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Sample records for alkali halide crystal

  1. Energy determination from electron range in alkali-halide crystals

    International Nuclear Information System (INIS)

    The coloration of alkali-halide crystals was used to determine the electron energies <10 MeV. The coloration depth in a crystal - the visual range, was measured by using a lighted transparent ruler and an empirical relation was used to determine the extrapolated range. The sharpest edge of coloration was obtained in KBr crystals. The electron energy was calculated from a semi-empirical relation between the extrapolated range of electrons and their energy

  2. Dislocation unpinning model of acoustic emission from alkali halide crystals

    Indian Academy of Sciences (India)

    B P Chandra; Anubha S Gour; Vivek K Chandra; Yuvraj Patil

    2004-06-01

    The present paper reports the dislocation unpinning model of acoustic emission (AE) from alkali halide crystals. Equations are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number of AE pulse emitted. It is found that the AE pulse rate should be maximum for a particular strain of the crystals. The peak value of the AE pulse rate should depend on the volume and strain rate of the crystals, and also on the pinning time of dislocations. Since the pinning time of dislocations decreases with increasing strain rate, the AE pulse rate should be weakly dependent on the strain rate of the crystals. The total number of AE should increase linearly with deformation and then it should attain a saturation value for the large deformation. By measuring the strain dependence of the AE pulse rate at a fixed strain rate, the time constant $\\tau_{\\text{s}}$ for surface annihilation of dislocations and the pinning time $\\tau_{\\text{p}}$ of the dislocations can be determined. A good agreement is found between the theoretical and experimental results related to the AE from alkali halide crystals.

  3. Deformation Bleaching of Coloration in Alkali Halide Crystals

    Science.gov (United States)

    Chandra, B. P.; Vishwakarma, H. L.; Khare, P. K.

    1997-12-01

    The present paper reports the phenomenological theory of deformation bleaching of coloration in alkali halide crystals. Expressions are derived for the dislocation capture probability of F-centre electrons in alkali halide crystals, and for the rate of generation of electrons in the dislocation band. On the basis of the rate of generation of dislocation electrons and their subsequent recombination with hole centres, deep traps and other compatible traps (including deformation generated traps), an expression is derived for the deformation bleaching, which indicates the exponential decrease of the density of F-centres with deformation of the crystal. A good agreement is found between the theoretical and experimental results. The value of the effective radius re of the interaction of dislocations with F-centres, is estimated and it is found to be 1.95b, 2.00b, 1.33b and 1.70b for KCl, KBr, NaCl and NaBr crystals, respectively (where b is the Burgers vector)

  4. 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.

  5. Irradiation-induced defects in alkali halide crystals

    International Nuclear Information System (INIS)

    Models are presented for the successive stages of aggregation and recombination of radiation-induced defects in alkali halides. The construction of the present models is assisted by the calculation of defect energies. Three main areas are discussed: firstly, initial aggregation of H centres is considered, where the formation of a weakly bound di-H centre which collapses into a neutral halogen molecule occupying an interstitial site is proposed. Secondly, the thermodynamics of formation of the interstitial loops detected in the electron microscope by Hobbs et al (Proc. R. Soc; A332; 167 (1973)) are considered. The previously proposed mechanism by which the loops are created is confirmed; this involves the displacement of lattice ions to dislocation loops by halogen molecules which occupy the vacancy pairs created. Thirdly, the mechanism of annealing of metal colloids is considered, and it is suggested that the vacancy-molecule complexes, which are created together with the dislocation loops, may play an important role. (author)

  6. 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)

  7. 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)

  8. Luminescence of mono halide excitons and intraband luminescence in alkali-halide crystals

    International Nuclear Information System (INIS)

    Nanosecond electron beam pulses excite in RbCl, RbBr and KBr crystals the continuum of temperature of two-halide auto localized excitons, as well as weak rapid luminescence interference as luminescence of metastable monohalide auto localized excitons luminescence was performed for KBr crystal, excited by 6.6-7.7 and 14-20 eV photons

  9. Acoustic and photon emissions during mechanical deformation of coloured alkali halide crystals

    International Nuclear Information System (INIS)

    Acoustic and photon emissions take place in the elastic and plastic as well as the fracture region of x-irradiated KBr, KCl and NaCl crystals. The rate of photon emission is linear with the strain rate: however, the RMS value of the acoustic emission is proportional to the square root of the strain rate. The acoustic emission is maximum for x-irradiated NaCl crystals; however, the photon emission is maximum for x-irradiated KBr crystals. From the similarity between the acoustic emission and the photon emission, it seems that mobile dislocations are responsible for the acoustic emission in coloured alkali halide crystals. (author)

  10. Helium irradiation of alkali halides

    International Nuclear Information System (INIS)

    An investigation has been made of radiation damage in alkali halide crystals induced by heavy bombardment of 1 MeV helium ions. The channeling technique has been employed and three processes have been monitored simultaneously to explain the apparent reduction of damage at high doses. It is shown that the initial rise and fall of the back-scattered yield from different alkali halides can be related to the Pooley mechanism coupled with the aggregation of interstitials to form dislocation loops through the intermediate stage of clusters

  11. The process of colloidal centre formation in alkali halide crystals during irradiation

    International Nuclear Information System (INIS)

    In this paper are analysed the processes of electronic centre aggregation to colloidal alkali metal particles in alkali halide crystals under radiation. It is shown that the existing theories of particle coalescence do not describe the experimentally observed kinetics of radiolysis. A new model of radiation colloid formation in these systems is proposed in which the interaction between colloidal centres is taken into account. In the present model the experimentally observed dose and temperature dependences, as well as the size distribution of the electron products of radiolysis, are explained. (author)

  12. Ga+, In+ and Tl+ Impurities in Alkali Halide Crystals Distortion Trends

    CERN Document Server

    Aguado, A

    2000-01-01

    A computational study of the doping of alkali halide crystals (AX: A = Na, K; X = Cl, Br) by ns2 cations (Ga+, In+ and Tl+) is presented. Active clusters of increasing size (from 33 to 177 ions) are considered in order to deal with the large scale distortions induced by the substitutional impurities. Those clusters are embedded in accurate quantum environments representing the surrounding crystalline lattice. The convergence of the distortion results with the size of the active cluster is analyced for some selected impurity systems. The most important conclusion from this study is that distortions along the (100) and (110) crystallographic directions are not independent. Once a reliable cluster model is found, distortion trends as a function of impurity, alkali cation and halide anion are identified and discussed. These trends may be useful when analycing other cation impurities in similar host lattices.

  13. Correlation between deformation bleaching and mechanoluminescence in coloured alkali halide crystals

    Indian Academy of Sciences (India)

    B P Chandra; M Ramrakhiani; P Sahu; A M Rastogi

    2000-02-01

    The present paper reports the correlation between deformation bleaching of coloration and mechanoluminescence (ML) in coloured alkali halide crystals. When the $F$-centre electrons captured by moving dislocations are picked up by holes, deep traps and other compatible traps, then deformation bleaching occurs. At the same time, radiative recombination of dislocation captured electrons with the holes gives rise to the mechanoluminescence. Expressions are derived for the strain dependence of the density of colour centres in deformed crystals and also for the number of colour centres bleached. So far as strain, temperature, density of colour centres, $E_{a}$ and volume dependence are concerned, there exists a correlation between the deformation bleaching and ML in coloured alkali halide crystals. From the strain dependence of the density of colour centres in deformed crystals, the value of coef?cient of deformation bleaching is determined and it is found to be 1.93 and 2.00 for KCl and KBr crystals, respectively. The value of $(D + \\mathcal{X})$ is determined from the strain dependence of the ML intensity and it is found to be 2.6 and 3.7 for KCl and KBr crystals, respectively. This gives the value of coef?cient of deformation generated compatible traps $\\mathcal{X}$ to be 0.67 and 1.7 for KCl and KBr crystals, respectively.

  14. Defects in alkali halide crystals irradiated under applied stress

    International Nuclear Information System (INIS)

    Futher study of physical property alterations of dielectric crystals placed in different fields and subjected to irradiation is carried out. Mechanical, optical and thermal properties of NaCl, LiF, KCl crystals irradiated with p and n-p radiation in electric thermal and mechanical fields are presented. Crystal structural defects responsible for the property alteration are studied (point defects, their aggregates, dislocations, and their interactions). The irradiation of crystals in the stressed state allows one to change the defect spectrum which means the possibility to obtain materials with controllable properties

  15. High-intensity ?-ray scattering from alkali halide crystals

    International Nuclear Information System (INIS)

    We have measured the fractional change F of the resonant photon fraction due to Bragg scattered from the (200), (400), and (600) planes of NaCl and NaF, as well as the (200) and (400) planes of LiF. Unlike previous measurements of this type, we have used well-collimated beams made possible by a high-intensity ?-ray source (?100 Ci). The values of F reflect loss in elastic intensity and are of importance since the crystals studied here are widely used as monochromating filters. We find a remarkably large fraction of the scattered radiation remains recoilless (>94%), even for the (600) reflection of NaCl, and a value of F=100.0(3%) for the (200) plane of LiF shows that this crystal is an excellent ?-ray monochromator and calibration for experiments with small F values. The F values can be expressed in terms of elastic and inelastic components, and as such provide information about the Debye-Waller factors of crystals

  16. A study of ion-photon emission in alkali-halide crystals

    International Nuclear Information System (INIS)

    Optical emission under bombardment of the NaCl, NaI, CsCl, and CsI crystals by Ar+ ions with an energy of 25 keV was studied, and the emission quantum yield of the sputtered alkaline-metal atoms is found to be higher for chlorides than for iodides. At the same time, the crystal luminescence reveals an inverse dependence. The assumption is made that population of the excited states of sputtered atoms is caused by electrons localized at the defect levels in the forbidden band. Studies of the energy distribution of the sputtered excited particles revealed the existence of a group of slow atoms emitting upon transitions from the highly-excited states. This fact testifies to the absence of substantial metallization of the surface under ionic bombardment of alkali-halide crystals. 20 refs., 3 figs., 1 tab

  17. 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.

  18. Efficiency of primary radiation-induced defects in alkali halide crystals

    International Nuclear Information System (INIS)

    Temperature dependences of F centers formation efficiency (FE) are measured by the method of pulse absorption spectrometry with nanosecond resolution with the aim of determination of the relative yield of decay reaction of electron excitations into primary pairs of structural defects in alkali halide crystals (LiF, NaF, NaCl, NaBr, KCl, KBr, KI, RbBr). It is shown that for all studied compounds FE of F centers increases in the temperature range from 100 up to 300 K. Activation energies of the primary defects storage process are determined. It is supposed that FE of primary defects is determined mainly by the ratio of exciton energy parameters of predissociated and predefect state as well as of energy, stored on defect

  19. Electron-beam production of colour centres on alkali halide crystals and films

    International Nuclear Information System (INIS)

    In this article we analyze the production of localized colour centres on the surface of alkali halide crystals and films produced by electron beam radiations in the 10-30 keV range. It was found that the colour centre production is restricted to electron penetration (3-10 ?m depending on the material and electron energy) with a very intense local optical density (above 104 cm-1). As the refractive index variation calculated using the Kramers-Kroenig relations from the observed absorption bands should be enough for light confinement (10-3-10-2), electron beam generated colour centres should allow the production of light wave guides for several applications. Optical absorption bands can be created in ionic crystals anywhere from the ultraviolet to the infrared, preserving transparent regions of the spectrum. With an appropriate computer aided design (CAD) program and a microcomputer interface to the adapted micropositioning mechanical devices and shutter, it was possible to control an electron microprobe sample holder in order to draw precise patterns and have various controlled exposure times. (orig.)

  20. 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.

  1. Mobile interstitial model and mobile electron model of mechano-induced luminescence in coloured alkali halide crystals

    International Nuclear Information System (INIS)

    A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08, 0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related to the process of stress relaxation in crystals. (author). 33 refs., 5 figs., 1 tab

  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. Electron scattering from alkali halide molecules

    International Nuclear Information System (INIS)

    The low energy electron scattering from molecules belonging to alkali halide matrix is studied. The modified Born-Eikonal Series method is employed to calculate rotational excitation cross sections. The curves are plotted for the incident electron energy versus total cross section for each column of alkali halide matrix. The conclusion is drawn regarding dependence of the total cross section with the electron-negativity difference of the molecules. (author)

  4. Temperature dependence of pulse-induced mechanoluminescence excitation in coloured alkali halide crystals

    Indian Academy of Sciences (India)

    Namita Rajput; S Tiwari; B P Chandra

    2004-12-01

    In practice, the relative efficiencies of different crystals are often determined under identical conditions of temperature and excitation. If the temperature of a crystal is increased or decreased with respect to room temperature, luminescence efficiency may get increased or decreased according to the composition of the crystal. When coloured crystals of NaCl, NaBr, KCl and KBr are excited by pulse-induced excitation at different temperatures, the mechanoluminescence (ML) intensity increases with temperature. The ML intensity of first peak, ml, second peak, _m2 and the total ML intensity, T, initially increase with temperature and then tend to attain an optimum value for a particular temperature of crystals. The ratio, m2/ml, is found to increase with increasing temperature of the crystals. The expression derived on the basis of rate equations, are able to explain the temperature dependence of ML intensity on several parameters.

  5. Temperature dependent dynamic ESD processes in alkali halides

    International Nuclear Information System (INIS)

    The effect of the sample temperature on angular-resolved kinetic-energy distributions of alkali and halogen atoms, electronically desorbed from single crystal alkali halides, has been measured. It was found that while the emission of particles with thermal energies increased by about a factor of 40 in the temperature range 90-300degC, the nonthermal halogen atom intensity decreased by about a factor of 3. From these temperature dependent measurements the activation energies for thermally assisted defect migration processes have been estimated. The results will be compared with the data available in the literature and the predictions of a recently proposed model for electron-stimulated desorption (ESD) of alkali halides. (orig.)

  6. The kinetics of diffusion-controlled annealing of Frenkel defects in alkali halide crystals

    International Nuclear Information System (INIS)

    The annealing kinetics of the strongly correlated (the so-called geminate) pairs of both neutral F,H centers as well as F, I centers entering secondary triplets (F..I..self-trapped hole) in KCl and KBr crystals is calculated. In this model diffusion of hole I and H centers and their annihilation with electron F centers at short relative distances stimulated by the elastic or Coulomb interaction are taken into account. It is demonstrated that F,H pairs are destroyed by tunneling recombination already at times ?10-4 s, i.e. much before the beginning of the thermostimulated experiments. A possible explanation of this contradiction is discussed. ((orig.))

  7. EPR and optical studies of Ge+ ions in alkali halide crystals

    International Nuclear Information System (INIS)

    By the method of EPR it is ascertained for the first time that X-ray irradiation of NaCl:Ce2+ and KCl:Ge2+ at 77 K results in the capture of an electron by Ge2+ ion and the formation of Ge+ ion. Two types of Ge+ centres are revealed Ge+ - centres with orthorhombic symmetry directly after irradiation; the nearest surrounding of these centres has a cation vacancy v sub(k) (Gesup(+)v sub(k) centres). When heating crystals up to 300 K, Gesup(+)v sub(k) - centres are transformed into Ge+ centres wth tetragonal symmetry (Gesup(+)v sub(k) centres) due to the drift of the cathion vacancy from Ge+ ion. Spin hamiltonan parameters are determined for Gesup(+)v sub(k) and Gesub(k)sup(+) centres. It is ascertained that cathion vacancy are primarily located in the nearest by (110) directions position from germanium ion. Absorption optical bands correspond to Gesub(k)sup(+) and Gesup(+)v sub(k) centres in 190-220 nm reg

  8. Na+ and Rb+ tracer diffusion in alkali halides

    International Nuclear Information System (INIS)

    We have undertaken a fundamental study of heterodiffusion of foreign ions in pure single crystals. The present work describes measurements of the diffusion coefficient of monovalent cations in some alkali halides, namely Na+ and Rb+ into KCl, KBr, NaI and KI. Priority is given to the super-accuracy of the experimental data. The target is to test the validity of the existing theories for calculating the enthalpy and entropy of migration. (author)

  9. 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.)

  10. Theory of the late stage of radiolysis of alkali halides

    International Nuclear Information System (INIS)

    Recent results on heavily irradiated natural and synthetic NaCl crystals give evidence for the formation of large vacancy voids, which were not addressed by the conventional Jain-Lidiard model of radiation damage in alkali halides. This model was constructed to describe metal colloids and dislocation loops formed in alkali halides during earlier stages of irradiation. We present a theory based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of excess H centers. Voids are shown to arise due to the reaction between F and VF centers at the surface of halogen bubbles. Critical parameters associated with the bubble-to-void transition are evaluated. Voids can grow to sizes exceeding the mean distance between colloids and bubbles, eventually absorbing them, and, hence, igniting a back reaction between the halogen gas and metal. The amount of radiation damage in alkali halides should be evaluated with account of void formation, which strongly affects the radiation stability of material

  11. Ground state properties of heavy alkali halides

    OpenAIRE

    Doll, Klaus; Stoll, Hermann

    1998-01-01

    We extend previous work on alkali halides by calculations for the heavy-atom species RbF, RbCl, LiBr, NaBr, KBr, RbBr, LiI, NaI, KI, and RbI. Relativistic effects are included by means of energy-consistent pseudopotentials, correlations are treated at the coupled-cluster level. A striking deficiency of the Hartree-Fock approach are lattice constants deviating by up to 7.5 % from experimental values which is reduced to a maximum error of 2.4 % by taking into account electron ...

  12. 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

    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

  13. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    Energy Technology Data Exchange (ETDEWEB)

    Bory, Benjamin F.; Wang, Jingxin; Janssen, René A. J.; Meskers, Stefan C. J., E-mail: s.c.j.meskers@tue.nl [Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Gomes, Henrique L. [Instituto de Telecomunicações, Av. Rovisco, Pais 1, 1049-001 Lisboa, Portugal and Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); De Leeuw, Dago M. [Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany and King Abdulaziz University, Jeddah (Saudi Arabia)

    2014-12-08

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron–hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 10{sup 25}/m{sup 3}. The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics.

  14. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    International Nuclear Information System (INIS)

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron–hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 1025/m3. The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics

  15. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    Science.gov (United States)

    Bory, Benjamin F.; Wang, Jingxin; Gomes, Henrique L.; Janssen, René A. J.; De Leeuw, Dago M.; Meskers, Stefan C. J.

    2014-12-01

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron-hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 1025/m3. The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics.

  16. Quantum-chemical investigations of the electronic structure, mechanism of radiation defect production and recombination in alkali halide crystals

    International Nuclear Information System (INIS)

    The results of recent investigations of electronic and spatial structure as well as mechanism of radiation-induced production and tunneling recombination of defects in ionic crystals LiF and KCl are briefly summerized. The calculations have been performed in the framework of the semiempirical quantum- chemical method, which is the simplified version of the unrestricted Hartree-Fock-Rothaan method, and of a molecular cluster model

  17. Measurement of Surface Phonon Dispersion Curves of Alkali Halide Single Crystals by Time of Flight Spectroscopy of He Atom Beams

    Science.gov (United States)

    Toennies, J. Peter

    1982-01-01

    The development of highly expanded He nozzle beams with velocity half widths less than 1% has made it possible to observe the annihilation and creation of single surface phonons in time of flight spectra of the scattered atoms. Measurements have been carried out for a wide range of incident angles at a beam energy of about 20 meV for the following crystals and directions: LiF langle100rangle, LiF langle110rangle, NaF langle100rangle, KCl langle100rangle, NaCl langle100rangle, and MgO langle100rangle. In all cases the spectra show up to 5 sharp well resolved maxima. From the final angle and energy of each peak the parallel surface momentum component and frequency of the phonon is determined. The results show a predominant coupling with Rayleigh surface phonons with only a weak coupling with bulk phonons. Rayleigh dispersion curves have been measured out to the zone boundary for all crystals except LiF langle110rangle and MgO. There is also some evidence for excitation of modes of higher frequencies. Except for LiF langle100rangle at the zone boundary the results compare well with theoretical calculations. Benedek has been able to fit the new LiF He atom and previous neutron dispersion curves with a revised breathing shell model calculation.

  18. Time-resolved spectroscopic study on the type I self-trapped excitons in alkali halide crystals. 2. Excitation spectra and relaxation processes

    International Nuclear Information System (INIS)

    Excitation spectra for the fluorescent and phosphorescent components of type I bands in seven alkali halides, NaCl, NaBr, KBr, RbBr, NaI, KI and RbI, are measured in both energy ranges of the free exciton absorption and the band-to-band transition. Using SR pulses as the excitation light source, the two components are resolved by the method of simultaneous photon-counting through two independent time-windows. Excitation spectra for the phosphorescent bands of type II or III are also measured for comparison. From these spectra, total luminescence yield and the fraction of the type I band are determined as a function of excitation energy. On the basis of these results, the relaxation processes of free electron-hole pairs and free excitons, especially on the difference between them, are discussed. (author)

  19. Energy transfer in alkali halide scintillators by electron-hole diffusion and capture

    International Nuclear Information System (INIS)

    Recent calculations and experiments dealing with charge transport and capture in activated alkali halide scintillators are reviewed. Both electrons and holes are captured at thallium sites in crystals such as KI(Tl) and NaI(Tl). The kinetics of charge transport is governed either by the diffusive motion of the self-trapped hole, or by the release of electrons from a thallium site. (U.S.)

  20. Alkali halide microstructured optical fiber for X-ray detection

    International Nuclear Information System (INIS)

    Microstructured optical fibers containing alkali halide scintillation materials of CsI(Na), CsI(Tl), and NaI(Tl) are presented. The scintillation materials are grown inside the microstructured fibers using a modified Bridgman-Stockbarger technique. The x-ray photon counts of these fibers, with and without an aluminum film coating are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The photon count results show significant variations in the fiber output based on the materials. The alkali halide fiber output can exceed that of the CdTe detector, dependent upon photon counter efficiency and fiber configuration. The results and associated materials difference are discussed

  1. Alkali halide microstructured optical fiber for X-ray detection

    Energy Technology Data Exchange (ETDEWEB)

    DeHaven, S. L., E-mail: stanton.l.dehaven@nasa.gov, E-mail: russel.a.wincheski@nasa.gov; Wincheski, R. A., E-mail: stanton.l.dehaven@nasa.gov, E-mail: russel.a.wincheski@nasa.gov [NASA Langley Research Center, Hampton, VA 23681 (United States); Albin, S., E-mail: salbin@nsu.edu [Norfolk State University, Norfolk, VA 23504 (United States)

    2015-03-31

    Microstructured optical fibers containing alkali halide scintillation materials of CsI(Na), CsI(Tl), and NaI(Tl) are presented. The scintillation materials are grown inside the microstructured fibers using a modified Bridgman-Stockbarger technique. The x-ray photon counts of these fibers, with and without an aluminum film coating are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The photon count results show significant variations in the fiber output based on the materials. The alkali halide fiber output can exceed that of the CdTe detector, dependent upon photon counter efficiency and fiber configuration. The results and associated materials difference are discussed.

  2. PLENARY SESSIONThermoluminescence and lattice defects in alkali halides

    OpenAIRE

    Alvarez Rivas, J.

    1980-01-01

    Recent developments in the study of the thermoluminescence of irradiated alkali halides indicate that many of the observed glow peaks are due to thermoluminescent processes related to the recombination of radiation induced lattice defects. There is a large amount of experimental results which supports that the F+H recombination is a rather common thermoluminescent process. Under some conditions it has been observed that the I + F, I + VK and H + ? recombinations can indirectly induce light em...

  3. Thermal conductivity of molten alkali halides and their mixtures

    International Nuclear Information System (INIS)

    Thermal conductivity of molten alkali halides and their mixtures with common anions is measured as a function of temperature. Use is made of the most reliable method of coaxial cylinders made of platinum, with radiation heat transfer being taken into account. It is found to vary directly with temperature. Expressions for its temperature dependence are derived from the experimental observations. Linear relations of the thermal conductivity to the molar volume are established for molten alkali fluorides, chlorides, bromides, iodides and their mixtures with common anions. Deviations from the additive quantities towards smaller values are observed in the case of the mixtures. They are in a good accordance with inverse deviations of their adiabatic compressibility. The heat conduction of ionic melts is semiquantitatively examined. Elementary quantities of heat transferred from cations to anions and vice versa are estimated. (author)

  4. Games people play with interstitials (in alkali halides)

    International Nuclear Information System (INIS)

    A survey is given of the various ways in which interstitial halogen atoms produced by ionising radiation can be trapped in alkali halides. First, the fundamental interstitial halogen atom center, the H-center, is discussed. Then, interstitial centers trapped by, or in the neighbourhood of, various impurities are presented. Particular attention is given to trapping by the following impurities: foreign halogen ions, foreign alkali ions or pairs of both. The discussion is limited to a description of the production and the models of these H-type centers and little is said about their sometimes interesting physical properties. A few speculations are offered why certain interstitial centers have not yet been observed. The models of a few paramagnetic diinterstitial centers are also presented

  5. Photoelectron spectroscopy of alkali halide clusters with excess electrons

    International Nuclear Information System (INIS)

    We have studied excess electrons in alkali halide clusters, using a combination of a laser vaporization source, time-of-flight mass spectrometer, and magnetic bottle photoelectron electron spectrometer. We have obtained photoelectron spectra of (NaCl)n-, (NaCl)nNa-, (NaCl)nNam- and (KI)3Km- cluster anions contain either a single excess electron, two excess electrons, or several excess electrons. In the spectra of (NaCl)n, our measured electron vertical binding energies are in excellent agreement with the calculated values. We found single excess electrons in the (NaCl)n- cluster anions are mostly localized, either occupying an anion vacancy as an F-center in solids, or neutralizing a Na+ ion. In a few case, electrons are delocalized on the surface of clusters. In the spectra of (NaCl)nNam-, we observed three distinct types of spectra, corresponding to three different electron accommodation modes. We suggest that in certain clusters, the excess electrons are spin paired, localizing in a single anion vacancy as an F'-center in solids or on a Na+ cation to form a Na-. In other clusters, the electrons separately occupy a pair of anion vacancies as a double F-center. In the spectra of (NaCl)3Nam- and (KI)3Km-, we found features of the spectra that resemble those seen in the spectra of pure alkali metal anions after m ? 2. We suggest that the metallic and ionic parts in these clusters are separated, analogous to the metal and nonmetal phase separation in alkali-alkali halide metals

  6. 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

  7. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Science.gov (United States)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  8. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    International Nuclear Information System (INIS)

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  9. Solution enthalpies of alkali metal halides in water and heavy water mixtures with dimethyl sulfoxide

    International Nuclear Information System (INIS)

    Solution enthalpies of CsF, LiCl, NaI, CsI and some other halides of alkali metals and tetrabutylammonium have been measured by the method of calorimetry. Standard solution enthalpies of all alkali metals (except rubidium) halides in water and heavy water mixtures with dimethylsulfoxide at 298.15 K have been calculated. Isotopic effects in solvation enthalpy of the electrolytes mentioned in aqueous solutions of dimethylsulfoxide have been discussed. 29 refs., 2 figs., 4 tabs

  10. Energy distributions of secondary ions sputtered from alkali-halide compound surfaces

    International Nuclear Information System (INIS)

    Energy distributions of secondary ions sputtered from the surfaces of six alkali-halide compounds have been measured. On the base of the experimentally obtained data the question on sputtered particles ionization mechanism is being discussed. A significant role of electron excitation processes during the cascade collisions is noticed, as well as the neutralization processes which have some specific peculiarities in the case of alkali-halide compounds.15 refs., 4 figs

  11. 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)

  12. 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

    2013-01-01

    Ro?. 5, ?. 6 (2013), s. 561-564. ISSN 2164-6627 R&D Projects: GA ?R GAP108/12/0891 Institutional support: RVO:68378271 Keywords : halide crystals * nucleation Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.aspbs.com/asem.html#v5n6

  13. Physics and nanofriction of alkali halide solid surfaces at the melting point

    Science.gov (United States)

    Zykova-Timan, T.; Ceresoli, D.; Tartaglino, U.; Tosatti, E.

    2006-09-01

    Alkali halide (1 0 0) surfaces are anomalously poorly wetted by their own melt at the triple point. We carried out simulations for NaCl(1 0 0) within a simple (BMHFT) model potential. Calculations of the solid-vapor, solid-liquid and liquid-vapor free energies showed that solid NaCl(1 0 0) 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(1 0 0). 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.

  14. 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.

  15. 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).

  16. Ab initio perspective on the Mollwo-Ivey relation for F centers in alkali halides

    Science.gov (United States)

    Tiwald, Paul; Karsai, Ferenc; Laskowski, Robert; Gräfe, Stefanie; Blaha, Peter; Burgdörfer, Joachim; Wirtz, Ludger

    2015-10-01

    We revisit the well-known Mollwo-Ivey relation that describes the "universal" dependence of the absorption energies of F-type color centers on the lattice constant a of alkali-halide crystals, Eabs?a-n. We perform both state-of-the-art ab initio quantum chemistry and post-DFT calculations of F-center absorption spectra. By "tuning" independently the lattice constant and the atomic species we show that the scaling with the lattice constant alone (keeping the elements fixed) would yield n =2 in agreement with the "particle-in-the-box" model. Keeping the lattice constant fixed and changing the atomic species enables us to quantify the ion-size effects which are shown to be responsible for the exponent n ?1.8 .

  17. 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).

  18. 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.

  19. Role of water in alkali halide heterogeneous chemistry relevant to the atmosphere: A surface science study

    Science.gov (United States)

    Ghosal, Sutapa

    2001-05-01

    Water is a ubiquitous atmospheric constituent. The interaction of water in its various forms (vapor, liquid, ice) with other atmospheric constituents has a significant impact on the chemistry of the atmosphere. Another class of compounds that are of considerable importance in atmospheric chemistry are alkali halide salts such as sea salt particles. Heterogeneous reactions of alkali halides with gas phase pollutants are believed to be an important source of halogens in the troposphere. There is an increasing amount of evidence that the presence of water plays an important role in the heterogeneous chemistry of alkali halide particles. It is the goal of this dissertation to contribute to the understanding of the interaction of water with alkali halide surfaces and its atmospheric implications. Surface processes are of fundamental importance in heterogeneous atmospheric chemistry, but they are often difficult to study because of their inherent complexity. As this dissertation shows, the use of modern surface science techniques offer valuable insights into these complex processes and as such offer complementary alternatives to the traditional atmospheric chemistry experiments. The surface science techniques used in this dissertation are X-ray photoelectron spectroscopy (XPS), scanning polarization force microscopy (SPFM) and scanning electron microscopy (SEM). Presented here are the results of the XPS and SEM studies undertaken to determine the nature and content of surface adsorbed water on NaCl as a function of surface defects. The details of HNO3 uptake on NaCl and the effect of surface adsorbed water on this uptake are also discussed. Our results show that the amount of ``strongly adsorbed water'' (SAW) on the surface of NaCl particles depends on the particle size and hence, on the concentration of surface defects. Unlike the (100) single crystal the more defective surfaces show dissociative water uptake at room temperature upon exposure to water vapor well below the deliquescence point of NaCl. The binding energy and temperature dependence characteristics of the SAW related oxygen signal on the NaCl particles are consistent with OH- like species. We also show that the dissociative adsorption of HNO3(g) on NaCl to form NaNO3(s) and HCl(g) follows single-site Langmuir adsorption behavior. The dissociative adsorption accompanied by water-induced recrystallization of the NaNO3 product on the NaCl surface gives rise to the experimentally observed HNO3 pressure dependence of the reactive sticking coefficient for reaction under steady-state reaction conditions. Surface segregation of bromine in bromide doped NaCl single crystals has been studied using XPS, SEM and SPFM. Our results show, for the first time, that substantial segregation of Br- to the surface of NaCl samples with low level Br- dopant concentrations occurs under conditions of water vapor exposure. The segregation phenomenon is likely to play an important role in atmospheric phenomena involving surface reactions of sea salt particles and aerosols.

  20. The electronic structure of the F-center in alkali-halides-The Bethe cluster - lattice

    International Nuclear Information System (INIS)

    The electronic structure of the F-center in alkali-halides with the NaCl structure has been studied using the Bethe Cluster lattice method. The central cluster has been taken as constituted by the vacancy and the nearest- and second-neighbors to it, respectively cations and anions. The optical transitions have been calculated and compared to experimental data on the location of the peak of the F-absorption band. The agreement obtained indicates that this method may be used to study properties of this defect in alkali halides. (Author)

  1. Electron density in the alkali halide crystals

    International Nuclear Information System (INIS)

    Structure factors at room temperature are computed for LiF, NaF, NaCl and KCl by means of theoretical ionic form factors and theoretical Debye-Waller factors. The values obtained are compared with the best available experimental data. For LiF, KCl and NaF - for which good experimental data are available - there is generally very good agreement, with only a few sizeable discrepancies for NaF that can be attributed to deficiencies of the experimental data. It is concluded that there is no apparent need to question the validity of the Debye-Waller theory as recently proposed in the literature. (orig.)

  2. Luminescent decay and spectra of impurity-activated alkali halides under high pressure

    International Nuclear Information System (INIS)

    The effect of high pressure on the luminescence of alkali halides doped with the transition-metal ions Cu+ and Ag+ and the heavy-metal ions In+ and Tl+ was investigated to 140 kbar. Measurement of spectra allowed the prediction of kinetic properties, and the predictions agree with lifetime data

  3. 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)

  4. Surface tension of molten alkali metal halides as a function of ion sizes

    International Nuclear Information System (INIS)

    The analysis of the experimental data on the surface tension of the liquid/vapor interphase boundary of the molten alkali metal halides MX (M Li-Cs, X = F-I) near the melting temperature, accounting for the cation and anion dimensional differences, is presented. The main attention is focused at the manifestation of the effects of the interphase boundary of the effects of the interphase boundary thickness and twofold electric layer. It is shown, that the experimental data on the whole MX series may be represented in the form of the electrocapillary curve on the graph of the surface tension dependence on the degree of the halides dimensional asymmetry

  5. Excess-electron and excess-hole states of charged alkali halide clusters

    Science.gov (United States)

    Honea, Eric C.; Homer, Margie L.; Whetten, R. L.

    1990-12-01

    Charged alkali halide clusters from a He-cooled laser vaporization source have been used to investigate two distinct cluster states corresponding to the excess-electron and excess-hole states of the crystal. The production method is UV-laser vaporization of an alkali metal rod into a halogen-containing He flow stream, resulting in variable cluster composition and cooling sufficient to stabilize weakly bound forms. Detection of charged clusters is accomplished without subsequent ionization by pulsed-field time-of-flight mass spectrometry of the skimmed cluster beam. Three types of positively charged sodium fluoride cluster are observed, each corresponding to a distinct physical situation: NanF+n-1 (purely ionic form), Nann+1F+n-1 (excess-electron form), and NanF+n (excess-hole form). The purely ionic clusters exhibit an abundance pattern similar to that observed in sputtering and fragmentation experiments and are explained by the stability of completed cubic microlattice structures. The excess-electron clusters, in contrast, exhibit very strong abundance maxima at n = 13 and 22, corresponding to the all-odd series (2n + 1 = jxkxl;j,k,l odd). Their high relative stability is explained by the ease of Na(0) loss except when the excess electron localizes in a lattice site to complete a cuboid structure. These may correspond to the internal F-center state predicted earlier. A localized electron model incorporating structural simulation results as account for the observed pattern. The excess-hole clusters, which had been proposed as intermediates in the ionization-induced fragmentation of neutral AHCs, exhibit a smaller variation in stability, indicating that the hole might not be well localized.

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

    OpenAIRE

    Zykova-Timan, T.; Ceresoli, D.; 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...

