comparative analysis of regularities of stable hole defects formation in KBr crystals under high-energy proton irradiation as compared with effects attained at low-intensive X-ray and strong pulsed electron excitation is presented. Proton energy is equal to E=5.5 MeV. Beam intensity varied in the 3.5x109-1.75x1011 cm-2 s-1 range. Absorbed dose rate at ?=1.75x1010 cm-2 s-1 makes up 2.15x104 rad/s. Electron energy equals E=200 keV. Under single-pulsed electron radiation the absorbed dose in crystals constituted 1.1x1020 eV/cm3. The absorbed dose rate in this case approached 1014 rad/s. Formation of hole colore centers was studied by measuring optical absorption spectra and thermostimulated luminescence. The processes of hole defect formation are shown to comply with the same regularities under proton and intense pulsed electron radiations. But in the proton track larger halide sets than at single-pulse electron excitation of crystals are formed

  5. Shallow electron traps in alkali halide crystals: Mollwo-Ivey relations of the optical absorption bands

    Science.gov (United States)

    Ziraps, Valters

    2001-03-01

    Evidences are given that two classes of the transient IR- absorption bands: (a) with max. at 0.27-0.36 eV in NaCl, KCl, KBr, KI and RbCl (due to shallow electron traps according G. Jacobs or due to bound polarons according E.V. Korovkin and T.A. Lebedkina) and (b) with max. at 0.15-0.36 eV in NaI, NaBr, NaCl:I, KCl:I, RbCl:I and RbBr:I (due to on-center STE localized at iodine dimer according M. Hirai and collaborators) are caused by the same defect- atomic alkali impurity center [M+]c0e- (electron e- trapped by a substitutional smaller size alkali cation impurity [M+]c0). The Mollwo-Ivey plots (for the transient IR-absorption bands) of the zero-phonon line energy E0 (for NaCl, KCl, KBr, RbCl and NaBr, KCl:I) and/or the low-energy edge valued E0 (for NaI, RbCl:I, RbBr:I) versus anion-cation distance (d) evidence that two types of the [M+]c0e- centers are predominant: (a) [Na+]c0e- in the KX and RbX host crystals with the relation E0approximately equals 6.15/d2.74, (b) [Li+]c03- in the NaX host crystals - E0approximately equals 29.4/d4.72. The Mollwo-Ivey relation E0approximately equals 18.36/d(superscript 2.70 is fulfilled as well for the F' band in NaCl, KCl, KBr, KI, RbCl, RbI if we use the F' center optical binding energy values E0.

  6. Recombination of radiation defects in alkali halide crystals at low temperature

    International Nuclear Information System (INIS)

    The complex investigation of the ionic-electronic processes of the charge transport and thermally stimulated luminescence of colour centres (I, ?, F, F', Vsub(K) and H) in X-irradiated KBr, NaCl, NaI and KCl crystals at 4.2 K has been carried out. The experiment has been performed on X-irradiated KBr at 4.2 K by a complex of thermally stimulated methods. A number of substages of temperature annealing of different defects was studied. The effect of electron tunneling ''recharge'' in the excited defect pair (F-H) during photostimulation in the F-band of KBr is observed which results in the charged Frenkel defect pair formation (?-I). The conclusion is drawn that the tunneling ''recharge'' of the non-excited F-H pair is unlikely. It was observed that the Frenkel defect (I, ?, ''H-Vsub(K)'', F, H') accumulation efficiencies increases by 10% or more if the X-irradiation at 4.6 K is carried out under an applied DC field of 3 kV/cm. Two competitive mechanism of the primary generation of the anion Frenkel defects are discussed. The formation of the self-trapped excitons and their luminescence as a result of the H and F centers direct recombination could be noneffective. It is found that anion exciton dissociation into the electron- hole pair is a process competitive to the exciton decay into the Frenkel defect pair

  7. A simple formula for the fundamental optical absorption of alkali halide melts

    International Nuclear Information System (INIS)

    Significant similarities - with respect to absorption of ultraviolet - between the crystalline and liquid phases of the alkali halides are considered. It is shown that a simple formula which emerged from an earlier application of local electron transfer concepts to the fundamental absorption of the alkali halide crystals appears to apply equally well (i.e., within experimental error) to their melts. This formula fits the observations relating to the fundamental absorption of five molten alkali halides and yields predictions for all the others - which will, it is hoped, stimulate experimental activity. (author)

  8. Optical radiation from electron sputtering of alkali halides

    International Nuclear Information System (INIS)

    Electron-surface collisions have been observed to result in the emission of optical radiation from excited atoms and molecules desorbed from alkali halide single crystal surfaces. The detected radiation included Na and Li resonance lines, hydrogen Balmer emission, and OH molecular radiation. Much previous experimental and theoretical effort has been devoted to electron stimulated desorption (ESD) of ground state neutrals and ions, and in particular from alkali halides. The few studies concerned with excited particles have dealt primarily with ejected metastable neutrals. In one case involving electron bombardment fluorescence of ice, a tentative identification has been made of OH molecular radiation. The results reported here include a) the first definitive work on optical radiation from electron bombardment induced emission of excited free substrate particles, and b) the first observations of characteristic radiation from previously adsorbed free atoms and molecules. (orig.)

  9. Angle-resolved kinetic energy distributions of atoms sputtered by electron bombardment of single crystal alkali halides

    International Nuclear Information System (INIS)

    Angle-resolved kinetic energy distributions have been measured for atoms desorbed from (100) and (110) surfaces of KBr and the (100) surface of KCl due to electron bombardment. We found strong directional emission of nonthermal halogen atoms along the axis of the investigated crystals rather than along the axis as expected. Angular distributions of both halogen and alkali atoms emitted with thermal energies were found to be uniformly cosine with respect to the surface normal for all crystal faces. Fast hole diffusion to the bombarded surface and nonradiative decay of selftrapped surface excitons are proposed as essential elements in the explanation of these results. (orig.)

  10. Study on influence of growth conditions on position and shape of crystal/melt interface of alkali lead halide crystals at Bridgman growth.

    Czech Academy of Sciences Publication Activity Database

    Král, Robert

    2012-01-01

    Ro?. 360, S1 (2012), s. 162-166. ISSN 0022-0248. [5th International Workshop on Crystal Growth Technology (IWCGT). Berlin, 26.06.2011-30.06.2011] R&D Projects: GA AV ?R KJB200100901 Institutional research plan: CEZ:AV0Z10100521 Keywords : Interfaces * morphological stability * segregation * Bridgman technique * halides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.552, year: 2012

  11. A new polarizable force field for alkali and halide ions

    International Nuclear Information System (INIS)

    We developed transferable potentials for alkali and halide ions which are consistent with our recent model of water [P. T. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)]. Following the approach used for the water potential, we applied Gaussian charge distributions, exponential repulsion, and r?6 attraction. One of the two charges of the ions is fixed to the center of the particle, while the other is connected to this charge by a harmonic spring to express polarization. Polarizability is taken from quantum chemical calculations. The repulsion between different species is expressed by the combining rule of Kong [J. Chem. Phys. 59, 2464 (1972)]. Our primary target was the hydration free energy of ions which is correct within the error of calculations. We calculated water-ion clusters up to 6 water molecules, and, as a crosscheck, we determined the density and internal energy of alkali-halide crystals at ambient conditions with acceptable accuracy. The structure of hydrated ions was also discussed

  12. A new polarizable force field for alkali and halide ions

    Science.gov (United States)

    Kiss, Péter T.; Baranyai, András

    2014-09-01

    We developed transferable potentials for alkali and halide ions which are consistent with our recent model of water [P. T. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)]. Following the approach used for the water potential, we applied Gaussian charge distributions, exponential repulsion, and r-6 attraction. One of the two charges of the ions is fixed to the center of the particle, while the other is connected to this charge by a harmonic spring to express polarization. Polarizability is taken from quantum chemical calculations. The repulsion between different species is expressed by the combining rule of Kong [J. Chem. Phys. 59, 2464 (1972)]. Our primary target was the hydration free energy of ions which is correct within the error of calculations. We calculated water-ion clusters up to 6 water molecules, and, as a crosscheck, we determined the density and internal energy of alkali-halide crystals at ambient conditions with acceptable accuracy. The structure of hydrated ions was also discussed.

  13. A new polarizable force field for alkali and halide ions

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, Péter T.; Baranyai, András [Institute of Chemistry, Eötvös University, 1518 Budapest 112, PO BOX 32 (Hungary)

    2014-09-21

    We developed transferable potentials for alkali and halide ions which are consistent with our recent model of water [P. T. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)]. Following the approach used for the water potential, we applied Gaussian charge distributions, exponential repulsion, and r{sup ?6} attraction. One of the two charges of the ions is fixed to the center of the particle, while the other is connected to this charge by a harmonic spring to express polarization. Polarizability is taken from quantum chemical calculations. The repulsion between different species is expressed by the combining rule of Kong [J. Chem. Phys. 59, 2464 (1972)]. Our primary target was the hydration free energy of ions which is correct within the error of calculations. We calculated water-ion clusters up to 6 water molecules, and, as a crosscheck, we determined the density and internal energy of alkali-halide crystals at ambient conditions with acceptable accuracy. The structure of hydrated ions was also discussed.

  14. Additional evidence for the interconnection of the conductivity activation energy with bulk properties in multiphased alkali halide mixed crystals

    International Nuclear Information System (INIS)

    The preparation of mixed crystals of NaBr and KBr from melt as well as their physical characterization have recently been reported. Electrical measurements were carried out at various temperatures, which showed that their conductivity increases with the increase in temperature and varies nonlinearly with bulk composition. We find that for most of the compositions studied, the activation energy deduced from the temperature variation of their conductivity obeys a thermodynamical model that interrelates the defect Gibbs energy with the bulk elastic and expansivity data. The present finding is similar to the one recently obtained in the mixed crystals of NaBr and KCl (V. Katsika-Tsigourakou, A. Vassilikou-Dova, Physica B, 403 (2008) 3809).

  15. Development of alkali halide-optics for high power-IR laser

    International Nuclear Information System (INIS)

    In this work 'Development of Alkali Halide-Optics for High Power-IR Laser' we investigated the purification of sodiumchloride-, potassiumchloride- and potassiumbromide-raw materials. We succeeded to reduce the content of impurities like Cu, Pb, V, Cr, Mn, Fe, Co and Ni in these raw materials to the lower of ppb's by a Complex-Adsorption-Method (CAM). Crystals were grown from purified substances by 'Kyropoulos' method'. Windows were cur thereof, polished and measured by FTIR-spectroscopy. Analytical data showed, that the resulting crystals were of lower quality than the raw materials. Because of this fact crystal-growing-conditions have to undergo a special improvement. Alkali halide windows from other sources on the market had been tested. (orig.)

  16. A new fundamental hydrogen defect in alkali halides

    International Nuclear Information System (INIS)

    Atom hydrogen in neutral (H0) and negative (H-) form on substitutional and interstitial lattice sites gives rise to well characterized model defects in alkali-halides (U,U1,U2,U3 centers), which have been extensively investigated in the past. When studying the photo-decomposition of OH- defects, a new configuration of atomic charged hidrogen was discovered, which can be produced in large quantities in the crystal and is apparently not connected to any other impurity. This new hidrogen defect does not show any pronounced electronic absorption, but displays a single sharp local mode band (at 1114cm-1 in KCl) with a perfect isotope shift. The defect can be produced by various UV or X-ray techniques in crystais doped with OH-, Sh- or H- defects. A detailed study of its formation kinetics at low temperature shows that it is primarily formed by the reaction of a mobile CI2- crowdion (H-center) with hidrogen defects

  17. Investigating Metallization in Shock-Compressed Alkali Halides

    Science.gov (United States)

    Diamond, M. R.; Ali, S. J.; Eggert, J.; Jeanloz, R.; Collins, G. W.; McWilliams, R. S.

    2014-12-01

    Laser-shock compression on four alkali halides has been used to probe the transition from insulating to metallic states, a high-pressure transition in chemical bonding that has fundamental implications for planetary formation and structure. Collectively, pressures up to 450 GPa were explored across a total of fourteen single-crystal samples of CsI, CsBr, KBr and NaCl. Velocity interferometry (VISAR) was used to record shock velocities and reflectivities at 532 nm during decaying shock compression. The data show up to three-fold increases in density as well as significant increases in optical reflectivity in response to high pressures and temperatures. Using a Drude model to estimate conductivities from the measured reflectivities, we investigate the onset of metallic conductivities for each compound. Ionic salts are simple model systems amenable to first-principles theory and serve as analog materials for predicting whether specific chemical constituents can reside in the rocky mantles or metallic cores of planets. A key objective is to disentangle the complementary roles of temperature and compression in transforming ionic into metallic bonding. Furthermore, at high pressures CsI becomes analogous to Xe: they are isoelectronic and follow matching equations of state. Therefore, studies on CsI can inform understanding of noble-gas geochemistry at conditions deep inside planets (e.g., the likelihood of Xe solubility in planetary mantles or cores). Our experiments were conducted using the Janus laser of the Jupiter Laser Facility at Lawrence Livermore National Laboratory.

  18. Electroreduction of praseodymium in solutions of alkali metal halides

    International Nuclear Information System (INIS)

    The process of praseodymium complexes electric reduction in solutions of alkali metal halides was studied by voltammetric and polarographic methods. The mechanism of praseodymium reduction is suggested. 3.0-3.2 M KCl solutions with pH 1.9-2.0 were chosen as optimal background electrolytes for praseodymium determination by voltammetric method. Praseodymium detection limit using the method mentioned equals 5x10-5 mol/l. Neodymium, terbium, gadolinium ions interfere in praseodymium determination

  19. Analysis of the Interrelationship Between Melting and Fracturing of Alkali Halides

    Science.gov (United States)

    Zou, Yong; Huang, Hulin; Cui, Guang Lei

    2015-05-01

    On the basis of the lattice potential energy with two forms proposed by Born-Mie and Born-Mayer, respectively, the critical interionic separations {{ r}}i where the lattice is fractured due to tensile force have been evaluated for alkali metal halides. The theoretical results are analyzed together with the interionic separations {{ r}}m determined by the melting temperature and the help of the isobaric equation of state. A new and simple interrelationship between {{ r}}m and {{ r}}i is obtained, and the crystal melting behavior can be accordingly predicted for NaCl-structure ionic crystals.

  20. Epitaxial growth of alkali halides on stepped metal surfaces

    International Nuclear Information System (INIS)

    We present a growth study of the alkali halides NaCl and KCl on the stepped metal surfaces Cu(311) and Cu(221) using high resolution low energy electron diffraction. For all systems studied it was found that the alkali halide deposit forms (100)-terminated epitaxial layers which have essential structural features in common: The interfacial arrangement between the ionic adlayer and the stepped metal substrate is characterized by an alignment of the polar in-plane Cl ion rows parallel and perpendicular to the intrinsic Cu steps. For low coverages (?1 ML) the Cl ions are in registry with the intrinsic substrate steps causing uniaxial strain in the direction perpendicular to the steps. In contrast, parallel to the steps the Cl ions are free to adjust their optimum Cl-Cl spacing. For coverages >3 ML, the strain perpendicular to the intrinsic Cu steps is accommodated which suggests the incorporation of monoatomic Cu defect steps at the interface in this regime of higher coverage

  1. Theory of freezing of alkali halides and binary alloys

    International Nuclear Information System (INIS)

    Using the basic equations of classical statistical mechanics relating the singlet densities rho1 and rho2 of a binary system to the three partial direct correlation functions csub(ij), a theory of freezing is developed. Though the theory is set up for arbitrary concentration, we focus on the freezing of the alkali halides. In particular, we show that periodic solutions of the equations for rho1 and rho2 can coexist with homogeneous solutions. The difference in free energy between periodic and homogeneous phases is built up in terms of (i) the volume difference and (ii) the Fourier components of rho1, rho2 and csub(ij). To lowest order, it is stressed that the freezing transition is determined by the charge-charge structure factor at the principal peak and by the compressibility. (author)

  2. Dynamical structure of water in alkali halide aqueous solutions

    Science.gov (United States)

    Ujike, Tomoko; Tominaga, Yasunori; Mizoguchi, Kohji

    1999-01-01

    The low-frequency Raman spectra of alkali halide AX (A=Na, K, Rb; X=Cl, Br) aqueous solutions with various temperatures and concentrations are investigated. We have found that at the supercooled temperature region the relaxation time of the KX and RbX aqueous solutions becomes shorter than that of pure water. Since in these solutions the viscosity decreases with increasing concentration, this result suggests that the relaxation time of the electrolytic solutions in the Raman region is strongly correlated with the viscosity. Moreover, through comparing the spectral profiles of the relaxation mode among AX aqueous solutions we demonstrate that the pattern of the concentration dependence of the relaxation mode parameters such as the activation energy changes between NaX and (KX, RbX) aqueous solutions.

  3. Alkali halide clusters produced by fast ion impact

    International Nuclear Information System (INIS)

    The most abundant geometries and relative stabilities of alkali halide clusters with a (XY)n0 configuration (e.g., LiF, NaCl, KBr) are described. Five main series were obtained: linear, cyclic, cubic, arc strips and nanotubes. The stability analysis shows that higher members are likely to be formed from the lower member of the same series and/or from two building blocks (n = 1, 2). The energy analysis (D-plot) indicates that the most compact ones (e.g., cubic and nanotubes) present higher stability when compared to the linear, cyclic and arc strip structures; moreover, relative stability between the cubic and nanotube series varies with the cluster size.

  4. Absorption lineshape of FA centers in alkali halides

    International Nuclear Information System (INIS)

    The line shape of the absorption bands of FA centers in alkali halides have been studied for the first time. The new method used for this investigation is based on the determination of the overlap between the FA1 and FA2 bands from luminescence measurements. The experimental results have been compared with calculated values deduced from the theoretical FA bands of different shapes. For both FA(I) centers in KCl:Na+ and FA(II) centers in KCl:Li+ and RbCl:Li+ the absorption lineshape at low temperature is much closer to a sum of two Lorentzian curves than that of two Gaussian or Poissonian bands. This results shows an unexpected difference with the F centers, whose absorption lineshape is known to be Poissonian at the same temperatures

  5. Desorption and surface topography changes induced by He+ ion bombardment of alkali halides

    International Nuclear Information System (INIS)

    Desorption fluxes from alkali halide (RbI, KBr) crystals under 5 keV He+ bombardment and the corresponding surface topography evolution were investigated by means of quadruple mass spectroscopy (QMS) and dynamic force microscopy (DFM) in UHV. Although, for the energy range of He+ ions used, desorption of alkali halides occurs predominantly via electronic processes, there are significant differences between the ion-stimulated desorption (ISD) and the electron-stimulated desorption (ESD). The latter proceeds in a layer-by-layer mode and, as a result, oscillating desorption fluxes are observed. For ISD the DFM images show that the surface erosion does not follow the layer-by-layer scheme and no oscillation in desorption fluxes are found but they exhibit monotonic decrease to some saturation level. We suggest that these differences between electron- and ion-stimulated desorption are caused by ballistic processes disturbing the perfect lattice and introducing defects in the bulk and at the surface. Such lattice defects can act as recombination centres for diffusing Frenkel defects and inhibit the desorption process. Additionally, projectiles colliding violently with top-layer ions introduce additional nucleation centres for vacancies on the surface which lead to the surface erosion in the multi-layer mode

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

    Science.gov (United States)

    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

  7. Charge-charge liquid structure factor and the freezing of alkali halides

    International Nuclear Information System (INIS)

    The peak height of the charge-charge liquid structure factor Ssub(QQ) in molten alkali halides is proposed as a criterion for freezing. Available data on molten alkali chlorides, when extrapolated to the freezing point suggests Ssub(QQ)sup(max) approximately 5. (author)

  8. Determination of oxygen in molten alkali halide salts by proton activation analysis

    International Nuclear Information System (INIS)

    The authors have recently used a lanthanum fluoride precipitation method to separate 18F produced from proton activation of 18O in alkali chloride and fluoride salts. The procedure was developed for studying dissolved oxide species in alkali halide melts. Determination of oxygen in these systems is important for research in batteries and in extractive metallurgy utilizing molten salts as solvents. The details are given oxygen determination in alkali chloride and fluoride systems

  9. Physics and Nanofriction of Alkali Halide Solid Surfaces at the Melting Point

    CERN Document Server

    Zykova-Timan, T; Tartaglino, U; Tosatti, E

    2006-01-01

    Alkali halide (100) surfaces are anomalously poorly wetted by their own melt at the triple point. We carried out simulations for NaCl(100) within a simple (BMHFT) model potential. Calculations of the solid-vapor, solid-liquid and liquid-vapor free energies showed that solid NaCl(100) is a nonmelting surface, and that the incomplete wetting can be traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface, reducing in particular its entropy much below that of solid NaCl(100). Presently, we are making use of the nonmelting properties of this surface to conduct case study simulations of hard tips sliding on a hot stable crystal surface. Preliminary results reveal novel phenomena whose applicability is likely of greater generality.

  10. Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

    CERN Document Server

    Zykova-Timan, T; Tartaglino, U; Tosatti, E

    2005-01-01

    Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface. The latter is pursued in detail, and it is shown that surface short-range charge order acts to raise the surface tension because incipient NaCl molecular formation anomalously reduces the surface entropy of liquid NaCl much below that of solid NaCl(100).

  11. Deformation-induced phonon scattering by debris defects in alkali halides

    International Nuclear Information System (INIS)

    A number of investigations have shown that the thermal conductivity of alkali halide crystals is markedly affected by crystalline defects, chiefly in the low temperature region, say below around 10 K. The effects are very prominent after plastic deformation, where the conductivity is reduced by more than a factor of 10 after deformation by several percent already. Albeit a considerable amount of data and respective models have been elaborated, the correspondence between models and the body of experimental results still needs improvement, especially in the temperature range between around 1 and 5 K. As will be shown for the case of NaCl, where most of the experimental results exist, a satisfactory description of the thermal conductivity properties can be obtained when relying on, instead of dislocations and/or vacancy defects, a debris defect as suggested by transmission electron microscopy.

  12. Ion Segregation and Deliquescence of Alkali Halide Nanocrystals on SiO2

    Energy Technology Data Exchange (ETDEWEB)

    Arima, Kenta; Jiang, Peng; Lin, Deng-Sung; Verdaguer, Albert; Salmeron, Miquel

    2009-08-11

    The adsorption of water on alkali halide (KBr, KCl, KF, NaCl) nanocrystals on SiO{sub 2} and their deliquescence was investigated as a function of relative humidity (RH) from 8% to near saturation by scanning polarization force microscopy. At low humidity, water adsorption solvates ions at the surface of the crystals and increases their mobility. This results in a large increase in the dielectric constant, which is manifested in an increase in the electrostatic force and in an increase in the apparent height of the nanocrystals. Above 58% RH, the diffusion of ions leads to Ostwald ripening, where larger nanocrystals grow at the expense of the smaller ones. At the deliquescence point, droplets were formed. For KBr, KCl, and NaCl, the droplets exhibit a negative surface potential relative to the surrounding region, which is indicative of the preferential segregation of anions to the air/solution interface.

  13. A study on the electrochemical behaviour of polypyrrole films in concentrated aqueous alkali halide electrolytes

    DEFF Research Database (Denmark)

    Jafeen, M. J. M.; Careem, M.A.

    2014-01-01

    The electrochemical behaviour of polypyrrole films doped with dodecyl benzene sulfonate (PPy/DBS) in LiCl aqueous electrolytes has been investigated in order to find the electrolyte concentration suitable for the operation of PPy/DBS-based soft actuators. For this investigation, PPy/DBS films deposited on gold-coated quartz crystals by electropolymerization and simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance techniques were used. During the first redox cycle, while large water movement is observed along with the counter ions in dilute electrolytes, such water transport in concentrated electrolytes is found to be very low. In dilute electrolytes, water molecules accompany counter ions as solvated molecules and due to osmotic effect. In concentrated electrolytes, water movement is less due to limited availability of free water as well as a smaller osmotic pressure difference. In highly concentrated aqueous electrolytes, the mass of the PPy/DBS film at the end of each redox cycle is found to drift, which can be controlled by changing the concentration of the electrolyte. The PPy/DBS films were also cycled at different scan rates in various alkali halide aqueous electrolytes of concentrations 0.1 and 1 M to determine the effective diffusion coefficients of alkali ions in the films. The effective diffusion coefficients were found to increase with the concentration of the electrolytes and decrease with the increase in size of cations.

  14. Atomic force microscopy studies of alkali halide surfaces nanostructured by DIET

    Science.gov (United States)

    Goryl, M.; Such, B.; Krok, F.; Meisel, K.; Kolodziej, J. J.; Szymonski, M.

    2005-11-01

    We report on surface topography modification of single crystal alkali halides due to creation of the excitonic states by keV electron irradiation. The DIET—structured surfaces have been studied with nanometer scale resolution by means of a dynamic (non-contact) atomic force microscopy (DFM) in UHV. The force microscopy studies reveal that randomly spread rectangular pits of monolayer depth in the topmost layer of the crystal are formed during irradiation. Growth and coalescence of the pits lead to almost layer-by-layer desorption mode. It is demonstrated that varying surface topography affects the yield of both the halogen and the alkali atom desorption component, as well as velocity spectrum of desorbing halogen atoms (thermal versus non-thermal ratio). We propose a model in which periodic changes of the surface topography with the increasing electron fluence (from initially flat to rough at about half monolayer desorbed, back to flat after a complete monolayer removal) are modulating the surface recombination probability for the excited F-centers. By controlling the population of traps in the bulk these surface processes are causing modulation of the diffusion range of mobile defects migrating from the bulk of the material towards its surface and the bulk recombination probabilities of F- and H-centres.

  15. Investigation of condensation and evaporation of alkali halide crystals by molecular beam methods. VIII. Molecular beam pulse experiments with lithium flouride

    Science.gov (United States)

    Dabringhaus, H.; Meyer, H. J.

    1983-02-01

    Experiments with molecular beam pulses allow the determination of the relaxation times of monomeric, dimeric, and trimeric molecules of lithium fluoride on (100) surfaces of LiF as functions of the crystal temperature T and of the molecular flux jon impinging onto the surface. At high T and low jon the relaxation times increase exponentially with 1/ T. The corresponding activation energies are 0.79, 0.77, and 1.14 eV for the monomers, dimers, and trimers. At lower T and higher jon they become independent of T but increase with decreasing jon. The experiments were performed with different lithium isotopes: 6Li for the impinging molecular beam and 7Li for the crystal. Measurements with dimers and trimers of differing isotopic composition show that the measured relaxation times are independent of the isotope exchange on the surface. Therefore, the Li exchange times are immeasurably small ( < 10 ?s).

  16. Molecular beam scattering from clean surfaces of alkali halides

    International Nuclear Information System (INIS)

    Molecular beam scattering of light gases from in situ cleaved alkali halide surfaces has been studied as a means of developing molecular beam scattering as a surface characterization tool and as a means of obtaining information about the gas atom-solid surface potential interaction. For 4He scattering from LiF carried out under improved resolution the main results are: (1) there are four bound states in the surface potential well, as energies of -5.8, -2.2, -0.6 and -0.1 MeV. (2) Most of the structure designated as ''fine structure'' is due either to transitions to these four levels via various small reciprocal lattice vectors or to the opening of diffraction channels. (3) The transitions involving the (01) and (0 anti 1) reciprocal lattice vectors (i.e., the ones nearly perpendicular to the incident wavevector) are strong; as much as 85 percent of the specular intensity may be removed. Transitions via the other small reciprocal lattice vectors are much weaker. (4) The widths of the lines are consistent with the velocity distribution, which has a half-width of about 2 percent. (5) The observed energies agree fairly well with those calculated for a zeta-function potential, but are not consistent with a Morse potential. The preliminary results for 4He/NaF scattering are that there are three bound-states in the surface potential well and are quite similar to the LiF results. These energies are -5.0, -1.9, and -0.5 MeV. 4He/NaF selective ad -0.5 MeV. 4He/NaF selective adsorption also shows ''fine structure'' and a more detailed analysis is called for here

  17. Anharmonic properties of potassium halide crystals

    OpenAIRE

    Raju, Krishna Murti

    2011-01-01

    An effort has been made to obtain the anharmonic properties of potassium halides starting from primary physical parameters viz. nearest neighbor distance and hardness parameters assuming long- and short- range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second, third and fourth order elastic constants respectively...

  18. Formation of structured nanophases in halide crystals.

    Czech Academy of Sciences Publication Activity Database

    Kulveit, Jan; Demo, Pavel; Polák, Karel; Sveshnikov, Alexey; Kožíšek, Zden?k

    Praha : Czechoslovak Association for Crystal Growth (CSACG), 2012 - (Kožíšek, Z.; Nitsch, K.). s. 46-46 ISBN 978-80-260-2357-9. [Joint Seminar – Development of materials science in research and education /22./. 03.09.2012-07.09.2012, Lednice] R&D Projects: GA ?R GAP108/12/0891 Institutional research plan: CEZ:AV0Z10100521 Keywords : halides * nucleation * nanophases Subject RIV: BM - Solid Matter Physics ; Magnetism

  19. Electronic properties of metal-induced gap states formed at alkali-halide/metal interfaces

    OpenAIRE

    Kiguchi, Manabu; Yoshikawa, Genki; Ikeda, Susumu; Saiki, Koichiro

    2005-01-01

    The spatial distribution and site- distribution of metal induced gap states (MIGS) are studied by thickness dependent near edge x-ray absorption fine structure (NEXAFS) and comparing the cation and anion edge NEXAFS. The thickness dependent NEXAFS shows that the decay length of MIGS depends on rather an alkali halide than a metal, and it is larger for alkali halides with smaller band gap energy. By comparing the Cl edge and K edge NEXAFS for KCl/Cu(001), MIGS are found to be...

  20. Energy distributions of atoms sputtered from alkali halides by 540 eV electrons, Ch.1

    International Nuclear Information System (INIS)

    The emission of halogen and alkali atoms, occurring under bombardment of alkali halides with electrons has been investigated. The electron energy was 540 eV and the temperature of the target was varied between room temperature and 4000C. The energy distribution of the emitted neutral particles was measured with a time of flight method. It was found that either diffusing interstitial halogen atoms or moving holes dominate the sputtering process above 2000C. Below 1500C alkali halides with lattice parameters s/d >= 0.33 show emission of non-thermal halogen atoms. s is the interionic space between two halogen ions in a direction and d is the diameter of a halogen atom. In general the energy distribution of the alkali and halogen atoms is thermal above 2000C, but not Maxwellian. (Auth.)

  1. Voltametric behaviour of neodymium ions in the solutions of alkali halides

    International Nuclear Information System (INIS)

    Systematic studies of Nd(3) coltammetric behaviour in alkali metal halide solutions were carried out to expand the range of background electrolytes for Nd(3) detection and to reveal the influence of cations, anions and pH on registration patterns of Nd(3) solutions

  2. Cluster-Bethe lattice calculation for the electronic structure of hydrogen centers in alkali-halides

    International Nuclear Information System (INIS)

    The Cluster-Bethe lattice (CBL) method to calculate the electronic structure of the hydrogen centers U, U1, U2, U3 in alkali-halides has been used. The results show the adequacy of the CBL in the interpretation of the nature of the optical transitions. (author)

  3. Measurement of velocity of Ultrasonic sound in alkali halide R R solutions with different Normality

    Directory of Open Access Journals (Sweden)

    M. N. Nyayate

    2012-06-01

    Full Text Available Velocity of sound in solutions is very large as compared to that in air, and this velocity is density dependent. In this experiment the alkali halide solutions of different normality was prepared and the velocity of sound was observed using Ultrasonic Interferometer at 2 M Hz of frequency. The velocity of sound was observed to be increasing with increasing Normality of solutions except for the potassium iodide solution, where this change is marginal. As an extension to this experiment sodium halide solutions were tested, and again the change in Sodium iodide was observed to be much less. This showed that the velocity of sound in alkali halide solutions was observed to be frequency dependent also that is at certain frequency for a solution velocity remains almost constant with change in normality.

  4. The self-trapping of anion excitons in alkali halides at elastic deformation

    International Nuclear Information System (INIS)

    The self-trapping of electronic excitations (EE) (excitons, holes and electrons) in alkali halides (AH), fluorides and oxides plays an important roles in luminescence and defect formation. Therein the specific features of self-trapping of EE in various materials are essentially different. In particular, the self-trapping of excitons in some AH (i.e. alkali iodides and bromides) occurs with overcoming of the potential barrier and in other AH (e.g. alkali fluorides and chlorides) such a barrier is absent. Here we develop the continuum theory of self-trapping of within the adiabatic approximation elastically stressed AH. In the continuum model of solids the functional of the total energy of are interacting exciton-phonon system in the deformed ionic crystal just as in the undeformed crystal depends on the dilation ?(r) described by the deformation potential of acoustic phonon, the electrostatic potential ?[r) due to the lattice polarization at optical lattice vibrations and the wave function of exciton chosen for hydro statically and uniaxially stressed 3D crystals. The functionals of the total energy of the interfacing exciton-phonon system E{?(r),?(r),?(r)} are minimized relative to ?, ? and ? for the cases of isotropic and anisotropic 3D crystals. As a result, we obtained the functionals depending on ? and determined their possible extremum. We have show that the linear deformations under the hydrostatic and uniaxial stress at 80 K lead to the decreasing of t 80 K lead to the decreasing of the self trapping barrier for exciton and to the increasing of the luminescence of self-trapped excitons (STE). While the nonlinear deformations under the such stress at 80 K lead to the increasing of the self-trapping barrier for excitons and to the decreasing at the STE luminescence in AH. At T=0 K the small hydrostatic and uniaxial pressures lead to the same effects. Further at hydrostatic and uniaxial compressions of AH the minimums of the adiabatic potentials of quasifree and STE are shifted to higher energies. The above predictions are consistent with the experimental data

  5. Refined potentials for rare gas atom adsorption on rare gas and alkali-halide surfaces

    Science.gov (United States)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1985-01-01

    The utilization of models of interatomic potential for physical interaction to estimate the long range attractive potential for rare gases and ions is discussed. The long range attractive force is calculated in terms of the atomic dispersion properties. A data base of atomic dispersion parameters for rare gas atoms, alkali ion, and halogen ions is applied to the study of the repulsive core; the procedure for evaluating the repulsive core of ion interactions is described. The interaction of rare gas atoms on ideal rare gas solid and alkali-halide surfaces is analyzed; zero coverage absorption potentials are derived.

  6. Correlations for calculating the surface tension and enthalpies of sublimation of alkali halides

    Energy Technology Data Exchange (ETDEWEB)

    Aqra, Fathi, E-mail: fathiaqra2009@hotmail.com

    2014-05-15

    The capability of a new model on predicting the surface tension of molten alkali halides is described. A relationship, with a simple form of calculation, exists between the surface tension (?) at the melting point, molar volume (V), inter-nuclear distance (D) and the enthalpy of sublimation (E{sub s}). The basic idea results from the assumption that all the parameters are constants that are usually easy to acquire. Moreover, two previous models (Furth and Schytil equations) were also checked and applied for calculating surface tension of molten salts. The three formulas have been examined for 20 salts and showed remarkable agreement between calculated and experimental data with a difference of less than 10% for most of the salts studied. The heats of sublimation of alkali halides were, theoretically, calculated and compared to literature values.

  7. Quantum-chemical simulation of production and tunneling recombination of pairs of Frenkel defects in alkali halides

    International Nuclear Information System (INIS)

    Quantum-chemical simulation of the mechanism of non-irradiating annihilation of self-localized exciton resulting in production of Frenkel defects in alkali-halide crystals is performed. LiF crystal is considered, in particular. It is shown that at drawing the anion escaping along the axis together with the following anion up to smaller distance characteristic for H-centre the electron tunneling back in anion vacancy with production of F-, H-centre pair becomes energetically advisable. Calculations of effectiveness of non-irradiating annihilation reveal that release of almost the total energy of self-localized exciton on an anion is possible, and time of transition does not exceed 10-11 s. The non-irradiating channel dominates for tunnel recombination of F-, H-pairs of defects while the irradiating one - for F-Vsub(k)-pairs

  8. A refinement of the Mollwo-Ivey rule for F-centres in alkali halides

    International Nuclear Information System (INIS)

    The simple formula is a very good fit for the detailed variation of the F-center peak absorption energy, for the 16 alkali halides with NaCl structure, excluding CsF. The first term arises from incoherent photon scattering leading to electronic level transitions. The second term is a diffraction term, arising from the coherent scattering of photons from relaxed ionic aggregates around F-centers separated on the average by distances of the order of optical wavelengths

  9. Making Solid Solutions with Alkali Halides (and Breaking Them)

    Science.gov (United States)

    John Brady

    In this exercise, the class will grow a variety of crystals of the same mineral, but with different chemical compositions. These crystals will be made from mixtures of halite (NaCl)and sylvite (KCl) that are melted and cooled. Because K+1 is significantly larger than Na+1,the unit cell is larger in sylvite than in halite. Intermediate compositions have intermediate unit cell sizes. Thus, a measurement of the lattice spacing of the crystalline products of your experiments can be used to determine their chemical composition. The principle goal of these experiments is to demonstrate that solid solutions do occur and that their physical properties vary with their chemical composition. Additional goals include studying the effect of composition on melting, exploring the process of exsolution as a function of temperature, and seeing the effect of fluids and deformation on crystallization kinetics.

  10. EXAFS STUDY OF RELAXATION OF Cu+ IMPURITIES IN ALKALI HALIDES

    OpenAIRE

    Murata, T.; Emura, S.

    1986-01-01

    Cu K-edge EXAFS measurements have been done for NaCl : Cu+ in order to study the lattice relaxation around a cuprous ion. It was found that the bond length of Cu+ and Cl- in NaCl takes almost the same value as that of CuCl crystal. This suggests a very large distortion of the latice around a cuprous ion.

  11. Thermoluminescence in alkali halides irradiated at 80K

    International Nuclear Information System (INIS)

    The thermoluminescence, the thermally stimulated currents and the thermal stability of the F centres induced in pure NaCl and KC1 crystals by X irradiation at 80K have been studied in detail, in the range between 80 and 300K. The thermoluminescent processes induced by illumination at 80K with F light in samples previously irradiated at room temperature has also been studied. It has been clearly observed the existence of thermoluminescent processes due to electrons and holes thermally released from traps, in which the F centres are not involved. The existence of hole-F centre recombination has not been observed. There are several thermoluminescent processes in both materials which are scribed to the recombination of F centres with mobile interstitial halogen atoms thermally released from traps, which are likely monovalent impurities in this temperature interval. The light emitting stage in these processes is originated by the formation of self trapped excitons. (Author) 66 refs

  12. A comparative study of semi-empirical interionic potentials for alkali halides - II

    International Nuclear Information System (INIS)

    A comprehensive study of some semi-empirical interionic potentials is carried out through the calculation of the cohesive energy, relative stability and pressure induced solid-solid phase transformations in alkali halides. The theoretical values of these properties of the alkali halides are obtained using a new set of van der Waals coefficients and zero-point energy in the expression for interionic potential. From the comparison of the present calculations with some previous sophisticated ab-initio quantum-mechanical calculations and other semi-empirical approaches, it is concluded that the present calculations in the simplest central pairwise interaction description with the new values of the van der Waals coefficients and zero-point energy are in better agreement with the experimental data than the previous calculations. It is also concluded that in some cases the better choice of the interionic potential alone in the simplest semi-empirical picture of interaction gives an agreement of the theoretical predictions with the experimental data much superior to the ab-initio quantum mechanical approaches. (author)

  13. Potential differences between chlorine and bromine electrode and between chlorine and iodine electrode in melts of the corresponding alkali-metal halides

    International Nuclear Information System (INIS)

    Halogen electrodes, according to the authors, are the most convenient electrodes for thermodynamic studies of reactions involving halogens in molten alkali metal halides when the emf method is used. The authors measured the potential differences between the chlorine and bromine electrode and between the chlorine and iodine electrode in cells described here. From the results of measurements at different temperatures, the authors generalized interpolation relations between the potentials of the bromine and iodine electrode in molten alkalimetal bromides and iodides and their mixtures relative to the chlorine electrode in chlorides of the same metals, on one hand, and the temperature and cation's crystal radius on the other hand

  14. VUV-induced processes in alkali halide dimer molecules - how well does the ionic approach work?

    International Nuclear Information System (INIS)

    Full text: The studies of the basic properties of alkalide halides are largely motivated by the almost pure ionic character of their molecular bond, allowing to use simple ionic models that are often sufficient to describe the experimental results. On the other hand, modern synchrotron radiation sources and advances in spectroscopic techniques make it possible to study a broad range of photo-induced processes where novel aspects can emerge, requiring more advanced analysis. Studying the dimer forms of ionic molecules is of interest also since the effects of the changed symmetry of the environment (dimers vs. monomers or solids) on the constituent ions can be observed. Here, the inner valence excitations and their electronic and nuclear decay processes in cesium halides dimers are investigated. Firstly, the primary resonant photoabsorption structures of both the monomer and dimer forms are compared and calculations based on the crystal field approach are used to model the spectra. Secondly, molecular fragmentation is studied using the partial ion yield technique, and the electronic decay channels leading to specific molecular fragmentation patterns are identified. It is shown that the nature of the electronic decay channels changes across the photoexcitation spectrum and energy calculations based on the ionic model are used to explain the observations. Both the successes and the shortcomings of the ionic approach are demonstrated in the case of cesium halide dimersed in the case of cesium halide dimers

  15. Studies of non-proportionality in alkali halide and strontium iodide scintillators using SLYNCI

    Energy Technology Data Exchange (ETDEWEB)

    Ahle, Larry; Bizarri, Gregory; Boatner, Lynn; Cherepy, Nerine J.; Choong, Woon-Seng; Moses, William W.; Payne, Stephen A.; Shah, Kanai; Sheets, Steven; Sturm, Benjamin, W.

    2010-10-14

    Recently a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument to study the non-proportionality of scintillators. This device, known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument), has can completely characterize a sample with less than 24 hours of running time. Thus, SLYNCI enables a number of systematic studies of scintillators since many samples can be processed in a reasonable length of time. These studies include differences in nonproportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. The results of such recent studies are presented here, including a study of various alkali halides, and the impact of europium doping level in strontium iodide. Directions of future work area also discussed.

  16. Studies of Non-Proportionality in Alkali Halide and Strontium Iodide Scintillators Using SLYNCI

    Energy Technology Data Exchange (ETDEWEB)

    Ahle, L; Bizarri, G; Boatner, L; Cherepy, N J; Choong, W; Moses, W W; Payne, S A; Shah, K; Sheets, S; Sturm, B W

    2009-05-05

    Recently a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument to study the non-proportionality of scintillators [1-3]. This device, known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument), has can completely characterize a sample with less than 24 hours of running time. Thus, SLYNCI enables a number of systematic studies of scintillators since many samples can be processed in a reasonable length of time. These studies include differences in nonproportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. The results of such recent studies are presented here, including a study of various alkali halides, and the impact of europium doping level in strontium iodide. Directions of future work area also discussed.

  17. Chemistry of alkali cation exchanged faujasite and mesoporous NaX using alkyl halides and phosphates

    Science.gov (United States)

    Lee, Min-Hong

    The purpose of this work was to increase the reactivity of Faujasite X (NaX) zeolite toward the reactive decontamination of materials subject to nucleophilic attack by means of zeolite cation optimization and by means of the synthesis of mesoporous Faujasite X. Primary alkyl halides and trialkyl phosphates have been the test materials on which the cation-optimized and mesoporous zeolites have been tested. In the alkali cation optimization work, reactions of methyl iodide and 1-chloropropane with alkali metal cation exchanged Faujasite zeolite X were investigated at room temperature. The reactivity of the framework and the product formation were shown to depend on zeolite framework counter-cation. A quantitative study of zeolite product formation has been carried out, primarily using solid-state NMR spectroscopy. Large alkali cations showed preference toward substitution chemistry. In contrast, alkyl halide exposed LiX and NaX zeolites underwent both substitution and elimination. Subsequently introduced water molecules led to hydrolysis of framework species that was sensitive to framework counter-cation. The mesoporous NaX zeolites work undertakes to test whether an improvement in surface chemical reactivity can be achieved by introducing mesopores into the already reactive nucleophilic microporous NaX zeolite. Incorporation of the polydiallyl dimethyl ammonium chloride (PDADMAC) template and the formation of mesopores in Faujasite X zeolite (NaX) were successful and well-characterized. The mesopores are proposed to have occurred from incorporation of the cationic PDADMAC polymer into the zeolite by compensating zeolite framework charge. Subsequent sodium cation exchange of calcined mesoporous NaX was shown to restore the chemical reactivity characteristic of as-synthesized NaX. Trialkyl organophosphorous compounds underwent substitution reactions. The reactivity of both microporous and mesoporous Faujasite zeolite X and the product formation was shown to depend on the length of the alkyl chain. Although introduced mesopores alleviated the limited reagent diffusion to reactive sites due to the microporosity of the NaX zeolites, no marked improvement in the product yields was achieved with either the 1-chloroalkanes or the trialkyl phosphates test compounds, regardless of alkyl chain length. The disappointing results have been attributed to lack of substantial net increase in the numbers of zeolite nucleophilic sites accompanying mesopore introduction.

  18. Building alkali-metal-halide layers within a perovskite host by sequential intercalation: (A(2)Cl)LaNb(2)O(7) (A = Rb, Cs).

    Science.gov (United States)

    Choi, Jonglak; Zhang, Xiao; Wiley, John B

    2009-06-01

    Alkali-metal-halide layers were constructed within Dion-Jacobson (DJ) layered perovskites by a two-step sequential intercalation method. Reductive intercalation with an alkali metal, followed by oxidative intercalation with chlorine gas, leads to the formation of the compounds, (A(2)Cl)LaNb(2)O(7) (A = Rb, Cs). Rietveld refinement of X-ray powder diffraction data shows that an alkali-metal-halide layer is formed between the perovskite blocks. The alkali-metal cation is eight-coordinate with four oxygens from the perovskite layer and four chlorides from the new halide layer; this environment is similar to cesium in the CsCl structure (B2). Thermal analysis indicates that these are low-temperature phases where decomposition begins by 400 degrees C. Details on the synthesis and characterization of this set of compounds are presented, and the general utility of this approach discussed. PMID:19466802

  19. Alkali halide decomposition and desorption by photons-the role of excited point defects and surface topographies

    International Nuclear Information System (INIS)

    Our recent work on photon-stimulated desorption of alkali halide surfaces has been reviewed. Most of the experimental data are presented for the first time. This new material is supplemented with two examples of our work published previously (see Szymonski et al 1996 Surf. Sci. 363 229; 2002 Acta Phys. Pol. 33 2237). The results are discussed and compared with relevant experimental and theoretical work by other authors. In particular, we focus on two aspects of the studies: high resolution AFM imaging of desorbed surfaces, and measurements of mass selected fluxes of the desorbing atoms. It is found that, at initial stages of the UV-photon stimulated desorption, the process is occurring in a 'layer-by-layer' mode as a result of growth and linking of monatomic pits on the surface. This results in periodic changes of surface topography from atomically flat to rough with a period equal to the time needed for desorption of 1 ML. Such periodic changes of the surface topography affect the efficiency of the desorption and result in oscillatory dependence of the emitted particle yields versus photon fluence. Careful analysis of the yields reveals that during irradiation there is a substantial number of stable ground state F-centres accumulated under the surface. The number of accumulated defects is changing periodically with the photon fluence in anti-correlation with the desorption yields. Based on the mentioned results, we argue that the production of F-centres and their int the production of F-centres and their interaction with the surface are, in fact, the limiting factor for PSD. To test the validity of this statement a series of desorption experiments for the crystal co-irradiated with visible light (with a wavelength corresponding to the F-centre absorption band) and UV photons have been performed. A dramatic increase in the desorption yield, as well as pronounced changes in the surface erosion process, have been found

  20. Alkali halide decomposition and desorption by photons—the role of excited point defects and surface topographies

    Science.gov (United States)

    Szymonski, Marek; Droba, Anna; Goryl, Maria; Kolodziej, Jacek J.; Krok, Franciszek

    2006-08-01

    Our recent work on photon-stimulated desorption of alkali halide surfaces has been reviewed. Most of the experimental data are presented for the first time. This new material is supplemented with two examples of our work published previously (see Szymonski et al 1996 Surf. Sci. 363 229 2002 Acta Phys. Pol. 33 2237). The results are discussed and compared with relevant experimental and theoretical work by other authors. In particular, we focus on two aspects of the studies: high resolution AFM imaging of desorbed surfaces, and measurements of mass selected fluxes of the desorbing atoms. It is found that, at initial stages of the UV-photon stimulated desorption, the process is occurring in a 'layer-by-layer' mode as a result of growth and linking of monatomic pits on the surface. This results in periodic changes of surface topography from atomically flat to rough with a period equal to the time needed for desorption of 1 ML. Such periodic changes of the surface topography affect the efficiency of the desorption and result in oscillatory dependence of the emitted particle yields versus photon fluence. Careful analysis of the yields reveals that during irradiation there is a substantial number of stable ground state F-centres accumulated under the surface. The number of accumulated defects is changing periodically with the photon fluence in anti-correlation with the desorption yields. Based on the mentioned results, we argue that the production of F-centres and their interaction with the surface are, in fact, the limiting factor for PSD. To test the validity of this statement a series of desorption experiments for the crystal co-irradiated with visible light (with a wavelength corresponding to the F-centre absorption band) and UV photons have been performed. A dramatic increase in the desorption yield, as well as pronounced changes in the surface erosion process, have been found.

  1. Optical Spectra and Energy Levels of Divalent Ytterbium and Samarium Ions in Some Alkali Halides.

    Science.gov (United States)

    Mejeha, Ihebrodike Maurice

    Available from UMI in association with The British Library. Requires signed TDF. This study is concerned with the measurement and analysis of the optical absorption spectra of divalent samarium (Sm^{2+}) and ytterbium (Yb^{2+}) ions in potassium and rubidium halide crystals. To incorporate the ions into the crystals, the latter were heated in (the appropriate) metal vapour. The optical absorption spectra of the impurity-doped crystals were measured and are ascribed to 4f^{N+1}to 4f^ {N}5d electronic transitions. For the first time, the optical spectra of Sm^{2+ } and Yb^{2+} ions in RbBr and RbI crystals are reported. In the case of Yb^{2+} ions in RbX, (X=Cl,Br,I) crystals, intermediate coupling calculations using J_1j - coupled basis functions give a satisfactory agreement between experimental and theoretical energy levels of the ions, by assuming that the effective site symmetry of the substitutional impurity ions is octahedral. However, the Slater-Condon and spin-orbit parameters that give the best fit between theory and experiment are reduced by up to 44% from the free-ions values. In the case of Sm^{2+} ions in KX and KbX crystals, theoretical calculation of the energy levels (assuming octahedral approximation) was based on the model in which the 4f^5 core electron states, best described in terms of LS-coupled basis functions, are coupled to the 5d electron states which are strongly perturbed by the crystal field. In this model, the agreement between theoretical and experimental energy levels is also quite satisfactory. Also found, are sets of absorption bands whose spectral positions and behaviour can best be explained by assuming electronic transitions from the ground states of the ions to the bonding molecular orbitals formed by the overlap of the 6s atomic orbitals of the impurity ions and the (n + 1)s atomic orbitals of the ligand ions. Preliminary investigations of the effect of thermal ageing on the optical spectra of RbBr : Yb^ {2+} crystals suggest that the Yb ^{2+} ions exist in three separate phases (in the crystals) among which is the Suzuki phase.

  2. Photodissociation comprehensive study of OH- on alkali halides and their interaction with colour centers

    International Nuclear Information System (INIS)

    This work shows that the OH- defect induces changes in the electronics processes of the alkali halides such as in radiation damage and optical cycles of colour centers. Two cases were considered: with the presence of an OH- ion in the (1) excited state and (2) in the ground state; 1) the comprehensive study of resonant OH- photodissociation in several hosts showed that deep traps (for electrons) can be produced from the OH- dissociation. These traps can be effective for the capture of electrons produced in the radiation damage of the lattice as well as for trapping electrons from ionized color centers. It was observed a second channel (new) for the de-excitation of the (OH-)* molecule in KI and RbI. This effect can be effective only when the lattice around the molecule holds a large enough interstitial space. This new mechanism is responsible for the strong production at LNT of F centers and OH0 molecules at the expenses of OH- defects. Considering the complete investigation of the full cycle it was proposed a phenomenological model that would explain the observed behaviour when one covers a wide variation of lattice parameters (KCl -> RbI); 2) It was verified that the OH- ion present in the lattice induces strong changes in the de-excitation processes of electronic defects with a spread out wave function (like F centers). A change in the reorientation behaviour of excited F2 and F+2 centers was also verified. Two main effects should be mentioned: A) The induced de-excitation is very fast and non-radiative on F centers. B) Another type of system investigated (F2 and F+2) has shown an intense increase of the speed of reorientation of the F2 and F+2 excited centers. (autor)

  3. Low-Energy Grazing Ion-Scattering From Alkali-Halide Surfaces: A Novel Approach To C-14 Detection

    Science.gov (United States)

    Meyer, F. W.; Galutschek, E.; Hotchkis, M.

    2009-03-01

    Carbon-14 labeled compounds are widely used in the pharmaceutical industry, e.g., as tracers to determine the fate of these compounds in vivo. Conventional accelerator mass spectrometry (AMS) is one approach that offers sufficiently high sensitivity to avoid radiological waste and contamination issues in such studies, but requires large, expensive facilities that are usually not solely dedicated to this task. At the ORNL Multicharged Ion Research Facility (MIRF) we are exploring a small size, low cost alternative to AMS for biomedical 14C tracer studies that utilizes ECR-ion-source-generated keV-energy-range multicharged C beams grazingly incident on an alkali halide target, where efficient negative ion production by multiple electron capture takes place. By using C ion charge states of +3 or higher, the molecular isobar interference at mass 14, e.g. 12CH2 and 13CH, is eliminated. The negatively charged ions in the beam scattered from the alkali halide surface are separated from other scattered charge states by two large acceptance (˜15 msr) stages of electrostatic analysis. The N-14 isobar interference is thus removed, since N does not support a stable negative ion. Initial results for C-14 detection obtained using C-14 enriched CO2 from ANSTO will be described.

  4. Dependences of molar volumes in solids, partial molal and hydrated ionic volumes of alkali halides on covalent and ionic radii and the golden ratio.

    Czech Academy of Sciences Publication Activity Database

    Heyrovská, Raji

    2007-01-01

    Ro?. 436, ?. 1-3 (2007), s. 287-293. ISSN 0009-2614 R&D Projects: GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z50040702 Keywords : alkali halides * ionic hydration * golden ratio Subject RIV: BO - Biophysics Impact factor: 2.207, year: 2007

  5. Sensitivity of alkali halide scintillating calorimeters with particle identification to investigate the DAMA dark matter detection claim

    CERN Document Server

    Nadeau, Patrick; Di Stefano, P C F; Lanfranchi, J -C; Roth, S; von Sivers, M; Yavin, Itay

    2014-01-01

    Scintillating calorimeters are cryogenic detectors combining a measurement of scintillation with one of phonons to provide particle identification. In view of developing alkali halide devices of this type able to check the DAMA/LIBRA claim for the observation of dark matter, we have simulated detector performances to determine their sensitivity by two methods with little model-dependence. We conclude that if performance of the phonon channel can be brought in line with those of other materials, an exposure of 10 kg-days would suffice to check the DAMA/LIBRA claim in standard astrophysical scenarios. Additionally, a fairly modest array of 5 kg with background rejection would be able to directly check the DAMA/LIBRA modulation result in 2 years.

  6. Development of processes for the production of solar grade silicon from halides and alkali metals, phase 1 and phase 2

    Science.gov (United States)

    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.

  7. A Review of Luminescent Anionic Nano System: d10 Metallocyanide Excimers and Exciplexes in Alkali Halide Hosts

    Directory of Open Access Journals (Sweden)

    Howard H. Patterson

    2013-06-01

    Full Text Available Dicyanoaurate, dicyanoargentate, and dicyanocuprate ions in solution and doped in different alkali halide hosts exhibit interesting photophysical and photochemical behavior, such as multiple emission bands, exciplex tuning, optical memory, and thermochromism. This is attributed to the formation of different sizes of nanoclusters in solution and in doped hosts. A series of spectroscopic methods (luminescence, UV-reflectance, IR, and Raman as well as theoretical calculations have confirmed the existence of excimers and exciplexes. This leads to the tunability of these nano systems over a wide wavelength interval. The population of these nanoclusters varies with temperature and external laser irradiation, which explains the thermochromism and optical memory. DFT calculations indicate an MLCT transition for each nanocluster and the emission energy decreases with increasing cluster size. This is in agreement with the relatively long life-time for the emission peaks and the multiple emission peaks dependence upon cluster concentration.

  8. Absorption measurements of mixed silver halide crystals and fibers by laser calorimetry.

    Science.gov (United States)

    Bunimovich, D; Nagli, L; Katzir, A

    1994-01-01

    The absorption coefficients of mixed silver halide crystals and fibers were measured by different laser calorimetric methods: adiabatic for crystals and isothermal for fibers. The composition dependence of the bulk absorption coefficients ?(b) of crystals and polycrystalline fibers at 10.6-µm (CO(2) radiation) was investigated. It was found that the crystal surface absorption ?(s) is dependent on the surface polishing quality. All experimental results of ?(b) are smaller than those reported in the literature. PMID:20861998

  9. Cu halide nanoparticle formation by diffusion of copper in alkali halide crystals

    Directory of Open Access Journals (Sweden)

    A. P\\u00E9rez-Rodr\\u00EDguez

    2006-01-01

    Full Text Available Atomos de cobre han sido introducidos por difusión en cristales de NaCl, KCl y KBr a 500±C. Los cristales han sido analizados óptimamente con medidas de fotoluminiscencia y por microscopía electrónica de barrido. Los espectros de emisión y excitación, medidos a baja temperatura muestran el efecto de confinamiento de exciton, indicando la formación de nanopartículas de CuX (X=Cl, Br, lo cual ha sido confirmado por imágenes de microscopía electrónica. Este método es propuesto como un método alternativo para obtener nanopartículas de CuX en cristales halogenuros alcalinos.

  10. Ca-Fe and Alkali-Halide Alteration of an Allende Type B CAI: Aqueous Alteration in Nebular or Asteroidal Settings

    Science.gov (United States)

    Ross, D. K.; Simon, J. I.; Simon, S. B.; Grossman, L.

    2012-01-01

    Ca-Fe and alkali-halide alteration of CAIs is often attributed to aqueous alteration by fluids circulating on asteroidal parent bodies after the various chondritic components have been assembled, although debate continues about the roles of asteroidal vs. nebular modification processes [1-7]. Here we report de-tailed observations of alteration products in a large Type B2 CAI, TS4 from Allende, one of the oxidized subgroup of CV3s, and propose a speculative model for aqueous alteration of CAIs in a nebular setting. Ca-Fe alteration in this CAI consists predominantly of end-member hedenbergite, end-member andradite, and compositionally variable, magnesian high-Ca pyroxene. These phases are strongly concentrated in an unusual "nodule" enclosed within the interior of the CAI (Fig. 1). The Ca, Fe-rich nodule superficially resembles a clast that pre-dated and was engulfed by the CAI, but closer inspection shows that relic spinel grains are enclosed in the nodule, and corroded CAI primary phases interfinger with the Fe-rich phases at the nodule s margins. This CAI also contains abundant sodalite and nepheline (alkali-halide) alteration that occurs around the rims of the CAI, but also penetrates more deeply into the CAI. The two types of alteration (Ca-Fe and alkali-halide) are adjacent, and very fine-grained Fe-rich phases are associated with sodalite-rich regions. Both types of alteration appear to be replacive; if that is true, it would require substantial introduction of Fe, and transport of elements (Ti, Al and Mg) out of the nodule, and introduction of Na and Cl into alkali-halide rich zones. Parts of the CAI have been extensively metasomatized.

  11. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert

    2011-07-01

    Full Text Available The chain polymer [{Cd(?-X2py2}1?] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  12. Characterization of alkali halides doped 1-(2-methoxy benzyloxy)-8- hydroxy-9,10-anthraquinone films for photovoltaic applications

    Science.gov (United States)

    Mahajan, Aman; Singh, Mandeep; Gupta, Himani; Bedi, R. K.; Kumar, S.; Aswal, D. K.

    2012-06-01

    Thin films of 1-(2-methoxy benzyloxy)-8-hydroxy-9, 10-anthraquinone (AQ) have been prepared by hot wall technique onto glass substrates kept at 348 K in a vacuum of 10-5 Torr. Chemical modifications of films have been performed by their treatment with different alkali halides. The films so obtained are systematically studied for their electrical and optical properties. The electrical conductivities of the resulting films exhibited semiconductor-like temperature dependence in the experimental range studied. LiCl and LiBr doped films exhibit almost three orders of magnitude higher conductivity, than untreated films, whereas NaCl, NaBr and KBr do not show any remarkable change in the conductivity. Analysis of optical absorption measurements indicate that the interband transition energies of films lie in the range of 2.57-2.66 eV. Keeping in view the electrical and optical properties of films, ITO/AQ/Al solar cells have been fabricated and characterized. The J-V characteristics of these devices are found to be in good agreement with standard diode equation. Power conversion efficiency of Li doped AQ based devices are found to increase by an order of two as compared to undoped AQ based devices.

  13. Thermodynamics of small alkali metal halide cluster ions: comparison of classical molecular simulations with experiment and quantum chemistry.

    Science.gov (United States)

    Vlcek, Lukas; Uhlik, Filip; Moucka, Filip; Nezbeda, Ivo; Chialvo, Ariel A

    2015-01-22

    We evaluate the ability of selected classical molecular models to describe the thermodynamic and structural aspects of gas-phase hydration of alkali metal halide ions and the formation of small water clusters. To understand the effect of many-body interactions (polarization) and charge penetration effects on the accuracy of a force field, we perform Monte Carlo simulations with three rigid water models using different functional forms to account for these effects: (i) point charge nonpolarizable SPC/E, (ii) Drude point charge polarizable SWM4-DP, and (iii) Drude Gaussian charge polarizable BK3. Model predictions are compared with experimental Gibbs free energies and enthalpies of ion hydration, and with microscopic structural properties obtained from quantum DFT calculations. We find that all three models provide comparable predictions for pure water clusters and cation hydration but differ significantly in their description of anion hydration. None of the investigated classical force fields can consistently and quantitatively reproduce the experimental gas-phase hydration thermodynamics. The outcome of this study highlights the relation between the functional form that describes the effective intermolecular interactions and the accuracy of the resulting ion hydration properties. PMID:25513841

  14. Temperature dependence of the rate of reactions of the solvated electron in irradiated melts of alkali metal halides

    International Nuclear Information System (INIS)

    The temperature dependence of the rate of disappearance of e-/sub s/ in molten alkali metal halides in the presence of various electron acceptors, was investigated so that data on the mechanism of the reactions of solvated electrons (es) in melts could be investigated. The investigation was conducted by the method of microsecond pulsed radiolysis with optical recording. A U-12 linear electron accelerator was used as the radiation source (energy of electrons 5 NeV, duration of pulse 2.3 ?sec). The parameters of the rapid-action spectro-photometric setup, techniques of preparation of the samples and irradiation correspond to those described in previous reports. To conduct the experiments in a wide range of temperatures, melts of NaC1-CsC1 (34/66 mole %) and LiBr-KBr (60/40 mole %) mixtures, the melting points of which are 493 and 3480C, respectively, were selected as the main systems. The disappearance e-/sub s/ in the investigated melts proceeds very rapidly even in the absence of an electron acceptor (in less than 3 ?sec after passage of the pulse). A quatitative measurement of the reactivity of e-/sub s/, was conducted on the basis of the dependence of its limiting concentration during the pulse on the concentration of the introduced acceptor

  15. Alkali atoms, dimers, exciplexes and clusters in 4He crystals

    International Nuclear Information System (INIS)

    Full text: A closed-shell He atom and a single-electron alkali atom strongly repel each other because of the Pauli principle. As a consequence, an alkali atom immersed into condensed (superfluid or solid) 4He forms a spherical bubble state, in which the alkali repels the He quantum fluid/solid by imposing its own symmetry on the local He environment. For 15 years we have investigated such atomic bubbles in solid 4He using optical and magnetic resonance spectroscopy. In this talk I will first review our high resolution magnetic resonance studies performed on solid He matrix-isolated alkali atoms in the radio-frequency and microwave domains with special emphasis on their sensitive dependence on the crystalline structure (body-centered cubic, bcc, versus hexagonally close-packed, hcp) of the helium matrix. In recent years we have extended the purely atomic studies to larger bound complexes, such as exciplexes, dimers and clusters. I will present some of our intriguing recent results: in their respective ground states, alkali and He atoms are the worst enemies in the periodic table and strongly repel each other. Excited alkali atoms, however, attract He atoms and form bound states (so-called exciplexes), in which up to 7 He atoms can be attached to one alkali atom. Cs2 and Rb2 dimers in solid He can be excited via a large variety of absorption bands, and the deexcitation proceeds either by photodissociation or by emission of radby photodissociation or by emission of radiation. We made the strange observation that, irrespective of the excitation band, dimer fluorescence is only emitted on the (1)3?u ? X1?g triplet-singlet transition which is forbidden in the free dimer. When the first excited P1/2 state of an alkali atom is populated by direct atomic excitation, it fluoresces at 879 nm (1.7 % blueshifted from the free atomic transition at 894 nm), a quantitatively well explained fact. However, when the same state is populated by photodissociation of the dimer, the emission wavelength is 885 nm. We attribute this effect to the formation of an entangled diatomic bubble state. The doped region of the He crystal has a bluish color that originates from Mie scattering by alkali clusters, the size distribution of which can be inferred from the extinction spectrum. When the doped He crystal is molten by lowering the He pressure, the doped (column-shaped) region remains solid at pressures, where pure He is superfluid. We present experimental support for our hypothesis that this new form of solid He is an amorphous or crystalline ionic structure formed by snowballs (nanoscopic solid He structures formed around positive ions) and electron bubbles. (author)

  16. Effect of Auger neutralization on yields of He ions backscattered and alkali ions sputtered from the surface of alkali halides by keV He ion impact

    International Nuclear Information System (INIS)

    The yields of ions and neutrals backscattered and alkali ions sputtered from LiF crystals by keV He+ ion impact have been measured by means of the coaxial impact collision ion scattering spectroscopy in time of flight analysis mode using the charging-up effect. It is found that as the charging-up potential increases due to continuous irradiation of the pulsed ion beam, the time of flight of the He+ ions backscattered shifts toward the shorter time, while that of the neutrals backscattered shifts toward the longer, and that of Li ions sputtered also shifts much more clearly toward the shorter. The charging-up potential has been estimated as a function of irradiation time of the pulsed ion beam from the time of flight data and the ion to neutral ratio in the backscattering yields is estimated to be about 0.15. The mechanisms for ionization on He and sputtering of alkali ions are discussed in terms of charging-up and trion (bihole and electron) produced by Auger neutralization of keV He+ ions at the target surface

  17. A thermodynamic analysis of the first solvation shells of alkali and halide ions in liquid water and in the gas phase

    Science.gov (United States)

    Grunwald, Ernest; Steel, Colin

    Let n denote the number of water molecules in the nearest-neighbour shell (NS) of an ion J± in liquid water, and denote J± ·nH2O in the gas phase by J± · NSG (g). The standard free energy of hydration ?G°hyd (J± ·NSG) can then be deduced by a thermodynamic cycle involving ?G°n for the formation of J± · NSG (g) and ?G°hyd for the transfer of J± (g) to water. Values of ?G°hyd (J± ·NSG) for alkali and halide ions are substantial, ranging from 48 % to 86 % of ?G0hyd. The values of ?G0hyd(J± ·NSG) can be accounted for largely by the calculated work-electrostatic (?Welec) and surface (?Wsurt)-in the process J± ·NSG (g) ? J± (aq). ?Welec is the major contributor. ?Wsurf depends on whether (i) J± ·NSG (g) can be represented by a cluster consisting of the ion and n separate water molecules, or (ii) there is some molecular complex formation within that cluster. In fact, ?Wsurt < 20 kJ mol-1 for the alkali ions and of the order of 100 kJ mol-1 for the halide ions. A reasonable case can be built that the alkali ions and some of the n water molecules form molecular complexes while the anions are better represented by case (i).

  18. Coloration of cadmium halide crystals due to reactor irradiation at low temperature

    International Nuclear Information System (INIS)

    The optical absorption spectra and ESR spectra of cadmium halide crystals were measured after the reactor irradiation at low temperature to study the coloration. The irradiated neutron dose was about 5 x 1017 n/cm2. In the measurement of ESR spectra, the crystal was rotated around the v-axis (the two-fold axis) in the magnetic field of fixed direction. The optical absorption spectra showed that the Cd3+ center was generated. From the analysis of the angular dependence of ESR spectra, the centers of C(2h) symmetry and the centers of D(3d) symmetry were considered to be generated. The models of these centers were considered, and the angular dependence was analyzed. It can be concluded from the present experiment that the coloration of cadmium halide crystals is recognized as the results of the reactor irradiation at low temperature. (Kato, T.)

  19. Electron paramagnetic resonance, optical transmission spectra and DC conductivity studies of vanadyl-doped alkali halide borate glasses

    International Nuclear Information System (INIS)

    Electron paramagnetic resonance, optical transmission spectra and DC conductivity of the glasses 2xMX·(0.30-x)M2O·0.70B2O3 (M=Na or K; X=Cl or Br) (0.01?x?0.10) containing 2.0 mol% of V2O5 have been studied. The spin-Hamiltonian parameters (SHP) of the VO2+ ions, the dipolar hyperfine parameter, P, the Fermi contact interaction parameter, K, and the molecular orbital coefficients (?2 and ?2) have been calculated. It is observed that in KX·K2O·B2O3 (X=Cl or Br) glasses, the tetragonal nature of V4+O6 complex decreases with KBr for x?0.05. An increase in the 2KX:K2O ratio (x?0.05) also results in the contraction of 3dxy orbit of the unpaired electron in the vanadyl ion, whereas in case of NaX·Na2O·B2O3 (X=Cl or Br) glasses, the SHP are independent of change in 2NaX:M2O ratio. It is observed that the SHP in these alkali halide borate glasses are independent of the theoretical optical basicity, ?th. It is also observed that the DC conductivity increases with increase in temperature. The order of conductivity is 10-6 ?-1 m-1 at low temperatures and 10-4 ?-1 m-1 at high temperatures. In MCl·M2O·B2O3 (M=Na or K) glasses, the conductivity increases and tivity increases and the activation energy decreases with an increase in mol% of the NaCl or KCl content whereas, in MBr·M2O·B2O3 (M=Na or K) glasses, the conductivity first increases and then decreases with mol% of the MBr content

  20. Crystallization of iron phosphate glass containing mixed alkali oxides

    International Nuclear Information System (INIS)

    Iron phosphate glass (IPG) is a versatile alternate glass matrix for immobilization of high level nuclear waste. In the present work, 20 wt % mixed alkali oxides (added in the form of eutectic chlorides, LiCl-55 wt % KCl) were immobilized in IPG and the glass waste form was characterized by X-ray diffraction (XRD) technique. Crystallization behavior was studied by using Differential Scanning Calorimetry (DSC). Good glass forming characteristics, high % of waste loading and good chemical durability are the superior salient features of a versatile iron phosphate glass (IPG) as a host for nuclear waste immobilization. In the present work, the possibility of vitrification of 20 wt % of LiCl-KCl eutectic in IPG was explored along with its crystallization studies in order to study the feasibility of immobilizing pyrometallurgical chloride waste

  1. The role of alkali additives in the crystallization of ferroelectric potassium lithium niobate crystals

    Science.gov (United States)

    Péter, Á.; Hajdara, I.; Szaller, Zs.; Lengyel, K.; Kovács, L.

    2013-05-01

    Ferroelectric K3Li2Nb5O15 (KLN-1) crystals have been grown by the top-seeded solution growth method from pure, Na+, Rb+ and Cs+ doped melt. The impact of alkali additives was assessed all over the entire pulling range by investigating the variation of the structural and physical properties by using spectroscopic and dielectric methods. The incorporation of alkali homologs has been correlated with their ionic radii: Na+ ions were found to enter both Li and K sites with high segregation coefficient (k˜1.6), Rb+ ions were detected only at K sites (k˜0.34) and Cs+ ions practically did not incorporate into the lattice (k˜0.12). Alkali additives have been found to play a dual role in the growth process by affecting the crystallization temperature and promoting the K and Li site occupancy. By decreasing the crystallization temperature the Cs2O additive reduced the concentration both of the antisite Nb ions at Li site and that of alkali vacancies; therefore it can be considered as a promising fluxing agent in the growth of KLN crystals.

  2. Thermoluminescence in alkali halides irradiated at 80K; Termoluminiscencia en haluros alcalinos irradiados a 80K

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez de Castro, M.

    1978-07-01

    The thermoluminescence, the thermally stimulated currents and the thermal stability of the F centres induced in pure NaCl and KC1 crystals by X irradiation at 80K have been studied in detail, In the range between 80 and 300K. The thermoluminescent processes induced by illumination at 80K with F light in samples previously irradiated at room temperature has also been studied. It has been clearly observed the existence of thermoluminescent processes due to electrons and holes thermally released from traps, in which the F centres are not involved. The existence of hole-F centre recombination has not been observed. There are several thermoluminescent processes in both materials which are scribed to the recombination of F centres with mobile interstitial halogen atoms thermally released from traps, which are likely monovalent impurities in this temperature interval. The light emitting stage in these processes is originated by the formation of self trapped excitons. (Author) 66 refs.

  3. In-situ investigation of surface reactions on alkali halides by atomic force microscopy

    International Nuclear Information System (INIS)

    In-situ AFM images have been produced of dissolution processes on NaCl and KBr single crystals under different organic solvents. Using a home-built sample holder stable imaging conditions have been achieved and atomic resolution could be obtained on both materials. Dissolution rates have been determined quantitatively from the AFM images and compared with empirical solvent parameters such as acceptor number AN and ET(30) value. The AFM results are in agreement with the expected behaviour of the liquids. Dissolution rates could be controlled using mixtures of polar and non polar solvents. The results are a basis for further investigations of other systems and technologically important processes such as corrosion and surface modification. (orig.)

  4. Differential calorimeter and temperature controller for stored energy measurements in irradiated alkali halides

    International Nuclear Information System (INIS)

    The design and performance of a simple temperature-controlled differential calorimeter are presented. This system allows to measure radiation-induced stored energy in insulators, above room temperature with a differential thermal analysis method. With platelets of KC1 single crystals, the base lines obtained for T2 T1 (with T2: irradiated sample temperature and T1: reference sample temperature) show a smooth drift less of 0,2 degree centigree in the interval from 25 to 400 degree centigree. The discrepancy between two consecutive base lines is less than ± 0,02 degree centigree which implies a calorimeter sensitivity of about ±0,004 cal/g. This sensitivity allows to measure stored energy release in samples with a color center concentration low enough to be directly measured with a spectrophotometer so that a search for correlations among the features of the stored energy spectrum and the color center annealing can be made. (Author) 13 refs

  5. Dipole-driven self-organization of zwitterionic molecules on alkali halide surfaces

    Directory of Open Access Journals (Sweden)

    Laurent Nony

    2012-03-01

    Full Text Available We investigated the adsorption of 4-methoxy-4?-(3-sulfonatopropylstilbazolium (MSPS on different ionic (001 crystal surfaces by means of noncontact atomic force microscopy. MSPS is a zwitterionic molecule with a strong electric dipole moment. When deposited onto the substrates at room temperature, MSPS diffuses to step edges and defect sites and forms disordered assemblies of molecules. Subsequent annealing induces two different processes: First, at high coverage, the molecules assemble into a well-organized quadratic lattice, which is perfectly aligned with the directions of the substrate surface (i.e., rows of equal charges and which produces a Moiré pattern due to coincidences with the substrate lattice constant. Second, at low coverage, we observe step edges decorated with MSPS molecules that run along the direction. These polar steps most probably minimize the surface energy as they counterbalance the molecular dipole by presenting oppositely charged ions on the rearranged step edge.

  6. A generalized rule of average for glow peak temperature of ternary alkali halide systems

    Scientific Electronic Library Online (English)

    G., Moroyoqui-Estrella; R., Pérez-Salas; R., Rodriguez-Mijangos.

    2011-04-01

    Full Text Available Se estudia la dependencia de la temperatura en la curva de brillo con la composición de los aniones en mezclas cristalinas impurificadas con Europio: KCl0.50KBr0.25RbX0.25:Eu2+ (X = Cl, Br). Cada material muestra una curva de brillo termoluminiscente consistente en dos picos de brillo principales co [...] n temperatura entre la del KCl:Eu2+ y la del KBr:Eu2+. El pico más intenso está relacionado con la destrucción del centro F, como ocurre en el caso de cristales de KCl:Eu2+ y su temperatura característica depende fuertemente de la composición del halogeno. El comportamiento confirma que la temperatura de la recombinación de los centros F-H en este tipo de materiales depende en gran medida de la proporción de los aniones. De estos resultados se propone una regla generalizada para obtener la temperatura, promediando la temperatura característica en función de la composición. Abstract in english The anion composition dependence of the characteristic glow peak temperature of europium doped KCl0.50KBr0.25RbX0.25:Eu2+ (X=Cl, Br) mixed crystals are studied. Each material shows a thermoluminescence glow curve consisting of two main glow peaks with a temperature is between KCl:Eu2+ and KBr:Eu2+. [...] The most intense is related to the F center destruction as occur in the case of KCl:Eu2+ crystals and its characteristic temperature depends strongly on the halogen composition. This behavior confirms that the temperature of the F-H centers recombination in this type of materials depends more on the proportion of anions. From these results, a generalized rule to obtain the temperature from averaging the characteristic temperature as function of the composition is discussed.

  7. Heteroepitaxial strain in alkali halide thin films: KCl on NaCl

    DEFF Research Database (Denmark)

    Baker, J.; Lindgård, Per-Anker

    1999-01-01

    We have pet-formed Monte Carlo simulations of the properties of a NaCl (001) surface covered by full or partial layers of KCl, for coverages up to 5 monolayers (ML). A wide variety of structures of the film is found. For integer ML coverages we find the continuous, so-called floating mode rumple structure, as was previously found in the KBr/NaCl system. However, for a coverage of similar to 2.1 ML, we find a discrete structure of periodicity 3:4 of small regularly spaced KCl pyramids. It has the same scattering characteristics as the structure observed by Henzler et al. [Phys. Rev. B 52, 17 060 (1995)], but it is two-dimensional modulated, rather than the rowlike stacking fault structure proposed by Henzler et al. Also, at a coverage of similar to 0.8 ML there is a stable 3:4 structure. Other structures are found at intermediate coverages, corresponding to regular arrays of dislocation lines with periodicity 9:10. A further growth from such structures would give rise to growth of a similar to 5 degrees miscutKCl crystal relative to the NaCl lattice. The reciprocal space patterns corresponding to the continuous and the discrete film deformations are also calculated.

  8. A coupled molecular dynamics and SCF-X?-SW technique of calculations of optical absorption spectra of localized electron in molten mixtures of alkali halides

    International Nuclear Information System (INIS)

    Coupled Molecular Dynamics and quantum-chemical SCF-X?-SW techniques are applied to calculate the optical absorption spectrum of solvated electron in molten alkali halides and their mixtures. First step of the calculations consists in the computer simulation of the system of alkali and halide ions plus a model anion which represents the solvated electron. The local ionic configurations around the model anion which are obtained by the simulation are then used as an input for the SCF-X?-SW quantum-chemical program and the electron transition energies for these configurations are calculated. It was found that the most probable trapping sites for an excess electron in molten KBr/Li Br systems are formed by the configurations of 3 cations. The calculations of the ensemble - averaged energy of the optical transitions of the trapped electrons in the KBr/LiBr systems correctly reproduce the experimental dependence of the maximum of optical absorption on the KBr/Li Br composition. (author). 14 refs, 4 figs

  9. Solution growth of single crystal methylammonium lead halide perovskite nanostructures for optoelectronic and photovoltaic applications.

    Science.gov (United States)

    Fu, Yongping; Meng, Fei; Rowley, Matthew B; Thompson, Blaise J; Shearer, Melinda J; Ma, Dewei; Hamers, Robert J; Wright, John C; Jin, Song

    2015-05-01

    Understanding crystal growth and improving material quality is important for improving semiconductors for electronic, optoelectronic, and photovoltaic applications. Amidst the surging interest in solar cells based on hybrid organic-inorganic lead halide perovskites and the exciting progress in device performance, improved understanding and better control of the crystal growth of these perovskites could further boost their optoelectronic and photovoltaic performance. Here, we report new insights on the crystal growth of the perovskite materials, especially crystalline nanostructures. Specifically, single crystal nanowires, nanorods, and nanoplates of methylammonium lead halide perovskites (CH3NH3PbI3 and CH3NH3PbBr3) are successfully grown via a dissolution-recrystallization pathway in a solution synthesis from lead iodide (or lead acetate) films coated on substrates. These single crystal nanostructures display strong room-temperature photoluminescence and long carrier lifetime. We also report that a solid-liquid interfacial conversion reaction can create a highly crystalline, nanostructured MAPbI3 film with micrometer grain size and high surface coverage that enables photovoltaic devices with a power conversion efficiency of 10.6%. These results suggest that single-crystal perovskite nanostructures provide improved photophysical properties that are important for fundamental studies and future applications in nanoscale optoelectronic and photonic devices. PMID:25871732

  10. Mollwo-Ivey relations for optical absorption bands of the atomic and F' centres in alkali halides

    International Nuclear Information System (INIS)

    Evidence indicates that two classes of the transient IR-absorption bands: (a) with maxima at 0.27-0.36 eV in NaCl, KCl, KBr, KI and RbCl and due to shallow electron traps or bound polarons according to Jacobs (Phys. Stat. Sol. B 129 (1985) 755) and Korovkin and Lebedkina (Fiz. Tverd. Tela (Russian) 35 (1993) 642), and (b) with maxima at 0.15-0.36 eV in NaI, NaBr, NaCl:I, KCl:I, RbCl:I and RbBr:I, due to on-centre STE localised at iodine-dimer according to Hirota et al. (J. Phys. Soc. Japan 63 (1994) 2774, Phys. Rev. B 52 (1995) 7779) and Edamatsu and Hirai (Mater. Sci. Forum 239-241 (1997) 525), are caused by the same defect. We propose that the defect is an atomic alkali impurity centre [M+]c0e-, i.e. an electron e- trapped by a smaller size substitutional alkali cation impurity [M+]c0. The Mollwo-Ivey plots for the transient IR-absorption bands of the zero-phonon line energy E0 for NaCl, KCl, KBr, RbCl and NaBr, KCl:I and/or the low-energy edge values E0 for NaI, RbCl:I and RbBr:I versus anion-cation distance, d, are obtained for the first time. These data suggest that two types of the [M+]c0e- centres are predominant: (i) [Na+]c0e- in KX and RbX host crystals with the relation E0?6.15/d2.74 and (ii) [Li+]c0e-]c0e- in NaX host crystals with E0?29.4/d4.72. The Mollwo-Ivey relation E0?18.36/d2.70 is fulfilled as well for the F' band in NaCl, KCl, KBr, KI, RbCl, RbI if we use the F' centre optical binding energy values for E0

  11. Advances in the growth of alkaline-Earth halide single crystals for scintillator detectors

    Science.gov (United States)

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, J. S.; Cherepy, N. J.; Beck, P. R.; Payne, S. A.; Burger, A.; Rowe, E.; Bhattacharya, P.

    2014-09-01

    Alkaline-earth scintillators such as strontium iodide and other alkaline-earth halides activated with divalent europium represent some of the most efficient and highest energy resolution scintillators for use as gamma-ray detectors in a wide range of applications. These applications include the areas of nuclear nonproliferation, homeland security, the detection of undeclared nuclear material, nuclear physics and materials science, medical diagnostics, space physics, high energy physics, and radiation monitoring systems for first responders, police, and fire/rescue personnel. Recent advances in the growth of large single crystals of these scintillator materials hold the promise of higher crystal yields and significantly lower detector production costs. In the present work, we describe new processing protocols that, when combined with our molten salt filtration methods, have led to advances in achieving a significant reduction of cracking effects during the growth of single crystals of SrI2:Eu2+. In particular, we have found that extended pumping on the molten crystalgrowth charge under vacuum for time periods extending up to 48 hours is generally beneficial in compensating for variations in the alkaline-earth halide purity and stoichiometry of the materials as initially supplied by commercial sources. These melt-pumping and processing techniques are now being applied to the purification of CaI2:Eu2+ and some mixed-anion europium-doped alkaline-earth halides prior to single-crystal growth by means of the vertical Bridgman technique. The results of initial studies of the effects of aliovalent doping of SrI2:Eu2+ on the scintillation characteristics of this material are also described.

  12. Locations of Halide Ions in Tetragonal Lysozyme Crystals

    Science.gov (United States)

    Lim, Kap; Adimurthy, Ganapathi; Nadarajah, Arunan; Forsythe, Elizabeth L.; Pusey, Marc L.

    1998-01-01

    Anions play an important role in the crystallization of lysozyme, and are known to bind to the crystalline protein. Previous studies employing X-ray crystallography had found one chloride ion binding site in the tetragonal crystal form of the protein and four nitrate ion binding sites in the monoclinic form. Studies using other approaches have reported more chloride ion binding sites, but their locations were not known. Knowing the precise location of these anions is also useful in determining the correct electrostatic fields surrounding the protein. In the first part of this study the anion positions in the tetragonal form were determined from the difference Fourier map obtained from the lysozyme crystals grown in bromide and chloride solutions under identical conditions. The anion locations were then obtained from standard crystallographic methods and five possible anion binding sites were found in this manner. The sole chloride ion binding site found in previous studies was confirmed. The remaining four sites were new ones for tetragonal lysozyme crystals. However, three of these new sites and the previously found one corresponded to the four unique binding sites found for nitrate ions in monoclinic crystals. This suggests that most of the anion binding sites in lysozyme remain unchanged, even when different anions and different crystal forms of lysozyme are employed. It is unlikely that there are many more anions in the tetragonal lysozyme crystal structure. Assuming osmotic equilibrium it can be shown that there are at most three more anions in the crystal channels. Some of the new anion binding sites found in this study were, as expected, in pockets containing basic residues. However, some of them were near neutral, but polar, residues. Thus, the study also showed the importance of uncharged, but polar groups, on the protein surface in determining its electrostatic field. This was important for the second part of this study where the electrostatic field surrounding the protein was accurately determined. This was achieved by solving the linearized version of the Poisson-Boltzmann equation for the protein in solution. The solution was computed employing the commercial code Delphi which uses a finite difference technique. This has recently become available as a module in the general protein visualization code Insight II. Partial charges were assigned to the polar groups of lysozyme for the calculations done here. The calculations showed the complexity of the electrostatic field surrounding the protein. Although most of the region near the protein surface had a positive field strength, the active site cleft was negatively charged and this was projected a considerable distance. This might explain the occurrence of "head-to-side" interactions in the formation of lysozyme aggregates in solution. Pockets of high positive field strength were also found in the vicinity of the anion locations obtained from the crystallographic part of this study, confirming the validity of these calculations. This study clearly shows not only the importance of determining the counterion locations in protein crystals and the electrostatic fields surrounding the protein, but also the advantage of performing them together.

  13. Photofragmentation of metal halides

    International Nuclear Information System (INIS)

    The author deals with photodissociation of molecules of alkali halides. It is shown that the total absorption cross section consists of two contributions arising from transitions to excited states of total electronic angular momentum ?=0+ and ?=1. From the inversion of the absorption continua potential energy curves of the excited states can be constructed in the Franck-Condon region. It is found that for all alkali halides the 0+ state is higher in energy than the ?=1 state. Extensive studies are reported on three thallium halides, TlI, TlBr and TlCl at various wavelengths covering the near ultraviolet region. (Auth.)

  14. Synthesis, crystal structures and thermal properties of new copper(I) halide coordination polymers

    Science.gov (United States)

    Näther, Christian; Greve, Jan; Jeß, Inke

    2002-05-01

    The new copper(I) halide coordination polymers {3}/{?}poly[CuCl( ?-2,5-dimethylpyrazine-N,N')] ( I), {2}/{?}poly[CuBr( ?-2,5-dimethylpyrazine-N,N')] ( II) and {2}/{?}poly[Cu 2X 2( ?-2,5-dimethylpyrazine-N,N')] (X=Br ( III), I ( IV)) were synthesized by the reaction of the copper(I) halides with 2,5-dimethylpyrazine in acetonitrile. In the crystal structure of I, helical CuCl chains are found, which are connected by the 2,5-dimethylpyrazine ligands forming a three-dimensional structure. In the structure of compound II Cu 2Br 2 dimers and in compounds III and IV CuX double chains (X=Br, I) occur which are connected via the ligands to sheets. The thermal properties of all compounds were investigated using simultaneously differential thermoanalysis (DTA), thermogravimetry (TG) and mass spectroscopy (MS) as well as temperature resolved X-ray powder diffraction. On heating compound I transforms into the new compound Cu 2Cl 2(2,5-dimethylpyrazine) ( V), which forms CuCl on further heating. For compound II in the first step a transformation into the 2:1 compound III is observed, which loses again a part of the ligands forming the new copper(I) halide rich compound Cu 4Br 4(2,5-dimethylpyrazine) ( VI). A halide rich compound Cu 4I 4(2,5-dimethylpyrazine) ( VII) which is presumably isotypic to VI is also observed during the thermal decomposition of IV. On further heating both 4:1 compounds transform directly to CuBr and CuI.

  15. New halides of neodymium and their crystal structures

    International Nuclear Information System (INIS)

    The crystal structures of the peritectic phases NdClsub(2.27) (t-phase) and NdClsub(2.37) (rh-phase) were determined. The structure of the rh-phase was solved, from the t-phase only the elementary cell could be determined because no single crystals of sufficient quality were obtained. Jutting out feature of the rh-phase which has to be formulated as Nd14Cl32O is a polyeder cluster of 6 quadratic antiprisms the inner cubo octahedric cavity of which is occupied by an oxygen atom. The linkage of these polyeder cluster ensues only under each other along the triple axis of the rhomboedric system over 3 upper and 3 lower common borders each. Therewith for the first time a superlattice of the fluorite-type was found in which this unit exclusively occurs. The type of linkage of polyeder clusters causes the occurrence of an exceptional polyeder around the twovalent Nd ions which can be looked at as a zwitter polyeder of icosahedron and cube and therefore coordinates tenfold the twovalent neodymium. The strict order of chemically and crystallografically clearly differentiated cations is expressed by a hexagonal-rhomboedric superstructure of the fluorite-aristotyp with a doubled c-axis. The phase diagram of the system Nd-NdBr3 was determined and a structure proposition was worked out for the first Vernier phase in there with n=4 of the series Lnsub(n)Xsub(2n+1). (SPI)

  16. Potential Advantage of Multiple Alkali Metal Doped KNbO3 Single Crystals

    OpenAIRE

    Hideo Kimura; Hongyang Zhao; Rumi Tanahashi; Lei Guo; Tingting Jia; Qiwen Yao; Zhenxiang Cheng

    2014-01-01

    Potassium niobate crystal KNbO3 (KN) is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being published. In order to exceed the KN crystal, it is important to study KN phase forming and doping effects on the K site. This article summarizes the authors’ study towards a multiple alkali metal doped KN crystal and related single crystals ...

  17. Nucleation and Crystal Growth of Organic-Inorganic Lead Halide Perovskites under Different Relative Humidity.

    Science.gov (United States)

    Gao, Hao; Bao, Chunxiong; Li, Faming; Yu, Tao; Yang, Jie; Zhu, Weidong; Zhou, Xiaoxin; Fu, Gao; Zou, Zhigang

    2015-05-01

    Organic-inorganic lead halide perovskite compounds are very promising materials for high-efficiency perovskite solar cells. But how to fabricate high-quality perovksite films under controlled humidity conditions is still an important issue due to their sensitivity to moisture. In this study, we investigated the influence of ambient humidity on crystallization and surface morphology of one-step spin-coated perovskite films, as well as the performance of solar cells based on these perovskite films. On the basis of experimental analyses and thin film growth theory, we conclude that the influence of ambient humidity on nucleation at spin-coating stage is quite different from that on crystal growth at annealing stage. At the spin-coating stage, high nucleation density induced by high supersaturation prefers to appear under anhydrous circumstances, resulting in layer growth and high coverage of perovskite films. But at the annealing stage, the modest supersaturation benefits formation of perovskite films with good crystallinity. The films spin-coated under low relative humidity (RH) followed by annealing under high RH show an increase of crystallinity and improved performance of devices. Therefore, a mechanism of fast nucleation followed by modest crystal growth (high supersaturation at spin-coating stage and modest supersaturation at annealing stage) is suggested in the formation of high-quality perovskite films. PMID:25871284

  18. Correlated studies of electric properties of ionic molecules: alkali and alkaline-earth hydrides, halides and chalcogenides

    Science.gov (United States)

    Fowler, P. W.; Sadlej, A. J.

    Electric polarizabilities, dipole and quadrupole moments of the molecules LiH, LiF, LiCl, NaH, NaF, NaCl, BeO, BeS, MgO, MgS, BeH, BeF, BeCl, MgH, MgF, MgCl, LiO, LiS, NaO and NaS are computed in a uniform basis at the correlated level of theory. The results are rationalized in terms of the properties of ion pairs, and the stability of the isolated anions: the hydrides, oxides and sulphides show large and positive correlation corrections to the polarizability in CASSCF, and erratic convergence of the MBPT series. The open-shell alkaline-earth hydrides and halides in the series all exhibit negative polarizability anisotropy.

  19. Neutron inelastic scattering investigation of phonons in alkali-halides and a neutron small-angle scattering study of voids in creep-deformed steel

    International Nuclear Information System (INIS)

    Studies on lattice dynamics in alkali-halides have been performed on RbBr and NaCl using inelastic scattering of thermal neutrons. Anharmonic properties of RbBr have been examined by measuring phonon peaks at the three temperatures 80, 290 and 370 K. In NaCl a three dimensional phonon dispersion map has been obtained. 72 phonon frequencies in off-symmetry directions have been determined. In creep-deformed alloy 800 the void radius distribution was obtained using neutron small-angle scattering. Six samples with different creep-times were studied. As these samples also contain carbides and ?'-precipitates the measured intensity is in principle due to scattering from three kinds of particles. Transmission electron microscopy measurements show that the scattering by the carbides is negligible, however. The relative radius distribution of ?'-particles, calculated for each sample individually, has an average radius of approximately 25 A. Because of experimental difficulties the void radius distribution could be determined only for samples with 5 and 10% creep. The voids appear to have a broad distribution around 300 A and the volume fraction of voids shows an increase of 7% between these two samples. (Auth.)

  20. Band-structure calculations of noble-gas and alkali halide solids using accurate Kohn-Sham potentials with self-interaction correction

    International Nuclear Information System (INIS)

    The optimized-effective-potential (OEP) method and a method developed recently by Krieger, Li, and Iafrate (KLI) are applied to the band-structure calculations of noble-gas and alkali halide solids employing the self-interaction-corrected (SIC) local-spin-density (LSD) approximation for the exchange-correlation energy functional. The resulting band gaps from both calculations are found to be in fair agreement with the experimental values. The discrepancies are typically within a few percent with results that are nearly the same as those of previously published orbital-dependent multipotential SIC calculations, whereas the LSD results underestimate the band gaps by as much as 40%. As in the LSD---and it is believed to be the case even for the exact Kohn-Sham potential---both the OEP and KLI predict valence-band widths which are narrower than those of experiment. In all cases, the KLI method yields essentially the same results as the OEP

  1. Crystallization of methyl ammonium lead halide perovskites: implications for photovoltaic applications.

    Science.gov (United States)

    Tidhar, Yaron; Edri, Eran; Weissman, Haim; Zohar, Dorin; Hodes, Gary; Cahen, David; Rybtchinski, Boris; Kirmayer, Saar

    2014-09-24

    Hybrid organic/lead halide perovskites are promising materials for solar cell fabrication, resulting in efficiencies up to 18%. The most commonly studied perovskites are CH3NH3PbI3 and CH3NH3PbI3-xClx where x is small. Importantly, in the latter system, the presence of chloride ion source in the starting solutions used for the perovskite deposition results in a strong increase in the overall charge diffusion length. In this work we investigate the crystallization parameters relevant to fabrication of perovskite materials based on CH3NH3PbI3 and CH3NH3PbBr3. We find that the addition of PbCl2 to the solutions used in the perovskite synthesis has a remarkable effect on the end product, because PbCl2 nanocrystals are present during the fabrication process, acting as heterogeneous nucleation sites for the formation of perovskite crystals in solution. We base this conclusion on SEM studies, synthesis of perovskite single crystals, and on cryo-TEM imaging of the frozen mother liquid. Our studies also included the effect of different substrates and substrate temperatures on the perovskite nucleation efficiency. In view of our findings, we optimized the procedures for solar cells based on lead bromide perovskite, resulting in 5.4% efficiency and Voc of 1.24 V, improving the performance in this class of devices. Insights gained from understanding the hybrid perovskite crystallization process can aid in rational design of the polycrystalline absorber films, leading to their enhanced performance. PMID:25171634

  2. Surface and zeta-potentials of silver halide single crystals: pH-dependence in comparison to particle systems.

    Science.gov (United States)

    Selmani, Atiða; Lützenkirchen, Johannes; Kallay, Nikola; Preo?anin, Tajana

    2014-06-18

    We have carried out surface and zeta-potential measurements on AgCl and AgBr single crystals. As for particle systems we find that, surprisingly and previously unnoted, the zeta-potential exhibits pH-dependence, while the surface potential does not. A possible interpretation of these observations is the involvement of water ions in the interfacial equilibria and in particular, stronger affinity of the hydroxide ion compared to the proton. The pH-dependence of the zeta-potential can be suppressed at sufficiently high silver concentrations, which agrees with previous measurements in particle systems where no pH-dependence was found at high halide ion concentrations. The results suggest a subtle interplay between the surface potential determining the halide and silver ion concentrations, and the water ions. Whenever the charge due to the halide and silver ions is sufficiently high, the influence of the proton/hydroxide ion on the zeta-potential vanishes. This might be related to the water structuring at the relevant interfaces which should be strongly affected by the surface potential. Another interesting observation is accentuation of the assumed water ion effect on the zeta-potential at the flat single crystal surfaces compared to the corresponding silver halide colloids. Previous generic MD simulations have indeed predicted that hydroxide ion adsorption is accentuated on flat/rigid surfaces. A thermodynamic model for AgI single crystals was developed to describe the combined effects of iodide, silver and water ions, based on two independently previously published models for AgI (that only consider constituent and background electrolyte ions) and inert surfaces (that only consider water and background electrolyte ions). The combined model correctly predicts all the experimentally observed trends. PMID:24863080

  3. Surface and zeta-potentials of silver halide single crystals: pH-dependence in comparison to particle systems

    International Nuclear Information System (INIS)

    We have carried out surface and zeta-potential measurements on AgCl and AgBr single crystals. As for particle systems we find that, surprisingly and previously unnoted, the zeta-potential exhibits pH-dependence, while the surface potential does not. A possible interpretation of these observations is the involvement of water ions in the interfacial equilibria and in particular, stronger affinity of the hydroxide ion compared to the proton. The pH-dependence of the zeta-potential can be suppressed at sufficiently high silver concentrations, which agrees with previous measurements in particle systems where no pH-dependence was found at high halide ion concentrations. The results suggest a subtle interplay between the surface potential determining the halide and silver ion concentrations, and the water ions. Whenever the charge due to the halide and silver ions is sufficiently high, the influence of the proton/hydroxide ion on the zeta-potential vanishes. This might be related to the water structuring at the relevant interfaces which should be strongly affected by the surface potential. Another interesting observation is accentuation of the assumed water ion effect on the zeta-potential at the flat single crystal surfaces compared to the corresponding silver halide colloids. Previous generic MD simulations have indeed predicted that hydroxide ion adsorption is accentuated on flat/rigid surfaces. A thermodynamic model for AgI single crystals was developed to describe the combined effects of iodide, silver and water ions, based on two independently previously published models for AgI (that only consider constituent and background electrolyte ions) and inert surfaces (that only consider water and background electrolyte ions). The combined model correctly predicts all the experimentally observed trends. (paper)

  4. Characterization of an alkali- and halide-resistant laccase expressed in E. coli: CotA from Bacillus clausii.

    Science.gov (United States)

    Brander, Søren; Mikkelsen, Jørn D; Kepp, Kasper P

    2014-01-01

    The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazine, tannic acid, and bilirubin at variable pH. Whereas ABTS, promazine, and phenyl hydrazine activities vs. pH were similar, the activity of B. clausii cotA was shifted upwards by ~0.5-2 pH units for the simple phenolic substrates DMP, SGZ, and caffeic acid. This shift is not due to substrate affinity (K(M)) but to pH dependence of catalytic turnover: The k(cat) of B. clausii cotA was 1 s?¹ at pH 6 and 5 s?¹ at pH 8 in contrast to 6 s?¹ at pH 6 and 2 s?¹ at pH 8 for of B. subtilis cotA. Overall, k(cat)/K(M) was 10-fold higher for B. subtilis cotA at pH(opt). While both proteins were heat activated, activation increased with pH and was larger in cotA from B. clausii. NaCl inhibited activity at acidic pH, but not up to 500-700 mM NaCl in alkaline pH, a further advantage of the alkali regime in laccase applications. The B. clausii cotA had ~20 minutes half-life at 80°C, less than the ~50 minutes at 80°C for cotA from B. subtilis. While cotA from B. subtilis had optimal stability at pH~8, the cotA from B. clausii displayed higher combined salt- and alkali-resistance. This resistance is possibly caused by two substitutions (S427Q and V110E) that could repel anions to reduce anion-copper interactions at the expense of catalytic proficiency, a trade-off of potential relevance to laccase optimization. PMID:24915287

  5. Alkali metals

    International Nuclear Information System (INIS)

    The discussion is presented under the following section headings: introduction; effect of contaminants; reactions of alkali metals with oxygen and nitrogen (sections on Li, Na, K, Rb, Cs); reactions of alkali metals with hydrogen; sample storage; sampling (sections on liquid metals in dynamic and static syystems and solid metals; methods for determination of oxygen (amalgamation, alkyl halide, fluorination, methanol solution and Karl Fischer titration, liquid ammonia for oxygen in lithium, distillation, plugging meter, electrochemical oxygen meter, freezing-point depression, resistivity, activation analysis); methods for determination of hydrogen (diffusion gasometric procedure, vacuum fusion and similar methods, amalgamation, isotope dilution, and miscellaneous); and,determination of nitrogen. (105 references.) (U.S.)

  6. Computation of methodology-independent single-ion solvation properties from molecular simulations. IV. Optimized Lennard-Jones interaction parameter sets for the alkali and halide ions in water

    Science.gov (United States)

    Reif, Maria M.; Hünenberger, Philippe H.

    2011-04-01

    The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [M. A. Kastenholz and P. H. Hünenberger, J. Chem. Phys. 124, 224501 (2006), 10.1529/biophysj.106.083667; M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144103 (2010)], the application of appropriate correction terms permits to obtain methodology-independent results. The corrected values are then exclusively characteristic of the underlying molecular model including in particular the ion-solvent van der Waals interaction parameters, determining the effective ion size and the magnitude of its dispersion interactions. In the present study, the comparison of calculated (corrected) hydration free energies with experimental data (along with the consideration of ionic polarizabilities) is used to calibrate new sets of ion-solvent van der Waals (Lennard-Jones) interaction parameters for the alkali (Li+, Na+, K+, Rb+, Cs+) and halide (F-, Cl-, Br-, I-) ions along with either the SPC or the SPC/E water models. The experimental dataset is defined by conventional single-ion hydration free energies [Tissandier et al., J. Phys. Chem. A 102, 7787 (1998), 10.1021/jp982638r; Fawcett, J. Phys. Chem. B 103, 11181] along with three plausible choices for the (experimentally elusive) value of the absolute (intrinsic) hydration free energy of the proton, namely, ? G_hyd^{ominus }[H+] = -1100, -1075 or -1050 kJ mol-1, resulting in three sets L, M, and H for the SPC water model and three sets LE, ME, and HE for the SPC/E water model (alternative sets can easily be interpolated to intermediate ? G_hyd^{ominus }[H+] values). The residual sensitivity of the calculated (corrected) hydration free energies on the volume-pressure boundary conditions and on the effective ionic radius entering into the calculation of the correction terms is also evaluated and found to be very limited. Ultimately, it is expected that comparison with other experimental ionic properties (e.g., derivative single-ion solvation properties, as well as data concerning ionic crystals, melts, solutions at finite concentrations, or nonaqueous solutions) will permit to validate one specific set and thus, the associated ? G_hyd^{ominus }[H+] value (atomistic consistency assumption). Preliminary results (first-peak positions in the ion-water radial distribution functions, partial molar volumes of ionic salts in water, and structural properties of ionic crystals) support a value of ? G_hyd^{ominus }[H+] close to -1100 kJ.mol-1.

  7. Synthesis and single-crystal structure determination of the zinc nitride halides Zn2NX (X=Cl, Br, I)

    International Nuclear Information System (INIS)

    A series of zinc nitride halides, Zn2NX (X=Cl, Br, I), has been synthesized from solid–liquid reactions of zinc nitride with the respective zinc halides under vacuum, and their crystal structures were determined using single-crystal and powder X-ray diffraction. While Zn2NCl and Zn2NBr crystallize in the acentric orthorhombic space group Pna21, Zn2NI adopts the centrosymmetric space group Pnma; Zn2NCl and Zn2NBr can be considered to belong to the anti-?-NaFeO2 type, and Zn2NI is closely related. Each N3? is tetrahedrally coordinated by zinc atoms, and the X? anions are located in the vacancies of the framework formed by corner-sharing [NZn4] tetrahedra. According to TGA/DTA analyses, the Zn2NX compounds exhibit good thermal stability. The electronic structure has been analyzed by employing density-functional theory and the HSE06 hybrid functional. - Graphical abstract: Zn2NCl, Zn2NBr, and Zn2NI have been synthesized, and their crystal structures (Cl and Br phases: Pna21; I phase: Pnma) have been determined from XRD; the direct band gap of Zn2NCl is theoretically (HSE06 hybrid functional) predicted as 3.7 eV. - Highlights: • Zn2NCl, Zn2NBr, and Zn2NI have been synthesized from solid–liquid reactions. • The crystal structures of Zn2NCl, Zn2NBr, and Zn2NI have been determined from single-crystal X-ray diffraction. • Zn2NCl and Zn2NBr crystallize in the acentric space group Pna21 whereas Zn2NI adopts the centrosymmetric space group Pnma. • Zn2NCl and Zn2NBr are stable up to 750 °C whereas Zn2NI decays at 600 °C already. • The direct band gap of Zn2NCl is theoretically predicted as 3.7 eV using the HSE06 hybrid functional

  8. Creation of molecular defects in alkali iodide crystals by irradiation with fast heavy ions

    International Nuclear Information System (INIS)

    We show for the first time that irradiation at room temperature of alkali iodide crystals by fast heavy ions (40Ar14+ ions of 5.53 MeV/A at a fluence of 1013 ions/cm2) leads to the formation of V-type defects. By means of UV visible optical absorption and resonant Raman scattering measurements, we have identified I3-, I5- and (I2)n in Kl and only I3- and I5- in RbI irradiated under similar conditions. These preliminary results are consistent with previous investigations obtained in iodide crystals after exposure to X or ? rays at room temperature. (orig.)

  9. Electrolytic systems and methods for making metal halides and refining metals

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Justin M.; Cecala, David M.

    2015-05-26

    Disclosed are electrochemical cells and methods for producing a halide of a non-alkali metal and for electrorefining the halide. The systems typically involve an electrochemical cell having a cathode structure configured for dissolving a hydrogen halide that forms the halide into a molten salt of the halogen and an alkali metal. Typically a direct current voltage is applied across the cathode and an anode that is fabricated with the non-alkali metal such that the halide of the non-alkali metal is formed adjacent the anode. Electrorefining cells and methods involve applying a direct current voltage across the anode where the halide of the non-alkali metal is formed and the cathode where the non-alkali metal is electro-deposited. In a representative embodiment the halogen is chlorine, the alkali metal is lithium and the non-alkali metal is uranium.

  10. Preparation of cerium halide solvate complexes

    Science.gov (United States)

    Vasudevan, Kalyan V; Smith, Nickolaus A; Gordon, John C; McKigney, Edward A; Muenchaussen, Ross E

    2013-08-06

    Crystals of a solvated cerium(III) halide solvate complex resulted from a process of forming a paste of a cerium(III) halide in an ionic liquid, adding a solvent to the paste, removing any undissolved solid, and then cooling the liquid phase. Diffusing a solvent vapor into the liquid phase also resulted in crystals of a solvated cerium(III) halide complex.

  11. Multipole interaction effects on cohesive and anharmonic properties of alkali cyanide crystals

    International Nuclear Information System (INIS)

    The cohesive and anharmonic properties of alkali cyanide crystals are investigated using a three-body potential consisting of long-range Coulomb and three-body interactions, and the short-range van der Waals attraction and overlap repulsion operative up to the second neighbour ions. The results on cohesive energy, compressibility, molecular force constant, and infrared absorption frequencies are in better agreement with their experimental data than those obtained earlier from a logarithmic potential. An overall systematic trend, followed by the values of third-and fourth-order elastic constants and the pressure and temperature derivatives of the second-order elastic constants, is discussed. (author)

  12. Radiation processes in crystal solid solutions

    CERN Document Server

    Gladyshev, Gennadi

    2012-01-01

    This is a monograph explaining processes occurring in two classes of crystal solids (metal alloys and doped alkali halide) under irradiation by various types of radiation (alpha, beta, gamma, X-radiations, ions). This e-book is a useful reference for advanced readers interested in the physics of radiation and solid state physics.