  7. Estimation of the critical temperatures and densities of molten alkali metal halides

    International Nuclear Information System (INIS)

    The critical temperatures and densities of the alkali halides MX (M Li-Cs; X = F-I) are calculated on the basis of the Rykov, Goldhammer and Philippov equations for estimating the liquids density. The modified Philippov equation is recommended as the equation for describing the experimental data on the density of the these melts in the temperature area Tmelt-Tc with the relative error of 0.1-0.2%

  8. Negative photoplastic effect due to the relaxed excited state of the F-center in alkali halides

    International Nuclear Information System (INIS)

    To make clear the mechanism of the photoplastic effect (PPE) in alkali halides containing F-centers, on the basis of the photochemical reaction of the F-center, temperature dependence of the PPE in KCl, and KBr and NaCl was studied from 95 K up to RT. The characteristic critical points thetasub(t)s in colored KCl and KBr were determined to be 110 and 190 K, respectively. Below thetasub(t) the sign of the PPE in both crystals was negative, i.e., decrement of the flow stress during light illumination was observed. Moreover, the thetasub(t)s were in good agreement with the temperature where the photoconductivities show remarkable increase in the course of the measurements. The negative PPE is explained in terms of the rotation of the principal strain axis of the relaxed state of the F-center having tetragonarity as to relax the stress around the edge dislocation coming closely. (author)

  9. Examination of the double layer contribution to the surface tension of alkali metal halides

    International Nuclear Information System (INIS)

    Analysis of surface tension on the liquid-vapor interface for alkali metal halides MX (M=Li-Cs; X=F-I) was made using microscopic theory, influence of the appearing double electric layer on the characteristic mentioned both for cationic and anionic substitutions was discussed. It is shown that for most MX salts the dependence of surface tension near melting point on the size difference of cation and anion can be adequately described using a model of mean-spheric approximation and parametrized density profile

  10. 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

  11. Molecular dispersion energy parameters for alkali and halide ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Reiser, S.; Deublein, S.; Hasse, H., E-mail: hans.hasse@mv.uni-kl.de [Laboratory of Engineering Thermodynamics, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Vrabec, J. [Thermodynamics and Energy Technology, University of Paderborn, 33098 Paderborn (Germany)

    2014-01-28

    Thermodynamic properties of aqueous solutions containing alkali and halide ions are determined by molecular simulation. The following ions are studied: Li{sup +}, Na{sup +}, K{sup +}, Rb{sup +}, Cs{sup +}, F{sup ?}, Cl{sup ?}, Br{sup ?}, and I{sup ?}. The employed ion force fields consist of one Lennard-Jones (LJ) site and one concentric point charge with a magnitude of ±1 e. The SPC/E model is used for water. The LJ size parameter of the ion models is taken from Deublein et al. [J. Chem. Phys. 136, 084501 (2012)], while the LJ energy parameter is determined in the present study based on experimental self-diffusion coefficient data of the alkali cations and the halide anions in aqueous solutions as well as the position of the first maximum of the radial distribution function of water around the ions. On the basis of these force field parameters, the electric conductivity, the hydration dynamics of water molecules around the ions, and the enthalpy of hydration is predicted. Considering a wide range of salinity, this study is conducted at temperatures of 293.15 and 298.15 K and a pressure of 1 bar.

  12. 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

  13. Formation of structured nanophases in halide crystals.

    Czech Academy of Sciences Publication Activity Database

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

    2011-01-01

    Ro?. 134, ?. 14 (2011), 144504/1-144504/7. ISSN 0021-9606 R&D Projects: GA AV ?R IAA100100806 Institutional research plan: CEZ:AV0Z10100521 Keywords : nanophase * halides * nucleation * spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.333, year: 2011

  14. From unexpected reactions to a new family of ionic co-crystals: the case of barbituric acid with alkali bromides and caesium iodide

    OpenAIRE

    Gobetto, Roberto; CHIEROTTI, Michele Remo

    2010-01-01

    Pressing solid barbituric acid with KBr to prepare samples for IR spectroscopy leads to the formation of an ionic co-crystal, in which the co-former is a classical ionic salt; co-crystal formation is also obtained with the other alkali bromides (LiBr, NaBr, RbBr and CsBr) and with caesium iodide. The simultaneous presence of alkali and halide ions affects the dissolution properties of barbituric acid in water.

  15. An Investigation of Ion-Pairing of Alkali Metal Halides in Aqueous Solutions Using the Electrical Conductivity and the Monte Carlo Computer Simulation Methods

    OpenAIRE

    Gujt, Jure; Bešter-Roga?, Marija; Hribar-Lee, Barbara

    2014-01-01

    The ion pairing is, in very dilute aqueous solutions, of rather small importance for solutions’ properties, which renders its precise quantification quite a laborious task. Here we studied the ion pairing of alkali halides in water by using the precise electric conductivity measurements in dilute solutions, and in a wide temperature range. The low-concentration chemical model was used to analyze the results, and to estimate the association constant of different alkali halide salts. It has bee...

  16. N ,N'-dimethylperylene-3,4,9,10-bis(dicarboximide) on alkali halide (001) surfaces

    Science.gov (United States)

    Fendrich, Markus; Lange, Manfred; Weiss, Christian; Kunstmann, Tobias; Möller, Rolf

    2009-05-01

    The growth of N ,N'-dimethylperylene-3,4,9,10-bis(dicarboximide) (DiMe-PTCDI) on KBr(001) and NaCl(001) surfaces has been studied. Experimental results have been achieved using frequency modulation atomic force microscopy at room temperature under ultrahigh vacuum conditions. On both substrates, DiMe-PTCDI forms molecular wires with a width of 10nm, typically, and a length of up to 600nm at low coverages. All wires grow along either the [110] direction (or [11¯0] direction, respectively) of the alkali halide (001) substrates. There is no wetting layer of molecules: atomic resolution of the substrates can be achieved between the wires. The wires are mobile on KBr but substantially more stable on NaCl. A p(2×2) superstructure in a brickwall arrangement on the ionic crystal surfaces is proposed based on electrostatic considerations. Calculations and Monte Carlo simulations using empirical potentials reveal possible growth mechanisms for molecules within the first layer for both substrates, also showing a significantly higher binding energy for NaCl(001). For KBr, the p(2×2) superstructure is confirmed by the simulations; for NaCl, a less dense, incommensurate superstructure is predicted.

  17. Physics of Solid and Liquid Alkali Halide Surfaces Near the Melting Point

    CERN Document Server

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

    2005-01-01

    This paper presents a broad theoretical and simulation study of the high temperature behavior of crystalline alkali halide surfaces typified by NaCl(100), of the liquid NaCl surface near freezing, and of the very unusual partial wetting of the solid surface by the melt. Simulations are conducted using two-body rigid ion BMHFT potentials, with full treatment of long-range Coulomb forces. After a preliminary check of the description of bulk NaCl provided by these potentials, which seems generally good even at the melting point, we carry out a new investigation of solid and liquid surfaces. Solid NaCl(100) is found in this model to be very anharmonic and yet exceptionally stable when hot. It is predicted by a thermodynamic integration calculation of the surface free energy that NaCl(100) should be a well ordered, non-melting surface, metastable even well above the melting point. By contrast, the simulated liquid NaCl surface is found to exhibit large thermal fluctuations and no layering order. In spite of that, ...

  18. Calculation of intraband electron and band-to-band hole luminescence spectra of some alkali halide crystals under pulse excitation by dense electron and laser beams of nano- and picosecond duration

    International Nuclear Information System (INIS)

    Theoretical calculation of spectra of two new types of fundamental radioluminescence of dielectrics - intraband electron and band-to-band hole ones - was conducted. These types of radioluminescence were revealed and studied experimentally due to the use of two high-power nano- and picosecond radiation sources for dielectric excitation - high-current electron accelerators and lasers with generators of ultraviolet harmonics. Satisfactory agreement of calculated spectra with ones, measured experimentally, was achieved. Correlation of calculation results with experimental data enabled to determine some important parameters of electron spectrum and specifically the upper boundary of passive region for conduction band ionization for CsI crystals. 27 refs., 8 figs

  19. H2O- center in alkali halides with OH-: properties and formation kinetics-destruction after radiation damage

    International Nuclear Information System (INIS)

    In order to understand the basic mechanisms that are responsible for the thermal formation and thermal destruction of the primary and secondary defects after low energy radiation damage in alkali halide crystals doped with OH-, the production of defects by pulse annealing in KCl:OH- and KBr:OH- was studied. These thermal processes were studied over a wide range of temperatures (52-300 K), and the several hydrogen reaction products were identified by their characteristic electronic absorption (visible-ultraviolet). Besides the well known substitucional and interstitial H0 sub(i) and H- defects, a new hydrogen defect, U2 sub(x) center, was discovered after the thermal destruction of the U2 centers. It is characterized by a new structureless eletronic absorption band (UV) at 45000 cm-1 in KCl and 40000 cm-1 in KBr. From this experimental observations it was proposed that the U2 sub(x) center is constituted by one H0 sub(i) center trapped by a substitucional OH-, without disturbing the electronic transition of the OH-. H2O- centers in KCl or H2O- and U centers in KBr are produced by thermal destruction of the U2 sub(x) centers. Furthermore, it was observed that thermal desctruction of H2O- centers produced: F(15%), U(60%) and OH- (25%) centers in KCl and F (approximated 100%) in KBr. At the end of this thermal process (at 300 K), 90 to 95% of the iitial OH- centers were restored at the expenses of F and U centers. Several new properties of the H2O- defect were found and studied. (Author)

  20. 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

  1. Viscometric and thermodynamic studies of interactions in ternary solutions containing sucrose and aqueous alkali metal halides at 293.15, 303.15 and 313.15 K

    Indian Academy of Sciences (India)

    Reena Gupta; Mukhtar Singh

    2005-05-01

    Viscosities and densities of sucrose in aqueous alkali metal halide solutions of different concentrations in the temperature range 293.15 to 313.15 K have been measured. Partial molar volumes at infinite dilution ($V_2^0$) of sucrose determined from apparent molar volume ($\\phi_v$) have been utilized to estimate partial molar volumes of transfer ($V^0_{2,tr}$) for sucrose from water to alkali metal halide solutions. The viscosity data of alkali metal halides in purely aqueous solutions and in the presence of sucrose at different temperatures (293.15, 303.15 and 313.5 K) have been analysed by the Jones-Dole equation. The nature and magnitude of solute-solvent and solute-solute interactions have been discussed in terms of the values of limiting apparent molar volume ($\\phi^0_v$), slope ($S_v$) and coefficients of the Jones-Dole equation. The structuremaking and structure-breaking capacities of alkali metal halides in pure aqueous solutions and in the presence of sucrose have been ascertained from temperature dependence of $\\phi^0_v$.

  2. 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.

  3. On the interpretation of luminescence of lead halide crystals.

    Czech Academy of Sciences Publication Activity Database

    Babin, V.; Krasnikov, A.; Nikl, Martin; Stolovits, A.; Zazubovich, S.

    2002-01-01

    Ro?. 229, ?. 3 (2002), s. 1295-1304. ISSN 0370-1972 Institutional research plan: CEZ:AV0Z1010914 Keywords : luminescence * lead halide * exciton Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2002

  4. 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 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)

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

    Directory of Open Access Journals (Sweden)

    A. Pérez-Rodríguez

    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.

  6. 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.

  7. Conductometric study of some alkali metal halides in (dimethyl sulfoxide + acetonitrile) at T = 298.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Mahendra Nath [Department of Chemistry, North Bengal University, Darjeeling 734013 (India)], E-mail: mahendraroy2002@yahoo.co.in; Banerjee, Ashis; Das, Rajesh Kumar [Department of Chemistry, North Bengal University, Darjeeling 734013 (India)

    2009-11-15

    Electrolytic conductivities of some alkali metal halides, MX (M{sup +} = Li{sup +}, Na{sup +}, and K{sup +}; X{sup -} = Cl{sup -}, Br{sup -}, and I{sup -}), NaBPh{sub 4} and Bu{sub 4}NBr have been investigated in (20, 40, and 60) mass% {l_brace}dimethyl sulfoxide (DMSO) in DMSO + acetonitrile{r_brace} at T = 298.15 K. The conductance results have been analyzed by the Fuoss-conductance-concentration equation in terms of the limiting molar conductance {lambda}{sup o} the association constant K{sub A} and the association diameter R. The ionic contributions to the limiting molar conductance have been estimated using Bu{sub 4}NBPh{sub 4} as the 'reference electrolyte'. The association constant K{sub A} tends to increase in the order mass percent 20 < 40 < 60 DMSO in (DMSO + acetonitrile) which is explained by the thermodynamic parameter {delta}G{sup o} and Walden product {lambda}{sup o}{eta}. The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvents.

  8. 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.; Skaarup, Steen

    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, whil...

  9. 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.)

  10. Evidence for New Excess Electron Localization Sites in Na{sub {ital n}}F{sub {ital n}{minus}1 } Alkali-Halide Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Durand, G.; Spiegelmann, F. [Laboratoire de physique quantique (UMR 5626 CNRS-UPS), IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F31062 Toulouse Cedex 4 (France); Labastie, P.; LHermite, J.; Poncharal, P. [Laboratoire CAR (UMR 5589 CNRS-UPS), IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F31062 Toulouse cedex 4 (France)

    1997-07-01

    This Letter examines new types of localization sites for an excess electron in finite alkali-halide clusters resulting from defects on cuboidal structures, namely {open_quotes}edge states,{close_quotes} R center, and other surface defects. We present theoretical calculations on Na{sub n}F {sub n{minus}1} clusters with one excess electron. Comparisons with experimental results are presented for different cluster sizes (n=17 , 23, 28, and 29). Structures with edge or surface defects are relevant for n=23 , 28, and 29. {copyright} {ital 1997} {ital The American Physical Society}

  11. Effect of alkali and alkaline earth metal oxides on crystal growth rate of wollastonite crystals in melt

    International Nuclear Information System (INIS)

    The effect of oxide additions of alkali (Li, Na, K) and alkaline earth (Mg, Sr, Ba) metals on growth rate of wollastonite CaSiO3 crystals in melt is studied. It has been found that low oxide additions of alkali and alkaline earth metals in melt can increase as well as decrease the wollastonite crystals growth

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. Advances in the growth of alkaline-earth halide single crystals for scintillator detectors

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, Lynn A [ORNL; Ramey, Joanne Oxendine [ORNL; Kolopus, James A [ORNL; Neal, John S [ORNL; Cherepy, Nerine [Lawrence Livermore National Laboratory (LLNL); Payne, Stephen A. [Lawrence Livermore National Laboratory (LLNL); Beck, P [Lawrence Livermore National Laboratory (LLNL); Burger, Arnold [Fisk University, Nashville; Rowe, E [Fisk University, Nashville; Bhattacharya, P. [Fisk University, Nashville

    2014-01-01

    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 crystal-growth 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.

  19. 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.)

  20. 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)

  1. Interaction of dislocations with radiation defects in alkaline-halide crystals

    International Nuclear Information System (INIS)

    The studies on interaction of dislocations with point defects in the alkaline-halide crystal are carried out with the purpose of clarifying the nature of the deformation-stimulated luminescence (DSL) and radiation strengthening mechanism. The KCl monocrystals were irradiated by the gamma-quanta (the absorbed dose is of 2 MGy). The information on the hole centers is obtained by analysis of the thermostimulated luminescence curves within the temperature range of 300-540 K. The load on the sample was registered simultaneously with studying the DSL luminescence intensity. It is established that at the room temperature of the DSL crystals the KCl is conditioned by the Vz and V2 hole centers. Dislocations destroy the Vz and V2 centers, which results in the VF- and H-centers, recombining with the F-type centers formation. Thus, the DSL is the consequence of destroying the V2 and Vz hole centers

  2. 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 ...

  3. Lithium-selective phosphine oxide-based ditopic receptors show enhanced halide binding upon alkali metal ion coordination†

    OpenAIRE

    Gavette, Jesse V.; Lara, Juven; Reling, Linda L.; Michael M. Haley; Darren W. Johnson

    2012-01-01

    Previous work on a ditopic receptor based on a tripodal phosphine oxide core demonstrated preferential enhancement of bromide binding over chloride or iodide in the presence of lithium cation. Current studies on an elongated receptor provide evidence that preferential bromide binding enhancement in the presence of lithium cation is common to this receptor class in general, and that lengthening of the receptor results in an overall increase in halide association. Furthermore, the extended rece...

  4. 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.

  5. 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

  6. 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.)

  7. 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

  8. 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)

  9. 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.)

  10. Study of growth conditions influence on shape and position of crystal/melt interface during crystal growth of ternary halides by vertical bridgman method.

    Czech Academy of Sciences Publication Activity Database

    Cihlá?, Antonín; Král, Robert

    Bratislava : Slovak Expert Group of Solid State Chemistry and Physics, 2011 - (Koman, M.; Jorík, V.), 32-33 ISBN 978-80-8134-002-4. [Joint Seminar – Development of materials science in research and education(DMRSE)/21.th./. Kežmarské Žlaby (SK), 29.08.2011-02.09.2011] R&D Projects: GA AV ?R KJB200100901 Institutional research plan: CEZ:AV0Z10100521 Keywords : crystal growth * growth conditions * vertical Bridgman method * crystal melt interface * ternary halid Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. 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.

  12. Introducing alkali impurities into BaFBr:Eu2+ crystals and their effect on photo-stimulated luminescence

    International Nuclear Information System (INIS)

    In alkali doped BaFBr:Eu2+ a considerable increase of photostimulated luminescence (PSL) intensity is observed. Upon Na doping the intensity of the PSL is increased by a factor of 15 in contrast to undoped samples. Moreover, the PSL peak shifted on 0.08 eV in the red region of spectrum upon Na doping. The potassium and rubidium doping results in the same effects, but with less efficiency. We prepared undoped BaFBr:Eu2+ crystals and those doped with varied concentrations of NaF, KF, RbF. The concentrations of alkali, which we doped before growth, were in the region of 0.1-5%. Atomic-Emission Analysis shows that the real alkali concentrations in the crystals are 0.0002-0.0025%. However, even such a small alkali doping concentration in BaFBr:Eu2+ influences effectively the PSL process

  13. 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.

  14. 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

  15. Silver alkali halide glasses and a vitreous analog of the RbAg/sub 4/I/sub 5/ superionic conductor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.; Angell, C.A.; Sundar, H.G.K.

    1985-05-01

    We report the existence of silver halide-rich glasses of a type not previously recognized. These contain only monovalent halides and represent perhaps the simplest ionic glasses yet realized. Despite the lack of the usual oxyanion matrix the new glasses show room temperature conductances which equal or exceed those of the best Ag/sup +/ glasses yet reported. Cu/sup +/ analogues have also been prepared. At the high conducting extreme apparently lies a vitreous state analog of the well-known crystalline conductor RbAg/sub 4/I/sub 5/. A crystalline analog of the latter FIC, CsAg/sub 4/(I /SUB 0.45/ C1 /SUB 0.55/ )/sub 5/ forms metastably on careful devitrification of the glass. Like its prototype, it has a very high conductivity and exhibits a sharp C /SUB p/ anomaly at low temperatures, -77/sup 0/C, in the vicinity of which the activation energy for conductance changes abruptly.

  16. Preparation and Single-Crystal X-Ray Structures of Four Related Mixed-Ligand 4-Methylpyridine Indium Halide Complexes

    Science.gov (United States)

    Hepp, Aloysius F.; Clark, Eric B.; Schupp, John D.; Williams, Jennifer N.; Duraj, Stan A.; Fanwick, Philip E.

    2013-01-01

    We describe the structures of four related indium complexes obtained during synthesis of solid-state materials precursors. Indium adducts of halides and 4-methylpyridine, InX3(pic)3 (X = Cl, Br; pic = 4-methylpyridine) consist of octahedral molecules with meridional (mer) geometry. Crystals of mer-InCl3(pic)3 (1) are triclinic, space group P1(bar) (No. 2), with a = 9.3240(3), b = 13.9580(6), c = 16.7268 (7) A, alpha = 84.323(2), beta = 80.938(2), gamma = 78.274(3)Z = 4, R = 0.035 for 8820 unique reflections. Crystals of mer-InBr3(pic)3 (2) are monoclinic, space group P21/n (No. 14), with a = 15.010(2), b = 19.938(2), c = 16.593(3), beta = 116.44(1)Z = 8, R = 0.053 for 4174 unique reflections. The synthesis and structures of related compounds with phenylsulfide (chloride) (3) and a dimeric complex with bridging hydroxide (bromide) (4) coordination is also described. Crystals of trans-In(SC6H5)Cl2(pic)3 (3) are monoclinic, space group P21/n (No. 14), with a = 9.5265(2), b = 17.8729(6), c = 13.8296(4), beta = 99.7640(15)Z = 4, R = 0.048 for 5511 unique reflections. Crystals of [In(mu-OH)Br2(pic)22 (4) are tetragonal, space group = I41cd (No. 110) with a = 19.8560(4), b = 19.8560(4), c = 25.9528(6), Z = 8, R = 0.039 for 5982 unique reflections.

  17. Basic properties of the F-type centers in halides, oxides and perovskites

    International Nuclear Information System (INIS)

    We present a short survey of the optical properties of primary radiation-induced point defects in alkali halides, simple oxides and some ABO3 perovskites. We discuss in details the optical properties of single electron F and F+ centers in rock-salt (f.c.c.) alkali halides and oxides and show that the Mollwo-Ivey law well-known for the F-type centers in alkali halides may be extended for other rock-salt structure insulators. We also discuss the major differences in point defect production mechanisms in halides and oxides. We show that the Rabin-Klick diagram may be generalized for a whole family of alkali halides. The F-type center migration and aggregation into metal colloids in alkali halides and oxides is also discussed.

  18. Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growth

    KAUST Repository

    Saidaminov, Makhsud I.

    2015-10-20

    Here we show the retrograde solubility of various hybrid perovskites through the correct choice of solvent(s) and report their solubility curves. Retrograde solubility enables to develop inverse temperature crystallization of FAPbX3 (FA = HC(NH2)2+, X = Br?/I?). FAPbI3 crystals exhibit a 1.4 eV bandgap – considerably narrower than their polycrystalline counterparts.

  19. Role of the crystallization substrate on the photoluminescence properties of organolead mixed halides perovskites

    OpenAIRE

    Michele Bastiani; Valerio D’Innocenzo; Samuel D. Stranks; Henry J. Snaith; Annamaria Petrozza

    2014-01-01

    We have fabricated CH3NH3PbI3-xCl x 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....

  20. Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growth.

    Science.gov (United States)

    Saidaminov, Makhsud I; Abdelhady, Ahmed L; Maculan, Giacomo; Bakr, Osman M

    2015-12-01

    Here we show the retrograde solubility of various hybrid perovskites through the correct choice of solvent(s) and report their solubility curves. Retrograde solubility enables to develop inverse temperature crystallization of FAPbX3 (FA = HC(NH2)2(+), X = Br(-)/I(-)). FAPbI3 crystals exhibit a 1.4 eV bandgap - considerably narrower than their polycrystalline counterparts. PMID:26511771

  1. Structural morphology of analbite: the influence of the substitution of K by Na on the crystal morphology of alkali feldspars

    International Nuclear Information System (INIS)

    The habit of the theoretical growth form of monoclinic high sanidine (KAlSi3O8) calculated from the attachment energies in an electrostatic point charge model is most similar to that of the alpine vein potassium feldspar called adularia. The effect on the crystal growth of alkali feldspar due to the substitution of K by Na has been investigated by the calculation of the attachment energies of analbite (NaAlSi3O8), which is triclinic with a disordered Si/Al distribution. The theoretical growth form of analbite consists of {110}, {1anti 10}, {001}, {010} and, as additional minor forms, {021} and {0anti 21}. Hence other habits than the Adularia type cannot be explained by the crystal structure of disordered alkali feldspars. Either ordering of Si and Al during the growth or external factors, such as impurities or supersaturation, must be examined as possible habit modifiers. They must be responsible for the platy Finisterre, the elongated Baveno or the thick prismatic Carlsbad habit of many alkali feldspar crystals

  2. Systematic hardness measurements on single crystals and polycrystalline blanks of cesium halides

    Indian Academy of Sciences (India)

    D B Sirdeshmukh; P Geeta Krishna; K G Subhadra

    2002-06-01

    Vickers and knoop hardness measurements were carried out on CsBr and CsI single crystals. Polycrystalline blanks of CsCl, CsBr and CsI were prepared by melting and characterized by X-ray diffraction. Vickers hardness measurements were carried out on these blanks. The hardness values were correlated with the lattice constant and the Schottky defect formation energy.

  3. 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

  4. Visualizing Carrier Diffusion in Individual Single-Crystal Organolead Halide Perovskite Nanowires and Nanoplates.

    Science.gov (United States)

    Tian, Wenming; Zhao, Chunyi; Leng, Jing; Cui, Rongrong; Jin, Shengye

    2015-10-01

    Single-crystal CH3NH3PbX3 (X = I(-), Cl(-), Br(-)) perovskite nanowires (NWs) and nanoplates (NPs), which demonstrate ultracompact sizes and exceptional photophysical properties, offer promises for applications in nanoscale photonics and optoelectronics. However, traditional electronic and transient techniques are limited by the dimensions of the samples, and characterizations of the carrier behavior (diffusion coefficient, charge mobility and diffusion length) in these NWs and NPs are extremely difficult. Herein, we report the direct visualization of the carrier diffusion process in individual single-crystal CH3NH3PbI3 and CH3NH3PbBr3 NWs and NPs using time-resolved and photoluminescence-scanned imaging microscopy. We report the diffusion coefficient (charge motility), which varies significantly between different NWs and NPs, ranging from 1.59 to 2.41 cm(2) s(-1) (56.4 to 93.9 cm(2) V(-1) s(-1)) for CH3NH3PbI3 and 0.50 to 1.44 cm(2) s(-1) (19.4 to 56.1 cm(2) V(-1) s(-1)) for CH3NH3PbBr3 and find this variation is independent of the shape and size of the sample. The average diffusion length is 14.0 ± 5.1 ?m for CH3NH3PbI3 and 6.0 ± 1.6 ?m for CH3NH3PbBr3. These results provide information that is essential for the practical applications of the single-crystal perovskite NWs and NPs, and the imaging microscopy may also be applicable to other optoelectronic materials. PMID:26390276

  5. 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.

  6. 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.

  7. Theory of Distinct Crystal Structures of Polymerized Fullerides AC60, A=K, Rb, Cs the Specific Role of Alkalis

    CERN Document Server

    Michel, K H

    2000-01-01

    The polymer phases of AC60 form distinct crystal structures characterized by the mutual orientations of the (C60-)n chains. We show that the direct electric quadrupole interaction between chains always favors the orthorhombic structure Pmnn with alternating chain orientations. However the specific quadrupolar polarizability of the alkali metal ions leads to an indirect interchain coupling which favors the monoclinic structure I2/m with equal chain orientations. The competition between direct and indirect interactions explains the structural difference between KC60 and RbC60, CsC60.

  8. Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts

    OpenAIRE

    Guino-o, Marites A.; Talbot, Meghan O.; Slitts, Michael M.; Pham, Theresa N.; Audi, Maya C.; Daron E. Janzen

    2015-01-01

    To investigate the predominant inter­molecular inter­actions in 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts, five salts were prepared and crystallographically characterized. The halide ions generally inter­act with the H atoms of the triazolium cation forming extended sheets. When the aryl ring lies on the plane of the triazolium cation, the cationic core formed two-dimensional networks that lead into layer-like assembled structures. The triazolium core exhibits ?–? inter­actions with the...

  9. Complexing in binary molten halide systems with a common anion, containing sodium halides

    International Nuclear Information System (INIS)

    Analysis of meltability diagrams of binary halide systems with a common anion published in literature permitted studying the interaction in sodium halide melts NaX (X = F-I) and halides of alkali, alkaline-earth, transition and rare earth elements, as well as uranium and thorium. It was ascertained that in most systems enhancement of polarizing effect of cation in the melt involves intensification of complexing. Transition from ideal to non-ideal eutectic systems and further to systems with incongruently and congruently melting compounds was pointed out, as well

  10. 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

  11. 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)

  12. 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.

  13. Synthesis, characterization and computational studies of zinc(ii)-halide complexes with a bidentate Schiff base ligand (2,5-MeO-ba)2En: the crystal structure of (2,5-MeO-ba)2En.

    Czech Academy of Sciences Publication Activity Database

    Khalaji, A.D.; Mighani, H.; Gholinejad, M.; Grivani, G.; Jalali Akerdi, S.; Fejfarová, Karla; Dušek, Michal

    2013-01-01

    Ro?. 54, ?. 4 (2013), s. 766-773. ISSN 0022-4766 Institutional research plan: CEZ:AV0Z10100521 Keywords : zinc(II) halides * Schiff base * crystal structure * density functional theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.501, year: 2013

  14. Structure and energetics of trivalent metal halides

    International Nuclear Information System (INIS)

    Metal trihalide (MX3) systems represent a stern challenge in terms of constructing transferable potential models. Starting from a previously published set of potentials, 'extended' ionic models are developed which, at the outset, include only anion polarization. Deficiencies in these models, particularly for smaller (highly polarizing) cations, axe shown to be significant. For example, crystal structures different to those observed experimentally axe adopted. The potentials axe improved upon by reference to ab initio information available for alkali halides with the 'constraint' that the parameters transfer systematically in a physically transparent manner, for example, in terms of ion radii. The possible influence of anion compression ('breathing') and the relative abundance of anion-anion interactions are considered. Simulation techniques axe developed to allow for the effective simulation of any system symmetry and for the study of transitions between different crystals (constant stress). The developed models are fully tested for a large range of metal trichloride (MCl3) systems. Particular attention is paid to the comparison with recent neutron and X-ray diffraction data on the liquid state. Polarization effects axe shown to be vital in reproducing strong experimental features. The excellent agreement between simulation and experiment allows for differences in experimental procedures to be highlighted. The transferability is further tested by modelling mixtures of the lanthanides with alkali halides with potentials unchanged from the pure systems. The complex evolution of the melt structure is highlighted as the concentration of MCl3 increases. The effectiveness of the models is tested by reference to dynamical properties. Particular attention is paid to the comparison with Raman scattering data available for a wide range of systems and mixture concentrations. The simulated spectra are generated both by a simple molecular picture of the underlying vibrations and by a more Complex (fluctuating polarizability) model in which the spectra are broken down into contributions from different mechanisms. This comparison allows for the validity of treating network-like systems as a series of 'isolated' molecules to be assessed. The transferability of the potentials is pushed to the limits by modelling metal tribromides, in which the parameters are obtained from the trichlorides by the same simple scaling arguments. (author)

  15. 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

  16. 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.

  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. Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts.

    Science.gov (United States)

    Guino-O, Marites A; Talbot, Meghan O; Slitts, Michael M; Pham, Theresa N; Audi, Maya C; Janzen, Daron E

    2015-06-01

    The asymmetric units for the salts 4-(4-fluoro-phen-yl)-1-isopropyl-1,2,4-triazol-1-ium iodide, C11H13FN3 (+)·I(-), (1), 1-isopropyl-4-(4-methyl-phen-yl)-1,2,4-triazol-1-ium iodide, C12H16N3 (+)·I(-), (2), 1-isopropyl-4-phenyl-1,2,4-triazol-1-ium iodide, C11H14N3 (+)·I(-), (3), and 1-methyl-4-phenyl-1,2,4-triazol-1-ium iodide, C9H10N3 (+)·I(-), (4), contain one cation and one iodide ion, whereas in 1-benzyl-4-phenyl-1,2,4-triazol-1-ium bromide monohydrate, C15H14N3 (+)·Br(-)·H2O, (5), there is an additional single water mol-ecule. There is a predominant C-H?X(halide) inter-action for all salts, resulting in a two-dimensional extended sheet network between the triazolium cation and the halide ions. For salts with para-substitution on the aryl ring, there is an additional ?-anion inter-action between a triazolium carbon and iodide displayed by the layers. For salts without the para-substitution on the aryl ring, the ?-? inter-actions are between the triazolium and aryl rings. The melting points of these salts agree with the predicted substituent inductive effects. PMID:26090137

  19. Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts

    Directory of Open Access Journals (Sweden)

    Marites A. Guino-o

    2015-06-01

    Full Text Available The asymmetric units for the salts 4-(4-fluorophenyl-1-isopropyl-1,2,4-triazol-1-ium iodide, C11H13FN3+·I?, (1, 1-isopropyl-4-(4-methylphenyl-1,2,4-triazol-1-ium iodide, C12H16N3+·I?, (2, 1-isopropyl-4-phenyl-1,2,4-triazol-1-ium iodide, C11H14N3+·I?, (3, and 1-methyl-4-phenyl-1,2,4-triazol-1-ium iodide, C9H10N3+·I?, (4, contain one cation and one iodide ion, whereas in 1-benzyl-4-phenyl-1,2,4-triazol-1-ium bromide monohydrate, C15H14N3+·Br?·H2O, (5, there is an additional single water molecule. There is a predominant C—H...X(halide interaction for all salts, resulting in a two-dimensional extended sheet network between the triazolium cation and the halide ions. For salts with para-substitution on the aryl ring, there is an additional ?–anion interaction between a triazolium carbon and iodide displayed by the layers. For salts without the para-substitution on the aryl ring, the ?–? interactions are between the triazolium and aryl rings. The melting points of these salts agree with the predicted substituent inductive effects.

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

    OpenAIRE

    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....

  1. Synthesis and crystal structure of alkali metal diamido dioxosilicates M2SiO2(NH2)2 with M corresponds to K, Rb and Cs

    International Nuclear Information System (INIS)

    SiO2 - ?-quartz - reacts with alkali metal amides MNH2 (M corresponds to K, Rb, and Cs) in molar ratios from 1:2 to 1:10 at 450 C ? T ? 600 C and P(NH3) = 6 kbar in autoclaves to diamidodioxosilicates M[SiO2(NH2)2]. Crystals of the colourless compounds which hydrolyze rapidly were investigated by X-ray methods. (orig.)

  2. Mixed alkali and alkaline-earth borate Li2Sr4B12O23 single crystal

    Science.gov (United States)

    Reshak, A. H.

    2015-10-01

    A comprehensive theoretical investigation of the electronic band structure, density of states, electron charge density distribution and the optical properties for mixed alkali and alkaline-earth borate Li2Sr4B12O23 (LSBO) single crystals were performed. The experimental geometrical structure was optimized by minimizing the forces acting on each atom. Calculations were performed using the full potential linear augmented plane wave plus local orbitals (FPLAPW + lo) method within the local density approximation (LDA), generalized gradient approximation (GGA) and the recently modified Becke-Johnson potential (mBJ). Our calculations show that LSBO crystal is a direct band gap semiconductor. The calculated band gap is 4.64 eV (LDA), 4.92 eV (GGA) and 5.51 eV (mBJ). An earlier calculation using the CASTEP code within LDA obtained a band gap of about 4.66 eV. To overcome the well-known LDA underestimation of the energy gap we have used GGA and mBJ . We find that mBJ succeed by large amount in bringing the calculated bond lengths in good agreement with the experimental data. Also we found that using mBJ to calculate the optical properties gives a birefringence of about 0.068 (at ? = 586.5 nm) in excellent agreement with the experimental data (0.068 at ? = 586.5 nm). Therefore, we believe that the mBJ calculations reported here show excellent agreement with the experimental data.

  3. 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

  4. Nitrate (chloride) melts as media for crystal growth of complex phosphates of alkali and trivalent metals

    Science.gov (United States)

    Livitska, Oksana; Strutynska, Nataliia; Zatovsky, Igor; Slobodyanik, Nikolai; Odinets, Eugen

    2016-01-01

    The interaction in the molten systems MIPO3-MIII2O3-MINO3 (MICl) (MI - Na, K; MIII - Al, Fe, Y, Bi) was investigated at molar ratios P/MIII=1 or 3 at the temperatures 400 °C (for MINO3) or 810 °C (for MICl). Formation conditions of complex phosphates MI3MIII2(PO4)3 and MI3MIII(PO4)2 (MI - Na, K; MIII - Al, Fe, Bi) were established. It was shown that the crystal size of obtained phosphates can be controlled by using different salt melts. The synthesized compounds were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, Optical microscopy and Scanning electron microscopy with Energy-dispersive X-ray spectroscopy. Differential thermal data for Na3Bi(PO4)2 and Na3Fe(PO4)2 showed congruent and incongruent melting, respectively.

  5. Metal-halide mixtures for latent heat energy storage

    Science.gov (United States)

    Chen, K.; Manvi, R.

    1981-01-01

    Alkali metal and alkali halide mixtures are identified which may be suitable for thermal energy storage at temperatures above 600 C. The use of metal-halides is appropriate because of their tendency to form two immiscible melts with a density difference, which reduces scale formation and solidification on heat transfer surfaces. Also, the accumulation of phase change material along the melt interface is avoided by the self-dispersing characteristic of some metal-halides, in particular Sr-SrCl2, Ba-BaCl2, and Ba-BaBr2 mixtures. Further advantages lie in their high thermal conductivities, ability to cope with thermal shock, corrosion inhibition, and possibly higher energy densities.

  6. Crystal Structures of Polymerized Fullerides AC60, A=K, Rb, Cs and Alkali-mediated Interactions

    CERN Document Server

    Verberck, B; Nikolaev, A V

    2002-01-01

    Starting from a model of rigid interacting C60 polymer chains on an orthorhombic lattice, we study the mutual orientation of the chains and the stability of the crystalline structures Pmnn and I2/m. We take into account i) van der Waals interactions and electric quadrupole interactions between C60 monomers on different chains as well as ii) interactions of the monomers with the surrounding alkali atoms. The direct interactions i) always lead to an antiferrorotational structure Pmnn with alternate orientation of the C60 chains in planes (001). The interactions ii) with the alkalis consist of two parts: translation-rotation (TR) coupling where the orientations of the chains interact with displacements of the alkalis, and quadrupolar electronic polarizability (ep) coupling, where the electric quadrupoles on the C60 monomers interact with induced quadrupoles due to excited electronic d states of the alkalis. Both interactions ii) lead to an effective orientation-orientation interaction between the C60 chains and ...