  13. Stability diagrams for complexes in molten mixtures of halide salts

    International Nuclear Information System (INIS)

    The stability of local fourfold coordination for divalent and trivalent metal ions in liquid mixtures of polyvalent metal halides and alkali halides is classified by means of structural coordinates obtained from properties of the elements. In parallel with earlier classifications of compound crystal structures and molecular shapes, the elemental properties are taken from first-principles calculations of valence electron orbitals in atoms, in the form of (i) the nodal radii of Andreoni, Baldereschi and Guizzetti or (ii) the pseudo-potential radii of Zunger and Cohen. As a third alternative we also consider a classification based on Pettifor's phenomenological chemical scale of the elements. The alternative structural classification schemes that are developed from these elemental properties are very successful in distinguishing molten mixtures in which the available experimental evidence indicates stability of ''complexes'', i.e. long-lived fourfold coordination of polyvalent metal ions. (author). 55 refs, 3 figs

  14. Structure of luminescence spectra of UO2+2 impurity ions in halide salt solid solutions

    International Nuclear Information System (INIS)

    Luminescence spectra of impurity polyatomic ions of UO22+ in water and aqueous solutions of alkali-halide salts are studied in the 1.62-77 K temperature range. The emission spectra of these solutions at 77 K are characterized by a pronounced vibrational structure specified by the interaction of an electron transition with an impurity ion intramolecular vibration #betta#1. At 1.62-4.2 K individual vibrational bands are splitted to phononless lines and structural phonon wings (FW). The PW structure is defined by an excitation of crystalline vibrations of a solution solid matrix. For the H2O-UO22+ solution the PW maximum frequences are shown to be comparable with the main critical points of the vibration spectrum of an orientation-disorded ice crystal. In case of aqueous solutions of alkali-halide salts with UO22+ impurity ions the PW luminescence spectra are compared with the density functions of undistorted vibrations of alkali-halide salt crystals and ice

  15. Middle infrared luminescence of Tb3+ in silver halide crystals and fibers

    International Nuclear Information System (INIS)

    The optical absorption and the luminescence emission were investigated in AgClxBr1-x crystals (03+ ions and in fibers extruded from these crystals. Strong luminescence emission in the middle infrared (MIR) in the spectral range 4.2-5.6 ?m was observed for the first time in such crystals and fibers. Various optical parameters were calculated for the Tb3+-doped crystals, using the Judd-Ofelt approximation. The measured and the calculated results have indicated that these doped crystals could be used for the development of solid-state lasers or fiber lasers operating in the middle infrared

  16. Cluster models of doped ionic crystal scintillators. Quantum calculations

    International Nuclear Information System (INIS)

    The authors have performed quantum electronic ab initio calculations of clusters of alkali halides, both pure and doped. In order to estimate the pure crystal energy gap and the dopant excitation, they have considered a central cation and four shells of ions surrounding it. They have studied KCl, NaI, NaCl and KI, both pure and with a Tl+ ion replacing the central alkali cation. Encouraging results are presented for absorption and emission

  17. Spectral-luminescence properties of the halide-cesium crystals with the impurity of the tetrahedral molecular anions

    International Nuclear Information System (INIS)

    Absorption, excitation (PLE) and emission (PL) spectra as well as infrared absorption spectra and Raman spectra of the tetrahedral molecular anions (MA) CrO42-. MoO42-, ReO4- in the halide-cesium crystals (CsHal) CsCl, CsBr, CsI have been studied in the temperature range of 4.2 K to 300 K. Impure MA in crystals CsHal is characterized by complicated structure of the infrared absorption and Raman spectra. The structure of the spectra is due to the splitting of the degenerate vibration ?2(E), ?3(F2), ?4(F2) of the impure MA as a result of the decreasing of their local symmetry from Td to C3v, C2v or Cs because of the formation of the complexes of the several types. Such molecular complexes are formed with anion or cation vacancies or with metal cations Me+(Na+, K+, Rb+, Tl+) and Me2+(Mg2+, Ca2+, Sr2+, Ba2+) which have been doped to the crystals for the charge compensation of the impure MA. Observed structure of the vibrational spectra has been identified by the calculation of the MA vibration, decreased the local symmetry in the formed complexes and by the computer optimisation of the theoretical and observed data of the vibrational frequency of MA in crystals. Luminescence of the crystals CsHal wi. Luminescence of the crystals CsHal with the impure MA CrO42-, MoO4-, ReO4- can be observed only at low temperature. Impure complexes with different structure and symmetry which are formed by the same tetrahedral MA are characterized by different value of the electron-phonon interaction that may be seen in the structure of the absorption, PL and PLE spectra or in the character of the temperature dependence of the emission quantum yield. The parameters of spin orbit and spin lattice interactions in the impure complexes has been received. (author)

  18. Some uranium halide complexes

    International Nuclear Information System (INIS)

    Uranium halide complex salts [MeEtim]X (where[MeEtim] 1-methyl-3-ethyl-imidazolium; X-Cl, Br, I) have been used for synthesis of room temperature ionic liquids AlX3 [Me Etim]X. The crystal structure of [MeEtim]I revealed significant H bonding between cation and anion. This interaction, detected here for the first time, is important for the structure of these ionic liquids which are efficient solvents for studying electrochemical and spectroscopic properties of novel uranium halide complex salts. The cyclic voltammogram of [UO2X4]2- salts showed irreversible and reversible reduction processes. X-ray structural analysis of this salt showed tetragonal symmetry and no evidence of H bonds between anions and cations. The X-ray structure of a pseudo-halide compound [U(NCS)]4- showed significant cation-anion bonding. (U.K.)

  19. Mechanochemical reactions of alkali metal-halides—The systems AX/BX/(H 2O) with A, B = Na, K, Rb, Cs and X = Cl, Br, I

    Science.gov (United States)

    Severin, Ingrid; Seifert, Hans-J.; Yariv, Shmuel

    1990-10-01

    Solid solutions (K, Rb)X with X = Cl, Br, I are obtained by grinding mixtures of KX and RbX in a ball mill. The reaction can be accelerated by adding a small amount of water. When grinding CsCl and NaCl or CsBr and NaBr together with a stoichiometric amount of water in the ratio 1:2:2 double salts Cs(Na · H 2O) 2X 3 (X = Cl, Br) are obtained. Above 40°C or 70°C, respectively they are partially dehydrated, yielding solid solutions Cs 1-x(Na · H 2O) xX. For both phases the enthalpies of formation from the binary halides were measured by solution calorimetry. They are negative.

  20. Oxidation of hydrogen halides to elemental halogens

    Science.gov (United States)

    Rohrmann, Charles A. (Kennewick, WA); Fullam, Harold T. (Richland, WA)

    1985-01-01

    A process for oxidizing hydrogen halides having substantially no sulfur impurities by means of a catalytically active molten salt is disclosed. A mixture of the subject hydrogen halide and an oxygen bearing gas is contacted with a molten salt containing an oxidizing catalyst and alkali metal normal sulfates and pyrosulfates to produce an effluent gas stream rich in the elemental halogen and substantially free of sulfur oxide gases.

  1. Lattice relaxation of luminescence centres of the X-line emission of ns2 impurity ions in alkali halides; anomalous geometry of the impurity centre in the excited nsnp state

    International Nuclear Information System (INIS)

    Clear evidence was found that in the active centre from which the X-line emission of ns2 impurities in alkali halides originates the excited impurity ion is statically displaced over an anomalously large distance in a direction which depends on the lattice structure. For fcc this is one of the (111) directions and the centre has trigonal symmetry, and for the bcc lattice it is one of the (001) directions and the symmetry is tetragonal. The displacement only occurs in the excited state and probably is a result of covalency effects. The study was performed using a readily available code for lattice relaxation around impurity ions. For the fcc lattice we have studied the relaxation of Ga+, In+ and Tl+ in KCl and of In+ in KBr. For the bcc case we considered In+ in high-pressure KCl. A comparison with well known experimental data for the three impurity ions and the good agreement found for both the T- and X-line emission wavelengths supports our theoretical results. (author)

  2. Role of the crystallization substrate on the photoluminescence properties of organo-lead mixed halides perovskites

    Directory of Open Access Journals (Sweden)

    Michele De Bastiani

    2014-08-01

    Full Text Available We have fabricated CH3NH3PbI3?xClx perovskite thin films crystallized in situ on substrates of different natures (e.g., porosity, wettability and investigated their photoluminescence properties. We observe that the crystallization time and thin film structure are strongly influenced by the chemical nature and porosity of the substrate. Moreover, we find that the mesoporous scaffold can tune the emissive properties of the semiconducting compound both in terms of spectral region and dynamics. In particular, perovskite crystallites grown in the nanometre size porous scaffold present a shorter-living and blue-shifted emission with respect to the perovskite crystals which are free to grow without any constraints.

  3. The radiation defect accumulation in scintillative crystals of caesium halides under intense electron beam irradiation

    CERN Document Server

    Galiy, P V

    1999-01-01

    The characteristics of defect accumulation and radiolysis at CsI crystals under mean energies of electron irradiation at wide dose rates and ranges of doses have been investigated by such methods: thermostimulated exoelectron emission (TSEE), Auger electron spectroscopy (AES) and optical absorption spectroscopy (OAS). The limit dose rates and absorbed doses of electron irradiation that lead to defects accumulation at room temperature in crystals volume and also surface stoichiometry violation have been evaluated. The doses of electron irradiation that lead to CsI radiolysis, with caesium coagulation in metallic phase have been determined. Some quasi periodic connection of such process with irradiation dose was observed.

  4. Structure of polyvalent metal halide melts

    International Nuclear Information System (INIS)

    A short review is given of recent progress in determining and understanding the structure of molten halide salts involving polyvalent metal ions. It covers the following three main topics: (i) melting mechanisms and types of liquid structure for pure polyvalent-metal chlorides; (ii) geometry and stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides; and (iii) structure breaking and electron localization on addition of metal to the melt. (author). 28 refs, 3 figs, 1 tab

  5. A facile solvothermal growth of single crystal mixed halide perovskite CH3NH3Pb(Br1-xClx)3.

    Science.gov (United States)

    Zhang, Taiyang; Yang, Mengjin; Benson, Eric E; Li, Zijian; van de Lagemaat, Jao; Luther, Joseph M; Yan, Yanfa; Zhu, Kai; Zhao, Yixin

    2015-04-23

    We demonstrate a facile synthetic approach for preparing mixed halide perovskite (CH3NH3)Pb(Br1-xClx)3 single crystals by the solvothermal growth of stoichiometric PbBr2 and [(1 - y)CH3NH3Br + yCH3NH3Cl] DMF precursor solutions. The band gap of (CH3NH3)Pb(Br1-xClx)3 single crystals increased and the unit cell dimensions decreased with an increase in Cl content x, consistent with previous theoretical predictions. Interestingly, the Cl/Br ratio in the (CH3NH3)Pb(Br1-xClx)3 single crystals is larger than that of the precursor solution, suggesting an unusual crystal growth mechanism. PMID:25853846

  6. Metal halide reduction with molten sodium/potassium alloy

    International Nuclear Information System (INIS)

    A method of obtaining a desired metal, selected from the group consisting of titanium, aluminium, iron, manganese, hafnium, zirconium, tantalum, vanadium, uranium and tungsten, which comprises reacting a halide of the desired metal with an alkali metal reducing agent at temperature at which the reducing agent is molten, in order to produce the desired metal and halide of the metal reducing agent

  7. Intensity distributions of reflected surface channeling protons scattered on surfaces of electron-bombarded alkali halide crystals

    International Nuclear Information System (INIS)

    We have examined the surface-channeling of 550 keV protons on electron-bombarded KBr(0 0 1) surfaces at grazing incidence. On the surface, electron-stimulated desorption (ESD) resulting from the irradiation of 5 keV electrons changes the surface morphology. In order to investigate the change of the surface morphology, the luminous intensity distributions observed on a fluorescent screen (scattering patterns) of the reflected protons under the surface-channeling conditions are measured. Normalized specular intensity of the protons oscillates, and the results of computer simulations show that the period of the intensity oscillation agrees with the period of layer-by-layer desorption. The measured period of the oscillation is comparable to the simulated one, i.e., the period of the desorption, however, the measured amplitude of the oscillation is weak. This shows that the layer-by-layer desorption of the experimental surface is observed but is not as remarkable as that of the perfect surface introduced in the simulation

  8. Alkali Metal Ion Templated Transition Metal Formate Framework Materials : Synthesis, Crystal Structures, Ion Migration, and Magnetism

    DEFF Research Database (Denmark)

    Eikeland, Espen; Lock, Nina

    2014-01-01

    Four transition metal formate coordination polymers with anionic frameworks, namely, Na[Mn(HCOO)(3)], K[Mn(HCOO)(3)], Na-2[Cu-3(HCOO)(8)], and K-2[Cu-5(HCOO)(12)], were synthesized using a mild solution chemistry approach. Multitemperature single-crystal (100-300 K) and powder Xray diffraction studies of the compounds reveal structures of large diversity ranging from cubic chiral Na-Mn formate to triclinic Na-Cu formate. The structural variety is caused by the nature of the transition metals, the alkali metal ion templation, and the versatility of the formate group, which offers metal metal coordination through three different O-C-O bridging modes (syn-syn, syn-anti, anti-anti) in addition to metal metal bridging via a single oxygen atom. The two manganese(II) compounds contain mononuclear, octahedrally coordinated moieties, but the three-dimensional connectivity between the manganese octahedra is very different in the two structures. The two copper frameworks, in contrast, consist of binuclear and mononuclear moieties (Na-Cu formate) and trinuclear and mononuclear moieties (K-Cu formate), respectively. Procrystal electron density analysis of the compounds indicates one-dimensional K+-ion conductivity in K-Mn and K-Cu, and the nature of the proposed potassium ion migration is compared with results from similar analysis on known Na+ and K+ ion conductors. K-Mn and Na-Mn were tested as cathode materials, but this resulted in poor reversibility due to low conductivity or structural collapse. The magnetic properties of the compounds were studied by vibrating sample magnetometric measurements, and their thermal stabilities were determined by thermogravimetric analysis and differential thermal analysis. Despite structural differences, the metal formates that contain the same transition metal have similar magnetic properties and thermal decomposition pathways, that is, the nature of the transition metal controls the compound properties.

  9. Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from Bacillus clausii

    DEFF Research Database (Denmark)

    Brander, SØren; Mikkelsen, JØrn Dalgaard

    2014-01-01

    The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazine, tannic acid, and bilirubin at variable pH. Whereas ABTS, promazine, and phenyl hydrazine activities vs. pH were similar, the activity of B. clausii cotA was shifted upwards by ,0.5–2 pH units for the simple phenolic substrates DMP, SGZ, and caffeic acid. This shift is not due to substrate affinity (KM) but to pH dependence of catalytic turnover: The kcat of B. clausii cotA was 1 s21 at pH 6 and 5 s21 at pH 8 in contrast to 6 s21 at pH 6 and 2 s21 at pH 8 for of B. subtilis cotA. Overall, kcat/KM was 10-fold higher forB. subtilis cotA at pHopt. While both proteins were heat activated, activation increased with pH and was larger in cotA from B. clausii. NaCl inhibited activity at acidic pH, but not up to 500–700 mM NaCl in alkaline pH, a further advantage of the alkali regime in laccase applications. The B. clausii cotA had ,20 minutes half-life at 80uC, less than the ,50 minutes at 80uC for cotA from B. subtilis. While cotA from B. subtilis had optimal stability at pH,8, the cotA from B. clausii displayed higher combined salt- and alkali-resistance. This resistance is possibly caused by two substitutions (S427Q and V110E) that could repel anions to reduce anion-copper interactions at the expense of catalytic proficiency, a trade-off of potential relevance to laccase optimization.

  10. Origin of radiative transitions from metastable minima of the excited state of Sn2+vsub(c)- centres in alkali halides

    International Nuclear Information System (INIS)

    The dependence of electronic wave functions on the coordinates of not totally symmetric vibrations and the hyperfine interaction are considered theoretically as the possible reasons of the radiative decay of the metastable minima of the sp excited state of Sn2+vsub(c) centres in KCl crystals. It is shown that the dependence of electronic wave functions on the coordinates of not totally symmetric vibrations, which leads to the dynamical lowering of symmetry and removal of forbiddenness for radiative transition from metastable minima (deviation from the Condon approximation), is the main reason of the radiative decay. Taking into account also the mixing of the functions of the radiative and metastable minima by the hyperfine interaction, a 1 to 10% shortening of decay time tau is expected at the transition from natural tin (containing 16% of Sn119) to pure isotope Sn119. A comparison of the decay times is performed which are measured at 2 and 4.2 K for Asub(T) luminescence of Sn2+vsub(c) centres in KCl crystals doped with tin having different isotopic abundance. The values of tau in KCl:SnCl2 and KCl:119SnCl2 crystals are shown to differ to about 4%, whereas in KCl crystals doped with the isotope 119Sn the decay time is always shorter than that in KCl with natural tin. This result, being the first experimental observation of the influence of the hyperfine interaction on luminescence the hyperfine interaction on luminescence decay kinetics of impurity centres in the crystals, is in good agreement with the theory. (author)

  11. Stability diagrams for fourfold coordination of polyvalent metal ions in molten mixtures of halide salts

    International Nuclear Information System (INIS)

    The stability of local fourfold coordination for divalent and trivalent metal ions in liquid mixtures of polyvalent metal halides and alkali halides is classified by means of structural coordinates obtained from properties of the elements. In parallel with earlier classifications of compound crystal structures and molecular shapes, the elemental properties are taken from first-principles calculations of valence electron orbitals in atoms, in the form of (i) the nodal radii of Andreoni, Baldereschi and Guizzetti or (ii) the pseudopotential radii or Zunger and Cohen. As a third alternative a classification based on Pettifor's phenomenological chemical scale of the elements is also considered. The alternative structural classification schemes that are developed from these elemental properties are generally successfully in distinguishing molten mixtures in which the available experimental evidence indicates long-lived fourfold coordination of polyvalent metal ions. In addition, Pettifor's chemical scale scheme is useful in sorting out finer details of local coordination in the liquid state. 3 figs., 71 refs

  12. Intercalation of C60 fullerene crystals with alkali and alkaline-earth metals through self-propagating high-temperature synthesis

    Science.gov (United States)

    Sidorov, N. S.; Palnichenko, A. V.

    2010-01-01

    A method for rapidly intercalating C60 fullerene crystals has been implemented using self-propagating high-temperature synthesis. The method has been used to intercalate C60 fullerene crystals with alkali (K, Rb) and alkaline-earth (Ca, Ba) metals. The superconducting transition temperatures of the prepared compounds have been measured. The C60 fullerene crystals intercalated with calcium have been investigated using X-ray diffraction.

  13. Crystal Dynamics from Neutron Spectrometry

    International Nuclear Information System (INIS)

    This paper reviews investigations carried out at Chalk River on the lattice dynamics of various crystals including lead, sodium, alkali halides, semi-conductors, and other more complex compounds. Analysis of the low temperature results (-?100oK) gives considerable insight into the nature of the interatomic forces. In sodium, a simple metal, the interatomic forces are very nearly derivable from a potential. Lead, a more complicated metal, has extremely long range forces accompanied by strong electronic effects. At higher temperatures anharmonic effects are very pronounced in both metals, especially in lead. The alkali halide results can be interpreted on a ''shell'' model, with polarizable ions. Even at low temperature neutron groups corresponding to the longitudinal optical modes. (author)

  14. Differential calorimeter and temperature controller for stored energy measurements in irradiated alkali halides; Calorimetro diferencial y controlador de temperatura para medidas de energia almacenada en haluros alcalinos irradiados

    Energy Technology Data Exchange (ETDEWEB)

    Delgado Martinez, L.

    1977-07-01

    The design and performance of a simple temperature-controlled differential calorimeter are presented. This system allows to measure radiation-induced stored energy in insulators, above room temperature with a differential thermal analysis method. With platelets of KC1 single crystals, the base lines obtained for T{sub 2} T{sub 1} (with T{sub 2}: irradiated sample temperature and T{sub 1}: reference sample temperature) show a smooth drift less of 0,2 degree centigree in the interval from 25 to 400 degree centigree. The discrepancy between two consecutive base lines is less than {+-} 0,02 degree centigree which implies a calorimeter sensitivity of about {+-}0,004 cal/g. This sensitivity allows to measure stored energy release in samples with a color center concentration low enough to be directly measured with a spectrophotometer so that a search for correlations among the features of the stored energy spectrum and the color center annealing can be made. (Author) 13 refs.

  15. Crystal growth and evaluation of scintillation properties of Eu and alkali-metal co-doped LiSrAlF6 single crystals for thermal neutron detector

    International Nuclear Information System (INIS)

    In recent work, Na co-doping have found to improve the light output of Eu doped LiCaAlF6 (Eu:LiCAF) for thermal neutron scintillator. We grew Eu 2% and alkali metal 1% co-doped LiSAF crystals by Micro-Pulling down method to understand the effect of alkali metal co-doping on scintillation properties and mechanism compared with LiCAF. In photo- and ?-ray induced radio-luminescence spectra of the all grown crystals, the emissions from d-f transition of Eu2+ were observed. Without relation to excitation source, decay times of co-doped LiSAF were longer than Eu only doped one. The light yield of Na, K and Cs co-doped LiSAF under 252Cf neutron excitation were improved. Especially, K co-doped Eu:LiSAF reached 33200 ph/n, which outperformed Eu only doped one by approximately 20% (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Thermally stimulated luminescence and lattice defects in crystals of alkali metal borate LiB3O5 (LBO)

    International Nuclear Information System (INIS)

    The recombination processes and lattice defects in crystals of alkali metal borate LiB3O5 (LBO) were studied by the means of the thermally stimulated luminescence (TL) and electron spin resonance (ESR) techniques. The glow curves, the spectra of the LBO recombination luminescence, and the angular variations of ESR-spectra of the O- center in three different planes were measured in the temperature range from 80 to 400 K. The luminescence bands were assigned to the electron (Em=4.0 eV) and hole (Em=4.2 eV) recombination processes. The model of the trapped hole center O- was proposed. The processes responsible for the formation of localised electronic excitations in LBO were discussed and compared with those taking place in other wide-gap oxides

  17. Electrodepositions on Tantalum in Alkali Halide Melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede

    2013-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO3 melts carbonate ions seems to be reduced to carbon in a single 4 electron step. By electrolyses at a constant potential of – 1.4 V vs. Pt in a NaCl-KCl-NaF-Na2CO3 melt at 800 oC coherent carbon containing surface layers could be obtained on tantalum substrates, when a CO2 atmosphere was applied

  18. Electrodepositions on Tantalum in alkali halide melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede

    2012-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K 2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO 3 melts carbonate ions seems to be reduced to carbon in a single 4 electron step. By electrolyses at a constant potential of - 1.4 V vs. Pt in a NaCl-KCl-NaF-Na2CO3 melt at 800 °C coherent carbon containing surface layers could be obtained on tantalum substrates, when a CO2 atmosphere was applied. Copyright © 2012 by The Electrochemical Society.

  19. Strongly localized anharmonic modes in perfect and imperfect crystals

    OpenAIRE

    Hizhnyakov, V.; Nevedrov, D.; Sigmund, E.

    1999-01-01

    Localized modes of large amplitudes in nonlinear lattices are considered. The applied method allows the reduction of nonlinear problem to a linear inverse problem of phonons scattering on a local potential. The method is efficient in the case of strongly localized modes. Analytical description of such modes in monatomic chain is given. Results of numerical calculations of anharmonic local vibrations of light ions in pure and impure alkali halide crystal are presented. It is ...

  20. Growth of KCl1–xBrx Mixed Crystals with Different Composition Percent and Study of KBr Concentration Effect on Optical Characteristics of Mixed Crystals

    Directory of Open Access Journals (Sweden)

    Sajad Shahmaleki

    2012-06-01

    Full Text Available In the present research, mixed crystals KCl1–xBrx (x = 0.1, 0.3, 0.5, 0.7 & 0.9 were grown by Czochralski method. Then some analysis such as chemical etching, XRD, and absorbing spectrum were established on the irradiated crystals by ?-ray. The results of this research show that configuration of defects in mixed crystals in contrast with pure crystals is different. Somehow that type and percentage of cumulative composition cause to changing in lattice parameter and lattice defect density in alkali halide crystals and finally change optical properties of crystal.

  1. Effect of an electric field on the crystallization in a high-alkali containing glass system

    International Nuclear Information System (INIS)

    In this study, we hypothesize that the temperature range for crystallization (dT) has two meanings: the presence of a critical energy for crystallization (ECR) and the presence of a crystallization energy (ECK) at each temperature, and we investigated this hypothesis. In order to investigate the validity of the hypothesis, we need a differential thermal analysis (DTA), and we measured the change in the crystallization starting temperature (TX) caused by an electric field in the glass ceramic 50SiO2-40Na2O-10CaO (wt%). From the DTA results and the Kissinger equation, the calculated ECR for crystallization was 55 ±4 kcal/mol. The TX decreased at temperatures under 450 degrees in the presence of an electric field while it was 495 ± 8 degrees in the absence of an electric field. The electric field decreased the activation energy needed for ion movement, so the glass met the condition for crystallization and stoichiometry at an even lower temperature; hence the TX was decreased. From this, we concluded that the ECK was proportional to the activation energy needed for ion movement. From this conclusion, we verified the hypothesis.

  2. Crystal fractionation in the petrogenesis of an alkali monzodiorite syenite series: the Oshurkovo plutonic sheeted complex, Transbaikalia, Russia

    Science.gov (United States)

    Litvinovsky, Boris A.; Jahn, Bor-ming; Zanvilevich, Ada N.; Shadaev, Michael G.

    2002-10-01

    The Oshurkovo Complex is a plutonic sheeted complex which represents numerous successive magmatic injections into an expanding system of subparallel and subvertical fractures. It comprises a wide range of rock types including alkali monzodiorite, monzonite, plagioclase-bearing and alkali-feldspar syenites, in the proportion of about 70% mafic rocks to 30% syenite. We suggest that the variation within the complex originated mainly by fractional crystallization of a tephrite magma. The mafic rocks are considered as plutonic equivalents of lamprophyres. They exhibit a high abundance of ternary feldspar and apatite, the latter may attain 7-8 vol.% in monzodiorite. Ternary feldspar is also abundant in the syenites. The entire rock series is characterized by high Ba and Sr concentrations in the bulk rock samples (3000-7000 ppm) and in feldspars (up to 1 wt.%). The mafic magma had amphibole at the liquidus at 1010-1030 °C based on amphibole geothermometer. Temperatures as low as this were due to high H 2O and P 2O 5 contents in the melt (up to 4-6 and ˜2 wt.%, respectively). Crystallization of the syenitic magmas began at about 850 °C (based on ternary feldspar thermometry). The series was formed at an oxygen fugacity from the NNO to HM buffer, or even higher. The evolution of the alkali monzodiorite-syenite series by fractional crystallization of a tephritic magma is established on the basis of geological, mineralogical, geochemical and Sm-Nd and Rb-Sr isotope data. The geochemical modeling suggests that fractionation of amphibole with subordinate apatite from the tephrite magma leaves about 73 wt.% of the residual monzonite melt. Further extraction of amphibole and plagioclase with minor apatite and Fe-Ti oxides could bring to formation of a syenite residuum. Rb-Sr isotopic analyses of biotite, apatite and whole-rock samples constrain the minimum age of basic intrusions at ca. 130 Ma and that of cross-cutting granite pegmatites at ca. 120 Ma. Hence the entire evolution took place in an interval of ?10 My. Initial 87Sr/ 86Sr ratios for the mafic rocks range from 0.70511 to 0.70514, and for syenites from 0.70525 to 0.70542. Initial ?Nd (130 Ma) values for mafic rocks vary from -1.9 to -2.4, and for syenites from -2.9 to -3.5. In a ?Nd( T) vs. ( 87Sr/ 86Sr) i diagram, all rock types of the complex fall in the enriched portion of the Mantle Array, suggesting their derivation from a metasomatized mantle source. However, the small but distinguishable difference in Sr and Nd isotopic compositions between mafic rocks and syenites probably resulted from mild (10-20%) crustal contamination during differentiation. Large negative Nb anomalies are interpreted as a characteristic feature of the source region produced by Precambrian fluid metasomatism above a subduction zone rather than by crustal contamination.

  3. Liquid Crystals and Glasses in Binary Systems from Sodium and Alkali-Earth Metal Butyrates

    Science.gov (United States)

    Mirnaya, T. A.; Bereznitski, Y. V.; Volkov, S. V.

    1996-07-01

    The temperature and composition ranges of liquid crystal and glass formation have been established for the binary mixtures of mesogenic sodium butyrate with non-mesogenic magnesium, calcium and strontium butyrates by means of differential thermal analysis and hot stage polarization microscopy. The formation of a vitreous optically anisotropic mesophase has been found for binaries of sodium butyrate with calcium and strontium butyrates.

  4. He atom-surface scattering: Surface dynamics of insulators, overlayers and crystal growth

    International Nuclear Information System (INIS)

    Investigations in this laboratory have focused on the surface structure and dynamics of ionic insulators and on epitaxial growth onto alkali halide crystals. In the later the homoepitaxial growth of NaCl/NaCl(001) and the heteroepitaxial growth of KBr/NaCl(001), NaCl/KBr(001) and KBr/RbCl(001) have been studied by monitoring the specular He scattering as a function of the coverage and by measuring the angular and energy distributions of the scattered He atoms. These data provide information on the surface structure, defect densities, island sizes and surface strain during the layer-by-layer growth. The temperature dependence of these measurements also provides information on the mobilities of the admolecules. He atom scattering is unique among surface probes because the low-energy, inert atoms are sensitive only to the electronic structure of the topmost surface layer and are equally applicable to all crystalline materials. It is proposed for the next year to exploit further the variety of combinations possible with the alkali halides in order to carry out a definitive study of epitaxial growth in the ionic insulators. The work completed so far, including measurements of the Bragg diffraction and surface dispersion at various stages of growth, appears to be exceptionally rich in detail, which is particularly promising for theoretical modeling. In addition, because epitaxial growth conditions over a wide range of lattice mismatches is possible with these materials, size effects in growth processes can be explored in great depth. Further, as some of the alkali halides have the CsCl structure instead of the NaCl structure, we can investigate the effects of the heteroepitaxy with materials having different lattice preferences. Finally, by using co-deposition of different alkali halides, one can investigate the formation and stability of alloys and even alkali halide superlattices

  5. Vapor phase crystallization in Apollo 14 breccia.

    Science.gov (United States)

    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.

  6. Structural criteria for the design of anion receptors: The interaction of halides with electron-deficient arenes

    Energy Technology Data Exchange (ETDEWEB)

    Berryman, Mr. Orion B. [University of Oregon; Bryantsev, Vyacheslav S. [California Institute of Technology, Pasadena; Stay, Mr. David P. [University of Oregon; Johnson, Prof. Darren W. [University of Oregon; Hay, Benjamin [ORNL

    2007-01-01

    This paper refines the nature of the interactions between electron-deficient arenes and halide anions. Conclusions are based on (i) new crystal structures containing alkali halide salts with 1,2,4,5-tetracyanobenzene (TCB) and 18-crown-6, (ii) evaluation of crystal structures found in the Cambridge Structural Database, and (iii) MP2/aug-cc-pVDZ calculations of F-, Cl-, and Br- complexes with TCB, 1,3,5-tricyanobenzene, triazine, and hexafluorobenzene. When the halide lies above the plane of the pi system, the results establish that three distinctly different types of complexes are possible: strongly covalent sigma complexes, weakly covalent donor-pi-acceptor complexes, and noncovalent anion-pi complexes. When aryl C-H groups are present, a fourth type of interaction leads to C-H center dot center dot center dot X- hydrogen bonding. Characterization of the different geometries encountered with the four possible binding motifs provides criteria needed to design host architectures containing electron-deficient arenes.

  7. Structural Criteria for the Design of Anion Receptors: The Interaction of Halides with Electron-Deficient Arenes

    Energy Technology Data Exchange (ETDEWEB)

    Berryman, Orion B.; Bryantsev, Vyacheslav; Stay, David P.; Johnson, Darren W.; Hay, Benjamin P.

    2007-01-10

    This paper refines the nature of the interactions between electron-deficient arenes and halide anions. Conclusions are based on (1) new crystal structures containing alkali halide salts with 1,2,4,5-tetracyanobenzene (TCB) and 18-crown-6, (2) evaluation of crystal structures found in the Cambridge Structural Database, and (3) MP2/aug-cc-pVDZ calculations of F?, Cl?, and Br? complexes with TCB, 1,3,5-tricyanobenzene, triazine, and hexafluorobenzene. When the halide lies above the plane of the ? system, the results establish that three distinctly different types of complexes are possible: strongly covalent ? complexes, weakly covalent donor ?-acceptor complexes, and electrostatic anion-? complexes. When aryl C?H groups are present, a fourth type of interaction leads to C?H???X? hydrogen bonding. Characterization of the different geometries encountered with the four possible binding motifs provides criteria needed to design host architectures containing electron-deficient arenes. This research was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences laboratory, a national scientific user facility sponsored by the U.S. Department of Energy?s Office of Biological and Environmental Research located at the Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  8. Growth and characterization of YBa2Cu3O7 - ? single crystals

    International Nuclear Information System (INIS)

    Measurement of the anisotropy of the physical properties of YBCO requires good quality single crystals. Small crystals have been widely grown from a CuO-BaCuO2 flux, but are usually in the form of thin platelets making many measurements difficult. More recently, an alternative additive flux route based on a mixed alkali halide eutectic has produced crystals with a three-dimensional morphology. In this paper the authors compare the morphology, crystallinity and physical properties of crystals grown by the two routes

  9. Local fields in ionic crystals

    International Nuclear Information System (INIS)

    Local fields arising from the electronic distortion in perfect ionic crystals are described in terms of multipolar excitations. Field factors for the alkali halides and chalcogenide ions are found to differ significantly from the Lorentz value of 4?/3, the correction size following an exponential dependence on the difference in ionic radii. Local fields are only slightly modified by these corrections however, and together with the Clausius-Mossotti relation may be regarded as accurate to within 2% if the Lorentz value is adopted. (author)

  10. Radiation-induced processes and defects in alkali and alkaline-earth borate crystals

    International Nuclear Information System (INIS)

    The paper presents the results of a study of the radiation-induced processes and defects in nonlinear optical crystals Li2B4O7 (LTB), LiB3O5 (LBO), CsLiB6O10, KB5O8·4H2O, ?-BaB2O4. It was revealed that a pulsed electron beam irradiation at 290 K forms the radiation-induced pairs of the 'vacancy--interstitial atom' defects in the cation sublattice of these crystals. This gives rise to a creation of metastable electronic (interstitial atom) and hole (small-radius polaron near the cation vacancy) centers in high concentrations. Optical hole-transitions from the local level of the trapped hole centers to the valence band states are responsible for the transient optical absorptions (TOA) of borates in the visible and UV spectral ranges. A sublattice of the weakly bound mobile lithium cations in LTB and LBO favors a spatial separation of the radiation-induced pair defects 'hole polaron near Li-vacancy--mobile interstitial Li0 atom'. Their decay rated by the electron-hole nonradiative tunnel recombination determines a peculiar feature of the TOA decay kinetics in LTB and LBO

  11. Crystallization and preliminary X-ray study of a family 10 alkali-thermostable xylanase from alkalophilic Bacillus sp. strain NG-27

    International Nuclear Information System (INIS)

    A family 10 alkali-thermostable xylanase from Bacillus sp. NG-27 has been crystallized. A diffraction data set has been collected to 2.2 Å resolution. Xylanases (EC 3.2.1.8) catalyze the hydrolysis of ?-1,4-glycosidic linkages within xylan, a major hemicellulose component in the biosphere. The extracellular endoxylanase (XylnA) from the alkalophilic Bacillus sp. strain NG-27 belongs to family 10 of the glycoside hydrolases. It is active at 343 K and pH 8.4. Moreover, it has attractive features from the point of view of utilization in the paper pulp, animal feed and baking industries since it is an alkali-thermostable protein. In this study, XylnA was purified from the native host source and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 174.5, b = 54.7, c = 131.5 Å, ? = 131.2°, and diffract to better than 2.2 Å resolution

  12. ????????????????? ???????? Effect of the Ratio of SiO2 and Al2O3 on the Viscosity and Crystallization of Non-Alkali Aluminoborosilicate Glasses at High Temperature

    Directory of Open Access Journals (Sweden)

    ???

    2013-05-01

    Full Text Available ????????????????????????????????????????????????????????????????????????????????????????????????Effect of the ratio of SiO2 and Al2O3 on the viscosity and crystallization of non-alkali aluminoborosilicate glasses at high temperature was investigated. The results showed that the viscosity, the fiber-drawing temperature and the activation energy for vicious flow were increased, the liquidus temperature was decreased and the difference between the fiber-drawing temperature & the liquidus temperature was increased with the ratio of SiO2 and Al2O3 increased.

  13. Halide substitution in magnesium borohydride

    OpenAIRE

    Baricco, Marcello; DAMIN, Alessandro Ali; Zavorotynska, Olena; Corno, Marta

    2012-01-01

    The synthesis of halide-substituted Mg(BH4)2 by ball-milling, and characterization with respect to thermodynamics and crystal structure, has been addressed. The ball-milled mixture of Mg(BH4)2 and MgX2 (X = Cl, Br) has been investigated by in situ/ex situ synchrotron powder X-ray di?raction (SR-PXD), di?erential scanning calorimetry (DSC), and infrared and Raman spectroscopy. High resolution SR-PXD patterns reveal that the unit cell volume of ?-Mg(BH4)2 in milled and annealed mixtu...

  14. Effect of alkali metal Oxides on viscosity and crystallization of the MgO–Al2O3–SiO2 glasses

    International Nuclear Information System (INIS)

    MgO–Al2O3–SiO2 glasses were prepared by using TiO2 and ZrO2 as nucleation agents, and 2% (wt%, the same as below) content of alkali metal oxide was added. The viscosity of MAS glass melt was investigated by the rotating crucible viscometer, and the melting temperature and activation energy for viscous flow of the melt were derived by the Arrhenius equation. After melting and casting, the glass samples were crystallized in the temperature range from 880 to 1145 °C. The prepared glass-ceramics presented transparent to opaque with the increasing of crystallization temperature, which had been investigated by X-ray diffraction and field emission–environment scanning electron microscope. The results showed that the melting temperature of glass containing 2% Na2O was about 1585 °C. The MgAl2O4, ZrTiO4 and the sapphirine crystalline phases precipitated from matrix glass successively as the crystallization temperature raising. When 1% Na2O was replaced by Li2O, the melting temperature of the glasses decreased to 1508 °C, meanwhile, the main crystal phase changed from MgAl2O4 to high-/low—quartz solid solution, therefore, the crystallization behavior was uncontrollable and the transparent glass ceramic cannot be obtained. As 1% K2O substituted for Na2O, the melting temperature decreased to 1573 °C. The adding of K2O could broaden the crystallization temperature range of preparing transparent glass-ceramics. After crystallized at the range from 900 °C to 1000 °C, the fine spinel (MgAl2O4) crystals which had average size about 25 nm precipitated from matrix glasses, and the specimens kept transparent

  15. Atomistic simulation of ion solvation in water explains surface preference of halides

    OpenAIRE

    Caleman, Carl; Hub, Jochen S.; van Maaren, Paul J.; van der Spoel, David

    2011-01-01

    Water is a demanding partner. It strongly attracts ions, yet some halide anions—chloride, bromide, and iodide—are expelled to the air/water interface. This has important implications for chemistry in the atmosphere, including the ozone cycle. We present a quantitative analysis of the energetics of ion solvation based on molecular simulations of all stable alkali and halide ions in water droplets. The potentials of mean force for Cl-, Br-, and I- have shallow minima near the surface. We de...

  16. Crystal preferred orientations of minerals from mantle xenoliths in alkali basaltic rocks form the Catalan Volcanic Zone (NE Spain)

    Science.gov (United States)

    Fernández-Roig, Mercè; Galán, Gumer; Mariani, Elisabetta

    2015-04-01

    Mantle xenoliths in alkali basaltic rocks from the Catalan Volcanic Zone, associated with the Neogene-Quaternary rift system in NE Spain, are formed of anhydrous spinel lherzolites and harzburgites with minor olivine websterites. Both peridotites are considered residues of variable degrees of partial melting, later affected by metasomatism, especially the harzburgites. These and the websterites display protogranular microstructures, whereas lherzolites show continuous variation between protogranular, porphyroclastic and equigranular forms. Thermometric data of new xenoliths indicate that protogranular harzburgites, lherzolites and websterites were equilibrated at higher temperatures than porphyroclastic and equigranular lherzolites. Mineral chemistry also indicates lower equilibrium pressure for porphyroclastic and equigranular lherzolites than for the protogranular ones. Crystal preferred orientations (CPOs) of olivine and pyroxenes from these new xenoliths were determined with the EBSD-SEM technique to identify the deformation stages affecting the lithospheric mantle in this zone and to assess the relationships between the deformation fabrics, processes and microstructures. Olivine CPOs in protogranular harzburgites, lherzolites and a pyroxenite display [010]-fiber patterns characterized by a strong point concentration of the [010] axis normal to the foliation and girdle distribution of [100] and [001] axes within the foliation plane. Olivine CPO symmetry in porphyroclastic and equigranular lherzolites varies continuously from [010]-fiber to orthorhombic and [100]-fiber types. The orthorhombic patterns are characterized by scattered maxima of the three axes, which are normal between them. The rare [100]-fiber patterns display strong point concentration of [100] axis, with normal girdle distribution of the other two axes, which are aligned with each other. The patterns of pyroxene CPOs are more dispersed than those of olivine, especially for clinopyroxene, but there is good correlation between the [100] olivine axis and the [001] pyroxene axis in most protogranular peridotites. However, the [001] axes of the three silicates are parallel in equigranular and some porphyroclastic lherzolites. CPOs and misorientation axes indicate deformation by dislocation creep accommodated mainly by the [100](010) slip system for olivine and the [001](100), [001](010) for orthopyroxene. Also, subsidiary slip systems for olivine are [100]{0kl}, [001](100), [100](001) in porphyroclastic and equigranular lherzolites. The fabric strength of the three main silicates are consistent, all of them decreasing with grain size reduction. These results indicate that the lithospheric mantle in this area was affected by several deformation stages that took place at decreasing temperature and pressure. An earlier stage is preserved in protogranular peridotites and a pyroxenite, with olivine [010]-fiber patterns and consistent deformation of pyroxenes. It could be related to axial shortening, transpression and/or subsequent recovery and annealing. Later deformation stages would be recorded by most porphyroclastic and equigranular lherzolites characterized by orthorhombic and [100]-fiber patterns for olivine, and transitions between them and with the [010]-fiber one. These samples would come most likely from an active shear zone at shallower upper mantle depth, where deformation at higher strain rates would explain the olivine [100]-fiber symmetry. Transient deformation patterns for olivine, grain size reduction along with weakening of the fabric strength could be due to dynamic recrystallization through grain boundary migration and subgrain rotation mechanisms.

  17. Theoretical and experimental study of the Stark effect in the ground state of alkali atoms in helium crystals

    OpenAIRE

    Ulzega, Simone; Weis, Antoine

    2007-01-01

    This thesis work describes a detailed study of the Stark interaction in the ground state of cesium atoms trapped in a solid helium matrix. The motivation for the investigation of electric field effects on alkali species implanted in solid helium is related to the original main goal of our experimental activities, i.e., the measurement of a permanent atomic electric dipole moment (EDM). The existence of an atomic EDM simultaneously violates the discrete symmetries of time reversal (T) and pari...

  18. Photochemistry of Phenyl Halides

    OpenAIRE

    Karlsson, Daniel

    2008-01-01

    We have studied fundamental aspects of photo-induced dissociation kinetics and dynamics in several phenyl halides. By combining femtosecond pump-probe measurements with ab initio calculations we are able to account for several observations. In mixed phenyl halides, the dissociation kinetics is found to be dependent on the nature, the number, and the position of the substituents, and also on the excitation wavelength. A surprisingly large reduction in the dissociation time constant, compared t...

  19. Tertiary phosphine derivatives of the f-block metals. Preparation of X4M(Me2PCH2C2Me2)2, where X is halide, methyl, or phenoxo and M is thorium or uranium. Crystal structure of tetra(phenoxo)bis[bis(1,2-dimethylphosphino)ethane]-uranium(IV)

    International Nuclear Information System (INIS)

    Through a number of tertiary phosphine complexes or uranium halides have been claimed, most of the claims have been shown to be false. In this communication we describe the synthesis of some authentic bis(1,2-dimethylphosphino)ethane (dmpe) complexes of uranium(IV) and thorium(IV) halides of the type X4M(dmpe)2 and their conversion to the tetramethyl and tetraphenoxo derivatives. The crystal structure of the phenoxo derivative, (PhO)4U(dmpe)2, is described

  20. Crown ether uranyl halide complexes

    International Nuclear Information System (INIS)

    Uranium oxide is recovered from an aqueous solution of uranyl halides by extracting uranyl halide from the aqueous solution with an organic liquid, forming a crown ether uranyl halide complex in the organic liquid, and then contacting the uranyl halide crown ether complex with water, carboxylate ion, and light under suitable conditions. Also disclosed are certain novel crown ether uranyl halide complexes and their preparation. Also disclosed is the use of 18-crown-6 to selectively recover uranyl halide from a solution thereof containing other metal salts

  1. Thermally stimulated luminescence and lattice defects in crystals of alkali metal borate LiB{sub 3}O{sub 5} (LBO)

    Energy Technology Data Exchange (ETDEWEB)

    Ogorodnikov, I.N. E-mail: ogo@dpt.ustu.ru; Isaenko, L.I.; Kruzhalov, A.V.; Porotnikov, A.V

    2001-10-01

    The recombination processes and lattice defects in crystals of alkali metal borate LiB{sub 3}O{sub 5} (LBO) were studied by the means of the thermally stimulated luminescence (TL) and electron spin resonance (ESR) techniques. The glow curves, the spectra of the LBO recombination luminescence, and the angular variations of ESR-spectra of the O{sup -} center in three different planes were measured in the temperature range from 80 to 400 K. The luminescence bands were assigned to the electron (E{sub m}=4.0 eV) and hole (E{sub m}=4.2 eV) recombination processes. The model of the trapped hole center O{sup -} was proposed. The processes responsible for the formation of localised electronic excitations in LBO were discussed and compared with those taking place in other wide-gap oxides.

  2. Low-alkali metal content in ?-vanadium mixed bronzes: The crystal structures of ?-K x (V,Mo)6O15 (x=0.23 and 0.32) by single-crystal X-ray diffraction

    International Nuclear Information System (INIS)

    The vanadium-molybdenum mixed oxide bronzes of composition K0.23(V5.35Mo0.65)O15 and K0.32(V5.48Mo0.52)O15 have a monoclinic structure with s.g. C2/m, Z=2, and unit-cell dimensions a=15.436(2), b=3.6527(5), c=10.150(1) A, ?=108.604(3)o and a=15.452(2), b=3.6502(5), c=10.142(1) A, ?=109.168(3)o, respectively, as determined by single-crystal X-ray diffraction. These compounds show the ?-Na x V6O15 tunnel structure, which is isostructural with bannermanite, natural sodium-potassium vanadate. Structure refinements from diffracted intensities collected in the 2-38o? range converged to final R=5.58% and 7.48% for the two crystals, respectively. The V atoms are distributed on three different crystallographic sites. Partial substitution of V with Mo occurs in only one of these positions. Oxygen atoms involved in vanadyl groups point toward the tunnels. The K ions in the tunnels are coordinated by seven oxygen atoms. The alkali metal content in these crystals is much lower than the solubility limit found for the analogous Na containing compound. - Graphical abstract: Perspective view of the crystal structure of K x V6- y Mo y O15 along [010]. This vanadium-molybdenum mixed bronze assumes the ?-Na x V6O15 (bannermanite-type) structure, (bannermanite-type) structure, in which Mo(VI) substitutes for V only in the V2 position. The alkali metal content in the studied crystals is much lower than the solubility limit found for the analogous Na containing compounds

  3. The ab-initio calculation of crystal structure and lattice dynamics of perfect and defective MeX (Me+ = Rb+, K+, Na+; X-= F-, Cl-)

    International Nuclear Information System (INIS)

    In this work, the interionic pair potentials X-- X-, Me+- X-(Me+ Rb+, K+, Na+; X- = F-, Cl-) within the framework of shell model were obtained using the self consistent field Rhoothaan-Hartree-Fock approximation allowing the correlation correction in second order Moller-Plesset form. Further, nonempirical pair potentials were used for the calculations of the structure and lattice dynamics of perfect and imperfect alkali halides crystals. Impact analysis of anion vacancies influence on crystal vibrational spectrum was carried out with the help of recursive technique calculations of symmetrized and localized density of vibrational states in the perfect and vacancies including crystal

  4. Crystal growth and evaluation of scintillation properties of Eu and alkali-metal co-doped LiSrAlF{sub 6} single crystals for thermal neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Wakahara, Shingo; Yokota, Yuui; Yamaji, Akihiro; Fujimoto, Yutaka; Sugiyama, Makoto; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Pejchal, Jan [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Institute of Physics AS CR, Cukrovarnicka 10, Prague 16253 (Czech Republic); Kawaguchi, Noriaki [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Fukuda, Kentaro [Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

    2012-12-15

    In recent work, Na co-doping have found to improve the light output of Eu doped LiCaAlF{sub 6} (Eu:LiCAF) for thermal neutron scintillator. We grew Eu 2% and alkali metal 1% co-doped LiSAF crystals by Micro-Pulling down method to understand the effect of alkali metal co-doping on scintillation properties and mechanism compared with LiCAF. In photo- and {alpha}-ray induced radio-luminescence spectra of the all grown crystals, the emissions from d-f transition of Eu{sup 2+} were observed. Without relation to excitation source, decay times of co-doped LiSAF were longer than Eu only doped one. The light yield of Na, K and Cs co-doped LiSAF under {sup 252}Cf neutron excitation were improved. Especially, K co-doped Eu:LiSAF reached 33200 ph/n, which outperformed Eu only doped one by approximately 20% (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Optical properties and radiation damages of cerium fluoride crystals doped with alkali-earth and rare-earth elements

    International Nuclear Information System (INIS)

    The most essential contribution in the investigation of CeF3 crystals having the goal to construct high precision electromagnetic calorimeters has been done by Crystal Clear Collaboration. Study of optical properties and radiation damages of Cerium Fluoride crystals doped with Ca, Ba, Sr, La, Nd, Zr and Hf in the wide range of concentrations has been performed with the goal to obtain high optical transparency of crystals at different cumulative doses under ?-irradiation. Time decay curves and relative light yields of scintillators as a function of doping level were measured using X-ray excitation of samples and single photon counting method

  6. Process for oxidation of hydrogen halides to elemental halogens

    Science.gov (United States)

    Lyke, Stephen E. (Middleton, WI)

    1992-01-01

    An improved process for generating an elemental halogen selected from chlorine, bromine or iodine, from a corresponding hydrogen halide by absorbing a molten salt mixture, which includes sulfur, alkali metals and oxygen with a sulfur to metal molar ratio between 0.9 and 1.1 and includes a dissolved oxygen compound capable of reacting with hydrogen halide to produce elemental halogen, into a porous, relatively inert substrate to produce a substrate-supported salt mixture. Thereafter, the substrate-supported salt mixture is contacted (stage 1) with a hydrogen halide while maintaining the substrate-supported salt mixture during the contacting at an elevated temperature sufficient to sustain a reaction between the oxygen compound and the hydrogen halide to produce a gaseous elemental halogen product. This is followed by purging the substrate-supported salt mixture with steam (stage 2) thereby recovering any unreacted hydrogen halide and additional elemental halogen for recycle to stage 1. The dissolved oxygen compound is regenerated in a high temperature (stage 3) and an optical intermediate temperature stage (stage 4) by contacting the substrate-supported salt mixture with a gas containing oxygen whereby the dissolved oxygen compound in the substrate-supported salt mixture is regenerated by being oxidized to a higher valence state.

  7. Strongly localized anharmonic modes in perfect and imperfect crystals

    CERN Document Server

    Hizhnyakov, V; Sigmund, E E

    1999-01-01

    Localized modes of large amplitudes in nonlinear lattices are considered. The applied method allows the reduction of nonlinear problem to a linear inverse problem of phonons scattering on a local potential. The method is efficient in the case of strongly localized modes. Analytical description of such modes in monatomic chain is given. Results of numerical calculations of anharmonic local vibrations of light ions in pure and impure alkali halide crystal are presented. It is found that, in the case of amplitudes ~0.5A, the vibrations depend very strongly on the crystallographic directions.

  8. Fabrication of La2Ti2O7 Crystals Using an Alkali-Metal Molybdate Flux Growth Method and Their Nitridability To Form LaTiO2N Crystals under a High-Temperature NH3 Atmosphere.

    Science.gov (United States)

    Hojamberdiev, Mirabbos; Yamaguchi, Akiko; Yubuta, Kunio; Oishi, Shuji; Teshima, Katsuya

    2015-04-01

    Flux growth is a promising method that allows one to control over the crystalline phase, crystal shape, crystal size, and crystal surface through the selection of a suitable flux. In this work, lanthanum titanate (La2Ti2O7) crystals with different morphologies were grown using the Na2MoO4, K2MoO4, NaCl, and mixed NaCl + K2MoO4 (molar ratio = 3:7) fluxes, and their nitridability to form LaTiO2N crystals under a high-temperature NH3 atmosphere was also investigated. The effects of the solute concentration and cooling rate on the growth of the La2Ti2O7 crystals were also studied. The X-ray diffraction results revealed that the {100} plane was dominant in the La2Ti2O7 platelet crystals grown using the alkali-metal molybdate fluxes. When the solute concentration was increased from 1 to 20 mol %, the average size of the crystals decreased without considerable alteration of the overall crystal morphology. The La2Ti2O7 crystals with the preferred ?010? and ?001? growth directions along the b and c axes were grown using the Na2MoO4 and K2MoO4 fluxes, respectively. Compared to the Na2MoO4 flux, the K2MoO4 flux did not show a cooling-rate-dependent effect on the growth of the La2Ti2O7 crystals. It was found that conversion of the La2Ti2O7 crystals to the LaTiO2N crystals was strongly dependent on the flux used to grow the precursor La2Ti2O7 crystals. That is, the La2Ti2O7 crystals grown using the K2MoO4 and NaCl fluxes were nearly completely converted into the LaTiO2N crystals, while conversion of the La2Ti2O7 crystals grown using the Na2MoO4 and mixed NaCl + K2MoO4 fluxes to the LaTiO2N crystals seemed to be not completed yet even after nitridation at 950 °C for 15 h using NH3 because of the larger crystal size and the presence of unintentional impurities (sodium and molybdenum from the flux) in the La2Ti2O7 crystal lattice. Nevertheless, the LaTiO2N crystals fabricated by nitriding the La2Ti2O7 crystals grown using the K2MoO4 and NaCl fluxes should be suitable for direct solar water splitting. PMID:25789564

  9. Pulsed copper halide vapor lasers

    Science.gov (United States)

    Kazarian, M. A.; Petrash, G. G.; Trofimov, A. N.

    The theory and the performance characteristics of copper halide lasers are examined with reference to recent theoretical and experimental research in the field of metal vapor lasers. The discussion covers gas discharge tubes, comparative characteristics of copper halide lasers, determination of the metastable level decomposition rates in copper chloride and copper bromide lasers, and spectroscopic measurements of the discharge plasma in copper halide lasers. Attention is also given to the kinetics of copper atoms formation in copper halide lasers and calculation of the kinetic characteristics of copper halide lasers.

  10. Transport and deposition of halide in alkali metal-stainless steel systems, (IV). Measurement of sodium iodide solubility in sodium with major constituents of stainless steel and oxide in sodium

    International Nuclear Information System (INIS)

    Solubility of sodium iodide in sodium is measured separately (a) with concentrations of major constituents leached from stainless steel in sodium and (b) with controlled concentration of oxide in sodium by the use of stainless steel capsule. The capsules loaded with 20 g sodium and 0.1-0.3 g powder of additives are heated at their upper part in a furnace and cooled at their bottom on brass plates. (a) After a given period of run for sodium iodide equilibration, the distribution of the iodide and constituents is fixed in solidified sodium by quenching the capsules. Sodium samples taken from the sectioned capsule tube are submitted to sodium dissolution by steam for determining the iodide and to vacuum distillation for determining the constituents. The iodide solubility appears to be in a reverse correlation with concentrations of iron and nickel and to be insensitive to change in those of chromium, manganese and silicon. (b) After a given period of run for sodium oxide equilibration, the sodium is solidified by quenching the capsule. Deposits on the capsule bottom is removed by sectioning the capsule tube and crystals of sodium iodide are introduced to the sectioned capsule on which an end plug is seal-welded. The capsule is again set under the large temperature gradient for a period of run for iodide equilibration. After fixing the iodide distribution in solidified sodium by the quenching, sodium samples are taken from the sectioned capsule tube and submitted to the stioned capsule tube and submitted to the sodium dissolution by steam for determining iodide in sodium. The iodide solubility data obtained from the present measurement are observed to be scarcely affected by the oxide concentration. (author)

  11. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    David T. Moore

    2014-08-01

    Full Text Available The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films.

  12. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    International Nuclear Information System (INIS)

    The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films

  13. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Moore, David T.; Sai, Hiroaki; Wee Tan, Kwan; Estroff, Lara A.; Wiesner, Ulrich, E-mail: ubw1@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)

    2014-08-01

    The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films.

  14. High Biomass Specific Methyl Halide Production Rates of Selected Coastal Marsh Plants and its Relationship to Halide Content

    Science.gov (United States)

    Manley, S. L.; Wang, N.; Cicerone, R. J.

    2002-12-01

    Salt tolerant coastal marsh plants (halophytes) have previously been shown to be globally significant producers of methyl chloride (MeCl) and methyl bromide (MeBr). While halophytes are known for their high salt content, there are few reports of their halide content. Our studies have attempted to quantify biomass specific methyl halide (MeX) production from these plants and relate it to tissue halide levels. MeCl, MeBr and MeI production rates and tissue chloride, bromide and iodide concentrations from selected coastal marsh plants were measured for nearly a year. Certain halophyte species (i.e. Batis and Frankenia) have very high summer biomass specific production rates for MeX (e.g. Frankenia: 1 ug MeCl /gfwt/hr; 80 ng MeBr/gfwt/hr; 8 ng MeI/gfwt/hr). These rates of MeCl and MeBr production are much higher than those from other coastal marsh plants or seaweeds. Plant halide levels remain high throughout the year, while MeX production peaks at a high level in mid summer falling to low winter rates. This implies a linkage to plant growth. Higher levels of chloride and bromide were seen in the fleshy marsh plants such as Batis (saltwort, approximately 20 percent dry wt chloride, 0.4 percent dry wt bromide) and Salicornia (pickleweed) than in the others such as Frankenia (alkali heath) approx 7 percent dry wt chloride, 0.1 percent dry wt bromide) or Spartina (cordgrass). No such trend was seen for iodide, which ranged from 4 - 10 ppm. Calculations show the daily halide losses from MeX production are far less than the variability in tissue halide content. MeX production removes a small fraction of the total tissue halide from these plants suggesting that MeX production is not a mechanism used by these species to control internal halide levels. Saltwort cell-free extracts incubated with bromide or iodide in the presence of S-adenosyl-L-methionine (SAM) produced the corresponding MeX. MeBr production was inhibited by caffeic acid the substrate of lignin-specific O-methyl transferase. MeX production may be a result of non-specific methylation of halides by SAM utilizing methyl transferases used in other biosynthetic pathways.

  15. Detection of alkali metal ions in DNA crystals using state-of-the-art X-ray diffraction experiments

    OpenAIRE

    Tereshko, Valentina; Wilds, Christopher J.; Minasov, George; Prakash, Thaza P.; Maier, Martin A.; Howard, Andrew; Wawrzak, Zdzislaw; Manoharan, Muthiah; Egli, Martin

    2001-01-01

    The observation of light metal ions in nucleic acids crystals is generally a fortuitous event. Sodium ions in particular are notoriously difficult to detect because their X-ray scattering contributions are virtually identical to those of water and Na+…O distances are only slightly shorter than strong hydrogen bonds between well-ordered water molecules. We demonstrate here that replacement of Na+ by K+, Rb+ or Cs+ and precise measurements of anomalous differences ...

  16. Methods for synthesizing alane without the formation of adducts and free of halides

    Science.gov (United States)

    Zidan, Ragaiy; Knight, Douglas A; Dinh, Long V

    2013-02-19

    A process is provided to synthesize an alane without the formation of alane adducts as a precursor. The resulting product is a crystallized .alpha.-alane and is a highly stable product and is free of halides.

  17. Physicochemical and spectroscopic investigations of crystals of alkali-rare earth fluorides K2LnF5

    International Nuclear Information System (INIS)

    Using the hydrothermal method compounds K2LnF5 (Ln is Nd, ..., Lu, Y) and K2LnF5 (Ln is Gd, Lu, Y) activated by Nd3+ ions are synthesized. Spectroscopic studies of the above series of compounds are conducted. It is shown that K2LnF5-Nd3+ compounds are suitable media for exciting generation of induced radiation in the far IR range. The coefficient of Nd3+ ion distribution in hydrothermal synthesis of K2GdF5-Nd3+ crystals is estimated by the spectroscopic methods

  18. Ultrasonic attenuation measurements on crystals which display persistent nonphotochemical ir spectral hole burning

    OpenAIRE

    Lengfellner, Hans; A. J. Sievers

    1985-01-01

    Temperature-dependent ultrasound-absorption measurements have been used to identify an ReO4 --induced loss peak in alkali halide crystals. The measured shape is consistent with an activation process with barrier energies of 60 meV for RbBr, 50 meV for KI, and 30 meV for RbI. The temperature dependence of the hopping time is compatible with the disappearance of the persistent ir spectral features of ReO4 - as the temperature is increased to 10 K.

  19. Cold ablation driven by localized forces in alkali halides

    Science.gov (United States)

    Hada, Masaki; Zhang, Dongfang; Pichugin, Kostyantyn; Hirscht, Julian; Kochman, Micha? A.; Hayes, Stuart A.; Manz, Stephanie; Gengler, Regis Y. N.; Wann, Derek A.; Seki, Toshio; Moriena, Gustavo; Morrison, Carole A.; Matsuo, Jiro; Sciaini, Germán; Miller, R. J. Dwayne

    2014-05-01

    Laser ablation has been widely used for a variety of applications. Since the mechanisms for ablation are strongly dependent on the photoexcitation level, so called cold material processing has relied on the use of high-peak-power laser fluences for which nonthermal processes become dominant; often reaching the universal threshold for plasma formation of ~1?J?cm-2 in most solids. Here we show single-shot time-resolved femtosecond electron diffraction, femtosecond optical reflectivity and ion detection experiments to study the evolution of the ablation process that follows femtosecond 400?nm laser excitation in crystalline sodium chloride, caesium iodide and potassium iodide. The phenomenon in this class of materials occurs well below the threshold for plasma formation and even below the melting point. The results reveal fast electronic and localized structural changes that lead to the ejection of particulates and the formation of micron-deep craters, reflecting the very nature of the strong repulsive forces at play.

  20. Cold ablation driven by localized forces in alkali halides.

    Science.gov (United States)

    Hada, Masaki; Zhang, Dongfang; Pichugin, Kostyantyn; Hirscht, Julian; Kochman, Micha? A; Hayes, Stuart A; Manz, Stephanie; Gengler, Regis Y N; Wann, Derek A; Seki, Toshio; Moriena, Gustavo; Morrison, Carole A; Matsuo, Jiro; Sciaini, Germán; Miller, R J Dwayne

    2014-01-01

    Laser ablation has been widely used for a variety of applications. Since the mechanisms for ablation are strongly dependent on the photoexcitation level, so called cold material processing has relied on the use of high-peak-power laser fluences for which nonthermal processes become dominant; often reaching the universal threshold for plasma formation of ~1 J cm(-2) in most solids. Here we show single-shot time-resolved femtosecond electron diffraction, femtosecond optical reflectivity and ion detection experiments to study the evolution of the ablation process that follows femtosecond 400 nm laser excitation in crystalline sodium chloride, caesium iodide and potassium iodide. The phenomenon in this class of materials occurs well below the threshold for plasma formation and even below the melting point. The results reveal fast electronic and localized structural changes that lead to the ejection of particulates and the formation of micron-deep craters, reflecting the very nature of the strong repulsive forces at play. PMID:24835317

  1. Exciton-relaxation dynamics in lead halides

    International Nuclear Information System (INIS)

    We survey recent comprehensive studies of exciton relaxation in the crystals of lead halides. The luminescence and electron-spin-resonance studies have revealed that excitons in lead bromide spontaneously dissociate and both electrons and holes get self-trapped individually. Similar relaxation has been also clarified in lead chloride. The electron-hole separation is ascribed to repulsive correlation via acoustic phonons. Besides, on the basis of the temperature profiles of self-trapped states, we discuss the origin of luminescence components which are mainly induced under one-photon excitation into the exciton band in lead fluoride, lead chloride, and lead bromide

  2. Halide laser glasses

    International Nuclear Information System (INIS)

    Energy storage and energy extraction are of prime importance for efficient laser action and are affected by the line strengths and linewidths of optical transitions, excited-state lifetimes, nonradiative decay processes, spectroscopic inhomogeneities, nonlinear refractive index, and damage threshold. These properties are all host dependent. To illustrate this, the spectroscopic properties of Nd3+ have been measured in numerous oxide, oxyhalide, and halide glasses. A table summarizes the reported ranges of stimulated emission cross sections, peak wavelengths, linewidths, and radiative lifetimes associated with the 4F/sub 3/2/ ? 4I/sub 11/2/ lasing transition

  3. Search for improved-performance scintillator candidates among the electronic structures of mixed halides

    Science.gov (United States)

    Li, Qi; Williams, Richard T.; Burger, Arnold; Adhikari, Rajendra; Biswas, Koushik

    2014-09-01

    The application of advanced theory and modeling techniques has become an essential component to understand material properties and hasten the design and discovery of new ones. This is true for diverse applications. Therefore, current efforts aimed towards finding new scintillator materials are also aligned with this general predictive approach. The need for large scale deployment of efficient radiation detectors requires discovery and development of high-performance, yet low-cost, scintillators. While Tl-doped NaI and CsI are still some of the widely used scintillators, there are promising new developments, for example, Eu-doped SrI2 and Ce-doped LaBr3. The newer candidates have excellent light yield and good energy resolution, but challenges persist in the growth of large single crystals. We will discuss a theoretical basis for anticipating improved proportionality as well as light yield in solid solutions of certain systems, particularly alkali iodides, based on considerations of hot-electron group velocity and thermalization. Solid solutions based on NaI and similar alkali halides are attractive to consider in more detail because the end point compositions are inexpensive and easy to grow. If some of this quality can be preserved while reaping improved light yield and possibly improved proportionality of the mixture, the goal of better performance at the low price of NaI:Tl might be attainable by such a route. Within this context, we will discuss a density functional theory (DFT) based study of two prototype systems: mixed anion NaIxBr1-x and mixed cation NaxK1-xI. Results obtained from these two prototype candidates will lead to further targeted theoretical and experimental search and discovery of new scintillator hosts.

  4. Electrical conductivities of molten alkali halide-alkaline earth halide mixtures

    International Nuclear Information System (INIS)

    Specific and molar electrical conductivities of molten iodide mixtures were measured. A multiple-term polynomial equation was used to describe the temperature and concentration dependence of specific electrical conductivity. Molar conductivity of molten mixtures gives a linear dependence on the kind of cations and anions. (author)

  5. Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975

    Science.gov (United States)

    James, Odette B.; Lindstrom, Marilyn M.; Flohr, Marta K.

    1987-09-01

    Clasts of an unusual type of lunar highlands igneous rock, alkali gabbronorite, have been found in Apollo 16 breccia 67975. The alkali gabbronorites form two distinct subgroups, magnesian and ferroan. Modes and bulk compositions are highly varied. The magnesian alkali gabbronorites are composed of bytownitic plagioclase (Or2-5An82-89), hypersthene (Wo3-5En49-62), augite (Wo39-42En36-44), a silica mineral, and trace Ba-rich K-feldspar. The ferroan alkali gabbronorites are composed of ternary plagioclase (Or11-22An65-74), pigeonite (Wo6-9En35-47), augite (Wo38-40En29-35), Ba-rich K-feldspar, and a silica mineral. Trace minerals in both subgroups are apatite, REE-rich whitlockite, and zircon. The magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same, or closely related, parent magmas; the compositional data indicate that these magmas were REE-rich. The ternary plagioclase is probably a high-temperature metastable phase formed during crystallization. In composition and mineralogy, the 67975 alkali gabbronorites show many similarities to Appllo 12 and 14 alkali norites, alkali gabbronorites, and alkali anorthosites, and all these rocks together constitute a distinctive alkali suite. In addition, the alkali gabbronorites, show some similarities to KREEP basalts, Mg-norites, and some felsites. These data suggest genetic links between some or all of these types of pristine rocks. Two types of relationships are possible. The first is that alkali-suite rocks crystallized in plutons of KREEP basalt magma, and KREEP basalts are their extrusive equivalents. The second is that the alkali-suite rocks and some felsites all crystallized in plutons of Mg-norite parent magmas, and KREEP basalt magmas formed by remelting of these plutons. Additional studies are needed to resolve which of these hypotheses is correct.

  6. Research update : physical and electrical characteristics of lead halide perovskites for solar cell applications

    OpenAIRE

    Bretschneider, Simon A.; Weickert, Jonas; Dorman, James A.; Schmidt-mende, Lukas

    2014-01-01

    The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We...

  7. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    OpenAIRE

    Bretschneider, Simon A.; Jonas Weickert; Dorman, James A.; Lukas Schmidt-Mende

    2014-01-01

    The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We...

  8. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    Directory of Open Access Journals (Sweden)

    Simon A. Bretschneider

    2014-04-01

    Full Text Available The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We discuss the crystal and band structure of perovskite materials currently implemented in solar cells and the impact of the crystal properties on ferroelectricity, ambipolarity, and the properties of excitons.

  9. Multiphased mixed crystals: Interconnection of the conductivity activation energy with bulk properties

    International Nuclear Information System (INIS)

    Using the miscible alkali halides, viz. N?Br and KCl, multiphased binary and ternary mixed crystals have recently been grown. Such crystals are important because of their potential applications, for example, for the construction of laser optical windows. The temperature dependence of their conductivity and the corresponding activation energy E have also been recently reported for various compositions. Here, we show that, upon combining experimental data alone, an interesting correlation emerges, which indicates that the energy E varies linearly with B?, where B stands for the measured bulk modulus of the multiphased mixed crystals and ? denotes the mean volume per atom. This conforms with an early model that interconnects the Gibbs energy for the formation and migration of defects in solids with bulk properties

  10. Hall Determination of Atomic Radii of Alkali Metals

    Science.gov (United States)

    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.)

  11. Effect of the nature of alkali and alkaline-earth oxides on the structure and crystallization of an aluminoborosilicate glass developed to immobilize highly concentrated nuclear waste solutions

    OpenAIRE

    Quintas, Arnaud; Caurant, Daniel; Majérus, Odile; Charpentier, Thibault; Dussossoy, Jean-Luc

    2008-01-01

    A complex rare-earth rich aluminoborosilicate glass has been proved to be a good candidate for the immobilization of new high level radioactive wastes. A simplified seven-oxides composition of this glass was selected for this study. In this system, sodium and calcium cations were supposed in other works to simulate respectively all the other alkali (R+=Li+, Rb+, Cs+) and alkaline-earth (R'2+=Sr2+, Ba2+) cations present in the complex glass composition. Moreover, neodymium or...

  12. Polar binary Zn/Cd-rich intermetallics: Synthesis, crystal and electronic structure of A(Zn/Cd)13 (A = alkali/alkaline earth) and Cs1.34Zn16

    International Nuclear Information System (INIS)

    The binary alkali/alkaline earth (A) zinc and cadmium (M) compounds that form the NaZn13 structure type (cubic, space group Fm3-bar c), which were known only from indexed X-ray powder diagrams, have been synthesized from stoichiometric mixtures of the elements and have been structurally characterized using a combination of single crystal data and the Rietveld method. The alkali zinc phases AIZn13 are only formed with the lighter alkali elements sodium to rubidium (AI=Na: a -bar =-bar 1227.3(2)-bar pm, R1=0.0205;AI=K: a -bar =-bar 1237.9(3)-bar pm, R1=0.0154;AI=Rb: a -bar =-bar 1245.19(1)-bar pm, Rp=0.0250), whereas the cadmium compounds AI Cd13 are stable only for the heavier alkali metals potassium to cesium (AI=K: a -bar =-bar 1379.2(4)-bar pm, R1=0.0118;AI=Rb: a -bar =-bar 1384.5(2)-bar pm, R1=0.0139;AI=Cs: a -bar =-bar 1392.0(3)-bar pm, R1=0.0381). In the crystal structures M-centered M(2)M(1)12 icosahedra are connected via strong exobonds (forming tetrahedral stars, stella quadrangula) to form a 3D net, in the interstices of which the alkali metals are located in a snub cube 24 coordination. In contrast, the alkaline earth (AII) zinc compounds with calcium, strontium and barium (AII=Ca: a -bar =-bar 1215.4(1)-bar pm, R1=0.0274;AII=Sr: a -bar =-bar 1222.2(2)-bar pm, R1=0.0154;AII=222.2(2)-bar pm, R1=0.0154;AII=Ba: a -bar =-bar 1235.8(2)-bar pm, R1=0.0227) show statistical defects at the Zn(2) position centering the Zn(1) icosahedra. Both the geometric and the electronic stability of the NaZn13 structure type, which can be assessed from the pseudo-bandgap calculated using FP-LAPW-DFT methods, are discussed. In contrast to the aforementioned systems, the NaZn13 type ceases to exist in the binary system Cs-Zn. In this case a phase Cs1.36Zn16 with a new structure type but very similar stoichiometry emerges. This compound is the first and only known phase in the system Cs-Zn and crystallizes with a new incommensurably modulated structure: its average structure (orthorhombic, space group Imma, a=264.2(5) -bar pm,b=720.8(14) -bar pm,c=1760(5) -bar pm, R1=0.0198) already indicates the representative structural features: in a 3D net of Zn atoms tubular channels filled by the Cs atoms are formed. This Cs filling is, due to geometric requirements, not commensurate with the Zn host structure resulting in a modulated structure with satellite reflections that can be indexed with a q-> vector of (0,-bar 0,-bar 0.2755). The final refinement in the superspace group (Pcn2(00g)sso,a=1760(5) -bar pm,b=720.8(14) -bar pm,c=264.2(5) -bar pm, wRmain=0.0550,wRsatellites=0.140) shows a strong occupational and a weak positional modulation of Cs in the channels formed by the Zn partial structure

  13. Oxoeuropates of alkali metals

    International Nuclear Information System (INIS)

    Full text: There are only few works on the study of M-Eu-O (M=Na-Cs) system. This is owing to extreme hygroscopicity and high volatility of alkali metal oxides used in the reaction with europium oxide. The use of other compounds such as nitrates and carbonates is undesirable because the chemical activity of these substances is not sufficient. Only data on the oxides with MEuO2 composition have been reported up till now. But the single-crystal X-ray diffraction was studied only for RbEuO2 . Reliable data on caesium oxoeuropates are not present. The use of alkali metal peroxide or superoxide in considerable abundance in the solid-state synthesis is a new and promising method for synthesis of transition metal sophisticated oxides with alkaline cations. This method allows us to get appropriate compounds in a short time with a good yield even at not-too-high temperatures. Heating Eu2O3 with Na-2O2, KO2 and CsO2 at about 500 deg C led to formation of yellow-green products. The reaction with caesium superoxide passed most intensively and was accompanied by high exothermal effect. The obtained substances differed in their X-ray powder diffraction parameters from the known ones. Absorption 151Eu Moessbauer spectra were single lines with the following parameters of isomer shift (?) relative to Eu2O3 and the width at half height (?): ?=0.33±0.03 mm.s-1, ?(?): ?=0.33±0.03 mm.s-1, ?=2.53?0.06 mm.s-1 for sodium europate; ?=0.16±0.03 mm.s-1, ?=2.95±0.05 mm.s-1 for potassium one and ?=0.18±0.03 mm.s-1, ?=2.92±0.09 mm.s-1 for caesium derivative. The synthesis of the compounds was lasting only a few seconds and no europium oxide was found in the products. However some heating had to be continued to crystallize the substance well. In this case the narrowing of the lines was seen in the Moessbauer spectra and X-ray patterns. The isomer shifts value prove that europium is trivalent in these compounds. Broadening of the Moessbauer lines for potassium and caesium europates is indicative of quadrupole interactions

  14. Investigation of change regularity of energy states of Mn2+ in halides

    International Nuclear Information System (INIS)

    Data on 4E, 4A1 (4G) and 4T1 (4G) energy states of Mn2+ ion in some halides have been obtained and analyzed. With use of the dielectric theory of the chemical bond for complex crystals, several chemical bond parameters were calculated. The change regularity of the energy states of Mn2+ in halides has been studied. The results show that the covalence, the coordination number and the radius of the central ion are the main factors influencing the energy states of Mn2+ ion in halides. The relationships between these factors and the energy state 4T1 (4G), the energy difference ?E (?E=4E, 4A1 (4G)?4T1 (4G)) of Mn2+ ion in halides were established: E=2.0898+0.8618 exp (?F/0.2431); ?E=0.3201+0.9713?F. These relationships allow us to predict the position of energy state 4T1 (4G) and the energy difference ?E of Mn2+ in halides. This work can be significant for further understanding the luminescent properties of Mn2+ and can be used to develop new Mn2+-doped phosphors. - Highlights: ? Relationship between F and energy state 4T1(4G) of Mn2+ in halides was set up. ? Relationship between F and energy difference ?E of Mn2+rence ?E of Mn2+ in halides was set up. ? Site occupation of Mn2+-doped halides with two or more cations can be made clear. ? Energy state 4T1(4G) and emission band of Mn2+ in halides can be predicted.

  15. Alkali metal hydride formation

    International Nuclear Information System (INIS)

    The present invention relates to a method of producing alkali metal hydrides by absorbing hydrogen gas under pressure into a mixture of lower alkyl mono amines and alkali metal alkyl amides selected from sodium and potassium amides formed from said amines. The present invention also includes purification of a mixture of the amines and amides which contain impurities, such as is used as a catalytic exchange liquid in the enrichment of deuterium, involving the formation of the alkali metal hydride

  16. Charged-soft-sphere potentials for trivalent metal halides

    International Nuclear Information System (INIS)

    Octahedral-type coordination by halogens in the liquid state has been reported for a number of trivalent metal ions from diffraction and Raman scattering experiments on their molten trihalides and from Raman scattering spectroscopy of liquid mixtures of trihalides with alkali halides. We analyze the available data on bond lengths and Raman frequencies by treating an isolated (MX6)3- species within a model which adopts charged-soft-sphere interionic potentials supplemented by an account of ionic polarization. The trivalent metal ions that we consider are M = La, Ce, Pr, Nd, Sm, Gd, Dy and Y for X = Cl and M = Al for X = F. The main result of the analysis is the prediction of trends in the soft-sphere repulsive parameters for the trivalent metal ions, leading to estimates of all the vibrational frequencies and the binding energy of such octahedral species. (author). 26 refs, 1 fig., 4 tabs

  17. Correlations between entropy and volume of melting in halide salts

    International Nuclear Information System (INIS)

    Melting parameters and transport coefficients in the melt are collated for halides of monovalent, divalent and trivalent metals. A number of systems show a deficit of entropy of melting relative to the linear relationships between entropy change and relative volume change on melting that are found to be approximately obeyed by a majority of halides. These behaviours are discussed on the basis of structural and transport data. The deviating systems are classified into three main classes, namely (i) fast-ion conductors in the high-temperature crystal phase such as AgI, (ii) strongly structured network-like systems such as ZnCl2, and (iii) molecular systems melting into associated molecular liquids such as SbCl3. (author). 35 refs, 1 fig., 3 tabs

  18. The solvent extraction of alkali metal ions with ?-diketones

    International Nuclear Information System (INIS)

    This work was undertaken to investigate effects of solvent and chelating-agent on the solvent extraction of alkali metal ions by seven ?-diketones, acetylacetone (Acac), benzoylacetone (BzA), dipivaloylmethane (DPM), dibenzoylmethane (DBM), thenoyltrifluoloacetone (TTA), benzoyltrifluoroacetone (BFA) and hexafluoroacetylacetone (HFA), and to separate lithium from alkali metals. The extraction of alkali metals increase with increasing donor power of the solvent: i.e., benzene Na>K>Rb>Cs, which is also the order in which the adduct formation of these ?-diketone chelates with donor solvents increase. The adduct formations between ?-diketone chelates of alkali metals and donor solvents markedly enhance the solubilities of the chelates in solvents and, consequently, the extractabilities of alkali metals with ?-diketones. Lithium was extracted with TTA in ether at such a low base concentration that sodium, potassium, rubidium and cesium were hardly extracted, and this enabled to separate lithium from other metals by the use of rubidium hydroxide (0.02 M). An attempt has been made to isolate alkali metal ?-diketone chelates and some chelates have been obtained as crystals. The infrared absorption bands arising from C=O and C.=C of TTA shift to lower frequencies in the alkali metal chelates with TTA, and consequently, ?-diketones is suggested to coordinate to alkali metal as a bidcoordinate to alkali metal as a bidentate ligand. (JPN)

  19. Dislocation Dynamics in a Crystal Lattice (Peierls-Nabarro) Relief

    CERN Document Server

    Petukhov, B V

    2007-01-01

    The theory of the dislocation motion in the periodic potential relief of the crystal lattice (the Peierls-Nabarro barriers) is reviewed. On the basis of the kink mechanism the temperature dependence of the flow stress is described for a wide class of materials. The theory of quantum mechanical dislocation tunnelling through the Peierls-Nabarro barriers is extended and compared with experimental data on the plasticity of alkali halides, BCC and HCP metals at low temperatures. The behavior of the flow stress at the range of athermic anomalies is modeled by changing the mechanism of the dislocation motion from the thermally activated hopping over the barriers to the quantum tunnelling through them. Some results of previous calculations are represented in a more explicit convenient for applications form. The pronounced effect of the switching between the normal and the superconducting states on the flow stress of metals is explained on the basis of the change in the dissipative properties of the electron subsyste...

  20. Development of Halide and Oxy-Halides for Isotopic Separations

    Energy Technology Data Exchange (ETDEWEB)

    Leigh R. Martin; Aaron T. Johnson; Jana Pfeiffer; Martha R. Finck

    2014-10-01

    The goal of this project was to synthesize a volatile form of Np for introduction into mass spectrometers at INL. Volatile solids of the 5f elements are typically those of the halides (e.g. UF6), however fluorine is highly corrosive to the sensitive internal components of the mass separator, and the other volatile halides exist as several different stable isotopes in nature. However, iodide is both mono-isotopic and volatile, and as such presents an avenue for creation of a form of Np suitable for introduction into the mass separator. To accomplish this goal, the technical work in the project sought to establish a novel synthetic route for the conversion NpO2+ (dissolved in nitric acid) to NpI3 and NpI4.

  1. Melting and liquid structure of polyvalent metal halides

    International Nuclear Information System (INIS)

    A short review is given of recent progress in determining and understanding liquid structure types and melting mechanisms for halides of polyvalent metals. The nature of the preferred local coordination for the polyvalent metal ion in the melt can usually be ascertained from data on liquid mixtures with halogen-donating alkali halides. The stability of these local coordination states and the connectivity that arises between them in the approach to the pure melt determines the character of its short-range and possible medium-range order. A broad classification of structural and melting behaviours can be given on the basis of measured melting parameters and transport coefficients for many compounds, in combination with the available diffraction data on the liquid structure of several compounds. Correlations have been shown to exist with a simple indicator of the nature of the chemical bond and also with appropriate parameters of ionic models, wherever the latter are usefully applicable for semiquantitative calculations of liquid structure. Consequences on the mechanisms for valence electron localization in solutions of metallic elements into strongly structured molten salts are also briefly discussed. (author). 46 refs, 4 figs, 2 tabs

  2. Self-Correction of Lanthanum-Cerium Halide Gamma Spectra (pre-print)

    International Nuclear Information System (INIS)

    Lanthanum-cerium halide detectors generally exhibit superior energy resolutions for gamma radiation detection compared with conventional sodium iodide detectors. However, they are also subject to self-activities due to lanthanum-138 decay and contamination due to beta decay in the low-energy region and alpha decay in the high-energy region. The detector's self-activity and crystal contamination jointly contribute a significant amount of uncertainties to the gamma spectral measurement and affect the precision of the nuclide identification process. This paper demonstrates a self-correction procedure for self-activity and contamination reduction from spectra collected by lanthanum-cerium halide detectors. It can be implemented as an automatic self-correction module for the future gamma radiation detector made of lanthanum-cerium halide crystals.

  3. Emission bands in luminescence exhibited by X-ray irradiated KCl and NaCl single crystals later subjected to strong electric fields

    International Nuclear Information System (INIS)

    Studies on colour centres in alkali halide crystals like KCl and NaCl irradiated with X-rays under strong electric fields have given valuable information regarding the defect processes taking place in them. For example, the concentration of F-centres in such samples is considerably larger than that in samples which are X-ray irradiated only; also, the thermoluminescence (TL) output in the glow peaks in these crystals is greater. Subsequent work has shown that many of the F-centres produced in these solids by X-ray irradiation can be destroyed even at room temperature by later subjecting the irradiated crystals to strong electric fields (d.c. or a.c.). Such destruction of F-centres is found to be associated with luminescence. The aim of this letter is to report the results of our measurements of the spectral characteristics of this light output in both materials. (author)

  4. Alkali and Halogen Chemistry in Volcanic Gases on Io

    CERN Document Server

    Schaefer, L

    2004-01-01

    We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10^-6 to 10^+1 bars) ranges, which overlap the nominal conditions at Pele (T = 1760 K, P = 0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. We predict the major alkali and halogen species in a Pele-like volcanic gas and the major alklai and halogen condensates. We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observation...

  5. Freeze Enhanced Halate Halide Reactions

    Science.gov (United States)

    Newberg, J. T.; Weaver, K.; Broderick, A.

    2014-12-01

    Relatively little is known about halate ion species (XO3-; X = I, Br, Cl) in atmospheric condensed phases. It was initial thought that iodate was a terminal stable species upon iodide oxidation. However, it is becoming increasingly recognized that reactions involving iodate can lead to reactive iodine, and this chemistry is accelerated under acidic conditions. The environmental concentrations and chemistry of bromate and chlorate are largely unexplored in environmental ices. We present results from a series of aqueous phase halate ion reactions with halides under acidic conditions, showing that the kinetics are strongly enhanced upon freezing. The products of these reactions are reactive halogens, which have important implications to marine boundary layer chemistry.

  6. Alkali metal ion battery with bimetallic electrode

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Methods of recovering alkali metals

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. ALKALI FUSION OF ROSETTA ZIRCON

    International Nuclear Information System (INIS)

    The decomposition of Rosetta zircon by fusion with different types of alkalis has been investigated. These alkalis include sodium hydroxide, potassium hydroxide and eutectic mixture of both. The influences of the reaction temperature, zircon to alkalis ratio, fusion time and the stirring of the reactant on the fusion reaction have been evaluated. The obtained results favour the decomposition of zircon with the eutectic alkalis mixture by a decomposition efficiency of 96% obtained at 500 0C after one hour

  9. Durability of beryllium fluoride glasses in water: comparison with other glasses and crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cline, C.F.; Kingman, D.D.; Weber, M.J.

    1979-01-01

    The water solubility of several fluoroberyllate glass compositions, several optical and laser glasses, and representative fluoride and alkali halide crystals, were measured so that the moisture resistances could be compared. Because of variations in tests used by commercial glass makers, a standard durability test procedure was used for all materials. Results showed that although fluoroberyllate glasses are more soluble in water than commercial silicate, phosphate, and fluorophosphate glasses, they are less soluble than many crystalline materials used in optical systems. Compositions are available with durability sufficient for use in normal atmospheric conditions. Since fluoroberyllate glasses transmit from less than 160 nm to ca 4000 nm, they should be potentially useful for many optical applications. 2 tables.

  10. Spectra of alkali atoms

    International Nuclear Information System (INIS)

    Emission spectra of alkali atoms has been determined by using spectrometer at the ultraviolet to infra red waves range. The spectra emission can be obtained by absorption spectrophotometric analysis. Comparative evaluations between experimental data and data handbook obtained by spark method were also presented. (author tr.)

  11. Fullerenes doped with metal halides

    International Nuclear Information System (INIS)

    The cage-like structure of fullerenes is a challenge to every experimental to put something inside - to dope the fullerenes. In fact, the research team that first identified C60 as a football-like molecule quickly succeeded in trapping metal atoms inside and in shrinking the cage around this atom by photofragmentation. In this paper we report the results of ''shrink-wrapping'' the fullerenes around metal halide molecules. Of special interest is the critical size (the minimum number of carbon atoms) that can still enclose the dopant. A rough model for the space available inside a carbon cage gives good agreement with the measured shrinking limits. (author). 8 refs, 6 figs

  12. The effect of doses, irradiation temperature, and doped impurities in the thermoluminescence response of NaCl crystals

    International Nuclear Information System (INIS)

    The interactions between ionizing gamma-radiation and two alkali halide single crystals, NaCl doped with Cd2+ (0.5 mol %) or Mn2+ (0.087 mol %), were analyzed for their possible use as low dose dosimeters. For that purpose, two irradiation temperatures (298 K and 77 K) and different doses at a fix dose rate were studied. The irradiated crystals were analyzed using their thermoluminescence and optical absorption properties. The F-centers formed in these crystals were measured as a function of the dose. The production of irradiation defects in the solid were correlated with the glow curve. Bleaching the F-centers produced a decrease in the peak of the glow curve, suggesting that F centers are intimately involved in the production of the thermoluminescence phenomenon. For the NaCl crystals doped with Cd, the area under the peak observed in the glow curves (associated to very deep traps) changes uniformly in the 1.15–13.8 Gy dose intervals, making this crystal a candidate for use as a dosimeter in low dose intervals. -- Highlights: ? The gamma irradiation of single crystals of NaCl doped with Cd or Mn were studied. ? The bleaching of the F-centers produced a decrease of the peak of the glow curve. ? Crystals of NaCl:Cd can be use as a dosimeter at low radiation doses

  13. EXAFS studies of zinc halide glasses

    International Nuclear Information System (INIS)

    Structure of mixed halide glasses of ZnCl2-ZnBr2, ZnCl2-ZnI2 and ZnX2-KX' (X, X'=Cl, Br, I) systems was investigated by means of Zn K-edge, Br K-edge and I L3-edge EXAFS spectroscopy. The network structure of the ZnCl2-ZnBr2 and ZnCl2-ZnI2 glasses is composed of corner-sharing tetrahedral units, ZnClnX4-n (X=Br, I). The bond distances between zinc and halide ions are similar to those of the corresponding end members though they are slightly varied by the substitution of halide ion. The addition of K+ ions introduces non-bridging halide ions and decreases the bond distance. (author)

  14. Thermochemical properties of zirconium halides. A review

    Energy Technology Data Exchange (ETDEWEB)

    Van der Vis, M.G.M.; Cordfunke, E.H.P.; Konings, R.J.M. [Netherlands Energy Research Foundation ECN, Petten (Netherlands)

    1997-10-22

    Physico-chemical experiments are reviewed and the thermodynamic properties of solid and gaseous zirconium halides of the general formula ZrX{sub n} (X=F, Cl, Br, I; n=1-4) are evaluated and, where necessary, estimated by analogy with other metal halide systems. Thermodynamic key values at 298.15K and heat capacity equations are tabulated up to 1500K for the solid phase and 3000K for the gas phase

  15. Defects in anisotropic silver halide microcrystals studied with transmission electron microscopy

    Science.gov (United States)

    van Renterghem, Wouter

    2001-12-01

    For more than 100 years silver halide microcrystals, where the halide is chloride or bromide, are used as the light-sensing element in photographic films. The combination of properties, like high sensitivity, high resolution and excellent image quality, leads to its dominant use in the imaging industry. Only with the development of the CCD camera in recent years a valuable alternative was found. Yet the image quality is still inferior to silver halide films. Therefore it is believed that the silver halides will still play an important role in the 21st century. Despite the progress over the last 100 years, there is still room for improvement and therefore the silver halides are still intensively investigated. One part of the research deals with the production of homogeneous populations of silver halide crystals with a specific morphology. This thesis reports the results of an investigation of the defect structure in populations of tabular silver halide crystals. The influence of these defects on the morphology of the crystals and the photographic properties is discussed. The technique used for this investigation is transmission electron microscopy (TEM), which is suitable to visualise, to localise and to characterise the defects completely. The samples have been investigated mainly in plan view, but also in edge view. The samples for the edge-view investigation have been prepared with ultramicrotomy. First the growth mechanisms of tabular AgCl and AgBr crystals with {100} surfaces are studied. It is shown that in both cases a limited number of mixed dislocations with an a/2 Burgers vector, lying in the (001) plane induce the tabular growth. The origin of these defects has been determined and the relation with the anisotropic growth is explained. Next, the growth of AgCl crystals with {111} faces is investigated. Using similar growth conditions as for AgBr, a large number of globular crystals are produced and the growth mechanism of these globular crystals is discussed. It is shown that the presence of twins on a {111} type of plane that is not parallel with the tabular plane is responsible for the thickness growth. Further, the introduction of a mixed bromo-iodide shell with high iodide concentration in an AgBr {111} tabular crystal population is investigated. Different incorporation methods are compared and their influence on the defect structure and the thickness of the crystals is discussed and related to the incorporation kinetics of the iodide. The crystals have also been studied in edge view. This showed the location of the parallel twins and the shell with high iodide concentration. The shell with low iodide concentration and the stacking faults, on the other hand, were not recognised in edge view. In the last chapter of this thesis, the formation of silver filaments during development of AgBr {111} tabular crystals is investigated. The evolution of the filament growth and the defect structure are investigated. It is shown that a large number of parallel twins and stacking faults formed on {111} type planes are present in the majority of the filaments. Further the influence of thickness of the tabular crystals on the filament morphology and on the colour of the developed film is discussed. It is argued that the compactness of the filaments is the major difference between the samples.

  16. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors.

    Science.gov (United States)

    Zhu, Haiming; Fu, Yongping; Meng, Fei; Wu, Xiaoxi; Gong, Zizhou; Ding, Qi; Gustafsson, Martin V; Trinh, M Tuan; Jin, Song; Zhu, X-Y

    2015-06-01

    The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ? 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials. PMID:25849532

  17. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

    Science.gov (United States)

    Zhu, Haiming; Fu, Yongping; Meng, Fei; Wu, Xiaoxi; Gong, Zizhou; Ding, Qi; Gustafsson, Martin V.; Trinh, M. Tuan; Jin, Song; Zhu, X.-Y.

    2015-06-01

    The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm-2) and high quality factors (Q ~ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 1016 cm-3. Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

  18. Chlor-alkali electrolysis

    International Nuclear Information System (INIS)

    The chlor-alkali industry produces simultaneously chlorine (Cl2) and caustic soda (NaOH) by decomposition of a salt solution in water. Additionally to the chlorine and caustic soda, hydrogen (H2) is produced. The global production capacity of chlorine in 1995 was approximately 44 million tons. The development of the chlorine production capacity in Western Europe since 1960 is presented. The most important chlorine producer in Western Europe is Germany with 38 % of the annual chlorine capacity of Western Europe. The chlorine capacity in 1997 in different Western European countries and their share an the total capacity in Western Europe is also presented. World-wide several processes are available for the production of chlorine and caustic soda. The most important routes are the following: ion exchange membrane process; mercury cell process; diaphragm process. Several other processes are available but do not have a significant contribution to the total production. The geographical distribution of the processes differs widely. In Japan the membrane process is predominate with 73 %, in the United States the diaphragm process with 75 %, whereas in Western Europe the mercury cell process is the most important one (64 %) [EIPPCB, 2000]. Approximately 65 % of the global chlorine capacity is located in these three regions. A comparison of the relative contribution of different production technologies to the chlor-alkali capacity in these three regions andalkali capacity in these three regions and in the world in 1994 is given. The distribution of processes and capacities of chlor-alkali plants in some European countries is presented (October 1999). Note that any one plant can have more than one cell technology installed. (author)

  19. The alkali-aggregate reaction - concrete microstructure evolution

    International Nuclear Information System (INIS)

    The alkali-aggregate reaction has been studied by scanning electron microscopy and energy dispersive X-ray analysis, electron probe microanalysis, and X-ray diffraction in concretes containing glass aggregates or hornfels and greywacke aggregates. The surface reaction of the natural aggregates in alkaline solutions has been analysed by X-ray photo-electron spectrometry. The study of concretes with glass aggregates stored at 20 degrees Celcius and 100 percent relative humidity has revealed, irrespective of alkali content and type of cement, the formation of a gel containing SiO2, Na2O, CaO, MgO and Al2O3. Under heat and pressure (210 degrees Celcius at MPa for 48 hours), the gel crystallizes and yields silicates not very different from tobermorite found in autoclaved normal concretes but cotaining Na and K in solid solutions. The alkali reaction in two natural aggregate concretes, is also shown by the formation of gels and silicate crystals. The progressive structuring of the gels in silicate crystals is promoted by an increase in temperature. Ettringite and Ca(OH)2 reinforce the alkali-aggregate reaction which may be looked upon as a hydration reaction, partially of the pozzolanic type

  20. Alkali oxide-tantalum oxide and alkali oxide-niobium oxide ionic conductors

    Science.gov (United States)

    Roth, R. S.; Parker, H. S.; Brower, W. S.; Minor, D.

    1974-01-01

    A search was made for new cationic conducting phases in alkali-tantalate and niobate systems. The phase equilibrium diagrams were constructed for the six binary systems Nb2O5-LiNbO3, Nb2O5-NaNbO3, Nb2O5-KNbO3, Ta2O5-NaTaO3, Ta2O5-LiTaO3, and Ta2O5-KTaO3. Various other binary and ternary systems were also examined. Pellets of nineteen phases were evaluated (by the sponsoring agency) by dielectric loss measurements. Attempts were made to grow large crystals of eight different phases. The system Ta2O5-KTaO3 contains at least three phases which showed peaks in dielectric loss vs. temperature. All three contain structures related to the tungsten bronzes with alkali ions in non-stoichiometric crystallographic positions.

  1. Stability of V-type defects in Ca2+ and Tl+ potassium iodide crystals

    International Nuclear Information System (INIS)

    In alkali halides, interstitial halide atoms are created under ionizing radiations at room temperature and their stabilization is known to play an important role in the coloration process. In alkali iodides such as KI, the coloration efficiency is known to be drastically increased by the addition of divalent cations. By means of Raman experiments, we describe the different stages of formation of V-type defects in the case of Ca+2 doped KI. By using traps like Tl+ cations, we show that the interstitial stabilization is different and does not lead to the formation of polyiodides as observed in KI:Ca+2. (author)

  2. Barium halide nanocrystals in fluorozirconate based glass ceramics for scintillation application

    International Nuclear Information System (INIS)

    Europium (Eu)-activated barium halide nanocrystals in fluorozirconate based glass ceramics represent a promising class of Xray scintillators. The scintillation in these glass ceramics is mainly caused by the emission of divalent Eu incorporated in hexagonal BaCl2 nanocrystals which are formed in the glass matrix upon appropriate annealing. Experiments with cerium (Ce)-activated fluorozironate glass ceramics showed that Ce is an interesting alternative. In order to get a better understanding of the scintillation mechanism in Eu- or Ce-activated barium halide nanocrystals, an investigation of the processes in the corresponding bulk material is essential. The objective of this thesis is the investigation of undoped, Eu-, and Ce-doped barium halides by X-ray excited luminescence (XL), pulse height, and scintillation decay spectra. That will help to figure out which of these crystals has the most promising scintillation properties and would be the best nanoparticles for the glass ceramics. Furthermore, alternative dopants like samarium (Sm) and manganese (Mn) were also investigated. Besides the above-mentioned optical investigation electron paramagnetic resonance (EPR) and Moessbauer measurements were carried out in order to complete the picture of Eu-doped barium halides. The EPR data of Eu-doped BaI2 is anticipated to yield more information about the crystal field and crystal structure that will help to understand the charge carrier process during the scintillation process. The main focus of the Moessbauer investigations was set on the Eu-doped fluorochlorozirconate glass ceramics. The results of this investigation should help to improve the glass ceramics. The Eu2+/Eu3+ ratio in the glass ceramics should be determined and optimize favor of the Eu2+. We also want to distinguish between Eu2+ in the glass matrix and Eu2+ in the nanocrystals. For a better understanding of Moessbauer spectroscopy on Eu also measurements on Eu in a CaF2 host lattice were carried out. (orig.)

  3. Crystal Electrostatic Energy

    OpenAIRE

    Ivanchin, Alexander

    2010-01-01

    It has been shown that to calculate the parameters of the electrostatic field of the ion crystal lattice it sufficient to take into account ions located at a distance of 1-2 lattice spacings. More distant ions make insignificant contribution. As a result, the electrostatic energy of the ion lattice in the alkaline halide crystal produced by both positive and negative ions is in good agreement with experiment when the melting temperature and the shear modulus are calculated. ...

  4. Unraveling halide hydration: A high dilution approach

    Science.gov (United States)

    Migliorati, Valentina; Sessa, Francesco; Aquilanti, Giuliana; D'Angelo, Paola

    2014-07-01

    The hydration properties of halide aqua ions have been investigated combining classical Molecular Dynamics (MD) with Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Three halide-water interaction potentials recently developed [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)], along with three plausible choices for the value of the absolute hydration free energy of the proton (? G^{ominus }_{hyd}[H^+]), have been checked for their capability to properly describe the structural properties of halide aqueous solutions, by comparing the MD structural results with EXAFS experimental data. A very good agreement between theory and experiment has been obtained with one parameter set, namely LE, thus strengthening preliminary evidences for a ? G^{ominus }_{hyd}[H^+] value of -1100 kJ mol-1 [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)]. The Cl-, Br-, and I- ions have been found to form an unstructured and disordered first hydration shell in aqueous solution, with a broad distribution of instantaneous coordination numbers. Conversely, the F- ion shows more ordered and defined first solvation shell, with only two statistically relevant coordination geometries (six and sevenfold complexes). Our thorough investigation on the effect of halide ions on the microscopic structure of water highlights that the perturbation induced by the Cl-, Br-, and I- ions does not extend beyond the ion first hydration shell, and the structure of water in the F- second shell is also substantially unaffected by the ion.

  5. Structure and bonding in metal-rich compounds: pnictides, chalcides and halides

    International Nuclear Information System (INIS)

    The subject is reviewed under the following headings: introduction (compounds included in the review; purpose of the review); MX compounds with M = transition metal and X = O,N,S or P; sulfides and selenides of the transition metals; transition-metal phosphides; alkali oxides; transition-metal oxides and nitrides with X/M < 1; metal-rich halides; conclusion. The references number 238. Compounds of the following principal elements of nuclear interest are included in the tables and text: Am, Ce, Cs, Eu, Gd, Hf, La, Mo, Np, Nb, Pu, Pr, Pa, Re, Ru, Sc, Ta, Tb, Th, W, U, V, Y, Zr. The information in the tables is presented under: structure type, space group, lattice parameters and remarks. (U.K.)

  6. Optical gaps of alkali borate and alkali fluoroborate glasses

    Science.gov (United States)

    Suzuki, Takenobu; Hirano, Masahiro; Hosono, Hideo

    2002-04-01

    The optical gaps of B2O3 alkali borate, and alkali fluoroborate glasses were determined by using blown films. The gap of B2O3 glass was 8.0 eV and the value decreased monotonically with decreasing the B2O3 content in both fluoroborate and borate glasses. When compared at a constant B2O3 content, the gap is in the order Li>Na>K and fluoroborate>borate. Ab initio molecular orbital calculation on the model clusters of the glasses revealed that the lowest excitations in B2O3 and alkali (fluoro) borate glasses are the transitions from nonbonding 2p orbitals of oxygen atoms in boroxol rings to vacant nonbonding 2p orbitals of boron atoms on "loose" BO3 triangles and from nonbonding 2p orbitals of oxygen atoms bonded with borons in tetrahedral coordination to the vacant ns orbitals of neighboring alkali ions, respectively. The vacant ns orbitals of the alkali ions neighboring oxygen atoms attached to tetrahedral borons primarily contribute to the lowest unoccupied molecular orbital (LUMO) levels. On the other hand, fluorine indirectly contributes to lowering the highest occupied molecular orbital (HOMO) levels via inductive effect (polarization of B-F ?-bond). It was therefore concluded that the effect of alkali addition on lowering LUMO levels is larger than that of fluorine addition on lowering the HOMO level.

  7. BRILLOUIN SCATTERING IN SILVER HALIDES

    OpenAIRE

    Hattori, T.; Imanishi, T.; Kurokawa, H.; Mitsuishi, A.

    1981-01-01

    Polarized Brillouin scattering spectra in AgBr and AgCl crystals were measured in the temperature region from room temperature to liquid phase temperature above the melting point. The anomaly that the acoustic phonon frequency shows a marked decrease at high temperature cannot be interpreted by a quasi-harmonic approximation. The discussion is given on the relation between the anomalous features and the increasing Frenkel defects.

  8. Upgrading platform using alkali metals

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Computational Screening of Mixed Metal Halide Ammines

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen

    Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. In this project we are searching for improved mixed materials with optimal desorption temperature and kinetics. We apply DFT calculations on mixed compounds selected by a Genetic Algorithm (GA), relying on biological principles of natural selection. The GA is evolving from an initial (random) population and selecting those with highest fitness, e.g. stability, release temperature and storage capacity. The search space includes all alkaline, alkaline earth, 3d and 4d metals and the four lightest halides, giving in total almost two million combinations.

  10. Lanthanide-halide based humidity indicators

    Science.gov (United States)

    Beitz, James V. (Hinsdale, IL); Williams, Clayton W. (Chicago, IL)

    2008-01-01

    The present invention discloses a lanthanide-halide based humidity indicator and method of producing such indicator. The color of the present invention indicates the humidity of an atmosphere to which it is exposed. For example, impregnating an adsorbent support such as silica gel with an aqueous solution of the europium-containing reagent solution described herein, and dehydrating the support to dryness forms a substance with a yellow color. When this substance is exposed to a humid atmosphere the water vapor from the air is adsorbed into the coating on the pore surface of the silica gel. As the water content of the coating increases, the visual color of the coated silica gel changes from yellow to white. The color change is due to the water combining with the lanthanide-halide complex on the pores of the gel.

  11. Shear viscosity of molten alkali halides from equilibrium and nonequilibrium molecular-dynamics simulations.

    Science.gov (United States)

    Galamba, N; de Castro, C A Nieto; Ely, James F

    2005-06-01

    The shear viscosity of molten NaCl and KCl was calculated through equilibrium (EMD) and nonequilibrium molecular-dynamics (NEMD) simulations in the canonical (N,V,T) ensemble. Two rigid-ion potentials were investigated, namely, the Born-Mayer-Huggins-Tosi-Fumi potential and the Michielsen-Woerlee-Graaf-Ketelaar potential with the parameters proposed by Ladd. The NEMD simulations were performed using the SLLOD equations of motion [D. J. Evans and G. P. Morriss, Phys. Rev. A 30, 1528 (1984)] with a Gaussian isokinetic thermostat and the results are compared with those obtained from Green-Kubo EMD (N,V,T) simulations and experimental shear viscosity data. The NEMD zero strain rate shear viscosity, eta(0), was obtained by fitting a simplified Carreau-type equation and by application of mode-coupling theory, i.e., a eta-gamma(1/2) linear relationship. The values obtained from the first method are found to be significantly lower than those predicted by the second. The agreement between the EMD and NEMD results with experimental data is satisfactory for the two potentials investigated. The ion-ion radial distribution functions obtained with the two rigid-ion potentials for both molten salts are discussed in terms of the differences between the two models. PMID:15974685

  12. Is surface layering of aqueous alkali halides determined by ion pairing in the bulk solution?

    Science.gov (United States)

    Brandes, Eva; Stage, Christiane; Motschmann, Hubert; Rieder, Julian; Buchner, Richard

    2014-11-01

    This contribution aims to elucidate the connection between ion-ion-solvent interactions in the bulk of aqueous electrolyte solutions and the properties of their liquid-air interface. In particular, we were interested in the conditions under which ion pairs form at the surface and whether this is linked to ion pairing in the bulk. For this reason different combinations of hard (Cl-, Li+) and soft ions (I-, Cs+) were investigated. Ion hydration and possible ion association in the bulk was probed with dielectric relaxation spectroscopy. This technique monitors the cooperative reorientation of the dipolar solvent molecules and detects all ion-pair species possibly present in the solution. At the interface, the formation of contact ion pairs was investigated by infrared-visible-sum frequency spectroscopy (SFG). This nonlinear optical technique possesses an inherent surface specificity and can be used for the characterization of interfacial water. The intensity of the SFG-active vibrational stretching modes depends on the number of oriented water molecules. The electric field at the surface of a charged aqueous interface aligns the water dipoles, which in turn increases the SFG response. Hence, the enhancement of the oscillator strengths of the water vibrational modes can be used to draw some conclusions on the strengths and geometrical extension of the electric field. The formation of ion pairs at the interface reduces the intensity of the band associated with hydrogen-bonded water. The underlying theory is presented. The combined data show that there are no contact ion pairs in the bulk of the fluid and—at best—only small amounts of solvent shared ion pairs. On the other hand, the combination of hard/hard or soft/soft ions leads to the formation of ion pairs at the liquid-air interface.

  13. Voltammetric behavior of erbium and lutetium ions in solutions of alkali metal halides

    International Nuclear Information System (INIS)

    A systematic study of voltammetric behavior of erbium and lutetium ions in 0.1-4.0 M MX solutions (M = Li, Na, K; X = Cl, Br, I) within pH 2.0-6.0 is performed. Cations and anions of background electrolyte, as well as the concentration of background solution and its pH value are studied for their effect on the behavior to optimize the conditions of erbium and lutetium determination by voltammetry. Detection limits for erbium and lutetium ions are found when using background solutions of optimum composition. 11 refs.; 5 figs.; 1 tab

  14. Electron emission from surfaces of alkali halides under the impact of metastable helium and neon atoms

    International Nuclear Information System (INIS)

    Energy distributions of the electrons ejected from the evaporated film surfaces of LiF, LiCl, LiBr, NaF and NaCl by the impact of metastable He and Ne atoms have been measured. The observed distribution curves have two distinct structures: one peak is dentified as the valence band structure caused by Penning ionization, while the other peak is ascribed to scattered electrons. The positions of the valence band peaks are shifted to lower ionization energy from the corresponding photoelectron peaks (by 0.1-1.5 eV depending on the substance). In contrast to the photoelectron spectra, the structure attributable to conduction bands appears only very weakly. The relative intensity of the peak caused by scattered electrons is either strong or weak depending on the combination of the metastable atom and the sample. The interpretation of this observation is that the scattered electron peak is enhanced when the energy of the metastable atom exceeds twice the band gap energy, i.e. when the electron-electron scattering of Penning electrons in the solid is feasible. (orig.)

  15. Optical properties of ? hole centres in alkali halides: II. MS-X? calculations

    Science.gov (United States)

    Cabria, I.; Moreno, M.; Aramburu, J. A.; Barriuso, M. T.; Rogulis, U.; Spaeth, J.-M.

    1998-07-01

    0953-8984/10/29/008/img9 calculations at different values of the metal-ligand distance, R, have been performed for 0953-8984/10/29/008/img10 units (0953-8984/10/29/008/img11, Br, I) subjected to the electrostatic potential of KX lattices. The results confirm that the optical absorption bands peaked at 3.4 and 4.2 eV in KCl:0953-8984/10/29/008/img12 can be associated with the 0953-8984/10/29/008/img13 and 0953-8984/10/29/008/img14 charge transfer (CT) transitions respectively of the 0953-8984/10/29/008/img15 complex. Also, the systematic red shift experienced by such transitions on passing from KX to RbX is related to the increase of R induced by the host lattice change. The spin-orbit coupling in 0953-8984/10/29/008/img16 and 0953-8984/10/29/008/img17 levels determines the sign of the magnetic circular dichroism of the optical absorption (MCDA) and it is shown that for bromides and iodides the two CT transitions can exhibit a different pattern as is experimentally observed. Also the non-existence of MCDA signal in the 0953-8984/10/29/008/img14 region of KCl:0953-8984/10/29/008/img12 is related to a practically zero value of the spin-orbit splitting. The existence of five CT peaks for iodides is explained through the 0953-8984/10/29/008/img20 component of the 0953-8984/10/29/008/img21 CT transition, whose oscillator strength increases following the ligand spin-orbit coefficient. As 0953-8984/10/29/008/img22 is always found to be located about 0.15 eV below 0953-8984/10/29/008/img16, this new component can also explain the asymmetry observed in the MCDA spectra of chlorides and bromides in the high energy side of the 0953-8984/10/29/008/img13 transition. In all these 0953-8984/10/29/008/img10 units, the unpaired electron is found to be located mainly on the X ligands, the charge on them increasing along the 0953-8984/10/29/008/img26 series. This is related to the corresponding decrease of the hyperfine constant for whose core polarization effects are calculated to be negligible. From the present results, the equilibrium 0953-8984/10/29/008/img27 distance would be close to 2.80 Å thus implying a 10% inwards relaxation with respect to the host lattice. To our knowledge these are the first calculations reported on heavy 0953-8984/10/29/008/img28 impurities.

  16. Thermal conductivity of molten alkali halides from equilibrium molecular dynamics simulations.

    Science.gov (United States)

    Galamba, N; Nieto de Castro, C A; Ely, J F

    2004-05-01

    The thermal conductivity of molten sodium chloride and potassium chloride has been computed through equilibrium molecular dynamics Green-Kubo simulations in the microcanonical ensemble (N,V,E). In order to access the temperature dependence of the thermal conductivity coefficient of these materials, the simulations were performed at five different state points. The form of the microscopic energy flux for ionic systems whose Coulombic interactions are calculated through the Ewald method is discussed in detail and an efficient formula is used by analogy with the methods used to evaluate the stress tensor in Coulombic systems. The results show that the Born-Mayer-Huggins-Tosi-Fumi potential predicts a weak negative temperature dependence for the thermal conductivity of NaCl and KCl. The simulation results are in agreement with part of the experimental data available in the literature with simulation values generally overpredicting the thermal conductivity by 10%-20%. PMID:15267797

  17. Interaction of the model alkyltrimethylammonium ions with alkali halide salts: an explicit water molecular dynamics study

    Directory of Open Access Journals (Sweden)

    M. Druchok

    2013-01-01

    Full Text Available We present an explicit water molecular dynamics simulation of dilute solutions of model alkyltrimethylammonium surfactant ions (number of methylene groups in the tail is 3, 5, 8, 10, and 12 in mixture with NaF, NaCl, NaBr, and NaI salts, respectively. The SPC/E model is used to describe water molecules. Results of the simulation at 298 K are presented in form of the radial distribution functions between nitrogen and carbon atoms of CH2 groups on the alkyltrimethylammonium ion, and the counterion species in the solution. The running coordination numbers between carbon atoms of surfactants and counterions are also calculated. We show that I- counterion exhibits the highest, and F- the lowest affinity to "bind" to the model surfactants. The results are discussed in view of the available experimental and simulation data for this and similar solutions.