  7. Halide Adsorption on Single-crystal Silver Substrates: Dynamic Simulations and ab-initio Density-functional Theory

    OpenAIRE

    Mitchell, S. J.; Wang, Sanwu; Rikvold, P. A.

    2001-01-01

    We investigate the static and dynamic behaviors of a Br adlayer electrochemically deposited onto single-crystal Ag(100) using an off-lattice model of the adlayer. Unlike previous studies using a lattice-gas model, the off-lattice model allows adparticles to be located at any position within a two-dimensional approximation to the substrate. Interactions with the substrate are approximated by a corrugation potential. Using Density Functional Theory (DFT) to calculate surface b...

  8. 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

  9. NMR spectra of alkali and halogen nuclei in alkali and halogen salts

    International Nuclear Information System (INIS)

    NMR signals of 7Li, 23Na, 35Cl, 39K, 79Br, 87Rb and 127I have been measured in various alkali and halogen salt powders relative to well defined aqueous solutions. With the known shielding constants of some of these solutions the nuclear magnetic shielding constants of the alkali and values of the shielding constants in alkali halides do not agree even in the order of magnitude with the experimental ones in some cases. For 23Na first-order and second-order quadrupole patterns have been observed and the quadrupole coupling constants are given. (orig.) 891 WBU

  10. Halide Adsorption on Single-crystal Silver Substrates Dynamic Simulations and ab-initio Density-functional Theory

    CERN Document Server

    Mitchell, S J; Rikvold, P A; Wang, Sanwu

    2002-01-01

    We investigate the static and dynamic behaviors of a Br adlayer electrochemically deposited onto single-crystal Ag(100) using an off-lattice model of the adlayer. Unlike previous studies using a lattice-gas model, the off-lattice model allows adparticles to be located at any position within a two-dimensional approximation to the substrate. Interactions with the substrate are approximated by a corrugation potential. Using Density Functional Theory (DFT) to calculate surface binding energies, a sinusoidal approximation to the corrugation potential is constructed. A variety of techniques, including Monte Carlo and Langevin simulations, are used to study the behavior of the adlayer. The lateral root-mean-square (rms) deviation of the adparticles from the binding sites is presented along with equilibrium coverage isotherms, and the thermally activated Arrhenius barrier-hopping model used in previous dynamic Monte Carlo simulations is tested.

  11. Casting of halide and fluoride alloys for laser windows. Semiannual technical report No. 1

    Energy Technology Data Exchange (ETDEWEB)

    Newberg, R.T.; Pappis, J.

    1974-10-15

    The problem of residual strain in castings of alkali halides (KCl and SrCl/sub 2/-doped KCl) and alkaline earth fluorides (CaF/sub 2/) has been overcome by the development of proper annealing and slow cooling procedures. Large castings (5/sup 1///sub 2/ in. dia) of CaF/sub 2/ and small castings (3 in. dia) of SrF/sub 2/ have been produced with low optical absorption coefficients at 5.25 ..mu..m. High quality CaF/sub 2/ castings have been obtained by using as starting material either high purity single crystal chips or ''reagent'' grade powder that has been subjected to reactive atmosphere processing (RAP) in teflon vapors.

  12. Structural effects in molecular metal halides.

    Science.gov (United States)

    Hargittai, Magdolna

    2009-03-17

    Metal halides are a relatively large class of inorganic compounds that participate in many industrial processes, from halogen metallurgy to the production of semiconductors. Because most metal halides are ionic crystals at ambient conditions, the term "molecular metal halides" usually refers to vapor-phase species. These gas-phase molecules have a special place in basic research because they exhibit the widest range of chemical bonding from the purely ionic to mostly covalent bonding through to weakly interacting systems. Although our focus is basic research, knowledge of the structural and thermodynamic properties of gas-phase metal halides is also important in industrial processes. In this Account, we review our most recent work on metal halide molecular structures. Our studies are based on electron diffraction and vibrational spectroscopy, and increasingly, we have augmented our experimental work with quantum chemical computations. Using both experimental and computational techniques has enabled us to determine intriguing structural effects with better accuracy than using either technique alone. We loosely group our discussion based on structural effects including "floppiness", relativistic effects, vibronic interactions, and finally, undiscovered molecules with computational thermodynamic stability. Floppiness, or serious "nonrigidity", is a typical characteristic of metal halides and makes their study challenging for both experimentalists and theoreticians. Relativistic effects are mostly responsible for the unique structure of gold and mercury halides. These molecules have shorter-than-expected bonds and often have unusual geometrical configurations. The gold monohalide and mercury dihalide dimers and the molecular-type crystal structure of HgCl(2) are examples. We also examined spin-orbit coupling and the possible effect of the 4f electrons on the structure of lanthanide trihalides. Unexpectedly, we found that the geometry of their dimers depends on the f electron configuration. Metal halides are unique in exhibiting strong vibronic interactions such as the Jahn-Teller effect and the related Renner-Teller effect. Some metal trihalide molecules have an almost T-shape due to static Jahn-Teller distortions. The nonlinear structure with a 150 degree bond angle of the chromium dichloride molecule demonstrates the Renner-Teller effect. Finally, we present a few examples of unknown structures that appear to be thermodynamically stable, including gold and silver triiodides and all silver subhalides. The combination of experimental and computational techniques has brought new insights to the structural chemistry of metal halides. We expect that the continuing progress in computational chemistry will shed further light on the intricate details of these and other molecular structures. PMID:19170522

  13. 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.

  14. Thermal emf of alkali metal--molten salt mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, K.E. (Univ. of Regina, Saskatchewan, Canada); Sime, S.J.

    1977-09-01

    The thermal emf of alkali metal--alkali halide mixtures is calculated on the basis of two models, the Pitzer model which suggests that the metal is completely dissociated to cation and electron, and the Rice model which assumes no dissociation. The Rice model gives surprisingly good agreement with the only available datum, that for Cs in CsAu. It is suggested that these systems will show a significant improvement in the figure of merit over simple molten salt mixtures. 3 tables.

  15. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Akdeniz, Z. (International Centre for Theoretical Physics, Trieste (Italy) Istanbul Univ. (Turkey). Dept. of Physics); Tosi, M.P. (Trieste Univ. (Italy). Dipt. di Fisica Teorica Argonne National Lab., IL (USA))

    1988-11-01

    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.

  17. Binary technetium halides

    Science.gov (United States)

    Johnstone, Erik Vaughan

    In this work, the synthetic and coordination chemistry as well as the physico-chemical properties of binary technetium (Tc) chlorides, bromides, and iodides were investigated. Resulting from these studies was the discovery of five new binary Tc halide phases: alpha/beta-TcCl3, alpha/beta-TcCl 2, and TcI3, and the reinvestigation of the chemistries of TcBr3 and TcX4 (X = Cl, Br). Prior to 2009, the chemistry of binary Tc halides was poorly studied and defined by only three compounds, i.e., TcF6, TcF5, and TcCl4. Today, ten phases are known (i.e., TcF6, TcF5, TcCl4, TcBr 4, TcBr3, TcI3, alpha/beta-TcCl3 and alpha/beta-TcCl2) making the binary halide system of Tc comparable to those of its neighboring elements. Technetium binary halides were synthesized using three methods: reactions of the elements in sealed tubes, reactions of flowing HX(g) (X = Cl, Br, and I) with Tc2(O2CCH3)4Cl2, and thermal decompositions of TcX4 (X = Cl, Br) and alpha-TcCl 3 in sealed tubes under vacuum. Binary Tc halides can be found in various dimensionalities such as molecular solids (TcF6), extended chains (TcF5, TcCl4, alpha/beta-TcCl2, TcBr 3, TcI3), infinite layers (beta-TcCl3), and bidimensional networks of clusters (alpha-TcCl3); eight structure-types with varying degrees of metal-metal interactions are now known. The coordination chemistry of Tc binary halides can resemble that of the adjacent elements: molybdenum and ruthenium (beta-TcCl3, TcBr3, TcI 3), rhenium (TcF5, alpha-TcCl3), platinum (TcCl 4, TcBr4), or can be unique (alpha-TcCl2 and beta-TcCl 2) in respect to other known transition metal binary halides. Technetium binary halides display a range of interesting physical properties that are manifested from their electronic and structural configurations. The thermochemistry of binary Tc halides is extensive. These compounds can selectively volatilize, decompose, disproportionate, or convert to other phases. Ultimately, binary Tc halides may find application in the nuclear fuel cycle and as precursors in inorganic and organometallic chemistry.

  18. Exciton-relaxation dynamics in lead halides

    OpenAIRE

    Iwanaga, Masanobu; Hayashi, Tetsusuke

    2002-01-01

    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 s...

  19. Self-Trapped Excitons in Ionic-Covalent Silver Halide Crystals and Nanostructures: High-Frequency EPR, ESE, ENDOR and ODMR Studies

    OpenAIRE

    P. G. Baranov; Romanov, N. G.; Poluektov, O. G.; Schmidt, J.

    2010-01-01

    Silver halides have unique features in solid state physics because their properties are considered to be of borderline nature between ionic and covalent bonding. In AgCl, the self-trapped hole (STH) is centered and partly trapped in the cationic sublattice, forming an Ag2+ ion inside of a (AgCl6)4? complex as a result of the Jahn–Teller distortion. The STH in AgCl can capture an electron from the conduction band forming the self-trapped exciton (STE). Recent results of a study of STE by means...

  20. Crystal-structural study of zirconium chelates with alkali metals of composition A2[Zr(Nta)2]·xH2O (A=Li, Na, K, Rb, Cs or CH3H6)

    International Nuclear Information System (INIS)

    Some zirconium complexes with nitrile triacetate and with alkali metal in the external sphere were studied crystalostructurally. Packing of complexes and extra-sphere cations was studied. Plane or slightly corrugated anion layers of two essentially different types arranged according to the principle of trigonal and square grids represent the standard element of crystal structure. Water molecules are located both in anion and cation layers. CN and coordination polyhedron of cations are different even in case of stereotype nature of reasons of their location in the interlayer space. In Cs-, Rb- and K- compounds polyhedrons of alkali metal form specific doubled chains. These compounds are not isomorphous ones and are characterized by a specific way of water molecule location. Structure of sodium compound differs fundamentally from other ones. Ionic conductivity may be expected in crystals. 4 refs., 6 figs., 2 tabs

  1. Properties of mixed alkali germanate glasses

    Science.gov (United States)

    Ashton-Patton, Melissann Marie

    There is little data in the literature pertaining to mixed alkali germanate glasses. The majority of the data exists for the sodium-potassium-germanate glasses, and focuses on the density, glass transition temperature and vibrational spectra. This study explores three of the ten possible mixed alkali germanate glass systems: the lithium-cesium-germanium ternary, the sodium-potassium-germanium ternary, and the potassium-rubidium-germanium ternary. The mixed alkali effect was examined at two different concentrations of germania (85 and 90 mol %). To examine the mixed alkali effect on the germanate anomaly, the alkali oxides were held in a ratio of 1:1 and the germanium was varied from 100 to 75 mol %. The glass transition temperature and densities behavior of the mixed alkali germanate glasses in this study behaved as expected, exhibiting a maximum in Tg and no mixed alkali effect in density. The glasses with a 1:1 ratio of alkali exhibited properties between the end member glasses. The infrared spectra from this study show that the hydroxyl content increases as the amount of alkali in the glass increases. The cation identity does effect the band positions and intensities. The infrared bands between 1500 and 4000 cm-1 are shown to be a result of water. Electrical conductivity of mixed alkali germanate glasses exhibited unique behavior. Small additions of alkali (? 5 mol %) result in a positive or a linear deviation from additivity, in both the lithium-cesium-germanate system and the sodium-potassium-germanate system. With 10 mol % alkali oxide addition the deviation from additivity increases as the radius ratio of the cations increases. However, with 15 mol % alkali oxide addition, the greater the difference in the radius ratio of the cations, the smaller the deviation from additivity. A Kissinger study on the lithium-cesium-germanate glasses, yields activation energies consistent with crystallization studies in the literature for other mixed alkali germanate glasses. Glasses with a 1:1 ratio of cesium oxide to lithium oxide, or more cesium oxide than lithium oxide, crystallize into cesium germanium oxide crystals, however if there is more lithium the glasses crystallize into an unknown phase.

  2. Casting of halide and fluoride alloys for laser windows. Semiannual technical report No. 2

    Energy Technology Data Exchange (ETDEWEB)

    Newberg, R.T.; Pappis, J.

    1975-04-15

    The main objective of this program is to demonstrate the feasibility of fusion casting of alkali halides and alkaline earth fluorides for high power laser window applications. The main effort deals with the fabrication and property evaluation of the alkaline earth fluorides. During the second six months of this program high quality castings of both CaF/sub 2/ and SrF/sub 2/ were fabricated. Castings of CaF/sub 2/ were attempted in an inert atmosphere of purified argon (1 to 50 torr). Calorimetrically measured 5.25 ..mu..m bulk absorption coefficients for cast CaF/sub 2/ are being consistently attained near 0.00042/cm regardless of the starting material. In preliminary results the 5.25 ..mu..m bulk absorption coefficient of cast SrF/sub 2/ lies near 0.000067/cm for an ingot using single crystal chips as starting material and lies near 0.00017/cm for an ingot cast from purified 'reagent' grade powder. The preliminary results also show that SrF/sub 2/ is equivalent in strength to CaF/sub 2/ and that polycrystalline cast material is equivalent in strength to single crystal material.

  3. 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.

  4. Characteristics of the fast electron emission produced during the cleavage of crystals

    Indian Academy of Sciences (India)

    B P Chandra; N L Patel; S S Rahangdale; R P Patel; V K Patle

    2003-01-01

    The present paper reports the fast electron emission produced during the cleavage of alkali halide crystals and models the dynamics of the process. The mechano-emission arises as a result of the ionization of surface traps at the expense of the energy which is released in the annihilation of the defects which are formed during cleavage. The slow electrons which appear upon the ionization of surface traps are subsequently accelerated in the ?eld of negatively charged segment of the freshly cleaved surface. Considering the basic mechanism of fast electron emission, expressions are derived which are able to explain satisfactorily the temporal, thermal, charge, surface, coloration, water adsorption and other characteristics of the fast electron emission produced during the cleavage of crystals. The decay time of the charges on the newly created surfaces, and the velocity of cracks can be determined from the measurements of fast electron emission produced during the cleavage of crystals. It is shown that two types of diffusing centres are responsible for the charge relaxation and thereby for the emission of fast electrons produced during the cleavage of alkali halide crystals.

  5. Copper doped alkali halides for computed radiography and digital imaging

    OpenAIRE

    Chakrabarti, K; Bandyopadhyay, P. K.; Barkyoumb, J. H.

    1998-01-01

    We report here the results of our x-ray fluorescence, photostimulated luminescence, and time resolved laser spectroscopy studies in KCI:Cu. This material seems to possess some desirable properties for being used as an imaging plate in computed radiography.

  6. Dynamics of early stage defect production in irradiated alkali halides

    International Nuclear Information System (INIS)

    The growth of F, HD and V2m centres in X-irradiated KCl (0.01 mol% SrCl2) has been studied as a function of temperature in the range 140 K to 185 K. The results show a dynamic, temperature-dependent saturation concentration of HD centres, which decreases with increasing temperature of irradiation and partially recovers on re-irradiation at a lower temperature. The growth of F and V2m centres has a temperature dependence quite different from that obtained for irradiations performed at higher temperatures. The model of Comins and Carragher is in good agreement with the experimental results and accounts in detail for the complex, interrelated defect growth. Analysis of the rate equations of the model shows that in the limit of sufficiently high temperature the form of solution F(t)= sum i?i(1-e-?it) is obtained; this has been used in the past to provide empirical fits to F centre growth curves and demonstrates an overall unity in the approaches used. ((orig.))

  7. 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

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

    International Nuclear Information System (INIS)

    A complex rare-earth rich alumino-borosilicate 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 (R2+ = Sr2+, Ba2+) cations present in the complex glass composition. Moreover, neodymium or lanthanum are used here to simulate all the rare-earths and actinides occurring in waste solutions. In order to study the impact of the nature of R+ and R2+ cations on both glass structure and melt crystallization tendency during cooling, two glass series were prepared by replacing either Na+ or Ca2+ cations in the simplified glass by respectively (Li+, K+, Rb+, Cs+) or (Mg2+, Sr2+, Ba2+) cations. From these substitutions, it was established that alkali ions are preferentially involved in the charge compensation of (AlO4)- entities in the glass network comparatively to alkaline-earth ions. The glass compositions containing calcium give way to the crystallization of an apatite silicate phase bearing calcium and rare-earth ions. The melt crystallization tendency during cooling strongly varies with the nature of the alkaline-earth. (authors)

  9. Actinide halide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1991-02-07

    A compound of the formula MX{sub n}L{sub m} wherein M = Th, Pu, Np,or Am thorium, X = a halide atom, n = 3 or 4, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is 3 or 4 for monodentate ligands or is 2 for bidentate ligands, where n + m = 7 or 8 for monodentate ligands or 5 or 6 for bidentate ligands, a compound of the formula MX{sub n} wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  10. Efficiency of energy transfer from ?-irradiated ammonium halides in aqueous iodide and nitrate solutions

    International Nuclear Information System (INIS)

    It is well known that ammonium halide (NH4X) crystals, on ?-exposure, store energy in the form of primary and secondary radiolytic products. Such crystals on dissolution in aqueous iodide and nitrate solutions result in oxidation of iodide and reduction of nitrate, respectively. The yields of iodine and nitrite are determined by chemical methods under varying conditions of the amount, dose and particle size of the irradiated ammonium halide salts. The maximum values of the efficiency of energy transfer for oxidation and reduction processes for ammonium halide salts correspond to 40% and 10%, respectively. At low doses, an empirical relation proposed between the percent efficiency of energy transfer and the absorbed dose is valid. The concentrations of inherent oxidizing and reducing species initially present are 7.0*1018 and 1.0*1018 per mol of ammonium halide, respectively. (author) 21 refs.; 7 figs.; 2 tabs

  11. Nickel(II) complexes of N2S2 donor set ligand and halide/pseudohalides: Synthesis, crystal structure, DNA and bovine/human serum albumin interaction

    Indian Academy of Sciences (India)

    Animesh Patra; Biplab Mondal; Buddhadeb Sen; Ennio Zangrando; Pabitra Chattopadhyay

    2015-11-01

    A series of neutral hexacoordinated nickel(II) complexes of formula [NiII (L)X2] (where L = 3,4-bis(2-pyridylmethylthio)toluene with tetradentate N2S2 donor set and X = chloride (1), azide (2), cyanate (3) and isothiocyanate anion (4)) have been synthesized and isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods along with detailed structural characterization of 1,2 and 3 by single crystal X-ray diffraction analyses. The structural study showed that the nickel(II) ion has a distorted octahedral geometry being chelated by the tetradentate N2S2 ligand and bound to cis- located choride or pseudohalide anions. In dimethylformamide solution the complexes showed quasi-reversible NiII/NiIII redox couples in cyclic voltammograms with E1/2 values of +0.723, +0.749, +0.768 and +0.868 V for 1, 2, 3 and 4, respectively. The study of interaction of the complexes with calf thymus DNA, bovine serum albumin (BSA) and human serum albumin (HSA) using spectroscopic and physicochemical tools clearly indicates that the complexes interact with DNA via groove binding mode.

  12. Specificity of structure of zinc(2) halides with cyclic tetraaminne ligands. Crystal structures of ZnCyclamX2, X=Cl, Br, I

    International Nuclear Information System (INIS)

    Crystal structure of ZnCyclamX2, X=Cl, Br, I, Cyclam(C10H24N4)=1,4,8,11-tetraazacyclotetradecane, was defined. The complexes are monomer tetragonally-bipyramid structures with meso-planar conformation Cyclam. Metal atoms is statistically shifted from equatorial plane by 0.24 A in case X=Cl; 0.33 A - X=Br; and 0.40 A - X=I. Secondary (elongated) axial bonds are nonequilibrium: Zn-Cl 2.424(8) and 2.0905(8) A, Zn-Br 2.555(4) and 3.214(4) A; Zn-I 2.753(1) and 3.543(1) A. Judging by geometry of the complexes and 13C[1H]NMR data statistical shift of Zn is dynamic character. The assumption is made that intramolecular motion increases stability of the complexes and characterizes specific type of binding, inherent of d10-metal complexes. It is shown that antibate correlation in the lengths of equatorial and axial bonds ascertained for slightly distorted octahedral complexes is just both for pyramid and bipyramid complexes with axial long-range action

  13. 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.

  14. Actinide halide complexes

    Science.gov (United States)

    Avens, Larry R. (Los Alamos, NM); Zwick, Bill D. (Santa Fe, NM); Sattelberger, Alfred P. (Los Alamos, NM); Clark, David L. (Los Alamos, NM); Watkin, John G. (Los Alamos, NM)

    1992-01-01

    A compound of the formula MX.sub.n L.sub.m wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands, a compound of the formula MX.sub.n wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  15. Liquid + liquid equilibrium in mixtures of lithium fluoride with potassium and rubidium halides

    International Nuclear Information System (INIS)

    Highlights: ? We measured electrical conductivity of the dissolving melts of LiF with KBr, KI, RbBr, and RbI along the saturation line. ? We studied a transient layer between the coexisting phases. ? The difference between the conductivities of phases increases as the radius of ion grows. ? An essential reorganisation of the light phase was found near the critical solution point. - Abstract: The liquid + liquid phase equilibrium of molten mixtures of lithium fluoride with potassium and rubidium halides was investigated over an extended temperature range in the two-phase region along the saturation line by the electrical conductivity method. In the overwhelming majority of mixtures, the electrical conductivity for coexisting equilibrium phases increased when the temperature increased. For mixtures with only potassium bromide, it decreased because of the extensive solubility of potassium bromide in lithium fluoride. The electrical conductivity for the light phase was half the value of the conductivity of the pure lithium fluoride. The electrical conductivity of the heavy phase did not differ enough from the conductivity of the pure heavy alkali halides. At the same time, the solubility of the heavy component in LiF was many times less than the lithium fluoride solubility in the lower phase. This contradiction points to essential reorganisation of the structure of the light phase. The difference between the conductivities of the coexisting phases at equal temperatures increased as the radius of the halide anion or alkali cation grew. The temperature growth led to the increase in the conductivity difference along the saturation line for mixtures of LiF with RbI. For mixtures of LiF with lighter alkali halides, it decreased up to zero at the critical mixing point for LiF + KBr mixtures as the temperature increased. Between the coexisting equilibrium phases, a transient layer was revealed, where a conductivity gradient exists. The thickness of this layer decreased as the temperature decreased and the sum of the ionic radii of the mixtures increased.

  16. Anharmonic properties of rubidium halides

    International Nuclear Information System (INIS)

    The anharmonic properties of rubidium halides are investigated using a three-body interaction (TBI) potential. This includes the prediction of second-, third- and fourth-order elastic constants, the pressure dependence of second- and third-order elastic constants. The agreement between experimental and theoretical results is, generally, good. The inclusion of anharmonic terms in the potential might lead to further improvements. (author)

  17. Solution-Phase Synthesis of Cesium Lead Halide Perovskite Nanowires.

    Science.gov (United States)

    Zhang, Dandan; Eaton, Samuel W; Yu, Yi; Dou, Letian; Yang, Peidong

    2015-07-29

    Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic-inorganic perovskites, the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites. PMID:26181343

  18. 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...

  19. 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.

  20. New ternary alkali oxides and quaternary alkali oxy-nitrides of molybdenum and tungsten

    OpenAIRE

    Arumugam, Nachiappan

    2005-01-01

    This work has focused on exploring the synthesis and characterization of new alkali oxides and oxynitrides of molybdenum and tungsten. In particular, the synthetic approach via the azide/nitrate route, which was developed recently, should be evaluated and extended to the oxides of the heavy group VI elements. For characterization, the crystal structures have been determined by using X-ray diffraction data by means of single crystal or powder methods, and TGA/DTA, DSC and specific heat me...

  1. The first alkali metal hydroxide-ammoniate, cesium hydroxide-ammoniate (1:1), CsOH·NH3, synthesis and crystal structure

    International Nuclear Information System (INIS)

    Cesium hydroxide-ammoniate (1:1), CsOH·NH3, was obtained as a side product in the reaction of cesium hydride, CsH and telluric acid, Te(OH)6 in liquid ammonia at ?38 °C. The compound crystallizes as colorless crystals in the monoclinic space group P21/c with Z = 8, a = 4.391(9) Å, b = 18.593(4) Å, c = 8.141 (16) Å, ? = 90.37(3)°, and V = 664.6(24) Å3. The crystal structure was solved from single crystal X-ray data. The structure contains a three-dimensional network built up by contacts between cesium cations and hydroxide anions and ammonia molecules, which in turn are connected by O–H···N and N–H···O hydrogen bonds. (author)

  2. Effect of alkali metal- and ammonium dichromates on solubility of boric acid

    International Nuclear Information System (INIS)

    Boric acid solubility in aqueous solutions of alkali metal and ammonium dichromates has been studied. It is established that the salts studied salt out boric acid. The value of lyotropic effect decreases in the series of NH4+, K+, Na+, Li+ cations. The sequence is the reciprocal to the one, observed in alkali metal chromates, and it is the same as in the case of halides and nitrates. It is conditioned by the character of cation hydration in acid medium. The negative sign of lyotropic effect is related to the absence of local interaction of boric acid with dimeric anions Cr2O72-, which is confirmed by the data of electron spectroscopy

  3. DEVELOPMENT AND EVALUATION OF METHODS FOR TOTAL ORGANIC HALIDE AND PURGEABLE ORGANIC HALIDE IN WASTEWATER

    Science.gov (United States)

    This report describes a series of studies involving the use of 'surrogate' methods for the determination of total organic halides (TOX), purgeable organic halides (POX), and solvent extractable organic halides (EOX), in wastewater and solid wastes. A pyrolysis/microcoulometric sy...

  4. Cs7Sm11[TeO3]12Cl16 and Rb7Nd11[TeO3]12Br16, the new tellurite halides of the tetragonal Rb6LiNd11[SeO3]12Cl16 structure type

    Science.gov (United States)

    Charkin, Dmitri O.; Black, Cameron; Downie, Lewis J.; Sklovsky, Dmitry E.; Berdonosov, Peter S.; Olenev, Andrei V.; Zhou, Wuzong; Lightfoot, Philip; Dolgikh, Valery A.

    2015-12-01

    Two new rare-earth - alkali - tellurium oxide halides were synthesized by a salt flux technique and characterized by single-crystal X-ray diffraction. The structures of the new compounds Cs7Sm11[TeO3]12Cl16 (I) and Rb7Nd11[TeO3]12Br16 (II) (both tetragonal, space group I4/mcm) correspond to the sequence of [MLn11(TeO3)12] and [M6X16] layers and bear very strong similarities to those of known selenite analogs. We discuss the trends in similarities and differences in compositions and structural details between the Se and Te compounds; more members of the family are predicted.

  5. Casting of halide and fluoride alloys for laser windows. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Newberg, R.T.; Pappis, J.

    1976-02-15

    The problem of residual strain in castings of alkali halides (KCl and SrCl/sub 2/-doped KCl) and alkaline earth fluorides (CaF/sub 2/ and SrF/sub 2/) has been overcome by the development of proper annealing and slow cooling procedures. Semiquantitative analysis of absorption coefficients and scattering centers (produced during improper casting and annealing procedures) has shown a correlation between the two for both the halides at 10 micrometers and fluorides at 5.25 micrometers. Consistently high quality castings of both CaF/sub 2/ and SrF/sub 2/ have been fabricated regardless of the starting materials. The dependence of fracture strength on both surface polish and annealing history is evidence that fracture for the fluorides is determined by surface and/or edge flaws. (GRA)

  6. Dehydrated rare earth halides and production process

    International Nuclear Information System (INIS)

    Rare earth chlorides, bromides or iodides containing less than 1 wt% water and less than 3 wt% oxyhalide are dehydrated by a gas flow of hydrogen halide through the halide bed. Structural water can interfer in some applications for instance metal preparation by chemical or electrochemical reduction

  7. New sulfido antimonates of the heavy alkali metals. Synthesis, crystal structure and chemical bonding of (K/Rb/Cs)3SbS3 and Cs3SbS4 . H2O

    International Nuclear Information System (INIS)

    The new sulfido antimonates(III) (Rb/Cs)3SbS3 were prepared from the alkali metal sulfides Rb2S/Cs2S2 and elemental antimony and sulfur or Sb2S3 at reaction temperatures of about 700 C. The known isotypic potassium compound was similarly synthesized from the elements. The structures of the light-yellow crystals were refined using single-crystal X-ray data. Both compounds are isotypic to the respective Na salt forming the Na3AsS3 structure type (cubic, space group P213, K/Rb/Cs: a = 947.21(7)/982.28(5)/1025.92(5) pm, Z = 4, R1 = 0.0159/0.0560/0.0582). The ?-tetrahedral SbS33- anions with Sb-S bond lengths of 242 pm are arranged in a cubic face centered packing, in which the three crystallographically different A+ cations occupy the tetrahedral and octahedral voids, overall exhibiting a distorted octahedral sulfur coordination. The chemical bonding and the characteristics of the stereochemically active lone electron pair have been investigated by means of FP-LAPW band structure calculations. Needle-shaped crystals of the monohydrate of the antimony(V) salt Cs3SbS4 . H2O were obtained from a suspension of Sb2O3, CsOH and elemental sulfur. Cs3SbS4 . H2O crystallizes in a new structure type (monoclinic, space group P21/c, a = 987.17(10), b = 994.83(7), c = 1600.46(14) pm, ? = 126.895(8) , Z = 4, R1 = 0.0234). As expected, the Sb-S distances (233.1-234.7 pm) in the nearly ideally tetrahedral anion SbS43- are considerably shorter than in the antimonates(III) but match the bond lengths in the anhydrous sulfido antimonate(V) Cs3SbS4. Due to their similar fcc-like anion packing and the stereochemically active lone electron pair of Sb in the antimonates(III), the whole series of compounds A3SbIII,VS3/4 shows a uniform structure relation, which is elucidated using crystallographic group-subgroup relations. (orig.)

  8. 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.

  9. 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.

  10. ALKALI RESISTANT CATALYST

    DEFF Research Database (Denmark)

    Fehrmann, Rasmus Technical University of Denmark,

    The present invention concerns the selective removal of nitrogen oxides (NOx) from gasses. In particular, the invention concerns a process, a catalyst and the use of a catalyst for the selective removal of nitrogen oxides in the presence of ammonia from gases containing a significant amount of alkali metal and/or alkali-earth compounds which process comprises using a catalyst combined of (i) a formed porous superacidic support, said superacidic support having an Hammett acidity stronger than Ho=-12, and (ii) a metal oxide catalytic component deposited on said superacidic support selected from the group consisting of oxides of Fe, Cu, V, Cr, Mn, and any mixtures thereof.

  11. Oscillatory rule in the energy spectrum of traps in KCl and NaI crystals

    CERN Document Server

    Gumenyuk, A F; Stanovyi, O P; Pashchenko, V G; Tomylko, S V

    2010-01-01

    The thermoluminescence (TL) method is used for the investigation of the energy spectrum of traps in KCl and NaI crystals in the temperature range 80-500 K. It is shown that the thermal activation energies of traps in KCl and NaI form one oscillatory series E=hwn with vibrational quantum energies of 0.121 eV in KCl and 0.061 eV in NaI. In this case, the quantum number n assumes half-integer and integer values. Based on the generalized data on the investigated alkali-halide crystals (AHC), we confirmed the earlier proposed model of TL in AHCs. It is assumed that, in addition to the nonradiative H-F recombination, there exists the two-stage recombination of H-centers at anion vacancies resulting in the radiative recombination of a hole at an F-center. The energy of a quantum in the oscillatory rule corresponds to a local vibrational mode of an X2 halide molecule.

  12. Chlor-Alkali Technology.

    Science.gov (United States)

    Venkatesh, S.; Tilak, B. V.

    1983-01-01

    Chlor-alkali technology is one of the largest electrochemical industries in the world, the main products being chlorine and caustic soda (sodium hydroxide) generated simultaneously by the electrolysis of sodium chloride. This technology is reviewed in terms of electrochemical principles and manufacturing processes involved. (Author/JN)

  13. 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.)

  14. Crystal structure, IMT and superconducting transitions in solids under high pressure

    International Nuclear Information System (INIS)

    Band structure methods have reached a high level of sophistication enabling us to calculate a wide variety of physical properties of solids. In this paper, the high pressure behaviour of Ni3(Al,Nb), LaFeO3, AgGaS2 and some of the alkali halide systems have been discussed. The crystal structural transformation in Ni3(Al,Nb) system and the magnetic as well as insulator-metal transition in La2FeO3 systems are studied by calculating their total energies as a function of volume. The question as to whether ionic solids will become superconductors under pressure is also discussed. The band structure calculations are made using the TBLMTO method. (author)

  15. Reactive scattering of electronically excited alkali atoms with molecules

    Energy Technology Data Exchange (ETDEWEB)

    Mestdagh, J.M.; Balko, B.A.; Covinsky, M.H.; Weiss, P.S.; Vernon, M.F.; Schmidt, H.; Lee, Y.T.

    1987-06-01

    Representative families of excited alkali atom reactions have been studied using a crossed beam apparatus. For those alkali-molecule systems in which reactions are also known for ground state alkali and involve an early electron transfer step, no large differences are observed in the reactivity as Na is excited. More interesting are the reactions with hydrogen halides (HCl): it was found that adding electronic energy into Na changes the reaction mechanism. Early electron transfer is responsible of Na(5S, 4D) reactions, but not of Na(3P) reactions. Moreover, the NaCl product scattering is dominated by the HCl/sup -/ repulsion in Na(5S, 4D) reactions, and by the NaCl-H repulsion in the case of Na(3P). The reaction of Na with O/sub 2/ is of particular interest since it was found to be state specific. Only Na(4D) reacts, and the reaction requires restrictive constraints on the impact parameter and the reactants' relative orientation. The reaction with NO/sub 2/ is even more complex since Na(4D) leads to the formation of NaO by two different pathways. It must be mentioned however, that the identification of NaO as product in these reactions has yet to be confirmed.

  16. ICES studies on sup(99m)Tc-halide complexes: formation, hydrolysis and ligand exchange

    Energy Technology Data Exchange (ETDEWEB)

    Fiser, M.; Brabec, V.; Dragoun, O.; Kovalik, A.; Rysavy, M.; Dragounova, N.

    1988-01-01

    The Internal Conversion Electron Spectroscopy (ICES) method was employed to study the products of reduction of no-carrier-added (sup(99m)Tc)pertechnetate by concentrated hydrochloric, hydrobromic and hydroiodic acids. The reductions were carried out in vacuum with subsequent evaporation of the solution to dryness. In the solid deposits, containing /similar to/ 10/sup -9/ g Tc, chemical shifts of sup(99m)Tc electron binding energies were measured and the results were compared with known data of x-ray photoelectron spectroscopy for defined technetium compounds. It was evidenced that all reduction/evaporation procedures yielded sup(99m)Tc(IV)-halide complexes. Another technique of reduction by vapours of halogen acids was proposed to prepare thin radioactive sources for physics studies. The reduction power of alkali halides in absence of acids was examined and a partial reduction of pertechnetate by iodide was found. The product was a hydrolysed species. The hydrolysis of halide complexes yielded the same product. In the absence of acids, dissolved species were partly oxidised to Tc(VII) by air. Oxidation was most apparent for the chloride and negligible for the iodide system. Ligand exchange of chloro and bromo complexes to chelate with DTPA at pH 3 was found to be uncomplete. Tc(IV) hydrolysed species, Tc(IV)DTPA and Tc(VII) were evidenced. Tc(V)DTPA was also observed which arises from partially oxidised products.