  18. IR and visible wavelength obscuration by pyrotechnically generated alkali-halide smokes

    Science.gov (United States)

    Hanley, J. T.; Kile, J. N.; Wattle, B. J.; Mack, E. J.

    1983-01-01

    In pursuit of an effective IR wavelength screen and an increased understanding of the particle formation mechanisms and resultant size distribution, this year's efforts focused on two primary objectives: (1) Through a series of chamber tests, assess the visible and IR wavelength extinction characteristics of four recently developed NWC pyrotechnics: LiC1 1, LM9, LM11 and LM12 and (2) Through a series of chamber tests conducted by Calspan with participants from NRL and NWC, investigate the smoke particle size distribution as functions of pyrotechnic and associated burn parameters.

  19. Cerium doped lanthanum halides: fast scintillators for medical imaging

    International Nuclear Information System (INIS)

    This work is dedicated to two recently discovered scintillating crystals: cerium doped lanthanum halides (LaCl3:Ce3+ and LaBr3:Ce3+).These scintillators exhibit interesting properties for gamma detection, more particularly in the field of medical imaging: a short decay time, a high light yield and an excellent energy resolution. The strong hygroscopicity of these materials requires adapting the usual experimental methods for determining physico-chemical properties. Once determined, these can be used for the development of the industrial manufacturing process of the crystals. A proper comprehension of the scintillation mechanism and of the effect of defects within the material lead to new possible ways for optimizing the scintillator performance. Therefore, different techniques are used (EPR, radioluminescence, laser excitation, thermally stimulated luminescence). Alongside Ce3+ ions, self-trapped excitons are involved in the scintillation mechanism. Their nature and their role are detailed. The knowledge of the different processes involved in the scintillation mechanism leads to the prediction of the effect of temperature and doping level on the performance of the scintillator. A mechanism is proposed to explain the thermally stimulated luminescence processes that cause slow components in the light emission and a loss of light yield. Eventually the study of afterglow reveals a charge transfer to deep traps involved in the high temperature thermally stimulated luminescence. (author)

  20. Lanthanide doped strontium-barium cesium halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  1. Computational screening of mixed metal halide ammines

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen

    Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. The storage in the halide ammines is very safe, and the salts are therefore highly relevant as a carbon-free energy carrier in future transportation infrastructure. In this project we are searching for improved mixed materials with optimal desorption temperatures and kinetics, optimally releasing all ammonia in one step. We apply Density Functional Theory, DFT, calculations on mixed compounds selected by a Genetic Algorithm (GA), relying on biological principles of natural selection. The GA is evolving from an initial (random) population and selecting those with highest fitness, a function based on e.g. stability, release temperature and storage capacity. The search space includes all alkaline, alkaline earth, 3d and 4d metals and the four lightest halides. In total the search spaces consists of millions combinations, which makes a GA ideal, to reduce the number of necessarycalculations. We are screening for a one step release from either a hexa or octa ammine, and we have found promising candidates, which will be further investigated ? both computationally and experimentally.

  2. The coacervation of aqueous solutions of tetraalkylammonium halides

    International Nuclear Information System (INIS)

    The coacervation of aqueous solutions of tatraalkylammonium halides in the presence of not of inorganic halides and acids has been studied, considering thermodynamic and spectroscopic aspects. The importance of dispersion forces as well as forces resulting from hydrophobic hydration has been assessed. The analogy between these systems and anionic ion exchange resins has been shown especially for Uranium VI extraction

  3. Halogen bonding-based anion coordination in calixarene/inorganic halide/diiodoperfluorocarbon assemblies

    OpenAIRE

    Biella, Serena; Gattuso, Giuseppe; Notti, Anna; Metrangolo, Pierangelo; Pappalardo, Sebastiano; Parisi, Melchiorre F.; Pilati, Tullio; Resnati, Giuseppe; Terraneo, Giancarlo

    2009-01-01

    Abstract Self-assembly of ternary mixtures composed of cation segregating agent/inorganic halide (penta-tert-butyl-pentakis(ethoxycarbonylmethoxy)calix[5]arene (1)/NaI or 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8,8,8]hexacosane (4)/BaI2) and diiodoperfluorocarbon (1,8-diiodoperfluorooctane (2)) produces crystalline supramolecular salts 3 and 5, respectively, whose structural characteristics in the solid state have been elucidated by single-crystal X-ray analyses. Encapsulation of...

  4. Europium-doped barium halide scintillators for x-ray and ?-ray detections:

    OpenAIRE

    Selling, J.; M.D. Birowosuto; Dorenbos, P.; Schweizer, S.

    2007-01-01

    Single crystals of undoped or europium-doped barium chloride, bromide, and iodide were investigated under x-ray and ?-ray excitations. The Eu2+-related x-ray excited luminescence found in the Eu-doped barium halides occurs at 402, 404, and 425?nm for the chloride, bromide, and iodide, respectively. BaCl2:Eu2+ shows the best scintillation properties of the systems investigated. The light yield is about 20?000±2000?photons?per?MeV of absorbed ?-ray energy, the energy resolution for the 662?keV ...

  5. Europium-doped barium halide scintillators for x-ray and ?-ray detections

    International Nuclear Information System (INIS)

    Single crystals of undoped or europium-doped barium chloride, bromide, and iodide were investigated under x-ray and ?-ray excitations. The Eu2+-related x-ray excited luminescence found in the Eu-doped barium halides occurs at 402, 404, and 425 nm for the chloride, bromide, and iodide, respectively. BaCl2:Eu2+ shows the best scintillation properties of the systems investigated. The light yield is about 20 000±2000 photons per MeV of absorbed ?-ray energy, the energy resolution for the 662 keV photopeak is 8.8%±0.9%, and the scintillation decay time is 390±40 ns

  6. Evaluation of Ce3+ and alkali metal ions Co-doped LiSrAlF6 crystalline scintillators

    International Nuclear Information System (INIS)

    High scintillation efficiency of Eu-doped LiSrAlF6 (LiSAF) and LiCaAlF6 (LiCAF) codoped with alkali metal ions has been reported in our recent studies. Thus in this paper, we demonstrated the scintillation properties of 1% Ce-doped LiSAF crystals with 1% alkali metal ions co-doping to increase the light yield and understand the scintillation mechanism. The crystals showed intense emission band corresponding to the 5d-4f transition of Ce3+, and their light yields under thermal neutron excitation were higher than that of the Ce only doped crystal. Especially, the light yield of Ce–Na co-doped crystal exceeded about two times that of Ce only doped one. -- Highlights: ? Ce-doped and alkali metal co-doped LiSAF crystals were grown by ?-PD method. ? Alkali metal co-doped crystals showed higher light yield than Ce only doped crystal. ? Decay time of alkali metal co-doped LiSAF were longer than that of Ce only doped one

  7. Electrolytic method to make alkali alcoholates using ion conducting alkali electrolyte/separator

    Science.gov (United States)

    Joshi, Ashok V. (Salt Lake City, UT); Balagopal, Shekar (Sandy, UT); Pendelton, Justin (Salt Lake City, UT)

    2011-12-13

    Alkali alcoholates, also called alkali alkoxides, are produced from alkali metal salt solutions and alcohol using a three-compartment electrolytic cell. The electrolytic cell includes an anolyte compartment configured with an anode, a buffer compartment, and a catholyte compartment configured with a cathode. An alkali ion conducting solid electrolyte configured to selectively transport alkali ions is positioned between the anolyte compartment and the buffer compartment. An alkali ion permeable separator is positioned between the buffer compartment and the catholyte compartment. The catholyte solution may include an alkali alcoholate and alcohol. The anolyte solution may include at least one alkali salt. The buffer compartment solution may include a soluble alkali salt and an alkali alcoholate in alcohol.

  8. Effect of uniaxial stress on luminescence of undoped and thallium-doped KI and RbI crystals

    International Nuclear Information System (INIS)

    The effect of uniaxial stress applied at various temperatures along the (100) crystal axis on the self-trapped exciton (STE) and impurity-induced luminescence has been studied for pure and Tl+, Na+-containing KI and RbI crystals under excitation in the exciton and band-to-band absorption region as well as under x-ray excitation. An increase of the intrinsic/extrinsic emission intensity ratios has been observed and explained by the stress-induced (i) enhancement of the self-trapping efficiency of electronic excitations and the decrease of their migration length and (ii) suppression of the nonradiative decay of excitons into stable radiation defects. A strong influence of the uniaxial stress on the structure of the STE adiabatic potential energy surface has been detected in RbI which is evident in the stress-induced increase of the Ex/? and, particularly, of the ?/Ex emission intensity ratios. This effect has been connected with the increase in the energy barriers between various STE configurations in the compressed crystal lattice. The dependence of the on-centre STE emission intensity in alkali halides on the distance between the nearest lattice anions and on their size has been discussed. (author)

  9. Studies of rare gas halide lasers

    OpenAIRE

    Hogan, Daniel Christopher.; Webb, Colin E.; Dr. C. E. Webb

    1983-01-01

    This thesis presents the results of a study of the mechanisms responsible for limiting the laser pulse duration obtainable in xenon chloride lasers which are excited by UV-preionized, self-sustained gas discharges. The xenon chloride laser system, the principal emission band of which is centred around 308 nm, belongs to the class of high pressure gas lasers known as 'rare-gas halides'(RGH). RGH lasers are now well known for their high peak power output at a number of wavelen...

  10. Water Content of Lunar Alkali Fedlspar

    Science.gov (United States)

    Mills, R. D.; Simon, J. I.; Wang, J.; Alexander, C. M. O'D.; Hauri, E. H.

    2016-01-01

    Detection of indigenous hydrogen in a diversity of lunar materials, including volcanic glass, melt inclusions, apatite, and plagioclase suggests water may have played a role in the chemical differentiation of the Moon. Spectroscopic data from the Moon indicate a positive correlation between water and Th. Modeling of lunar magma ocean crystallization predicts a similar chemical differentiation with the highest levels of water in the K- and Th-rich melt residuum of the magma ocean (i.e. urKREEP). Until now, the only sample-based estimates of water content of KREEP-rich magmas come from measurements of OH, F, and Cl in lunar apatites, which suggest a water concentration of NanoSIMS data from granitic clasts from Apollo sample 15405,78 show that alkali feldspar, a common mineral in K-enriched rocks, can have approx. 20 ppm of water, which implies magmatic water contents of approx. 1 wt % in the high-silica magmas. This estimate is 2 to 3 orders of magnitude higher than that estimated from apatite in similar rocks. However, the Cl and F contents of apatite in chemically similar rocks suggest that these melts also had high Cl/F ratios, which leads to spuriously low water estimates from the apatite. We can only estimate the minimum water content of urKREEP (+ bulk Moon) from our alkali feldspar data because of the unknown amount of degassing that led to the formation of the granites. Assuming a reasonable 10 to 100 times enrichment of water from urKREEP into the granites produces an estimate of 100-1000 ppm of water for the urKREEP reservoir. Using the modeling of and the 100-1000 ppm of water in urKREEP suggests a minimum bulk silicate Moon water content between 2 and 20 ppm. However, hydrogen loss was likely very significant in the evolution of the lunar mantle. Conclusions: Lunar granites crystallized between 4.3-3.8 Ga from relatively wet melts that degassed upon crystallization. The formation of these granites likely removed significant amounts of water from some mantle source regions, e.g. later mare basalts predicting derivation from a mantle with <10 ppm water. However, this would have been a heterogeneous pro-cess based on K distribution. Thus some, if not most of the mantle may not have been devolatilized by this process; as seen by water in volcanic glasses and melt inclusions.

  11. Water Content of Lunar Alkali Fedlspar

    Science.gov (United States)

    Mills, R. D.; Simon, J. I.; Wang, J.; Alexander, C. M. O'D.; Hauri, E. H.

    2016-01-01

    Detection of indigenous hydrogen in a diversity of lunar materials, including volcanic glass, melt inclusions, apatite, and plagioclase suggests water may have played a role in the chemical differentiation of the Moon. Spectroscopic data from the Moon indicate a positive correlation between water and Th. Modeling of lunar magma ocean crystallization predicts a similar chemical differentiation with the highest levels of water in the K- and Th-rich melt residuum of the magma ocean (i.e. urKREEP). Until now, the only sample-based estimates of water content of KREEP-rich magmas come from measurements of OH, F, and Cl in lunar apatites, which suggest a water concentration of water content of the magma ocean would have water contents of 320 ppm for the bulk Moon and 1.4 wt % for urKREEP from plagioclase in ferroan anorthosites. Results and interpretation: NanoSIMS data from granitic clasts from Apollo sample 15405,78 show that alkali feldspar, a common mineral in K-enriched rocks, can have approx. 20 ppm of water, which implies magmatic water contents of approx. 1 wt % in the high-silica magmas. This estimate is 2 to 3 orders of magnitude higher than that estimated from apatite in similar rocks. However, the Cl and F contents of apatite in chemically similar rocks suggest that these melts also had high Cl/F ratios, which leads to spuriously low water estimates from the apatite. We can only estimate the minimum water content of urKREEP (+ bulk Moon) from our alkali feldspar data because of the unknown amount of degassing that led to the formation of the granites. Assuming a reasonable 10 to 100 times enrichment of water from urKREEP into the granites produces an estimate of 100-1000 ppm of water for the urKREEP reservoir. Using the modeling of and the 100-1000 ppm of water in urKREEP suggests a minimum bulk silicate Moon water content between 2 and 20 ppm. However, hydrogen loss was likely very significant in the evolution of the lunar mantle. Conclusions: Lunar granites crystallized between 4.3-3.8 Ga from relatively wet melts that degassed upon crystallization. The formation of these granites likely removed significant amounts of water from some mantle source regions, e.g. later mare basalts predicting derivation from a mantle with water. However, this would have been a heterogeneous pro-cess based on K distribution. Thus some, if not most of the mantle may not have been devolatilized by this process; as seen by water in volcanic glasses and melt inclusions.

  12. crystals

    Science.gov (United States)

    Badalyan, A.; Hovsepyan, R.; Mantashyan, P.; Mekhitaryan, V.; Drampyan, R.

    2014-07-01

    A novel combined interferometric-mask method for the formation of micro- and nanometric scale three-dimensional (3D) rotational symmetry quasi-crystalline refractive lattice structures in photorefractive materials is demonstrated experimentally. The method is based on micrometric scale spatial modulation of the light by amplitude mask in the radial directions and along the azimuthal angle and the use of counter-propagating beam geometry building up Gaussian standing wave, which defines the light modulation in the axial direction with half-wavelength periodicity. 3D intensity pattern can be represented as numerous mask-generated 2D quasi-periodic structures located in each anti-node of the standing wave. The formed 3D intensity distributions of the optical beams can be imparted into the photorefractive medium thus creating the micro- and sub-micrometric scale 3D refractive index volume lattices. The used optical scheme allows also the formation of 2D lattices by removing the back-reflecting mirror. 2D and 3D refractive lattices were recorded with the use of 532 nm laser beam and rotational symmetry mask in doped lithium niobate crystals and were tested by the probe beam far-field diffraction pattern imaging and direct observation by phase microscope. The formed rotational symmetry 3D refractive structures have the periods of 20-60 ?m in the radial directions, 60 ?m along the azimuthal angle and half-wavelength 266 nm in the axial direction.

  13. On-line alkali monitoring - Part 1

    International Nuclear Information System (INIS)

    As a consequence of the increased knowledge of the environmental impact of combustion based heat and power generation, the use of renewable biofuels will be increased. An obstacle associated to biofuel combustion compared to other fuels is the large release of alkali. Alkali compounds in flue gases are known to cause severe operational problems. Three of the major problems are; fouling of superheating tubes (causing reduced heat transfer and possibly corrosion), agglomeration of the bed material in fluidized beds, and poisoning of SCR catalysts. Yet another alkali related problem arises when, in order to increase the electric efficiency of combustion power plants, combined-cycle technology is used. Alkali vapour present in the fuel gas for the gas turbine is condensed to particles which increase corrosion and erosion of the turbine blades. The research on ash related operational problems has to be extended in order to ensure future use of biofuels in heat and power generation. In all successful research, adequate tools are necessary. To investigate ash related problems the key issue is to be able to perform continuous alkali measurements. This pilot study has investigated the need of continuous alkali measurements, which alkali species are harmful in the different applications and also available instrumentation capable of measuring the specific alkali species. The report gives a short summary presenting alkali related operational problems. In addition a schematic overview is given, showing the alkali species that possibly can exist in various parts of the power plant. 48 refs, 13 figs, 4 tabs

  14. Water Content of Lunar Alkali Fedlspar

    Science.gov (United States)

    Mills, R. D.; Simon, J. I.; Wang, J.; Alexander, C. M. O'D.; Hauri, E. H.

    2016-01-01

    Detection of indigenous hydrogen in a diversity of lunar materials, including volcanic glass, melt inclusions, apatite, and plagioclase suggests water may have played a role in the chemical differentiation of the Moon. Spectroscopic data from the Moon indicate a positive correlation between water and Th. Modeling of lunar magma ocean crystallization predicts a similar chemical differentiation with the highest levels of water in the K- and Th-rich melt residuum of the magma ocean (i.e. urKREEP). Until now, the only sample-based estimates of water content of KREEP-rich magmas come from measurements of OH, F, and Cl in lunar apatites, which suggest a water concentration of low water estimates from the apatite. We can only estimate the minimum water content of urKREEP (+ bulk Moon) from our alkali feldspar data because of the unknown amount of degassing that led to the formation of the granites. Assuming a reasonable 10 to 100 times enrichment of water from urKREEP into the granites produces an estimate of 100-1000 ppm of water for the urKREEP reservoir. Using the modeling of and the 100-1000 ppm of water in urKREEP suggests a minimum bulk silicate Moon water content between 2 and 20 ppm. However, hydrogen loss was likely very significant in the evolution of the lunar mantle. Conclusions: Lunar granites crystallized between 4.3-3.8 Ga from relatively wet melts that degassed upon crystallization. The formation of these granites likely removed significant amounts of water from some mantle source regions, e.g. later mare basalts predicting derivation from a mantle with <10 ppm water. However, this would have been a heterogeneous pro-cess based on K distribution. Thus some, if not most of the mantle may not have been devolatilized by this process; as seen by water in volcanic glasses and melt inclusions.

  15. Investigation regarding the role of chloride in organic-inorganic halide perovskites obtained from chloride containing precursors.

    Science.gov (United States)

    Dar, M Ibrahim; Arora, Neha; Gao, Peng; Ahmad, Shahzada; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

    2014-12-10

    As the photovoltaic performance of a device is strongly influenced by the morphology of perovskite, achieving precise control over the crystal formation of organic-inorganic halide perovskites synthesized in the ambience of chloride ions has garnered much attention. Although the resulting morphology dictates the performance of the device considerably, the understanding of the role of chloride ions has been scant. To unravel this mystery, we investigated three different organic-inorganic halide perovskite materials grown from the chloride-containing precursors under different but optimized conditions. Despite the presence of chloride ions in the reaction mixture, scanning transmission electron microscopy- energy dispersive spectroscopy (STEM-EDS) reveals that the CH3NH3PbI3 perovskites formed are chloride-free. Moreover bright field transmission electron microscopy indicates that chloride ions effect the growth of the CH3NH3PbI3. PMID:25392941

  16. Tellurium halide IR fibers for remote spectroscopy

    Science.gov (United States)

    Zhang, Xhang H.; Ma, Hong Li; Blanchetiere, Chantal; Le Foulgoc, Karine; Lucas, Jacques; Heuze, Jean; Colardelle, P.; Froissard, P.; Picque, D.; Corrieu, G.

    1994-07-01

    The new family of IR transmitting glasses, the TeX glasses, based on the association of tellurium and halide (Cl, Br, or I) are characterized by a wide optical window extending from 2 to 18 micrometers and a strong stability towards devitrification. Optical fibers drawn from these glasses exhibit low losses in the 7 - 10 micrometers range (less than 1 dB/m for single index fibers, 1 - 2 dB/m for fibers having a core-clad structure). The TeX glass fibers have been used in a remote analysis set-up which is mainly composed of a FTIR spectrometer coupled with a HgCdTe detector. This prototype system permits qualitative and quantitative analysis in a wide wavelength region lying from 3 to 13 micrometers , covering the fundamental absorption of more organic species. The evolution of a lactic and an alcoholic fermentation has been monitored by means of this set-up.

  17. Selective release of phosphorus and nitrogen from waste activated sludge with combined thermal and alkali treatment.

    Science.gov (United States)

    Kim, Minwook; Han, Dong-Woo; Kim, Dong-Jin

    2015-08-01

    Selective release characteristics of phosphorus and nitrogen from waste activated sludge (WAS) were investigated during combined thermal and alkali treatment. Alkali (0.001-1.0N NaOH) treatment and combined thermal-alkali treatment were applied to WAS for releasing total P(T-P) and total nitrogen(T-N). Combined thermal-alkali treatment released 94%, 76%, and 49% of T-P, T-N, and COD, respectively. Release rate was positively associated with NaOH concentration, while temperature gave insignificant effect. The ratio of T-N and COD to T-P that released with alkali treatment ranged 0.74-0.80 and 0.39-0.50, respectively, while combined thermal-alkali treatment gave 0.60-0.90 and 0.20-0.60, respectively. Selective release of T-P and T-N was negatively associated with NaOH. High NaOH concentration created cavities on the surface of WAS, and these cavities accelerated the release rate, but reduced selectivity. Selective release of P and N from sludge has a beneficial effect on nutrient recovery with crystallization processes and it can also enhance methane production. PMID:25690681

  18. Liquid alkali metals and alkali-based alloys as electron-ion plasmas

    International Nuclear Information System (INIS)

    The article reviews the theory of thermodynamic and structural properties of liquid alkali metals and alkali-based alloys, within the framework of linear screening theory for the electron-ion interactions. (author)

  19. Recent advances in new holographic silver halide materials

    OpenAIRE

    Neipp lópez, Cristian; Pascual Villalobos, Inmaculada; Beléndez Vázquez, Augusto

    2000-01-01

    Photographic emulsions are still one of the most widely used recording materials, due to the high energetic and spectral sensitivity and ease of processing. In order to obtain holograms of high quality on photographic emulsions, the different chemical procedures applied to the emulsions must be optimized. In this work we study two particular procedures, silver halide sensitized gelatin and fixation-free rehalogenating bleaching applied to two new commercial silver halide emulsions: the BB-64...

  20. Regenerable activated bauxite adsorbent alkali monitor probe

    Science.gov (United States)

    Lee, Sheldon H. D. (Willowbrook, IL)

    1992-01-01

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases.

  1. Seasonal variations in halides in marine brown algae from Porbandar and Okha coasts (NW coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, Ch.K.; Singbal, S.Y.S.

    1995-01-01

    percentage of enrichment factor) of halides shows that the tissue concentration of each halide was independent of other halides accumulation. The extent of bioaccumulation could be related to intrinsic property such as x space (spectroscopic electronegativity...

  2. Performance of Alkali Activated Slag with Various Alkali Activators

    Directory of Open Access Journals (Sweden)

    D.V.S.P.RAJESH

    2013-02-01

    Full Text Available The need to meet a sustainable development is now an important challenge to the cement industry. The production of OPC is responsible for about 7% of the world?s CO2 emission, a major contributor to the green house effect which is implicated in global warming and climatic changes, lead to the search for more environmentally viable alternative to cement. One of those alternative material is alkali activated slag (AAS where ground granulated blast furnace slag is used not as partial replacement to cement but also as a sole binder in the production of concrete. The overall aim of the study was to investigate the potential of alkali activated slag as a sole binder in producing concrete.The performance of alkali-activated slag concrete with sodium silicate, sodium hydroxide, sodium carbonate as activator are used at 4% Na2O(by weight of slag and 4% of hydrated lime by total weight of solid binder content if used as a retarder. The scope of the work covered four mixes: - Normal OPC mix and three alkali activated slag mixesof the same binder content and the same water binder ratio. The fresh concrete properties studied were setting time and workability and the Engineering properties studied are compressive strength was measured in 1,7,28 days, split tensile strength was measured in 7,28 days and flexure, punching shear strength was compared in 12 days only. The AAS concrete with different activators investigated was found to achieve good workability comparable with that of OPC. Sodium silicate, sodium hydroxide activated slag mixes sets very quickly. AAS concrete is much more sensitive to curing where if there is no addition of retarder (hydrated lime to the mix. Among AAS mix sodium silicate was the best; sodium carbonate was the second; and sodium hydroxide was third in terms of compressive, split tensile strengths and in terms of flexure strength and punching shear strength sodium hydroxide was best; sodium carbonate was second; sodium silicate (water glass was third.

  3. Energy transfer by borate and cyanide additives in gamma radiolytic decomposition of alkali metal nitrates

    International Nuclear Information System (INIS)

    Oxyanions are well known to form radical species after gamma irradiation and so the alkali halides (and even pseudohalides) from colour centres. Effect of borate and cyanide additives on the gamma radiolytic decomposition of sodium and potassium nitrates has shown enhancement in G(NO2-) calculated on the basis of electron fraction of the nitrate salt. Studies over a concentration range of 0.5 to 90 mol% of the additives and at different doses upto 1 MGy have shown maximum enhancement upto two orders of magnitude. It is proposed that energy transfer via radical species may be the main cause of enhancement in the radiolytic decomposition process. (author). 7 refs., 2 figs., 1 tab

  4. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Science.gov (United States)

    2010-07-01

    ...Substituted halogenated pyridinol, alkali salt. 721.8900 Section 721.8900 ...Substituted halogenated pyridinol, alkali salt. (a) Chemical substances and significant...substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and...

  5. Tellurite glass as a waste form for mixed alkali-chloride waste streams: Candidate materials selection and initial testing

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J., E-mail: brian.riley@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Rieck, Bennett T. [Washington State University, Pullman, WA 99164 (United States); McCloy, John S.; Crum, Jarrod V. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Sundaram, S.K. [Alfred University, Alfred, NY 14802 (United States); Vienna, John D. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer We provide the first standardized chemical durability test on tellurite glasses. Black-Right-Pointing-Pointer The glasses we studied showed a wide variety of chemical durability. Black-Right-Pointing-Pointer The best-performing glass showed good halide retention following melting and durability testing. Black-Right-Pointing-Pointer These glasses have very high densities resulting in high volumetric waste loading ability. - Abstract: Tellurite glasses have historically been shown to host large concentrations of halides. They are here considered for the first time as a waste form for immobilizing chloride wastes, such as may be generated in the proposed molten alkali salt electrochemical separations step in nuclear fuel reprocessing. Key properties of several tellurite glasses are determined to assess acceptability as a chloride waste form. TeO{sub 2} glasses with other oxides (PbO, Al{sub 2}O{sub 3} + B{sub 2}O{sub 3}, WO{sub 3}, P{sub 2}O{sub 5}, or ZnO) were fabricated with and without 10 mass% of a simulated (non-radioactive) mixed alkali, alkaline-earth, and rare earth chloride waste. Measured chemical durability is compared for the glasses, as determined by the product consistency test (PCT), a common standardized chemical durability test often used to validate borosilicate glass waste forms. The glass with the most promise as a waste form is the TeO{sub 2}-PbO system, as it offers good halide retention, a low sodium release (by PCT) comparable with high-level waste silicate glass waste forms, and a high storage density.

  6. Novel, inorganic composites using porous, alkali-activated, aluminosilicate binders

    Science.gov (United States)

    Musil, Sean

    Geopolymers are an inorganic polymeric material composed of alumina, silica, and alkali metal oxides. Geopolymers are chemical and fire resistant, can be used as refractory adhesives, and are processed at or near ambient temperature. These properties make geopolymer an attractive choice as a matrix material for elevated temperature composites. This body of research investigated numerous different reinforcement possibilities and variants of geopolymer matrix material and characterized their mechanical performance in tension, flexure and flexural creep. Reinforcements can then be chosen based on the resulting properties to tailor the geopolymer matrix composites to a specific application condition. Geopolymer matrix composites combine the ease of processing of polymer matrix composites with the high temperature capability of ceramic matrix composites. This study incorporated particulate, unidirectional fiber and woven fiber reinforcements. Sodium, potassium, and cesium based geopolymer matrices were evaluated with cesium based geopolymer showing great promise as a high temperature matrix material. It showed the best strength retention at elevated temperature, as well as a very low coefficient of thermal expansion when crystallized into pollucite. These qualities made cesium geopolymer the best choice for creep resistant applications. Cesium geopolymer binders were combined with unidirectional continuous polycrystalline mullite fibers (Nextel(TM) 720) and single crystal mullite fibers, then the matrix was crystallized to form cubic pollucite. Single crystal mullite fibers were obtained by the internal crystallization method and show excellent creep resistance up to 1400°C. High temperature flexural strength and flexural creep resistance of pollucite and polycrystalline/single-crystal fibers was evaluated at 1000-1400°C.

  7. High Pressure Electrochemistry: Application to silver halides

    Science.gov (United States)

    Havens, K.; Kavner, A.

    2007-12-01

    Electron and ion charge transfer processes help govern electrical conductivity and diffusive mass and heat transport properties in deep Earth minerals. In an attempt to understand how pressure influences charge transfer behavior, the halide silver bromide (AgBr) was studied under the influence of an electric potential difference applied across two electrodes in a diamond anvil cell. This study follows our previous work on AgI, which was found to dissociate to molecular iodine and silver metal due to pressure and voltage influences. We performed two sets of experiments on AgBr at high pressure in a diamond anvil cell: electrochemical dissociation and electrical resistance measurements. In our study, we were able to electrochemically dissociate AgBr at pressures of 0.25-1.6 GPa by applying a voltage across the electrodes in the diamond cell sample chamber. Ag metal grew visibly on the negatively-charged electrode when voltages varying from 0.1 V to 5 V were applied. Additionally, a dark blue color appeared in low pressure areas of the diamond cell and grew darker from both voltage application and light exposure, indicating photochemical effects. We found that the reaction area and growth rate of both metal and dark blue color strongly increased as voltage increased, but tended to decrease with greater pressure. The resistance across the cell was observed to be influenced by both pressure and light exposure. As the AgBr sample was exposed to visible light, the resistance dropped instantaneously, and after the light was turned off, the resistance increased on a timescale of 10's of seconds to minutes. Notably, at higher pressures, the AgBr showed less photosensitivity. Exploration of these metal halide systems has many potential applications. First, these experiments explore the pressure-dependence of photochemical and photovoltaic processes, and may spur development of pressure-tuned microscale electronic devices. Second, these experimental results can be used to constrain thermodynamic models of pressure-dependent electrochemical behavior of materials, which may then be applied to the high temperature, high pressure mineral phases of the deep Earth and planets.

  8. Soft scorpionate coordination at alkali metals.

    Science.gov (United States)

    Rajesekharan-Nair, Rajeev; Lutta, Samuel T; Kennedy, Alan R; Reglinski, John; Spicer, Mark D

    2014-05-01

    Reported here are the single-crystal X-ray structure analyses of bis-?-methanol-?(4)O:O-bis{[hydrotris(3-phenyl-2-sulfanylidene-2,3-dihydro-1H-1,3-imidazol-1-yl)borato-?(3)H,S,S'](methanol-?O)sodium(I)}, [Na2(C27H22BN6S3)2(CH4O)4] (NaTm(Ph)), bis-?-methanol-?(4)O:O-bis{[hydrotris(3-isopropyl-2-sulfanylidene-2,3-dihydro-1H-1,3-imidazol-1-yl)borato-?(3)H,S,S'](methanol-?O)sodium(I)}-diethyl ether-methanol (1/0.3333/0.0833), [Na2(C18H28BN6S3)2(CH4O)4]·0.3333C4H10O·0.0833CH3OH (NaTm(iPr)), and a novel anhydrous form of sodium hydrotris(methylthioimidazolyl)borate, poly[[?-hydrotris(3-methyl-2-sulfanylidene-2,3-dihydro-1H-1,3-imidazol-1-yl)borato]sodium(I)], [Na(C12H16BN6S3)] ([NaTm(Me)]n). NaTm(iPr) and NaTm(Ph) have similar dimeric molecular structures with ?(3)H,S,S'-bonding, but they differ in that NaTm(Ph) is crystallographically centrosymmetric (Z' = 0.5) while NaTm(iPr) contains one crystallographically centrosymmetric dimer and one dimer positioned on a general position (Z' = 1.5). [NaTm(Me)]n is a one-dimensional coordination polymer that extends along the a direction and which contains a hitherto unseen side-on ?(2)-C=S-to-Na bond type. An overview of the structural preferences of alkali metal soft scorpionate complexes is presented. This analysis suggests that these thione-based ligands will continue to be a rich source of interesting alkali metal motifs worthy of isolation and characterization. PMID:24816005

  9. TG-FTIR, DSC and quantum chemical studies of the thermal decomposition of quaternary methylammonium halides

    International Nuclear Information System (INIS)

    The thermal decomposition of quaternary methylammonium halides was studied using thermogravimetry coupled to FTIR (TG-FTIR) and differential scanning calorimetry (DSC) as well as the DFT, MP2 and G2 quantum chemical methods. There is almost perfect agreement between the experimental IR spectra and those predicted at the B3LYP/6-311G(d,p) level: this has demonstrated for the first time that an equimolar mixture of trimethylamine and a methyl halide is produced as a result of decomposition. The experimental enthalpies of dissociation are 153.4, 171.2, and 186.7 kJ/mol for chloride, bromide and iodide, respectively, values that correlate well with the calculated enthalpies of dissociation based on crystal lattice energies and quantum chemical thermodynamic barriers. The experimental activation barriers estimated from the least-squares fit of the F1 kinetic model (first-order process) to thermogravimetric traces - 283, 244 and 204 kJ/mol for chloride, bromide and iodide, respectively - agree very well with theoretically calculated values. The theoretical approach assumed in this work has been shown capable of predicting the relevant characteristics of the thermal decomposition of solids with experimental accuracy

  10. XRD study on pyrohydrolysed U-Zr and U-Pu-Zr alloys for halide extraction

    International Nuclear Information System (INIS)

    Pyrohydrolysis is a method which is routinely employed for clean separation of F and Cl from solid nuclear fuel matrices. In this process solid matrix is exposed to moist Ar/O2 at 900? temperature. The Halides in form of HF and HCl are extracted with vapor and are collected in dil. NaOH solution, which can be analyzed for F and Cl content by ion chromatography. A pyrohydrolysis method was optimized in our laboratory for analysis of proposed metallic fuels for fast reactors U-Zr and U-Pu-Zr alloys. The method showed faster recovery in presence of moist O2 as compared to moist Ar, which is unusual as most of the alloys analyzed can be efficiently pyrohydrolysed in Ar. A detailed study was performed on pyrohydrolysed products of U-Zr alloy, obtained on heating in moist argon and oxygen atmospheres using X-ray powder diffraction (XRD) and thermogravimetric methods. For U-Zr alloy heated in moist Ar the XRD of the product showed X-ray lines similar to UO2. Whereas after pyrohydrolysis of 30 min fractional U3O8 is detected which rises further with heating time. In comparison to this similar studies showed that U3O8 is detected even within 10 min in moist O2 as carrier gas and is the only oxide product. Thermo gravimetry study also supports this in which it was found that in presence of oxygen U3O8 is formed in single step. A correlation of halide recovery to fraction of U3O8 was found; in case of moist argon recovery is proportional to increasing time of pyrohydrolysis from 10 min. to 90 min. and the fraction of U3O8 increases from 0 to 100%. It can be concluded that the formation of U3O8 is very crucial for release of halides. This effect can be attributed to density of U3O8 8.34g/cc crystal structure as compared to UO2 10.96 g/cc, hence formation of U3O8 results in higher degree of expansion which will open the matrix significantly. From the observations it was inferred that though the MXn can be easily pyrohydrolysed, the recovery depends on the exposure of that part of MXn which is deep inside the matrix. The matrix opening is a crucial property required to produce reproducible recoveries for F and Cl. In this case it is the better opening of the matrix in moist oxygen, due to fast oxidation and formation of U3O8 which imparts expansion to the matrix leading to release of halides

  11. EPR and optical absorption studies on manganese ion doped in mixed alkali cadmium phosphate glasses

    International Nuclear Information System (INIS)

    Electron paramagnetic resonance (EPR) spectra of Mn(II) ions in cadmium phosphate glasses are presented with mixed alkali variation as xLi2O + (20 - x) Na2O + 20 CdO + 59.5 P2O5 + 0.5 MnO glass system with 5 ? x ? 15 mol%. The EPR spectra of Mn(II) ions doped samples exhibit a sextet centered at g = 2·0. The optical absorption spectrum at room temperature shows three bands for Mn(II) ions in octahedral symmetry. The crystal field (Dq) and Racah parameters (B and C) are evaluated. From EPR and optical spectral studies reveals the nature of the bonding is dominantly ionic and its site symmetry is octahedral. At equal composition of alkali content, i.e. for x = 10 the glass system shows the mixed alkali effect.

  12. Design and construction of a copper-halide laser

    International Nuclear Information System (INIS)

    The considerations necessary for the design and construction of an inexpensive, reliable copper halide laser are presented. A broad range of parameters which govern the output of the double-pulse copper-halide laser was studied. The laser has an optimum operating temperature which is different for each halide uCl, CuBr, CuI), but corresponds to a halide vapor pressure of about 0.1 torr for all three halides. At low repetition rates the highest laser output is achieved with helium as buffer gas. The laser output increases linearly with laser tube cross-section. As the tube diameter is increased, the dissociation energy must be increased, but not the excitation energy. A thyratron bias circuit has been developed which permits both dissociation and excitation pulses to be obtained from the same capacitor (with a small delay) without thyratron latch. Use of the single thyratron reduces the laser cost considerably. A laser tube with an operating life of many hundreds of hours has been designed. The description of a laser with an output of 0.5 mJ per pulse at repetition rates of up to 120 pulses per second is given. The design and construction of various components of this laser are given in detail. (authors)

  13. Unconventional superconductivity in electron-doped layered metal nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I)

    Science.gov (United States)

    Kasahara, Yuichi; Kuroki, Kazuhiko; Yamanaka, Shoji; Taguchi, Yasujiro

    2015-07-01

    In this review, we present a comprehensive overview of superconductivity in electron-doped metal nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I) with layered crystal structure and two-dimensional electronic states. The parent compounds are band insulators with no discernible long-range ordered state. Upon doping tiny amount of electrons, superconductivity emerges with several anomalous features beyond the conventional electron-phonon mechanism, which stimulate theoretical investigations. We will discuss experimental and theoretical results reported thus far and compare the electron-doped layered nitride superconductors with other superconductors.

  14. Atomic Force Microscopy Studies of Radiation Damage on Ionic Crystal Surfaces.

    Science.gov (United States)

    Wilson, Robert Mark

    1995-01-01

    The goal adopted at the start of work leading to this thesis was to image products of radiation damage on ionic surfaces with as high a resolution as possible. With this goal in mind, we explored the use of atomic force microscopy (AFM) as a novel tool for studying surface defects on insulators at mesoscopic scales (>10 nm), in anticipation of extending these measurements to the atomic scale. We studied the progressive desorption and defect evolution of KI using the tuning range of 4th harmonic Ti:sapphire laser light to excite the strongly absorbing exciton bands of the alkali iodides. We also studied CaF_2 metallization using low energy electrons. The first part of the thesis discusses the extent to which AFM may image non-periodic local atomic structures, and the significance of forces and surface adsorbates on the scanning process. Since our instrument was restricted to ambient atmosphere, we studied how sensitive the surface was to humidity using NaCl imaged at atomic resolution in a helium desiccated chamber. The intrusive nature of the tip makes defect observation difficult and transient, since the interaction may be unavoidably strong. But a thin water layer produces the best imaging conditions with humidities near ~25% to help buffer the loading force of the tip by supporting the main part of the mesoscopic (van der Waals) force, lubricating the surface and damping vibrations. We studied 12 alkali halide and alkaline earth fluoride crystals at atomic scale, the widest AFM survey of such materials to date, using an objective figure of merit to investigate correlations of different images with lattice constant, solubility, ratio of ionic radii, and polarizability, for example. As a class, ionic crystals are often unstable in electronic excited states, making it possible for electron or photon irradiation to produce vacancy-interstitial defect pairs from the relaxation of electron-hole pairs into self -trapped excitons. We performed in situ measurements of KI using uv laser irradiation to monitor the surface erosion and metallization in real time. This thesis addresses the important question of how reliably the AFM can image a surface at scales >10 nm while a laser producing near surface excitation densities ~10 ^{22} cm^{ -3} per second is focused on the sample around the cantilever. As in the case of alkali halides, when CaF _2 crystals are irradiated by electrons in vacuum at elevated temperature, F centers diffuse to the surface and nucleate forming calcium metal. Upon ceasing the irradiation and cooling the sample, the surface topography on the 10 nm and larger scale remains mostly stable upon exposure to air and consequent oxidation, so that AFM observations in air can detail the evidence of formation and migration of beam induced metallization achieved in vacuum. (Abstract shortened by UMI.).

  15. DELIGNIFICATION OF SUGARCANE BAGASSE WITH ALKALI AND PERACETIC ACID AND CHARACTERIZATION OF THE PULP

    Directory of Open Access Journals (Sweden)

    Ting Zhang

    2010-06-01

    Full Text Available Sugarcane bagasse was delignified with alkali and peracetic acid in a two-stage process to obtain pulps with high yield and low kappa number. The experimental results indicated that alkali pretreatment prior to peracetic acid (PAA delignification could significantly reduce PAA loading by partially removing lignin and swelling the fibers. An optimum condition for the two-stage delignification was obtained for pulping of sugarcane bagasse. The pulps were further characterized by chemical composition analysis, strength property tests, Fourier Transform Infrared Spectroscopy (FTIR, X-Ray Diffraction (XRD, and Thermal Gravimetric Analysis (TGA. It was found that the alkali-PAA process could be conducted under milder conditions with resulting higher pulping selectivity, higher degree of polymerization (DP, and superior mechanical properties of pulps, compared to the kraft pulping process. Both kraft pulps and alkali-PAA pulp had similar FTIR spectra, XRD spectra, and TGA (DTG curves. However, further analysis indicated that the alkali-PAA pulp had higher infrared crystallization index and cellulose crystallinity.

  16. Oxygen mobility in alkali feldspars

    International Nuclear Information System (INIS)

    The oxygen mobility is shown from oxygen atoms exchange between potassic and sodic feldspars and 18 oxygen enriched water. Exchanges are carried out in autoclaves between 400 and 800 deg. C under a water pressure between 300 and 800 bars. The oxygen is extracted from silicate by a ClF3 attack. Two distinct mechanisms may be found. The first one is auto-diffusion; for adularia we have: D = 9.10-7 exp(-32000/RT) (cm2.s-1), for albite: D 4.5.10-5 exp(-37000/RT) (cm2.s-1). The second one, more rapid, is associated with alkali atoms exchanges. These results are applied to the order-disorder problem in feldspars and to the oxygen geochemistry. (author)

  17. Raman and mid-infrared spectroscopic study of geometrically frustrated hydroxyl cobalt halides at room temperature

    International Nuclear Information System (INIS)

    Mid-infrared absorption and Raman spectra of the geometrically frustrated material series, hydroxyl cobalt halides ß-Co2(OH)3Cl and ß-Co2(OH)3Br, are first, to the best of our knowledge, measured at room temperature, to study the corresponding relationship between their vibrational spectral properties and crystal microstructures. Through the comparative analysis of the four spectra we have categorically assigned the OH-related vibration modes of hydroxyl groups in the trimeric hydrogen bond environment (Co3 ?OH)3 ... Cl/Br, and tentatively suggested vibration modes of O-Co-O, Co-O and Cl/Br-Co-Cl/Br units. These results can also become the basis for analysing their low-temperature spectral properties, which can help to understand the underlying physics of their exotic geometric frustration phenomena around phase transition temperatures. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  18. Diode pumped alkali vapor fiber laser

    Science.gov (United States)

    Payne, Stephen A. (Castro Valley, CA); Beach, Raymond J. (Livermore, CA); Dawson, Jay W. (Livermore, CA); Krupke, William F. (Pleasanton, CA)

    2007-10-23

    A method and apparatus is provided for producing near-diffraction-limited laser light, or amplifying near-diffraction-limited light, in diode pumped alkali vapor photonic-band-gap fiber lasers or amplifiers. Laser light is both substantially generated and propagated in an alkali gas instead of a solid, allowing the nonlinear and damage limitations of conventional solid core fibers to be circumvented. Alkali vapor is introduced into the center hole of a photonic-band-gap fiber, which can then be pumped with light from a pump laser and operated as an oscillator with a seed beam, or can be configured as an amplifier.

  19. Layered structures of organic/inorganic hybrid halide perovskites

    OpenAIRE

    Huan, Tran Doan; Tuoc, Vu Ngoc; Minh, Nguyen Viet

    2015-01-01

    Organic/inorganic hybrid halide perovskites, formed by substituting the cations A of ABX$_3$ halide perovskites with certain organic cations, may be used for solar thermoelectric applications. In this work, we systematically study three lead-free hybrid perovskites, i.e., methylammonium tin iodide CH$_3$NH$_3$SnI$_3$, ammonium tin iodide NH$_4$SnI$_3$, and formamidnium tin iodide HC(NH$_2$)$_2$SnI$_3$, by first-principles calculations. We find that in addition to the commonl...

  20. Alkali content of alpine ultramafic rocks

    Science.gov (United States)

    Hamilton, W.; Mountjoy, W.

    1965-01-01

    The lower limit of abundance of sodium and potassium in ultramafic rocks is less than the threshold amount detectable by conventional analytical methods. By a dilutionaddition modification of the flame-spectrophotometric method, sodium and potassium have been determined in 40 specimens of alpine ultramafic rocks. Samples represent six regions in the United States and one in Australia, and include dunite, peridotite, pyroxenite, and their variably serpentinized and metamorphosed derivatives. The median value found for Na2O is 0.004 per cent, and the range of Na2O is 0.001-0.19. The median value for K2O is 0.0034 per cent and the range is 0.001-0.031 per cent. Alkali concentrations are below 0.01 per cent Na2O in 28 samples and below 0.01 per cent K2O in 35. Derivation of basalt magma from upper-mantle material similar to such ultramafic rocks, as has been postulated, is precluded by the relative amounts of sodium and potassium, which are from 200 to 600 times more abundant in basalt than in the ultramafic rocks. Similar factors apply to a number of other elements. No reasonable process could produce such concentrations in, for example, tens of thousands of cubic miles of uniform tholeiitic basalt. The ultramafic rocks might have originated either as magmatic crystal precipitates or as mantle residues left after fusion and removal of basaltic magma. Injection of ultramafic rocks to exposed positions is tectonic rather than magmatic. ?? 1965.

  1. Alkali metal adsorption on graphite: a review

    Energy Technology Data Exchange (ETDEWEB)

    Caragiu, Mellita [Department of Physics and Astronomy, Ohio Northern University, 525 S Main Street, Ada, OH 45810 (United States); Finberg, Sharon [Department of Natural Sciences, Bentley College, 175 Forest Street Waltham, MA 02452 (United States)

    2005-09-07

    The adsorption of alkali metals on graphite has been the subject of various studies for the past two decades. Briefly, two main reasons can be offered to justify the persisting interest in these adsorption systems. First, experiments have pointed out intriguing structural phase transitions of the adsorbed species, and, second, in an attempt to explain the experimental results, the more complicated question of the nature of alkali metal-graphite bonding arose. Despite the relative simplicity of the electronic structure of the alkali metals, their interaction with the graphite surface is still the subject of current debate. This review paper presents relevant experimental data and results of selected theoretical calculations that, in time, guided the process of scientific discovery towards the current understanding of the alkali metals/graphite adsorption systems. (topical review)

  2. Alkali metal adsorption on graphite: a review

    International Nuclear Information System (INIS)

    The adsorption of alkali metals on graphite has been the subject of various studies for the past two decades. Briefly, two main reasons can be offered to justify the persisting interest in these adsorption systems. First, experiments have pointed out intriguing structural phase transitions of the adsorbed species, and, second, in an attempt to explain the experimental results, the more complicated question of the nature of alkali metal-graphite bonding arose. Despite the relative simplicity of the electronic structure of the alkali metals, their interaction with the graphite surface is still the subject of current debate. This review paper presents relevant experimental data and results of selected theoretical calculations that, in time, guided the process of scientific discovery towards the current understanding of the alkali metals/graphite adsorption systems. (topical review)

  3. Solutions of hydrogen in liquid alkali metals

    International Nuclear Information System (INIS)

    The paper reviews work carried out on solutions of hydrogen in liquid alkali metals. Phase diagrams for the lithium-hydrogen system are described, and equilibrium hydrogen pressure data for solutions in lithium, sodium, potassium, rubidium, caesium and sodium-potassium, are summarized. Solubility data for hydrogen in lithium, sodium, potassium, sodium-potassium, rubidium and caesium, are discussed. Finally, thermodynamic data for the alkali metal hydrides are given. (U.K.)

  4. Superconductivity in alkali-doped C60

    Science.gov (United States)

    Ramirez, Arthur P.

    2015-07-01

    Superconductivity in alkali-doped C60 (A3C60, A = an alkali atom) is well described by an s-wave state produced by phonon mediated pairing. Moderate coupling of electrons to high-frequency shape-changing intra-molecular vibrational modes produces transition temperatures (Tc) up to 33 K in single-phase material. The good understanding of pairing in A3C60 offers a paradigm for the development of new superconducting materials.

  5. Calcium silicate hydrate: Crystallisation and alkali sorption

    International Nuclear Information System (INIS)

    Homogeneous single C-S-H gels has been prepared for the investigation of alkali binding potential and crystallisation. A distribution coefficient, Rd, was introduced to express the partition of alkali between solid and aqueous phases at 25 deg. C. Rd is independent of alkali hydroxide concentration and depends only on Ca:Si ratio over wide ranges of alkali concentration. The trend of numerical values of Rd indicates that alkali bonding into the solid improves as its Ca:Si ratio decreases. Reversibility is demonstrated, indicating a possibility of constant Rd value of the material. Al has been introduced to form C-A-S-H gels and their alkali sorption properties also determined. Al substituted into C-S-H markedly increases Rd, indicating enhancement of alkali binding. However, the dependence of Rd on alkali concentration is non-ideal with composition. A two-site model for bonding is presented. Crystallisation both under saturated steam and 1 bar vapour pressure has been investigated. It has been shown that heat treatment by saturated steam causes crystallisation of gels. The principal minerals obtained were (i) C-S-H gel and Ca(OH)2 at -55 deg. C, (ii) 1.1 nm tobermorite, jennite and afwillite at 85 -130 deg. C, and (iii) xonotlite, foshagite and hillebrandite at 150-180 deg. C. Properties of crystalline C-S-H were also reported for reversible phase transformation, pH conditioning ability, seednsformation, pH conditioning ability, seeding effect and solubility. At 1 bar pressure, crystallisation is slower than in saturated steam due to lower water activity. Tobermorite-like nanodomains develop during reaction at low Ca/Si ratios. In some Ca-rich compositions, Ca(OH)2 is exsolved and occurs as nano-sized crystallites. (author)

  6. Method for calcining nuclear waste solutions containing zirconium and halides

    International Nuclear Information System (INIS)

    A reduction in the quantity of gelatinous solids which are formed in aqueous zirconium-fluoride nuclear reprocessing waste solutions by calcium nitrate added to suppress halide volatility during calcination of the solution while further suppressing chloride volatility is achieved by increasing the aluminum to fluoride mole ratio in the waste solution prior to adding the calcium nitrate

  7. Extraction of tellurium halide complexes with tetrasubstituted alkylamines

    International Nuclear Information System (INIS)

    Solvent extraction of tellurium (4) from halogen hydracid acid solutions by tetrabutyl-ethylenediamine, tetra exylethylenediamine, tetrhcaoyetylenediamine has been studied. The composition of the halide complexes of tellurium, extracted by the alkyldiamines, has been determined. A method of separation of tellurium from lead tin and iron and a procedure of extraction-photometric determination of tellurium in ores and cast iron have been developed

  8. Alternative route to metal halide free ionic liquids

    International Nuclear Information System (INIS)

    An alternative synthetic route to metal halide free ionic liquids using trialkyloxonium salt is proposed. Utility of this synthetic route has been demonstrated by preparing 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid through the reaction between 1-methylimidazole and triethyloxonium tetra-fluoroborate in anhydrous ether. (author)

  9. CO2 electrochemical reduction via adsorbed halide anions

    Science.gov (United States)

    Ogura, Kotaro; Salazar-Villalpando, Maria D.

    2011-01-01

    The electrochemical reduction of CO2 was studied utilizing halide ions as electrolytes, specifically, aqueous solutions of KCl, KBr, KI. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were a Pt wire and an Ag/AgCl electrode, respectively. The results of our work suggest a reaction mechanism for the electrochemical reduction of CO2 where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO2. Electron-transfer to CO2 may occur via the X- ad(Br-, Cl-, I-)-C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO2. The stronger the adsorption of the halide anion to the electrode, the more strongly CO2 is restrained, resulting in higher CO2 reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons; leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the over potential necessary for CO2 reduction, and thus increase the rate of electrochemical CO2 reduction.

  10. Radiation-induced mobility of interstitial alkali ions in iron-doped quartz

    International Nuclear Information System (INIS)

    Electron paramagnetic resonance (EPR) has been used to investigate charge-compensation mechanisms in iron-doped single crystals of quartz. In the case of substitutional Fe3+ ions, either an adjacent interstitial lithium or sodium ion or an adjacent OH- molecule provides the additional positive charge needed to maintain neutrality. These Fe3+ centers are known as S1, S3, and S2, respectively. Ionizing radiation does not remove the interstitial alkali ions from their positions next to the Fe3+ ions if the sample is below 130 K. Above the critical temperature of 130 K, radiation moves the lithium and sodium away from the Fe3+ ions and replaces them with hydrogen ions (i.e. protons). Thermal annealing in the 350-4500C range returns the alkali ions to the Fe3+ sites, thus restoring the crystal to its pre-irradiated state. (author)

  11. Solubility of alkali and alkaline earth metal sulfates in anhydrous hydrogen peroxide

    International Nuclear Information System (INIS)

    Solubility of alkali and alkaline earth metals sulfates is determined by isothermal method in anhydrous hydrogen method. Sodium sulfated of anhydrous hydrogen peroxide are crystallized in form of Na2SO4x2H2O2 solvates. Presence of peroxosolvates in the rest of solvates was not determined. Solubility of fluorides and perchlorates in hydrogen peroxide was also considered. 9 refs., 1 fig

  12. The role of alkali ions in the 190 K TSL peak in quartz

    International Nuclear Information System (INIS)

    The role of alkali ions in the creation of the thermally stimulated luminescence (TSL) peak at 190 K in quartz has been investigated by wavelength resolved TSL and thermally stimulated current (TSC) measurements performed on synthetic crystals, both as grown and hydrogen swept, characterised by alkali content of about 1-3 and 0.1 ppm respectively. The 190 K peak has been efficiently produced in as-grown crystals by a double irradiation procedure consisting of a first x-ray irradiation at 90 K followed by heating in the 170-300 K temperature range and a second irradiation at 90 K; this effect has not been observed in the hydrogen swept crystal. Moreover, the study of the spectral composition of the emitted light has shown the existence of two emission bands, one peaking at 450 nm (T150 K and peaking at around 380 nm. In as grown samples, TSC peaks at 205, 260 and at around 350 K (composite structure) have been detected: their intensities are much stronger in the as grown crystal and with the electric field oriented along the z-axis indicating that they have an ionic character. By taking into account the mechanism of formation of the [SiO4/M+]0 (M+=Li+, Na+) traps (previously found to be responsible for the 190 K TSL peak), the 205 K TSC peak can be attributed to the radiation induced dissociation of alkalis from [AlO4/M+]0 defect>4/M+]0 defect centres and subsequent migration near to Si sites; on the other hand, the 260 K TSC peak can be related to the subsequent disintegration of [SiO4/M+]0 defects involving the migration of alkalis to different ionic traps

  13. Multiple-scattering x-ray-absorption fine-structure analysis and thermal expansion of alkali halides

    Energy Technology Data Exchange (ETDEWEB)

    Frenkel, A.I. (School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978 (Israel)); Stern, E.A.; Qian, M.; Newville, M. (Department of Physics, University of Washington, Seattle, Washington 98195 (United States))

    1993-11-01

    X-ray-absorption fine-structure (XAFS) data of RbBr, RbCl, and KBr at 30 K and 125 K were measured and analyzed. An ionized-atom multiple-scattering calculation and a correlated Debye model were used for fitting the theory used in the computer code FEFF to data. The modifications of FEFF necessary to obtain good fits to the data are discussed. The results demonstrate the domination of single-scattering and focusing paths in XAFS and the determination of vibrational information through at least 10 A around the center atom. Numerical calculations were performed to analyze the cause of the difference found between the forward-scattering amplitudes of Rb[sup +] and Br[sup [minus

  14. Molecular Simulation of Aqueous Electrolyte Solubility. 3. Alkali-halide Salts and Their Mixtures in Water and in Hydrochloric Acid.

    Czech Academy of Sciences Publication Activity Database

    Mou?ka, F.; Lísal, Martin; Smith, W. R.

    2012-01-01

    Ro?. 116, ?. 18 (2012), s. 5468-5478. ISSN 1520-6106 R&D Projects: GA ?R GA203/08/0094; GA MŠk LH12020 Grant ostatní: NSERC(CA) OGP1041; EC(XE) COST TD0802 Institutional research plan: CEZ:AV0Z40720504 Keywords : molecular simulations * electrolyte hydrates * oemc simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.607, year: 2012

  15. Quantum efficiencies of imaging detectors with alkali halide photocathodes. I - Microchannel plates with separate and integral CsI photocathodes

    Science.gov (United States)

    Carruthers, George R.

    1987-07-01

    Measurements and comparisons have been made of the quantum efficiencies of microchannel plate (MCP) detectors in the far-UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiences were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are about 15 percent at 1216 A for a CsI-coated MCP compared with 65 percent for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20 percent for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration.

  16. Quantum efficiencies of imaging detectors with alkali halide photocathodes. 1: Microchannel plates with separate and integral Csl photocathodes.

    Science.gov (United States)

    Carruthers, G R

    1987-07-15

    We have measured and compared the quantum efficiencies of microchannel plate (MCP) detectors in the far- UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiencies were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are ~15% at 1216 A for a CsI-coated MCP compared with 65% for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20% for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration. PMID:20489984

  17. Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from Bacillus clausii

    OpenAIRE

    Brander, Søren; Mikkelsen, Jørn D.; Kepp, Kasper P.

    2014-01-01

    The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazi...

  18. Study of the point defect creation and of the excitonic luminescence in alkali halides irradiated by swift heavy ions

    International Nuclear Information System (INIS)

    The aim of this experimental thesis is to study the excitonic mechanisms and of the defect creation, in NaCl and KBr, under dense electronic excitations induced by swift heavy ion irradiations. In the first part, we present the main features of the interaction of swift heavy ions with solid targets, and after we review the well known radiolytic processes of the defect creation during X-ray irradiation. In the second chapter, we describe our experimental set-up. In the chapter III, we present our results of the in-situ optical absorption measurements. This results show that defect creation is less sensitive to the temperature than during a classical irradiation. Besides, we observe new mechanisms concerning the defect aggregation. In the chapter IV, we present the results of excitonic luminescence induced by swift by swift heavy ions. We observe that the luminescence yields only change with the highest electronic stopping power. In the chapter V, we perform thermal spike and luminescence yields calculations and we compare the numerical results to the experiments presented in the chapter IV. (author). 121 refs., 65 figs., 30 tabs

  19. Lighter Alkali hydride and deuteride 1: Electronic properties of pure solids

    International Nuclear Information System (INIS)

    The properties of lighter alkali hydrides of metals which crystallize in the rock-salt structure are discussed. First, the properties of pure crystals which are dominated by the electrons, in particular the energy levels and the eigenstates of the electrons in the absence of lattice defects are considered. After that, the optical properties of the solids excited at photon energies larger than those appropriate to lattice vibration and dominated by the transition of electron from the occupied core and valence levels to the normally empty conduction states, are discussed. 127 refs, 29 figs, 17 tabs

  20. Borate fluoride and fluoroborate in alkali-metal borate prepared by an open high-temperature solution method.

    Science.gov (United States)

    Wu, Hongping; Yu, Hongwei; Bian, Qiang; Yang, Zhihua; Han, Shujuan; Pan, Shilie

    2014-12-15

    By incorporation of the largest-electronegativity F atoms into borate, two novel halogen-containing borates, Li6RbB2O6F and K3B3O3F6, have been synthesized. Interestingly, Li6RbB2O6F is the first borate fluoride in alkali-metal borate. Meanwhile, K3B3O3F6 appears to be the first confirmed alkali-metal fluoroborate crystal grown by a high-temperature solution in air. PMID:25437774

  1. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.

    2012-01-01

    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  2. Superconducting intercalation compounds of metal nitride halides

    OpenAIRE

    Fogg, Am; Green, Vm; O Hare, D.

    1999-01-01

    The crystal structures of the layered host lattices, [?-ZrNBr and [?- HfNCl have been determined. They have been found to be isostructural with rhombohedral SmSI. New lithium intercalation compounds (Li(x)MNX; M = Zr, Hf; X = Cl, Br, I) have been prepared by treatment of either [?-ZrNBr, [?- HfNCl, ?-ZrNBr or ?-ZrNI with an excess of BuLi in hexane. These intercalates are all superconducting and show transition temperatures (T(c)) of 12, 20, 11 and 11 K respectively. The lithium interca...

  3. The influence of different parameters on the hydration process of binders based on alkali activated slag

    Directory of Open Access Journals (Sweden)

    DARKO KRIZAN

    2005-02-01

    Full Text Available The influence of certain types of activators (water glass Na2O·nSiO2 and sodium-metasilicate Na2SiO3·5H2O on the hydration process of alkali activated slag was investigated in this study. The influence of activator concentration, specific surface area of the slag and the modulus n of the water glass (mass ratio between SiO2 and Na2O on the kinetics of the hydration process i.e., the change of compressive strength were also investigated. Poorly crystallized low base calcium silicate hydrate C?S?H (I is the main hydration product of alkali activated slag regardless of the activator used. This is the reason for the rapid increase in the strength of alkali activated slag and also of the very high strength values. The strength growth rate and strength values were significantly higher when sodium?metasilicate was used as the activator than when water glass was used. The specific surface area of the slag and the activator concentration are parameters which have a closely connected influence on strength and their action is cumulative. The modulus n of water glass does not have an explicit influence on the strength of alkali activated slag.

  4. Compression-Driven Enhancement of Electronic Correlations in Simple Alkali Metals

    Science.gov (United States)

    Fabbris, Gilberto; Lim, Jinhyuk; Veiga, Larissa; Haskel, Daniel; Schilling, James

    2015-03-01

    Alkali metals are the best realization of the nearly free electron model. This scenario appears to change dramatically as the alkalis are subjected to extreme pressure, leading to unexpected properties such as the departure from metallic behavior in Li and Na, and the occurrence of remarkable low-symmetry crystal structures in all alkalis. Although the mechanism behind these phase transitions is currently under debate, these are believed to be electronically driven. In this study the high-pressure electronic and structural ground state of Rb and Cs was investigated through low temperature XANES and XRD measurements combined with ab initio calculations. The results indicate that the pressure-induced localization of the conduction band triggers a Peierls-like mechanism, inducing the low symmetry phases. This localization process is evident by the pressure-driven increase in the number of d electrons, which takes place through strong spd hybridization. These experimental results indicate that compression turns the heavy alkali metals into strongly correlated electron systems. Work at Argonne was supported by DOE No. DE-AC02-06CH11357. Research at Washington University was supported by NSF DMR-1104742 and CDAC/DOE/NNSA DE-FC52-08NA28554.

  5. Microscopic Surface Structure of Liquid Alkali Metals

    CERN Document Server

    Tostmann, H; Shpyrko, O G; Pershan, P S; Ocko, B M; Deutsch, M; Tostmann, Holger; Masi, Elaine Di; Shpyrko, Oleg G.; Pershan, Peter S.; Ocko, Benjamin M.; Deutsch, Moshe

    2004-01-01

    We report an x-ray scattering study of the microscopic structure of the surface of a liquid alkali metal. The bulk liquid structure factor of the eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the properties of an elemental liquid alkali metal. Analysis of off-specular diffuse scattering and specular x-ray reflectivity shows that the surface roughness of the K-Na alloy follows simple capillary wave behavior with a surface structure factor indicative of surface induced layering. Comparison of thelow-angle tail of the K67Na33 surface structure factor with the one measured for liquid Ga and In previously suggests that layering is less pronounced in alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not affect the surface structure, indicating that oxide and hydride are not stable at the liquid surface under these experimental conditions.

  6. ChemTeacher: Alkali Metals - Group 1 (IA)

    Science.gov (United States)

    2012-07-20

    ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Alkali Metals page includes resources for teaching students about the discovery, properties, and uses of the alkali metals.

  7. Synthesis and Characterization of Novel Ternary and Quaternary Alkali Metal Thiophosphates

    KAUST Repository

    Alahmary, Fatimah S.

    2014-05-01

    The ongoing development of nonlinear optical (NLO) crystals such as coherent mid-IR sources focuses on various classes of materials such as ternary and quaternary metal chalcophosphates. In case of thiophosphates, the connection between PS4-tetrahedral building blocks and metals gives rise to a broad structural variety where approximately one third of all known ternary (A/P/S) and quaternary (A/M/P/S) (A = alkali metal, M = metal) structures are acentric and potential nonlinear optical materials. The molten alkali metal polychalcophosphate fluxes are a well-established method for the synthesis of new ternary and quaternary thiophosphate and selenophosphate compounds. It has been a wide field of study and investigation through the last two decades. Here, the flux method is used for the synthesis of new quaternary phases containing Rb, Ag, P and S. Four new alkali metal thiophosphates, Rb4P2S10, RbAg5(PS4), Rb2AgPS4 and Rb3Ag9(PS4)4, have been synthesized successfully from high purity elements and binary starting materials. The new compounds were characterized by single crystal and powder X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-VIS), Raman spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These compounds show interesting structural variety and physical properties. The crystal structures feature 3D anionic framework built up of PS4 tetrahedral units and charge balanced by Ag and alkali metal cations. All prepared compounds are semiconductors with band gap between 2.3 eV to 2.6 eV and most of them are thermally stable up to 600ºC.

  8. Lanthanum halide scintillators: Properties and applications

    International Nuclear Information System (INIS)

    BrilLanCe[reg]-350 and BrilLanCe[reg]-380, Saint-Gobain Crystals' trade-names for LaCl3:Ce and LaBr3:Ce are being brought to market under exclusive license to Delft and Bern Universities. We are reporting the properties of crystals produced with commercially viable processes and find they match others' observations. These scintillators are bright (60,000 photons/MeV for LaBr3:Ce) and have very linear response, a combination that leads to very good energy resolution (3:Ce). The materials also have fast scintillation decay times (3:Ce). These excellent properties are retained at high temperature with only moderate light loss (138 and Ac227, the latter having been substantially reduced in recent processing. BrilLanCe[reg]-350 is now available in detectors up to 51 mm diameter while 38 mm diameter is available for BrilLanCe[reg]-380. Larger sizes are expected

  9. Preparation of high purity alkali metals

    International Nuclear Information System (INIS)

    The paper surveys the methodology of preparation of high purity alkali metals. The physicochemical and chemical methods of preparation and purification are described, including dissociation substitution, and chemical purification. The physical purification processes for alkali metals are also discussed. These are divided into 4 groups: 1) transport within one phase, where the processes are chiefly electromagnetic separations and thermodiffusion, 2) transfer between two phases, where distillation is the chief process, 3) transfer between two condensed phases concerns isothermal techniques, and 4) transfer between condensed phases by polythermal techniques. (U.K.)

  10. Collisional electron-capture processes at sodium halide surfaces

    International Nuclear Information System (INIS)

    A new class of inelastic collisional excitation processes accounts for the electron spectra of ion bombarded sodium halide surfaces. These spectra indicate that the excitation-deexcitation process consists of a sequence of lattice-ion collisions in which localized electron transfer occurs. Such collisional processes demonstrate how collisions can initiate electronic change in molecular compounds and that electron-transfer processes must play an essential role in chemistry activated by energetic collisions

  11. Reflection holographic optical elements in silver-halide sensitized gelatin

    OpenAIRE

    Pascual Villalobos, Inmaculada; Beléndez Vázquez, Augusto; Fimia Gil, Antonio

    1991-01-01

    Silver halide sensitized gelatin has proven to be an alternative to dichromated gelatin as a recording material in the production of transmission holographic optical elements (HOEs). In this paper we discuss the possible applications of this process to the production of reflection HOEs as well as the possible use of one of them in the construction of a hybrid refraction- diffraction system that could be used to copy transmission HOEs using partially coherent light.

  12. Organometal halide perovskites as useful materials in sensitized solar cells.

    Science.gov (United States)

    Singh, Surya Prakash; Nagarjuna, P

    2014-04-14

    Organometal halide perovskites offer dual potential properties as a light harvester and at the same time as a hole conductor in inorganic-organic hybrid heterojunction solar cells. The sequential deposition route provides a power conversion efficiency of 15% under standard AM1.5G test conditions. In this perspective, we will briefly summarize the development of perovskite-sensitized solar cells from their first report up to the present. PMID:24577264

  13. Separation parameters in the reaction between volatile halides and hydrogen

    International Nuclear Information System (INIS)

    Equations for calculating the separation coefficient and factor in reactions of volatile halides of group III-VI metals (M=B, Zr, Hf, V, Nb, Ta, Mo) with hydrogen from the equilibrium constants of the corresponding reactions and initial reactant concentrations were obtained. The concept of the limiting impurity concentration was introduced. The values specified were calculated for the reduction of volatile chlorides with hydrogen

  14. Influence of the Print Run on Silver Halide Printing Plates

    Directory of Open Access Journals (Sweden)

    Tomislav Cigula

    2010-09-01

    Full Text Available The most common printing technique today is lithography. The difference between printing and nonprinting areason a printing plate is accomplished by opposite physical and chemical properties of those areas (MacPhee, 1998.The printing areas are made of photoactive layer that attracts oil and chemical substances with oil solvent – printinginks. The nonprinting areas are made of aluminium-oxide which attracts water based substances – the fountainsolution.There are many of various types of photoactive layer which are used for production of offset printing plates, amongothers is silver halide layer. The usage of the silver halide technology in the graphic reproduction is not a novelty.The filmmaking phase is based on the usage of the silver halide as the photographically active ingredient, for instance,AgBr (silver bromide. The new, digital plate making technology (Computer to Plate, CtP eliminates thefilmmaking phase and therefore enables control of the printing plate’s exposure made by computer. CtP technologyeliminates the filmmaking phase, but it also results with the reduction of needed material quantities and requiredtime for the production (Limburg, 1994; Seydel, 1996.In this paper the basis of the graphic reproduction by using the silver halide digital printing plates was described.The changes of the AgX copying layer and the surface of the aluminium base in the printing process have beenobserved. The surface characteristics were determined by measuring the relevant surface roughness parameters. Inaddition, measurements of coverage values on the prints, detailed at smaller print run, were conducted.Results showed that surface changes on the printing plate are changing during printing process and that thesechanges influence transfer of the printing ink on the printing substrate. These measurements proved to be of greatinterest in the graphic reproduction as they enable us to determine consistency of the printing plates during theprinting process, to predict the endurance as well as to define the print run which will result with optimal qualityprints.

  15. Molybdenum bis(?-cyclopentadienyl) dihydride complexes with transition metal halides

    International Nuclear Information System (INIS)

    Stable complexes of molybdenum bis (eta-cyclopentadienyl) dihydride with copper, silver, zinc, mercury, iron, cobalt halides are prepared. The analysis of IR spectra of the compounds permits to make a conclusion on the participation of hydrogen hydride atoms of Cp2MoH2 in the formation of the bond with transition metal atom. A possible similarity in the structure of the complexes prepared and the active centre of nitrogenase ferment is discussed

  16. Characterization of Catalytically Active Octahedral Metal Halide Cluster Complexes

    Directory of Open Access Journals (Sweden)

    Satoshi Kamiguchi

    2014-04-01

    Full Text Available Halide clusters have not been used as catalysts. Hexanuclear molecular halide clusters of niobium, tantalum, molybdenum, and tungsten possessing an octahedral metal framework are chosen as catalyst precursors. The prepared clusters have no metal–metal multiple bonds or coordinatively unsaturated sites and therefore required activation. In a hydrogen or helium stream, the clusters are treated at increasingly higher temperatures. Above 150–250 °C, catalytically active sites develop, and the cluster framework is retained up to 350–450 °C. One of the active sites is a Brønsted acid resulting from a hydroxo ligand that is produced by the elimination of hydrogen halide from the halogen and aqua ligands. The other active site is a coordinatively unsaturated metal, which can be isoelectronic with the platinum group metals by taking two or more electrons from the halogen ligands. In the case of the rhenium chloride cluster Re3Cl9, the cluster framework is stable at least up to 300 °C under inert atmosphere; however, it is reduced to metallic rhenium at 250–300 °C under hydrogen. The activated clusters are characterized by X-ray diffraction analyses, Raman spectrometry, extended X-ray absorption fine structure analysis, thermogravimetry–differential thermal analysis, infrared spectrometry, acid titration with Hammett indicators, and elemental analyses.

  17. Photoexcitation, -ionization and fragmentation of molecular rubidium halides

    International Nuclear Information System (INIS)

    Full text: Photoionization and fragmentation of molecular rubidium halides following photoexcitation in the vacuum ultraviolet region are investigated. The experiments were performed at beamline 52 at MAX-I storage ring (Lund, Sweden) using Wiley- McLaren type time-of-flight mass spectrometer. Ion time-of-flight spectra, total and partial ion yield spectra are measured from the vapours of RbF, RbCl, RbBr and RbI, containing both the monomer and dimer molecules. From the partial ion yield spectra of the Rb+ covering the 8-18 eV photon energy range, a number of resonating excited states are identified. In the same spectral region similar resonances were observable in the case of Br+ and I+ partial ion yield spectra, but not in the case of F+ and Cl+ partial ion yield spectra. The fragmentation patterns of the excited and ionized rubidium halide molecules RbX and also the Rb2X2 dimers are studied in detail from ion time-of-flight mass spectra recorded at and around the resonances. Molecular dissociation following the resonant excitation is discussed and the different fragmentation of rubidium halide molecules is explained with two different electronic decay channels

  18. Colloidal nanocrystals with inorganic halide, pseudohalide, and halometallate ligands.

    Science.gov (United States)

    Zhang, Hao; Jang, Jaeyoung; Liu, Wenyong; Talapin, Dmitri V

    2014-07-22

    We investigate simple halides and pseudohalides as an important class of inorganic ligands for nanocrystals (NCs) in solution phase ligand exchange. These short, robust, and easy to model ligands bind to the NC surface and provide electrostatic stabilization of NC dispersions in N-methylformamide. The replacement of organic ligands on NCs with compact halide and pseudohalide ligands greatly facilitates electronic communication between NCs. For example, a high electron mobility of ? ? 12 cm(2) V(-1) s(-1) has been observed in thin films made of I(-)-capped CdSe NCs. We also studied charge transport properties of thin films based on the pseudohalide N3(-)-capped InAs NCs, suggesting the possibility of obtaining "all III-V" NC solids. In addition, we extend the surface chemistry of halometallates (e.g., CH3NH3PbI3), which can stabilize colloidal solutions of lead chalcogenide NCs. These halide, pseudohalide, and halometallate ligands enrich the current family of inorganic ligands and can open up more opportunities for applications of NCs in the fields of electronics, optoelectronics, and thermoelectrics. PMID:24988140

  19. Infrared Spectra of Simple Inorganic Ion Pairs in Solid Solution: A Physical Inorganic Chemistry Experiment.

    Science.gov (United States)

    Miller, Philip J.; Tong, William G.

    1980-01-01

    Presents a physical inorganic experiment in which large single crystals of the alkali halides doped with divalent ion impurities are prepared easily. Demonstrates the ion pairing of inorganic ions in solid solution. (CS)

  20. The etching process of boron nitride by alkali and alkaline earth fluorides under high pressure and high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Guo, W., E-mail: guowei1982cry@163.com [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Ma, H.A.; Jia, X. [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China)

    2014-03-01

    Graphical abstract: - Highlights: • Appropriate etch processes of hBN and cBN under HPHT are proposed. • The degree of the crystallization of hBN was decreased. • A special cBN growth mechanism with a triangular unit is proposed. • Plate-shape cBN crystals with large ratio of length to thickness were obtained. • A strategy provides useful guidance for controlling the cBN morphology. - Abstract: Some new etching processes of hexagonal boron nitride (hBN) and cubic boron nitride (cBN) under high pressure and high temperature in the presence of alkali and alkaline earth fluorides have been discussed. It is found that hBN is etched distinctly by alkali and alkaline earth fluorides and the morphology of hBN is significantly changed from plate-shape to spherical-shape. Based on the “graphitization index” values of hBN, the degree of the crystallization of hBN under high pressure and high temperature decreases in the sequence of LiF > CaF{sub 2} > MgF{sub 2}. This facilitates the formation of high-quality cBN single crystals. Different etch steps, pits, and islands are observed on cBN surface, showing the strong etching by alkali and alkaline earth fluorides and the tendency of layer-by-layer growth. A special layer growth mechanism of cBN with a triangular unit has been found. Furthermore, the morphologies of cBN crystals are apparently affected by a preferential surface etching of LiF, CaF{sub 2} and MgF{sub 2}. Respectively, the plate-shape and tetrahedral cBN crystals can be obtained in the presence of different alkali and alkaline earth fluorides.

  1. The etching process of boron nitride by alkali and alkaline earth fluorides under high pressure and high temperature

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Appropriate etch processes of hBN and cBN under HPHT are proposed. • The degree of the crystallization of hBN was decreased. • A special cBN growth mechanism with a triangular unit is proposed. • Plate-shape cBN crystals with large ratio of length to thickness were obtained. • A strategy provides useful guidance for controlling the cBN morphology. - Abstract: Some new etching processes of hexagonal boron nitride (hBN) and cubic boron nitride (cBN) under high pressure and high temperature in the presence of alkali and alkaline earth fluorides have been discussed. It is found that hBN is etched distinctly by alkali and alkaline earth fluorides and the morphology of hBN is significantly changed from plate-shape to spherical-shape. Based on the “graphitization index” values of hBN, the degree of the crystallization of hBN under high pressure and high temperature decreases in the sequence of LiF > CaF2 > MgF2. This facilitates the formation of high-quality cBN single crystals. Different etch steps, pits, and islands are observed on cBN surface, showing the strong etching by alkali and alkaline earth fluorides and the tendency of layer-by-layer growth. A special layer growth mechanism of cBN with a triangular unit has been found. Furthermore, the morphologies of cBN crystals are apparently affected by a preferential surface etching of LiF, CaF2 and MgF2. Respectively, the plate-shape and tetrahedral cBN crystals can be obtained in the presence of different alkali and alkaline earth fluorides

  2. Ultrasmooth organic-inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells.

    Science.gov (United States)

    Zhang, Wei; Saliba, Michael; Moore, David T; Pathak, Sandeep K; Hörantner, Maximilian T; Stergiopoulos, Thomas; Stranks, Samuel D; Eperon, Giles E; Alexander-Webber, Jack A; Abate, Antonio; Sadhanala, Aditya; Yao, Shuhua; Chen, Yulin; Friend, Richard H; Estroff, Lara A; Wiesner, Ulrich; Snaith, Henry J

    2015-01-01

    To date, there have been a plethora of reports on different means to fabricate organic-inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry. PMID:25635571

  3. Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells

    Science.gov (United States)

    Zhang, Wei; Saliba, Michael; Moore, David T.; Pathak, Sandeep K.; Hörantner, Maximilian T.; Stergiopoulos, Thomas; Stranks, Samuel D.; Eperon, Giles E.; Alexander-Webber, Jack A.; Abate, Antonio; Sadhanala, Aditya; Yao, Shuhua; Chen, Yulin; Friend, Richard H.; Estroff, Lara A.; Wiesner, Ulrich; Snaith, Henry J.

    2015-01-01

    To date, there have been a plethora of reports on different means to fabricate organic–inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.

  4. Alkali resistant optical coatings for alkali lasers and methods of production thereof

    Science.gov (United States)

    Soules, Thomas F; Beach, Raymond J; Mitchell, Scott C

    2014-11-18

    In one embodiment, a multilayer dielectric coating for use in an alkali laser includes two or more alternating layers of high and low refractive index materials, wherein an innermost layer includes a thicker, >500 nm, and dense, >97% of theoretical, layer of at least one of: alumina, zirconia, and hafnia for protecting subsequent layers of the two or more alternating layers of high and low index dielectric materials from alkali attack. In another embodiment, a method for forming an alkali resistant coating includes forming a first oxide material above a substrate and forming a second oxide material above the first oxide material to form a multilayer dielectric coating, wherein the second oxide material is on a side of the multilayer dielectric coating for contacting an alkali.

  5. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    International Nuclear Information System (INIS)

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF3:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to 137Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF3:Ce-loaded sample have been made using 137Cs sources. Figure 2 shows an energy spectrum acquired for CeF3. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr3 crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% 138La component of lanthanum leads to significant self-activity, which will be a problem for very large detector volumes. Yet a significant strength of the nanostructure detector concept is the ability to create extremely large detector volumes by mixing nanoparticles into a transparent matrix. This would argue for use of nanoparticles other than lanthanum halides. Nanocomposites are easy to prepare; it is much less costly to use nanocomposites than to grow large whole crystals of these materials. The material can be fabricated at an industrial scale, further reducing cost. This material potentially offers the performance of $300/cc material (e.g., lanthanum bromide) at a cost of $1/cc. Because the material acts as a plastic, it is rugged and flexible, and can be made in large sheets, increasing the sensitivity of a detector using it. It would operate at ambient temperatures. Very large volumes of detector may be produced at greatly reduced cost, enhancing the non-proliferation posture of the nation for the same dollar value.

  6. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    Energy Technology Data Exchange (ETDEWEB)

    Paul Guss, Sanjoy Mukhopadhyay, Ron Guise, Ding Yuan

    2010-06-09

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF{sub 3}:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to {sup 137}Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF{sub 3}:Ce-loaded sample have been made using {sup 137}Cs sources. Figure 2 shows an energy spectrum acquired for CeF{sub 3}. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr{sub 3} crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% {sup 138}La component of lanthanum leads to significant self-activity, which will be a problem for very large detector volumes. Yet a significant strength of the nanostructure detector concept is the ability to create extremely large detector volumes by mixing nanoparticles into a transparent matrix. This would argue for use of nanoparticles other than lanthanum halides. Nanocomposites are easy to prepare; it is much less costly to use nanocomposites than to grow large whole crystals of these materials. The material can be fabricated at an industrial scale, further reducing cost. This material potentially offers the performance of $300/cc material (e.g., lanthanum bromide) at a cost of $1/cc. Because the material acts as a plastic, it is rugged and flexible, and can be made in large sheets, increasing the sensitivity of a detector using it. It would operate at ambient temperatures. Very large volumes of detector may be produced at greatly reduced cost, enhancing the non-proliferation posture of the nation for the same dollar value.

  7. The origin of halide melt phases in layered intrusions, and their significance to platinum-group element mobility

    Science.gov (United States)

    Hanley, J. J.

    2007-12-01

    Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles became increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids, and the partitioning behavior of Cl in fluid-melt systems. Previously unreported, the latest stage volatiles in the layered intrusions were halide melts (slightly hydrous molten salts) of relatively simply composition (NaCl with minor KCl or CaCl2) with salinities in excess of 90 wt% eq. NaCl or CaCl2. These volatiles were trapped at minimum temperatures of 760-800°C, near the eutectic temperature for water-saturated granitic liquid at moderate crustal pressures. Trace element analysis of the salt melt inclusions by laser ablation ICP-MS (ETH Zürich) show that they contain no detectable concentrations of ore and accessory metals. This is in contrast to the earlier, lower salinity volatiles which contain ppm-concentrations of Pt, Pd, As, Bi, Sb as well as abundant S and base metals. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic or felsic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H2O ratios for the parental silicate liquid (> 9 for a granitic residue). Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show that the coeval silicate melts had Cl:H2O ratios of only 0.1 to 0.2. Similarily, the salt melt phases could not have evolved via the removal of H2O by crystallization of hydrous magmatic minerals (e.g., biotite, apatite) since their modal abundances in the intrusions are very low. The most plausible explanation for the halide melt phases involves the "dehydration" of an initially lower- salinity aqueous fluid. This may have occurred by the reaction of the aqueous fluid with nominally-anhydrous minerals such as pyroxene, or by the late-stage alteration of cumulus minerals to hydrous mineral assemblages. Through the use of conventional hydrothermal experimental techniques, it can be shown that the reaction of a volumetrically-minor CaCl2-rich aqueous fluid phase (20 wt% eq. CaCl2) with the assemblage diopside-enstatite-quartz at near-solidus conditions (700°C, 0.4 kbar) results in the formation of tremolite by the reaction of H2O with the initially anhydrous mafic mineral assemblage. The resulting salinity of the dehydrated saline phase, trapped as synthetic inclusions in quartz, was > 96 wt% eq. CaCl2, consistent with the water-poor nature of the salt melt inclusions from the intrusions. The results of this study indicate that, through the loss of H2O, metal-bearing aqueous volatiles in layered intrusions may precipitate metals as they are dehydrated to form salt melt phases. Metal precipitation may occur as amount of free H2O in the volatile phase necessary to hydrate metal complexes decreases. This precipitation mechanism challenges the conventional magmatic hypothesis for platinum-group element deposit formation in layered intrusions.

  8. Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

    OpenAIRE

    Lammert, Heiko; Heuer, Andreas

    2005-01-01

    The mixed-alkali effect on the cation dynamics in silicate glasses is analyzed via molecular dynamics simulations. Observations suggest a description of the dynamics in terms of stable sites mostly specific to one ionic species. As main contributions to the mixed--alkali slowdown longer residence times and an increased probability of correlated backjumps are identified. The slowdown is related to the limited accessibility of foreign sites. The mismatch experienced in a forei...

  9. The source for polarized alkali ions

    International Nuclear Information System (INIS)

    The source for polarized heavy ions (PSI) has been used to produce polarized beams of 23Na for several runs. The method of polarizing an alkali atomic beam by optical pumping with an electrooptic modulated laser was used in all experiments and turned out to be very effective and reliable. (orig.)

  10. Masses and radii of alkali nuclei

    International Nuclear Information System (INIS)

    The various nuclear information concerning alkali isotopes which have been obtained either by on-line mass spectrometry or by on-line laser spectroscopy are reviewed. Mass spectrometry provided mass-determinations while laser spectroscopy provided values of I, ?, Qsub(s) and delta2>. The masses and the variations of the mean square charge radii are presented and briefly discussed. (orig.)

  11. S/N heterostructure of BiSrCaCuO/BiSrCuO grown by halide CVD

    International Nuclear Information System (INIS)

    Thin film S/N heterostructures of superconducting BiSrCaCuO and metallic BiSrCuO with a good surface morphology, crystallinity, and superconducting properties were formed on (100) MgO substrates by halide CVD. Critical temperatures (zero resistance at Tc) and critical current densities (Jc) of the BiSrCaCuO films on MgO substrate were Tc=75 to 80 K and Jc=1x106A/cm2 at 60 K. Electrical resistance of the metallic BiSrCuO films was 1 to 2 x10-3 ohm-cm from 10 to 300 K. High resolution transmission electron microscopy (HRTEM) images showed the interface between the BiSrCaCuO and BiSrCuO films to be atomically very abrupt. The critical temperatures of S/N-multilayer samples was about 75K. In this work, we fabricated S/N-heterostructures of bismuth-compound crystals grown by halide CVD and studied the film quality and superconducting properties. (orig.)

  12. Involvement of S-adenosylmethionine-dependent halide/thiol methyltransferase (HTMT) in methyl halide emissions from agricultural plants: isolation and characterization of an HTMT-coding gene from Raphanus sativus (daikon radish)

    OpenAIRE

    Taniguchi Tomokazu; Negishi Takashi; Matsuda Michiko; Toda Hiroshi; Itoh Nobuya; Ohsawa Noboru

    2009-01-01

    Abstract Background Biogenic emissions of methyl halides (CH3Cl, CH3Br and CH3I) are the major source of these compounds in the atmosphere; however, there are few reports about the halide profiles and strengths of these emissions. Halide ion methyltransferase (HMT) and halide/thiol methyltransferase (HTMT) enzymes concerning these emissions have been purified and characterized from several organisms including marine algae, fungi, and higher plants; however, the correlation between emission pr...

  13. 10 CFR 431.324 - Uniform test method for the measurement of energy efficiency of metal halide ballasts.

    Science.gov (United States)

    2010-01-01

    ...method for the measurement of energy efficiency of metal halide ballasts...ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL...method for the measurement of energy efficiency of metal halide ballasts....

  14. Alkali element background reduction in laser ICP-MS

    Science.gov (United States)

    Magee, C. W., Jr.; Norris, C. A.

    2015-03-01

    Alkali backgrounds in laser ablation ICP-MS analyses can be enhanced by electron-induced ionisation of alkali contamination on the skimmer cone, reducing effective detection limits for these elements. Traditionally, this problem is addressed by isolating analyses of high-alkali materials onto a designated cone set, or by operating the ICP-MS in a "soft extraction" mode, which reduces the energy of electrons repelled into the potentially contaminated sampling cone by the extraction field. Here we present a novel approach, where we replace the traditional alkali glass tuning standards with synthetic low-alkali glass reference materials. Using this vitreous tuning solution, we find that this approach reduces the amount of alkali contamination produced, halving backgrounds for the heavy alkali elements without any change to analytical procedures. Using segregated cones is still the most effective method for reducing lithium backgrounds, but since the procedures are complimentary, both can easily be applied to the routine operations of an analytical lab.

  15. Crystallization In High Level Waste (HLW) Glass Melters: Operational Experience From The Savannah River Site

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K. M.

    2014-02-27

    processing strategy for the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The basis of this alternative approach is an empirical model predicting the crystal accumulation in the WTP glass discharge riser and melter bottom as a function of glass composition, time, and temperature. When coupled with an associated operating limit (e.g., the maximum tolerable thickness of an accumulated layer of crystals), this model could then be integrated into the process control algorithms to formulate crystal tolerant high level waste (HLW) glasses targeting higher waste loadings while still meeting process related limits and melter lifetime expectancies. This report provides a review of the scaled melter testing that was completed in support of the Defense Waste Processing Facility (DWPF) melter. Testing with scaled melters provided the data to define the DWPF operating limits to avoid bulk (volume) crystallization in the un-agitated DWPF melter and provided the data to distinguish between spinels generated by K-3 refractory corrosion versus spinels that precipitated from the HLW glass melt pool. This report includes a review of the crystallization observed with the scaled melters and the full scale DWPF melters (DWPF Melter 1 and DWPF Melter 2). Examples of actual DWPF melter attainment with Melter 2 are given. The intent is to provide an overview of lessons learned, including some example data, that can be used to advance the development and implementation of an empirical model and operating limit for crystal accumulation for WTP. Operation of the first and second (current) DWPF melters has demonstrated that the strategy of using a liquidus temperature predictive model combined with a 100 °C offset from the normal melter operating temperature of 1150 °C (i.e., the predicted liquidus temperature (TL) of the glass must be 1050 °C or less) has been successful in preventing any detrimental accumulation of spinel in the DWPF melt pool, and spinel has not been observed in any of the pour stream glass samples. Spinel was observed at the bottom of DWPF Melter 1 as a result of K-3 refractory corrosion. Issues have occurred with accumulation of spinel in the pour spout during periods of operation at higher waste loadings. Given that both DWPF melters were or have been in operation for greater than 8 years, the service life of the melters has far exceeded design expectations. It is possible that the DWPF liquidus temperature approach is conservative, in that it may be possible to successfully operate the melter with a small degree of allowable crystallization in the glass. This could be a viable approach to increasing waste loading in the glass assuming that the crystals are suspended in the melt and swept out through the riser and pour spout. Additional study is needed, and development work for WTP might be leveraged to support a different operating limit for the DWPF. Several recommendations are made regarding considerations that need to be included as part of the WTP crystal tolerant strategy based on the DWPF development work and operational data reviewed here. These include: Identify and consider the impacts of potential heat sinks in the WTP melter and glass pouring system; Consider the contributions of refractory corrosion products, which may serve to nucleate additional crystals leading to further accumulation; Consider volatilization of components from the melt (e.g., boron, alkali, halides, etc.) and determine their impacts on glass crystallization behavior; Evaluate the impacts of glass REDuction/OXidation (REDOX) conditions and the distribution of temperature within the WTP melt pool and melter pour chamber on crystal accumulation rate; Consider the impact of precipitated crystals on glass viscosity; Consider the impact of an accumulated crystalline layer on thermal convection currents and bubbler effectiveness within the melt pool; Evaluate the impact of spinel accumulation on Joule heating of the WTP melt pool; and Include noble metals in glass melt experiments because of their potential to act as nucleation site

  16. Crystallization In High Level Waste (HLW) Glass Melters: Operational Experience From The Savannah River Site

    International Nuclear Information System (INIS)

    processing strategy for the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The basis of this alternative approach is an empirical model predicting the crystal accumulation in the WTP glass discharge riser and melter bottom as a function of glass composition, time, and temperature. When coupled with an associated operating limit (e.g., the maximum tolerable thickness of an accumulated layer of crystals), this model could then be integrated into the process control algorithms to formulate crystal tolerant high level waste (HLW) glasses targeting higher waste loadings while still meeting process related limits and melter lifetime expectancies. This report provides a review of the scaled melter testing that was completed in support of the Defense Waste Processing Facility (DWPF) melter. Testing with scaled melters provided the data to define the DWPF operating limits to avoid bulk (volume) crystallization in the un-agitated DWPF melter and provided the data to distinguish between spinels generated by K-3 refractory corrosion versus spinels that precipitated from the HLW glass melt pool. This report includes a review of the crystallization observed with the scaled melters and the full scale DWPF melters (DWPF Melter 1 and DWPF Melter 2). Examples of actual DWPF melter attainment with Melter 2 are given. The intent is to provide an overview of lessons learned, including some example data, that can be used to advance the development and implementation of an empirical model and operating limit for crystal accumulation for WTP. Operation of the first and second (current) DWPF melters has demonstrated that the strategy of using a liquidus temperature predictive model combined with a 100 °C offset from the normal melter operating temperature of 1150 °C (i.e., the predicted liquidus temperature (TL) of the glass must be 1050 °C or less) has been successful in preventing any detrimental accumulation of spinel in the DWPF melt pool, and spinel has not been observed in any of the pour stream glass samples. Spinel was observed at the bottom of DWPF Melter 1 as a result of K-3 refractory corrosion. Issues have occurred with accumulation of spinel in the pour spout during periods of operation at higher waste loadings. Given that both DWPF melters were or have been in operation for greater than 8 years, the service life of the melters has far exceeded design expectations. It is possible that the DWPF liquidus temperature approach is conservative, in that it may be possible to successfully operate the melter with a small degree of allowable crystallization in the glass. This could be a viable approach to increasing waste loading in the glass assuming that the crystals are suspended in the melt and swept out through the riser and pour spout. Additional study is needed, and development work for WTP might be leveraged to support a different operating limit for the DWPF. Several recommendations are made regarding considerations that need to be included as part of the WTP crystal tolerant strategy based on the DWPF development work and operational data reviewed here. These include: Identify and consider the impacts of potential heat sinks in the WTP melter and glass pouring system; Consider the contributions of refractory corrosion products, which may serve to nucleate additional crystals leading to further accumulation; Consider volatilization of components from the melt (e.g., boron, alkali, halides, etc.) and determine their impacts on glass crystallization behavior; Evaluate the impacts of glass REDuction/OXidation (REDOX) conditions and the distribution of temperature within the WTP melt pool and melter pour chamber on crystal accumulation rate; Consider the impact of precipitated crystals on glass viscosity; Consider the impact of an accumulated crystalline layer on thermal convection currents and bubbler effectiveness within the melt pool; Evaluate the impact of spinel accumulation on Joule heating of the WTP melt pool; and Include noble metals in glass melt experiments because of their potential to act as nucleation site

  17. Radioluminescence of synthetic quartz related to alkali ions

    Energy Technology Data Exchange (ETDEWEB)

    Martini, M., E-mail: m.martini@unimib.it [Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); INFN-Sezione di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Fasoli, M. [Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Galli, A. [Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Istituto di Fotonica e Nanostrutture, IFN-CNR (Italy); Villa, I. [Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Guibert, P. [IRAMAT-CRP2A (Institut de recherche sur les Archeomateriaux), UMR no. 5060, CNRS-Universite Bordeaux III, F-33607 Pessac (France)

    2012-04-15

    The radioluminescence (RL) of synthetic quartzes (GEMMA Quartz and Crystal Company) has been measured at room temperature. Some samples were treated by electrodiffusion ('sweeping') in order to change the concentrations of alkali ions, mainly Li{sup +} and Na{sup +}, which in quartz are known to be linked to Al ions, substitutional for Si ions. The RL emission spectra show evidence of a role of alkali ions in affecting some specific emissions. All the spectra could be analysed as composed of four bands in the blue and UV region. Specifically, the well known blue emission at around 470 nm was seen to be composed by two bands at 430 nm (2.86 eV) and at 485 nm (2.53 eV). Effects of irradiation, during the RL measurements, were clearly seen only in the 'Li swept in' sample, namely an increase in the 485 nm band intensity and a decrease in the 430 nm band one. The previously reported UV emission was detected at 355 nm (3.44 eV) in all the samples, being the most intense band in the 'swept out' sample. A further UV emission was detected at 315 nm (3.94 eV), more intense in untreated samples. Possible assignments of the detected emission bands are discussed in relation to the defects of quartz, specifically focusing on the Al centres that are most affected by sweeping procedures. - Highlights: Black-Right-Pointing-Pointer Contribution to the understanding of relationships between defects in quartz and luminescence emissions. Black-Right-Pointing-Pointer Role of charge compensators at substitutional Al sites in the optical properties of quartz. Black-Right-Pointing-Pointer Evidence of the double nature of the 'blue emission' (around 470 nm).

  18. A study of the influence of slag alkali level on the alkali-silica reactivity of slag concrete

    OpenAIRE

    Hester, David; McNally, Ciaran; Richardson, Mark G.

    2005-01-01

    Ground granulated blast furnace slag (ggbs), can reduce the alkali load in concrete, despite its relatively high alkali content. Most research has been devoted to the efficacy of slag with an alkali content of less than 1.0% and this is reflected in guidance documents. A comparative assessment was made of the effect, if any, of the alkali level of ggbs on potential alkali-silica reactivity. Expansion tests were performed on a matrix of concrete mixes using Irish normal Portland cement, two sl...

  19. Quadrupolar deformation of the electronic charge cloud and the lattice mechanics of LiH-LiD crystals

    International Nuclear Information System (INIS)

    As the deformable shell model incorporates both scalar and dipolar deformation, it is natural to expect that the quadrupolar deformation may be important in the case of lithium hydride, where the unstable hydrogen ion with its extremely loose bound outermost electron (compared to alkali halides) appears to be a plausible candidate for such deformation. Quadrupolar deformation in an ion in crystal may arise because of the variation of the electric field produced by o,.her ions over the extent of the charge cloud or due to a shortrange overlap effect of nearest neighbours. The second effect is much stronger than the first and this alone is considered in the present investigation. A method has been developed to obtain the relevant equations and evaluate all the lattice sums appropriate for the structure on the basis of an extended deformable shell model which incorporates scalar, dipolar and quadrupolar deformation. The quadrupolar deformation is found to have quite a considerable effect both on the dynamic and static properties of LiH-LiD crystals. The resulting model not only removes the discrepancies mentioned above but has also been successful in correlating the specific properties namely, the static lattice structure, the cohesive energy, the second order elastic constants, the dielectric properties and the lattice dynamics with a single set of parameters used for all of them. Only the shortrange overlap effect of the nearest neighbours has been taken into account at neighbours has been taken into account and not that due to the variation of the electric field produced by other ions over the extent of charge cloud, since the former effect is much stronger than the latter one. (K.B.)

  20. Structural and chemical aspects of complex formation in the metal halide-macrocyclic polyether systems

    International Nuclear Information System (INIS)

    Structural data for more than two hundred complexes of oxygen-containing crown ethers with the period 2-6 element halides, as well as uranium and thorium halides are reviewed. The main types of complexes are distinguished. The characteristic features of the formation of complexes and coordination fragments are discussed

  1. Metal-halide lamp design: atomic and molecular data needed

    Energy Technology Data Exchange (ETDEWEB)

    Lapatovich, Walter P [OSRAM SYLVANIA, Central Research and Services Laboratory, 71 Cherry Hill Drive, Beverly, MA 01921 (United States)], E-mail: walter.lapatovich@sylvania.com

    2009-05-15

    Metal-halide lamps are a subset of high intensity discharge (HID) lamps so named because of their high radiance. These lamps are low temperature ({approx}0.5 eV), weakly ionized plasmas sustained in refractory but light transmissive envelopes by the passage of electric current through atomic and molecular vapors. For commercial applications, the conversion of electric power to light must occur with good efficiency and with sufficient spectral content throughout the visible (380-780 nm) to permit the light so generated to render colors comparable to natural sunlight. This is achieved by adding multiple metals to a basic mercury discharge. Because the vapor pressure of most metals is very much lower than mercury itself, metal-halide salts of the desired metals, having higher vapor pressures, are used to introduce the material into the basic discharge. The metal compounds are usually polyatomic iodides, which vaporize and subsequently dissociate as they diffuse into the bulk plasma. Metals with multiple visible transitions are necessary to achieve high photometric efficiency (efficacy) and good color. Compounds of Sc, Dy, Ho, Tm, Ce, Pr, Yb and Nd are commonly used. The electrons, atoms and radicals are in local thermodynamic equilibrium (LTE), but not with the radiation field. Strong thermal (10{sup 6} K m{sup -1}) and density gradients are sustained in the discharge. Atomic radiation produced in the high-temperature core transits through colder gas regions where it interacts with cold atoms and un-dissociated molecules before exiting the lamp. Power balance and spectral output of the lamp are directly affected by the strength of atomic transitions. Attempts to simulate the radiative output of functional metal-halide lamps have been successful only in very simple cases. More data (e.g. the atomic transition probabilities of Ce i) are necessary to improve lamp performance, to select appropriate radiators and in scaling the lamp geometry to various wattages for specific applications.

  2. Effect of chromone-substituted benzothiazolium halides on photosynthetic processes

    International Nuclear Information System (INIS)

    The effects of 3-R2-2[2-(6-R1-chromone-3-yl)ethenyl]benzothiazolium halides (CBH) on photosynthetic electron transport in spinach chloroplasts and in the legal suspension of Chlorella vulgaris were investigated. Using EPR spectroscopy it was confirmed that these compounds containing in their molecules two heterocyclic skeletons, namely benzothiazole and chromone, interact with the intermediate D+, corresponding to the tyrosine radical TyrD situated in D2 protein on the donor side of photosystem 2. Consequently, higher concentrations of CBH inhibited oxygen evolution rate in Chlorella vulgaris and the inhibitory effectiveness depended on the lipophilicity of the of the compound. (authors)

  3. Thermal conductivity of halide solid solutions: measurement and prediction.

    Science.gov (United States)

    Gheribi, Aïmen E; Poncsák, Sándor; St-Pierre, Rémi; Kiss, László I; Chartrand, Patrice

    2014-09-14

    The composition dependence of the lattice thermal conductivity in NaCl-KCl solid solutions has been measured as a function of composition and temperature. Samples with systematically varied compositions were prepared and the laser flash technique was used to determine the thermal diffusivity from 373 K to 823 K. A theoretical model, based on the Debye approximation of phonon density of state (which contains no adjustable parameters) was used to predict the thermal conductivity of both stoichiometric compounds and fully disordered solid solutions. The predictions obtained with the model agree very well with our measurement. A general method for predicting the thermal conductivity of different halide systems is discussed. PMID:25217938

  4. Chemistry and superconductivity of intercalated metal nitride halides

    Science.gov (United States)

    Fuertes, Amparo

    2014-06-01

    Titanium, zirconium and hafnium nitride halides show layered structures based on double slabs with compositions [X-M-N-N-M-X] (X = Cl, Br or I; M = Ti, Zr or Hf) that are separated by van der Waals gaps. Intercalation of electron donor species between the double layers induces superconductivity with critical temperatures up to 25.5 K. This review discusses the synthesis and structural chemistry of the hosts and intercalation compounds in this group of materials, as well as the influence of the structural and chemical features of the intercalates on the superconducting properties.

  5. Geopolymers and Related Alkali-Activated Materials

    Science.gov (United States)

    Provis, John L.; Bernal, Susan A.

    2014-07-01

    The development of new, sustainable, low-CO2 construction materials is essential if the global construction industry is to reduce the environmental footprint of its activities, which is incurred particularly through the production of Portland cement. One type of non-Portland cement that is attracting particular attention is based on alkali-aluminosilicate chemistry, including the class of binders that have become known as geopolymers. These materials offer technical properties comparable to those of Portland cement, but with a much lower CO2 footprint and with the potential for performance advantages over traditional cements in certain niche applications. This review discusses the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials, in particular initial setting and long-term durability. Perspectives for future research developments are also explored.

  6. Removal of Retired Alkali Metal Test Systems

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Decalcification resistance of alkali-activated slag

    International Nuclear Information System (INIS)

    Highlights: ? The effects of decalcification on properties of alkali-activated slag were studied. ? Decalcification was performed by concentrated NH4NO3 solution (accelerated test). ? Portland-slag cement (CEM II/A-S 42.5 N) was used as a benchmark material. ? Decalcification led to strength decrease and noticeable structural changes. ? Alkali-activated slag showed significantly higher resistance to decalcification. - Abstract: This paper analyses the effects of decalcification in concentrated 6 M NH4NO3 solution on mechanical and microstructural properties of alkali-activated slag (AAS). Portland-slag cement (CEM II/A-S 42.5 N) was used as a benchmark material. Decalcification process led to a decrease in strength, both in AAS and in CEM II, and this effect was more pronounced in CEM II. The decrease in strength was explicitly related to the decrease in Ca/Si atomic ratio of C–S–H gel. A very low ratio of Ca/Si ?0.3 in AAS was the consequence of coexistence of C–S–H(I) gel and silica gel. During decalcification of AAS almost complete leaching of sodium and tetrahedral aluminum from C–S–H(I) gel also took place. AAS showed significantly higher resistance to decalcification in relation to the benchmark CEM II due to the absence of portlandite, high level of polymerization of silicate chains, low level of aluminum for silicon substitution in the structure of C–S–H(I), and the formation of protective of protective layer of polymerized silica gel during decalcification process. In stabilization/solidification processes alkali-activated slag represents a more promising solution than Portland-slag cement due to significantly higher resistance to decalcification.

  8. Microstructured hydroxyl environments and Raman spectroscopy in selected basic transition-metal halides

    International Nuclear Information System (INIS)

    Raman vibrational spectra of the selected basic (hydroxyl OH and deuteroxyl OD) transition-metal halides, geometrically frustrated material series ?-, ?-, ?-Cu2(OH)3Cl, ?-Cu2(OH)3Br, ?-Ni2(OH)3Cl, ?-Co2(OH)3Cl, ?-Co2(OH)3Br, ?-Cu2(OD)3Cl, and ?-Co2(OD)3Cl are measured at room temperature and analysed to investigate the relationship between the microstructured OH environments and their respective Raman spectra. Among these selected samples, the last two are used to determine the OH stretching vibration region (3600 cm?1?3300 cm?1) and OH bending vibration region (1000 cm?1?600 cm?1) of OH systems in the spectra. Through the comparative analysis of the distances d(metal—O), d(O—halogen), and d(OH), the strong metal—O interaction and trimeric hydrogen bond (C3v, Cs or C1 symmetry) are found in every material, but both determine simultaneously an ultimate d(OH), and therefore an OH stretching vibration frequency. According to the approximately linear relationship between the OH stretching vibration frequency and d(OH), some unavailable d(OH) are guessed and some doubtful d(OH) are suggested to be corrected. In addition, it is demonstrated in brief that the OH bending vibration frequency is also of importance to check the more detailed crystal microstructure relating to the OH group. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. Crystal chemistry of hydrogen storage materials

    OpenAIRE

    Jones, Mo; David, Wif; Johnson, Sr; Sommariva, M.; Lowton, Rl; Nickels, Ea; Edwards, Pp

    2008-01-01

    We review here work on two classes of compounds that have been promoted as potential hydrogen storage materials; alkali metal amides and borohydrides, highlighting how their crystal structure and chemical properties may be used to influence the key hydrogen absorption and desorption parameters in these materials. © 2008 Materials Research Society.

  10. Reactive flux syntheses, crystal structures and band gaps of AInS2 (A = Rb, Cs)

    International Nuclear Information System (INIS)

    High-quality single crystals of RbInS2, CsInS2 were isolated from the halide flux as a major phase of the repeated fusion of CaS and In2S3 followed by slow cooling. RbInS2 and CsInS2 are practically isostructural with KInS2. RbInS2: C2/c, a = 11.071(6) A, b = 11.068(1) A, c = 15.610(7) A, ? = 100.36(3)o, V = 1882(2) A3, Z = 16, d x = 3.74 g/cm3, R = 6.38%, R w = 6.42%. CsInS2: C2/c, a = 11.197(3) A, b = 11.158(3) A, c = 16.358(4) A, ? = 99.92(2)o, V = 2013(2) A3, Z = 16, d x = 4.12 g/cm3, R = 5.60%, R w = 6.20%. The AInS2 (A = Rb, Cs) structure is characterized by double layers of vertex-sharing [In4S10] units that each consists of four [InS4] polyhedra. The charge-balancing alkali-metal cations are stuffed into the channels created by the packing of these anionic [In4S10] blocks. The optical reflectance measurements show a band gap of 3.3 eV for RbInS2 and 3.4 eV for CsInS2, suggesting that both are semiconductors

  11. Halide salts accelerate degradation of high explosives by zerovalent iron

    International Nuclear Information System (INIS)

    Zerovalent iron (Fe0, ZVI) has drawn great interest as an inexpensive and effective material to promote the degradation of environmental contaminants. A focus of ZVI research is to increase degradation kinetics and overcome passivation for long-term remediation. Halide ions promote corrosion, which can increase and sustain ZVI reactivity. Adding chloride or bromide salts with Fe0 (1% w/v) greatly enhanced TNT, RDX, and HMX degradation rates in aqueous solution. Adding Cl or Br salts after 24 h also restored ZVI reactivity, resulting in complete degradation within 8 h. These observations may be attributed to removal of the passivating oxide layer and pitting corrosion of the iron. While the relative increase in degradation rate by Cl- and Br- was similar, TNT degraded faster than RDX and HMX. HMX was most difficult to remove using ZVI alone but ZVI remained effective after five HMX reseeding cycles when Br- was present in solution. - The addition of halide ions promotes the degradation of high explosives by zerovalent iron

  12. Thermodynamics of the vaporization of thorium and uranium halides

    International Nuclear Information System (INIS)

    The vaporization behaviour of thorium and uranium halides is being investigated in the solid and liquid regions by the boiling-temperature and transpiration techniques. The two techniques have been used for studies on ThCl4, UF4 and UCl4 over the temperature ranges 880 to 1161 K, 1169 to 1427 K, and 763 to 1008 K, respectively. The data derived from the two techniques agree excellently with each other for these three halides, thereby establishing their vaporization behaviour. Boiling-temperature studies have been completed for ThF4 , ThBr4, ThI4 and UBr4 over the temperature ranges 1395 to 1554 K, 842 to 1089 K, 790 to 1044 K, and 759 to 1004 K, respectively. In a number of cases, the present data are at variance with existing published data. The vapour pressure data were expressed as: log10p=A-BT-1 where p is in atmospheres and T in kelvin. The constants A and B for the vapour pressure equations are listed

  13. Sodium-metal halide and sodium-air batteries.

    Science.gov (United States)

    Ha, Seongmin; Kim, Jae-Kwang; Choi, Aram; Kim, Youngsik; Lee, Kyu Tae

    2014-07-21

    Impressive developments have been made in the past a few years toward the establishment of Na-ion batteries as next-generation energy-storage devices and replacements for Li-ion batteries. Na-based cells have attracted increasing attention owing to low production costs due to abundant sodium resources. However, applications of Na-ion batteries are limited to large-scale energy-storage systems because of their lower energy density compared to Li-ion batteries and their potential safety problems. Recently, Na-metal cells such as Na-metal halide and Na-air batteries have been considered to be promising for use in electric vehicles owing to good safety and high energy density, although less attention is focused on Na-metal cells than on Na-ion cells. This Minireview provides an overview of the fundamentals and recent progress in the fields of Na-metal halide and Na-air batteries, with the aim of providing a better understanding of new electrochemical systems. PMID:24953300

  14. Oxide Film Aging on Alloy 22 in Halide Containing Solutions

    International Nuclear Information System (INIS)

    Passive and corrosion behaviors of Alloy 22 in chloride and fluoride containing solutions, changing the heat treatment of the alloy, the halide concentration and the pH of the solutions at 90 deg. C, was investigated. The study was implemented using electrochemical techniques, which included open circuit potential monitoring over time, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements carried out at open circuit and at passivity potentials. Corrosion rates obtained by EIS measurements after 24 h immersion in naturally aerated solutions were below 0.5 ?m/year. The corrosion rates were practically independent of solution pH, alloy heat treatment and halide ion nature and concentration. EIS low frequency resistance values increased with applied potential in the passive domain and with polarization time in pH 6 - 1 M NaCl at 90 deg. C. This effect was attributed to an increase in the oxide film thickness and oxide film aging. High frequency capacitance measurements indicated that passive oxide on Alloy 22 presented a double n-type/p-type semiconductor behavior in the passive potential range. (authors)

  15. MgAl2O4 spinel refractory as containment liner for high-temperature alkali salt containing environments

    Science.gov (United States)

    Peascoe-Meisner, Roberta A [Knoxville, TN; Keiser, James R [Oak Ridge, TN; Hemric, James G [Knoxville, TN; Hubbard, Camden R [Oak Ridge, TN; Gorog, J Peter [Kent, WA; Gupta, Amul [Jamestown, NY

    2008-10-21

    A method includes containing a high-temperature alkali salt containing environment using a refractory containment liner containing MgAl.sub.2O.sub.4 spinel. A method, includes forming a refractory brick containing MgAl.sub.2O.sub.4 spinel having an exterior chill zone defined by substantially columnar crystallization and an interior zone defined by substantially equiaxed crystallization; and removing at least a portion of the exterior chill zone from the refractory brick containing MgAl.sub.2O.sub.4 spinel by scalping the refractory brick containing MgAl.sub.2O.sub.4 spinel to define at least one outer surface having an area of substantially equiaxed crystallization. A product of manufacture includes a refractory brick containing MgAl.sub.2O.sub.4 spinel including an interior zone defined by substantially equiaxed crystallization; and at least one outer surface having an area of substantially equiaxed crystallization.