  17. ICES studies on 99mTc-halide complexes: formation, hydrolysis and ligand exchange

    International Nuclear Information System (INIS)

    The Internal Conversion Electron Spectroscopy (ICES) method was employed to study the products of reduction of no-carrier-added [99mTc]pertechnetate by concentrated hydrochloric, hydrobromic and hydroiodic acids. The reductions were carried out in vacuum with subbsequent evaporation of the solution to dryness. In the solid deposits, containing ? 10-9 g Tc, chemical shifts of 99mTc electron binding energies were measured and the results were compared with known data of x-ray photoelectron spectroscopy for defined technetium compounds. It was evidenced that all reduction/evaporation procedures yielded 99mTc(IV)-halide complexes. Another technique of reduction by vapours of halogen acids was proposed to prepare thin radioactive sources for physics studies. The reduction power of alkali halides in absence of acids was examined and a partial reduction of pertechnetate by iodide was found. The product was a hydrolysed species. The hydrolysis of halide complexes yielded the same product. In the absence of acids, dissolved species were partly oxidised to Tc(VII) by air. Oxidation was most apparent for the chloride and negligible for the iodide system. Ligand exchange of chloro and bromo complexes to chelate with DTPA at pH 3 was found to be uncomplete. Tc(IV) hydrolysed species, Tc(IV)DTPA and Tc(VII) were evidenced. Tc(V)DTPA was also observed which arises from partially oxidised products. (author)

  18. Double-Diffusive Convection During Growth of Halides and Selenides

    Science.gov (United States)

    Singh, N. B.; Su, Ching-Hua; Duval, Walter M. B.

    2015-01-01

    Heavy metal halides and selenides have unique properties which make them excellent materials for chemical, biological and radiological sensors. Recently it has been shown that selenohalides are even better materials than halides or selenides for gamma-ray detection. These materials also meet the strong needs of a wide band imaging technology to cover ultra-violet (UV), midwave infrared wavelength (MWIR) to very long wavelength infrared (VLWIR) region for hyperspectral imager components such as etalon filters and acousto-optic tunable filters (AO). In fact AOTF based imagers based on these materials have some superiority than imagers based on liquid crystals, FTIR, Fabry-Perot, grating, etalon, electro-optic modulation, piezoelectric and several other concepts. For example, broadband spectral and imagers have problems of processing large amount of information during real-time observation. Acousto-Optic Tunable Filter (AOTF) imagers are being developed to fill the need of reducing processing time of data, low cost operation and key to achieving the goal of covering long-wave infrared (LWIR). At the present time spectral imaging systems are based on the use of diffraction gratings are typically used in a pushbroom or whiskbroom mode. They are mostly used in systems and acquire large amounts of hyperspectral data that is processed off-line later. In contrast, acousto-optic tunable filter spectral imagers require very little image processing, providing new strategies for object recognition and tracking. They are ideally suited for tactical situations requiring immediate real-time image processing. But the performance of these imagers depends on the quality and homogeneity of acousto-optic materials. In addition for many systems requirements are so demanding that crystals up to sizes of 10 cm length are desired. We have studied several selenides and halide crystals for laser and AO imagers for MWIR and LWIR wavelength regions. We have grown and fabricated crystals of several materials such as mercurous chloride, mercurous bromide, mercurous iodide, lead chloride lead bromide, lead iodide, thallium arsenic selenide, gallium selenide, zince sulfide zinc selenide and several crystals into devices. We have used both Bridgman and physical vapor transport (PVT) crystal growth methods. In the past have examined PVT growth numerically for conditions where the boundary of the enclosure is subjected to a nonlinear thermal profile. Since past few months we have been working on binary and ternary materials such as selenoiodides, doped zinc sulfides and mercurous chloro bromide and mercurous bromoiodides. In the doped and ternary materials thermal and solutal convection play extremely important role during the growth. Very commonly striations and banding is observed. Our experiments have indicated that even in highly purified source materials, homogeneity in 1-g environment is very difficult. Some of our previous numerical studies have indicated that gravity level less than 10-4 (?-g) helps in controlling the thermosolutal convection. We will discuss the ground based growth results of HgClxBr(1-x) and ZnSe growth results for the mm thick to large cm size crystals. These results will be compared with our microgravity experiments performed with this class of materials. For both HgCl-HgBr and ZnS-ZnSe the lattice parameters of the mixtures obey Vagard's law in the studied composition range. The study demonstrates that properties are very anisotropic with crystal orientation, and performance achievement requires extremely careful fabrication to utilize highest figure of merit. In addition, some parameters such as crystal growth fabrication, processing time, resolution, field of view and efficiency will be described based on novel solid solution materials. It was predicted that very similar to the pure compounds solid solutions also have very large anisotropy, and very precise oriented and homogeneous bulk and thin film crystals is required to achieve maximum performance of laser or imagers. Some of the parameters controlling the homogeneity su

  19. Halide Ion Enhancement of Nitrate Ion Photolysis

    Science.gov (United States)

    Richards, N. K.; Wingen, L. M.; Callahan, K. M.; Tobias, D. J.; Finlayson-Pitts, B. J.

    2009-12-01

    Nitrate ion photochemistry is an important source of NOx in the polar regions. It is uncertain whether coexisting ions such as halides play a role in nitrate photochemistry. The effect of halides on NO3 photolysis was investigated using photolysis experiments in 230 L Teflon chambers that contain deliquesced aerosols of NaBr:NaNO3, KBr:KNO3 and ternary mixtures of NaCl:NaBr:NaNO3. Gas phase NO2 and gaseous halogen products were measured as a function of photolysis time using long path FTIR, NOx chemiluminescence and API-MS (atmospheric pressure ionization mass spectrometry). Experiments were conducted with NO3- held at a constant 0.5 M and with the amount of total halide concentration varying from 0.25 M to 4 M. Studies on NaBr:NaNO3 mixtures suggest that as the bromide ion to nitrate ion ratio increases, there is an enhancement in the rate of production of NO2 in the nitrate-bromide mixtures over that formed in the photolysis of NaNO3. Molecular dynamic (MD) simulations provide molecular level insight into the ions near the air-water interface in the aqueous halide-nitrate mixtures. These studies suggest that the presence of sodium halides at the air-water interface may encourage some nitrate ions to approach the top layers of water, allowing for more efficient escape of photoproducts than is seen in the absence of halides. Experiments on mixtures of KBr:KNO3 are being conducted to determine potential cation effects. In addition, ternary mixtures of NaCl:NaBr:NaNO3 are being examined to determine the effects of mixtures of halides on production of NO2 and gaseous halogen products. The implications of this photochemistry for tropospheric chemistry will be discussed.

  20. Halide based MBE of crystalline metals and oxides

    Energy Technology Data Exchange (ETDEWEB)

    Greenlee, Jordan D.; Calley, W. Laws; Henderson, Walter; Doolittle, W. Alan [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, Georgia (United States)

    2012-02-15

    A halide based growth chemistry has been demonstrated which can deliver a range of transition metals using low to moderate effusion cell temperatures (30-700 C) even for high melting point metals. Previously, growth with transition metal species required difficult to control electron beam or impurity inducing metal organic sources. Both crystalline oxide and metal films exhibiting excellent crystal quality are grown using this halide-based growth chemistry. Films are grown using a plasma assisted Molecular Beam Epitaxy (MBE) system with metal-chloride precursors. Crystalline niobium, cobalt, iron, and nickel were grown using this chemistry but the technology can be generalized to almost any metal for which a chloride precursor is available. Additionally, the oxides LiNbO{sub 3} and LiNbO{sub 2} were grown with films exhibiting X-ray diffraction (XRD) rocking curve full-widths at half maximum of 150 and 190 arcseconds respectively. LiNbO{sub 2} films demonstrate a memristive response due to the rapid movement of lithium in the layered crystal structure. The rapid movement of lithium ions in LiNbO{sub 2} memristors is characterized using impedance spectroscopy measurements. The impedance spectroscopy measurements suggest an ionic current of.1 mA for a small drive voltage of 5 mV AC or equivalently an ionic current density of {proportional_to}87 A/cm{sup 2}. This high ionic current density coupled with low charge transfer resistance of {proportional_to}16.5 {omega} and a high relaxation frequency (6.6 MHz) makes this single crystal material appealing for battery applications in addition to memristors. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites

    Science.gov (United States)

    Yakunin, Sergii; Protesescu, Loredana; Krieg, Franziska; Bodnarchuk, Maryna I.; Nedelcu, Georgian; Humer, Markus; de Luca, Gabriele; Fiebig, Manfred; Heiss, Wolfgang; Kovalenko, Maksym V.

    2015-08-01

    Metal halide semiconductors with perovskite crystal structures have recently emerged as highly promising optoelectronic materials. Despite the recent surge of reports on microcrystalline, thin-film and bulk single-crystalline metal halides, very little is known about the photophysics of metal halides in the form of uniform, size-tunable nanocrystals. Here we report low-threshold amplified spontaneous emission and lasing from ~10 nm monodisperse colloidal nanocrystals of caesium lead halide perovskites CsPbX3 (X=Cl, Br or I, or mixed Cl/Br and Br/I systems). We find that room-temperature optical amplification can be obtained in the entire visible spectral range (440-700 nm) with low pump thresholds down to 5+/-1 ?J cm-2 and high values of modal net gain of at least 450+/-30 cm-1. Two kinds of lasing modes are successfully observed: whispering-gallery-mode lasing using silica microspheres as high-finesse resonators, conformally coated with CsPbX3 nanocrystals and random lasing in films of CsPbX3 nanocrystals.

  2. Purification of alkali metal nitrates

    Science.gov (United States)

    Fiorucci, Louis C. (Hamden, CT); Gregory, Kevin M. (Woodridge, IL)

    1985-05-14

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

  3. Harmonic dynamical behaviour of thallous halides

    Indian Academy of Sciences (India)

    Sarvesh K. Tiwari; L. J. Shukla; K. S. Upadhyaya

    2010-05-01

    Harmonic dynamical behaviour of thallous halides (TlCl and TlBr) have been studied using the new van der Waals three-body force shell model (VTSM), which incorporates the effects of the van der Waals interaction along with long-range Coulomb interactions, three-body interactions and short-range second neighbour interactions in the framework of rigid shell model (RSM). Phonon dispersion curves (PDC), variations of Debye temperature with absolute temperature and phonon density of state (PDS) curves have been reported for thallous halides using VTSM. Comparison of experimental values with those of VTSM and TSM are also reported in the paper and a good agreement between experimental and VTSM values has been found, from which it may be inferred that the incorporation of van der Waals interactions is essential for the complete harmonic dynamical behaviour of thallous halides.

  4. Theory of Hydrogen Migration in Organic–Inorganic Halide Perovskites**

    Science.gov (United States)

    Egger, David A; Kronik, Leeor; Rappe, Andrew M

    2015-01-01

    Solar cells based on organic–inorganic halide perovskites have recently been proven to be remarkably efficient. However, they exhibit hysteresis in their current–voltage curves, and their stability in the presence of water is problematic. Both issues are possibly related to a diffusion of defects in the perovskite material. By using first-principles calculations based on density functional theory, we study the properties of an important defect in hybrid perovskites—interstitial hydrogen. We show that differently charged defects occupy different crystal sites, which may allow for ionization-enhanced defect migration following the Bourgoin–Corbett mechanism. Our analysis highlights the structural flexibility of organic–inorganic perovskites: successive iodide displacements, combined with hydrogen bonding, enable proton diffusion with low migration barriers. These findings indicate that hydrogen defects can be mobile and thus highly relevant for the performance of perovskite solar cells. PMID:26073061

  5. Theory of Hydrogen Migration in Organic-Inorganic Halide Perovskites.

    Science.gov (United States)

    Egger, David A; Kronik, Leeor; Rappe, Andrew M

    2015-10-12

    Solar cells based on organic-inorganic halide perovskites have recently been proven to be remarkably efficient. However, they exhibit hysteresis in their current-voltage curves, and their stability in the presence of water is problematic. Both issues are possibly related to a diffusion of defects in the perovskite material. By using first-principles calculations based on density functional theory, we study the properties of an important defect in hybrid perovskites-interstitial hydrogen. We show that differently charged defects occupy different crystal sites, which may allow for ionization-enhanced defect migration following the Bourgoin-Corbett mechanism. Our analysis highlights the structural flexibility of organic-inorganic perovskites: successive iodide displacements, combined with hydrogen bonding, enable proton diffusion with low migration barriers. These findings indicate that hydrogen defects can be mobile and thus highly relevant for the performance of perovskite solar cells. PMID:26073061

  6. Electric field effects on alanine tripeptide in sodium halide solutions.

    Science.gov (United States)

    Astrakas, Loukas G; Gousias, Christos; Tzaphlidou, Margaret

    2015-12-01

    The electric field effects on conformational properties of trialanine in different halide solutions were explored with long-scale molecular dynamics simulations. NaF, NaCl, NaBr and NaI solutions of low (0.2?M) and high (2?M) concentrations were exposed to a constant electric field of 1000?V/m. Generally, the electric field does not disturb trialanine's structure. Large structural changes appear only in the case of the supersaturated 2.0?M NaF solution containing NaF crystals. Although the electric field affects in a complex way, all the ions-water-peptide interactions, it predominantly affects the electroselectivity effect, which describes specific interactions such as the ion-pair formation. PMID:25006865

  7. New ternary transplutonium compounds: chalcogenide halides

    International Nuclear Information System (INIS)

    Although chalcogenide halides have been identified in almost all groups of the Periodic Table, they were previously unknown in the case of the actinide elements. Based on the known lanthanide chalcogenide halides, they focused their investigation on the sulfur-based compounds. Consistent with the scarcity of transplutonium elements, they developed an original microscale preparation of the ternary compounds AnSI (An = 242Pu, 243Am, 248Cm). The reaction scheme is: An2O3 (or AnO2) ? AnBr3 ?AnI3 ? AnSI. All products are examined by X-ray powder diffraction and solid state spectroscopy

  8. Synthesis, characterization and thermal properties of small R 2 R '2N+ X --type quaternary ammonium halides

    International Nuclear Information System (INIS)

    Twenty-one R 2 R '2N+ X - -type (R=methyl or ethyl, R '=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with 1H-NMR, 13C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. The thermal properties of all compounds were studied using TG/DTA and DSC methods. The smallest compounds decomposed during or before melting. The decreasing trend of melting points was observed when the alkyl chain length was increased. The liquid ranges of 120-180 deg. C were observed for compounds with 5-6 carbon atoms in the alkyl chain. The low melting points and wide liquid ranges suggest potential applicability of these compounds for example as ionic liquids precursors

  9. 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.)

  10. Reactivity of perfluoroalkyl halides towards nucleophiles

    International Nuclear Information System (INIS)

    The method of cyclic voltammetry was employed for the study and comparative evaluation of reactivity of perfluoroalkyl iodides and arylperfluoroalkyliodonium salts towards nucleophiles in various solvents. The method suggested can be used for predicting the reactivity of perfluoroalkyl halides in reactions proceeding according to the SRN1 mechanism. 16 refs., 3 figs., 4 tabs

  11. Unraveling halide hydration: A high dilution approach

    International Nuclear Information System (INIS)

    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 (?Ghyd?[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 ?Ghyd?[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

  12. Thermodynamic properties of pure and dilute alkali cyanides: short range order effects

    International Nuclear Information System (INIS)

    The alkali-cyanides NaCN and KCN, both pure and mixed in alkali-halides are studied, in the low temperature phases (paraelectric and antiferroelectric). Experimental results on the dielectric properties of these systems indicate that short-range order effects are important. These effects are investigated using the Kikuchi method in the limit of the pair correlation approximation (Bethe approximation). The results for the temperature dependence of the dielectric constant, for the pure systems, are adjusted to the experimental data available to obtain the three relevant parameters of the model: coordination number, coupling interaction and electric dipole moment of the CN- molecular ion. This parametrization is used in the study of the dielectric constants of the mixed systems and the critical temperature as a function of the CN- dipole concentration is obtained. The results are in good qualitative agreement with the experimental ones. (Author)

  13. Compounds of alkali metal anions

    Energy Technology Data Exchange (ETDEWEB)

    Dye, J.L.

    1979-01-01

    Anions of sodium, potassium, rubidium, and cesium are stable both in suitable solvents and in crystalline solids. The latter can be prepared either by cooling a saturated solution or by rapid solvent evaporation. Thermodynamic arguments show that alkali metal anions can probably exist in saturated solutions of the alkali metals in any compatible solvent, but that below saturation, dissociation into the cation and solvated electrons is favored in highly polar solvents such as ammonia. The key to solvent-free salts of the alkali metal anions is stabilization of the cation by incorporation into a suitable crown or cryptand complex. By using such complexes it also appears possible to produce electride salts in which the charge of the complexed cation is balanced by a trapped electron. The chemical, electrical, and optical properties of salts of the alkali metal anions and electrides could provide useful applications. 83 references.

  14. 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.

  15. Highly Luminescent Colloidal Nanoplates of Perovskite Cesium Lead Halide and Their Oriented Assemblies.

    Science.gov (United States)

    Bekenstein, Yehonadav; Koscher, Brent A; Eaton, Samuel W; Yang, Peidong; Alivisatos, A Paul

    2015-12-30

    Anisotropic colloidal quasi-two-dimensional nanoplates (NPLs) hold great promise as functional materials due to their combination of low dimensional optoelectronic properties and versatility through colloidal synthesis. Recently, lead-halide perovskites have emerged as important optoelectronic materials with excellent efficiencies in photovoltaic and light-emitting applications. Here we report the synthesis of quantum confined all inorganic cesium lead halide nanoplates in the perovskite crystal structure that are also highly luminescent (PLQY 84%). The controllable self-assembly of nanoplates either into stacked columnar phases or crystallographic-oriented thin-sheet structures is demonstrated. The broad accessible emission range, high native quantum yields, and ease of self-assembly make perovskite NPLs an ideal platform for fundamental optoelectronic studies and the investigation of future devices. PMID:26669631

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

    Directory of Open Access Journals (Sweden)

    G. Moroyoqui-Estrella

    2011-01-01

    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 con 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.

  17. Role of Farben centers in electron- and photon-stimulated desorption from alkali halides

    International Nuclear Information System (INIS)

    Measurements of the time history of ground-state neutral lithium desorption from LiF during pulsed electron irradiation have resulted in a new model for the lithium-desorption mechanism. We show that the slow diffusion to the surface of bulk Farben (F) centers created by the electron-beam is the rate-controlling factor responsible for most of the time history of the lithium desorption rather than the thermal evaporation of the metal from the surface. Comparison between theoretical and experimental time dependencies yields values for the F center diffusion constant and its activation energy

  18. Inelastic light scattering of the VK- and H-centre in alkali halides

    OpenAIRE

    Goovaerts, E.; De Schepper, L.; Schoemaker, D.

    1980-01-01

    The inelastic light scattering of the VK-centre was measured in LiF, KCl and RbCl. The spectra consist of a single peak at 437 cm-1 of the laser frequency in LiF, at 241 cm-1 in KCl and at 244 cm-1 in RbCl [1]. The raman active fundamental mode of the X-2 molecule (X- : halogen ion) induces the inelastic light scattering, as is seen by comparison with calculated data on the free X-2 molecules [2] as well as with measured frequencies of analogous systems. A tentative calculation of the frequen...

  19. 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.

  20. Factors affecting alkali jarosite precipitation

    Science.gov (United States)

    Dutrizac, J. E.

    1983-12-01

    Several factors affecting the precipitation of the alkali jarosites (sodium jarosite, potassium jarosite, rubidium jarosite, and ammonium jarosite) have been studied systematically using sodium jarosite as the model. The pH of the reacting solution exercises a major influence on the amount of jarosite formed, but has little effect on the composition of the washed product. Higher temperatures significantly increase the yield and slightly raise the alkali content of the jarosites. The yield and alkali content both increase greatly with the alkali concentration to about twice the stoichiometric requirement but, thereafter, remain nearly constant. At 97 °C, the amount of product increases with longer retention times to about 15 hours, but more prolonged reaction times are without significant effect on the amount or composition of the jarosite. Factors such as the presence of seed or ionic strength have little effect on the yield or jarosite composition. The amount of precipitate augments directly as the iron concentration of the solution increases, but the product composition is nearly independent of this variable. A significant degree of agitation is necessary to suspend the product and to prevent the jarosite from coating the apparatus with correspondingly small yields. Once the product is adequately suspended, however, further agitation is without significant effect. The partitioning of alkali ions during jarosite precipitation was ascertained for K:Na, Na:NH4, K:NH4, and K:Rb. Potassium jarosite is the most stable of the alkali jarosites and the stability falls systematically for lighter or heavier congeners; ammonium jarosite is slightly more stable than the sodium analogue. Complete solid solubility among the various alkali jarosite-type compounds was established.

  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. 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.

  2. Polarized XANES study of the importance of inter-block vis-a-vis intra-block coupling in evolution of Tc in halide-molecule-intercalated Bi2Sr2CaCu2O8-? single crystals

    International Nuclear Information System (INIS)

    In addition to doping in the lattice that affects the intra-block coupling, intercalated molecules sit in between the consecutive basal planes, thereby increasing the effective length of the c-axis. This, in turn, must lead to a decrease in inter-block coupling. Both the doping and intercalation have been reported to affect the evolution of Tc in a system, implying the inherent importance of both types of coupling. In the latter case, the resulting depression of Tc is ascribed to transfer of charge between the intercalate and the host CuO2 plane. Most interesting studies in this regard pertain to use of I2, HgI2 and HgBr2 molecules as intercalates for the Bi2Sr2CaCu2O8+y system. Earlier reports mostly claim that the host CuO2 plane in Bi2Sr2CaCu2O8+y invariably becomes overdoped whichever the intercalate, thereby leading to a fall in Tc. In this paper, we examine these claims in the case of Bi2Sr2CaCu2O8+y single crystals by measuring the number of itinerant holes before and after intercalation by making polarization-dependent soft-x-ray absorption measurements at the O K and the Cu L3 edges. Our results do support the earlier claims on overdoing of the CuO2 plane in the case of iodine intercalate but are not in agreement with those in the case of the HgI2 intercalate. (author)

  3. 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)

  4. Coordination Networks of Mercury(II) Halides and Polyether Ligand

    OpenAIRE

    Crochet, Aurélien; Fromm, Katharina M.

    2012-01-01

    New crystalline mercury halide adducts with polyetheras ligands were isolated, characterized, and identified as trans-[HgIICl?(diox)?]n (1) and trans-[HgIII?(diox)]n (2). The compounds were obtained from the metal halide salts in solution of 1,4-dioxane and can be considered as “cutting-out” products from the metal halide as they show similarity in the arrangement with starting compounds.

  5. Electrical conductivity of supercooled halide melts.

    Czech Academy of Sciences Publication Activity Database

    Sveshnikov, Alexey; Demo, Pavel; Kožíšek, Zden?k; Nitsch, Karel; Rodová, Miroslava

    Praha : MAXDORF s.r.o., 2002 - (Nitsch, K.; Rodová, M.), s. 51-52 ISBN 80-85912-85-8. [Joint Seminar "Development of Materials Science in Research and Education " /12./. Praha (CZ), 10.09.2002-12.09.2002] R&D Projects: GA AV ?R IAA1010010; GA ?R GA203/00/1423 Institutional research plan: CEZ:AV0Z1010914 Keywords : supercooled halide metals * electrical conductivity Subject RIV: BM - Solid Matter Physics ; Magnetism

  6. Probing the Catalytic Mechanism of Copper Amine Oxidase from Arthrobacter globiformis with Halide Ions.

    Science.gov (United States)

    Murakawa, Takeshi; Hamaguchi, Akio; Nakanishi, Shota; Kataoka, Misumi; Nakai, Tadashi; Kawano, Yoshiaki; Yamaguchi, Hiroshi; Hayashi, Hideyuki; Tanizawa, Katsuyuki; Okajima, Toshihide

    2015-09-18

    The catalytic reaction of copper amine oxidase proceeds through a ping-pong mechanism comprising two half-reactions. In the initial half-reaction, the substrate amine reduces the Tyr-derived cofactor, topa quinone (TPQ), to an aminoresorcinol form (TPQamr) that is in equilibrium with a semiquinone radical (TPQsq) via an intramolecular electron transfer to the active-site copper. We have analyzed this reductive half-reaction in crystals of the copper amine oxidase from Arthrobacter globiformis. Anerobic soaking of the crystals with an amine substrate shifted the equilibrium toward TPQsq in an "on-copper" conformation, in which the 4-OH group ligated axially to the copper center, which was probably reduced to Cu(I). When the crystals were soaked with substrate in the presence of halide ions, which act as uncompetitive and noncompetitive inhibitors with respect to the amine substrate and dioxygen, respectively, the equilibrium in the crystals shifted toward the "off-copper" conformation of TPQamr. The halide ion was bound to the axial position of the copper center, thereby preventing TPQamr from adopting the on-copper conformation. Furthermore, transient kinetic analyses in the presence of viscogen (glycerol) revealed that only the rate constant in the step of TPQamr/TPQsq interconversion is markedly affected by the viscogen, which probably perturbs the conformational change. These findings unequivocally demonstrate that TPQ undergoes large conformational changes during the reductive half-reaction. PMID:26269595

  7. 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.

  8. 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.

  9. Lanthanum halide scintillators for time-of-flight 3-D pet

    Science.gov (United States)

    Karp, Joel S. (Glenside, PA); Surti, Suleman (Philadelphia, PA)

    2008-06-03

    A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

  10. Growth and characterization of polycrystalline lanthanide halide scintillators

    International Nuclear Information System (INIS)

    We are exploring a novel time- and cost-efficient approach to produce robust, large-volume polycrystalline lanthanide halide scintillators using a hot wall evaporation (HWE) technique. To date, we have fabricated LaBr3:Ce and LaCl3:Ce films (slabs) measuring up to 7 cm in diameter and 7+ mm in thickness (20-25 cm3 in volume) on quartz substrates. These polycrystalline scintillators exhibit very bright emissions approaching those exhibited by their melt-grown crystal counterparts. Scanning electron micrographs (SEMs) and X-ray diffraction analysis confirm polycrystalline growth with columnar structures, both of which help in light piping, thereby contributing to the observed high light yields. The new scintillators also exhibit good energy resolution for ?-rays over the tested range of 60 keV (241Am) to 662 keV (137Cs), although they have not yet reached that of the corresponding crystals. The measured response linearity over the same energy range is comparable for both our HWE synthesized films and melt-grown commercially-available reference crystals. Similar consistency in response is also observed in terms of their decay time and afterglow behaviors. The data collected so far demonstrate that our HWE technique permits the rapid creation of scintillators with desired structural and compositional characteristics, without the introduction of appreciable defects, and yields material performance equivalent to or approaching that of crystals. Consequently, the deposition parameters may be manipulated to tailor the physical and scintillation performance of the resulting structures, while achieving a cost per unit volume that is substantially lower than that of crystals. In turn, this promises to allow the use of these novel scintillation materials in such applications as SPECT, PET, room-temperature radioisotope identification and homeland security, where large volumes of materials in a wide variety of shapes and sizes are needed. This paper describes our growth and testing of polycrystalline LaBr3:Ce scintillators and provides comparative characterizations of their performance with crystals.

  11. 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

  12. 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.

  13. Effect of alkali and heat treatments for bioactivity of TiO{sub 2} nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seo young, E-mail: mast6269@nate.com [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Kim, Yu kyoung, E-mail: yk0830@naver.com [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Park, Il song, E-mail: ilsong@jbnu.ac.kr [Division of Advanced Materials Engineering, Research Center for Advanced Materials Development and Institute of Biodegradable Materials, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Jin, Guang chun, E-mail: jingc88@126.com [Oral Medical College, Beihua University, Jilin City 132013 (China); Bae, Tae sung, E-mail: bts@jbnu.ac.kr [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Lee, Min ho, E-mail: mh@jbnu.ac.kr [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of)

    2014-12-01

    Highlights: • TiO{sub 2} nanotubes formed via anodization were treated by alkali and heat. • The surface roughness was increased after alkali treatment (p < 0.05). • After alkali and heat treatment, the wettability was better than before treatment. • Alkali treated TiO{sub 2} nanotubes were shown higher HAp formation in SBF. • Heat treatment affected on the attachment of cells for alkali treated nanotubes. - Abstract: In this study, for improving the bioactivity of titanium used as an implant material, alkali and heat treatments were carried out after formation of the nanotubes via anodization. Nanotubes with uniform length, diameter, and thickness were formed by anodization. The alkali and heat-treated TiO{sub 2} nanotubes were covered with the complex network structure, and the Na compound was generated on the surface of the specimens. In addition, after 5 and 10 days of immersion in the SBF, the crystallized OCP and HAp phase was significantly increased on the surface of the alkali-treated TiO{sub 2} nanotubes (PNA) and alkali and heat-treated TiO{sub 2} nanotubes (PNAH) groups. Cell proliferation was decreased due to the formation of amorphous sodium titanate (Na{sub 2}TiO{sub 3}) layer on the surface of the PNA group. However, anatase and crystalline sodium titanate were formed on the surface of the PNAH group after heat treatment at 550 °C, and cell proliferation was improved. Thus, PNA group had higher HAp forming ability in the simulated body fluid. Additional heat treatment affected on enhancement of the bioactivity and the attachment of osteoblasts for PNA group.

  14. Effect of alkali and heat treatments for bioactivity of TiO2 nanotubes

    International Nuclear Information System (INIS)

    Highlights: • TiO2 nanotubes formed via anodization were treated by alkali and heat. • The surface roughness was increased after alkali treatment (p < 0.05). • After alkali and heat treatment, the wettability was better than before treatment. • Alkali treated TiO2 nanotubes were shown higher HAp formation in SBF. • Heat treatment affected on the attachment of cells for alkali treated nanotubes. - Abstract: In this study, for improving the bioactivity of titanium used as an implant material, alkali and heat treatments were carried out after formation of the nanotubes via anodization. Nanotubes with uniform length, diameter, and thickness were formed by anodization. The alkali and heat-treated TiO2 nanotubes were covered with the complex network structure, and the Na compound was generated on the surface of the specimens. In addition, after 5 and 10 days of immersion in the SBF, the crystallized OCP and HAp phase was significantly increased on the surface of the alkali-treated TiO2 nanotubes (PNA) and alkali and heat-treated TiO2 nanotubes (PNAH) groups. Cell proliferation was decreased due to the formation of amorphous sodium titanate (Na2TiO3) layer on the surface of the PNA group. However, anatase and crystalline sodium titanate were formed on the surface of the PNAH group after heat treatment at 550 °C, and cell proliferation was improved. Thus, PNA group had higher HAp forming ability in the simulated body fluid. Additional heat treatment affected on enhancement of the bioactivity and the attachment of osteoblasts for PNA group

  15. Silver nanoparticles from silver halide photography to plasmonics

    CERN Document Server

    Tani, Tadaaki

    2015-01-01

    This book provides systematic knowledge and ideas on nanoparticles of Ag and related materials. While Ag and metal nanoparticles are essential for plasmonics, silver halide (AgX) photography relies to a great extent on nanoparticles of Ag and AgX which have the same crystal structure and have been studied extensively for many years. This book has been written to combine the knowledge of nanoparticles of Ag and related materials in plasmonics and AgX photography in order to provide new ideas for metal nanoparticles in plasmonics. Chapters 1–3 of this book describe the structure and formation of nanoparticles of Ag and related materials. Systematic descriptions of the structure and preparation of Ag, Au, and noble-metal nanoparticles for plasmonics are followed by and related to those of nanoparticles of Ag and AgX in AgX photography. Knowledge of the structure and preparation of Ag and AgX nanoparticles in photography covers nanoparticles with widely varying sizes, shapes, and structures, and formation proce...

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

    Energy Technology Data Exchange (ETDEWEB)

    Selling, J.

    2007-07-01

    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 BaCl{sub 2} 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 BaI{sub 2} 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 Eu{sup 2+}/Eu{sup 3+} ratio in the glass ceramics should be determined and optimize favor of the Eu{sup 2+}. We also want to distinguish between Eu{sup 2+} in the glass matrix and Eu{sup 2+} in the nanocrystals. For a better understanding of Moessbauer spectroscopy on Eu also measurements on Eu in a CaF{sub 2} host lattice were carried out. (orig.)

  17. 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

  18. New alkali metal diphosphates how materials to preserve the security of the environment: CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7) synthesis and crystal structure determination

    Science.gov (United States)

    Chernyatieva, Anastasiya; Filatova, Alyona; Spiridonova, Dariya; Krivovichev, Sergey

    2013-04-01

    In this work we describe preliminary results of the synthesis and of a crystal-chemical study of synthetic phosphates with transition metals. Due to the increasing requirements for environmental safety specialists from various industries, we are searching for sustainable forms of immobilization of hazardous waste during storage. We are also developing a component-based waste for new materials. In our continued exploratory synthesis of compounds containing transition-metals, we were able to produce the new diphosphate phases CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7). A crystal chemical study has allowed us to identify new phosphates. Crystals of CsNaCu(P2O7) (Phase 1) is orthorhombic, crystallizes in space group Pmn21, with a = 5.147(8), b = 15.126(2), c = 9.717(2) Å, V = 756.20 Å3, R1 = 0.066 and Rb2Cu(P2O7) (Phase 2) is orthorhombic as well, crystallizes in space group Pmcn, with a = 5.183(8), b = 10.096(1), c = 15.146(3) Å, V = 793.55 Å3, R1 = 0.063, they have been obtained by high-temperature reaction of RbNO3, CsNO3, Cu(NO3)2, NaOH and (NH4)4P2O7. Synthetic crystals of the phosphate of copper and rubidium were studied in detail by us on the structures of Rb2Cu(P2O7) and Rb2Cu3(P2O7)2 - new alkali metal copper diphosphates (CHERNYATIEVA et al., 2008). Here we report the synthesis, the structure and the properties of the title compounds and we compare these phases with the previously discovered K2CuP2O7 (ELMAADI et al., 1995) and CsNaMnP2O7 (HUANG et al., 1998). These structures crystallize in other space groups, although their structures are also based on 2-D layers, formed by P2O7 groups combined with polyhedra of the transition metals (CHERNYATIEVA et al., 2012). A crystal chemical study has allowed us to identify even new diphosphates CsNaCu(P2O7) (Phase 3). Crystals of CsNaCoP2O7 is monoclinic, space group P 21/n, with a = 7,424(2), b = 7,648(1), c = 12,931(3)Å, ? = 90,71(2)° , V = 734.2(3) Å3 and R1 = 0.060. The structure is based framework of Co tetrahedra and P2O7 groups. The structure of the [Co(P2O7)]2-framework in more detail. The phosphate groups and tetrahedra coordinate cobalt ions form topology. This is a unique 4-coordination topology, where Co and P2O7 groups in the structure are topologically equivalent. References CHERNYATIEVA, A. P., KRIVOVICHEV, S. V., SPIRIDONOVA, D. V. (2008): International conference «Inorganic Materials» Dresden (2008) P3 - 143. CHERNYATIEVA, A. P, SPIRIDONOVA, D. V., KRIVOVICHEV, S. V. The crystal structures of two new synthetic compounds CsNaCu(P2O7) and Rb2Cu(P2O7), Acta Mineralogica-Petrographica (2012) Vol.7, p.25 EL MAADI, A., BOUKHARI, A., HOLT, E.M. (1995) Journal of Alloys Compounds, 223: 13-17. HUANG, Q., HWU, S. J., MO, X. H. (2001): Angewandte Chemie - International Edition, 40: 1690-1693.

  19. 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)

  20. Topological insulator phase in halide perovskite structures

    Science.gov (United States)

    Jin, Hosub; Im, Jino; Freeman, Arthur J.

    2012-09-01

    Topological insulators are a novel quantum state of matter that reveals their properties and shows exotic phenomena when combined with other phases. Hence, priority has been given to making a good quality topological insulator interface with other compounds. From the applications point of view, the topological insulator phase in perovskite structures could be important to provide the various heterostructure interfaces with multifunctional properties. Here, by performing a tight-binding analysis and first-principles calculations, we predict that cubic-based CsPbI3 and CsSnI3 perovskite compounds under reasonable hydrostatic pressure are feasible candidates for three-dimensional topological insulators. Combined with cubic symmetry, the spin and total angular momentum doublets forming the valence and conduction bands result in a prototype of a continuum model, representing three-dimensional isotropic Dirac fermions, and govern the topological phase transition in halide perovskite materials.

  1. Role of microstructure in the electron-hole interaction of hybrid lead halide perovskites

    Science.gov (United States)

    Grancini, Giulia; Srimath Kandada, Ajay Ram; Frost, Jarvist M.; Barker, Alex J.; de Bastiani, Michele; Gandini, Marina; Marras, Sergio; Lanzani, Guglielmo; Walsh, Aron; Petrozza, Annamaria

    2015-10-01

    Organic-inorganic metal halide perovskites have demonstrated high power conversion efficiencies in solar cells and promising performance in a wide range of optoelectronic devices. The existence and stability of bound electron-hole pairs in these materials and their role in the operation of devices with different architectures remains a controversial issue. Here we demonstrate, through a combination of optical spectroscopy and multiscale modelling as a function of the degree of polycrystallinity and temperature, that the electron-hole interaction is sensitive to the microstructure of the material. The long-range order is disrupted by polycrystalline disorder and the variations in electrostatic potential found for smaller crystals suppress exciton formation, while larger crystals of the same composition demonstrate an unambiguous excitonic state. We conclude that fabrication procedures and morphology strongly influence perovskite behaviour, with both free carrier and excitonic regimes possible, with strong implications for optoelectronic devices.

  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. Paramagnetic SO3- radicals in alkali-borate and alkali-silicate glasses

    International Nuclear Information System (INIS)

    Alkali-silicate and alkali-borate glasses with sulphur include sulphite ion compounds, whose formation is promoted by alkali-metal oxides. Gamma irradiation effect gives rise to paramagnetic SO3- radicals, which are responsible for the EPR signal in the range of g=2.004

  4. Optimized spatial frequency response in silver halide sensitized gelatin

    OpenAIRE

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

    1991-01-01

    Silver halide sensitized gelatin processing is optimized to increase the spatial frequency response in Agfa-Gevaert 8E75 HD emulsion; therefore a diffraction efficiency of 55% in reflection gratings of 5000 lines/mm is achieved.

  5. Single-mode photonic crystal fiber for the middle infrared

    Science.gov (United States)

    Butvina, Leonid N.; Sereda, Olesya V.; Dianov, Eugeny M.; Lichkova, Ninel V.; Zagorodnev, Vladimir N.

    2007-04-01

    Photonic crystal optical fiber from silver halide crystals is described. Both experimental and theoretical evidences are presented to establish that the fiber is effectively singlemode at wavelength 10.6 ?m with numerical aperture NA = 0.16 and optical losses of 2 dB/m . Crystalline microstructured optical fibers offer key advantages over step-index optical fibers from silver halide crystals. The wide transmission range of wavelengths 2-20 ?m provides great potential for applications in spectroscopy and for the development of a range of new crystalline-based non-linear optical fibers.

  6. Transition metal-catalyzed nucleophilic substitution at thiophene-halides

    OpenAIRE

    Potratz, Stefanie

    2009-01-01

    Task of this thesis was nucleophilic substitution at thiophene-halides with O- and N-nucleophiles using copper and palladium catalysts. It was shown that phenols could be coupled under mild reactions conditions using modern copper catalysts. However, reaction conditions were not universal and conversion of diols was not possible. The poisoning of the catalyst due to stable copper-dialcoholate complexes was discussed. For amination of thiophene halides palladium catalysis was most effect...

  7. Characterization of Catalytically Active Octahedral Metal Halide Cluster Complexes

    OpenAIRE

    Satoshi Kamiguchi; Sayoko Nagashima; Teiji Chihara

    2014-01-01

    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 clu...

  8. 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...

  9. Investigation of doped cuprous halides for photovoltaic and display applications

    OpenAIRE

    Vijayaraghavan, Rajani

    2011-01-01

    The thesis mainly focuses on the growth and optoelectronic characterisation of the doped cuprous halides (CuX) with high UV/blue emission properties and the light harvesting in the CuBr/Si based heterojunction photovoltaic (PV) cells. Since cuprous halides are short wavelength emitters with high excitonic binding energies, growth of lower resistivity, highly luminescent p and n-type films are essential for the development of the future excitonic based light emitting devices with these materia...

  10. 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

  11. Halide and proton binding kinetics of yellow fluorescent protein variants.

    Science.gov (United States)

    Seward, Harriet E; Basran, Jaswir; Denton, Roanne; Pfuhl, Mark; Muskett, Frederick W; Bagshaw, Clive R

    2013-04-01

    A T203Y substitution in green fluorescent protein causes a red shift in emission to yield a class of mutants known as yellow fluorescent protein (YFP). Many of these YFP mutants bind halides with affinities in the millimolar range, which often results in the chromophore pK values being shifted into the physiological range. While such sensitivities may be exploited for halide and pH sensors, it is desirable to reduce such environmental sensitivities in other studies, such as in Förster resonance energy transfer probes to measure conformational changes within fusion proteins. Venus and Citrine are two such variants that have been developed with much reduced halide sensitivities. Here we compare the kinetics of halide binding, and the coupled protonation reaction, for several YFP variants and detect slow kinetics (dissociation rate constants in the range of 0.1-1 s(-1)), indicative of binding to an internal site, in all cases. The effective halide affinity for Venus and Citrine is much reduced compared with that of the original YFP 10C construct, primarily through a reduced association rate constant. Nuclear magnetic resonance studies of YFP 10C confirm halide binding occurs on a slow time scale (chemical shift occur throughout the sequence and structure. PMID:23514090

  12. 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.

  13. Alkali burns from wet cement.

    OpenAIRE

    Peters, W. J.

    1984-01-01

    When water is added to the dry materials of Portland cement calcium hydroxide is formed; the wet cement is caustic (with a pH as high as 12.9) and can produce third-degree alkali burns after 2 hours of contact. Unlike professional cement workers, amateurs are usually not aware of any danger and may stand or kneel in the cement for long periods. As illustrated in a case report, general physicians may recognize neither the seriousness of the injury in its early stages nor the significance of a ...

  14. 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.

  15. A complete series of uranocene(III) halides :braceUCp''2Xbracesub(n): :X=F, Cl, Br, or I; Cp'' = eta-C5H3(SiMe3)2]; Single-crystal x-ray structure determinations of the chloride and bromide (n=2 for X-=?-Cl- or ?-Br-)

    International Nuclear Information System (INIS)

    Reduction of [UCp''2X2] [Cp''=eta-C5H3(SiMe3)2; X=Cl, Br, or l: or :braceUCp''2(?-BF4)(?-F)brace2: with Na/Hg in toluene yields the lipophilic (and n.m.r. characterisable) compounds :braceUCp''2Xbracesub(n): (X=F, Cl, Br, or l), which are versatile precursors to uranocene (III or IV) compounds; X-ray data on the chloro- and bromo-derivatives reveal them to be the first uranocene(III) halide dimers (i.e., n=2, with ?-X-). (author)

  16. Method of handling radioactive alkali metal waste

    International Nuclear Information System (INIS)

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

  17. About alkali metal dicyanamides. Syntheses, single-crystal structure determination, DSC/TG and vibrational spectra of KCs[N(CN)2]2 and NaRb2[N(CN)2]3 . H2O

    International Nuclear Information System (INIS)

    Transparent colorless crystals of KCs[N(CN)2]2 and NaRb2[N(CN)2]3 . H2O were obtained by blending aqueous solutions of Na[N(CN)2] and RbF or KF, respectively. After evaporation of the water, the remaining solid was extracted with absolute ethanol and the solvent was allowed to evaporate at r. t. KCs[N(CN)2]2 crystallizes in the space group C2/c (no. 15) with the cell parameters a = 1382.7(2), b = 998.1(1) and c = 1455.4(2) pm, and ? = 118.085(4) . The structure of NaRb2[N(CN)2]3 . H2O is exhibiting the P63/m (no. 176) with the cell parameters a = 705.98(7) and c = 1462.89(12) pm. Single-crystalline ?-K[N(CN)2] was obtained while attempting to synthesize 'NaK2[N(CN)2]3', corroborating the results of previous X-ray powder diffraction experiments. Vibrational spectra and DSC/TGA analyses complete our results.

  18. 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

  19. The Renaissance of Halide Perovskites and Their Evolution as Emerging Semiconductors.

    Science.gov (United States)

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2015-10-20

    The recent re-emergence of the halide perovskites, of the type AMX3, derives from a sea-changing breakthrough in the field of photovoltaics that has led to a whole new generation of solar devices with remarkable power conversion efficiency. The success in the field of photovoltaics has led to intense, combined research efforts to better understand these materials both from the fundamental chemistry and physics points of view and for the improvement of applied functional device engineering. This groundswell of activity has breathed new life into this long-known but largely "forgotten" class of perovskites. The impressive achievements of halide perovskites in photovoltaics, as well as other optoelectronic applications, stem from an unusually favorable combination of optical and electronic properties, with the ability to be solution processed into films. This defines them as a brand new class of semiconductors that can rival or exceed the performance of the venerable classes of III-V and II-IV semiconductors, which presently dominate the industries of applied optoelectronics. Our aim in this Account is to highlight the basic pillars that define the chemistry of the halide perovskites and their unconventional electronic properties through the prism of structure-property relationships. We focus on the synthetic requirements under which a halide perovskite can exist and emphasize how the synthetic conditions can determine the structural integrity and the bulk properties of the perovskites. Then we proceed to discuss the origins of the optical and electronic phenomena, using the perovskite crystal structure as a guide. Some of the most remarkable features of the perovskites dealt with in this Account include the evolution of a unique type of defect, which gives rise to superlattices. These can enhance or diminish the fluorescence properties of the perovskites. For example, the exotic self-doping ability of the Sn-based perovskites allows them to adopt electrical properties from semiconducting to metallic. We attempt to rationalize how these properties can be tuned and partially controlled through targeted synthetic procedures for use in electronic and optical devices. In addition, we address open scientific questions that pose big obstacles in understanding the fundamentals of perovskites. We anticipate that the answers to these questions will provide the impetus upon which future research directions will be founded. PMID:26350149

  20. Unconventional Superconductivity in electron-doped layered metal nitride halides $M$N$X$ ($M$ = Ti, Zr, Hf; $X$ = Cl, Br, I)

    OpenAIRE

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

    2014-01-01

    In this review, we present a comprehensive overview of superconductivity in electron-doped metal nitride halides $M$N$X$ ($M$ = 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 th...

  1. 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.

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Science.gov (United States)

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

    2015-08-01

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

  4. Incorporation of alkali metals on Pt(111)

    Science.gov (United States)

    Lehmann, J.; Roos, P.; Bertel, E.

    1996-07-01

    The alkali-metal-doped platinum (111) surface is one of the most popular model systems for studies on catalytic promotion. Our results indicate that in the low-coverage range the alkali metals Na and K are incorporated into the surface. This is in contrast to the widely accepted adsorption geometry and calls for the reexamination of the current picture of alkali-metal-coadsorbate interactions on Pt(111). The driving mechanism for the incorporation is apparently different from that known on other metal surfaces and may be related to the large surface stress of Pt(111).

  5. High effective silica fume alkali activator

    Indian Academy of Sciences (India)

    Vladimír Živica

    2004-04-01

    Growing demands on the engineering properties of cement based materials and the urgency to decrease unsuitable ecologic impact of Portland cement manufacturing represent significant motivation for the development of new cement corresponding to these aspects. One category represents prospective alkali activated cements. A significant factor influencing their properties is alkali activator used. In this paper we present a new high effective alkali activator prepared from silica fume and its effectiveness. According to the results obtained this activator seems to be more effective than currently used activators like natrium hydroxide, natrium carbonate, and water glass.

  6. “On water” sp3–sp2 cross-couplings between benzylic and alkenyl halides

    OpenAIRE

    Krasovskaya, Valeria; Krasovskiy, Arkady; Bhattacharjya, Anish; Lipshutz, Bruce H.

    2011-01-01

    Organic-solvent-free cross-couplings between benzylic and alkenyl halides have been developed. Various alkenyl halides can be effciently benzylated by combining the precursor halides in the presence of Zn dust and a Pd catalyst at room temperature, in water as the only medium.

  7. Alkali metal for ultraviolet band-pass filter

    Science.gov (United States)

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

    1993-01-01

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

  8. 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.

  9. Phonon Dispersion Relations in Alkali Metals

    International Nuclear Information System (INIS)

    It has been shown in this paper that the phonon dispersion curves of sodium in the [100], [110] and [111] symmetry directions can be explained well on the basis of a simple model, where one has to consider only central force constants between nearest and next nearest neighbours. The tangential force constant between the nearest neighbours is very much smaller as compared to the radial force constant, while for the next nearest neighbours the radial and tangential force constants are comparable. The calculation is carried out on the basis of the model suggested by de Launay, where it is shown that the conduction electrons exert a volume force for longitudinal modes. The stiffness constant of the electron gas is its bulk modulus which in de Launay's model is equal to the Cauchy discrepancy (C12-C14) for the cubic crystals. The three force constants ?1, ?2 and ?1' can be determined from the measured elastic constants and the secular equation can be solved to give the dispersion curves. The dispersion curves have also been obtained using the calculated values of the bulk modulus of the electron gas after considering not only the exchange and correlation energies but also the Fermi kinetic energy. These also agree fairly well with experiment. The measured elastic constants as well as calculated bulk modulus of the electron gas indicate that the Cauchy relation C12 = C44 holds good approximately in alkali metals. This result is rather surprising as it requires that the interaction between the atoms be central in nature in spite of the metallic binding. A justification for this has been given by Cochran. A model with four force constants is being worked out. They can be determined from the three elastic constants and calculated bulk modulus of the electron gas. (author)

  10. Density of mixed alkali borate glasses: A structural analysis

    International Nuclear Information System (INIS)

    Density of mixed alkali borate glasses has been correlated with the glass structure. It is assumed that in such glasses each alkali oxide associates with a proportional quantity of B2O3. The number of BO3 and BO4 units related to each type of alkali oxide depends on the total concentration of alkali oxide. It is concluded that in mixed alkali borate glasses the volumes of structural units related to an alkali ion are the same as in the corresponding binary alkali borate glass. This reveals that each type of alkali oxide forms its own borate matrix and behaves as if not affected with the presence of the other alkali oxide. Similar conclusions are valid for borate glasses with three types of alkali oxide

  11. Density of mixed alkali borate glasses: A structural analysis

    Energy Technology Data Exchange (ETDEWEB)

    Doweidar, H. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt)]. E-mail: hdoweidar@mans.edu.eg; El-Damrawi, G.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt); Moustafa, Y.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt); Ramadan, R.M. [Glass Research Group, Physics Department, Faculty of Science, Mansoura University, P.O. Box 83, Mansoura 35516 (Egypt)

    2005-05-15

    Density of mixed alkali borate glasses has been correlated with the glass structure. It is assumed that in such glasses each alkali oxide associates with a proportional quantity of B{sub 2}O{sub 3}. The number of BO{sub 3} and BO{sub 4} units related to each type of alkali oxide depends on the total concentration of alkali oxide. It is concluded that in mixed alkali borate glasses the volumes of structural units related to an alkali ion are the same as in the corresponding binary alkali borate glass. This reveals that each type of alkali oxide forms its own borate matrix and behaves as if not affected with the presence of the other alkali oxide. Similar conclusions are valid for borate glasses with three types of alkali oxide.

  12. Synthesis, crystal structure, and properties of the rhombohedral modification of the thiospinel CuZr1.86(1)S4

    International Nuclear Information System (INIS)

    The rhombohedral modification of the thiospinel, CuZr1.86(1)S4, has been synthesized by the reaction of the constituent elements in an alkali metal halide flux and structurally characterized by single crystal X-ray diffraction techniques. The title compound crystallizes in the rhombohedral space group D3d5-R3-barm (no. 166, a=7.3552(2) A, c=35.832(2) A, V=1678.76(13) A3, Z=12, and R/wR=0.0239/0.0624). The structure is composed of close packed S layers, with a stacking order of ...ABCBCABABCACAB....along the c axis. The Zr and Cu atoms occupy the octahedral and tetrahedral holes between S layers, respectively. Three different kinds of S-M-S layers exist in the structure: layer I has fully occupied Zr and Cu sites, layer II has fully occupied Zr sites but no Cu, and layer III has partially occupied Zr and fully occupied Cu sites. Transport and optical properties indicate that the title compound is a small band gap (1.26 eV) n-type semiconductor. - Graphical abstract: The projected view of the rhombohedral modification, CuZr1.86(1)S4, down the [100] direction. Large letters denote the packing sequence of the S atoms (yellow circles) along the c axis. Zr (black circles) and Cu (red circles) atoms occupy the octahedral and tetrahedral holes, respectively, between close packed S layers.

  13. Raman study of the charge transfer C 60 complexes with tetraphenylphosphonium halides

    Science.gov (United States)

    Sauvajol, J. L.; Graja, A.; Firlej, L.; Król, S.

    1997-12-01

    Raman spectra are presented for single crystal charge-transfer complexes of fullerene and tetraphenylphosphonium halides, (Ph 4P) 2C 60Y (Y = Cl, Br, I). The Raman spectrum is found to be insensitive to the halogen ion indicating the intrinsic character of this spectrum. The spectra of complexes excited at 514.5 nm look very different from those excited at 647.1 nm; especially the low-frequency modes are stronger in the Raman spectrum excited at 647.1 nm. The 1469 cm -1 pentagonal pinch mode of C 60 is shifted and split in these complexes, a double-peak structure with components at 1462 and 1452 cm -1 is observed. All these results are understood as due to the presence of C -60 in crystalline sites of low symmetry.

  14. Excitons versus free charges in organo-lead tri-halide perovskites

    Science.gov (United States)

    D'Innocenzo, Valerio; Grancini, Giulia; Alcocer, Marcelo J. P.; Kandada, Ajay Ram Srimath; Stranks, Samuel D.; Lee, Michael M.; Lanzani, Guglielmo; Snaith, Henry J.; Petrozza, Annamaria

    2014-04-01

    Excitonic solar cells, within which bound electron-hole pairs have a central role in energy harvesting, have represented a hot field of research over the last two decades due to the compelling prospect of low-cost solar energy. However, in such cells, exciton dissociation and charge collection occur with significant losses in energy, essentially due to poor charge screening. Organic-inorganic perovskites show promise for overcoming such limitations. Here, we use optical spectroscopy to estimate the exciton binding energy in the mixed-halide crystal to be in the range of 50?meV. We show that such a value is consistent with almost full ionization of the exciton population under photovoltaic cell operating conditions. However, increasing the total photoexcitation density, excitonic species become dominant, widening the perspective of this material for a host of optoelectronic applications.

  15. Thallous and cesium halide materials for use in cryogenic applications

    International Nuclear Information System (INIS)

    Certain thallous and cesium halides, either used alone or in combination with other ceramic materials, are provided in cryogenic applications such as heat exchange material for the regenerator section of a closed-cycle cryogenic refrigeration section, as stabilizing coatings for superconducting wires, and as dielectric insulating materials. The thallous and cesium halides possess unusually large specific heats at low temperatures, have large thermal conductivities, are nonmagnetic, and are nonconductors of electricity. They can be formed into a variety of shapes such as spheres, bars, rods, or the like and can be coated or extruded onto substrates or wires. (author)

  16. Ultrafast time-resolved spectroscopy of lead halide perovskite films

    Science.gov (United States)

    Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

    2015-09-01

    Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

  17. 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...

  18. 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.)

  19. Magnetic studies on alkali metal uranates(V) MUO3 with the perovskite structure

    International Nuclear Information System (INIS)

    The magnetic properties of alkali metal uranates(V) MUO3 (M, alkali metal) with the perovskite structure have been studied. In this study RbUO3 (cubic perovskite structure) was prepared and its magnetic susceptibility was measured from 4.2 K to room temperature. It was found that a magnetic anomaly (magnetic transition) occurred at about 27 K. As a result of the U5+ ion in the paramagnetic state, the electron paramagnetic resonance spectrum was not observed even at 4.2 K. The magnetic susceptibility results and the optical absorption spectrum were analysed on the basis of an octahedral crystal field model. The magnetic transition temperatures and crystal field parameters determined for MUO3 (M triple bond Li, Na, K, Rb) are compared and discussed. (orig.)

  20. Dielectric measurements of adsorbed krypton on lamellar halides

    OpenAIRE

    Laheurte, J.P.; Noiray, J.C.; Obadia, M.; Romagnan, J.P.

    1981-01-01

    We present simultaneous measurements of adsorption isotherms and dielectric isotherms for krypton on lamellar halides. The comparison between the two isotherms shows that dielectric method is well adapted to characterize the multilayer formation. The evolution of dielectric properties from a two-dimensional system towards the bulk is also obtained.

  1. 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

  2. Photoluminescence of Au - formed in 12CaO · 7Al 2O 3 single crystal by Au +-implantation

    Science.gov (United States)

    Miyakawa, M.; Kamioka, H.; Hirano, M.; Kamiya, T.; Hosono, H.

    2006-09-01

    Au + ion implantation with fluences from 1 × 10 14 to 3 × 10 16 cm -2 into 12CaO · 7Al 2O 3 (C12A7) single crystals was carried out at a sample temperature of 600 °C. The implanted sample with the fluence of 1 × 10 15 cm -2 exhibited photoluminescence (PL) bands peaking at ˜3.1 and ˜2.3 eV at ?150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au - ion having the electronic configuration of 6 s2, judged from their similarities to those reported on Au - ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (˜2.3 × 10 21 cm -3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au + implantation if an appropriate fluence is chosen.

  3. Photoluminescence of Au- formed in 12CaO . 7Al2O3 single crystal by Au+-implantation

    International Nuclear Information System (INIS)

    Au+ ion implantation with fluences from 1 x 1014 to 3 x 1016 cm-2 into 12CaO . 7Al2O3 (C12A7) single crystals was carried out at a sample temperature of 600 deg. C. The implanted sample with the fluence of 1 x 1015 cm-2 exhibited photoluminescence (PL) bands peaking at ?3.1 and ?2.3 eV at ?150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au- ion having the electronic configuration of 6s 2, judged from their similarities to those reported on Au- ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (?2.3 x 1021 cm-3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au+ implantation if an appropriate fluence is chosen

  4. Silica enigma and ignorance in alkali

    International Nuclear Information System (INIS)

    Si migration and K, Na alterations are two key problems for understanding the whole process of hydrothermal metallogenesis, but they have not attracted sufficient attention of geologists for a long time. It is impossible for us to know hydrothermal metallogenetic regularity actually without studying dequartzfication and alkali-introduction. Being distinct from common habitual thinking, it is considered that ore-forming elements are micro-amount, passive subordinate components in the flow of hydrothermal matter movement, and there is no metallogenesis for a certain element in nature. Except that the ore source is controlled by the uneven distribution ore-forming elements in the mantle and crust the same metallogenesis may almost lead to the formation of deposits of all elements. Principal active components in the hydrothermal matter system include alkali, silica and acid volatiles. The ternary system has determined the fate of release, activation, migration, precipitaion and concentration of ore-forming elements. Each member of the ternary system plays a different role in metallogenesis, having marvellous functional division of work. of these three members main control factor is alkali metal, whereas silica and acid are constrained by alkali. Acidic matter (including silica) and ore-forming elements are derivatives from activities of alkali metals

  5. 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

  6. 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

  7. 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...

  8. N,N'-dimethylperylene-3,4,9,10-bis(dicarboximide) on alkali halide(001) surfaces

    OpenAIRE

    Fendrich, Markus; Lange, Manfred; WEISS, CHRISTIAN; Kunstmann, Tobias; Moeller, Rolf

    2008-01-01

    The growth of N,N'-dimethylperylene-3,4,9,10-bis(dicarboximide) (DiMe-PTCDI) on KBr(001) and NaCl(001) surfaces has been studied. Experimental results have been achieved using frequency modulation atomic force microscopy at room temperature under ultra-high vacuum conditions. On both substrates, DiMe-PTCDI forms molecular wires with a width of 10 nm, typically, and a length of up to 600 nm at low coverages. All wires grow along the [110] direction (or [1$\\bar{1}$0] direction...

  9. Second virial coefficients of alkali vapours

    International Nuclear Information System (INIS)

    Based on the ab initio calculations of Bertoncini et al, (J. Chem. Phys.; 52:5112 (1970)), on the triplet state of LiNa, the present authors proposed a Sato-type anti-Morse potential for the alkali dimers and used this in the calculation of Bsup((3))(T) [the triplet state contribution to the second virial coefficient] of alkali vapours. In this note the potential is compared with those of other workers in the calculation of Bsup((3))(T) and the second virial coefficients of all the alkali vapours are calculated over a wide range of temperature using the Morse and Rydberg potentials for the ground state and the anti-Morse potential for the triplet state of the dimers. (U.K.)

  10. Solvent-free MALDI investigation of the cationization of linear polyethers with alkali metals.

    Science.gov (United States)

    Hortal, Ana R; Hurtado, Paola; Martínez-Haya, Bruno; Arregui, Andrés; Bañares, Luis

    2008-07-24

    The MALDI technique with solvent-free sample preparation has been applied to evaluate relative gas-phase affinities of polyether chain polymers with alkali metal cations. The study is performed on poly(ethylene glycol) and poly(propylene glycol) polymers of different lengths (PEG600, PEG1000, PPG425, PPG750) and the alkali metal cations Li(+), Na(+), K(+), and Cs(+). The experiments show that the lattice energy of the alkali metal salts employed as cation precursors can have a strong influence on the outcome of conventional MALDI measurements. With the solvent-free method, these crystal binding effects can be made negligible by combining in the same sample alkali metal salts with different counterions. The recorded MALDI spectra show that the polyether-cation aggregation efficiencies decrease systematically with growing cation size. This cation size selectivity is considerably enhanced for the polymers with the shorter chains, which can be attributed to the reduced ability of the polymer to build a coordination shell around the larger cations. The steric effects introduced by the side CH3 group of propylene glycol with respect to ethylene glycol also enhance the preference for cationization of the polymer by the smaller cations. These observations correct some qualitative trends derived from previous studies, which did not account for lattice energy effects of the cation precursors. PMID:18582106

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

    Science.gov (United States)

    Investigations have focused primarily on surface structure and dynamics of ionic insulators, epitaxial growth onto alkali halide crystals and multiphoton studies. The surface dynamics of RbCl has been re-examined. We have developed a simple force constant model which provides insight into the dynamics of KBr overlayers on NaCl(001), a system with a large lattice mismatch. The KBr/NaCl(001) results are compared to Na/Cu(001) and NaCl/Ge(001). We have completed epitaxial growth experiments for KBr onto RbCl(001). Slab dynamics calculations using a shell model for this system with very small lattice mismatch are being carried out in collaboration with Professor Manson of Clemson University and with Professor Schroeder in Regensburg, Germany. Extensive experiments on multiphoton scattering of helium atoms onto NaCl and, particularly, LiF have been carried out and the theory has been developed to a rather advanced stage by Professor Manson. This work will permit the extraction of more information from time-of-flight spectra. It is shown that the theoretical model provides a very good description of the multiphoton scattering from organic films. Work has started on self-assembling organic films on gold (alkyl thiols/Au(111)). We have begun to prepare and characterize the gold crystal; one of the group members has spent two weeks at the Oak Ridge National Laboratory learning the proper Au(111) preparation techniques. One of our students has carried out neutron scattering experiments on NiO, measuring both bulk phonon and magnon dispersion curves.

  12. Carbonate, Halide, and Other New Mineral Inclusions in Diamond and Deep-Seated Carbonatitic Magma

    Science.gov (United States)

    Kaminsky, F.; Wirth, R.; Matsyuk, S.

    2009-05-01

    A series of uncommon micro- and nano-inclusions was identified in diamonds from the Juina area: carbonates, halides, and others. Carbonates are represented by calcite (with Sr and Ba), K-rich nyerereite (K2O = 10.0-13.78 wt. %), and nahcolite. Halides are NaCl, KCl, CaCl2 and PbCl2. Minerals of the periclase- wüstite series belong to two separate groups: wüstite and Mg-wüstite with Mg# = 1.9-15.3, and Fe-periclase and periclase with Mg# = 84.9-92.1. Wollastonite-II (high, Ca: Si = 0.992) has a triclinic structure. Ca-rich garnet has a noticeable admixture of Zr; it belongs to the andradite - kimzeyite - schorlomite group. Two types of spinel were distinguished among mineral inclusions in diamond: zoned magnesioferrite (with Mg# varying from 13.5 in a core to 90.8 in a rim) and Fe-spinel (magnetite). Olivine (Mg# = 93.6), intergrown with nyerereite, forms elongated, lath-shaped crystal and, probably, is a retrograde transformation of ringwoodite or wadsleyite. Some apatite grains are enriched in La, Ce and Nd. Among other minerals, there are anhydrite, cuspidine, phlogopite, TiO2 with an ?-PbO2 structure, native Fe. All inclusions are polymineralic solid inclusions. These minerals form a carbonatitic-type mineral association in diamond which may have been originated in lower mantle and/or transition zone. Wüstite inclusions with Mg# = 1.9-3.4, according to the experimental data, may have been formed in the lowermost mantle. The source for the observed carbonatitic-type mineral association in diamond is deep-seated carbonatitic, most likely natrocarbonatitic magma.

  13. 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.

  14. Matrix isolation infrared spectra of hydrogen halide and halogen complexes with nitrosyl halides

    Science.gov (United States)

    Allamandola, Louis J.; Lucas, Donald; Pimentel, George C.

    1982-01-01

    Matrix isolation infrared spectra of nitrosyl halide (XNO) complexes with HX and X2 (X = Cl, Br) are presented. The relative frequency shifts of the HX mode are modest (ClNO H-Cl, delta-nu/nu = -0.045; BrNO H-Br, delta-nu/nu = -0.026), indicating weak hydrogen bonds 1-3 kcal/mol. These shifts are accompanied by significant shifts to higher frequencies in the XN-O stretching mode (CIN-O HCl, delta-nu/nu = +0.016; BrN-O HBr, delta-nu/nu = +0.011). Similar shifts were observed for the XN-O X2 complexes (ClN-O Cl2, delta-nu/nu = +0.009; BrN-O-Br2, delta-nu/nu = +0.013). In all four complexes, the X-NO stretching mode relative shift is opposite in sign and about 1.6 times that of the NO stretching mode. These four complexes are considered to be similar in structure and charge distribution. The XN-O frequency shift suggests that complex formation is accompanied by charge withdrawal from the NO bond ranging from about .04 to .07 electron charges. The HX and X2 molecules act as electron acceptors, drawing electrons out of the antibonding orbital of NO and strengthening the XN-O bond. The implications of the pattern of vibrational shifts concerning the structure of the complexes are discussed.

  15. Alkali metal vapors - Laser spectroscopy and applications

    Science.gov (United States)

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

    1980-01-01

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

  16. Sample preparation and crystal growth for solid state actinide research

    International Nuclear Information System (INIS)

    The authors review the latest developments in the preparation of actinide samples for solid state physics investigations. Metallothermic reduction of the actinide halides, oxides and carbides in the preparation of actinide metals is discussed. Various methods of refining the metals are presented. Then the synthesis of actinide compounds is considered. Finally the various methods of crystal growth are reviewed. (Auth.)

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Silver halide sensitized gelatin as a holographic storage medium

    OpenAIRE

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

    1988-01-01

    Silver halide sensitized gelatin is one of the most promising techniques for the manufacturing of transmission holographic optical elements. These techniques combine the relatively high sensitivity of photographic material with the low scattering and high light-stability of dichromated gelatin. The influences of the developer and the bleaching in the diffraction efficiency and noise is analyzed starting with Agfa 8E75 HD plates.

  2. 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.

  3. Silver halide sensitized gelatin derived from BB-640 holographic emulsion

    OpenAIRE

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

    1998-01-01

    Silver halide sensitized gelatin (SHSG) is one of the most interesting techniques for the production of holographic optical elements, achieving relatively high sensitivity of photographic material with a low scattering of dichromated gelatin. Here we present experimental results for SHSG derived from the novel BB-640, a red-sensitive ultra-fine-grain emulsion from Holographic Recording Technologies (Steinau, Germany). The material is characterized before recording and after processing, and in...

  4. Study of methyl halide fluxes in temperate and tropical ecosystems

    OpenAIRE

    Blei, Emanuel

    2010-01-01

    CH3Br and CH3Cl (methyl halides) are the most abundant natural vectors of bromine and chlorine into the stratosphere and play an important role in stratospheric ozone destruction. The current knowledge of their respective natural sources is incomplete leading to large uncertainties in their global budgets. Beside the issue of quantification, characterisation of possible sources is needed to assist modelling of future environmental change impacts on these sources and hence the s...

  5. Organic-inorganic hybrid photovoltaics based on organometal halide perovskites

    OpenAIRE

    Lee, Michael M.; Henry J. Snaith

    2013-01-01

    This thesis details the development of a novel photovoltaic device based on organometal halide perovskites. The initial focus of this thesis begins with the study of lighttrapping strategies in solid-state dye-sensitised solar cells (detailed in chapter 3). While I report enhancement in device performance through the application of near and far-?eld light-trapping techniques, I ?nd that improvements remain step-wise due to fundamental limitations currently employed in dye-sensitised ...

  6. Improved spatial frequency response in silver halide sensitized gelatin holograms

    OpenAIRE

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

    1998-01-01

    We report what we believe to be the best results obtained to date with regard to the spatial frequency response of silver halide sensitized gelatin (SHSG) holograms. A very high diffraction efficiency, as high as 91% (after allowing for reflection), and an almost flat spatial frequency response between 800 lines/mm and 2800 lines/mm have been achieved using the new BB-640 plates manufactured by Holographic Recording Technologies. The results are compared with those for gratings recorded in th...

  7. Silver halide sensitized gelatin holograms using Slavich PFG-01 emulsion

    OpenAIRE

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

    1999-01-01

    Silver halide sensitized gelatin (SHSG) is an interesting technique for the production of holographic optical elements. It combines the high sensitivity of photographic emulsions with the well-known low scattering and high diffraction efficiency corresponding to dichromated gelatin. In this paper we present a comparative study of SHSG holograms recorded on both Slavich PFG-01 and Agfa 8E75 HD emulsions. We will show that real high diffraction efficiencies can be obtained (as high as 93% allo...

  8. Silver halide sensitized gelatin as a holographic recording material

    OpenAIRE

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

    1994-01-01

    Silver halide sensitized gelatin (SHSG) has proven to be a good alternative to dichromated gelatin and bleached emulsions in the production of volume phase holographic optical elements. In the present paper, the processing procedure for SHSG derived from Agfa-Gevaert holographic plates is reviewed and the holographic characteristics of the processed SHSG are experimentally measured and analysed. Several important aspects related to the influence of the developer and the bleach bath, the noise...

  9. Corrosion and compatibility in liquid alkali metals

    International Nuclear Information System (INIS)

    The literature dealing with liquid alkali metal corrosion of vanadium and its alloys is reviewed in the following subsections. Attention is given to both lithium and sodium data. Preceding this review, a brief outline of the current state of understanding of liquid metal corrosion mechanisms is provided

  10. Positronium impact ionization of Alkali atoms

    CERN Document Server

    Ghosh, D

    2015-01-01

    Target ionization processes of alkali atoms by Positronium impact are investigated. Calculations are performed in the frame work of model potential formalism using the Coulomb distorted eikonal approximation. Interesting qualitative features are noted both in the scattered Ps and the ejected electron distributions in differential as well as double differential levels of the collision cross sections.

  11. 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...

  12. 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.

  13. Photoluminescence of Au{sup -} formed in 12CaO . 7Al{sub 2}O{sub 3} single crystal by Au{sup +}-implantation

    Energy Technology Data Exchange (ETDEWEB)

    Miyakawa, M. [Frontier Collaborative Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)]. E-mail: m-miyakawa@lucid.msl.titech.ac.jp; Kamioka, H. [ERATO-SORST, Japan Science and Technology Agency, in Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hirano, M. [ERATO-SORST, Japan Science and Technology Agency, in Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Kamiya, T. [ERATO-SORST, Japan Science and Technology Agency, in Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hosono, H. [Frontier Collaborative Research Center, Tokyo Institute of Technology, Mail Box S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); ERATO-SORST, Japan Science and Technology Agency, in Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2006-09-15

    Au{sup +} ion implantation with fluences from 1 x 10{sup 14} to 3 x 10{sup 16} cm{sup -2} into 12CaO . 7Al{sub 2}O{sub 3} (C12A7) single crystals was carried out at a sample temperature of 600 deg. C. The implanted sample with the fluence of 1 x 10{sup 15} cm{sup -2} exhibited photoluminescence (PL) bands peaking at {approx}3.1 and {approx}2.3 eV at {<=}150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au{sup -} ion having the electronic configuration of 6s {sup 2}, judged from their similarities to those reported on Au{sup -} ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 ({approx}2.3 x 10{sup 21} cm{sup -3}), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au{sup +} implantation if an appropriate fluence is chosen.

  14. 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)

  15. 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.

  16. Superconductivity in room-temperature stable electride and high-pressure phases of alkali metals.

    Science.gov (United States)

    Hosono, Hideo; Kim, Sung-Wng; Matsuishi, Satoru; Tanaka, Shigeki; Miyake, Atsushi; Kagayama, Tomoko; Shimizu, Katsuya

    2015-03-13

    S-band metals such as alkali and alkaline earth metals do not undergo a superconducting transition (SCT) at ambient pressure, but their high-pressure phases do. By contrast, room-temperature stable electride [Ca24Al28O64](4+)?4e(-) (C12A7:e(-)) in which anionic electrons in the crystallographic sub-nanometer-size cages have high s-character exhibits SCT at 0.2-0.4?K at ambient pressure. In this paper, we report that crystal and electronic structures of C12A7:e(-) are close to those of the high-pressure superconducting phase of alkali and alkaline earth metals and the SCT of both materials is induced when electron nature at Fermi energy (EF) switches from s- to sd-hybridized state. PMID:25666076

  17. 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...