  16. CONTRIBUTION TO THE STUDY OF HYDROXYMETYLATION REACTION OF ALKALI LIGNIN

    OpenAIRE

    Teodor Malutan; Raluca Nicu; Valentin I. Popa

    2008-01-01

    The hydroxymethylation of alkali lignin with formaldehyde in alkaline solution was studied. The influence of reaction conditions of the hydroxymethylation of alkali lignin was followed by modifying the temperature, time, and the ratios of NaOH to lignin and CH2O to lignin. Three different types of alkali lignin were utilized. The reaction was followed by total consumption of formaldehyde, and the resulting products were characterized through FTIR-spectra, thermogravimetry analysis, ash and mo...

  17. Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

    CERN Document Server

    Lammert, H; Lammert, Heiko; Heuer, Andreas

    2005-01-01

    The mixed-alkali effect on the cation dynamics in silicate glasses is analyzed via molecular dynamics simulations. Observations suggest a description of the dynamics in terms of stable sites mostly specific to one ionic species. As main contributions to the mixed--alkali slowdown longer residence times and an increased probability of correlated backjumps are identified. The slowdown is related to the limited accessibility of foreign sites. The mismatch experienced in a foreign site is stronger and more retarding for the larger ions, the smaller ions can be temporarily accommodated. Also correlations between unlike as well as like cations are demonstrated that support cooperative behavior.

  18. Synthesis, structural and spectral studies of five- and six-coordinate adducts of organotin(IV) halides containing dibenzylsulfoxide (DBSO) as ligand. The crystal structures of fac-[MeSnCl3(dbso)2] and trans-[Ph2SnCl2(dbso)2

    International Nuclear Information System (INIS)

    The reaction of the ambidentate ligand dibenzylsulfoxide (dbso) with Me2SnCl2 in 1:1 molar ratio leads to the formation of the five-coordinate adduct [Me2SnCl2(dbso)], whereas the same reaction conditions with Ph2SnCl2 provide the six-coordinate adduct trans-[Ph2SnCl2(dbso)2]. On the other hand, the reaction with ?Bu2SnCl2 forms the dimeric adduct [{?Bu2SnCl2(dbso)}2], which probably possesses octahedral tin(IV) nuclei and bridging chlorides. The adducts [MeSnCl3(dbso)2] and [Ph3SnCl(dbso)] were also prepared and included in the study. All complexes were studied by microanalysis and IR, NMR (1H, 13C and 119Sn) and Moessbauer spectroscopies to investigate their structural properties. The six-coordinate species fac-[MeSnCl3(dbso)2] and trans-[Ph2SnCl2(dbso)2] were also studied by single crystal X-ray diffractometry. These compounds crystallize in the orthorhombic, Pbcn, and monoclinic space group P21/c, respectively, as discrete neutral molecules with the tin(IV) atom in a distorted octahedral geometry and the two dbso ligands in cis and trans positions, respectively. (author)

  19. Structural and spectroscopic studies on the alkali borohydrides MBH4 (M=Na,K,Rb,Cs)

    OpenAIRE

    Renaudin, Guillaume; Gomes, Sandrine; Hagemann, Hans-Rudolf; Keller, L; Yvon, Klaus

    2004-01-01

    Alkali borohydrides MBH[4] and their deuterides have been investigated by X-ray and neutron powder diffraction (M=K,Rb,Cs) and by infrared and Raman spectroscopy (M=Na,K,Rb,Cs). At room temperature the compounds crystallize with a cubic high temperature (HT) structure having FM[3]M symmetry in which the [BH4][?] complexes are disordered. At low temperature (LT) the potassium compound transforms into a tetragonal low temperature structure having P4[2]/n mc symmetry in which the [BH4][?] comple...

  20. Tuning the decomposition temperature in complex hydrides: synthesis of a mixed alkali metal borohydride.

    OpenAIRE

    Nickels, EA; Jones, MO; David, WI; Johnson, SR; Lowton, RL; Sommariva, M; Edwards, PP

    2008-01-01

    Variegated decomposers: The synthesis of the first mixed alkali metal borohydride, which contains lithium and potassium, is presented. LiK(BH 4)2 (see picture; K crimson, Li yellow, B green, H gray) has a crystal structure similar to LiBH4, and a thermal decomposition temperature between those of LiBH4 and KBH4. Using this route, the hydrogen desorption thermodynamics of complex hydrides can be easily tailored. (Figure Presented). © 2008 Wiley-VCH Verlag GmbH and Co. KGaA.

  1. Compare study cellulose/Mn?O? composites using four types of alkalis by sonochemistry method.

    Science.gov (United States)

    Fu, Lian-Hua; Li, Shu-Ming; Bian, Jing; Ma, Ming-Guo; Long, Xing-Luan; Zhang, Xue-Ming; Liu, Shi-Jie

    2015-01-22

    The purpose of this article was to explore the influences of alkalis types on the cellulose/Mn3O4 composites via a sonochemistry method. In this study, cellulose/Mn3O4 composites were successfully fabricated using four types of alkalis (urea (CO(NH2)2), hexamethylenetetramine ((CH2)6N4, HMT), NaOH, and KOH) by an environmentally-friendly sonochemistry method. The phase, shape, thermal stability, and the formation mechanism of the cellulose composites were researched in detail. Experimental results demonstrated that the types of alkalis played an important role in the phase, shape, dispersion, and thermal stability of cellulose/Mn3O4 composites. By thermal treatment of cellulose/Mn3O4 composites at 600°C for 3h in air, the Mn3O4 crystals were obtained. This novel method reported here maybe has a guiding significance for the synthesis of manganese oxide materials and other metal oxides using cellulose as template. PMID:25439907

  2. Electrochemical devices utilizing molten alkali metal electrode-reactant

    Science.gov (United States)

    Hitchcock, David C. (Omaha, NE); Mailhe, Catherine C. (Berkeley, CA); De Jonghe, Lutgard C. (Oakland, CA)

    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.

  3. Dynamics of exchange and abstraction reactions in the systems hydrogen-hydrogen halide. Experimental results

    International Nuclear Information System (INIS)

    The modern status of experimental study of multi-channel interaction of H and D atoms with molecules of hydrogen halides HX (X=F, Cl, Br, I) is reviewed. Kinetic data of reactions in thermal equilibrium for all hydrogen halides are considered. Reactions of oscillatory-excited HX molecules, as well as reactions of hot hydrogen atoms in molecular beams or HX obtained by photolysis with molecules in the ground state are discussed. Some dynamic aspects of interaction of H and D atoms with hydrogen halides in molecular beams are considered. Most probable kinetic parameters characterizing exchange and abstraction reactions are discussed

  4. First Principles Calculations of Linear and Second-Order Optical Responses in Rhombohedrally Distorted Perovskite Ternary Halides, CsGeX3 (X = Cl, Br, and I)

    Science.gov (United States)

    Tang, Li-Chuan; Chang, Yia-Chung; Huang, Jung-Yau; Lee, Ming-Hsien; Chang, Chen-Shiung

    2009-11-01

    Systematic studies based on first-principles calculations of second-order optical susceptibilities as well as the dielectric function of CsGeX3 (X = Cl, Br, and I; CGX) are presented. The relationship between structural properties and optoelectronic responses are examined. The structural factors ??, and dGe, dX are proposed to describe the degree of distortion from an ideal perovskite structure. ?? and dGe increase when halide anions are changed from Cl to I; while halide anion displacement, dX, decreases. The structural distortion effect on these rhombohedral CGX crystals is analyzed by first-principles calculations. The dielectric function and the second harmonic generation (SHG) response coefficient also increase with increasing ?? and dGe. The direct band gaps (EG) of CsGeX3 all occur at the R-point, ?ER. The experimental band gaps of CGX crystals become smaller, i.e., ECGCG (=3.67 eV) >ECGBG (=2.32 eV) >ECGIG (=1.53 eV), as ?? and dGe increase, i.e., dCGCGegermanium. The calculated magnitudes of ?(2)ijk are close to some reported experimental values near the band gap.

  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

    Science.gov (United States)

    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 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. Cathode architectures for alkali metal / oxygen batteries

    Energy Technology Data Exchange (ETDEWEB)

    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. Imaging and Characterization of Molecules and One-Dimensional Crystals Formed within Carbon Nanotubes

    OpenAIRE

    Sloan, J.; Luzzi, DE; Kirkland, Ai; Hutchison, Jl; Green, Mlh

    2004-01-01

    The imaging and characterization of individual molecules and atomically thin, effectively one-dimensional crystals of rock salt and other halides encapsulated within single-walled carbon nanotubes are reviewed in this .article. These species were imaged by conventional and super-resolved high-resolution transmission electron microscopy and by scanning tunneling microscopy, revealing the detailed atomic structure of these nanoscopic species.

  8. Gas phase chromatography of halides of elements 104 and 105

    International Nuclear Information System (INIS)

    On-line isothermal gas phase chromatography was used to study halides of 261104 (T1/2 = 65 s) and 262,263105 (T1/2 = 34 s and 27 s) produced an atom-at-a time via the reactions 248Cm(18O, 5n) and 249Bk(18O, 5n, 4n), respectively. Using HBr and HCl gas as halogenating agents, we were able to produce volatile bromides and chlorides of the above mentioned elements and study their behavior compared to their lighter homologs in Groups 4 or 5 of the periodic table. Element 104 formed more volatile bromides than its homolog Hf. In contrast, element 105 bromides were found to be less volatile than the bromides of the group 5 elements Nb and Ta. Both 104 and Hf chlorides were observed to be more volatile than their respective bromides. 31 refs., 8 figs

  9. Recent progress in efficient hybrid lead halide perovskite solar cells

    Science.gov (United States)

    Cui, Jin; Yuan, Huailiang; Li, Junpeng; Xu, Xiaobao; Shen, Yan; Lin, Hong; Wang, Mingkui

    2015-06-01

    The efficiency of perovskite solar cells (PSCs) has been improved from 9.7 to 19.3%, with the highest value of 20.1% achieved in 2014. Such a high photovoltaic performance can be attributed to optically high absorption characteristics and balanced charge transport properties with long diffusion lengths of the hybrid lead halide perovskite materials. In this review, some fundamental details of hybrid lead iodide perovskite materials, various fabrication techniques and device structures are described, aiming for a better understanding of these materials and thus highly efficient PSC devices. In addition, some advantages and open issues are discussed here to outline the prospects and challenges of using perovskites in commercial photovoltaic devices.

  10. Diffusion coefficients of alkali metal atoms in hydrogen and deuterium

    International Nuclear Information System (INIS)

    Diffusion coefficients of rubidium and cesium atoms in molecular hydrogen and deuterium have been determined experimentally by a method based on the effect of non-resonance spin echo in a set of optically oriented atoms of alkali metals. Anomalous effect of isotopic composition of buffer gas molecules on the value of diffusion coefficient of the alkali metal atoms has been revealed

  11. Thermochemical properties of the alkali hydroxides: A review

    Energy Technology Data Exchange (ETDEWEB)

    Konings, R.J.M.; Cordfunke, E.H.P. (Stichting Energieonderzoek Centrum Nederland, Petten)

    1989-09-01

    The formation of volatile alkali hydroxides as a result of high-temperature steam corrosion plays an important role in nuclear technology. For the modeling of the volatilization processes, reliable thermodynamic data are required. In the present paper recent physico-chemical experiments by the authors will be discussed and the thermochemical properties of the alkali hydroxide series will be evaluated. (orig.).

  12. Thermochemical properties of the alkali hydroxides. A review

    Energy Technology Data Exchange (ETDEWEB)

    Konings, R.J.; Cordfunke, E.H.

    1988-11-01

    The formation of volatile alkali hydroxides as a result of high-temperature steam corrosion plays an important role in nuclear technology. For the modeling of the volatilization processes, reliable thermodynamic data are required. Recent physico-chemical experiments are discussed and the thermochemical properties of the alkali hydroxide series are evaluated. 6 figs., 66 refs., 7 tabs.

  13. NEW THIO S2- ADDUCTS WITH ANTIMONY (III AND V HALIDE: SYNTHESIS AND INFRARED STUDY

    Directory of Open Access Journals (Sweden)

    HASSAN ALLOUCH

    2013-12-01

    Full Text Available Five new S2- adducts with SbIII and SbV halides have been synthesized and studied by infrared. Discrete structures have been suggested, the environment around the antimony being tetrahedral, trigonal bipyramidal or octahedral.

  14. PALLADIUM CATALYZED COUPLING OF ARYL HALIDES WITH ARYLHALOSILANES IN AIR AND WATER. (R828129)

    Science.gov (United States)

    In the presence of a palladium catalyst, various aryl halides reacted with arylhalosilanes in aqueous media and under an air atmosphere to give the corresponding unsymmetrical aryl–aryl coupling products conveniently. ...

  15. A Contribution to the estimation of binary halide and pseudo-halide equilibrium constants using a linear extrapolation methodology

    Scientific Electronic Library Online (English)

    Astréa F. de S., Silva; Manuel M., Ortega; Cristo B., Melios; Leonardo, Pezza; Mercedes de, Moraes; Mário Alberto, Tenan; André F., Oliveira.

    Full Text Available O coeficiente de atividade molar individual do íon fluoreto (yF) foi determinado a 25° C para valores de força iônica entre 0,100 and 3,00 mol L-1 (NaClO4) usando-se um eletrodo íon-seletivo. A dependência do coeficiente de atividade com a força iônica é explicada pela equação ?F = log yF = 0,2315I [...] - 0,041I². A função ?F(I), foi associada a outras funções estimadas em trabalhos anteriores, por exemplo,?Cu(I) para cobre, e ?H(I) para íon hidrogênio, possibilitando a estimativa de constantes de estabilidade estequiométricas e termodinâmicas tanto para equilíbrios de protonação de alguns haletos e pseudo-haletos como para as constantes de formação de complexos 1:1 de metais bivalentes com fluoreto e pseudo-haletos. O procedimento de cálculo proposto é consistente com dados experimentais criticamente selecionados da literatura. Verificou-se que é possível usar ?F(I) na previsão de parâmetros de equilíbrio termodinâmicos independentemente do caráter HSAB de Pearson . Abstract in english The molar single ion activity coefficient (yF) of fluoride ions was determined at 25 °C and ionic strengths between 0.100 and 3.00 mol L-1 NaClO4 using an ion-selective electrode. The activity coefficient dependency on ionic strength was determined to be ?F = log yF = 0.2315I - 0.041I². The function [...] ?F(I), combined with functions obtained in previous work for copper (?Cu) and hydrogen (?H), allowed us to make the estimation of the stoichiometric and thermodynamic protonation constants of some halides and pseudo-halides as well as the formation constants of some pseudo-halides and fluoride 1:1 bivalent cation complexes. The calculation procedure proposed in this paper is consistent with critically-selected experimental data. It was demonstrated that it is possible to use ?F(I) for predicting the thermodynamic equilibrium parameters independently of Pearson's hardness of acids and bases.

  16. Reactivity of mercury(II) halides with the unsymmetrical phosphorus ylide Ph2PCH2CH2PPh2=C(H)C(O)Ph: Crystal structure of {HgI2 [PPh2CH2CH2PPh2=C(H)C(O)Ph]}n

    OpenAIRE

    Ebrahim, Mothi Mohamed; Stoeckli-evans, Helen; Panchanatheswaran, Krishnaswamy

    2009-01-01

    The unsymmetrical phosphorus ylide, Ph2PCH2CH2PPh2=C(H)C(O)Ph is shown to react with Hg(II) halides to form polymeric products with the composition {HgX2 [PPh2CH2CH2PPh2C(H)C(O)Ph]}n, where X = Cl (1), Br (2), I (3). The complexes have been characterized by elemental analysis, IR, 1H, 31P NMR spectra as well as by ESI mass spectra. In product 1 the ylide exhibits a P, C-bridging mode of coordination, while in 2 and 3 it shows a monodentate P-coordination with the dangling ylide. The structur...

  17. Alkali metal anions: an unusual oxidation state

    International Nuclear Information System (INIS)

    Background information concerning the M- state of alkali metals is summarized. Pulse-radiolysis techniques used in various studies to verify the existence of the M- species in certain solvents are discussed. Thermodynamics of the anion formation are considered: and using Na+I- as a model, the lattice enthalpy of a hypothetical Na+Na-(s) has been computed to be 13.7 kcal/mole. Reactions with a complexing agent such as crown ethers and m,n,o cryptand which interacts strongly with the M+ from the M+M- entity yielded solid salts of Na-. Free energy calculations are made; and the conclusion is drawn that, with the possible exception of Cs, suitable salts of all the alkali meal anions should be thermodynamically stable. The solid salt of Na- with cryptand, Na+C.Na-, was prepared, isolated, and characterized with an overall stoichiometry of Na2C18H36O6N2 being established. Powder conductivity measurements on the shiny, gold-colored material indicated that in spite of metallic appearance the material is probably a semiconductor. Crystallographic studies indicate that the solid may be viewed as essentially alternate layers in a hexagonally packed arrangement. NMR spectra of the compound in solutions are recorded, and the compound is proposed for use as a two-electron reducing agent. for use as a two-electron reducing agent. 98 references

  18. Dynamics of reactive ultracold alkali polar molecules

    Science.gov (United States)

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

    2011-05-01

    Recently, ultracold polar molecules of KRb have been created. These molecules are chemically reactive and their lifetime in a trap is limited. However, their lifetime increases when they are loaded into a 1D optical lattice in the presence of an electric field. These results naturally raise the question of manipulating ultracold collisions of other species of alkali dimer molecules, with an eye toward both novel stereochemistry, as well as suppressing unwanted reactions, to enable condensed matter applications. In this talk, we report on a comparative study between the bi-alkali polar molecules of LiNa, LiK, LiRb, LiCs which have been predicted to be reactive. We compute the isotropic C6 coefficients of these systems and we predict the elastic and reactive rate coefficients when an electric field is applied in a 1D optical lattice. We will discuss the efficacy of evaporative cooling for each species. This work was supported by a MURI-AFOSR grant.

  19. Reactions at alkali metal-glass interfaces

    International Nuclear Information System (INIS)

    The discovery of solids which exhibit high ionic conductivity has stimulated efforts to construct high energy density batteries utilizing such solids as the electrolytes. The most common of these include alkali ion conductors such as polycrystalline Na ?-alumina and NASICON. More recently, glasses in the form of borates, silicates, phosphates and others have also been shown to exhibit extremely high Li, Na, and Ag ion conductivity. since glasses are isotropic and may be fabricated easily into complex shapes they would appear to be highly attractive alternatives to some of the polycrystaline electrolytes mentioned above. Although a number of glassy electrolytes possess the required high ionic conductivities for cell operation, little or no information is available with regards to their corrosion resistance against potential reactants such as alkali metals, alloys and fused salts. As part of a program to investigate the potential of lithium borate based glasses as solid electrolytes, we have begun to investigate the reactions that occur at the glass-liquid lithium interface under both quiescent and ionic current flow conditions

  20. Influence of electrode, buffer gas and control gear on metal halide lamp performance

    International Nuclear Information System (INIS)

    In this paper the influence of electrode composition, buffer gas fill pressure and control gear on the performance of metal halide lamps is investigated. It is shown that pure tungsten electrodes improve lumen maintenance and reduce voltage rise over lamp life. An optimum buffer gas fill pressure condition is discovered which allows for reduced electrode erosion during lamp starting as well as under normal operating conditions. Use of electronic control gear is shown to improve the performance of metal halide lamps

  1. Rashba Spin-Orbit Coupling Enhanced Carrier Lifetime in Organometal Halide Perovskites

    OpenAIRE

    Zheng, Fan; Tan, Liang Z.; LIU, SHI; Rappe, Andrew M.

    2015-01-01

    Organometal halide perovskites are promising solar-cell materials for next-generation photovoltaic applications. The long carrier lifetime and diffusion length of these materials make them very attractive for use in light absorbers and carrier transporters. While these aspects of organometal halide perovskites have attracted the most attention, the consequences of the Rashba effect, driven by strong spin-orbit coupling, on the photovoltaic properties of these materials are l...

  2. Valence and conduction bands engineering in halide perovskites for solar cell applica- tions

    OpenAIRE

    Meloni, Simone; Palermo, Giulia; Astani, Negar Ashari; Curchod, Basile F. E.; Graetzel, Michael; Roethlisberger, Ursula

    2014-01-01

    We performed ab initio simulations aimed at identifying the atomistic and electronic structure origin of the high valence and conduction band, and band gap tunability of halide perovskites. We found that the two key ingredients are the overlap between bivalent cation and halide atomic orbitals, and the electronic charge of the bottom of the conduction band (CBM) state on the Sn or Pb atoms. In particular, we found that lower gaps are associated to higher negative antibonding...

  3. The effect of low solublility organic acids on the hygroscopicity of sodium halide aerosols

    OpenAIRE

    L. Miñambres; Méndez, E.; M. N. Sánchez; Castaño, F; F. J. Basterretxea

    2014-01-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be performed in this study. The hygroscopic properties of sodium halide submicrometer particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were gen...

  4. The effect of low solublility organic acids on the hygroscopicity of sodium halide aerosols

    OpenAIRE

    Min?ambres, L.; Me?ndez, E.; Sa?nchez, M. N.; Castan?o, F.; Basterretxea, F. J.

    2014-01-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be investigated in this study. The hygroscopic properties of sodium halide sub-micrometre particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles w...

  5. Electrocatalysis and electron transfer mechanisms in the reduction of organic halides at Ag

    OpenAIRE

    Mussini, Patrizia Romana; FALCIOLA, LUIGI; ROSSI, MANUELA

    2009-01-01

    The reductive cleavage of a series of organic halides, including both aromatic and aliphatic compounds, has been investigated in acetonitrile at glassy carbon and silver electrodes. Ag exhibits extraordinary electrocatalytic activities for the reduction of most of the investigated halides. During the reductive cleavage of a carbon-halogen bond, electron transfer (ET) and bond breaking may occur either in a single step or in two distinct steps. The compounds examined in this study are represen...

  6. Synthesis, structural and spectral studies of five- and six-coordinate adducts of organotin(IV) halides containing dibenzylsulfoxide (dbso) as ligand. The crystal structures of fac-[MeSnCl3(dbso)2] and trans-[Ph2SnCl2(dbso)2

    Scientific Electronic Library Online (English)

    Gerimário F. de, Sousa; José R., Sabino; Ivo, Vencato; Carlos A. L., Filgueiras; José D., Ardisson.

    1425-14-01

    Full Text Available A reação do ligante ambidentado dibenzilsulfóxido (dbso) com Me2SnCl2 na proporção molar 1:1 leva à formação do produto pentacoordenado [Me2SnCl2(dbso)], enquanto Ph2SnCl2 leva à formação do complexo hexacoordenado trans-[Ph2SnCl2(dbso)2], utilizando as mesmas condições de reação. Por outro lado, a [...] reação com nBu2SnCl2 forma o produto bimetálico [{nBu2SnCl2(dbso)}2], o qual provavelmente possui núcleos de estanho(IV) octaédricos e cloretos em ponte. Os complexos [MeSnCl3(dbso)2] e [Ph3SnCl(dbso)] também foram preparados. Todos os produtos foram estudados por análise elementar e por espectroscopias no IV, RMN (¹H, 13C, 119Sn) e Mössbauer. As espécies hexacoordenadas fac-[MeSnCl3(dbso)2] e trans-[Ph2SnCl2(dbso)2] foram também estudadas por difratometria de raios X; as determinações estruturais revelaram que estes compostos cristalizam-se nos sistemas cristalinos ortorrômbico, Pbcn, e monoclínico, P2(1)/c, respectivamente. As moléculas possuem átomos de estanho(IV) numa geometria octaédrica distorcida, com os dois ligantes dbso em posições cis e trans, respectivamente. Abstract in english The reaction of the ambidentate ligand dibenzylsulfoxide (dbso) with Me2SnCl2 in 1:1 molar ratio leads to the formation of the five-coordinate adduct [Me2SnCl2(dbso)], whereas the same reaction conditions with Ph2SnCl2 provide the six-coordinate adduct trans-[Ph2SnCl2(dbso)2]. On the other hand, the [...] reaction with nBu2SnCl2 forms the dimeric adduct [{nBu2SnCl2(dbso)}2], which probably possesses octahedral tin(IV) nuclei and bridging chlorides. The adducts [MeSnCl3(dbso)2] and [Ph3SnCl(dbso)] were also prepared and included in the study. All complexes were studied by microanalysis and IR, NMR (¹H, 13C and 119Sn) and Mössbauer spectroscopies to investigate their structural properties. The six-coordinate species fac-[MeSnCl3(dbso)2] and trans-[Ph2SnCl2(dbso)2] were also studied by single crystal X-ray diffractometry. These compounds crystallize in the orthorhombic, Pbcn, and monoclinic space group P2(1)/c, respectively, as discrete neutral molecules with the tin(IV) atom in a distorted octahedral geometry and the two dbso ligands in cis and trans positions, respectively.

  7. Determination of halide impurities in ionic liquids by total reflection X-ray fluorescence spectrometry.

    Science.gov (United States)

    Vander Hoogerstraete, Tom; Jamar, Steven; Wellens, Sil; Binnemans, Koen

    2014-04-15

    The determination and quantification of halide impurities in ionic liquids is highly important because halide ions can significantly influence the chemical and physical properties of ionic liquids. The use of impure ionic liquids in fundamental studies on solvent extraction or catalytic reactions can lead to incorrect experimental data. The detection of halide ions in solution by total reflection X-ray fluorescence (TXRF) has been problematic because volatile hydrogen halide (HX) compounds are formed when the sample is mixed with the acidic metal standard solution. The loss of HX during the drying step of the sample preparation procedure gives imprecise and inaccurate results. A new method based on an alkaline copper standard Cu(NH3)4(NO3)2 is presented for the determination of chloride, bromide, and iodide impurities in ionic liquids. The 1-butyl-3-methylimidazolium ([C4mim]) ionic liquids with the anions acetate ([C4mim][OAc]), nitrate ([C4mim][NO3]), trifluoromethanesulfonate ([C4mim][OTf]), and bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]) were synthesized via a halide-free route and contaminated on purpose with known amounts of [C4mim]Cl, [C4mim]Br, [C4mim]I, or potassium halide salts in order to validate the new method and standard. PMID:24628670

  8. The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols

    Science.gov (United States)

    Miñambres, L.; Méndez, E.; Sánchez, M. N.; Castaño, F.; Basterretxea, F. J.

    2014-10-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be investigated in this study. The hygroscopic properties of sodium halide sub-micrometre particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were generated by flowing atomized sodium halide particles (either dry or aqueous) through a heated oven containing the gaseous acid. The obtained results indicate that gaseous organic acids easily nucleate onto dry and aqueous sodium halide particles. On the other hand, scanning electron microscopy (SEM) images indicate that lauric acid coating on NaCl particles makes them to aggregate in small clusters. The hygroscopic behaviour of covered sodium halide particles in deliquescence mode shows different features with the exchange of the halide ion, whereas the organic surfactant has little effect in NaBr particles, NaCl and NaI covered particles experience appreciable shifts in their deliquescence relative humidities, with different trends observed for each of the acids studied. In efflorescence mode, the overall effect of the organic covering is to retard the loss of water in the particles. It has been observed that the presence of gaseous water in heterogeneously nucleated particles tends to displace the cover of hexanoic acid to energetically stabilize the system.

  9. The effect of low solublility organic acids on the hygroscopicity of sodium halide aerosols

    Science.gov (United States)

    Miñambres, L.; Méndez, E.; Sánchez, M. N.; Castaño, F.; Basterretxea, F. J.

    2014-02-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be performed in this study. The hygroscopic properties of sodium halide submicrometer particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were generated by flowing atomized sodium halide particles (either dry or aqueous) through a heated oven containing the gaseous acid. The obtained results indicate that gaseous organic acids easily nucleate onto dry and aqueous sodium halide particles. On the other hand, Scanning Electron Microscopy (SEM) images indicate that lauric acid coating on NaCl particles makes them to aggregate in small clusters. The hygroscopic behaviour of covered sodium halide particles in deliquescence mode shows different features with the exchange of the halide ion: whereas the organic covering has little effect in NaBr particles, NaCl and NaI covered particles change their deliquescence relative humidities, with different trends observed for each of the acids studied. In efflorescence mode, the overall effect of the organic covering is to retard the loss of water in the particles. It has been observed that the presence of gaseous water in heterogeneously nucleated particles tends to displace the cover of hexanoic acid to energetically stabilize the system.

  10. Fluorescence-Based Bacterial Bioreporter for Specific Detection of Methyl Halide Emissions in the Environment

    Science.gov (United States)

    Farhan Ul Haque, Muhammad; Nadalig, Thierry; Bringel, Françoise; Schaller, Hubert

    2013-01-01

    Methyl halides are volatile one-carbon compounds responsible for substantial depletion of stratospheric ozone. Among them, chloromethane (CH3Cl) is the most abundant halogenated hydrocarbon in the atmosphere. Global budgets of methyl halides in the environment are still poorly understood due to uncertainties in their natural sources, mainly from vegetation, and their sinks, which include chloromethane-degrading bacteria. A bacterial bioreporter for the detection of methyl halides was developed on the basis of detailed knowledge of the physiology and genetics of Methylobacterium extorquens CM4, an aerobic alphaproteobacterium which utilizes chloromethane as the sole source of carbon and energy. A plasmid construct with the promoter region of the chloromethane dehalogenase gene cmuA fused to a promotorless yellow fluorescent protein gene cassette resulted in specific methyl halide-dependent fluorescence when introduced into M. extorquens CM4. The bacterial whole-cell bioreporter allowed detection of methyl halides at femtomolar levels and quantification at concentrations above 10 pM (approximately 240 ppt). As shown for the model chloromethane-producing plant Arabidopsis thaliana in particular, the bioreporter may provide an attractive alternative to analytical chemical methods to screen for natural sources of methyl halide emissions. PMID:23956392

  11. Enhanced photoluminescence and solar cell performance via Lewis base passivation of organic-inorganic lead halide perovskites.

    Science.gov (United States)

    Noel, Nakita K; Abate, Antonio; Stranks, Samuel D; Parrott, Elizabeth S; Burlakov, Victor M; Goriely, Alain; Snaith, Henry J

    2014-10-28

    Organic-inorganic metal halide perovskites have recently emerged as a top contender to be used as an absorber material in highly efficient, low-cost photovoltaic devices. Solution-processed semiconductors tend to have a high density of defect states and exhibit a large degree of electronic disorder. Perovskites appear to go against this trend, and despite relatively little knowledge of the impact of electronic defects, certified solar-to-electrical power conversion efficiencies of up to 17.9% have been achieved. Here, through treatment of the crystal surfaces with the Lewis bases thiophene and pyridine, we demonstrate significantly reduced nonradiative electron-hole recombination within the CH(3)NH(3)PbI(3-x)Cl(x) perovskite, achieving photoluminescence lifetimes which are enhanced by nearly an order of magnitude, up to 2 ?s. We propose that this is due to the electronic passivation of under-coordinated Pb atoms within the crystal. Through this method of Lewis base passivation, we achieve power conversion efficiencies for solution-processed planar heterojunction solar cells enhanced from 13% for the untreated solar cells to 15.3% and 16.5% for the thiophene and pyridine-treated solar cells, respectively. PMID:25171692

  12. Cerium-doped mixed-alkali rare-earth double-phosphate scintillators for thermal neutron detection

    Science.gov (United States)

    Neal, John S.; Boatner, Lynn A.; Spurrier, Merry; Szupryczynski, Piotr; Melcher, Charles L.

    2007-08-01

    Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K 2CsLu(PO 4) 2 and CsLi 2Lu(PO 4) 2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. New members of the rare-earth double-phosphate family have been synthesized by high-temperature flux growth. These new samples, represented by the general formula (A,B) 3Lu(PO 4) 2:Ce where A and B are alkali elements, incorporate lithium as one of the components and varying levels of Ce doping. Characteristics important to gamma-ray and thermal neutron excitation are calculated for three model systems which incorporate total lithium-ion substitution. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. Future work includes (1) synthesis of mixed-alkali scandium and yttrium double-phosphates in which Li ions are substitutional in the structure with varying lithium-ion content up to and including total lithium-ion substitution on the alkali ion site and (2) measurements of light output and pulse shape using thermal neutron excitation.

  13. Cerium-doped mixed-alkali rare-earth double-phosphate scintillators for thermal neutron detection

    International Nuclear Information System (INIS)

    Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K2CsLu(PO4)2 and CsLi2Lu(PO4)2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. New members of the rare-earth double-phosphate family have been synthesized by high-temperature flux growth. These new samples, represented by the general formula (A,B)3Lu(PO4)2:Ce where A and B are alkali elements, incorporate lithium as one of the components and varying levels of Ce doping. Characteristics important to gamma-ray and thermal neutron excitation are calculated for three model systems which incorporate total lithium-ion substitution. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. Future work includes (1) synthesis of mixed-alkali scandium and yttrium double-phosphates in which Li ions are substitutional in the structure with varying lithium-ion content up to and including total lithium-ion substitution on the alkali ion site and (2) measurements of lighkali ion site and (2) measurements of light output and pulse shape using thermal neutron excitation

  14. Controlled in-situ dissolution of an alkali metal

    Science.gov (United States)

    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.

  15. Alkali absorption and citrate excretion in calcium nephrolithiasis

    Science.gov (United States)

    Sakhaee, K.; Williams, R. H.; Oh, M. S.; Padalino, P.; Adams-Huet, B.; Whitson, P.; Pak, C. Y.

    1993-01-01

    The role of net gastrointestinal (GI) alkali absorption in the development of hypocitraturia was investigated. The net GI absorption of alkali was estimated from the difference between simple urinary cations (Ca, Mg, Na, and K) and anions (Cl and P). In 131 normal subjects, the 24 h urinary citrate was positively correlated with the net GI absorption of alkali (r = 0.49, p renal tubular acidosis (RTA), urinary citrate excretion was subnormal relative to net GI alkali absorption, with data from most patients residing outside the 95% confidence ellipse described for normal subjects. However, the normal relationship between urinary citrate and net absorbed alkali was maintained in 11 patients with chronic diarrheal syndrome (CDS) and in 124 stone-forming patients devoid of RTA or CDS, half of whom had "idiopathic" hypocitraturia. The 18 stone-forming patients without RTA or CDS received potassium citrate (30-60 mEq/day). Both urinary citrate and net GI alkali absorption increased, yielding a significantly positive correlation (r = 0.62, p renal origin of hypocitraturia. However, the normal dependence was maintained in CDS and in idiopathic hypocitraturia, suggesting that reduced citrate excretion was largely dietary in origin as a result of low net alkali absorption (from a probable relative deficiency of vegetables and fruits or a relative excess of animal proteins).

  16. Sampling of alkali metals in nuclear application

    International Nuclear Information System (INIS)

    The sampling of alkali metals in nuclear application for analytical procedures has to take into account their reactivity with the atmosphere. Flow-through and overflow methods are developed to get samples which have to be completely used without dividing them, since segregation of impurities occurs at cooling and solidification. The samplers are tight in order to prevent any contamination with atmospheric gases. They have to be opened to get out the samples in a purified argon atmosphere. The procedure has been capable to analyze 1 ?g of oxygen per g of sodium, in agreement with the results of in-line analyses which are performed with electrochemical probes. Thus, representative samples of sodium can be obtained from large nuclear cooling circuits. (orig.)

  17. Study on alkali metal thermoelectric converter

    International Nuclear Information System (INIS)

    The alkali metal thermoelectric converter (AMTEC) utilizing the sodium ion conducting ?''-alumina solid electrolyte (BASE) is a device to convert heat energy to electric energy directly. It is characterized by high conversion efficiencies (20-40%), high power densities (1 W/cm2), no moving parts, low maintenance requirements, high durability, and efficiency independent of size. Because of these merits, AMTEC is one of the most promising candidate for dispersed small scale power station, remote power station and aerospace power systems. In this paper, the theoretical and experimental studies on the thin film electrodes characteristics, power generating characteristics, cell efficiency, integral electrode with large current lead, porous metal current lead, series connected cells power generation, potassium AMTEC, wick return AMTEC and system analysis for space and grand use are reported. (J.P.N.) 79 refs

  18. The source for polarized alkali ions

    International Nuclear Information System (INIS)

    The source for polarized heavy ions (PSI) has been used to produce polarized beams of 6Li and 23Na. Reactions of 6Li on 26Mg at 44 MeV and 23Na on 206Pb at 170 MeV have been investigated. The method of polarizing an alkali atomic beam by optical pumping has been improved by using an electrooptic modulated laser beam. In accordance with the primary work of J. Kelly (Boulder, USA) and W. Ertmer (Bonn, FRG), a LiTaO3 electrooptic modulator has been constructed and with this new equipment, the figure of merit of the source has been improved by a factor of 4. (orig.)

  19. Heat pipes containing alkali metal working fluid

    International Nuclear Information System (INIS)

    This invention is concerned with improving high temperature evaporation-condensation heat-transfer devices which have important and unique advantage in terrestrial and space energy processing. 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. In accordance with the invention 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

  20. Raman spectroscopic studies on mixed alkali borotungsten glasses

    Science.gov (United States)

    Edukondalu, A.; Srinivasu, CH.; Rahman, Syed; Sathe, V.; Kumar, K. Siva

    2014-04-01

    Mixed alkali borate glasses of composition xLi2O-(30-x)K2O-10WO3-60B2O3 (0 ? x ? 30 mol%) were prepared by melt quench technique. The structure of present glass system was investigated by Raman spectroscopy. The characteristic bands of these glasses due to the stretching and bending vibrations were identified and analyzed by the increasing of alkali content. This fact allowed us to identify the specific structural units which appear in these glasses and thus to point out the network modifier role of alkali oxide for low concentrations and its former role at high concentrations.

  1. Partial melting and fractionation in the Mesa Chivato alkali basalt-trachyte series, Mount Taylor Volcanic Field, New Mexico

    Science.gov (United States)

    Schrader, C. M.; Schmidt, M. E.; Crumpler, L. S.; Wolff, J. A.

    2012-12-01

    Mesa Chivato comprises a series of alkaline cones, flows, and domes within the Mount Taylor Volcanic Field (MTVF) in northwest New Mexico. Compositions range from alkali basalt to trachyte. Intermediate magmas are less well represented than mafic and felsic rocks, but benmoreites and transitional benmoreite-trachytes provide a window into the differentiation processes. Major element, trace element, and isotopic data suggest that petrogenesis of benmoreite proceeded by fractional crystallization of mafic liquids and magma mixing with partially melted mafic rocks. Major element mass balance models permit the derivation of transitional benmoreite/trachyte from the benmoreite by 20-25% crystallization of microphenocryst phases (olivine, plagioclase, Ti-magnetite, and apatite) and further fractionation to trachyte by 10-15% crystallization of olivine, plagioclase and alkali feldspar, Fe-Ti oxide, and apatite. These models are supported by SiO2-Sr and -Ba systematics. However, the hawaiite to benmoreite gap cannot be crossed by fractional crystallization alone. While major element models permit the mafic lavas to yield the benmoreite, they require extensive fractionation of clinopyroxene and plagioclase - this is unsupported by petrography (clinopyroxene phenocrysts are rare in the mafic rocks and lacking in the intermediate rocks) and cannot explain the benmoreite's very high Sr contents (>1800 ppm), which would have been depleted by plagioclase fractionation. From LA-ICPMS analysis of plagioclase: 87Sr/86Sr of early alkali basalt (0.70285-0.70300) and late hawaiite (0.70406-0.70421) bracket the 87Sr/86Sr of the benmoreite (0.70361-0.70406). Thus, either could represent the fractionated liquid parental to the benmoreite and the other the partially melted source.

  2. Electronic structure of copper halides CuI and CuCl: A comparative X-Ray photoelectron and absorption spectroscopy study

    Science.gov (United States)

    Generalov, A. V.; Vinogradov, A. S.

    2013-06-01

    The energy distributions of the occupied and unoccupied electronic states for copper halides CuCl and CuI have been investigated using X-ray photoemission and absorption spectroscopy with a highenergy resolution on the equipment of the Russian-German beamline for outlet and monochromatization of synchrotron radiation from the electron storage ring BESSY II. A quasi-molecular analysis of the obtained experimental spectra has revealed that there is a fundamental similarity of the energy structures of the valence band and the conduction band of copper halides Cu X ( X = Cl, I) due to the identical atomic structure of the studied compounds. The differences in the positions of individual energy subbands in the valence band and the conduction band of Cu X and in their intensities in the spectra are associated with different degrees of hybridization of the Cu 3 d, 4 s and X( n + 1) s, np valence states, as well as with different sizes of structural units (CuCl4 and CuI4 quasi-molecules) of the studied crystals.

  3. Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01

    International Nuclear Information System (INIS)

    This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and 3:Ce+3) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr3:Ce+3 powder, free of oxyhalide, were produced by a rigorously coxyhalide, were produced by a rigorously controlled process. (2) Micron size (? 5 (micro)m), platelet shape LaBr3 seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr3 (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr3 ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr3 is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable

  4. Studies of some reactions between uranyl halides and hydrocarbyl anions

    International Nuclear Information System (INIS)

    Reactions of uranyl halides (UO sub 2 X sub 2) with hydrocarbyl anions of the type (R=Ar sup - or Ar sub n H sub 3 sub - sub n C sup -), result in the formation of thermally unstable intermediates ([UO sub 2 R sub 2 X sub 2] sup - sup 2) which undergo thermolysis to give uranium dioxide and organic products. The type of organic product obtained depends on the thermolysis pathway of the intermediate. If the intermediate thermolysis occurs via H-abstraction, the monomer RH is formed, and if thermolysis occurs via reductive elimination (coupling) the dimer R-R is obtained. The thermolysis pathways, the yield of organic products, and the type of these products are discussed on the basis of electronic and steric factors. When the hydrocarbyl group used is benzilic, the main factor that controls reactivity is found to be electronic. On the other hand, the steric factor is the main factor that controls the reactivity in the case of phenolic type hydrocarbyls. Differences in reactivity between uranyl chloride and uranyl bromide towards hydrocarbyl anions are discussed. 25 refs., 2 figs., 3 tabs. (A.M.H.)

  5. Alkali activation of halloysite for adsorption and release of ofloxacin

    Science.gov (United States)

    Wang, Qin; Zhang, Junping; Wang, Aiqin

    2013-12-01

    Halloysite nanotubes are promising vehicles for the controlled release of drug molecules. Here, we systematically investigated the effects of alkali activation on the physicochemical properties, structure and morphology of halloysite nanotubes by XRD, FTIR, SEM and TEM, etc. Afterwards, the adsorption and in vitro release properties of halloysite for cationic ofloxacin (OFL) were evaluated. The results indicate that alkali activation dissolves amorphous aluminosilicate, free silica and alumina, which results in the increase in pore volume and pore size. OFL is adsorbed onto halloysite via electrostatic interaction and complexation. Alkali activation could increase the adsorption capacity of halloysite for OFL and prolong release of the adsorbed OFL compared with the natural halloysite. Thus, alkali activation of halloysite is an effective protocol to improve the adsorption and prolong release for cationic drug molecules.

  6. Alkali-bonded ceramics with hierarchical tailored porosity.

    Czech Academy of Sciences Publication Activity Database

    Landi, E.; Medri, V.; Papa, E.; D?de?ek, Ji?í; Klein, Petr; Benito, P.; Vaccari, A.

    2013-01-01

    Ro?. 73, SI (2013), s. 56-64. ISSN 0169-1317 Institutional support: RVO:61388955 Keywords : alkali-bonded ceramics * metalcaolin * geopolymerization parameters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.703, year: 2013

  7. Saccharification of gamma-ray and alkali pretreated lignocellulosics

    International Nuclear Information System (INIS)

    Enzymic saccharification of gamma ray and alkali pretreated sawdust, rice straw, and sugar cane bagasse showed higher release of reducing sugar from pretreated substrates. By gamma ray treatment alone (500 kGy) reducing sugar release of 2.8, 9.2, and 10 g/l was obtained from 7.5% (w/v) sawdust, rice straw, and bagasse and the same substrates showed reducing sugar release of 4.2, 30, and 20 g/l respectively when treated with alkali (0.1 g/g). Combination of gamma ray with alkali treatment further increased the reducing sugar release to 10.2, 33, and 36 g/l from sawdust, rice straw, and bagasse respectively. The effects of gamma ray and alkali treatment on saccharification varied with the nature of the substrate

  8. The 4843 Alkali Metal Storage Facility Closure Plan

    International Nuclear Information System (INIS)

    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

  9. Photoconductivity enhancement in alkali metal doped multiwall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Khoshnevisan, B., E-mail: b.khosh@kashanu.ac.ir [Faculty of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Zareie Mahmoudabadi, M.; Izadifard, M. [Faculty of Physics, University of Shahroud, Shahroud (Iran, Islamic Republic of)

    2013-12-06

    Photoconductivity effects in pristine and alkali-metal (K, Li) doped multiwalled carbon nanotubes (CNTs) were studied under xenon (100 mW) and also halogen (10 mW) light continues sources. To perform the measurements, the pristine and alkali doped CNTs were deposited into pores of a silver foam plate with nano-metric porosity by electrophoresis technique. The foam acted as a conducting frame for sweeping the photo-induced electrons to prevent rapid local electron–hole recombination in the CNTs. The radiation spectrum of the xenon source was similar to the Sun light spectrum and under normal ambient condition the photocurrents in the alkali doped samples were enhanced noticeably in comparison with the pristine CNTs. These results present a functional photoconductive performance of a heap of as-prepared alkali-metal doped CNTs that would be applicable as a light sensor without the necessity of separation between metallic and semiconducting CNTs (m- and s-CNTs).

  10. A Case of Severe Airbag Related Ocular Alkali Injury

    OpenAIRE

    Shawn S Barnes; Wong, William; Affeldt, John C

    2012-01-01

    While airbags have saved many lives and are clearly beneficial overall, sodium hydroxide (NaOH) powder produced by the inflation reaction can cause significant alkali ocular injury if not irrigated promptly. Here we report a case of severe airbag related ocular alkali injury as a way to bring attention to the need for prompt ocular irrigation following motor vehicle accidents (MVA) with airbag deployment.

  11. Alkali promotion of N-2 dissociation over Ru(0001)

    DEFF Research Database (Denmark)

    Mortensen, Jens JØrgen; Hammer, BjØrk

    1998-01-01

    Using self-consistent density functional calculations, we show that adsorbed Na and Cs lower the barrier for dissociation of N2 on Ru(0001). Since N2 dissociation is a crucial step in the ammonia synthesis reaction, we explain in this way the experimental observation that alkali metals promote the ammonia synthesis reaction over Ru catalysts. We also show that the origin of this effect is predominantly a direct electrostatic attraction between the adsorbed alkali atoms and the dissociating molecule.

  12. Polarization and Covalency in Alkali-Tetralide Clusters

    OpenAIRE

    Geertsma, Wiebe

    2002-01-01

    In this paper we discuss the structure of A4M4 alkali(=A)- tetralide (= M) (= group 14) clusters. Without polarization these polyions consist of a central tetralide tetrahedron with each face capped by an alkali ion. We show that ionic polarization can lead to quite different cluster structures by breaking up of the tetralide tetrahedron into pairs M_2, and it can even destroy covalent bonds in these clusters. Consequences for the structure of the solid, liquid and amorphous...

  13. Hydration number of alkali metal ions determined by insertion in a conducting polymer.

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2008-01-01

    In aqueous solutions, the alkali metals ions are associated with a number of H2O molecules. A distinction is made between a primary solvent shell, (or inner solvation shell), consisting of H2O molecules directly coordinated to the metal ion, and a secondary (or outer) solvation shell, consisting of all other water molecules whose properties are still influenced significantly by the cation. Knowing the hydration number is important when considering, for instance, the transport of Na+ and K+ in biological cell membranes, since their different behavior may depend on the details of ion hydration. The solvation of alkali metal ions has been discussed for many years without a clear consensus. This work presents a systematic study of the hydration numbers of the 5 alkali metal ions, using the electrochemical insertion of the ions in a conducting polymer (polypyrrole containing the large immobile anion DBS-). The technique of Electrochemical Quartz Crystal Microbalance (EQCM) has been used to simultaneously determine the mass entering a film of PPy(DBS), and the charge during the first reduction. The method determines the total mass of metal ions and H2O entering the film quite accurately. The charge inserted allows direct calculation of the number of M+ ions entering the film, and therefore the inserted M+ mass. The mass of the water molecules is calculated as a difference. The results yield the following primary hydration numbers: Li+: 5.5-5.6; Na+: 4.0-4.1; K+: 2.0-2.5; Rb+: 0.6-1.2; Cs+: ~0. The most important result is the clear distinction between all the 5 cations, including a clear difference between Na+ and K+. The method is attractive because of the relative simplicity of interpretation – it may also be akin to transport in a cell membrane.

  14. CHEMICAL AND THERMAL STABILITY OF RICE HUSKS AGAINST ALKALI TREATMENT

    Directory of Open Access Journals (Sweden)

    Bwire S. Ndazi

    2008-11-01

    Full Text Available Chemical and thermal stability of rice husks against alkali treatment with 2 to 8% w/v NaOH are presented and discussed in this paper. The thermal stability of the rice husks was examined by using a thermal gravimetric analysis instrument. Chemical stability was evaluated by examining the organic components of rice husks using proximate analysis. The results indicated that the proportion of lignin and hemicellulose in rice husks treated with NaOH ranging from 4 to 8% decreased significantly by 96% and 74%, respectively. The thermal stability and final degradation temperatures of the alkali-treated rice husks were also lowered by 24-26°C due to degradation of hemicellulose and lignin during alkali treatment. Absence of the onset degradation zones in the alkali-treated rice husks was a further indication that hemicellulose and other volatile substances degraded during alkali treatment. This leads to a conclusion that alkali treatment of rice husks with more than 4% NaOH causes a substantial chemical degradation of rice husks, which subsequently decreases their thermal stability.

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

    International Nuclear Information System (INIS)

    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

  16. Ionic interactions in alkali-aluminium tetrafluoride clusters

    International Nuclear Information System (INIS)

    Complex anion structures ((AlF4)-, (AlF5)2- and (AlF6)3-) coexist in liquid mixtures of aluminium trifluoride and alkali fluorides in composition-dependent relative concentrations and are known to interact with the alkali counterions. We present a comparative study of the static and vibrational structures of MAlF4 molecules (with M = any alkali), with the aim of developing and testing a refined model of the ionic interactions for applications to the Al-M fluoride mixtures. We find that, whereas an edge-bridged coordination is strongly favoured for Li in LiAIF4, edge-bridging and face-bridging of the alkali ion become energetically equivalent as one moves from Na to the heavier alkalis. This result is sensitive to the inclusion of alkali polarizability and may be interpreted as implying (for M = K, Rb or Cs) almost free relative rotations of the M+ and (AlF4)- partners at temperatures of relevance to experiment. The consistency of such a viewpoint with electron diffraction data on vapours and with Raman spectra on melts is discussed. (author)

  17. The influence of alkali promoters on coadsorbed molecules

    International Nuclear Information System (INIS)

    A model has been suggested recently based on the results of an extensive study of the coadsorbate system CO + K on Ru(001). It is introduced and discussed in this article based on previous results and on results obtained very recently for a similar coadsorbate system, CO + K/Ni(111). This model is in competition with a variety of differing or similar ideas and interpretations which are mostly based on similar experimental results. Some of these other models postulate a lying-down, or strongly tilted, molecule in the presence of alkali atoms, at least at low coverages. The CO molecule is usually considered to be attached to the substrate and to be closely coadsorbed to the alkali neighbor(s) but sometimes even a vertical or horizontal adsorption on top of the alkali layer has been suggested. The interaction between alkali and CO has been described as indirect via the substrate or direct by forming a ''?''-bond between adjacent alkalis and CO molecules or even by forming an ionic K/sub x/-CO/sub y/ complex. Some authors prefer a model in which the main (or exclusive) interaction comes from a charge transfer from the donating alkali into the 2? orbital of the coadsorbed CO, thus, enhancing the C- metal and reducing the C-O bond strength

  18. Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl3 promoted homocoupling

    Directory of Open Access Journals (Sweden)

    Aiichiro Nagaki

    2011-08-01

    Full Text Available The use of FeCl3 resulted in a fast homocoupling of aryllithiums, and this enabled its integration with the halogen–lithium exchange reaction of aryl halides in a flow microreactor. This system allows the homocoupling of two aryl halides bearing electrophilic functional groups, such as CN and NO2, in under a minute.