  18. Mesoscopic photosystems for solar light harvesting and conversion: facile and reversible transformation of metal-halide perovskites.

    Science.gov (United States)

    Harms, Hauke Arne; Tétreault, Nicolas; Pellet, Norman; Bensimon, Michaël; Grätzel, Michael

    2014-01-01

    Recently, hybrid organic-inorganic metal halide perovskites have gained prominence as potent light harvesters in thin film solid-state photovoltaics. In particular the solar-to-electric power conversion efficiency (PCE) of devices using CH(3)NH(3)PbI(3) as sensitizer has increased from 3 to 20.1% within only a few years. This key material can be prepared by solution processing from PbI(2) and CH(3)NH(3)I in one step or by sequential deposition. In the latter case an electron capturing support such as TiO(2) is first covered with PbI(2), which upon exposure to a CH(3)NH(3)I solution is converted to the perovskite. Here we apply for the first time quartz crystal microbalance (QCMD) measurements in conjunction with X-ray diffraction and scanning electron microscopy to analyse the dynamics of the conversion of PbI(2) to CH(3)NH(3)PbI(3). Employing 200 nm thick PbI(2) films as substrates we discover that the CH(3)NH(3)I insertion in the PbI(2) is reversible, with the extraction into the solvent isopropanol occurring on the same time scale of seconds as the intercalation process. This offers an explanation for the strikingly rapid and facile exchange of halide ions in CH(3)NH(3)PbX(3) by solution processing at room temperature. PMID:25643832

  19. 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...

  20. 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

  1. Effect of alkali lignins with different molecular weights from alkali pretreated rice straw hydrolyzate on enzymatic hydrolysis.

    Science.gov (United States)

    Li, Yun; Qi, Benkun; Luo, Jianquan; Wan, Yinhua

    2016-01-01

    This study investigated the effect of alkali lignins with different molecular weights on enzymatic hydrolysis of lignocellulose. Different alkali lignins fractions, which were obtained from cascade ultrafiltration, were added into the dilute acid pretreated (DAP) and alkali pretreated (AP) rice straws respectively during enzymatic hydrolysis. The results showed that the addition of alkali lignins enhanced the hydrolysis and the enhancement for hydrolysis increased with increasing molecular weights of alkali lignins, with maximum enhancement being 28.69% for DAP and 20.05% for AP, respectively. The enhancement was partly attributed to the improved cellulase activity, and filter paper activity increased by 18.03% when adding lignin with highest molecular weight. It was found that the enhancement of enzymatic hydrolysis was correlated with the adsorption affinity of cellulase on alkali lignins, and the difference in surface charge and hydrophobicity of alkali lignins were responsible for the difference in affinity between cellulase and lignins. PMID:26496216

  2. Developments in alkali-metal atomic magnetometry

    Science.gov (United States)

    Seltzer, Scott Jeffrey

    Alkali-metal magnetometers use the coherent precession of polarized atomic spins to detect and measure magnetic fields. Recent advances have enabled magnetometers to become competitive with SQUIDs as the most sensitive magnetic field detectors, and they now find use in a variety of areas ranging from medicine and NMR to explosives detection and fundamental physics research. In this thesis we discuss several developments in alkali-metal atomic magnetometry for both practical and fundamental applications. We present a new method of polarizing the alkali atoms by modulating the optical pumping rate at both the linear and quadratic Zeeman resonance frequencies. We demonstrate experimentally that this method enhances the sensitivity of a potassium magnetometer operating in the Earth's field by a factor of 4, and we calculate that it can reduce the orientation-dependent heading error to less than 0.1 nT. We discuss a radio-frequency magnetometer for detection of oscillating magnetic fields with sensitivity better than 0.2 fT/ Hz , which we apply to the observation of nuclear magnetic resonance (NMR) signals from polarized water, as well as nuclear quadrupole resonance (NQR) signals from ammonium nitrate. We demonstrate that a spin-exchange relaxation-free (SERF) magnetometer can measure all three vector components of the magnetic field in an unshielded environment with comparable sensitivity to other devices. We find that octadecyltrichlorosilane (OTS) acts as an anti-relaxation coating for alkali atoms at temperatures below 170°C, allowing them to collide with a glass surface up to 2,000 times before depolarizing, and we present the first demonstration of high-temperature magnetometry with a coated cell. We also describe a reusable alkali vapor cell intended for the study of interactions between alkali atoms and surface coatings. Finally, we explore the use of a cesium-xenon SERF comagnetometer for a proposed measurement of the permanent electric dipole moments (EDMs) of the electron and the 129Xe atom, with projected sensitivity of deltade=9x10 -30 e-cm and deltadXe=4x10 -31 e-cm after 100 days of integration; both bounds are more than two orders of magnitude better than the existing experimental limits on the EDMs of the electron and of any diamagnetic atom.

  3. Merwinite-structured phases as a potential host of alkalis in the upper mantle

    Science.gov (United States)

    Bindi, Luca; Safonov, Oleg G.; Zedgenizov, Dmitriy A.

    2015-08-01

    Two previously unknown Na- and K-rich phases were synthesized near the solidus of the model CMAS lherzolite interacted with the CaCO3 + Na2CO3 + KCl melt at 7 GPa. They coexist with forsterite, garnet and chloride-carbonate melt. Stoichiometry and unit-cell parameters measured by means of powder diffraction indicate that one of the phases corresponds to (K,Na)2Ca4Mg2Si4O15 (with about 0.1 a.p.f.u. Al). Although single-crystal X-ray measurements of this phase did not allow the solution of the crystal structure, we suggest that the structure of this phase includes mixed SiO4 and Si2O7 units. Single-crystal diffraction experiments of the other alkali-rich phase with composition (Ca2.06Na0.86K0.08)?=3.00(Mg0.53Si0.45Al0.03)?=1.01Si2.00O8 showed that it exhibits the merwinite structure, space group P21/ a, with lattice parameters a = 12.987(2), b = 5.101(1), c = 9.130(2) Å, ? = 92.36(1)°, V = 604.3(2) Å3, and Z = 4. The structure was refined to R 1 = 0.031 using 2619 independent reflections. In the structure, Na is hosted at the large Ca sites, whereas Si replaces Mg at the octahedral site and occurs in the usual tetrahedral coordination. Ordering-induced distortion provokes a change in coordination of the (Ca, Na) atoms with respect to pure merwinite. Merwinite phases with lower K + Na contents (0.08-0.18 a.p.f.u.) coexist with forsterite, clinopyroxene and immiscible carbonate-chloride and silicate melts at higher temperatures (up to 1510 °C) at 7 and 5.5 GPa. These phases (including alkali-rich ones at solidus) show a general formula [Ca3-2 x (Na,K)2 x ][Mg1- x Si x ]Si2O8 (with x up to 0.45), where the Na + K content negatively correlates with Ca and positively correlates with Si. The present experimental and crystal-chemical data prove that merwinite-structured phases may be efficient hosts for alkalis in the upper mantle. They are mineralogical indicators of either the interaction of mantle peridotites with alkaline carbonatitic liquids or high-pressure crystallization of silica-undersaturated CaO and alkali-rich melts.

  4. Radiation studies of aqueous alkali-metal hydroxide systems at low temperatures

    International Nuclear Information System (INIS)

    This investigation initially involves the study of electron trapping in gamma-irradiated alkali-metal hydroxide aqueous glasses. The study was conducted using electron spin resonance (esr) and optical spectroscopy techniques at about 77K. The hydroxides of lithium, sodium and potassium were looked at briefly as these have been covered in previous work. Rubidium and caesium hydroxides have been investigated in more detail, and results presented here clearly show that a second electron trapped centre exists for gamma-irradiated Rb aqueous glasses. Results for irradiated CsOH aqueous glasses are less conclusive, but certainly show divergence from the pattern established in lithium, sodium and potassium systems. Other systems studied are the aqueous hydroxide glasses of sodium, potassium, rubidium and caesium (by pulse-radiolysis) irradiated aqueous glasses containing halide salts (by esr and optical spectroscopy), irradiated aqueous hydroxide glasses of caesium or rubidium mixed with sodium or potassium (esr spectroscopy), gamma-irradiated glasses of mixed ammonia-water systems at 77K (esr and optical spectroscopy) and gamma irradiated KOH pellets at 77K (esr spectroscopy). (UK)

  5. Structural characterization of alkali metal 3-nitrobenzoates

    Science.gov (United States)

    ?wis?ocka, R.; Oleksi?ski, E.; Regulska, E.; Kalinowska, M.; Lewandowski, W.

    2007-05-01

    In this paper, the influence of lithium, sodium, potassium, rubidium and cesium on the electronic system of the 3-nitrobenzoic acid was studied. The vibrational (FT-IR, FT-Raman) and NMR ( 1H and 13C) spectra for 3-nitrobenzoic acid and its alkali metal salts were recorded. The changes of chemical shifts of protons ( 1H NMR) and carbons ( 13C NMR) in the series of studied alkali metal 3-nitrobenzoates were observed too. Optimized geometrical structures of studied compounds were calculated by B3PW91 method using 6-311++G ?? and 6-311++G basis sets. Geometric aromaticity indices, dipole moments and energies were also calculated. The theoretical wavenumbers and intensities of IR spectra were obtained at B3PW91/6-311++G level. The calculated parameters were compared to experimental characteristic of studied compounds.

  6. 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.

  7. Influence of alkali and alkaline earth ions on the -alkylation of the lower rim phenolic-OH groups of -tert-butyl-calix[4]arene to result in amide-pendants: Template action of K+ and the structure of K+ bound tetra-amide derivative crystallized with a -tert-butylcalix[4]arene anion

    Indian Academy of Sciences (India)

    Amjad Ali; Chebrolu P Rao; Philippe Guionneau

    2008-03-01

    Role of alkali and alkaline earth ions on the formation of calix[4]arene-amide derivatives through -alkylation of the lower rim phenolic-OH groups in general and template action of K+ in particular have been explored. Na+ and K+ ions among alkali, and Ca2+ and Sr2+ ions among alkaline earth have shown tetra-amide derivatives bound to metal ion species. Among all these, potassium salts act as template and yields a K+ bound tetra-amide derivative where the charge is counter balanced by a calix[4] arene-monoanion and the product is crystallographically characterized. Change in the amide precursor used in these -alkylation reactions has no effect on the type of the amide derivative formed. Also demonstrated is a direct one-step reaction for the preparation of 1,3-di-amide derivative in high yield and low reaction period using CsHCO3.

  8. Transport properties of alkali metal doped fullerides

    Science.gov (United States)

    Yadav, Daluram; Yadav, Nishchhal

    2015-07-01

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

  9. Modeling of Lead Halide Perovskites for Photovoltaic Applications

    OpenAIRE

    Jishi, Radi A.; Ta, Oliver B.; Sharif, Adel A.

    2014-01-01

    We report first-principles calculations, using the full potential linear augmented plane wave method, on six lead halide semiconductors, namely, CH3NH3PbI3, CH3NH3PbBr3, CsPbX3 (X=Cl, Br, I), and RbPbI3. Exchange is modeled using the modified Becke-Johnson potential. With an appropriate choice of the parameter that defines this potential, an excellent agreement is obtained between calculated and experimental band gaps of the six compounds. We comment on the possibility that ...

  10. Evaluation of field test equipment for halide and DOP testing

    International Nuclear Information System (INIS)

    The Nucon Testing Services Department, field testing at power reactor sites, has performed tests using R-11, R-12, and R-112 in conjunction with gas chromatographs and direct reading halide detectors. The field operational experience with these detector systems, thus sensitivity, precision, and manner of field calibration, are presented. Laboratory experiments regarding 3H-tagged methyl iodide for in place leak testing of adsorber systems indicate a low hazard, high reliability process for leak testing in facilities where atmospheric cross contamination occurs. (U.S.)

  11. Inelastic low-energy electron collisions with hydrogen halides

    Science.gov (United States)

    Horá?ek, J.

    2000-02-01

    Inelastic low-energy electron collisions with hydrogen halides HCl, HBr, DBr and HI are studied theoretically on the basis of the nonlocal resonance model of Domcke and Mündel. The model takes account of the dependence of the dipole-modified threshold exponent on the internuclear distance and of the precise form of the long-range part of the negative ion potential. Cross sections for vibrational excitation, dissociative attachment and associative detachment have been calculated. For all three collision processes, the cross sections calculated are in better agreement with experiment than previous calculations.

  12. The Oxidation State of Europium in Halide Glasses

    OpenAIRE

    Weber, J. K. R.; Vu, M.; Paßlick, C.; Schweizer, S.; Brown , D E; C. E. Johnson; Johnson, J. A.

    2011-01-01

    The luminescent properties of divalent europium ions can be exploited to produce storage phosphors for x-ray imaging applications. The relatively high cost and limited availability of divalent europium halides makes it desirable to synthesize them from the readily available trivalent salts. In this work, samples of pure EuCl3 and fluoride glass melts doped with EuCl3 were processed at 700-800 °C in an inert atmosphere furnace. The Eu oxidation state in the resulting materials was determined u...

  13. 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)

  14. 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

    2014-09-01

    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.

  15. Formation and evolution of point defects created in alkali halogen compounds irradiated by heavy ions

    International Nuclear Information System (INIS)

    The goal of this study was to achieve a better understanding of the heavy-ion material interaction. Alkali halogen crystals were chosen since the color centers produced by heavy ions can be distinguished easier from those generated by X rays. Measurements on KI irradiated at low temperature showed that the usual process of non radiative de-excitation of self-captured exciton is not prevailing. As the main objective of this work was the exact determination of the defects created by accelerated heavy ions, an important effort was dedicated to the spectrum deconvolution. Due to the high quality of the obtained spectra the V band analyse was possible. The defect stability was found to have the same nature in all the cubical alkali halogens and depend essentially on the crystal type. The defect evolution after irradiation is related to the diffusion coefficients corresponding to each mobile species and to the crystal lattice in which they move. Based on measurements made at different temperatures a simple modeling of the recombination kinetics was proposed. This effect was found to be specific to irradiation by heavy ions. It is difficult to determine the initial processes from the fossil defects, so, the defect history must be known as the described investigation methods do not permit to establish the transient aspect of defect creation. The important role of impurities should be stressed as the third intruder in the ion/crystal configuration; it can modify significantly the final state of the irradiated crystal, as it was found in KI, for instance. The open problems underlined in this study will probably be solved by using the atomic force microscopy and diffraction or on-line Raman measurements in ISOC chamber to avoid the passage to ambient conditions of the crystals irradiated at low temperatures

  16. (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 electrodes.

  17. Alkali depletion and ion-beam mixing in glasses

    International Nuclear Information System (INIS)

    Ion-implantation-induced alkali depletion in simple alkali-silicate glasses (12M2O.88SiO2) has been studied for implantations at room temperature and near 77K. Results are consistent with a mechanism for alkali removal, by heavy ion bombardment, based on radiation-enhanced migration and preferential removal of alkali from the outermost layers. Similar results were obtained for mixed-alkali glasses ((12-x)Cs2.O.xM2O.88SiO2) where, in addition, a mixed-alkali effect may also be operative. Some preliminary experiments with ion implantation through thin Al films on SiO2 glass and on a phosphate glass show that inter-diffusion takes place and suggest that this ion-mixing technique may be a useful method for altering the physical properties of glass surfaces

  18. 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.

  19. 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...

  20. Superconductivity in Room Temperature Stable electride and high-pressure phases of alkali metals

    OpenAIRE

    hosono, Hideo; Kim, Sung-Wng; Matsuishi, Satoru; Tanaka, Shigeki; Miyake, Atsushi; Kagayama, Tomoko; Shimizud, Katsuya

    2015-01-01

    S-band metals such as alkali and alkaline earth metals do not undergo a superconducting transition (SCT) at an ambient pressure, but their high-pressure phases do. In contrast, room temperature stable electride electride (C12A7:e-) in which anionic electrons in the crystallographic sub-nanometer-size cages have high s-character exhibits SCT at 0.2-0.4K at an ambient pressure. In this paper we report that crystal and electronic structure of C12A7:e- are close to those of the ...

  1. 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...

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

    OpenAIRE

    DARKO KRIZAN; MIROSLAV KOMLJENOVIC; BRANISLAV ZIVANOVIC

    2005-01-01

    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 ...

  3. Alternative alkali resistant deNOx catalysts

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Kristensen, Steffen Buus; Due-Hansen, Johannes; Riisager, Anders; Fehrmann, Rasmus

    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...

  4. Cathode architectures for alkali metal / oxygen batteries

    Science.gov (United States)

    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.

  5. Alkali?silica reaction (ASR) – Performancetesting

    OpenAIRE

    Lindgård, Jan

    2013-01-01

    Whether or not concrete prism tests developed for assessment of alkali?silica reactivity of aggregates is suitable for general ASR performance testing of concrete has been evaluated. The work has been part of the Norwegian COIN program (2007?2014), and has been performed in co?operation with the "performance testing" task group of RILEM TC 219?ACS. Thus, the RILEM aggregate concrete prism tests (CPTs) form the basis for the laboratory program. As a foundation for the experimental work, an int...

  6. Electrodes For Alkali-Metal Thermoelectric Converters

    Science.gov (United States)

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

    1989-01-01

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

  7. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts.

    Science.gov (United States)

    Falivene, Laura; Poater, Albert; Cazin, Catherine S J; Slugovc, Christian; Cavallo, Luigi

    2013-05-28

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol(-1). This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event. PMID:23235534

  8. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts

    OpenAIRE

    Falivene, Laura; Poater Teixidor, Albert; Cazin, Catherine S. J.; Slugovc, Christian; Cavallo, Luigi

    2013-01-01

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol(-1). This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event

  9. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts

    KAUST Repository

    Falivene, Laura

    2013-01-01

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol-1. This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event. © 2013 The Royal Society of Chemistry.

  10. Photophysical behavior and fluorescence quenching by halides of quinidine dication: Steady state and time resolved study

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Neeraj Kumar; Tewari, Neeraj; Arora, Priyanka; Rautela, Ranjana; Pant, Sanjay [Photophysics Laboratory, Department of Physics, DSB Campus, Kumaun University, Nainital 263002, Uttarakhand (India); Joshi, Hem Chandra, E-mail: hem_sup@yahoo.co.uk [Institute for Plasma Research, Laser Diagnostics Division, Bhat, Near Indira Bridge, Gandhinagar 382428, Gujarat (India)

    2015-02-15

    The fluorescence quenching of quinidine in acidified aqueous solution by various halides (Cl{sup ?}, Br{sup ?} and I{sup ?}) was studied using steady state and time resolved fluorescence techniques. The quenching process was characterized by Stern–Volmer (S–V) plots. Possibility of conformers (one is not quenched by halide and the other is quenched) is invoked to explain the observed results. - Highlights: • Fluorescence quenching of quinidine in acidified aqueous solution by halides. • Various quenching parameters have been estimated. • Possibility of conformers is invoked to explain the observed results.

  11. Ion Partitioning at the liquid/vapor interface of a multi-component alkali halidesolution: A model for aqueous sea salt aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Ghosal, Sutapa; Brown, Matthew A.; Bluhm, Hendrik; Krisch, Maria J.; Salmeron, Miquel; Jungwirth, Pavel; Hemminger, John C.

    2008-12-22

    The chemistry of Br species associated with sea salt ice and aerosols has been implicated in the episodes of ozone depletion reported at Arctic sunrise. However, Br{sup -} is only a minor component in sea salt, which has a Br{sup -}/Cl{sup -} molar ratio of {approx}0.0015. Sea salt is a complex mixture of many different species, with NaCl as the primary component. In recent years experimental and theoretical studies have reported enhancement of the large, more polarizable halide ion at the liquid/vapor interface of corresponding aqueous alkali halide solutions. The proposed enhancement is likely to influence the availability of sea salt Br{sup -} for heterogeneous reactions such as those involved in the ozone depletion episodes. We report here ambient pressure x-ray photoelectron spectroscopy studies and molecular dynamics simulations showing direct evidence of Br{sup -} enhancement at the interface of an aqueous NaCl solution doped with bromide. The experiments were carried out on samples with Br{sup -}/Cl{sup -} ratios in the range 0.1% to 10%, the latter being also the ratio for which simulations were carried out. This is the first direct measurement of interfacial enhancement of Br{sup -} in a multi-component solution with particular relevance to sea salt chemistry.

  12. Induced Spin-Currents in Alkali-Films

    CERN Document Server

    Bergmann, G; Garrett, D; Bergmann, Gerd; Song, Funing; Garrett, Doug

    2004-01-01

    In sandwiches of FeK and FeCs the conduction electrons in the alkali metals have a large mean free path. The experiments suggest that the specular reflection for spin up and down electrons is different at the interface yielding a spin current in the alkali film. The spin current is detected by the anomalous Hall effect of Pb surface impurities.

  13. Purification of tetra-hydro-borates of alkali metals

    International Nuclear Information System (INIS)

    Tetra-hydro-borates of alkali metals received by industrial methods or in laboratory contain different admixtures depending on using method. For recrystallization of tetra-hydro-borate of lithium using diethyl ether. For receiving pure natrium tetra-hydro-borate from technical product use several methods: recrystallization from water, water-alkali solution, liquid ammonia, pyridine and ethanol

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

    Science.gov (United States)

    Soung, Wen Y. (Houston, TX)

    1984-01-01

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

  15. Dispersion coefficients for alkali-metal diatoms

    Energy Technology Data Exchange (ETDEWEB)

    Dalgarno, A.; Marinescu, M.; Sadeghpour, H.R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

    1993-05-01

    The knowledge of the long-range interaction between atoms and molecules is of fundamental importance for low-energy and low-temperature collisions. The electrostatic interaction between the charge distributions of two ground-state alkali-metal atoms can be expanded in powers of 1/R, the internuclear distance. The coefficients corresponding to the expansion powers of R{sup -6}, R{sup -8}, and R{sup -10} are calculated exactly using a numerical technique originally developed for determining resonance profile near an absorption line. These coefficients are evaluated by integrating the dynamic electric multipole polarizabilities at imaginary frequencies which are in turn obtained by solving two coupled inhomogeneous differential equations. Highly accurate one-electron model potentials are developed to represent the motion of the valence electron in the field of the closed alkali positive ion core. The numerical results for the constants C{sub 6}, C{sub 8}, and C{sub 10} for the homo- and hetero-nuclear alkai diatoms are compared with other calculations.

  16. Group separation method for radioactive alkali scrubber liquid wastes

    International Nuclear Information System (INIS)

    Radioactive alkali scrubber liquid wastes generated in a reprocessing facility are at first neutralized by nitric acid, and precipitates are removed from filtrates. The filtrates are processed by oxalic acid, hydrogen fluoride, iodic acid or ammonium, and rare earth elements are precipitated and removed as insoluble salts. Further, after increasing the valency of TRU elements in the filtrates by an electrolytic method, the TRU elements are adsorbed and solidified by cationic ion exchange resins, and removed from the filtrates. Further, alkali and alkaline earth metals contained in the filtrates processed by the cation exchange resins are evaporated to dryness and stabilized. In this way, platinum elements, rare earth elements, TRU element and alkali/alkaline earth metal elements dissolved in the radioactive alkali scrubber liquid wastes are separated into four groups. Since radioactive alkali liquid wastes are thus converted to solid wastes, entire amount of the radioactive wastes can be reduced. (T.M.)

  17. 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

  18. Silver Halide Sensitized Gelatin Derived from BB-640 Holographic Emulsion

    Science.gov (United States)

    Neipp, Cristian; Pascual, Inmaculada; Beléndez, Augusto

    1999-03-01

    Silver halide sensitized gelatin (SHSG) is one of the most interesting techniques for the production of holographic optical elements, achieving relatively high sensitivity of photographic material with a low scattering of dichromated gelatin. Here we present experimental results for SHSG derived from the novel BB-640, a red-sensitive ultra-fine-grain emulsion from Holographic Recording Technologies (Steinau, Germany). The material is characterized before recording and after processing, and information about the thickness, absorption, and refractive-index modulation of the final holograms is obtained. The influence of the developer is analyzed, and diffraction efficiencies as great as 96.2% (after allowing for reflections) with a transmission of 1% and absorption and scatter losses of 2.8% are obtained with AAC developer. Our investigations reveal that high-quality SHSG transmission holograms may be obtained with the new BB-640 plates.

  19. Two-photon pumped lead halide perovskite nanowire lasers

    CERN Document Server

    Gu, Zhiyuan; Sun, Wenzhao; Li, Jinakai; Liu, Shuai; Song, Qinghai; Xiao, Shumin

    2015-01-01

    Solution-processed lead halide perovskites have shown very bright future in both solar cells and microlasers. Very recently, the nonlinearity of perovskites started to attract considerable research attention. Second harmonic generation and two-photon absorption have been successfully demonstrated. However, the nonlinearity based perovskite devices such as micro- & nano- lasers are still absent. Here we demonstrate the two-photon pumped nanolasers from perovskite nanowires. The CH3NH3PbBr3 perovskite nanowires were synthesized with one-step solution self-assembly method and dispersed on glass substrate. Under the optical excitation at 800 nm, two-photon pumped lasing actions with periodic peaks have been successfully observed at around 546 nm. The obtained quality (Q) factors of two-photon pumped nanolasers are around 960, and the corresponding thresholds are about 674?J=cm2. Both the Q factors and thresholds are comparable to conventional whispering gallery modes in two-dimensional polygon microplates. Ou...

  20. Versatile, isotopically specific hydrogen halide TEA pin laser

    International Nuclear Information System (INIS)

    A practical, easily constructed design for a laboratory hydrogen/deuterium halide chemical TEA laser is presented. Typical output energies in excess of 50 mJ/pulse broadband and 5 mJ/pulse on single lines are easily obtained. Isotopically specific oscillation on the v=1?0 band of single isotopes of H35Cl--H37Cl, D35Cl--D37Cl, H79Br--H81Br, and D79Br--D81Br is demonstrated. The ease of conversion from one laser species to the next and the flexible design provide a highly versatile device for laboratory problems in chemical and physical dynamics. Major advances in the development of laboratory HCl and HBr chemical TEA lasers are also reviewed

  1. Interionic interactions in alcoholic solutions of hydrogen halides

    International Nuclear Information System (INIS)

    Based on experimental data of ionization constants the effective short-range potential dij for HCl, HBr and HI in n-alcohols (methanol-ethanol) has been calculated and analyzed at 5-55 Deg C. Established regularities in changing values dij (as well as values ?ijG*=NAdij) depend on temperature, solvent, anion have been explained on the basis of the conception of Samojlov about near solvation. Changes in values ?ijG* are demonstrated to be conditioned by the correlation of contributions from ion-molecular and intermolecular non-coulomb interactions that in turn to be determined by structural state of solvent and solvation of electrolyte particles in hydrogen halide solution

  2. Material Innovation in Advancing Organometal Halide Perovskite Functionality.

    Science.gov (United States)

    Zheng, Fan; Saldana-Greco, Diomedes; Liu, Shi; Rappe, Andrew M

    2015-12-01

    Organometal halide perovskites (OMHPs) have garnered much attention recently for their unprecedented rate of increasing power conversion efficiency (PCE), positioning them as a promising basis for the next-generation photovoltaic devices. However, the gap between the rapid increasing PCE and the incomplete understanding of the structure-property-performance relationship prevents the realization of the true potential of OMHPs. This Perspective aims to provide a concise overview of the current status of OMHP research, highlighting the unique properties of OMHPs that are critical for solar applications but still not adequately explained. Stability and performance challenges of OMHP solar cells are discussed, calling upon combined experimental and theoretical efforts to address these challenges for pioneering commercialization of OMHP solar cells. Various material innovation strategies for improving the performance and stability of OMHPs are surveyed, showing that the OMHP architecture can serve as a promising and robust platform for the design and optimization of materials with desired functionalities. PMID:26631361

  3. Mechanical properties of silver halide core/clad IR fibers

    Science.gov (United States)

    Shalem, Shaul; German, Alla; Moser, Frank; Katzir, Abraham

    1996-04-01

    We have developed core/clad polycrystalline silver halide optical fibers with a loss of roughly 0.3 dB/m at 10.6 micrometers. Such fibers, with core diameters 0.3 - 0.6 mm and lengths of 1 to 2 meters are capable of continuously delivering output power densities as high as 14 KW/cm2. The fibers were repetitively bent in the plastic and elastic regimes and the optical transmission monitored during bending. The mechanical properties of the core/clad fibers and of the core only fibers are similar. It was also demonstrated that the 'bending' properties of the core/clad fibers are determined by the cladding material. Our investigations suggest that proper design of the core/clad structure may give significant improvement in mechanical properties such as more cycles to optical failure. This will be very important especially for endoscopic laser surgery and other medical applications.

  4. Solidification of nitrate solutions with alkali-activated slag and slag–metakaolin cements

    International Nuclear Information System (INIS)

    Highlights: • The effectiveness of an AASC matrix for NaNO3 solution solidification is stated. • XRD, DTA-TG, and X-ray microtomography experiments were performed. • Crystallization of NaNO3 reduces the shrinkage of hardened AASC-based waste forms. • Metakaolin shortens the setting time and increases the compressive strength of AASC. - Abstract: The solidification of nitrate solutions with alkali-activated slag (AASC) and slag–metakaolin cements (AASMC) and the resulting setting times, compressive strengths, dimensional stability, water resistance, hydration products, microstructures, and macroporous network structures were evaluated. The influences of the alkali activator concentration, mineral composition of metakaolin, ratio of slag to slag + metakaolin, and concentration of NaNO3 on the cement performance were all evaluated in detail. The compressive strength of cemented nitrate solutions with AASC and AASMC aged for 28 days was from 13.4 to 42 MPa depending on the NaNO3 concentration. X-ray diffractometer, differential thermal analyzer, and electron microscope analyses suggested that NaNO3 crystallizes in cementitious matrices without reacting with the hydration products of AASC and AASMC. X-ray microtomography showed that the solidified NaNO3 solution with a salt concentration of 700 g/l and AASC had a denser microstructure without shrinkage microcracks, a smaller macropore volume, and smaller macropore sizes than hardened AASC-based paste mixed with water

  5. 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...

  6. Bright light-emitting diodes based on organometal halide perovskite

    Science.gov (United States)

    Tan, Zhi-Kuang; Moghaddam, Reza Saberi; Lai, May Ling; Docampo, Pablo; Higler, Ruben; Deschler, Felix; Price, Michael; Sadhanala, Aditya; Pazos, Luis M.; Credgington, Dan; Hanusch, Fabian; Bein, Thomas; Snaith, Henry J.; Friend, Richard H.

    2014-09-01

    Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15?nm layer of CH3NH3PbI3-xClx perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9?-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2?W?sr-1?m-2 at a current density of 363?mA?cm-2, with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364?cd?m-2 at a current density of 123?mA?cm-2, giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.

  7. Extraction of halide and thiocyanate complexes of cadmium by tributylphosphate from sulfuric acid solutions

    International Nuclear Information System (INIS)

    Extraction of the halide and thiocyanate complexes of cadmium from H2SO4-KX solutions, where X=Cl, Br, I, or SCN, by solutions of tributyl phosphate (TBP) in benzene has been examined as a function of the acidity of the medium, halide ion and TBP concentration, and also of the temperature. Optimal conditions have been established for extraction. Cadmium is extracted as CdX2.2TBP at low halide-ion concentrations (less than or equal to 0.1 g-ion I-/liter, and less than or equal to 1 g-ion Br-, Cl-, and SCN-/liter). The extraction constants and the thermodynamic extraction characteristics of the cadmium complexes have been determined. In order of their extractability by tributyl phosphate the cadmium halide complexes follow the order: iodide > bromide > chloride > thiocyanate. Extraction of cadmium as its iodide complex by tributyl phosphate enables cadmium to be separated from indium and zinc

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

    OpenAIRE

    HASSAN ALLOUCH; LIBASSE DIOP

    2013-01-01

    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.

  9. 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.

  10. 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.

    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.

  11. Barium iodide single-crystal scintillator detectors

    Energy Technology Data Exchange (ETDEWEB)

    Cherepy, N

    2007-07-30

    We find that the high-Z crystal Barium Iodide is readily growable by the Bridgman growth technique and is less prone to crack compared to Lanthanum Halides. We have grown Barium Iodide crystals: undoped, doped with Ce{sup 3+}, and doped with Eu{sup 2+}. Radioluminescence spectra and time-resolved decay were measured. BaI{sub 2}(Eu) exhibits luminescence from both Eu{sup 2+} at 420 nm ({approx}450 ns decay), and a broad band at 550 nm ({approx}3 {micro}s decay) that we assign to a trapped exciton. The 550 nm luminescence decreases relative to the Eu{sup 2+} luminescence when the Barium Iodide is zone refined prior to crystal growth. We also describe the performance of BaI{sub 2}(Eu) crystals in experimental scintillator detectors.

  12. 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

  13. 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...

  14. Calculation of standard Gibbs energies enthalpies, and entropies of halide solvation

    International Nuclear Information System (INIS)

    The standard Gibbs energies, enthalpies and entropies of halides (F-, Cl-, Br- and I-) in some non-aqueous solvents (acetonitrile, DMSO, alcohols) have been calculated using the Van Arkel thermodynamic cycle. It is shown that the method suggested for the calculation permits evaluation of thermodynamic functions of halide solvation in different solvents proceeding from available experimental values without employing adjustment parameters. 12 refs.; 1 fig.; 3 tabs

  15. Nickel-Catalyzed Regiodivergent Opening of Epoxides with Aryl Halides: Co-Catalysis Controls Regioselectivity

    OpenAIRE

    Zhao, Yang; Daniel J. Weix

    2013-01-01

    Epoxides are versatile intermediates in organic synthesis, but have rarely been employed in cross-coupling reactions. We report that bipyridine-ligated nickel can mediate the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the co-catalyst employed. Iodide co-catalysis results in opening at the less hindered position via an iodohydrin intermediate. Titan...

  16. The influence of the development in silver halide sensitized gelatin holograms derived from PFG-01 plates

    OpenAIRE

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

    1999-01-01

    Silver halide sensitized gelatin (SHSG) is an interesting technique for the production of holographic optical elements. It combines the high sensitivity of photographic emulsions with the well-known low scattering and high diffraction efficiency corresponding to dichromated gelatin. Owing to the fact that Agfa has ceased production of holographic material it is necessary to find and study new silver halide materials for applications in holography. The differences between these new materials a...

  17. Arsine oxidation with heteropoly acid in the presence of halide ions

    International Nuclear Information System (INIS)

    Kinetics and mechanism of arsine oxidation by phosphomolybdovanadium heteropoly acid are studied in the presense of halide ions as catalysts. It is established that intrasphere arsine oxidation in an intermediate V(5) complex with AsH3 and halide-ion is a limiting stage of the proposed mechanism. The quantum-chemical calculation of the electronic structure of intermediate complexes, which supports the above mechanism is carried out. The method of theoretical estimation of the activation energy is proposed

  18. 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.

  19. 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.

  20. Performance of high alkali slag concretes in the context of alkali-silica reaction

    OpenAIRE

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

    2003-01-01

    The depletion of natural resources, the requirement for sustainable development and environmental restrictions, such as those associated with the Kyoto Agreement, makes the re-use of waste materials increasingly important as we enter the new millennium. The use of one such material in concrete, ground granulated blast furnace slag is well-accepted in many parts of the world. However much research and experience of use is based on slags with low alkali levels and low chloride contents. Enviro...

  1. Ultrasonic coal washing to leach alkali elements from coals.

    Science.gov (United States)

    Balakrishnan, S; Reddy, V Midhun; Nagarajan, R

    2015-11-01

    Deposition of fly ash particles onto heat-transfer surfaces is often one of the reasons for unscheduled shut-downs of coal-fired boilers. Fouling deposits encountered in convective sections of a boiler are characterized by arrival of ash particles in solidified (solid) state. Fouling is most frequently caused by condensation and chemical reaction of alkali vapors with the deposited ash particles creating a wet surface conducive to collect impacting ash particles. Hence, the amount of alkali elements present in coals, which, in turn, is available in the flue gas as condensable vapors, determines the formation and growth of fouling deposits. In this context, removal of alkali elements becomes vital when inferior coals having high-ash content are utilized for power generation. With the concept of reducing alkali elements present in a coal entering the combustor, whereby the fouling deposits can either be minimized or be weakened due to absence of alkali gluing effect, the ultrasonic leaching of alkali elements from coals is investigated in this study. Ultrasonic water-washing and chemical-washing, in comparison with agitation, are studied in order to estimate the intensification of the alkali removal process by sonication. PMID:26186840

  2. Superconductivity of Alkali Metals under High Pressure

    CERN Document Server

    Shi, L; Shi, Lei; Papaconstantopoulos, Dimitrios A.

    2005-01-01

    We calculated the superconductivity properties of alkali metals under high pressure using the results of band theory and the rigid-muffin theory of Gaspari and Gyorffy. Our results suggest that at high pressures Lithium, Potassium, Rubidium and Cesium would be superconductors with transition temperatures approaching 10-20 $K$. Our calculations also suggest that Sodium would not be a superconductor under high pressure even if compressed to less than half of its equilibrium volume. We found that the compression of the lattice strengthens the electron-phonon coupling through a delicately balanced increase of both the electronic and phononic components of this coupling. This increase of the electron-phonon coupling in Li is due to an enhancement of the $s$-$p$ channel of the interaction, while in the heavier elements the $p$-$d$ channel is the dominant component.

  3. Superconductivity of Alkali Metals under High Pressure

    Science.gov (United States)

    Shi, Lei; Papaconstantopoulos, Dimitrios

    2006-03-01

    We calculated the superconductivity properties of alkali metals under high pressure using the results of band theory and the rigid-muffin theory of Gaspari and Gyorffy. Our results suggest that at high pressures Lithium, Potassium, Rubidium and Cesium would be superconductors with transition temperatures approaching 10-20 K. Our calculations also show that Sodium would not be a superconductor under high pressure even if compressed to less than half of its equilibrium volume. We found that the compression of the lattice strengthens the electron-phonon coupling through a delicately balanced increase of both the electronic and phononic components of this coupling. This increase of the electron-phonon coupling in Li is due to an enhancement of the s-p channel of the interaction, while in the heavier elements the p-d channel is the dominant component.

  4. Identificationof alkali-silica reaction outcomes ????????????? ???????????????, ????????????? ??????-?????????? ????????

    Directory of Open Access Journals (Sweden)

    Korolev Evgeniy Valer’evich

    2013-06-01

    Full Text Available Portland cement-based concrete is widely used in civil engineering. Therefore, it is very important to determine the preconditions of corrosion of the cement concrete. The service life of concrete structures can be substantially reduced by the alkali-silica reaction. It is well known that this reaction causes formation of the sodium silicate hydrogel. Thus, by identifying this gel, a researcher can make an assumption about the reasons for the corrosion. Obviously, macroscopic quantities of sodium salts can be discerned using analytical chemistry methods. Unfortunately, determinant values of such salts in the concrete structure are usually very small. Thus, there is a need for special research methods.Raman spectroscopy is an advanced method based on the analysis of instantaneous two-photon non-elastic light scattering. This method is applicable even in case of small quantities of chemicals under research. The first successful study of silicates using Raman spectroscopy methods was performed in the 20ies of the 20th century. In this work the authors have proven that sodium hydrogels can be easily identified in the concrete using the Raman spectroscopy. In the course of the analysis of the interphase boundary between the cement stone and the aggregates, the authors observed, at least, one spectral peak which did not belong to cement or to the disperse phases of the concrete. At the same time, this peak can be classified as a peak of the sodium silicate. Thus, sodium silicate gel is generated during the service life of the structure under research, and this research has revealed the presence of the alkali-silica reaction.??????-?????????? ??????? ????? ????????? ? ????????????? ?????????? ????? ???????????? ??????????? ?? ????????? ???????. ?????????? ??????-?????????? ??????? ?????????????? ???????????? ????, ? ?????? ???????? ?????? ????????????? ??????. ????????, ??? ????????????? ???? ?????????? ????? ?????????????? ???????? ????????????? ??????????????? ?????????. ?? ?????? ??????? ?????????? ?? ???????? ?????????? ? ????????? ???????? ??????????????? ? ?????????? ????????? ??????????? ??????? ?????????????? ?????? ?? ??????? ??????? ????????? ?????? — ???????????, ??? ???????? ??????????? ?????????? ??????-?????????? ???????.

  5. Synthesis of tunable-band-gap "Open-Box" halide perovskites by use of anion exchange and internal dissolution procedures.

    Science.gov (United States)

    Wu, Zhengcui; Wang, Baohua; He, Jian; Chen, Tao

    2016-01-01

    We demonstrate the synthesis of cuboid MAPbBr3 (MA=CH3NH3) microcrystals and subsequent conversion into open-box-like MAPb(Br1-xIx)3 (0?x?1) microcrystals by anion exchange in MAI solution. During the substitution of Br(-) with I(-), the initial cuboid framework of MAPbBr3 crystals is retained. The preferential internal dissolution of MAPbBr3 due to the surface coverage and protection of MAPb(Br1-xIx)3 induces voids inside the cuboid crystals, finally leading to open-box-like iodide-rich MAPb(Br1-xIx)3. By controlling the degree of anion exchange, the intense light absorption of the product is able to be tuned in specific wavelengths throughout the visible range. This solution-phase anion exchange approach provides a synthetic strategy in designing sophisticated organolead halide perovskites structures as well as tuning the band gaps for further applications across a range of possible domains. PMID:26397923

  6. Monitoring and control of impurities in liquid alkali metal circuits

    International Nuclear Information System (INIS)

    The paper reviews the monitoring methods and processes for removing impurities from liquid alkali metals in technical plants. Sources of the impurities - in particular oxygen, hydrogen, carbon, nitrogen, corrosion products and fission products are outlined, as well as impurity monitoring in operating liquid alkali metal circuits. On-line measuring devices for the monitoring in plants are described, including the plugging meter, hydrogen meter, tritium meter, oxygen meter, carbon meter, and resistivity meter. Sample preparation, analysis of trace impurities, and purification of alkali metals are also discussed. (U.K.)

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

    Directory of Open Access Journals (Sweden)

    Teodor Malutan

    2008-02-01

    Full Text Available 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 moisture contents, as well as by the amounts of OH groups.

  8. Spectroscopic study of the interactions of alkali fluorides with D-xylose

    Science.gov (United States)

    Fernández-Bertrán, Jose; Reguera, Edilso; Ortiz, Pedro

    2001-11-01

    The interactions of alkali fluorides with D-xylose have been studied by X-ray diffraction (XRD), infrared spectroscopy (IR), nuclear magnetic resonance (NMR, 1H and 13C) and atomic absorption spectrophotometry. KF and CsF form complexes with D-xylose in a 1:1 molar ratio. These complexes can be obtained by solid state milling the reactants in an agate mortar or from methanolic solutions of the sugar and the salt. LiF and NaF do not form complex with D-xylose. IR and XRD prove the identical nature of the complexes obtained by milling and from solution. IR spectra indicate strong perturbation of the OH stretching vibrations with considerable shifts to lower frequencies, which must be caused by strong hydrogen bond formation to the fluorine anion. The perturbations of C?O bond are weak, indicating that cation binding to the oxygen atoms is not the main interaction responsible for the complex formation. 1H NMR spectra of the D-xylose-KF complex dissolved in deuterium oxide is equal to that of pure D-xylose, indicating the destruction of the complex in solution. The complex is stable in DMSO, and 13C spectra of the complex in DMSO-d 6 and in solid state (CPMAS) spectra are in accordance with the observed interactions in the IR spectra. As far as we know, this is the first report of a sugar-halide salt complex in which the anion instead of the cation provides the binding forces.

  9. Iodide compounds of rare earths with alkali metals

    Energy Technology Data Exchange (ETDEWEB)

    Molodkin, A.K.; Dudareva, A.G.

    1986-11-01

    Iodide compounds of rare earths with alkali metal iodides formed in the melt are reviewed. The systems LnI/sub 3/-MeI (Zn=Sm, Gd, Dy, Ho) and YbI/sub 2/-MeI (Me - alkali metal) are investigated for the first time by the DTA, RPA and crystallooptical methods. IR absorption and luminescence spectra of SmI/sub 3/, DyI/sub 3/, HoI/sub 3/, HoBe/sub 3/ and compounds of samarium triiodide with alkali metals iodides are considered. /sup 127/I NQR spectra of iodides: GdI/sub 3/, DyI/sub 3/, HoI/sub 3/ and RbIxHoI/sub 3/ are recorded. Iodide compounds of lanthanides with alkali metals are analyzed and systematized.

  10. Electric field-induced softening of alkali silicate glasses

    Science.gov (United States)

    McLaren, C.; Heffner, W.; Tessarollo, R.; Raj, R.; Jain, H.

    2015-11-01

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  11. 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

  12. Kinetics of molybdenite oxidizing leaching in alkali medium by ozone

    International Nuclear Information System (INIS)

    On the basis of investigation of the process kinetics proposed is a model of oxidizing leaching of molybdenite in alkali medium while ozonization of the solution by ozoneair mixture. A kinetic equation is derived, that describes experimental data satisfactorily

  13. 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

  14. 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.

  15. Enzymatic hydrolysis of sugarcane bagasse pretreated with acid or alkali

    OpenAIRE

    Vivian Cristina Pietrobon; Regina Teresa Rosim Monteiro; Georgia Bertoni Pompeu; Eduardo Poggi e Borges; Mario Lucio Lopes; Henrique Vianna de Amorim; Sandra Helena da Cruz; Ellen Karine Diniz Viégas

    2011-01-01

    The aim of this study was to evaluate the performance of enzymatic hydrolysis of acid or alkali pretreated sugarcane bagasse for the production of fermentable sugars. The first step consisted of selection of commercial enzymes presenting the highest cellulolytic activities. After selection of four enzymes: HPL, CL, P1 and P4, their performances were tested in the bagasse pretreated with acid and alkali. The sugar content of the hydrolysates was analyzed by anion exchange liquid chromatography...

  16. Assessment of concrete bridge decks with alkali silica reactions

    DEFF Research Database (Denmark)

    Eriksen, Kirsten; Jansson, Jacob; Geiker, Mette Rica

    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...

  17. Photoemission spectroscopy study of a multi-alkali photocathode

    CERN Document Server

    Ettema, A R H

    2000-01-01

    In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

  18. Pressure-induced s-band ferromagnetism in alkali metals

    OpenAIRE

    Pickard, Chris J.; Needs, R. J.

    2011-01-01

    First-principles density-functional-theory calculations show that compression of alkali metals stabilizes open structures with localized interstitial electrons which may exhibit a Stoner-type instability towards ferromagnetism. We find ferromagnetic phases of the lithium-IV-type, simple cubic, and simple hexagonal structures in the heavier alkali metals, which may be described as s-band ferromagnets. We predict that the most stable phases of potassium at low temperatures and...

  19. Structural instabilities and superconductivity in the alkali tungsten bronzes

    International Nuclear Information System (INIS)

    A model of local structural states (phases) in the superconducting TI phase of the nonstoichiometric alkali tungsten bronzes Msub(x)WO3 (M an alkali) is shown to be consistent with the dramatic increase of the superconducting transition temperature as x approaches the TII phase boundary value. This model also predicts the existence of (x dependent) anharmonicity and heat capacity anomalies, and it is consistent with the fact that the cubic phase of Nasub(x)WO3 is superconducting. (author)

  20. Condensation of helium in nanoscopic alkali wedges at zero temperature

    OpenAIRE

    Hernández, E. Susana; Ancilotto, Francesco; Barranco Gómez, Manuel; Mayol Sánchez, Ricardo; Pi Pericay, Martí

    2006-01-01

    We present a complete calculation of the structure of liquid $^4$He confined to a concave nanoscopic wedge, as a function of the opening angle of the walls. This is achieved within a finite-range density functional formalism. The results here presented, restricted to alkali metal substrates, illustrate the change in meniscus shape from rather broad to narrow wedges on weak and strong alkali adsorbers, and relate this change to the wetting behavior of helium on the correspond...

  1. Recovering uranium values from alkali carbonate leach solutions

    International Nuclear Information System (INIS)

    A process for recovering uranium value from an alkali carbonate leach liquor containing uranium, molybdenum and vanadium values is claimed. It comprises: precipitating the uranium, molybdenum and vanadium from the liquor by adding a source of a precipitating divalent cation and a hydroxide anion; separating the precipitate from the liquor; and recovering the uranium value from the precipitate by dissolution in acid or alkali and separation of the uranium from the uranium-containing solution formed

  2. Coherent coupling of alkali atoms by random collisions

    OpenAIRE

    Katz, Or; Peleg, Or; Firstenberg, Ofer

    2015-01-01

    Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibriate the spin state of the atoms. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali specie to another specie, mediated by these random collisions. We show that, the minor specie (potassium) inherits the magnetic properties of the dominant specie (rubidium), including its lifetime (T1), coherence time (T2), gyromagnetic ratio, and S...

  3. 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.

  4. Preferential Eu Site Occupation and Its Consequences in the Ternary Luminescent Halides AB2I5?Eu2 + (A =Li -Cs ; B =Sr , Ba)

    Science.gov (United States)

    Fang, C. M.; Biswas, Koushik

    2015-07-01

    Several rare-earth-doped, heavy-metal halides have recently been identified as potential next-generation luminescent materials with high efficiency at low cost. AB2I5?Eu2 + (A =Li - Cs ; B =Sr , Ba) is one such family of halides. Its members, such as CsBa2I5?Eu2 + and KSr2I5?Eu2 + , are currently being investigated as high-performance scintillators with improved sensitivity, light yield, and energy resolution less than 3% at 662 keV. Within the AB2I5 family, our first-principles-based calculations reveal two remarkably different trends in Eu site occupation. The substitutional Eu ions occupy both eightfold-coordinated B1 (VIII ) and the sevenfold-coordinated B2 (VII ) sites in the Sr-containing compounds. However, in the Ba-containing crystals, Eu ions strongly prefer the B2 (VII ) sites. This random versus preferential distribution of Eu affects their electronic properties. The calculations also suggest that in the Ba-containing compounds one can expect the formation of Eu-rich domains. These results provide atomistic insight into recent experimental observations about the concentration and temperature effects in Eu-doped CsBa2I5 . We discuss the implications of our results with respect to luminescent properties and applications. We also hypothesize Sr, Ba-mixed quaternary iodides ABaVIIISrVIII5?Eu as scintillators having enhanced homogeneity and electronic properties.

  5. 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.

  6. Luminescence, autolocalization and decay of excitons on defects in ionic crystals (CsBr)

    International Nuclear Information System (INIS)

    The review is made of investigations on specific features of excitons in alkali haloid crystals: existence of free and autolocalized excitons, autolocalizing excitons with defects production, defects recombination with luminescent exciton production, cubic crystals (mainly CsBr) taken as an exsample

  7. 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

  8. 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)

  9. Alkali-slag cements for the immobilization of radioactive wastes

    International Nuclear Information System (INIS)

    Alkali-slag cements consist of glassy slag and an alkaline activator and can show both higher early and later strengths than Type III Portland cement, if a proper alkaline activator is used. An examination of microstructure of hardened alkali-slag cement pastes with the help of XRD and SEM with EDAX shows that the main hydration product is C-S-H (B) with low C/S ratio and no crystalline substances exist such as Ca(OH)2, Al (OH)3 and sulphoaluminates. Mercury intrusion tests indicate that hardened alkali-slag cement pastes have a lower porosity than ordinary Portland cement, and contain mainly gel pores. The fine pore structure of hardened alkali-slag cement pastes will restrict the ingress of deleterious substances and the leaching of harmful species such as radionuclides. The leachability of Cs+ from hardened alkali-slag cement pastes is only half of that from hardened Portland cement. From all these aspects, it is concluded that alkali-slag cements are a better solidification matrix than Portland cement for radioactive wastes

  10. 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.

  11. 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 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

  12. Effects of halides on reaction of nucleosides with ozone.

    Science.gov (United States)

    Suzuki, Toshinori; Kaya, Eriko; Inukai, Michiyo

    2012-01-01

    Ozone (O(3)), a major component of photochemical oxidants, is used recently as a deodorizer in living spaces. It has been reported that O(3) can directly react with DNA, causing mutagenesis in human cells and carcinogenesis in mice. However, little is known about the effects of coexistent ions in the reaction of O(3). In the present study, we analyzed the effects of halides on the reaction of O(3) with nucleosides using reversed-phase high-performance liquid chromatography with ultraviolet detection. When aqueous O(3) solution was added to a nucleoside mixture in potassium phosphate buffer (pH 7.3), the nucleosides were consumed with the following decreasing order of importance: dGuo > Thd > dCyd > dAdo. The effects of addition of fluoride and chloride in the system were slight. Bromide suppressed the reactions of dGuo, Thd, and dAdo but enhanced the reaction of dCyd. The major products were 5-hydroxy-2'-deoxycytidine, 5-bromo-2'-deoxycytidine, and 8-bromo-2'-deoxyguanosine. The time course and pH dependence of the product yield indicated formation of hypobromous acid as the reactive agent. Iodide suppressed all the reactions effectively. The results suggest that bromide may alter the mutation spectrum by O(3) in humans. PMID:22646086

  13. Raman Spectroscopy of Organic-Inorganic Halide Perovskites.

    Science.gov (United States)

    Ledinský, Martin; Löper, Philipp; Niesen, Bjoern; Holovský, Jakub; Moon, Soo-Jin; Yum, Jun-Ho; De Wolf, Stefaan; Fejfar, Antonín; Ballif, Christophe

    2015-02-01

    Micro-Raman spectroscopy provides laterally resolved microstructural information for a broad range of materials. In this Letter, we apply this technique to tri-iodide (CH3NH3PbI3), tribromide (CH3NH3PbBr3), and mixed iodide-bromide (CH3NH3PbI3-xBrx) organic-inorganic halide perovskite thin films and discuss necessary conditions to obtain reliable data. We explain how to measure Raman spectra of pristine CH3NH3PbI3 layers and discuss the distinct Raman bands that develop during moisture-induced degradation. We also prove unambiguously that the final degradation products contain pure PbI2. Moreover, we describe CH3NH3PbI3-xBrx Raman spectra and discuss how the perovskite crystallographic symmetries affect the Raman band intensities and spectral shapes. On the basis of the dependence of the Raman shift on the iodide-to-bromide ratio, we show that Raman spectroscopy is a fast and nondestructive method for the evaluation of the relative iodide-to-bromide ratio. PMID:26261955

  14. 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.)

  15. 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

  16. Tungsten Chemistry in Alkali Chloride Melts

    Science.gov (United States)

    Danilov, Danil A.; Volkovich, Vladimir A.; Vasin, Boris D.; Polovov, Ilya B.; Griffiths, Trevor R.

    2007-12-01

    Speciation of tungsten in alkali chloride melts (based on NaCl-2CsCl, NaCl-KCl and 3LiCl-2KCl mixtures) was studied between 550 and 750?C using electronic absorption spectroscopy. OnlyW(IV) and W(V) chloro and oxychloro species can be stabilized under the conditions studied. Tungsten(IV) chloride ions are very sensitive to oxide/hydroxide impurities present in the melt. Anodic dissolution ofWmetal at anodic current densities in the range of 0.005 - 0.1 A/cm2 produces only [WCl6]2- ions that can be electrochemically (on a glassy carbon anode) oxidized to [WCl6]-. Small amounts of oxide ions present in the melt result in a gradual conversion of W(IV) chloro species intoW(IV) oxychloro species. In the presence of O2 in the atmosphere [WCl6]2- is oxidized into the tungsten(V) species [WOCl5]2-. Dissolution of tungsten hexachloride, WCl6, in an NaCl-2CsCl melt initially yields [WCl6]2- (due to disproportionation). Reaction of metallic tungsten with Pd(II)-containing melts results in the formation of [WCl6]2- species. The main spectroscopic parameters of [WCl6]2- and [WCl6]- complex ions were calculated.

  17. Magnetoelectric Jones spectroscopy of alkali atoms

    Energy Technology Data Exchange (ETDEWEB)

    Chernushkin, V V; Mironova, P V; Ovsiannikov, V D [Department of Physics, Voronezh State University, 394006, Voronezh (Russian Federation)], E-mail: albert@phys.vsu.ru

    2008-06-14

    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.

  18. 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).

  19. 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.

  20. 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.

  1. Compositional dependence of the quantum efficiency of the transition at 1.3?m of praseodymium in halide glasses

    International Nuclear Information System (INIS)

    This paper discusses an improvement in the quantum efficiency of the 1.3 ?m transition of Pr3+ achieved as a result of doping alternative halide glasses. An increase from 3.4% in ZBLAN to 9.9% in a multicomponent halide glass is reported

  2. The reaction dynamics of alkali dimer molecules and electronically excited alkali atoms with simple molecules

    Energy Technology Data Exchange (ETDEWEB)

    Hou, H [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-12-01

    This dissertation presents the results from the crossed molecular beam studies on the dynamics of bimolecular collisions in the gas phase. The primary subjects include the interactions of alkali dimer molecules with simple molecules, and the inelastic scattering of electronically excited alkali atoms with O2. The reaction of the sodium dimers with oxygen molecules is described in Chapter 2. Two reaction pathways were observed for this four-center molecule-molecule reaction, i.e. the formations of NaO2 + Na and NaO + NaO. NaO2 products exhibit a very anisotropic angular distribution, indicating a direct spectator stripping mechanism for this reaction channel. The NaO formation follows the bond breaking of O2, which is likely a result of a charge transfer from Na2 to the excited state orbital of O2-. The scattering of sodium dimers from ammonium and methanol produced novel molecules, NaNH3 and Na(CH3OH), respectively. These experimental observations, as well as the discussions on the reaction dynamics and the chemical bonding within these molecules, will be presented in Chapter 3. The lower limits for the bond dissociation energies of these molecules are also obtained. Finally, Chapter 4 describes the energy transfer between oxygen molecules and electronically excited sodium atoms.

  3. 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 ...

  4. Modelisation and numerical simulation for bulk crystal growth processes

    International Nuclear Information System (INIS)

    The aim of this work is to study the relevance of numerical simulation for improving the process control in the field of crystal growth. This investigation focused on the growth of semiconductor and halide crystals by the Bridgman solidification technique, the principle of which is to cool a seeded feed material contained in a crucible, either by pulling the crucible or by decreasing the temperature in the furnace. Calculations are performed with the finite element method, and for comparison, experiments are carried out on Bridgman pulling machines operating either in a laboratory or in industrial plants. Calculations and experimental data have shown a good agreement and a satisfactory reliability

  5. 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 8.9-9 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

  6. Mesoporous zeolite single crystals for catalytic hydrocarbon conversion

    DEFF Research Database (Denmark)

    Schmidt, I.; Christensen, C.H.; Hasselriis, Peter; Kustova, Marina; Nielsen, Michael Brorson; Dahl, Søren; Johannsen, K.; Christensen, Claus H.

    2005-01-01

    Recently, mesoporous zeolite single crystals were discovered. They constitute a novel family of materials that features a combined micropore and mesopore architecture within each individual crystal. Here, we briefly summarize recent catalytic results from cracking and isomerization of alkalies, alkylation of aromatics and present new results on isomerization of aromatics. Specifically, the shape-selective isomerization of meta-xylenc into para-xylene and ortho-xylene is studied. In all these rea...

  7. Cobalt-catalyzed reductive coupling of saturated alkyl halides with activated alkenes.

    Science.gov (United States)

    Shukla, Paritosh; Hsu, Yun-Chu; Cheng, Chien-Hong

    2006-01-20

    [reaction: see text] An efficient cobalt-catalyzed reductive coupling reaction of alkyl halides with electron-withdrawing alkenes (CH(2)=CR(1)EWG, EWG = electron-withdrawing group) in the presence of water and zinc powder in acetonitrile to give the corresponding Michael-type addition product (RCH(2)CR(1)EWG) was described. The methodology is versatile such that unactivated primary, secondary, and tertiary alkyl bromides and iodides and various conjugated alkenes including acrylates, acrylonitrile, methyl vinyl ketone, and vinyl sulfone all successfully participate in this coupling reaction. For the alkyl halides used in the reaction, the iodides generally gave better yields compared to those of the corresponding bromides. It is a unique method employing CoI(2)dppe, zinc, and alkyl halides, affording conjugate addition products in high yields. Mechanistically, the reaction appears to follow an oxidative addition driven route rather than the previously reported radical route. PMID:16408976

  8. Catalysis by desolvation: the catalytic prowess of SAM-dependent halide-alkylating enzymes.

    Science.gov (United States)

    Lohman, Danielle C; Edwards, David R; Wolfenden, Richard

    2013-10-01

    In the biological fixation of halide ions, several enzymes have been found to catalyze alkyl transfer from S-adenosylmethionine to halide ions. It proves possible to measure the rates of reaction of the trimethylsulfonium ion with I(-), Br(-), Cl(-), F(-), HO(-), and H2O in water at elevated temperatures. Comparison of the resulting second-order rate constants, extrapolated to 25 °C, with the values of k(cat)/K(m) reported for fluorinase and chlorinase indicates that these enzymes enhance the rates of alkyl halide formation by factors of 2 × 10(15)- and 1 × 10(17)-fold, respectively. These rate enhancements, achieved without the assistance of cofactors, metal ions, or general acid-base catalysis, are the largest that have been reported for an enzyme that acts on two substrates. PMID:24041082

  9. Oxidant-Free Au(I)-Catalyzed Halide Exchange and Csp2-O Bond Forming Reactions.

    Science.gov (United States)

    Serra, Jordi; Whiteoak, Christopher J; Acuña-Parés, Ferran; Font, Marc; Luis, Josep M; Lloret-Fillol, Julio; Ribas, Xavi

    2015-10-21

    Au has been demonstrated to mediate a number of organic transformations through the utilization of its ? Lewis acid character, Au(I)/Au(III) redox properties or a combination of both. As a result of the high oxidation potential of the Au(I)/Au(III) couple, redox catalysis involving Au typically requires the use of a strong external oxidant. This study demonstrates unusual external oxidant-free Au(I)-catalyzed halide exchange (including fluorination) and Csp2-O bond formation reactions utilizing a model aryl halide macrocyclic substrate. Additionally, the halide exchange and Csp2-O coupling reactivity could also be extrapolated to substrates bearing a single chelating group, providing further insight into the reaction mechanism. This work provides the first examples of external oxidant-free Au(I)-catalyzed carbon-heteroatom cross-coupling reactions. PMID:26397959

  10. Studies on radiation-sensitive nonsilver halide materials, (1)

    International Nuclear Information System (INIS)

    In order to discover new radiation-sensitive nonsilver halide materials, the coloration based on the formation of Stenhouse salts was studied in the following three systems: (a) furfural-amine/HCl aq/methanol solution, (b) furfural-amine/polyhalogenide/PMMA matrix, (c) furfural-amine/PVC matrix. Firstly, forty-five aromatic amines were surveyed to find out the amines suitable for the color precursors (reactant from furfural and amine) in the system (a). As a result, the five amines, which gave the precursors in good yields by the reaction with furfural, were selected: m-nitroaniline, N-methylaniline, m-methyl-N-methylaniline, aniline, and o-methoxyaniline. Secondly, the coloration induced by electron beam bombardment was studied in the systems (b) and (c) containing the color precursors (the reactants from these amines and furfural). Although the PMMA films containing the color precursors and polyhalogenides were sensitive to electron beam, they were not stable when standing under daylight at room temperature. The PVC films containing the color precursors were very stable and colored to reddish yellow (lambda sub(max) 498 - 545 nm) by electron beam bombardment. The PVC film containing N-methylaniline-furfural was the most sensitive and the increase in absorbance at 498 nm was 0.78 by electron beam bombardment of 60 kV - 7.5 x 10-7C/cm2. A good linear relationship existed between the degree of coloration and the amounts of electron beam bombardment in the range from 0 to 10-6C/cm2. (author)

  11. Optical properties of metallic nanoparticles synthesized by implantation of alkali ions in LiF

    International Nuclear Information System (INIS)

    The optical functions of metallic particles, resulting from the precipitation of alkali ions implanted in LiF crystals, have been calculated from optical absorption and reflectivity measurements in the photon energy range 0.4-6 eV. Optical data are analyzed in terms of local electrical field effects. The real part of the dielectric function remains positive in the whole energy spectrum, in opposition to the one calculated in the Maxwell-garnett approximation where enhanced reflections should correspond to negative values of the dielectric function. Additional resonances shown by the energy loss function are responsible for this discrepancy. An absorption peak associated to Li precipitates and a secondary peak of the plasma resonance are revealed, so as a loss structure at 5 eV due to F centres also detected in electron energy loss spectrometry (REELS). Implications for non linear optical properties are addressed. (Author)

  12. 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

  13. Interconnection between structures of halides and oxides of heavy transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Drobot, D.V.; Pisarev, E.A. (Moskovskij Inst. Tonkoj Khimicheskoj Tekhnologii (USSR))

    1983-01-01

    A variant of genesis of halide structural grounds of formally group 4 through group 6 valent heavy transition metals is proposed on the assumption that octahedron coordination of the metal is invariable. The tungsten hexachloride structure is chosen as the basis. The nickel arsenide structure is chosen as the basic one for consideration of the interconnection between crystalline structures of halides of groups 4 through 7 of the Periodic system. Analysis of the interconnection between the structures permits to assume a possible existence of the variable composition phases on the base of lower halogen - and oxohalogen-derivatiives of the heavy transition metals.

  14. New mechanism for glomerular injury. Myeloperoxidase-hydrogen peroxide-halide system.

    OpenAIRE

    Johnson, R. J.; W. G. Couser; 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. Designing mixed metal halide ammines for ammonia storage using density functional theory and genetic algorithms

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen; Quaade, Ulrich J.; Vegge, Tejs

    2014-01-01

    Metal halide ammines have great potential as a future, high-density energy carrier in vehicles. So far known materials, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, are not suitable for automotive, fuel cell applications, because the release of ammonia is a multi-step reaction, requiring too much heat to be supplied, making the total efficiency lower. Here, we apply density functional theory (DFT) calculations to predict new mixed metal halide ammines with improved storage capacities and the ability to rel...

  16. Highly efficient route to fused polycyclic aromatics via palladium-catalyzed aryne annulation by aryl halides.

    Science.gov (United States)

    Liu, Zhijian; Larock, Richard C

    2007-01-01

    Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products. PMID:17194103

  17. The silver ions contribution into the cytotoxic activity of silver and silver halides nanoparticles

    Science.gov (United States)

    Klimov, A. I.; Zherebin, P. M.; Gusev, A. A.; Kudrinskiy, A. A.; Krutyakov, Y. A.

    2015-11-01

    The biocidal action of silver nanoparticles capped with sodium citrate and silver halides nanoparticles capped with non-ionic surfactant polyoxyethylene(20)sorbitan monooleate (Tween 80®) against yeast cells Saccharomyces cerevisiae was compared to the effect produced by silver nitrate and studied through the measurement of cell loss and kinetics of K+ efflux from the cells. The cytotoxicity of the obtained colloids was strongly correlated with silver ion content in the dispersions. The results clearly indicated that silver and silver halides nanoparticles destroyed yeast cells through the intermediate producing of silver ions either by dissolving of salts or by oxidation of silver.

  18. Cobalt-catalyzed ortho alkylation of aromatic imines with primary and secondary alkyl halides.

    Science.gov (United States)

    Gao, Ke; Yoshikai, Naohiko

    2013-06-26

    We report here cobalt-N-heterocyclic carbene catalytic systems for the ortho alkylation of aromatic imines with alkyl chlorides and bromides, which allows the introduction of a variety of primary and secondary alkyl groups at room temperature. The stereochemical outcomes of the reaction of secondary alkyl halides suggest that the present reaction involves single-electron transfer from a cobalt species to the alkyl halide to generate the corresponding alkyl radical. A cycloalkylated product obtained by this method can be transformed into unique spirocycles through manipulation of the directing and cycloalkyl groups. PMID:23758603

  19. Microwave and Nuclear Excitations of Alkali Metal Vapors

    Science.gov (United States)

    Lin, Li-Te Steven

    Alkali metals have been evaluated as the most promising candidates with the highest photon production efficiency (40-50%) in the visible-to-infrared region for flashlamps. Alkali metal excimers with a bound-free transition are proposed as the agents for such an efficient photon -generating process. In this study, these issues are examined by microwave excitation with sodium and rubidium, and nuclear excitation with only sodium. Microwave-excited alkali metal fluorescence has been demonstrated by a microwave-driven alkali metal lamp with a specially designed heat-pipe confinement. Two major emissions are studied: (1) atomic emission, as the major contribution in microwave excitation and electric discharge, and (2) excimer emission, as the agent for high efficiency and potential applications for high power, tunable lasers. Atomic emission dominated the microwave-excited alkali metal spectra, especially the D line. The suppression of atomic emission occurred while increasing the vapor pressure. Self-absorption and line broadening of the D line at high vapor pressure were observed. The experimental fluorescence efficiency of alkali metal vapors, obtained in microwave excitation, was in good agreement with the theoretical predictions. The branching ratio for pumping the upper level state of the excimer transition is the key point for obtaining practically efficient excimer fluorescers. The alkali metal excimer emission was not identified with certainty in microwave excitation due to the ambiguous structure. However, the considerable elevation of the peak base at 436 and 452 nm for the sodium spectra, and the red shift of the primary peak in the broad continuum for the rubidium spectra, confirmed the existence of alkali metal excimer emissions. The nuclear excitation experiment was performed in a TRIGA reactor with a double-encapsulated heat pipe to generate the sodium vapor. ^3He was used as a nuclear volume energy source. The first observation of nuclear-excited sodium excimer emission at 436 nm was successfully obtained with 810 Torr of ^3He at 924 K (Na = 52.7 Torr). Similar suppression and self-absorption of the 3D to 3P atomic line confirms the results of microwave excitation. This experiment established the physical feasibility of nuclear-driven alkali metal excimer lamps.

  20. 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)

  1. Maternal exposure to alkali, alkali earth, transition and other metals: Concentrations and predictors of exposure.

    Science.gov (United States)

    Hinwood, A L; Stasinska, A; Callan, A C; Heyworth, J; Ramalingam, M; Boyce, M; McCafferty, P; Odland, J Ø

    2015-09-01

    Most studies of metals exposure focus on the heavy metals. There are many other metals (the transition, alkali and alkaline earth metals in particular) in common use in electronics, defense industries, emitted via combustion and which are naturally present in the environment, that have received limited attention in terms of human exposure. We analysed samples of whole blood (172), urine (173) and drinking water (172) for antimony, beryllium, bismuth, cesium, gallium, rubidium, silver, strontium, thallium, thorium and vanadium using ICPMS. In general most metals concentrations were low and below the analytical limit of detection with some high concentrations observed. Few factors examined in regression models were shown to influence biological metals concentrations and explained little of the variation. Further study is required to establish the source of metals exposures at the high end of the ranges of concentrations measured and the potential for any adverse health impacts in children. PMID:25984984

  2. 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.

  3. Behaviour of gaseous alkali compounds from coal gasification

    International Nuclear Information System (INIS)

    In this project the behaviour of alkali compounds has been studied with a chemical equilibrium model. The goal is to evaluate the possibilities to remove the sodium and potassium compounds together with the fly ash particles by using a ceramic honeycomb filter. The studied processes include both CO2/O2- and air-blown gasification and combustion. The results show that the difference between the processes with flue gas recirculation and air-blown processes is small. This is due to that the equilibrium concentration of the dominant gaseous alkali compound, chloride, is more or less the same in both processes. This research project is closely connected to the EU-project coordinated by the Delft University of Technology (DUT). In that project alkali concentration of the fuel gas from a 1.6 MW pilot plant will be measured. During the next phase of this research the results from DUT will be compared with the results of this presentation. (author)

  4. Spectroscopic and theoretical study on alkali metal phenylacetates

    Science.gov (United States)

    Regulska, E.; ?wis?ocka, R.; Samsonowicz, M.; Lewandowski, W.

    2013-07-01

    The influence of lithium, sodium, potassium, rubidium and cesium cations on the electronic system of phenylacetic acid was studied. The FT-IR, FT-Raman and 1H and 13C NMR spectra were recorded for studied compounds. Characteristic shifts in IR and NMR spectra along alkali metal phenylacetates were observed. Good correlations between the wavenumbers of the vibrational bands in the IR spectra of phenylacetates and some alkali metal parameters such as ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy were found. The density functional hybrid method B3LYP with 6-311++G** basis set was used to calculate optimized geometrical structures of studied compounds. Aromaticity indices, atomic charges, dipole moments and energies were calculated as well as the wavenumbers and intensities of IR spectra and chemical shifts in NMR spectra. The theoretical parameters were compared to experimental characteristic of alkali metal phenylacetates.