  19. Alkali and heavy metal emissions of the PCFB-process; Alkali- ja raskasmetallipaeaestoet PCFB-prosessista

    Energy Technology Data Exchange (ETDEWEB)

    Kuivalainen, R.; Eriksson, T.; Lehtonen, P. [Foster Wheeler Energia Oy, Karhula (Finland)

    1997-10-01

    Pressurized Circulating Fluidized Bed (PCFB) combustion technology has been developed in Karhula R and D Center since 1986. As part of the development, 10 MW PCFB test facility was built in 1989. The test facility has been used for performance testing with different coal types through the years 1990-1995 in order to gain data for design and commercialization of the high-efficiency low-emission PCFB combustion technology. The main object of the project was to measure vapor phase Na and K concentrations in the PCFB flue gas after hot gas filter and investigate the effects of process conditions and sorbents on alkali release. The measurements were performed using plasma assisted method of TUT Laboratory of Plasma Technology and wet absorption method of VTT Energy. The measurements were carried out during three test campaigns at PCFB Test Facility in Karhula. In autumn 1995 both VTT and TUT methods were used. The measurements of the following test period in spring 1996 were performed by VTT, and during the last test segment in autumn 1996 TUT method was in use. During the last test period, the TUT instrument was used as semi-continuous (3 values/minute) alkali analyzer for part of the time. The measured Na concentrations were below 30 ppb(w) in all measured data points. The results of K were below 10 ppb(w). The accuracies of the both methods are about +50 % at this concentration range. The scatter of the data covers the effects of different process variables on the alkali emission. The measured emissions are at the same order of magnitude as the guideline emission limits estimated by gas turbine manufacturers

  20. BEDT-TTF based organic conductors with metal-halide/pseudohalide anions

    International Nuclear Information System (INIS)

    To date, three ?-(ET)2X salts (X- = Cu(NCS)2-, I3- and Ag(CN)2-·H2O) and four other ?-like salts [(ET)4Hg3X8, X- = Cl-, Br-; (MDT-TTF)2AuI2, and (MT)2Au(CN)2] have been reported. Among these seven compounds, five of them are superconductors either under ambient or applied pressure. More than half of these compounds contain polymeric anions. Except the triiodide salt, all the aformentioned anions consist of group IB or IIB metals with halides (Cl-, Br-, I-) pseudo halides (CN-, SCN-) ligands. The authors have explored the electrocrystallization of ET donor molecules with group IB, IIB and other metal halide or pseudohalide anions. The synthesis, conductivities, and ESR properties of the results ET salts are presented

  1. Molecular tunnelling ionization of allyl halides induced by phase-controlled two-colour laser fields

    International Nuclear Information System (INIS)

    We have investigated the molecular tunnelling ionization (TI) of four allyl halide molecules (C3H5X; X = F, Cl, Br, I) induced by phase-controlled two-colour laser fields consisting of a fundamental light and a second-harmonic light with a pulse duration of 130 fs and an intensity of 1012–1013 W cm?2. The geometric structure of the highest occupied molecular orbital (HOMO) of the four allyl halides can be systematically changed by replacing the halogen atom. We observed phase-dependent orientation-selective molecular ionization in the four methyl halide molecules. The mechanism of molecular TI is discussed in connection with the geometric structure of the HOMO. (paper)

  2. Low-temperature magnetic circular dichroism spectra of thin layers of copper and silver halides

    International Nuclear Information System (INIS)

    The electronic and magnetic circular dichroism spectra of thin layers of Cu1 and Ag1 halides have beem measured at low ( about10 K) temperatures. The med spectra show clear A-terms which, in the case of the silver halides and for one band of cuprous iodide, have unexpected negative signs. A qualitative theoretical interpretation of these signs has been attempted by considering halogen-p and metals/d atomic orbital mixing within the framework of a simple, tight-binding model. Reasonable agreement of theory with experiment has been achieved for the positive copper halide A-terms, but it has not proved possible to obtain by calculation the experimentally observed negative A-term sign of the silver salts and cuprous iodide

  3. Fundamental study on alkali metal thermoelectric converter

    International Nuclear Information System (INIS)

    The alkali metal thermoelectric converter (AMTEC) utilizing the sodium ion conducting ?''-alumina is a device to convert heat energy to electric energy directly. In this paper, the results of theoretical and experimental studies on AMTEC power generating characteristics, internal electrical resistances of single cell, and system analysis of AMTEC power generating systems are reported. This paper consists of 5 chapters, which are summarized as follows: In chapter 1, a theoretical explanation of AMTEC, a brief survey of the research and development history of AMTEC and a purpose of this paper are reported. In chapter 2, the properties of ?''-alumina, preparations of thin film electrodes, and special attention points to be paid in handling of ?''-alumina and film electrodes are reported. The AMTEC power generating characteristics of the tubular cells are also reported. In chapter 3, the experimental results of the disk type cells and the theoretical considerations about internal resistances are reported. The causes of electrode erosion are also reported. In chapter 4, the system analysis on AMTEC steam-turbine combined cycle for a dispersed power station and AMTEC power system for a aerospace power are reported. Chapter 5 summarizes major results achieved in the preceding four chapters as a concluding remark. (J.P.N.) 62 refs

  4. Alternative alkali resistant deNOx catalysts

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Kristensen, Steffen Buus

    2012-01-01

    Alternative alkali resistant deNOx catalysts were prepared using three different supports ZrO2, TiO2 and Mordenite zeolite. The majority of the catalysts were prepared by incipient wetness impregnation of a commercial support, with vanadium, copper or iron precursor, one catalyst was prepared by onepot sol–gel method. All catalysts were characterized by BET, XRPD and NH3-TPD. Initial SCR activities of 8 out of 9 catalysts showed higher NO conversion at least at one temperature in the temperature range 300–500 ?C compared to the conventional V2O5-WO3/TiO2 catalyst. After potassium poisoning (100–130 µmol of K/g of catalyst) the relative drop in SCR activity and acidity was lower for all the alternative catalysts compared to the industrial V2O5-WO3/TiO2 catalyst. Furthermore, Cu/MOR and Nano-V2O5/Sul-TiO2 catalysts showed 8–16 times higher SCR activities than the conventional even after high potassium doping (250 and 280 µmol of K/g, respectively). The increased poisoning resistance was due to high substrate acidity (sulphated, heteropoly acid promoted and zeolite supports), substituting the active species of the catalyst (other than vanadium species, i.e. Cu, Fe) and new catalyst synthesis methods (Nano-V2O5/Sul-TiO2 catalyst prepared by sol–gel method).

  5. Magnetoelectric Jones spectroscopy of alkali atoms

    International Nuclear Information System (INIS)

    The Jones effect in a medium of free atoms exposed to static electric and magnetic fields is a useful tool for determining details of an atomic structure. For atoms in their nS ground states irradiated by a monochromatic wave in resonance with a single-photon transition to an n' D state, the bilinear Jones effect is not shaded by the quadratic Kerr and Cotton-Mouton effects, nor by the linear in magnetic field Faraday effect. The position and shape of the amplitude resonance may provide information on spectroscopic properties of atomic levels. We generalize equations for the Jones-effect amplitude to the case of a doublet structure of energy levels and calculate corresponding parameters for alkali atoms. General equations are derived for the amplitude dependence on the relative orientation of the static electric and magnetic fields and on the angle between the static field and the major axis of the wave polarization vector. These equations demonstrate explicitly that the three bilinear-in-static-fields optical birefringence effects-(i) the Jones birefringence (in parallel fields), (ii) the linear birefringence and (iii) the directional birefringence (the last two in perpendicular fields)-correspond to particular cases of the bilinear-in-static-fields correction to the amplitude of Rayleigh forward scattering

  6. Shock barometer using cathodoluminescence of alkali feldspar

    Science.gov (United States)

    Kayama, Masahiro; Nishido, Hirotsugu; Sekine, Toshimori; Nakazato, Tadahiro; Gucsik, Arnold; Ninagawa, Kiyotaka

    2012-09-01

    Color cathodoluminescence (CL) images of unshocked and experimentally shocked sanidine at pressures up to 40.1 GPa showed red-violet emission below 20.0 GPa and blue emission above 20.0 GPa. The phases in these shock-recovered samples were identified as crystalline feldspar for red-violet emitting areas and as diaplectic feldspar glass for blue emitting ones by micro-Raman spectroscopy. CL spectra of these shocked sanidine have emissions at ˜330, ˜380 and 400-420 nm of which intensities increase with an increase in shock pressure. Similar UV-blue emissions were found in alkali feldspar and the glass in Martian meteorites and Ries crater impactite. The deconvolution of these CL spectra provides the emission component at 2.948 eV assigned to shock-induced defect center, where this intensity correlates linearly with peak shock-induced pressure on sanidine, with little dependence on composition and structure. The correlation gives quantitative values of the shock pressures experienced by the feldspar, resulting in estimated shock pressures of Martian meteorites and Ries crater impactite. The CL intensity of feldspar has a potential for a universal shock barometer with high spatial resolution (˜1 ?m) and in a wide pressure range (theoretically ˜4.5-40.1 GPa). This leads to a breakthrough in understanding the impact histories on Earth, Moon, and Mars.

  7. Alkali-aggregate reactivity of typical siliceious glass and carbonate rocks in alkali-activated fly ash based geopolymers

    Science.gov (United States)

    Lu, Duyou; Liu, Yongdao; Zheng, Yanzeng; Xu, Zhongzi; Shen, Xiaodong

    2013-08-01

    For exploring the behaviour of alkali-aggregate reactivity (AAR) in alkali-activated geopolymeric materials and assessing the procedures for testing AAR in geopolymers, the expansion behaviour of fly ash based geopolymer mortars with pure silica glass and typical carbonate rocks were studied respectively by curing at various conditions, i.e. 23°C and 38°C with relative humidity over 95%, immersed in 1M NaOH solution at 80°C. Results show that, at various curing conditions, neither harmful ASR nor harmful ACR was observed in geopolymers with the criteria specified for OPC system. However, with the change of curing conditions, the geopolymer binder and reactive aggregates may experience different reaction processes leading to quite different dimensional changes, especially with additional alkalis and elevated temperatures. It suggests that high temperature with additional alkali for accelerating AAR in traditional OPC system may not appropriate for assessing the alkali-aggregate reactivity behaviour in geopolymers designed for normal conditions. On the other hand, it is hopeful to control the dimensional change of geopolymer mortar or concrete by selecting the type of aggregates and the appropriate curing conditions, thus changing the harmful AAR in OPC into beneficial AAR in geopolymers and other alkali-activated cementitious systems.

  8. Improvements in pulp properties by alkali preextraction and subsequent kraft pulping with controlling H-factor and alkali charge

    Directory of Open Access Journals (Sweden)

    Kyujeong Sim

    2012-11-01

    Full Text Available The objective of this study was to determine the processing conditions for obtaining improved pulp properties from the kraft pulping process with an alkali pre-extraction stage. Before the kraft pulping, a pre-extraction of hemicelluloses from mixed hardwood chips was performed with two different alkali concentrations (3% and 12% as Na2O at 150 °C for 90 minutes. The kraft pulping of the pre-extracted chips was then conducted in two ways: with either the H-factor alone controlled or with both the H-factor and the alkali charge controlled. When the chips were pre-extracted with the 3% alkali charge and with the kraft pulping controlled to an H-factor of 500, the yield and properties of the pulp were higher than those of the reference kraft pulp. The 12% alkali pre-extraction and kraft pulping resulted in a low yield of screened pulp. However, when the alkali charge and the H-factor were adjusted together, the pulp yield remained constant and the pulp properties improved in comparison to the reference pulp for both the 3 and 12% cases.

  9. New observations on the mechanism of lithium nitrate against alkali silica reaction (ASR)

    International Nuclear Information System (INIS)

    In the current study, in order to elucidate the mechanisms for the favorable effects of lithium nitrate in controlling alkali silica reaction (ASR), vycor glass disk immersion specimens and glass disk-cement paste sandwich specimens were prepared and examined by XRD, SEM and Laser Ablation Induction Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results showed that when glass disk was immersed in only NaOH solution, the glass was attacked by hydroxyl ions but no solid reaction product was found, thus the presence of calcium was essential for the formation of ASR gel. In the presence of lithium, the glass surface was covered by a thick layer of Li-Si crystal. With the addition of Ca(OH)2, the glass surface was completely covered by Li-Si crystal and a lithium-bearing low Ca-Na-(K)-Si gel. These two phases either form a dense matrix with Li-Si crystal serving as the framework, and the gel filling in the void space, or the Li-Si crystal serving as the foundation to completely cover the entire reactive SiO2 surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO3 were attributed to the formation of a layer of Li-Si crystals intimately at the reactive SiO2 particle surface and the formation of Li-bearing low-Ca ASR gel products. The Li-bearing low-Ca ASR gels may have a dense and rigid structure, thus having low capacity to absorb moisture from the surrounding paste, and exhibiting a m the surrounding paste, and exhibiting a non-swelling property.

  10. Structural and computational studies of geometric isomers of 2-(4-methoxystyryl)-1,3-benzothiazole and preparation of their complexes with zinc halides

    Science.gov (United States)

    ?akovi?, Marijana; ?i?ak, Helena; Soldin, Željka; Trali?-Kulenovi?, Vesna

    2009-12-01

    The 2-(4-methoxystyryl)-1,3-benzothiazole (MeO-sbt) and its complexes with zinc halides of general formula [ZnX 2(MeO-sbt) 2], X = Cl, Br, I, are prepared. Crystal structure of both geometric isomers cis-2-(4-methoxystyryl)-1,3-benzothiazole 1a and trans-2-(4-methoxystyryl)-1,3-benzothiazole 1b are reported. Optimized structures of isomers 1a and 1b are consistent with X-ray structures. By comparison of calculated and experimental IR spectra as well as experimental NMR data it has been concluded that trans-isomer 1b was initial product. Quantum-mechanical calculations have shown that thermal isomerization in the singlet ground state is not possible at room temperature, but isomerization could be initiated by high temperature or photochemically which had not been studied in this work.

  11. Ionic conductivity of N-alkyl pyridinium halides mesophases

    International Nuclear Information System (INIS)

    The quasi anhydrous N-alkyl pyridinium halides undergo at a temperature Tc a phase transition from a crystalline isolating state to a conducting mesophase (? = 3.10-2 ?-1cm-1). The transition temperature depends on the nature on counter-ion and on the aliphatic chain length. The present study is devoted to the N-alkyl pyridinium chlorides, bromides and iodides varying the number of carbon atoms in the chain from ten to twenty two. The transition temperatures Tc were found to increase from 30 deg. C up to 110 deg. C by a step of 10 deg. C for two added carbon atoms in the chain. The electrical measurements have shown that the conductivity of the mesophases which is ionic in origin is due to a large mobility of counter-ions in hydrophilic parts. At high frequencies (F > 103 Hz) ionic conductivity predominates in the bulk and does not depend on frequency. At low frequencies (F 3 Hz) the most important are interface phenomena depending on the square root of inverse frequency (?-1/2) and being due to an electronic exchange limited by diffusion velocity of counter-ions. The electrical conductivity depends weekly on the chain length and the mesophases textures. The most conducting mesophase is the optically isotropic. The conductivity increases with increasing water content of the system and decreases with increasing atomic number of counter-ion. The diffusion measurements by radioactive tracers confirm the ionic character of charge carriers although the diffusion factors obtained by this method are largely higher than the calculated ones from the conductivity values. (author)

  12. The electronic structure of thorium halides predicted by HSE and GW

    Science.gov (United States)

    Ellis, Jason; Wen, Xiaodong; Martin, Richard

    2014-03-01

    Recently, there has been a significant experimental push to measuring the VUV nuclear excitation of 229Th using optical spectroscopy. Large band gap Thorium halides such as ThF4 and Na2ThF6 have been suggested as candidate materials for studying this nuclear transition, as they are transparent to the relevant optical frequencies. In this work, we compare the many body GW approach, hybrid density functional theory, and local density approximation calculations of the electronic structure of these materials, as well as the rest of the binary thorium halides (ThX4, X=Cl,Br,I).

  13. Lasers based on metal vapors and their halides. Lazery na parakh metallov i ikh galogenidov

    Energy Technology Data Exchange (ETDEWEB)

    Petrash, G.G.

    1987-01-01

    The papers presented in this volume contain results of experimental studies of the physical processes occurring in lasers based on metal vapors and their halides. Various implementations of electrical schemes for the pulsed power supply to active media are examined; the thermal conditions of the operation of self-heating lasers are investigated in a systematic manner. Data on the spectral and temporal characteristics of the emission of pulsed lasers based on metals and copper halides are presented. The physical processes limiting the service life of lasers based on copper bromide vapors are discussed.

  14. New mechanism for glomerular injury. Myeloperoxidase-hydrogen peroxide-halide system.

    OpenAIRE

    Johnson, R. J.; Couser, W G; Chi, E Y; Adler, S.; Klebanoff, S. J.

    1987-01-01

    Reactive oxygen species, particularly hydrogen peroxide (H2O2), participate in neutrophil-mediated glomerulonephritis. However, the mechanism of H2O2 neptrotoxicity is unknown. Myeloperoxidase (MPO), a neutrophil cationic enzyme that localizes in glomeruli, can react with H2O2 and halides to form highly reactive products. We tested the hypothesis that the MPO-H2O2-halide system may induce glomerular injury by infusing MPO followed by H2O2 in a chloride-containing solution into the renal arter...

  15. Interactions and low energy collisions between an alkali ion and an alkali atom of different nucleus

    CERN Document Server

    Rakshit, Arpita; Berriche, Hamid; Deb, Bimalendu

    2015-01-01

    We study theoretically interaction potentials and low energy collisions between different alkali atoms and alkali ions. Specifically, we consider systems like X + Y$^{+}$, where X(Y$^{+})$ is either Li(Cs$^+$) or Cs((Li$^+$), Na(Cs$^+$) or Cs(Na$^+$) and Li(Rb$^+$) or Rb(Li$^+$). We calculate the molecular potentials of the ground and first two excited states of these three systems using pseudopotential method and compare our results with those obtained by others. We calculate ground-state scattering wave functions and cross sections of these systems for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order $1$ K, one needs to take into account at least 60 partial waves. In the low energy limit ($< 1 \\mu$K), elastic scattering cross sections exhibit Wigner law threshold behavior while in the high energy limit the cross sections go as $E^{-1/3}$. We discuss qualitatively the possibilities of forming cold molecular ion by ...

  16. Alkali norite, troctolites, and VHK mare basalts from breccia 14304

    Science.gov (United States)

    Goodrich, Cyrena Anne; Taylor, G. Jeffrey; Keil, Klaus; Kallemeyn, Gregory W.; Warren, Paul H.

    1986-09-01

    Twelve clasts were separated from breccia 14304 for consortium study: six pristine highlands rocks, two mare basalts, and four nonpristine highlands rocks. The pristine highlands rocks include representatives of the magnesian troctolite-anorthosite and alkali suites, the two most common subgroups of the Mg suite found at the Apollo 14 site. Two troctolite clasts have olivine (~Fo 90) and plagioclase (~An 94) compositions similar to one group of Apolo 14 troctolites. One also contains spinel (Mg' 66-85). Incompatible element abundances in one are similar to those of 14305 troctolites, although the HREE (heavy rare earth elements) pattern is distinct among Apollo 14 troctolites. A dunite clast (~Fo 89) may be an unrepresentative piece of a troctolite. Alkali lithologies include an alkali anorthosite and an alkali norite, which is a rock type not previously described. The alkali norite has a pristine igneous texture and contains inverted pigeonite (Mg' 64), plagioclase (An82), K-feldspar, ternary feldspar, REE-rich phosphates, and silica. It resembles alkali gabbronorites from Apollo 14 and 67975 in mineralogy and mineral compositions. Alkali lithologies and phosphate-bearing magnesian anorthosites from Apollo 14 may have formed from Mg-rich magmas that assimilated various amounts of material rich in P and REE. This material could be a fractionated derivative of urKREEP. another pristine clast from 14304 is an Mg-gabbronorite. The two mare basalt clasts are very high potassium (VHK) basalts. They have 4 mg/g K and K/La ratios of 580 and 700. The parent magmas of VHK basalts could have formed from typical low-Ti, high-Al basaltic magmas by assimilation of K-rich material. This material could also be a fractionated derivative or urKREEP. Nonpristine 14304 clasts include melt-textured anorthosites and an augite-rich poikilitic melt rock. The latter is probably polymict, but its major component must be an Mg-suite gabbro.

  17. Intrinsic luminescence of alkali metal sulphates

    International Nuclear Information System (INIS)

    Full text: The information on research of intrinsic radiation of Na2SO4 crystal in the literature misses, as well as the information on breadth of a band the forbidden energies. We in pure Na2SO4 crystal and Na2SO4:Tl crystal measure spectra of making of peaks thermoluminescence (TL) 120 K, 240 K and 430 K at an irradiation by identical number of quanta in the field of a vacuum ultraviolet. Making of all three peaks TL begins with of energy of quanta 8.8 eV, and sharp propagation of storage light sum begins with energies 8.9-9 eV to what propagation of counting rate TL testifies. Spectra of making of TL peaks were measured as follows: the crystals at temperature of liquid nitrogen is irradiated with identical amount of quanta of various energies in an interval 6-11 eV with a step 0.1-0.3 eV at exposure time of 20 minutes in each point. After an irradiation in each point TL spectrum is measured at constant speed of a heating 0.18 K/s. In an interval of temperatures 80-500 K. On intensity in TL peaks and its functional connection from energy of quanta by which the irradiation was made, are under construction the graph of a spectrum of making. We guess, that low-temperature TL peaks 120 K and 240 K in Na2SO4 are related to a delocalization of electron defects at the moment of polymorphic transferring. Thus, as well as in crystal K2SO4, at energies of quantum 8.9-O4, at energies of quantum 8.9-9 eV in Na2SO4 there are separate electron-hole pairs, i.e. the breadth of a forbidden band of this crystal makes 8.8-9 eV. At the following stage we explored a spectrum of initiation of an intra-centric luminescence of impurity Tl+ in Na2SO4:Tl and a intrinsic luminescence of clear crystal Na2SO4. At initiation of object by UV radiation (6-12 eV) the spectrum of initiation of intra-centric luminescence of Tl in Na2SO4:Tl has been measured at 300 and 80 K. Radiation of Tl (4.2 eV) precipitated out light filter UFS-5. According to the obtained data the intra-centric luminescence of impurity Tl in Na2S04:Tl in fundamental spectral range is not raised. Luminescence of Tl is efficiently raised in the field of transparence of crystal Na2SO4. The excitation band has a maximum 7.5 eV at 300 K and 7.7 eV at 80 K. At excitation by UV radiation (6-12 eV) the spectrum of excitation of clear crystal Na2SO4 is measured at 300 and 80 K. Intrinsic radiation of crystal Na2SO4 at 3.8-4 eV is efficiently raised in fundamental absorption band. It confirms that radiation 3.8-4.0 eV results from recombination of electrons with the auto-localized electron defects

  18. Tuning the coordination geometries and magnetic dynamics of [Ln(hfac)4](-) through alkali metal counterions.

    Science.gov (United States)

    Zeng, Dai; Ren, Min; Bao, Song-Song; Zheng, Li-Min

    2014-01-21

    Four lanthanide compounds with formulas [Cs{Dy(hfac)4}] (1), [Cs{Er(hfac)4}] (2), [K{Dy(hfac)4}] (3), and [K{Er(hfac)4}] (4) (hfac = hexafluoroacetylacetone) are reported. Compounds 1 and 2 crystallize in the orthorhombic Pbcn space group, while 3 and 4 are in the triclinic P1? space group. All display chain structures in which the mononuclear [Ln(hfac)4](-) anions are linked by alkali metal ions. However, the coordination geometries around the Ln atoms are quite different depending on the cation. They adopt a distorted dodecahedron with pseudo-D2d symmetry in the cesium compounds 1 and 2, while a distorted square-antiprism with pseudo-D4d symmetry is adopted in the potassium compounds 3 and 4. The latter compounds show distinct field-induced slow magnetization relaxation. The energy barriers are 23.95 and 20.21 K for compounds 3 and 4, respectively. PMID:24393012

  19. Modelling Of Monazite Ore Break-Down By Alkali Process Spectrometry

    International Nuclear Information System (INIS)

    A computer modelling has been developed for the calculation of mass balance of monazite ore break-down by alkali process at Rare Earth Research and Development Center. The process includes the following units : ore digestion by concentrate NaOH, dissolution of digested ore by HCl, uranium and thorium precipitation and crystallization of Na3PO4 which is by-product from this process. The model named RRDCMBP was prepared in Visual Basic language. The modelling program can be run on personal computer and it is interactive and easy to use. User is able to choose any equipment in each unit process and input data to get output of mass balance results. The model could be helpful in the process analysis for the further process adjustment and development

  20. Mechanistic insights into solubilization of rice protein isolates by freeze-milling combined with alkali pretreatment.

    Science.gov (United States)

    Wang, Tao; Zhang, Hao; Wang, Li; Wang, Ren; Chen, Zhengxing

    2015-07-01

    The solubilization of rice protein isolates (RPIs) has been regarded as one of the critical and challenging processes affecting commercial availability. Simultaneous treatment with freezing and milling (freeze-milling) combined with alkali pretreatment can remarkably increase the maximum achievable amounts of soluble RPIs by up to 42 times. This study investigates the mechanism of solubilization of RPIs by freeze-milling (RPI(fm)). Structural analyses reveal that milling causes proteins to unfold with ice crystals formed inside protein bodies. Fluorescent and Fourier transform infrared spectra show that RPI(fm) possesses disrupted hydrophobic surface and exposed hydrophilic inner groups. Size exclusion chromatography results reveal that RPI(fm) exhibits disaggregation and strong water-protein interactions. These results indicate that freeze-milling may be a promising manufacturing technique in food industry. PMID:25704687

  1. Spectroscopic investigation of indium halides as substitudes of mercury in low pressure discharges for lighting applications

    International Nuclear Information System (INIS)

    Low pressure discharges with indium halides as radiator are discussed as substitutes for hazardous mercury in conventional fluorescent lamps. In this work, the applicability of InBr and InCl in a low pressure discharge light source is investigated. The aim is to identify and understand the physical processes which determine the discharge characteristics and the efficiency of the generated near-UV emission of the indium halide molecule and of the indium atom which is created due to dissociation processes in the plasma. As discharge vessels sealed cylindrical quartz glass tubes which contain a defined amount of indium halide and a rare gas are used. Preliminary investigations showed that for a controlled variation of the indium halide density a well-defined cold spot setup is mandatory. This was realized in the utilized experimental setup. The use of metal halides raises the issue, that power coupling by internal electrodes is not possible as the electrodes would quickly be eroded by the halides. The comparison of inductive and capacitive RF-coupling with external electrodes revealed that inductively coupled discharges provide higher light output and much better long term stability. Therefore, all investigations are carried out using inductive RF-coupling. The diagnostic methods optical emission and white light absorption spectroscopy are applied. As the effects of absorption-signal saturation and reabsorption of emitted radiation within the plasma volume could lead to an underestimation of the determined population densities by orders of magnitude, these effects are considered in the data evaluation. In order to determine the electron temperature and the electron density from spectroscopic measurements, an extended corona model as population model of the indium atom has been set up. A simulation of the molecular emission spectra has been implemented to investigate the rovibrational population processes of the indium halide molecules. The impact of the cold spot temperature, the RF-power and the background gas type on the discharge characteristics is investigated for rare gas plasmas containing InBr or InCl. Varying the cold spot temperature yields a maximum efficiency around 210 to 230 degrees centigrade. At low cold spot temperatures the efficiency drops due to a too low indium halide density whereas reabsorption of emitted indium halide and indium photons limits the efficiency at high cold spot temperatures. Reducing the RF-power increases the discharge efficiency as the effect of reabsorption of the generated radiation is reduced. The utilized background gas does not influence the maximum efficiency as the discharge characteristics is solely determined by indium in the relevant cold spot temperature range. As reabsorption effects of the indium radiation are smaller with InCl, the highest efficiency of 24 per cent was obtained at a cold spot temperature of 230 degrees centigrade (40 W power, discharge vessel filled with 1 mbar argon and 1.5 mg InCl). The potential of a low pressure indium halide discharge light source has been demonstrated by simulating the application of phosphors which yields an efficacy of about 60 lm/W. The feasibility of applying low pressure indium halide discharges for lighting purposes has been discussed by outlining a lamp prototype.

  2. Fabrication of large-volume, low-cost ceramic lanthanum halide scintillators for gamma ray detection : final report for DHS/DNDO/TRDD project TA-01-SL01.

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, Timothy J.; Ottley, Leigh Anna M.; Yang, Pin; Chen, Ching-Fong; Sanchez, Margaret R.; Bell, Nelson Simmons

    2008-10-01

    This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr{sub 3} ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr{sub 3} is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable.

  3. The role of NH3 and hydrocarbon mixtures in GaN pseudo-halide CVD: a quantum chemical study.

    Science.gov (United States)

    Gadzhiev, Oleg B; Sennikov, Peter G; Petrov, Alexander I; Kachel, Krzysztof; Golka, Sebastian; Gogova, Daniela; Siche, Dietmar

    2014-11-01

    The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons-NH3-Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located ?-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. PMID:25316343

  4. Olivine + halides: a recipe for iron mobilization in volcanic ash?

    Science.gov (United States)

    Hoshyaripour, G.; Hort, M. K.; Langmann, B.

    2013-12-01

    During the last decade, scientific evidences strongly suggest that volcanic ash iron has fertilization impact upon the surface ocean. Still, it is not well constrained how the insoluble iron in ash (i.e., as a component in minerals and also glass) could be mobilized during volcanic eruptions and atmospheric transport. Here we investigate the volcanic plume controls on ash iron solubility. We develope a conceptual box model to simulate the high, mid and low temperature chemical, physical and thermodynamic processes in eruption plumes to better constrain the iron mobilization in volcanic ash. We take into account the interaction of different species in a solid-liquid-gas system representing various volcanic settings (convergent plate, divergent plate and hot spot). Results show that the hot core of a volcanic plume (T>600°C) does not produce soluble iron directly but significantly controls the Fe mineralogy and oxidation state at the ash surface. The final iron mineralogy at the ash surface (i.e. the ash's oxidation front with 1-100 nm thickness) is likely to be independent of temperature and oxygen fugacity and is closely correlated to the ratio of H2 and H2S content of the magmatic gas to the amount of entrained oxygen. As the plume continues rising and cooling, sulfuric acid condenses at about 150°C followed by water condensation at about 50°C which also dissociates sulfuric acid and produces H+ ions in the liquid phase. The aqueous phase scavenges the surrounding gas species (e.g. SO2, HCl, HF) and concurrently dissolves the ash surface constituents. Since HCl is about 4 orders of magnitudes more soluble than SO2, its dissolution mainly controls the pH of the liquid. Hence, high HCl concentrations in the gas phase results in lower pH in the aqueous phase (pHfayalite) show a much higher dissolution rate in comparison with oxidized species (e.g. hematite). Thus, the presence of the reduced iron species in the mineral assemblage seems to be more favorable for the soluble iron production. We conclude that bio-available iron production is weakly correlated with the tectonic setting and is instead controlled by the halide content of the eruption plume and the oxidation state of the iron at the ash mineral assemblage (e.g. presence of olivine). This hypothesis could satisfactorily explain the extraordinary iron release from the ash of Hekla eruption in 2000 and also the fertilization impact caused by the ash erupted from Kasatochi in 2008.

  5. The Chemical Effects of Nuclear Transformations in the Alkali Chlorides: Pt. I. Factors Determining the Behaviour of the S35

    International Nuclear Information System (INIS)

    The most favourable systems in which it may be hoped that the detailed relation between dislocations, point defects and the chemical changes accompanying, and subsequent to, nuclear reactions can be established are the simplest ionic solids. The simple crystal structures of the alkali chlorides and the considerable body of physical data on defects in these crystals makes them especially suitable to such studies. A number of nuclear reactions can be examined in such systems; we have chosen to study the Cl35(n, p)S35 reactions. In this paper we present a survey of the main features of the behaviour of the S35. If the crystals of the irradiated alkali chloride are analysed by dissolving in water containing sulphide and sulphate carriers, the S35 is found distributed between the two fractions. The stability of the fraction S35 which precipitates with the sulphide carrier decreases down the alkali metal series from sodium to caesium. In sodium chloride the sulphide fraction is stable at 300°C, unaffected by a pressure of 2000 atm, or by crushing of the crystals. The same fraction in potassium, rubidium and caesium chlorides is oxidized at 180°C, so that after several hours heating practically all the S35 precipitates with the sulphate fraction. The sulphide fraction in caesium chloride is also susceptible to oxidation by crushing. Crystals of sodium and potassium chlorides bombarded with 2 MeV electrons in doses varying from 0.1 to 150 Mrad prior to neutron irradiation, all show a great increase in the proportion of S35 precipitating as sulphide. In sodium chloride more than 90% precipitates as sulphide at a dose of 50 Mrad. An increase is also seen when sodium chloride crystals are enriched with sodium by heating in the metal vapour, and when small amounts of divalent calcium and cadmium are introduced into potassium chloride crystals. All these three treatments involve the introduction of defects into the crystal lattice, so these are presumed to play a determining role in the final state of the S35 produced. The sulphide fraction present in electron-bombarded crystals, and crystals containing divalent substituted ions, is less stable than the same fraction in untreated crystals. The crystals become coloured on neutron irradiation due to the formation of F and V centres. If the centres are bleached by heat or exposure to daylight a small increase in the sulphide fraction is seen in sodium and rubidium chlorides. Vacuum outgassing of crystals before neutron irradiation seems to have no effect on the proportion of sulphide found. A preliminary interpretation of the data is given and it is shown that there is no necessity to invoke improbably highly positively charged sulphur species. (author)

  6. Reference spectroscopic data for hydrogen halides, Part II: The line lists

    International Nuclear Information System (INIS)

    Accurate spectroscopic parameters for the hydrogen halides, namely HF, HCl, HBr, and HI, together with their deuterated isotopologues, are crucial for the quantitative study of terrestrial and planetary atmospheres, astrophysical objects, and chemical lasers. A thorough evaluation of all the hydrogen halide line parameters in previous HITRAN editions has been carried out. A new set of line lists was generated for the HITRAN2012 edition using methods described here. In total, 131,798 entries were generated for numerous pure-rotational and ro-vibrational transitions (fundamental, overtone, and hot bands) for hydrogen halides and their deuterated species in a standard HITRAN 160-character format. Data for the deuterated isotopologues have been entered into HITRAN for the first time. The calculations employ the recently developed semi-empirical dipole moment functions [Li G, et al. J Quant Spectrosc Radiat Transfer 2013;121:78–90] and very accurate analytical potential energy functions and associated functions characterizing Born–Oppenheimer breakdown effects. Line-shape parameters have also been updated using the most recent available experimental and theoretical studies. Comparison with the previous HITRAN compilation has shown significant improvements. -- Highlights: • Significant improvements of line positions and intensities of hydrogen halides. • Extended ro-vibrational range for non-LTE applications. • First time inclusion of the deuterated species, DF, DCl, DBr and DI in HITRAN. • Updated line-shape parameters

  7. Shape evolution and single particle luminescence of organometal halide perovskite nanocrystals.

    Science.gov (United States)

    Zhu, Feng; Men, Long; Guo, Yijun; Zhu, Qiaochu; Bhattacharjee, Ujjal; Goodwin, Peter M; Petrich, Jacob W; Smith, Emily A; Vela, Javier

    2015-03-24

    Organometallic halide perovskites CH3NH3PbX3 (X = I, Br, Cl) have quickly become one of the most promising semiconductors for solar cells, with photovoltaics made of these materials reaching power conversion efficiencies of near 20%. Improving our ability to harness the full potential of organometal halide perovskites will require more controllable syntheses that permit a detailed understanding of their fundamental chemistry and photophysics. In this manuscript, we systematically synthesize CH3NH3PbX3 (X = I, Br) nanocrystals with different morphologies (dots, rods, plates or sheets) by using different solvents and capping ligands. CH3NH3PbX3 nanowires and nanorods capped with octylammonium halides show relatively higher photoluminescence (PL) quantum yields and long PL lifetimes. CH3NH3PbI3 nanowires monitored at the single particle level show shape-correlated PL emission across whole particles, with little photobleaching observed and very few off periods. This work highlights the potential of low-dimensional organometal halide perovskite semiconductors in constructing new porous and nanostructured solar cell architectures, as well as in applying these materials to other fields such as light-emitting devices and single particle imaging and tracking. PMID:25661423

  8. Iron thiolate complexes: efficient catalysts for coupling alkenyl halides with alkyl Grignard reagents.

    Science.gov (United States)

    Cahiez, Gérard; Gager, Olivier; Buendia, Julien; Patinote, Cindy

    2012-05-01

    Ironing out the kinks: Efficient new catalytic systems based on iron thiolates are described for the iron-catalyzed cross-coupling of alkyl Grignard reagents with alkenyl halides. The reaction is highly chemo- and stereoselective. With this new procedure, the use of N-methylpyrrolidone as a co-solvent is no longer required. PMID:22461150

  9. Correlated linear response calculations of the C6 dispersion coefficients of hydrogen halides.

    Czech Academy of Sciences Publication Activity Database

    Sauer, S. P. A.; Paidarová, Ivana

    2007-01-01

    Ro?. 3, 2-4 (2007), s. 399-421. ISSN 1574-0404 R&D Projects: GA AV ?R IAA401870702 Institutional research plan: CEZ:AV0Z40400503 Keywords : hydrogen halides * C6 dospersion coefficients * van der Waals coefficients * polarizability at imaginary frequences * SOPPA Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Electrophosphorescence from hole-transporting layer doped with cerium halide nano-particles

    International Nuclear Information System (INIS)

    Hybrid films of hole-transporting compounds embedded with cerium halides nano-particles were successfully prepared by simultaneous vacuum deposition of hole-transporting compounds and cerium halides. From observation by transmission electron microscopy, it was confirmed that cerium halides formed spherical nano-particles with diameter of less than 20 nm. The hybrid films exhibited fluorescence by irradiation of ultraviolet light. However, fairly efficient electrophosphorescence was confirmed in the electroluminescence device having the hybrid films as an emissive layer. When the hybrid film of 4,4?-N,N?-dicarbazole-biphenyl doped with cerium iodide nano-particles was used, maximum luminance was 486 cd cm?2, and maximum external quantum efficiency was 0.11%. -- Highlights: • Hybrid films of organic semiconductors and Ce halides were prepared by simple vapor deposition. • PL of the hybrid films is due to fluorescence of organic semiconductors. • EL of the hybrid films is due to phosphorescence of organic semiconductors. • Mechanism of the emission process was qualitatively discussed. • Heavy atom effect was observed in the EL device using the hybrid films as emissive layer

  11. Viabilization of a new aluminium grain refiner based on Zirconium halide salt

    International Nuclear Information System (INIS)

    A new aluminium grain refiner based on Zirconium halide salt is proposed. Its efficiency, as grain refiner is analysed varying the salt amount, the inoculation temperature and holding time. The grain size reduction shows to be dependent on the salt amount and independent on the inoculation temperature. The holding time effects is dependent on the innoculated salt amount. (Author)

  12. FORMATION OF HIGHLY CONDUCTING DERIVATIVES OF POLYACETYLENE THROUGH OXIDATION WITH SELECTED METAL HALIDES

    OpenAIRE

    Billaud, D.; Kulszewicz, I.; Pro_, A.; Bernier, P; Lefrant, S.

    1983-01-01

    Some new metal halides (InCl3, InI3, TiCl4, TiI4, SnCl4, ZrCl4) can oxidize polyacetylene with the formation of highly conducting polymers characterized by elemental analysis, mass uptake and physical methods. Electrical conductivities and EPR spectra are in agreement with the metallic behaviour of these new materials.

  13. Recoil halogen reactions in liquid and frozen aqueous solutions of methyl halides

    International Nuclear Information System (INIS)

    Reactions of recoil 38Cl, 80Br and 128I have been studied in frozen neat systems of methyl chloride, methyl bromide and methyl iodide as well as liquid and frozen aqueous solutions of these methyl halides. In all systems, the major product was the radio-labelled halide ion. There was no evidence for other halogen inorganic species. The major labelled organic product was the parent molecule. Because of different reactivity between organic and aqueous phases, the recoil halogen atoms tracer technique can acquire site information of the methyl halide solutes in the liquid and frozen aqueous systems. For all liquid and frozen systems, the methyl halide molecules tended to aggregate. For liquid systems, the tendency for aggregation diminished as the solute concentration approached zero, where the probable state of the solute approached a monomolecular dispersion. Unlike the liquid state, the frozen ice lattice demonstrated a ''caging effect'' for the solute aggregates which resulted in constant product yields over the whole concentration range. (orig.)

  14. Direct ToF-SIMS analysis of organic halides and amines on TLC plates

    International Nuclear Information System (INIS)

    It has been reported that: 'direct analysis of thin layer chromatography (TLC) plates with secondary ion mass spectrometry (SIMS) yields no satisfactory results' (J. Chromatogr. A 1084 (2005) 113-118). While this statement appears to be true in general, we have identified two important classes of compounds, organic halides and amines, that appear to yield to such direct analyses. For example, five organic halides with diverse structures were eluted on normal phase TLC plates. In all cases the halide signals in the negative ion time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra were notably stronger than the background signals. Similarly, a series of five organic amines with diverse structures were directly analyzed by positive ion ToF-SIMS. In all but one of the spectra characteristic, and sometimes even quasi-molecular ions, were observed. Most likely, the good halide ion yields are largely a function of the electronegativity of the halogens. We also propose that direct analysis of amines on normal phase silica gel is facilitated by the acidity, i.e., proton donation, of surface silanol groups

  15. Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

    Directory of Open Access Journals (Sweden)

    Han Wang

    2012-05-01

    Full Text Available By using ionic liquids as solvents, the chlorination or bromination of unprotected anilines at the para-position can be achieved in high yields with copper halides under mild conditions, without the need for potentially hazardous operations such as supplementing oxygen or gaseous HCl.

  16. Radiation chemistry of hydrocarbon and alkyl halide systems. Progress report, August 1, 1977--August 1, 1978

    International Nuclear Information System (INIS)

    Progress of experimental work is reported on pulse radiolysis of simple alkyl halides in the gas phase, gas phase radiolysis of CHF3-CH3I mixtures, gamma radiolysis of the system CO/H2, and improvements in equipment and facilities

  17. Optimization of power of alkali metal thermo electric convertor

    Science.gov (United States)

    Lodhi, M. A. K.; Ahmad, Nadeem

    2015-02-01

    Alkali Metal Thermo Electric Convertor (AMTEC) uses infrared radiation to knock out electrons from some alkali metal acting as the working material. In the present paper sodium is chosen as the alkali metal. The freed electrons after going through a circuit and having done the prescribed work meet the sodium ions. A solid electrolyte, called beta" alumina solid electrolyte (BASE) is used for diffusing the working material ions. The system is closed and continues working as long as the heat source is kept turned on. The longevity, power and efficiency of the device depend inversely to some extent on the thickness of the electrolyte and electrodes. In this work we have optimized the thickness of electrodes. This optimization improved the efficiency and power output by 28 and 14.8% points respectively.

  18. Characterization of alkali-modified soy protein concentrate

    Directory of Open Access Journals (Sweden)

    Bara? Miroljub B.

    2005-01-01

    Full Text Available To study the influence of the preparation mode, including mild alkali modification, of soy protein concentrate on soluble protein content and composition, some of its nutritive and functional properties were investigated. Soy protein concentrate prepared by aqueous alcohol leaching was modified in mild alkaline solutions (pH 8.0 at 40, 50 and 60° C for 60 minutes and compared with two principal types of commercial soy protein concentrate. Soluble protein content, composition and properties of soy protein concentrate, as well as their potential use are essentially determined by the preparation mode. Limited mild alkali hydrolysis increased protein solubility by 40-71%, while emulsion stability was increased by 18-56%. Major storage soybean proteins exhibited different stability to alcohol denaturation and mild alkali modification. The most susceptible were acidic -A3 - and -A5- subunits of glycinin.

  19. EUV ionization of bare and alkali doped helium nanodroplets

    International Nuclear Information System (INIS)

    He nanodroplets are widely used as a cold and weakly interacting matrix for spectroscopy of embedded species. In this work we excite or ionize the He droplets using synchrotron radiation and study the back action onto the impurity atoms. Using photoelectron-photoion coincidence imaging spectroscopy at variable photon energies (20-25 eV), we compare charge-transfer to Penning ionization of impurities located inside the droplets (rare gases) and those located at the droplet surface (alkali metals). The surprising finding is that alkali metals are very efficiently Penning ionized upon excitation of the 1s2p-band of He droplets, in contrast to rare gases. This speaks for rapid exciton migration to the surface, followed by relaxation and eventually the energy transfer to the alkali impurity.

  20. Design and growth of lead selenoiodide semiconductors crystals for radiation detection

    Science.gov (United States)

    House, David; Singh, N. B.; Arnold, B.; Choa, Fow-Sen; Schreib, B.

    2014-09-01

    We have designed experiments utilizing for achieving desired bandgap resistivity, electron hole-pairs by solid solution materials. A low temperature synthesis, purification and growth to reduce stress and high yield for low defect density crystals of PbI2-PbSe system was developed for low cost large volume high efficiency detectors. This material system can be used for ?-ray detection. The material design is based on the heavy metal halide and selenide solid-solution system. This novel multicomponent crystal involves innovative approach for synthesis, purification and low temperature growth from the melt in modified three- zone Bridgman furnace. Crystals up to 15 mm diameter were grown and cm size slabs were fabricated for evaluation. Our approach for shaped crystal growth previously used for crystal is an exciting approach to increase the yield and further reduce the fabrication cost. Preliminary results show high resistivity and large crystal growth feasibility for crystals using parent components.

  1. Feasibility of supersonic diode pumped alkali lasers: Model calculations

    International Nuclear Information System (INIS)

    The feasibility of supersonic operation of diode pumped alkali lasers (DPALs) is studied for Cs and K atoms applying model calculations, based on a semi-analytical model previously used for studying static and subsonic flow DPALs. The operation of supersonic lasers is compared with that measured and modeled in subsonic lasers. The maximum power of supersonic Cs and K lasers is found to be higher than that of subsonic lasers with the same resonator and alkali density at the laser inlet by 25% and 70%, respectively. These results indicate that for scaling-up the power of DPALs, supersonic expansion should be considered.

  2. Assessment of concrete bridge decks with alkali silica reactions

    DEFF Research Database (Denmark)

    Eriksen, Kirsten; Jansson, Jacob

    2008-01-01

    Based on investigations of concrete from an approximately 40 years old bridge a procedure to support the management of maintenance and repair of alkali silica damaged bridges is proposed. Combined petrography and accelerated expansion testing were undertaken on cores from the Bridge at Skovdiget, Bagsværd, Denmark to provide information on the damage condition as well as the residual reactivity of the concrete. The Danish Road Directory’s guidelines for inspection and assessment of alkali silica damaged bridges will be briefly presented, and proposed modifications will be describe

  3. Ocular alkali burn associated with automobile air-bag activation.

    OpenAIRE

    White, J. E.; McClafferty, K; Orton, R B; Tokarewicz, A C; Nowak, E S

    1995-01-01

    Alkali burns of the eye can result in permanent visual impairment and are therefore potentially devastating. Immedicate diagnosis and treatment are essential to a good prognosis. The authors report the case of a 52-year-old woman who suffered alkali keratitis as the result of the activation of an automobile air bag. This type of injury will be seen more frequently as more cars are equipped with air bags and should be suspected in drivers and passengers involved in accidents in which air bags ...

  4. A hidden history of heartburn: The milk-alkali syndrome

    Directory of Open Access Journals (Sweden)

    Swaminathan Krishnan

    2011-01-01

    Full Text Available Milk-alkali syndrome was once considered to be of historic interest and a rare cause of hypercalcemia. Currently, it should be an important consideration in the differential diagnosis of hypercalcemia, after malignancies and primary hyperparathyroidism. The resurgence is in part due to the easy availability of over the counter (OTC calcium preparations. We describe a 50-year-old man who presented with severe hypercalcemia on two occasions associated with renal failure and metabolic alkalosis. Extensive investigations during the first admission failed to unravel a specific cause of hypercalcemia but a thorough history during his subsequent admission helped to confirm the diagnosis of milk-alkali syndrome.

  5. Interaction of alkali-metal overlayers with oxygen

    International Nuclear Information System (INIS)

    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 O2 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

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

    Science.gov (United States)

    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.

  7. Heat transfer characteristics of alkali metals flowing across tube banks

    International Nuclear Information System (INIS)

    For the purpose of getting heat transfer coefficients of alkali metals flowing across tube banks at an acceptable level, we propose to use an inviscid-irrotational flow model, which is based on our flow visualization experiment. We show that the heat transfer coefficients obtained for the condition where only the test rod is heated in tube banks considerably differ from those obtained for the condition where all the rods are heated, because of interference between thick thermal boundary layers of alkali metals. We also confirm that the analytical values obtained by this flow model are in a reasonable agreement with experimental values. (author)

  8. Chemical reactions of ultracold alkali-metal dimers in the lowest-energy $^3\\Sigma$ state

    OpenAIRE

    Tomza, Micha?; Madison, Kirk W.; Moszynski, Robert; Krems, Roman V.

    2013-01-01

    We show that the interaction of polar alkali dimers in the quintet spin state leads to the formation of a deeply bound reaction complex. The reaction complex can decompose adiabatically into homonuclear alkali dimers (for all molecules except KRb) and into alkali trimers (for all molecules). We show that there are no barriers for these chemical reactions. This means that all alkali dimers in the $a^3\\Sigma^+$ state are chemically unstable at ultracold temperature, and the us...

  9. Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arima, Kenta; Jiang, Peng; Deng, Xingyi; Bluhm, Henrik; Salmeron, Miquel

    2010-03-31

    The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.

  10. Off-center impurities in alkali halides: reorientation, electric polarization and binding to F center. V. Temperature-dependent electrostatic polarizabilities

    OpenAIRE

    Georgiev, Mladen

    2008-01-01

    We derive and discuss expressions for the temperature-dependent electrostatic polarizabilities of off-center ions holding good under various experimental conditions. At low temperatures and electric-field strengths, all of them reasonably reduce to values characteristic of phonon-coupled two-level systems. Prospects for further studies of the dispersive coupling are also considered.

  11. Off-center impurity in alkali halides: reorientation, electric polarization and pairing to F center. II. In-plane rotation and polarizability

    OpenAIRE

    Baldacchini, G.; Montereali, R. M.; Grassano, U. M.; Scacco, A.; Petrova, P.; Mladenova, M.; Ivanovich, M.; Georgiev, M.

    2007-01-01

    Because of its inherent 2-D character, the eigenvalue equation for the hindered rotation around a normal cation site of an off-center impurity nearest-neighboring an F center is the well-known Mathieu equation. We present an overview of literature data on Mathieu's periodic functions providing exact solutions to the Li+ reorientational problem. We compare them with bottom-well approximating solutions by harmonic-oscillator functions at an effective vibrational frequency reno...

  12. A Study on Alkali Consumption Regularity in Minerals of Reservoirs During Alkali(NaoH/Surfactant/Polymer Flooding in Daqing Oilfield

    Directory of Open Access Journals (Sweden)

    Zhenhai JIANG

    2012-04-01

    Full Text Available

    In the process of oil displacement of ASP (Alkali/ Surfactant/Polymer flooding , when Alkali interacts with the fluid and minerals of the reservoir, the alkali is subject to be consumed. The consumption regularity is the key factor affecting ASP ingredient, injection plan, scaling regularity for production wells and oil displacement effectiveness. Therefore to study the alkali consumption is of great significance in guiding ASP ingredient, injection project design, and the analysis for oil displacement mechanism. In this paper, aiming at the main components of minerals in the reservoir in Daqing Oilfield, the laboratory study on static alkali consumption for five kinds of minerals (kaolinite, grundite, chlorite, feldspar and quartz in ASP system and single component NaOH solution are done respectively. The alkali consumption regularities for five kinds of minerals in ASP and single component NaOH solution are concluded. The research indicates that the amount of alkali consumption for kaolinite, grundite, chlorite, feldspar and quartz is changing from larger to less accordingly, but is mainly caused by clay minerals; the average alkali consumption is 18.3% higher than that by matrix minerals. In single component NaOH solution, the alkali consumption styles of clay minerals and the matrix minerals take the chemical reaction as the lead, and the physical adsorption as the second. In ASP system solution, the alkali consumption style of clay minerals, takes the physical adsorption as the lead, and of matrix minerals takes the chemical reaction as the lead. In ASP solution, compared with single component solution, polymer and surfactant have the functions of restraint to alkali consumption in minerals of the reservoir, and the amount of alkali consumption decreases evidently.

    Key words: Alkali; Surfactan; Polymer; ASPl; Oil displacement

  13. Ternary alkali-metal and transition metal or metalloid acetylides as alkali-metal intercalation electrodes for batteries

    Energy Technology Data Exchange (ETDEWEB)

    Nemeth, Karoly; Srajer, George; Harkay, Katherine C; Terdik, Joseph Z

    2015-02-10

    Novel intercalation electrode materials including ternary acetylides of chemical formula: A.sub.nMC.sub.2 where A is alkali or alkaline-earth element; M is transition metal or metalloid element; C.sub.2 is reference to the acetylide ion; n is an integer that is 0, 1, 2, 3 or 4 when A is alkali element and 0, 1, or 2 when A is alkaline-earth element. The alkali elements are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). The alkaline-earth elements are Berilium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). M is a transition metal that is any element in groups 3 through 12 inclusive on the Periodic Table of Elements (elements 21 (Sc) to element 30 (Zn)). In another exemplary embodiment, M is a metalloid element.

  14. Electric fields induced in alkali-containing glasses by electron irradiation

    International Nuclear Information System (INIS)

    The formation of electric fields in alkali-containing glasses during electron irradiation is described by a numerical integration of Poisson's equation. The mobilities of both primary electrons and alkali ions as well as the excitation, mobility and emission of secondary electrons are considered. It is shown that during field-assisted migration of both alkali ions and electrons no transport correlation exists. (author)

  15. THE ROLE OF RPOS IN ALKALI TOLERANCE OF ENTEROHEMORRHAGIC E. COLI

    Science.gov (United States)

    The alkali tolerance of foodborne pathogens contributes to the survival of cells when encountering the alternating acidic and alkali conditions of gastrointestinal environments. The rpoS gene may play a role in the alkali tolerance of enterohemorrhagic Escherichia coli (EHEC). The objective was to d...

  16. Crystallization kinetics of organic-inorganic trihalide perovskites and the role of the lead anion in crystal growth.

    Science.gov (United States)

    Moore, David T; Sai, Hiroaki; Tan, Kwan W; Smilgies, Detlef-M; Zhang, Wei; Snaith, Henry J; Wiesner, Ulrich; Estroff, Lara A

    2015-02-18

    Methylammonium lead halide perovskite solar cells continue to excite the research community due to their rapidly increasing performance which, in large part, is due to improvements in film morphology. The next step in this progression is control of the crystal morphology which requires a better fundamental understanding of the crystal growth. In this study we use in situ X-ray scattering data to study isothermal transformations of perovskite films derived from chloride, iodide, nitrate, and acetate lead salts. Using established models we determine the activation energy for crystallization and find that it changes as a function of the lead salt. Further analysis enabled determination of the precursor composition and showed that the primary step in perovskite formation is removal of excess organic salt from the precursor. This understanding suggests that careful choice of the lead salt will aid in controlling crystal growth, leading to superior films and better performing solar cells. PMID:25625616

  17. Electrical and optical properties of the TTF-halides

    Energy Technology Data Exchange (ETDEWEB)

    Warmack, R.J.; Callcott, T.A.

    1976-06-01

    Recent interest in the highly conductive charge transfer organic crystals, particularly tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ), prompted this investigation of TTF-TCNQ and other systems. Results of conductivity measurements on TTF-TCNQ confirm results obtained by other authors. TTF was found to combine with the halogens to form crystals with interesting electrical properties due to the segregated stacking of the TTF molecules. The monoclinic forms of TTF-I/sub n/ and TTF-Br/sub n/ (n approximately 0.7) have a high conductivity (100-550 (..cap omega..-cm)/sup -1/) which is almost temperature independent for a very broad region near room temperature but displays a thermally activated conductivity at low temperature. Unlike monoclinic TTF-Br/sub n/, monoclinic TTF-I/sub n/ displays a strong hysteresis in its conductivity upon temperature cycling. The conductivity of the orthorhombic form of TTF-I/sub n/ (n = 2) is about five orders of magnitude lower than the monoclinic form at room temperature and is thermally activated over the entire temperature range. Polarized single crystal optical reflectance measurements in the spectral region from 0.6 eV to 5 eV on the two crystalline forms of TTF-I/sub n/ were made. The reflection of light polarized along the conducting axis of the monoclinic crystals was typical of Drude-like free electron gas with the edge occurring at about 1.15 eV. Optical properties were determined by a Lorentzian oscillator fitting procedure. Results indicated that the majority of the visible spectrum can be attritubed to TTF/sup +/ transitions.

  18. Crystal Meth

    Science.gov (United States)

    ... Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, 2013 ... my drug addiction having to deal with Crystal meth. I am now in recovery and fighting my ...

  19. Crystal Creations.

    Science.gov (United States)

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  20. Effect of Three-Body Interactions on Electronic Polarizabilities and Photoelastic Behaviour of Partially Covalent Crystals

    International Nuclear Information System (INIS)

    The effect of three-body interactions on the photoelastic behaviour and the electronic polarization of silver, thallium and copper halides, which are partially covalent in character and posses three different crystal structures are investigated. The cation, anion and molecular polarizabilities calculated in their crystalline state seem to be reliable as they follow a systematic trend. The calculated values of the strain derivatives of the electronic dielectric constants are much closer to their experimental data than those obtained by earlier workers