  5. Ionization reactions of metal hexafluorides with alkali atoms and dimers

    International Nuclear Information System (INIS)

    Ionization reactions are observed in crossed beams, usually of thermal energy, of alkalis and MoF6, WF6, and UF6. Previous studies have indicated large electron affinities for these hexafluorides, and this is confirmed here. Ionization at thermal energies proceeds with the alkali dimers A2 for the three hexafluorides, but with alkali atoms A only for UF6. Several ionization paths are observed, allowing the deduction of molecular energies. A few experiments are done with eV-range beams. Lower limits for the electron affinities are 4.5, 3.3, 4.9, 4.3, and 1.9 eV for MoF6, MoF5, WF6, UF6, and UF5, respectively. Possible mechanisms are discussed

  6. Quadrupole splittings of alkali NMR signals in decylammoniumchloride mesophases

    International Nuclear Information System (INIS)

    In lyotropic mesophases of decylammoniumchloride the NMR signals of the alkali nuclei 6Li, 7Li, 23Na, 39K, 85Rb, 87Rb and 133Cs solubilized in these mesophases have been observed. The linewidths of the signals are comparable with the linewidths in aqueous solutions. Apart from 6Li and 39K for all other alkali nuclei in the mesophases first-order quadrupole splitted spectra have been observed. For the rubidium isotopes 85Rb and 87RB a ratio of the quadrupole splitting of 2.01 +- 0.05 has been determined. Further the chemical shifts of the solubilized alkali nuclei relative to infinitely diluted aqueous solutions have been measured. (orig.)

  7. Low-frequency Raman scattering in alkali tellurite glasses

    Indian Academy of Sciences (India)

    Angelos G Kalampounias

    2008-10-01

    Raman scattering has been employed to study the alkali-cation size dependence and the polarization characteristics of the low-frequency modes for the glass-forming tellurite mixtures, 0.1M2O–0.9TeO2 (M = Na, K, Rb and Cs). The analysis has shown that the Raman coupling coefficient alters by varying the type of the alkali cation. The addition of alkali modifier in the tellurite network leads to the conversion of the TeO4 units to TeO3 units with a varying number of non-bridging oxygen atoms. Emphasis has also been given to the lowfrequency modes and particular points related to the low-frequency Raman phenomenology are discussed in view of the experimental findings.

  8. CRYSTAL POLYMORPHISM IN 1-BUTYL-3-METHYLIMIDAZOLIUM HALIDES: SUPPORTING IONIC LIQUID FORMATION THROUGH INHIBITION OF CRYSTALLIZATION. (R828257)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. Electronic states at (110) surface of cesium halides

    International Nuclear Information System (INIS)

    The electronic structure of valence bands of the CsCl, CsBr and CsI crystals is calculated taking into account spin-orbital interaction. The Slater-Koster interpolation procedure is used in the method of linear combination of atomic orbits. Using the Green function method the electronic states at the (110) surface of these crystals is calculated. It is found that surface states appear above the valence bands and in the forbidden energy gap in the continuous band spectrum range

  10. Poly(ethylene glycol) cationization with alkali metals in matrix-assisted laser desorption ionization investigated with the solvent-free method

    Science.gov (United States)

    Hortal, Ana R.; Hurtado, Paola; Martínez-Haya, Bruno; Arregui, Andrés; Bañares, Luis

    2008-09-01

    Matrix-assisted laser desorption ionization (MALDI) was applied to determine the relative efficiencies for attachment of alkali cations to poly(ethylene glycol) polymers. The solvent-free sample preparation method was employed in order to discriminate the gas-phase polymer-cation complex formation mechanism from solubility and co-crystallization effects. We show that the cohesion energy of the cation precursor has a strong influence on the outcome of the MALDI measurements. This potential drawback is circumvented by the simultaneous use of alkali salts of similar lattice energy. The experiments include chain polymers of different length (PEG600 and PEG1000) and alkali cations of different size (Na+, K+, Cs+). We found that the attachment efficiencies decrease with growing cation size. This decrease is significantly more rapid for the shorter PEG600 polymers. These results corroborate the general trends observed in earlier studies, but correct the dependence on alkali cation size assessed in previous MALDI experiments with the conventional dried-droplet sample preparation method.

  11. 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 (pH<0.5) and consequently an increase in the ash dissolution rate. Moreover reduced iron carrying minerals (e.g. fayalite) 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.

  12. GaN nanotubes grown by halide vapor phase epitaxy

    International Nuclear Information System (INIS)

    Full text: Wide-band gap GaN nanostructures such as quantum dots, nanorods, nanowires, nano columns and nanotubes have a strong potential within areas of biochemical sensing, nanofluidics, and optoelectronics. GaN nanotubes play a role of the building blocks for several applications such as solution-based transistors and highly sensitive nanotube molecular sensors. We have studied non-catalytic and Au-assisted growth of GaN nanotubes using halide vapor phase epitaxy (HVPE) technique. The growth was performed in the temperature range 480 degrees Celsius to 520 degrees Celsius using pure N2 as a carrier gas at atmospheric pressure. The nanotubes size, shape, density and the selectivity of growth have been studied depending on V/III ratio, growth temperature and substrate material. By increasing the GaCl partial pressure, the structure changed from dot-like to nanotubes. The nanotubes were about 1 ?m long with a diameter of typically 200 nm. In addition, it was observed that the nanostructures were spontaneously nucleated at droplets of Ga or, when using Au-coated Al2O3, on droplets of Au/Ga alloy. By varying the growth temperature, the inner diameter of the nanotubes could be controlled. A growth model is suggested, where the nanotubes are nucleated at droplets of Ga or an Au/Ga alloy. Our experimental results suggest that the approach with pre-patterned Au-coated Al2O3 substrates has the potential for fabrication of well-organized nanotubes with a high density. Nanostructures were characterized using electron microscopy methods and by low temperature time-resolved photoluminescence (TRPL). Studies were performed on samples with different wall thickness in the range of 35-75 nm. Two recombination processes with different dynamics contribute to the emission spectra of the GaN nanotubes. The photoluminescence peak shifts rapidly to the higher energy from 3.47 eV to 3.75 eV within a very short time of 30 ps. The origin of the emission having a short lifetime is related to the near band gap luminescence in GaN, while the higher energy luminescence with a relatively slow decay of 2 ns is associated with the interface underlayer formed on the substrate during the growth. (authors)

  13. 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.

  14. Relaxation time scales in collective dynamics of liquid alkali metals

    CERN Document Server

    Mokshin, A V; Hänggi, P; Mokshin, Anatolii V.; Yulmetyev, Renat M.; H\\"anggi, Peter

    2004-01-01

    In this paper the investigation of the dynamical processes of liquid alkali metals is executed by analyzing the time scales of relaxation processes in liquids. The obtained theoretical dynamic structure factor $S(k,\\omega)$ for the case of liquid lithium is found to be in excellent agreement with the recently received inelastic X-ray scattering data. The comparison and interrelation with other theories are given here. Finally, an important part of this paper is the confirmation of the scale uniformity of the dynamic processes in liquid alkali metals predicted by some previous molecular dynamic simulation studies.

  15. Single Stage Brine Filtration System in Chlor-Alkali Industries

    Directory of Open Access Journals (Sweden)

    Unnikrishnan H

    2014-03-01

    Full Text Available The Conventional Brine Filtration in Chlor-Alkali industries is done using clarifier and precoat systems which is time consuming and requires huge amount of electricity .It also generates large amount of sludge causing environmental pollution .The maintenance cost is also high these problems are overcome by single stage brine filtration system. This report compares the present and conventional filtration systems and its benefits. The use of new system like PTFE membrane for brine filtration is also included. This report is based on the study conducted on one of the Chlor - Alkali plant in Kerala.

  16. 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

  17. The behaviour of gaseous alkali compounds in coal gasification

    International Nuclear Information System (INIS)

    In this project the behaviour of alkali compounds emitting from CO2/O2-and air gasification will be studied by using an equilibrium model developed at the Aabo Akademi. This research project is closely connected to the EU-project coordinated by the Delft University of Technology (DUT). In that project alkali emissions from a 1.6 MW pilot plant are measured. The results from those measurements will be compared with the calculations performed in this LIEKKI 2 -project. Furthermore, in the project carried out at DUT the behaviour of a honeycomb-structured filter under CO2/O2 -gasification environment is going to be studied. (author)

  18. Density and thermal expansion of liquid alkali metals

    International Nuclear Information System (INIS)

    The paper reviews the work carried out on the density and thermal expansion of liquid alkali metals. Experimental methods to investigate these physical properties are described, including hydrostatic weighing, and the dilatometer, pycnometer, weighed pycnometer, penetrating radiation, maximum gas bubble pressure, and 'rocking ampoule' techniques. Statistical processing of the data from such experiments is outlined, together with the processed results for density and the temperature coefficient of volumetric expansion. Recommended reference data on the density and thermal expansion of the liquid alkali metals: sodium, lithium, potassium, rubidium and caesium, are given in tabular form. (U.K.)

  19. 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 ...

  20. Effects of the material composition in the TL curves of alkaline halides with Eu2+ exposed to ? radiation

    International Nuclear Information System (INIS)

    The solid state dosemeters plays a very important paper in the growing use of the ionizing radiation. When being increased the use of the radioactive isotopes in the medicine and in the industry, the necessity to have materials but adapted in each case it has increased. To synthesize such materials, it is necessary to enlarge the knowledge on the paper that its play the physical characteristics of the crystals such as the crystalline structure, the lattice constant, imbibed nano structures, dislocations, ions size, electronic states of the ions, etc., on the effects of the ionizing radiation. In the past its have been carried out many studies approaching these problems in some materials, but we consider that its are insufficient before the challenges of the applications. To contribute to the understanding of these effects, we present a study focused to alkaline halide crystals impurified with Eu2+ ions, making an analysis on the paper that its play a) the ions concentration of Eu2+ in KBr: Eu2+, b) the different sites of trapping of electrons and holes in KBr: Eu2+, KCl: Eu2+, RbBr:Eu2+, RbCl: Eu2+ and c) the composition of the crystalline solid solutions KClxBr1-X: Eu2+ and RbCIxKBr1-x: Eu2+ on the thermoluminescence curve when these materials are exposed to small dose of ? irradiation. The increase in the concentration of Eu2+ ions produces a smaller relative intensity of the emissions of high temperature for a given dose and it is found that in a RbClxKBr1-x: Eu2+ with the greater/smaller concentration of Cl- ions, the temperature of the characteristic emission is near to the 453/373 K. The composition x of halogenous ions and not the one of alkaline in the crystalline solid solution dominates the landslide of the temperature of the emission. (Author)

  1. Field test results of in-place charcoal adsorber leak-testing by pulse mode halide injection

    International Nuclear Information System (INIS)

    Current recognized practices for adsorber in-place leak tests in the nuclear industry are by the use of intermittent sampling gas chromatographs, or by continuous sampling and continuous read-out halide detectors. Both test methods normally utilize the continuous halide injection technique when testing to ANSI/ASME-N510, Testing of Nuclear Air-Cleaning Systems. The use of continuous reading halide detectors and pulse mode halide injection has made in-place leak testing of charcoal adsorber banks possible, where short halide delay times caused by high humidity and/or high airflow and where the release of contaminants from the adsorber surface interfere with data interpretation and subsequent test results. Interpretations of response curves from actual field measurements are given as examples, where leak test data acquired by previously described methods could not give a definite interpretation. The pulse mode halide injection method with continuous reading halide detection also provides additional information about available adsorbent surface sites and utilizes significantly less fluorocarbon, an already suggested practice

  2. Process for producing tungsten monocarbide

    International Nuclear Information System (INIS)

    This patent describes a process for producing coarse tungsten monocarbide crystals. It comprises providing an alkali metal halide salt containing tungsten oxide; reacting a solid carbonaceous reactant selected from the group consisting of natural flake graphite, carbon black, HPN-200 graphite and sugar with the alkali metal halide salt containing tungsten oxide without sparging with a hydrocarbon gas to produce coarse tungsten monocarbide crystals at least 50% of which are larger than 15 micrometers; and removing the coarse tungsten monocarbide crystals from the remaining reaction products and any unreacted material

  3. 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)

  4. Halogen bonding-enhanced electrochemical halide anion sensing by redox-active ferrocene receptors.

    Science.gov (United States)

    Lim, Jason Y C; Cunningham, Matthew J; Davis, Jason J; Beer, Paul D

    2015-09-17

    The first examples of halogen bonding redox-active ferrocene receptors and their anion electrochemical sensing properties are reported. Halogen bonding was found to significantly amplify the magnitude of the receptor's metallocene redox-couple's voltammetric responses for halide sensing compared to their hydrogen bonding analogues in both acetonitrile and aqueous-acetonitrile solvent media. PMID:26289779

  5. Solution structure and behavior of dimeric uranium(III) metallocene halides

    International Nuclear Information System (INIS)

    The variable-temperature 1H NMR behavior of the uranium(III) dimers [Cp double-prime 2UX]2 and [Cpdouble-dagger2UX]2, where X is F, Cl, Br, or I, Cp double-prime is 1,3-(Me3Si)2C5H3, and Cpdouble-dagger is 1,3-(Me3C)2C5H3, has been examined. At low temperature, the number of inequivalent CMe3 or SiMe3 groups implies that the solution structure is the same as the solid-state structure in all of these complexes. The barriers to ring rotation in the Cp double-prime series are strongly dependent upon the U-X distance, but all of the barriers to ring rotation in the Cpdouble-dagger series are the same. The trends in ring rotation barriers are explained by the different conformations of the Cp ligands in the dimers. In addition to the homo-halide dimers, the variable-temperature NMR behavior of the hetero-halide dimers Cp'4(?-X)(?-Y), where Cp' is Cp double-prime or Cpdouble-dagger and X and Y are halides where X ? Y, was examined. Above room temperature, the halide atoms exchange sites rapidly on the NMR time scale

  6. Room-Temperature Magneto-Optical Phenomena in Organo-Metal Halide Perovskites.

    Science.gov (United States)

    Wu, Ting; Hsiao, Yu-Che; Li, Mingxing; Kang, Nam-Goo; Mays, Jimmy; Hu, Bin

    2015-03-01

    Organo-metal halide perovskites have become extremely interesting light-emitting, photovoltaic and lasing materials. The first magneto-optical phenomena, namely magneto-absorption effects, were reported in 1994 for very low temperature and high field (20 Tesla). Here, we report room-temperature magneto-optical phenomena at low field (<200 mT) from such perovskites. We find that room-temperature magneto-optical effects require high excitation intensity. At high excitation intensities we can observe magnetic field effects on photoluminescence, photocurrent, and electroluminescence. The magneto-optical phenomena indicate that both light-emitting and photovoltaic responses undergo a spin-dependent process. Furthermore, at low excitation intensities organo-metal halide perovskites exhibit negligible magnetic field effects. Therefore, we can conclude that the magneto-optical phenomena are from spin-dependent charge recombination in light-emitting and photovoltaic processes. This presents a new mechanism to control the light-emitting and photovoltaic functions in organo-metal halide perovskites by using spins. This presentation will discuss the key parameters in controlling magneto-optical phenomena in organo-metal halide perovskites.

  7. 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

  8. New chemical cross-coupling between aryl halides and allylic acetates using a cobalt catalyst.

    Science.gov (United States)

    Gomes, Paulo; Gosmini, Corinne; Périchon, Jacques

    2003-04-01

    [reaction: see text] The cobalt-catalyzed coupling reaction of aromatic halides and allylic acetates proceeds readily under mild conditions in the presence of the appropriate reducing agent to produce allylaromatic derivatives either in pure acetonitrile (aryl bromides) or in an acetonitrile/pyridine mixture (aryl chlorides). PMID:12659569

  9. New efficient preparation of arylzinc compounds from aryl halides using cobalt catalysis and sacrificial anode process

    Science.gov (United States)

    Gosmini; Rollin; Nedelec; Perichon

    2000-09-22

    Electroreduction of aryl-chlorides or -bromides in an electrochemical cell fitted with a sacrificial zinc anode and in the presence of cobalt halide associated with pyridine as ligand in DMF or acetonitrile as solvent affords the corresponding organozinc species in good yields. PMID:10987936

  10. Homocoupling of benzyl halides catalyzed by POCOP-nickel pincer complexes

    KAUST Repository

    Chen, Tao

    2012-08-01

    Two types of POCOP-nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX 2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields. © 2012 Elsevier Ltd. All rights reserved.

  11. Holographic collimator of diameter 200 mm in silver halide sensitized gelatin

    OpenAIRE

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

    1990-01-01

    In this paper we present the theoretical analysis and experimental results of a holographic collimator made in silver halide sensitized gelatin. Diffraction efficiency up to 70% over the whole plate and wave aberration as low as 20-lambda in the maximum diffraction efficiency geometry of reconstruction are its main properties as a holographic optical element.

  12. Ionic liquids as solvent for efficient esterification of carboxylic acids with alkyl halides

    OpenAIRE

    carboxylic, Ionic liquids as solvent for efficient e

    2010-01-01

    The selective esterification of carboxylic acid derivatives with a variety of alkyl halides was carried out using ionic liquid as solvent in the presence of triethylamine. The reaction was found to proceed under relatively mild conditions with excellent conversions (up to 99%) and selectivities. The ionic liquid was recycled and reused.

  13. Halocyclization of Unsaturated Guanidines Mediated by Koser's Reagent and Lithium Halides.

    Science.gov (United States)

    Daniel, Marion; Blanchard, Florent; Nocquet-Thibault, Sophie; Cariou, Kevin; Dodd, Robert H

    2015-11-01

    The synthesis of halogenated cyclic guanidines through iodine(III)-mediated umpolung of halide salts is described. Cyclic guanidines of various sizes can be obtained with generally excellent regioselectivities through either a chloro- or a bromocyclization, using Koser's reagent and the corresponding lithium salt. PMID:26492553

  14. 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

  15. Bi(OTf)3-Catalyzed 5-Exo-Trig Cyclization via Halide Activation

    OpenAIRE

    Hayashi, Ryuji; Cook, Gregory R.

    2008-01-01

    Lewis acid activation of allyl halides utilizing Bi(OTf)3 resulted in cationic cyclization of alkenes with high efficiency. While other Lewis acids could catalyzed this process with highly substituted alkenes, bismuth salts demonstrated unique reactivity in come cases. This suggested that bismuth triflate possesses intersting halophilic properties.

  16. Magnetic Silica Supported Copper: A Modular Approach to Aqueous Ullmann-type Amination of Aryl Halides

    Science.gov (United States)

    One-pot synthesis of magnetic silica supported copper catalyst has been described via in situ generated magnetic silica (Fe3O4@SiO2); the catalyst can be used for the efficacious amination of aryl halides in aqueous medium under microwave irradiation.

  17. 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.

  18. 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; Kepp, Kasper Planeta

    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,...

  19. Standard enthalpies of solution of alkali metal halides in water, dimethylformamide, and isopropanol at 303.6 and 313.15 K

    International Nuclear Information System (INIS)

    Standard enthalpies of solution are determined on the basis of earlier measured values of enthalpies of solution of sodium, potassium and cesium iodides in water, dimethylformamide and isopropanol at 303.6 and 313.15 K as well as thermodynamic characteristics of ionic association in the above mentioned liquid systems are determined. Temperature coefficients of enthalpies of solution are calculated and discussed

  20. Muon implantation in alkali metal hydrides

    International Nuclear Information System (INIS)

    Zero, longitudinal and transverse field ?SR measurements have been made on LiH, LiD and NaH. The primary motivation for the study was to elucidate the behaviour of the muons in the diamagnetic state and analysis of the time-dependent zero field relaxation data suggests that negatively charged muonium, Mu-, is formed and takes up a H- vacancy site in these materials. Evidence is presented for a small (approximately 2%) reduction in the Mu-Li distance relative to the unperturbed nearest neighbour anion-cation distances in the pure crystal lattices

  1. Milk alkali syndrome—an unusual syndrome causing an unusual complication

    OpenAIRE

    George, S.; Clark, J

    2000-01-01

    Milk alkali syndrome is rare and although pancreatitis secondary to hypercalcaemia is well recognised, there has only been one other reported case of pancreatitis secondary to the milk alkali syndrome. Such a case, caused by self medication of over the counter medication, is reported.???Keywords: milk alkali syndrome; pancreatitis; over the counter medication

  2. 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...

  3. About alkali metal dicyanamides. Syntheses, single-crystal structure determination, DSC/TG and vibrational spectra of KCs[N(CN){sub 2}]{sub 2} and NaRb{sub 2}[N(CN){sub 2}]{sub 3} . H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Reckeweg, Olaf [Cornell Univ., Ithaca, NY (United States). Baker Laboratory; Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie; Wakabayashi, Ryo H.; DiSalvo, Francis J. [Cornell Univ., Ithaca, NY (United States). Baker Laboratory; Schulz, Armin [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Schneck, Christof; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

    2015-07-01

    Transparent colorless crystals of KCs[N(CN){sub 2}]{sub 2} and NaRb{sub 2}[N(CN){sub 2}]{sub 3} . H{sub 2}O were obtained by blending aqueous solutions of Na[N(CN){sub 2}] and RbF or KF, respectively. After evaporation of the water, the remaining solid was extracted with absolute ethanol and the solvent was allowed to evaporate at r. t. KCs[N(CN){sub 2}]{sub 2} crystallizes in the space group C2/c (no. 15) with the cell parameters a = 1382.7(2), b = 998.1(1) and c = 1455.4(2) pm, and ? = 118.085(4) . The structure of NaRb{sub 2}[N(CN){sub 2}]{sub 3} . H{sub 2}O is exhibiting the P6{sub 3}/m (no. 176) with the cell parameters a = 705.98(7) and c = 1462.89(12) pm. Single-crystalline ?-K[N(CN){sub 2}] was obtained while attempting to synthesize 'NaK{sub 2}[N(CN){sub 2}]{sub 3}', corroborating the results of previous X-ray powder diffraction experiments. Vibrational spectra and DSC/TGA analyses complete our results.

  4. Halide peroxidase in tissues that interact with bacteria in the host squid Euprymna scolopes.

    Science.gov (United States)

    Small, A L; McFall-Ngai, M J

    1999-03-15

    An enzyme with similarities to myeloperoxidase, the antimicrobial halide peroxidase in mammalian neutrophils, occurs abundantly in the light organ tissue of Euprymna scolopes, a squid that maintains a beneficial association with the luminous bacterium Vibrio fischeri. Using three independent assays typically applied to the analysis of halide peroxidase enzymes, we directly compared the activity of the squid enzyme with that of human myeloperoxidase. One of these methods, the diethanolamine assay, confirmed that the squid peroxidase requires halide ions for its activity. The identification of a halide peroxidase in a cooperative bacterial association suggested that this type of enzyme can function not only to control pathogens, but also to modulate the interactions of host animals with their beneficial partners. To determine whether the squid peroxidase functions under both circumstances, we examined its distribution in a variety of host tissues, including those that typically interact with bacteria and those that do not. Tissues interacting with bacteria included those that have specific cooperative associations with bacteria (i.e., the light organ and accessory nidamental gland) and those that have transient nonspecific interactions with bacteria (i.e., the gills, which clear the cephalopod circulatory system of invading microorganisms). These bacteria-associated tissues were compared with the eye, digestive gland, white body, and ink-producing tissues, which do not typically interact directly with bacteria. Peroxidase enzyme assays, immunocytochemical localization, and DNA-RNA hybridizations showed that the halide-dependent peroxidase is consistently expressed in high concentration in tissues that interact bacteria. Elevated levels of the peroxidase were also found in the ink-producing tissues, which are known to have enzymatic pathways associated with antimicrobial activity. Taken together, these data suggest that the host uses a common biochemical response to the variety of types of associations that it forms with microorganisms. PMID:10022605

  5. Correlation of crystal quality and extreme magnetoresistance of WTe2

    Science.gov (United States)

    Ali, Mazhar N.; Schoop, Leslie; Xiong, Jun; Flynn, Steven; Gibson, Quinn; Hirschberger, Max; Ong, N. P.; Cava, R. J.

    2015-06-01

    High-quality single crystals of WTe2 were grown using a Te flux followed by a cleaning step involving self-vapor transport. The method is reproducible and yields consistently higher-quality single crystals than are typically obtained via halide-assisted vapor transport methods. Magnetoresistance (MR) values at 9 tesla and 2 kelvin as high as 1.75 million %, nearly an order of magnitude higher than previously reported for this material, were obtained on crystals with residual resistivity ratio (RRR) of approximately 1250. The MR follows a near B 2 law (B = 1.95(1)) and, assuming a semiclassical model, the average carrier mobility for the highest-quality crystal was found to be 167,000 \\text{cm}^2/\\text{Vs} at 2 K. A correlation of RRR, MR ratio and average carrier mobility (?\\textit{avg}) is found with the cooling rate during the flux growth.

  6. Trapped electrons in ice crystal

    International Nuclear Information System (INIS)

    Optical absorption in ice crystals was studied. The temperature dependence of the parameters of optical absorption of trapped electrons in ice crystal are shown in figures. The value of lambda max approaches to a constant value below -500C. Variation of the G value is large in the temperature range between 00C and -500C, and small at lower temperature. The temperature dependence of half-width is almost same as that of the G value. The characteristic region peculiar to solid may be below -500C. The spectrum of optical absorption by ice crystlas was compared with that of alkali ice, and the former was narrower than the latter. The ice crystals used for the experiment were made by gradual growth in a bath, irradiated in liquid nitrogen, and measured at this temperature. The ice crystals made from water containing various solutes were studied. Increase of trapped electrons after irradiation was seen only in cases that the solutes were KF and NH4F. The increase may be caused by F-. The absorption peak in case of alkali ice was seen at 6600 A, and shifted to the side of shorter wave length in comparison with the absorption in pure water. This is due to the effect of solute ions. On the other hand, the reason of the increase of trapped electrons due to the presence of F- is still not known. Overall fading of color due to irradiation was seen. Differential spectra, infra-red absorption spectra and dose dependence were investigated. (Kato, T.)

  7. Possible applications of alkali-activated systems in construction.

    Czech Academy of Sciences Publication Activity Database

    Bohá?ová, J.; Stan?k, S.; Vavro, Martin

    2013-01-01

    Ro?. 12, ?. 2 (2013), s. 8-17. ISSN 1804-4824 Institutional support: RVO:68145535 Keywords : alkali-activated system * geopolymer * binder Subject RIV: JN - Civil Engineering http://www.degruyter.com/view/j/tvsb.2012.12.issue-2/v10160-012-0012-8/v10160-012-0012-8.xml?format=INT

  8. Possible applications of alkali-aktivated systems in construction.

    Czech Academy of Sciences Publication Activity Database

    Bohá?ová, J.; Stan?k, S.; Vavro, Martin

    2012-01-01

    Ro?. 12, ?. 2 (2012), s. 8-17. ISSN 1804-4824 Institutional support: RVO:68145535 Keywords : alkali-activated system * geopolymer * binder Subject RIV: JN - Civil Engineering http://www.degruyter.com/view/j/tvsb.2012.12.issue-2/v10160-012-0012-8/v10160-012-0012-8.xml?format=INT

  9. Vanadium pentoxide base catalysts with additions of alkali mettal oxides

    International Nuclear Information System (INIS)

    Activity of catalysts on the basis of vanadium pentoxide with additions of alkali metal oxides in electrochemical reaction of H2O2 decomposition has been considered. Using the methods of electric conductivity, X-ray phase analysis, IR-spectroscopy the phase composition of the catalysts studied and their structure are determined. A connection between the catalyst activity and structure is shown

  10. Chlor-Alkali Industry: A Laboratory Scale Approach

    Science.gov (United States)

    Sanchez-Sanchez, C. M.; Exposito, E.; Frias-Ferrer, A.; Gonzalez-Garaia, J.; Monthiel, V.; Aldaz, A.

    2004-01-01

    A laboratory experiment for students in the last year of degree program in chemical engineering, chemistry, or industrial chemistry is presented. It models the chlor-alkali process, one of the most important industrial applications of electrochemical technology and the second largest industrial consumer of electricity after aluminium industry.

  11. Stabilized Alkali-Metal Ultraviolet-Band-Pass Filters

    Science.gov (United States)

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

    1995-01-01

    Layers of bismuth 5 to 10 angstrom thick incorporated into alkali-metal ultraviolet-band-pass optical filters by use of advanced fabrication techniques. In new filters layer of bismuth helps to reduce surface migration of sodium. Sodium layer made more stable and decreased tendency to form pinholes by migration.

  12. Assesment of Alkali Resistance of Basalt Used as Concrete Aggregates

    Directory of Open Access Journals (Sweden)

    al-Swaidani Aref M.

    2015-11-01

    Full Text Available The objective of this paper is to report a part of an ongoing research on the influence of using crushed basalt as aggregates on one of durability-related properties of concrete (i.e. alkali-silica reaction which is the most common form of Alkali-Aggregate Reaction. Alkali resistance has been assessed through several methods specified in the American Standards. Results of petrographic examination, chemical test (ASTM C289 and accelerated mortar bar test (ASTM C1260 have particularly been reported. In addition, the weight change and compressive strength of 28 days cured concrete containing basaltic aggregates were also reported after 90 days of exposure to 10% NaOH solution. Dolomite aggregate were used in the latter test for comparison. The experimental results revealed that basaltic rocks quarried from As-Swaida’a region were suitable for production of aggregates for concrete. According to the test results, the studied basalt aggregates can be classified as innocuous with regard to alkali-silica reaction. Further, the 10% sodium hydroxide attack did not affect the compressive strength of concrete.

  13. 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 ...

  14. 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.

  15. The ultraviolet photodissociation dynamics of the hydrogen halides

    International Nuclear Information System (INIS)

    The first electronic absorption bands of hydrogen halide (HX) molecules - HI, HBr, HCl and DCl - have been studied using two experimental, laser-based techniques. Each band of HX consists of absorption of ultraviolet (UV) radiation and leads to fragmentation into two sets of products: H(2S) + X(2Pj); j=3/2, 1/2. Numerous measurements that cover most of the UV absorption bands (??200-300 nm) of HI and HBr were made using H Rydberg atom photofragment translational spectroscopy (HRPTS). The results comprise two important properties: the branching between the accessible product channels and the spatial distributions of the recoil velocities of the photofragments. These extensive observations afford a detailed interpretation of the featureless absorption bands in terms of the relative influences of transitions and dissociations involving multiple electronic states: 3?(1), 3?(0+), 1?(1) and 3?+(1). The photolysis of HCl between 201 and 210 nm was also studied by HRPTS to provide a number of direct determinations of the relative product yield for comparison with the best available theoretical predictions based on ab initio electronic structure calculations and a time-independent treatment of the photodissociation dynamics. The good agreement between the calculations and observations provided encouraging support for the theoretical description. The second experimental method combined resonance enhanced multiphoton ionization (REMPI) and a time-of-flight mass spectrometer (TOF MS) to quantify the relative production of die spin-orbit components of the halogen photoproducts from HI, DCl and vibrationally-excited HCl. Relating the observed REMPI yields for each quantum state to the nascent populations required a scaling factor to account for the different ionization probabilities. This was derived for the ground state of the chlorine atom by comparing the Cl(2Pj) REMPI signal recorded following photolysis of HCl at ?=205.5 nm with a direct determination obtained by HRPTS. The calibration factor was subsequently used to convert chlorine REMPI yields into the relative branching between Cl(2Pj) atoms in two studies. The first set of experiments photodissociated DCl molecules at 5 wavelengths between 200 and 220 nm and the results showed reasonable agreement with the calculations employing the aforementioned time-independent theory. The second study used infrared absorption to create HCl molecules in selected rotational states of vibrational levels v=1-3 prior to photolysis. These results were compared against values generated by time-dependent wave propagation using the existing ab initio data and highlighted some inadequacies of the theory. The REMPI-TOF MS technique was further applied to detect the iodine atoms from the photolysis of HI. The results confirmed a slight partiality to the HRPTS results that had been previously considered in a Monte Carlo simulation of the HRPTS experiment. Guided by the I-atom REMPI observations, the effect of the detection bias was successfully accounted for and the former determinations corrected. (author)

  16. Molten lanthanide halide systems: experimental, modeling and thermodynamic computation

    International Nuclear Information System (INIS)

    Molten lanthanide halide based systems were studied using two approaches: experiments and calculations. Liquid mixing enthalpies of chloride europium systems (MCl-EuCl2; M = Na, K, Rb) were measured at 1138 K. They can be represented (in kJ.mol-1) as a function of the molar fraction of EuCl2 (x) with the polynomials: ?mixHm0 (NaCl - EuCl2) = x(1 - x)(-1.6634 - 5.4964x + 6.3324x2), ?mixHm0 (KCl - EuCl2 = x(1 - x)(-21.262 + 17.196x- 6.6293x2), ?mixHm0 (RbCl - EuCl2 = x(1 - x)(-25.286 + 15.786x). The NaCl-EuCl2 phase diagram was experimentally determined. It exhibits an eutectic equilibrium (x(EuCl2) = 0.49; Teut = 847 ± 2 K). Temperatures and enthalpies effusion and transition of EuCl2 were also measured (Ttrs= 1014 ± 2 K, ?trsHm0 = 11.5 ± 0.7 kJ.mol1, TfUs = 1125 ± 2 K, ?fusHm0 = 18.7 ± 1,1 kJ.mol-1) as well as heat capacities (Cpm0(EuCl2, ortho.) = 76.26 + 8.08 x 10-3 T between 310

  17. Properties of beryl single crystals grown by a high pressure hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Furusaki, T.; Bando, Y.; Kodaira, K. (Dept. of Applied Chemistry, Faculty of Engineering, Hokkaido Univ., Sapporo, 060 (JP)); Matsushita, T. (Dept. of Electrical Engineering, Kumamoto Institute of Technology, Kumamoto, 860 (JP))

    1989-08-01

    The authors discuss beryl crystals grown under high pressure hydrothermal condition of 1 GPa. The optimum crystal growth was observed at 600{sup 0}C and from 0.1N NaOH solution. The beryl crystals from 0.1 - 0.3N NaOH solutions incorporated water molecules and alkali cations in the channels of the beryl structure. The crystals showed same refractive indices and density as those of natural emerald crystals. These physical properties were very similar to natural emeralds.

  18. An alkali-free barium borosilicate viscous sealing glass for solid oxide fuel cells

    Science.gov (United States)

    Hsu, Jen-Hsien; Kim, Cheol-Woon; Brow, Richard K.; Szabo, Joe; Crouch, Ray; Baird, Rob

    2014-12-01

    An alkali-free, alkaline earth borosilicate glass (designated G102) has been developed as a viscous sealant for use with solid oxide fuel cells (SOFCs). The glass possesses the requisite viscosity, electrical resistivity, and thermal and chemical stability under SOFC operating conditions to act as a reliable sealant. Sandwich seals between aluminized stainless steel and a YSZ/NiO-YSZ bilayer survived 148 thermal cycles (800 °C to room temperature) in both oxidizing and reducing atmospheres at a differential pressure of ˜3.4 kPa (0.5 psi) without failure. For sandwich seals that were held at 800 °C for up to 2280 h in air, G102 resisted crystallization, there were limited interactions at the G102/YSZ interface, but BaAl2Si2O8 crystals formed at the glass/metal interface because of the reaction between the glass and the aluminized steel. Sandwich seals that were intentionally cracked by thermal shock resealed to became hermetic upon reheating to temperatures as low as 744 °C.

  19. Determination of membrane hydration numbers of alkali metal ions by insertion in a conducting polymer

    DEFF Research Database (Denmark)

    Skaarup, Steen; Junaid Mohamed Jafeen, Mohamed

    2010-01-01

    In aqueous solutions, the alkali metals ions, Li+, Na+, K+, Rb+ and Cs+ are known to be associated with a number of H2O molecules. Traditionally, 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. Although the solvation of alkali metal ions in aqueous solution has been discussed for many years, there is still no clear consensus. Part of the discrepancy is simply that different methods measure over different time scales, and therefore do not necessarily define the same hydration shell. This work presents a systematic study of one special variant of the hydrationnumbers 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 can then be calculated as a difference. The values determined this way may be called membrane hydration numbers. The results yield the following membrane hydration numbers: Li+: 5.3-5.5; Na+ 4.3-4.5; K+: 2.0-2.2; Rb+: 0.8-0.9; Cs+: similar to 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.

  20. Lanthanide containing ionic liquid crystals: EuBr2, SmBr3, TbBr3 and DyBr3 in C12mimBr

    OpenAIRE

    Mudring, Anja-Verena

    2010-01-01

    Abstract Doping the ionic liquid crystal C12mimBr with various lanthanide halides yields interesting novel liquid crystalline and luminescent materials. The thermal phase behavior of all compounds was investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry and the photophysical properties were determined by luminescence spectroscopy. C12mimBr itself is an ionic liquid crystal that shows bluish-white emission upon excitation with UV-light due ...